Operator's Manual Model SMX2040 Model SMX2042 Model SMX2044

Operator's Manual Model SMX2040 Model SMX2042 Model SMX2044

Operator's Manual

Model SMX2040 6½ Digit Digital Multimeter

Model SMX2042 6½ Digit Multi-Function Digital Multimeter

Model SMX2044 6½ Digit LCR Sourcing Digital Multimeter

Corporation

December, 2004

CAUTION

In no event shall Signametrics or its Representatives be liable for any consequential damages whatsoever (including, without limitation, damages for loss of business profits, business interruption, loss of business information, or other loss) arising out of the use of or inability to use Signametric's products, even if Signametrics has been advised of the possibility of such damages. Because some states do not allow the exclusion or limitation of liability for consequential damages, the above limitations may not apply to you.

© 1999 Signametrics Corp. Printed in the USA. All rights reserved. Contents of this publication must not be reproduced in any form without the permission of Signametrics Corporation.

Signametrics 2

TABLE OF CONTENTS

1.0 INTRODUCTION .................................................................................................................................................7

1.1

S

AFETY

C

ONSIDERATIONS

..........................................................................................................................7

1.2

M

INIMUM

R

EQUIREMENTS

.........................................................................................................................8

1.3

F

EATURE

S

ET

.............................................................................................................................................8

2.0 SPECIFICATIONS ...............................................................................................................................................9

2.1

DC V

OLTAGE

M

EASUREMENT

...................................................................................................................9

2.2

DC C

URRENT

M

EASUREMENT

....................................................................................................................9

2.3

AC V

OLTAGE

M

EASUREMENTS

..................................................................................................................9

2.3.1 AC Voltage True RMS Measurement .......................................................................................9

2.3.2 AC Peak-to-Peak Measurement (SMX2044)..........................................................................10

2.3.3 AC Crest Factor Measurement (SMX2044)...........................................................................10

2.3.4 AC Median Value Measurement (SMX2044).........................................................................11

2.4

AC C

URRENT

M

EASUREMENT

, T

RUE

RMS ..............................................................................................11

2.5

R

ESISTANCE

M

EASUREMENTS

..................................................................................................................12

2.5.1 2-wire and 4-wire...................................................................................................................12

2.5.2 6-wire Guarded Resistance Measurement (SMX2044)..........................................................12

2.6

L

EAKAGE

M

EASUREMENT

(SMX2044)....................................................................................................12

2.7

RTD T

EMPERATURE

M

EASUREMENT

(SMX2044) ...................................................................................12

2.8

A

DDITIONAL

C

OMPONENT

M

EASUREMENTS

............................................................................................13

2.8.1 Diode Characterization .........................................................................................................13

2.8.2 Capacitance Measurement (SMX2042, 44) ...........................................................................13

2.8.3 Inductance Measurement (SMX2044)....................................................................................13

2.8.4 In Circuit AC-Based Capacitance Measurements (SM2044) ................................................13

2.9

T

IMING

M

EASUREMENTS

(SMX2042, 44)................................................................................................14

2.9.1 Threshold DAC ......................................................................................................................14

2.9.2 Frequency and Period Measurement.....................................................................................14

2.9.3 Duty Cycle Measurement .......................................................................................................14

2.9.4 Pulse Width ............................................................................................................................14

2.9.5 Totalizer .................................................................................................................................15

2.10

T

RIGGER

F

UNCTIONS

..............................................................................................................................15

2.10.1 External Hardware Trigger (at DIN-7 connector) ..............................................................15

2.10.2 PXI Bus Hardware Trigger Inputs (at PXI J2) ....................................................................15

2.10.3 PXI Bus Hardware Trigger Output (to PXI J2) ...................................................................15

2.10.4 Analog Threshold Trigger....................................................................................................15

2.11

S

OURCE

F

UNCTIONS

(SMX2044)...........................................................................................................16

2.11.1 DC Voltage Source ..............................................................................................................16

2.11.2 AC Voltage Source...............................................................................................................16

2.11.3 DC Current Source ..............................................................................................................16

2.12

A

CCURACY

N

OTES

.................................................................................................................................17

2.13

O

THER

S

PECIFICATIONS

.........................................................................................................................18

3.0 GETTING STARTED.........................................................................................................................................19

3.1

S

ETTING THE

DMM..................................................................................................................................19

3.2

I

NSTALLING THE

DMM M

ODULE

.............................................................................................................19

3.3

I

NSTALLING THE

DMM

SOFTWARE PACKAGE

...........................................................................................19

3.4

DMM I

NPUT

C

ONNECTORS

......................................................................................................................19

3.5

S

TARTING THE

C

ONTROL

P

ANEL

..............................................................................................................21

3.6

U

SING THE

C

ONTROL

P

ANEL

....................................................................................................................22

4.0 DMM OPERATIONS AND MEASUREMENTS.............................................................................................24

4.1

V

OLTAGE

M

EASUREMENT

........................................................................................................................24

4.1.1 DC Voltage Measurements ....................................................................................................24

4.1.2 True RMS AC Voltage Measurements ...................................................................................25

3 Signametrics

4.1.3 AC Peak-to-Peak and Crest Factor Measurement (SMX2044) .............................................25

4.1.4 AC Median Value Measurement (SMX2044).........................................................................26

4.2

C

URRENT

M

EASUREMENTS

......................................................................................................................26

4.2.1 Improving Current Measurements .........................................................................................26

4.2.2 Low Level DC Current Measurements...................................................................................27

4.2.3 Extended DC Current Measurements (SM2044) ...................................................................27

4.3

R

ESISTANCE

M

EASUREMENTS

..................................................................................................................27

4.3.1 2-wire Ohm Measurements ....................................................................................................27

4.3.2 4-wire Ohm Measurements ....................................................................................................27

4.3.3 Using Offset Ohms function ...................................................................................................28

4.3.4 6-wire Guarded Resistance Measurement (SMX2044)..........................................................28

4.3.5 Leakage Measurements (SMX2044) ......................................................................................29

4.3.6 Extended Resistance Measurements (SMX2044) ...................................................................30

4.3.7 Effects of Thermo-Voltaic Offset............................................................................................31

4.3.8 Guarding High Value Resistance Measurements (SMX2044) ...............................................32

4.4

RTD T

EMPERATURE

M

EASUREMENT

(SMX2044) ...................................................................................32

4.5

I

NTERNAL

T

EMPERATURE

(SMX2044) ....................................................................................................32

4.6

D

IODE

C

HARACTERIZATION

.....................................................................................................................33

4.7

C

APACITANCE

M

EASUREMENT

(SMX2044).............................................................................................33

4.8

I

N

-C

IRCUIT

C

APACITANCE

M

EASUREMENT

(SMX2044)..........................................................................34

4.9

I

NDUCTANCE

M

EASUREMENT

(SMX2044) ..............................................................................................34

4.10

C

HARACTERISTIC

I

MPEDANCE

M

EASUREMENT

(SMX2044) ..................................................................34

4.11

T

RIGGER

O

PERATION

.............................................................................................................................34

4.11.1 External Hardware Trigger .................................................................................................34

4.11.2 Analog Threshold Trigger....................................................................................................35

4.11.3 Software Issued Triggered Operations ................................................................................35

4.11.4 Using the PXI bus Trigger Facilities ...................................................................................35

4.12

F

REQUENCY AND

T

IMING

M

EASUREMENTS

(SMX2042, 44) ..................................................................36

4.12.1 Threshold DAC ....................................................................................................................36

4.12.2 Frequency and Period Measurements .................................................................................37

4.12.3 Duty Cycle Measurement .....................................................................................................38

4.12.4 Pulse Width ..........................................................................................................................38

4.12.5 Totalizer Event Counter .......................................................................................................38

4.13

S

OURCING

F

UNCTIONS

(SMX2044) .......................................................................................................39

4.13.1 DC Voltage Source ..............................................................................................................39

4.13.2 AC Voltage Source...............................................................................................................40

4.13.3 DC Current Source ..............................................................................................................40

4.13.4 Source Current - Measure Voltage ......................................................................................40

4.14

S

YNTHESIZING

R

ESISTANCE

(SMX2044) ...............................................................................................41

4.15

I

NTERFACING TO THE

SMX4032

SERIES

R

ELAY

S

CANNERS

...................................................................42

4.15.1 Triggering the SMX2040 DMMs .........................................................................................42

4.15.2 Multiplexing with the SMX2040 DMMs...............................................................................43

4.15.3 Interface Commands and Timing.........................................................................................43

5.1

D

ISTRIBUTION

F

ILES

................................................................................................................................45

5.1.1 The SM40CAL.DAT file ........................................................................................................46

5.2

U

SING THE

SMX2040 D

RIVER

W

ITH

C++

OR

S

IMILAR

S

OFTWARE

..........................................................47

Multiple Card Operations Under Windows ....................................................................................47

5.3

V

ISUAL

B

ASIC

F

RONT

P

ANEL

A

PPLICATION

.............................................................................................48

5.3.1 Visual Basic Simple Application ............................................................................................49

5.4

W

INDOWS

DLL D

EFAULT

M

ODES AND

P

ARAMETERS

..............................................................................49

5.5

U

SING THE

SMX2040 DLL

WITH

L

AB

W

INDOWS

/CVI

®.........................................................................50

5.6

W

INDOWS

C

OMMAND

L

ANGUAGE

...........................................................................................................51

DMMArmAnalogTrigger ................................................................................................................51

DMMArmTrigger............................................................................................................................52

DMMBurstBuffRead .......................................................................................................................53

DMMBurstRead ..............................................................................................................................54

DMMCalibrate................................................................................................................................55

DMMCleanRelay ............................................................................................................................55

DMMClearMinMax ........................................................................................................................56

DMMClosePCI ...............................................................................................................................56

Signametrics 4

DMMDelay .....................................................................................................................................57

DMMDisableTrimDAC...................................................................................................................57

DMMDisArmTrigger ......................................................................................................................58

DMMDutyCycleStr .........................................................................................................................58

DMMErrString................................................................................................................................59

DMMFrequencyStr .........................................................................................................................59

DMMGetACCapsR .........................................................................................................................61

DMMGetBusInfo.............................................................................................................................61

DMMGetCalDate............................................................................................................................62

DMMGetdB.....................................................................................................................................62

DMMGetdBStr ................................................................................................................................63

DMMGetCJTemp ............................................................................................................................63

DMMGetDeviation .........................................................................................................................64

DMMGetDeviatStr ..........................................................................................................................65

DMMGetFuncRange.......................................................................................................................65

DMMGetFunction...........................................................................................................................66

DMMGetGrdVer .............................................................................................................................66

DMMGetHwVer ..............................................................................................................................67

DMMGetID .....................................................................................................................................67

DMMGetManDate ..........................................................................................................................68

DMMGetMax ..................................................................................................................................68

DMMGetMaxStr .............................................................................................................................69

DMMGetMin...................................................................................................................................69

DMMGetMinStr ..............................................................................................................................70

DMMGetRange ...............................................................................................................................70

DMMGetRate..................................................................................................................................71

DMMGetSourceFreq ......................................................................................................................71

DMMGetTCType.............................................................................................................................72

DMMGetType .................................................................................................................................72

DMMGetVer ...................................................................................................................................73

DMMInit .........................................................................................................................................73

DMMIsAutoRange ..........................................................................................................................74

DMMIsInitialized ............................................................................................................................75

DMMIsRelative ...............................................................................................................................75

DMMLoadCalFile...........................................................................................................................76

DMMOpenPCI................................................................................................................................77

DMMOpenCalACCaps ...................................................................................................................77

DMMOpenTerminalCal ..................................................................................................................78

DMMPeriodStr ...............................................................................................................................78

DMMPolledRead ............................................................................................................................80

DMMPolledReadCmd.....................................................................................................................80

DMMPolledReadStr........................................................................................................................81

DMMRead.......................................................................................................................................81

DMMReadBuffer.............................................................................................................................82

DMMReadBufferStr ........................................................................................................................83

DMMReadCJTemp .........................................................................................................................83

DMMReadCrestFactor ...................................................................................................................84

DMMReadDutyCycle ......................................................................................................................85

DMMReadFrequency......................................................................................................................85

DMMReadFrequencyStr .................................................................................................................86

DMMReadInductorQ ......................................................................................................................87

DMMReadMeasurement .................................................................................................................87

DMMReadMedian...........................................................................................................................88

DMMReadNorm..............................................................................................................................88

DMMReadPeakToPeak...................................................................................................................89

DMMReadPeriod............................................................................................................................89

DMMReadStr ..................................................................................................................................90

DMMReadTotalizer ........................................................................................................................91

DMMReadWidth .............................................................................................................................92

DMMReady .....................................................................................................................................92

5 Signametrics

DMMSetACCapsDelay ...................................................................................................................93

DMMSetACCapsLevel ....................................................................................................................93

DMMSetACVSource .......................................................................................................................94

DMMSetAutoRange ........................................................................................................................95

DMMSetBuffTrigRead ....................................................................................................................95

DMMSetCapsAveSamp ...................................................................................................................96

DMMSetCJTemp.............................................................................................................................97

DMMSetCompThreshold ................................................................................................................98

DMMSetCounterRng.......................................................................................................................98

DMMSetDCISource ........................................................................................................................99

DMMSetDCVSource .......................................................................................................................99

DMMSetExternalShunt .................................................................................................................100

DMMSetFuncRange......................................................................................................................101

DMMSetFunction..........................................................................................................................101

DMMSetInductFreq ......................................................................................................................102

DMMSetOffsetOhms .....................................................................................................................102

DMMSetRange..............................................................................................................................103

DMMSetRate.................................................................................................................................103

DMMSetRelative ...........................................................................................................................104

DMMSetResistance .......................................................................................................................106

DMMSetRTD ................................................................................................................................106

DMMSetSensoreParams ...............................................................................................................107

DMMSetSourceMode....................................................................................................................107

DMMSetSynchronized...................................................................................................................108

DMMSetTCType ...........................................................................................................................109

DMMSetTempUnits.......................................................................................................................109

DMMSetTrigRead .........................................................................................................................110

DMMSetTrimDAC ........................................................................................................................111

DMMStartTotalizer.......................................................................................................................111

DMMStopTotalizer .......................................................................................................................113

DMMTerminate.............................................................................................................................113

DMMTrigger.................................................................................................................................114

DMMWidthStr...............................................................................................................................114

SetACCapsFreq.............................................................................................................................115

6.0 MAINTENANCE ..............................................................................................................................................116

6.1

P

ERFORMANCE

T

ESTS

............................................................................................................................117

6.2

DC V

OLTAGE

T

EST

................................................................................................................................117

6.3

R

ESISTANCE

T

EST

, 2-

WIRE

.....................................................................................................................118

6.4

R

ESISTANCE

T

EST

, 4-

WIRE

.....................................................................................................................118

6.5

AC V

OLTAGE

T

EST

................................................................................................................................120

6.6

DC C

URRENT

T

EST

................................................................................................................................121

6.7

AC C

URRENT

T

EST

................................................................................................................................121

6.8

C

APACITANCE

T

EST

(SMX2044

ONLY

)..................................................................................................122

6.9

F

REQUENCY

C

OUNTER

T

EST

(SMX2044

ONLY

).....................................................................................123

6.10

C

ALIBRATION

.......................................................................................................................................124

7.0 WARRANTY AND SERVICE.........................................................................................................................125

8.0 ACCESSORIES.................................................................................................................................................125

Signametrics 6

1.0 Introduction

Congratulations! You have purchased a PXI/CompactPCI Plug-in instrument with analog and systems performance that rivals the best, all-in-one box instruments. The SMX2040 series digital multimeters (DMMs) are easy to setup and use, have sophisticated analog and digital circuitry to provide very repeatable measurements, and are protected to handle any unexpected situations your measurement environment may encounter. To get years of reliable service from these DMMs, please take a few moments and review this manual before installing and using this precision instrument.

This manual describes the SMX2040 and SMX2044 DMMs. Each DMM delivers unmatched breakthrough performance in a PXI and CompactPCI plug-in instrument. With a rich repertoire of functions, the SMX2040 series out performs all other plug-in DMMs, including the trusted Signametrics SM-2020CT, and most brand named bench top units.

Note: In this manual, all references to the "SMX2040" and “DMM” apply to the SMX2040 and SMX2044.

Features unique to the SMX2044 will be identified as such.

1.1 Safety Considerations

Safety Considerations

The SMX2040 series of DMMs is capable of measuring up to 300 VDC or 250 VAC across the Volt HI and LO terminals, and can also measure common mode signals that "float" the DMM above EARTH ground by up to 300 VDC or 250 VAC. When making common mode measurements, the majority of the circuits inside the DMM are at the common mode voltage. These voltages can be lethal and can KILL!

During and after installing your DMM, check to see that there are no wires or ribbon cables from your PXI/CompactPCI chassis trapped inside the DMM.

The DMM comes installed with two shields (bottom and top) that must not be removed for performance

as well as safety reasons. Removal of these shields and/or improper assembly of the shields can result in lethal voltages occurring within your chassis. Also make sure the chassis is 3U in size.

Warning

Check to see that no loose wires or ribbon cables infringe upon any of the internal circuits of the

DMM, as this may apply measurement voltages to your computer, causing electrocution and/or

damage to your PXI/CompactPCI chassis !

To avoid shock hazard, install the DMM only into a 3U PXI and CompactPCI chassis that has its power connector connected to a power receptacle with an earth safety ground.

When making any measurements above 50 VDC or 40 VAC, only use Safety Test Leads. Examples of these are the Signametrics Basic Test Leads and Deluxe Test Leads, offered as an optional accessory with the Signametrics DMMs. Do not use these units in a 6U chassis as an electrocution hazard will be

present.

7 Signametrics

1.2 Minimum Requirements

The SMX2040 series of system DMMs are precision plug-in modules that are compatible with 3U PXI or

CompactPCI chassis. The processor type must be a Pentium or equivalent processor running MS Windows. The

DMM requires a single PXI or CompactPCI slot. A mouse must be installed when controlling the DMM from the

Windows Control Panel. The SMX2040 comes with a Windows' DLL, for operation with Windows' Version

95/98/Me/2000/XP and NT4.0.

1.3 Feature Set

The base unit, the SMX2040, has 6-1/2 digit performance and can be used as a general purpose DMM, giving very accurate and stable readings. The SMX2044 adds to the SMX2040 additional measurement functions not found in other DMMs such as inductance measurement and sourcing capabilities.

SMX2040, 42, 44 6½ Digit DMMs feature table:

DMM

SMX2044 LCR

Sourcing DMM

Multi-Function

DMM

√ √

DCV 4 ranges, >10 G

Ω & 10 MΩ input resistance.

ACV 4 ranges, 1 M

Ω input

2-Wire Ohms, six ranges 330

Ω to 33 MΩ

4-Wire Ohms, four ranges 330

Ω to 330 kΩ

Offset Ohms

DC current, four ranges 3.3 mA to 2.5 A

AC current, four ranges 3.3 mA to 2.5 A

Diode V/I characteristics at 100

ηA to 1mA

Auto range, Relative

Min/Max, dB and percent deviation functions

On board measurement buffer

Measurement rate: 0.2 to 1,000/sec

External and threshold trigger

Thermocouples

High Dynamic range; +3,300,000 counts

PXI Trigger In/Out

Capacitance, seven ranges, 10 nF to 10 mF

Temperature (five basic RTD types)

Frequency / Period measurement

Pulse width, pos./neg., & duty cycle

Totalizer/event counter

Variable threshold DAC; all timing measure.

Peak to Peak, Crest factor, Median

Internal DMM temperature sensor

Six wire Ohms (with force/sense)

Inductance, six ranges 33

µH to 3.3 H

DCV source 0 to +/-10.0 V

ACV source 0 to 20 V pk-pk, 2 Hz to 75 KHz

DC current source, 1 nA to 12.5 mA

Leakage measurement

Synthesized resistance source

Extended Resistance measurements

In Circuit Capacitance

plus 33

Ω,

330 M

plus 33

plus 10 mA

plus 33

Ω,

330 M

plus 33

Ω range

plus 10 mA

Signametrics 8

2.0 Specifications

2.1 DC Voltage Measurement

Input Characteristics

Input Resistance 330 mV & 3.3 V Ranges: >10 GΩ ,

Input Resistance 33 V & 330 V Ranges: 10.0 MΩ

Accuracy ± (% of reading + Volts) [1]

6 ½ Digits

Resolution 24 hours

23

°C ± 1°C

330 mV 330.0000 mV

100

ηV

3.3 V 3.300000 V

1

µV

33 V 33.00000 V

10

µV

330 V 330.0000 V

100

µV

0.003 + 4.5

0.002 + 10

0.003 + 250

µV

µV

µV

0.004 + 1 mV

90 Days

23

°C ± 5°C

One Year 23

°C

± 5°C

0.004 + 5.5

µV

0.007 + 8

µV

0.0025 + 12

µV

0.0045 + 17

µV

0.004 + 280

µV

0.007 + 330

µV

0.005 + 1.2 mV 0.008 + 1.5 mV

[1] With reading rate set to 10 readings per second (rps) or slower, and within one hour of DCV zero, using Relative control.

DCV Noise Rejection Normal Mode Rejection, at 50, 60, or 400 Hz ± 0.5%, is better than 95 dB for reading rates of 10 rps or lower. Common Mode Rejection (with 1 k

Ω lead imbalance) is better than 120 dB for these conditions.

2.2 DC Current Measurement

Input Characteristics

Burden Voltage < 350 mV for all ranges

Protected with 2.5A fuse ( 5x20mm, 250 V Fast)

Accuracy ± (% of reading + Amps) [1]

3.3 mA

33 mA

330 mA

2.5 A

5 ½ Digits

3.30000 mA

33.0000 mA

330.000 mA

2.50000 A

Resolution

10

ηA

100

ηA

1

µA

10

µA

24 hours

23

°C ± 5°C

90 Days

23

°C ± 5°C

0.052 + 200

ηA

0.07 + 350

ηA

0.04 + 1

µA

0.05 + 30

µA

0.55 + 50

µA

0.06 + 2

µA

0.055 + 40

µA

0.6 + 200

µA

One Year 23

°C

± 5°C

0.1 + 400

ηA

0.1 + 3

µA

0.075 + 60

µA

0.65 + 350

µA

[1] With reading rate set to 10 rps or slower, and within one hour of DCI zero, using Relative control.

2.3 AC Voltage Measurements

Input Characteristics

Input Resistance 1.0 MΩ, shunted by < 100 pF, all ranges

Crest Factor 3 at Full Scale, increasing to 7 at Lowest Specified Voltage

AC coupled Specified range: 10 Hz to 100 kHz

Typical Settling time < 0.5 sec to within 0.1% of final value

2.3.1 AC Voltage True RMS Measurement

Range

330 mV

3.3 V

33 V

250 V [2]

Full Scale 6 ½ Digits

330.0000 mV

3.300000 V

33.00000 V

250.0000 V

Lowest specified Voltage

5 mV [1]

10 mV

100 mV

1 V

Resolution

100

ηV

1

µV

10

µV

100

µV

[1] Between 5 mV and 10 mV, add 100

µV additional error to the accuracy table below. In many computer installations, if the DMM is not near a noisy board, usable voltage measurements of 1 mV can be obtained.

[2] Signal is limited to 8x10

6

Volt Hz Product. For example, the largest frequency input at 250 V is

32 kHz, or 8x10

6

Volt x Hz.

9 Signametrics

Accuracy ± (% of reading + Volts) [1]

Range

330 mV

3.3 V

33 V

250 V

Frequency

10 Hz - 20 Hz

20 Hz - 47 Hz

47 Hz - 10 kHz

10 kHz - 50 kHz

50 kHz - 100 kHz

10 Hz - 20 Hz

20 Hz - 47 Hz

47 Hz - 10 kHz

10 kHz - 50 kHz

50 kHz - 100 kHz

10 Hz - 20 Hz

20 Hz - 47 Hz

47 Hz - 10 kHz

10 kHz - 50 kHz

50 kHz - 100 kHz

10 Hz - 20 Hz

20 Hz - 47 Hz

47 Hz - 10 kHz

10 kHz - 50 kHz

50 kHz - 100 kHz

24 hours

23

°C ± 1°C

3.0 + 350

µV

0.92 + 150

µV

0.13 + 100

µV

0.55 + 160

µV

5.3 + 350

µV

3.0 + 2 mV

0.93 + 1.3 mV

0.05 + 1 mV

0.62 + 1.2 mV

5.1 + 1.5 mV

3.0 + 14 mV

0.93 + 12 mV

0.06 + 10 mV

0.31 + 18 mV

2.0 + 30 mV

3.0 + 140 mV

0.93 + 120 mV

0.04 + 100 mV

0.32 + 150 mV

2.5 + 200 mV

90 Days

23

°C ± 5°C

3.1 + 380

µV

0.93 + 170

µV

0.14 + 110

µV

0.6 + 200

µV

5.4 + 370

µV

3.1 + 2.2 mV

0.96 + 1.5 mV

0.055 + 1.1 mV

0.65 + 1.3 mV

5.2 + 1.7 mV

3.1 + 16 mV

0.96 + 14 mV

0.065 + 11 mV

0.33 + 21 mV

2.2 + 35 mV

3.1 + 160 mV

0.96 + 130 mV

0.045 + 110 mV

0.4 + 170 mV

2.8 + 240 mV

One Year

23

°C ± 5°C

3.2 + 430

µV

0.95 + 200

µV

0.15 + 120

µV

0.63 + 230

µV

5.6 + 400

µV

3.2 + 2.5 mV

1.0 + 1.7 mV

0.065 + 1.2 mV

0.70 + 1.5 mV

5.3 + 2 mV

3.3 + 20 mV

1.0 + 16 mV

0.073 + 13 mV

0.35 + 25 mV

2.4 + 40 mV

3.3 + 200 mV

1.0 + 150 mV

0.06 + 130 mV

0.45 + 200 mV

3.2 + 300 mV

ACV Noise Rejection Common Mode rejection, for 50 Hz or 60 Hz with 1 k

Ω imbalance in either lead, is better than 60 dB.

2.3.2 AC Peak-to-Peak Measurement (SMX2044)

• Measures the peak-to-peak value of a repetitive waveform

ACV

Range

330 mV

Lowest specified input voltage

(Vp-p)

0.1 V

Full Scale reading (Vp-p)

1.85 V

Resolution

1 mV

Typical Accuracy 23

°C ± 5°C

One Year [1]

1.5

±10 mV

3.3 V 1.0 V 18.5 V 10 mV 1.4 ±70 mV

33 V 10 V 185.0 V 100 mV 1.0 ±700 mV

250 V 100 V 850.0 V 1 V 1.0 ± 6 V

[1] Specified from 30Hz to 10 kHz. Input signal frequency of 30 Hz to 30 kHz.

2.3.3 AC Crest Factor Measurement (SMX2044)

Measures the crest factor (peak / RMS) of a repetitive waveform

ACV

Range

Lowest specified input voltage

(Vp-p)

Highest specified input voltages (Vp-p)

Resolution

Typical Accuracy 23

°C ± 5°C

One Year [1]

330 mV 0.1 V 1.8 V 0.01

2.2

±0.3

3.3 V 1.0 V 18 V 0.01 2.1 ±0.1

33 V 10 V 180 V 0.01 2.0 ±0.1

250 V 100 V 700 V 0.01 2.0 ±0.1

[1] Crest factor measurement requires signal frequency of 30 Hz to 30 kHz.

Signametrics 10

2.3.4 AC Median Value Measurement (SMX2044)

• Measures the mid-point between the positive and negative peaks of a repetitive waveform

• Used to determine the Threshold DAC setting for optimal frequency and timing measurements

ACV

Range

Lowest specified input voltage (Vp-p)

Resolution

Typical Accuracy 23

°C ± 5°C One Year [1]

330 mV

3.3 V

33 V

250 V

0.08 V

0.80 V

8 V

80 V

Full Scale reading

±0.95 V

±9.5 V

±95.0 V

±350.0 V

1 mV

10 mV

100 mV

1 V

2.0%

±17 mV

3% ±160 mV

3% ±1.4 V

3% ±12 V

[1] Median measurements require a repetitive signal with frequency range of 30 Hz to 30 KHz.

2.4 AC Current Measurement, True RMS

Input Characteristics

Burden Voltage < 350 mV RMS all Ranges

Crest Factor 3 at Full Scale, increasing to 7 at Lowest Specified Current

Protected with 2.5 A fuse ( 5x20 mm, 250 V Fast)

Range

3.3 mA

33 mA

330 mA

2.5 A

Full Scale 6 1/2 Digits

3.300000 mA

33.00000 mA

330.0000 mA

2.500000 A

Lowest Specified Current Resolution

50

µA

500

µA

1 nA

10 nA

5 mA 100 nA

50 mA 1 uA

Accuracy ± (% of reading + Amps)

Range

3.3 mA

33 mA

330 mA

2.5 A

Frequency 24 hours

23

°C ± 1°C

10 Hz - 20 Hz

3.8 + 4

µA

20 Hz - 47 Hz

47 Hz - 1 kHz

1 kHz - 10 kHz

10 Hz - 20 Hz

20 Hz - 47 Hz

47 Hz - 1 kHz

1 kHz - 10 kHz

10 Hz - 20 Hz

20 Hz - 47 Hz

47 Hz - 1 kHz

1 kHz - 10 kHz

0.9 + 4

µA

0.04 + 1.5

µA

0.12 + 4

µA

1.8 + 30

µA

0.6 + 30

µA

0.07 + 10

µA

0.21 + 30

µA

1.8 + 400

µA

0.6 + 400

µA

0.1 + 100

µA

0.3 + 300

µA

10 Hz - 20 Hz

20 Hz - 47 Hz

47 Hz - 1 kHz

1 kHz - 10 kHz

1.8 + 4 mA

0.66 + 4 mA

0.6 + 3.8mA

0.6 + 4mA

90 Days

23

°C ± 10°C

2.7 + 4

µA

0.9 + 4

µA

0.08 + 3

µA

0.14 + 4

µA

2.6 + 30

µA

0.9 + 30

µA

0.15 + 20

µA

0.3 + 40

µA

2.7 + 400

µA

0.9 + 400

µA

0.17 + 180

µA

0.4 + 350

µA

2.5 + 4.5 mA

0.8 + 6 mA

0.63 + 3.8 mA

0.62 + 4.5 mA

One Year

23

°C ± 10°C

2.9 + 4

µA

1.0 + 4

µA

0.12 + 4

µA

0.22 + 4

µA

2.8 + 30

µA

1.0 + 30

µA

0.16 + 30

µA

0.4 + 40

µA

2.8 + 400

µA

1.0 + 400

µA

0.22 + 220

µA

0.6 + 400

µA

2.7 + 5 mA

0.9 + 6 mA

0.65 + 4 mA

0.7 + 5 mA

Note: All AC Current ranges have typical measurement capability to 20 kHz.

11 Signametrics

2.5 Resistance Measurements

2.5.1 2-wire and 4-wire

Accuracy ± (% of reading +

Ω) [1]

Range [2]

33

Ω [3]

330

3.3 k

33 k

330 k

3.3 M

33 M

330 M

Ω [3]

Full Scale

6 ½ Digits

33.00000

330.0000

3.300000 k

33.00000 k

330.0000 k

Resolution Source 24 hours

10

µΩ

100

µΩ

1 m

Ω current

10 mA

1 mA

1 mA

23

°C ± 1°C

0.0038 + 1 m

3.300000 M

33.0000 M

1

Ω 1

100

0.018 + 40

100 nA

0.12 + 400

330.00 M

10 k

10 nA

1 + 50 k

0.0037 + 4.5 m

0.0023 + 28 m

10 m

Ω 100

100 m

Ω 10

0.0055 + 3.2

90 Days

23

°C ± 10°C

0.005 + 1.5 m

0.0046 + 5 m

0.003 + 32 m

0.0033 + 330 m

0.007 + 4

0.03 + 50

0.13 + 500

1.4 + 60 k

[1] With reading rate set to 2 rps or slower, and within one hour of Ohms zero, using Relative control.

[2] 4-wire ohms is available up to the 330 k

Ω range.

[3] 33

Ω and 330 MΩ ranges are only available with the SMX2042,44.

2.5.2 6-wire Guarded Resistance Measurement (SMX2044)

Typical additional error contributed by guarding

Accuracy ± (% of reading +

Ω)

33

330

10 mA

1 mA

3.3 k

1 mA

33 k

Ω 100

330 k

Ω 10 current

°C ± 5°C [1]

0.3 + 4 m

0.003 + 20 m

0.005 + 100 m

0.03 + 1

0.35 + 10

[1] This table should be used in conjunction with the 2-wire and 4-wire table above.

One Year

23

°C ± 10°C

0.008 + 2 m

0.007 + 6 m

0.005 + 33 m

0.006 + 350 m

0.009 + 5

0.04 + 70

0.2 + 600

2.0 + 80 k

2.6 Leakage Measurement (SMX2044)

Accuracy ± (% of reading +

Ω) [1]

Leakage Reading Voltage range

One Year 23

°C ± 5°C [1]

1.00

ηA to 100.00 ηA

100.00

ηA to 1000.00ηA

1000.00

ηA to 3.3 µA

-10 V to +10 V

-9 V to + 9 V

-7 V to + 7 V

2 + 350 pA

1.2 + 2

ηA

1.5 + 20

ηA

[1] Error does not include external shunt resistor’s tolerance.

2.7 RTD Temperature Measurement (SMX2044)

RTD Type

pt385, pt3911, pt3916, pt3926

Ro (

Ω)

100, 200

Resolution Temperature

Ω 0.01°C range

Temperature Accuracy 23

°C ± 5°C [1]

One Year

-150 to 650

°C ±0.06°C

pt385, pt3911, pt3916, pt3926

500, 1 k

Ω 0.01°C

-150 to 650

°C ±0.03°C

Cu (Copper)

Cu (Copper)

Less than 12

Ω 0.01°C

Higher than 90

Ω 0.01°C

-100 to 200

°C ±0.18°C for temperatures ≤ 20°C, ±0.05°C otherwise

-100 to 200

°C ±0.10°C for temperatures ≤ 20°C, ±0.05°C otherwise

[1] With reading rate set to 2 rps or slower, using a 4-wire RTD. Measurement accuracy does not include RTD probe error.

Signametrics 12

2.8 Additional Component Measurements

2.8.1 Diode Characterization

Available DC current values 100 ηA, 1 µA, 10 µA, 100 µA and 1 mA. SMX2042 and SMX2044 add 10 mA. SMX2044 has a variable current from 10

ηA to 12.5 mA using the DCI source.

Typical Current Value Uncertainty 1%

Typical Voltage Value Uncertainty 0.02%

Maximum diode voltage compliance 4 V

2.8.2 Capacitance Measurement (SMX2042, 44)

Accuracy ± (% of reading + Farads) [1]

10

ηF

Scale Resolution One Year

4 ½ Digits

23

°C ± 5°C

11.999

ηF

1 pF 2.1 ± 5 pF

100

ηF 119.99

1

µF 1.1999

1 mF

10 mF

1.1999 mF

11.999 mF

10 pF

100 pF

10

µF 11.999 ηF

100

µF 119.99 ηF

100

ηF

1

µF

1.0

1.0

1.0

1.0

1.2

2

[1] Within one hour of zero, using Relative control. Accuracy is specified for values higher than 5% of the selected range with the exception of the 10

ηF range, which measures down to 0 pF.

2.8.3 Inductance Measurement (SMX2044)

33

µH

330

µH

3.3 mH

33 mH

330 mH

3.3 H frequency

75 kHz

50 kHz

4 kHz

1.5 kHz

1 kHz

100 Hz

± (% of reading + inductance) [1]

Resolution

4 ½ Digits

33.000

µH

1

ηH

330.00

µH 10

3.3000 mH

33.000 mH

330.00 mH

3.3000 H

100

ηH

1

µH

10

µH

100

µH

Accuracy 23

°C ± 5°C

One Year [2]

3.0% + 500

ηH

2.0% + 3

µH

1.5% + 25

µH

1.5% + 200

µH

2.5 + 3 mH

3 + 35 mH

[1] Within one hour of zero, and Open Terminal Calibration.

[2] Accuracy is specified for values greater than 5% of the selected range.

2.8.4 In Circuit AC-Based Capacitance Measurements (SM2044)

Accuracy ± (% of reading + Farads) [1]

Scale Resolution One Year

4 ½ Digits

23

°C ± 5°C

33

ηF

32.99

ηF

330

ηF 329.9

10 pF

100 pF

12% ± 250 pF

5% ± 500 pF

3.3

µF 3.299

1000 pF

33

µF 32.99 ηF

330

µF 329.9 ηF

3.3 mF 3.299 mF

1

µF

4% ± 1

ηF

5% ± 20

ηF

5% ± 1

µF

7% ± 50

µF

[1] Specified to 2/3 of range (ie. 22

ηF

on 33nF range). Within one hour from last AC-Caps Open calibration. Add an error of 50e-6*R*C (%) due to paralled resistance.

13 Signametrics

2.9 Timing Measurements (SMX2042, 44)

2.9.1 Threshold DAC

The Threshold DAC is used for selecting a detection threshold to give optimal frequency and

timing measurements.

± (% of setting + volts)

Selected VAC range [1]

Threshold range (DC level)

Highest allowed input

Vp-p

Typical one year setting uncertainty

330 mV

3.3 V

33 V

250 V

-1.0 V to +1.0 V

-10.0 V to +10.0 V

-100.0 V to 100.0 V

-500 V to 500 V

Threshold

DAC resolution

0.5 mV

5.0 mV

50 mV

500 V

1.900 V

19.00 V

190.0 V

850.0 V

0.2% + 4 mV

0.2% + 40 mV

0.2% + 0.4 V

0.2% + 4 V

[1] This table should be used in conjunction with the AC volts section above.

2.9.2 Frequency and Period Measurement

ACV Mode

Input Impedance 1 M

Ω with < 300 pF

Frequency Range 1 Hz - 100 Hz 100 Hz-1 kHz 1 kHz-10 kHz 10 kHz-100 kHz 100 kHz-300 kHz

Resolution

Uncertainty is ±0.002% of reading ± adder shown

Input Signal Range [1]

1 mHz

4 mHz

10% - 200% of range

10 mHz

20 mHz

10% - 200% of range

100 mHz

200 mHz

10% -200% of range

1 Hz

2 Hz

10% - 200% of range

1 Hz

5 Hz

45% -200% of range

[

1] Input RMS voltage required for a valid reading. Do not exceed 250 V RMS input. For example, 10% -200% of range indicates that in the 330 mVAC range, the input voltage should be 33 mV to 660 mV RMS.

ACI Mode

Input Impedance 10

Ω in the 3 mA and 30 mA ranges, 0.1 Ω in the 330 mA and 2.5 A ranges.

Frequency Range 1 Hz - 100 Hz 100 Hz-1 kHz 1 kHz-10 kHz 10 kHz-500 kHz

Resolution

Uncertainty

Input Signal Range,

3.3 mA, 330mA Ranges

[1]

Input Signal Range,

33 mA, 2.5A ranges

1 mHz

0.01% ±4 mHz

10% -500% of range

50% -100% of range

10 mHz

0.01% ±20 mHz

10% - 500% of range

50% - 100% of range

100 mHz

0.01% ±200 mHz

10% -500% of range

50% - 100% of range

1 Hz

0.01% ±2 Hz

10% - 500% of range

50% - 100% of range

[1] Input current required to give a valid reading. For example, 10% -500% of range indicates that in the 3.3 mA range, the input current should be 0.33 mA to 16.5 mA.

2.9.3 Duty Cycle Measurement

Frequency Range 1 Hz to 100 Hz 100 Hz to 1 kHz 1 kHz to 10 kHz 10 kHz to 100 kHz

Resolution 0.02% 0.2% 2% 20%

Typical Uncertainty is

±0.03% of reading ± adder shown

Full scale reading

0.03%

100.00 %

0.3%

100.00 %

3%

100.00 %

20%

100.00 %

2.9.4 Pulse Width

± (% of reading + sec)

Signametrics 14

Polarity

Positive or negative pulse widths

Frequency range

1 Hz to 100 kHz

Resolution

2

µs

2.9.5 Totalizer

• Active edge polarity: Positive or negative transition

• Maximum count: 10^9

Allowed rate: 1 to 30,000 events per second

Uses Threshold DAC

Width range

2

µs to 1 s

Typical

Uncertainty

0.01 +/- 4

µs

2.10 Trigger Functions

2.10.1 External Hardware Trigger (at DIN-7 connector)

Trigger Input voltage level range

Ttrigger High current drive

Timing Characteristics

Trigger Activation

Internal Reading Buffer

Isolation of trigger input

High: +3V to +15V, Low: -15V to +0.8V

Min. 1mA, Max 10mA (TTL or CMOS logic level)

Trigger occurs within 2/Reading rate

Positive or Negative edge depending on trigger command.

Up to 1,000 readings/sec into 64 locations reading buffer

±50 V from analog DMM inputs, and from computer chassis earth ground.

2.10.2 PXI Bus Hardware Trigger Inputs (at PXI J2)

Trigger Input

Trigger Pulse Width

Internal Reading Buffer

Selectable lines

Isolation from DMM inputs

TTL or CMOS positive pulse

Minimum 250

µS up to 1,000 readings/sec into 64 readings buffer

PXI_TRIG1,2,3,4,5,6,7 and PXI_STAR

±330 V from any of the DMM 4 main inputs terminals

2.10.3 PXI Bus Hardware Trigger Output (to PXI J2)

Trigger Output

Trigger Pulse Width

Activity

Selectable lines

Isolation from DMM inputs

TTL or CMOS negative pulse. Positive edge = ready

Approximately 140

µS

A single pulse is issued for each A/D conversion (at 10 or higher measurement rate)

PXI_TRIG1,2,3,4,5,6 and PXI_STAR

±330 V from any of the DMM 4 main inputs terminals

2.10.4 Analog Threshold Trigger

• Captures up to 64 readings

Reading rate: 10 rps or higher

15 Signametrics

2.11 Source Functions (SMX2044)

• Isolated to 300 V DC from the Chassis

• Current can be paralleled with multiple SMX2044s

Voltage can be put in series with multiple SMX2044s

2.11.1 DC Voltage Source

Parameter

Output Voltage range

Typical Current source/sink at 5V output

DAC resolution

Accuracy 23

°C ± 10°C One Year

Typical settling time

Typical source resistance

Closed Loop [1] Open Loop

-10.000 V to +10.000 V

5 mA

18 bits

0.015% ± 350

µV

3 S (rate set to 2/s)

5 mA

12 bits

1.0% ± 35 mV

1 mS

250

[1] 10 rps or lower measurement rate is required for the closed loop mode.

2.11.2 AC Voltage Source

Parameter

Output Voltage, sine wave

DAC resolution

Typical Current Drive at 3.5V RMS

Accuracy 18°C to 28°C One Year

Typical settling time (f-out > 40 Hz)

Typical source resistance

Frequency range / resolution

Frequency stability

Closed Loop [1] Open Loop

50mV to 7.1 V RMS (0.14 to 20.0V peak-to-peak)

16 bits 12 bits

3.5 mA RMS

ACV spec ± 2 mV ACV spec + 0.8% ± 20 mV

10 s (rate set to 2 rps)

250

2 Hz to 75 kHz / 2 Hz

1.5 s

100 ppm ± 1 Hz

[1] 5 rps or lower measurement rate is required for the closed loop mode.

2.11.3 DC Current Source

1.25

µA

4.2 V

12.5

µA

4.2 V

125

µA

4.2 V

1.25 mA 4.2 V

12.5 mA 1.5 V

Voltage Minimum level

Accuracy 23

°C ± 10°C One Year

500 pA

1

ηA

1% + 10

ηA

5

5

ηA 10

50

ηA 100

500

ηA 1

µA 10

1% + 100

ηA

1% + 500

ηA

1% + 5

µA

1% + 50

µA

[1] Resolution without Trim DAC. The use of the Trim DAC can improve the resolution by a factor of 10, but it has to be set separately since it is not calibrated.

Signametrics 16

2.12 Accuracy Notes

Important All accuracy specifications for DCV, Resistance, DCI, ACV, and ACI apply for the time periods shown in the respective specification tables. To meet these specifications, the System Calibration function must be performed once a day. System Calibration is a simple software operation that takes a few seconds. Do it by executing the DMMCalibrate() command, or selecting S-Cal in the control panel.

All three products are capable of continuous measurement as well as data transfer rates of up to 1,000 readings per second (rps). To achieve the 6-1/2 digit resolution, the DMM should be operated at 5 rps or slower. The maximum reading rate for 5-1/2 digits is 30 rps.

Accuracy vs. Reading Rates All of the above specifications apply to reading rates of 2 rps or lower. For higher reading rates, increase the noise floor for DCV, Resistance, and DCI by the square root of the increase in reading rate from 2 rps. For example, the noise floor for the 3 .

3 VDC range is 8

µV at 5 rps. At 20 readings per second, or

10x the reading rate, the noise increases by the square root of 10, or 3.16 times. The noise, then, at 20 readings per second is ± 25

µV.

The noise characteristics for the AC functions increases by the same number as the DC functions. For example, the noise floor for the 3.3 VAC, 20 rps, will have digit rattle of 8.7 mV vs. 2.75 mV at 2 rps.

Reading Rates vs. Noise Rejection The best AC (50 Hz, 60 Hz or 400 Hz) power line rejection is obtained at reading rates that are whole number divisions greater than 1 of the line frequency, as shown in the following table.

For best AC line rejection you should use the reading rates checked. It is important to follow this table. Always use the lowest checked rate that is practical for the application.

Reading Rate (rps)

0.1

0.2

0.5

1

2

5

10

Power Line frequency

50 Hz

60 Hz

400 Hz

15

20

25

√ √

30

40

50

√ √

60

80

100

200

400

Reading Rates vs. Digits of Resolution For reading rates of 10 readings per second (rps) and slower, the DMM has 6 ½ digits of resolution. For reading rates from 10 rps to 30 rps, the DMM has 5 ½ digits of resolution.

17 Signametrics

Temperature Coefficient, All Functions

Reading Rate

(user selectable)

Less than 0.1 x accuracy specification per

°C at 23C

± 5°C

Hardware Interface

Overload Protection (voltage inputs)

• 0.5 to 1,000 readings per second (rps)

• Up to 10 rps, 6 ½ digits

• Up to 30 rps, 5 ½ digits

Single 3U PXI or CompactPCI slot

330 VDC, 250 VAC

Isolation 330 VDC, 250 VAC from Earth Ground

Maximum Input (Volt x Hertz) 8x106 Volt x Hz normal mode input (across Voltage HI &

LO).

1x106 Volt x Hz Common Mode input (from Voltage HI or

LO relative to Earth Ground).

Designed to IEC 1010-1, Installation Category II.

Safety

Calibration

Calibrations are performed by Signametrics in a computer with a 3

°C internal temperature rise. All calibration constants are stored in a text file.

Range

°C to 70°C, operating

-65

°C to +85°C, storage

Size

DMM Internal Temperature

Measurement (SMX2042, 44)

7” X 3.5” (Standard PXI/CompactPCI 3U format)

±2°C

Note: Signametrics reserves the right to make changes in materials, specifications, product functionality, or accessories without notice.

Accessories

Several accessories are available for the SMX2040 DMMs, which can be purchased directly from Signametrics, or one of its approved distributors or representatives. These are some of the accessrories avaialble:

• DMM probes SM-PRB ($15.70)

• DMM probe kit SM-PRK ($38.50)

• Delux probe kit SM-PRD ($95.00).

• Shielded SMT Tweezer Probes SM-PRSMT ($24.90).

• Multi Stacking Double Banana shielded cable 36” SM-CBL36 ($39.00).

• Multi Stacking Double Banana shielded cable 48” SM-CBL48 ($43.00).

• Mini DIN Trigger, 6-Wire Ohms connector SM2040-CON7 ($14.00).

• LabView VI’s library SM204x.llb ($99.00).

Signametrics 18

3.0 Getting Started

After unpacking the DMM, please inspect for any shipping damage that may have occurred, and report any claims to your transportation carrier.

The DMM is shipped with the Digital Multimeter module; three floppy disks containing the various software panels and drivers plus the calibration data specific for the unit, and this Operator's manual.

3.1 Setting the DMM

The SMX2040 series DMMs are PXI/CompactPCI Plug&Play devices and do not require any switch settings, or any other adjustments to the DMM prior to installation. The only switches are the PXI trigger input and output selection switches, capable of selecting one of the PXI triggers and PXI Start Trigger.

The SM40CAL.DAT file supplied with your DMM has a unique calibration record for that DMM (See

"Calibration" at the end of this manual.) When using multiple DMMs in the same chassis, the SM40CAL.DAT file must have a calibration record for each DMM. Append the unique calibration records of each DMM into one

SM40CAL.DAT file using a text editor such as Notepad. The defalut location for the SM40CAL.DAT file is at the root directory C:\.

3.2 Installing the DMM Module

Warning

To avoid shock hazard, install the DMM only into a chassis that has its power line connector connected to an

AC receptacle with an Earth Safety ground.

After installation, check to see that no loose wires or ribbon cables infringe upon any of the internal circuits of the DMM, as this may apply measurement voltages to your chassis, causing personal injury and/or damage to your equipment!

This module is designed for 3U PXI and CompactPCI chassis. To prevent shock hazard do not plug it into

other format chassis such as 6U without making shure that all sides of the DMM are covered.

Caution: Only install the DMM module with the power to the chassis turned OFF!

Use extreme care when plugging the DMM module(s) into a PXI or CompactPCI chassis. If possible, choose an empty slot away from any high-speed boards (e.g. CPU or other noisy modules) or the power supply. Please be

patient during the installation process! Due to it’s shielding it is a tight fit. Watch for any interference between the module and the chassis. Gently push the DMM into the chassis, making shure the handle is correctly located.

Once in, lock it in with the handle and tighten the top and bottom screws to secure it into the chassis.

Be patient!

3.3 Installing the DMM software package

To install the DMM, turn off the PXI/CompactPCI chassis, plug in the DMM into the PXI/CompcatPCI chassis, preferably away from the CPU or any other noisy card, than turn on the power. The first time you power up your computer with the DMM installed, your Windows system will detect the new DMM and will open the “New

Hardware found” wizard. It will prompt you for a driver. Insert Disk1 which contains the necessary driver.

To complete the installation, run the ‘SETUP’ program provided on the Diks1. This takes care of all installation and registration requirements of the software. If you are installing the DMM on a computer that had an SMX2040 series install in it, you should first uninstall the old software. For a clean reintallation remove all INF files containing reference to the Signametrics DMM. Dependig on operating system, these files will be located at

Windows\inf, Windows\inf\other or WINNT\inf. The files will be named Oemx.INF where x is 0,1,2,… and/or

SIGNAMETRICSSMX2040.INF. If present, these files will prevent “Found New Hardware” wizard from detecting the new DMM. Also, make sure you backup and remove the old calibration record (C:\SM40CAL.DAT).

3.4 DMM Input Connectors

19 Signametrics

Before using the DMM, please take a few moments and review this section to understand where the voltage, current, or resistance and other inputs and outputs should be applied. This section contains important information

concerning voltage and current limits. Do not exceed these limits, as personal injury or damage to the instrument, your chassis or application may result.

F igure 3-1. The DMM input con nectors.

V ,

+ This is the positive termin sourcing of VDC, VAC and IDC.

+ and V,

- is 300 VDC or 250 V al for all Volts, 2W

Ω, capacitance, di

It is also the Source HI for 4

AC when in the measuring

W

Ω measurem

m ode and inductance measurements, and for ents. The maximum input across V,

ode. When in the sourcing mode, the maximum

input allow ed before damage occ urs is 100 volts.

V,

- This is the negative terminal for all Volts, 2WΩ, capacitance diode and inductance measurements, and or sourcing of VDC, VAC and IDC. It is also the Source LO for 4W

Ω. Do not float this terminal or any other

DMM terminal more than 300 VDC or 250 VAC above Earth Ground. (Also, see Trig, 6W Guard below.)

I + This is the positive terminal for all Current measurements. It is also the Sense HI for 4W

Ω measurements and

6W

Ω guarded measurements. The maximum input across I, 4W + and I, 4W - is 2.5 A. Do not apply more than

5 V peak across these two terminals!

I – This is the negative terminal for all Current measurements. In the Current modes, it is protected with a 2.5 A,

250 V Fast Blow fuse (5 x 20 mm). It is also the Sense LO for 4W

Ω measurements and 6WΩ guarded measurements. V,

- and I, 4W - should never have more than 5 V peak across them.

TRIG GUARD Both the Trigger and Guard functions use the DIN-7 connector. This group of pins include the positive and negative hardware trigger input lines and the two SMX2044 Guarded Measurement Force and Sense signals. The external trigger initiates reading(s) into the onboard buffer, and the 6W guard signals facilitate in-

Signametrics 20

circuit resistor measurements by means of isolating a loading node. The DIN-7 plug can be ordered from

Signametrics and is available at many electronic hardware distributors. The connector is generically referred to as a mini DIN-7 male. The trigger signal should be in the range of 3 V to 12 V peak. The two 6W guard signals should never have more than 5 V peak across them.

Warning! The DIN connector pins are protected to a maximum of 35 V with respect to the chassis and any other DMM terminal. Do not apply any voltages greater than 35 V to the DIN connector pins. Violating this limit may result in personal injury and/or permanent damage to the DMM.

DIN-7, Pin number

7

4

1

6

Function

External Trigger, Positive terminal

External Trigger, Negative terminal

Guard Source (SMX2044)

Guard Sense (SMX2044)

DIN-7 Connector Pin Description, view from bracket side.

3 .5 Starting the Control Panel

You can verify the installation and gain familiarity with the DMM by exercising its measurement functions using the Windows based Control Panel. To run the control panel, double click the “SMX2044.EXE”. If you do not hear the relays click, it is most likely due to an installation error. Another possible source for an error is that the

SM40CAL.DAT file does not correspond to the installed DMM.

The Control Panel is operated with a mouse. All functions are accessed using the left mouse button. When the

DMM is operated at very slow reading rates, you may have to hold down the left mouse button longer than usual for the program to acknowledge the mouse click.

Note: The SMX2040 front panel powers up in DCV, 2 readings per second, 330 V range. If the DMM is operated in

Autorange, with an open input, you may hear the SMX2040 relays clicking every few seconds, as a range change occurs. This is perfectly normal with ultra high impedance DMMs such as the SMX2040. This phenomenon is caused by the virtually infinite input impedance of the 330 mV and 3.3 V DCV ranges. On these ranges, an open input will read whatever charge is associated with the signal conditioning of the DMM. As this electrical charge changes, the SMX2040 will change ranges, causing the relay clicking. This is normal.

21 Signametrics

3.6 Using the Control Panel

Figure 3-2. The Control Panel for the SMX2044. The three main groups include Measure, Source and

R ange buttons. The 8 Range buttons are context sensitive such that only “330m, 3.3, 33 and 250 appear when in AC Voltage Functions, “3.3m 33m 330m 2.5” appear when in Current Functions, etc.

Note: All of the controls described below correspond to their respective software function, which can be invoked within your control software or as objects in a visual programming environment. Using the software command language of the SMX2040 provides powerful capabilities. Some composite functions are not included in the control panel above.

DC/AC This function switches between DC and AC. This is applicable for the following DMM functions:

Voltage, Current, and Voltage-Source. If Voltage-Source is the function presently in use, the Source control under the Tools menu can be used to set frequency and amplitude in ACV, and amplitude only in DCV and DCI.

Relative This is the Relative function. When activated, the last reading is stored and subtracted from all subsequent readings. This is a very important function when making low level DCV measurements, or in 2W

Ω. For example, when using 2W

Ω, you can null out lead resistance by shorting the leads together and clicking on Relative.

When making low level DC voltage measurements (e.g., in the

µV region), first apply a copper short to the V, +

& - input terminals, allow the reading to stabilize for a few seconds, and click on Relative. This will correct for any offsets internal to the SMX2040. The Relative button can also be used in the Percent and dB deviation displays

(s hown below), which are activated using the Tools in the top menu.

The Min/Max box can be used to analyze variations in terms of Min, Max, Percent and dBV. This display can be activated by selecting the Min/Max/Deviation from the Tools menue. For instance, testing a circuit bandwidth with an input of 1V RMS, activate t he

Relative function with the frequency set to 100Hz, than sweep gradually the frequency , and monitor the percent deviation as well as the dBV error and capture any response anomalies with the Min/Max display. The left display indicates peaking of 2.468%

(0.21 dBV) and maximum peaking in the response of +56.24mV and a notch of –

10.79mV from the reference at 100Hz.

Rate Box Controls the SMX2040 reading rate. 0.1 rps to 1,000 rps can be set. As measurement rate increases, so does the measurement noise. For best accuracy set to the lowest rate acceptable for the application. Also consider the line frequency (50/60 Hz) of operation when setting reading rates, as certain reading rates have more noise rejection at either 50 or 60 Hz. (See “Specifications” for details.) Generally, set the measurement rate to as low a rate as practical for the application. When measuring RMS values, there is no point setting the measurement rate to a value higher than 5 rps since the RMS circuitry has a settling time that is over a second.

The capacitance and inductance functions are not affected by rate setting.

Note on Measurement Rate: All three products are capable of continuous measurement as well as data transfer rates of up to 1,000 rps. To achieve the 6-1/2 digit resolution and accuracy, the DMM should be operated at 10 rps

or slower. The maximum reading rate for 5-1/2 digits is 30 rps.

Signametrics 22

Range Can be set to AutoRange or manual by clicking on the appropriate range in the lower part of the Windows panel. Autoranging is best used for bench top application and is not recommended for an automated test application due to the uncertainty of the DMM range, as well as the extra time for range changes. Locking a range is highly recommended when operating in an automated test system, especially to speed up measurements. Another reason to lock a range is to control the input impedance in DCV. The 330 mV and 3.3 V ranges have virtually infinite input impedance, while the 33 V and 330 V ranges have 10 M

Ω input impedance.

S_Cal This function is the System Calibration that corrects for internal gain, scale factor and zero errors. The

DMM does this by alternatively selecting its local DC reference and a zero input. It is required at least once every day to meet the SMX2040 accuracy specifications. We recommend that you also perform this function whenever the external environment changes (e.g. the temperature in your work environment changes by more than 5

°C, or the

SMX2044 on board temperature sensor indicates more than a 5

°C change). This function takes less than a few seconds to perform. Disconnect all leads to the DMM before doing this operation. Keep in mind that this is not a substitute for periodic calibration, which must be performed with external standards.

ClosedLoop This check box selection is used in conjunction with the AC and DC Voltage-Source functions of the

SMX2044. When checked, the DMM monitors the output level and continuously applies corrections to the output level. When not checked, the DMM is a 12 bit source vs. 16 bits in the ClosedLoop mode.

OpenCal This check box selection is used in conjunction with inductance measurement. It is necessary to perform

Open Terminal Calibration using this control, prior to measuring inductance. This function characterizes both the internal DMM circuitry as well as the probe cables. To perform OpenCal, attach the probe cables to the DMM, leaving the other end of the probe cables open circuited. Then, activate the OpenCal button.

Sync With this check box selection is active, the DMM measurements are internally synchronized, which reduces the measurement rate, but allows full scale input swings to be settled in single measurement.

Sources Panel

There are three function buttons in the Source group (SMX2044 only). The V, I, LEAK buttons select one of three source functions, Voltage (DC and AC), IDC and Leakage. The Sources Panel is automatically enabled when one of the source functions is enabled. It can also be invoked using the Sources Panel selection under the Tools menu. This panel allows the entry of values for all of the source functions, including Leakage.

The V-OUT Scroll bar and Text box are used to set the Voltage for DC and AC Volts as well as for

Leakage. When sourcing ACV, the voltage is in RMS and the FREQ. Scroll bar and Text box control the frequency of the source. It is also used to control inductance frequency. When sourcing DC current, use the I-OUT set of controls. When measuring timing or freqeuncy the THRESH set of controls is used for comperator threshold. All of the source controls are context sensitive and will be enabled when appropriate.

23 Signametrics

4.0 DMM Operations and Measurements

Most of the SMX2040 measurement functions are accessible from the Windows Control Panel (Figure above). All of the functions are included in the Windows DLL driver library. To gain familiarity with the SMX2040 series

DMMs, run the Windows ‘SETUP.EXE’ to install the software, then run the DMM, as described in the previous section. This section describes in detail the DMM’s operation and measurement practices for best performance.

4.1 Voltage Measurement

Measures from 0.1

µV to 300 VDC or 250 VAC. Use the V, + and V, - terminals, being certain to always leave the I+, I- and DIN-7 terminals disconnected. Use the AC/DC button on the Control Panel to switch between AC and

DC.

Making Voltage Measurements is straightforward. The following tips will allow you to make the most accurate voltage measurements.

4.1.1 DC Voltage Measurements

When making very low level DCV measurements (<100

µV), you should first short the DMM with a copper wire shorting plug across the V,

+ and V, - terminals and perform the Relative function to eliminate zero errors before making your measurements. A common source of error can come from your test leads, which can introduce several

µVolts of error due to thermal voltages. To minimize thermal voltaic effects after handling the test leads, you should wait a few seconds before making measurements. Signametrics offers several high quality probes that are optimal for low level measurements.

Note: The SMX2040 front panel powers up in DCV, 2 readings per second, 330 V range. If the DMM is operated in

Autorange, with an open input, you may hear the SMX2040 relays clicking every few seconds, as a range change occurs. This is perfectly normal with ultra high impedance DMMs such as the SMX2040. This phenomenon is caused by the virtually infinite input impedance of the 330 mV and 3.3 V DCV ranges. On these ranges, an open input will read whatever charge is associated with the signal conditioning of the DMM. As this electrical charge changes, the SMX2040 will change ranges, causing the relays to click. This is normal.

Signametrics 24

4.1.2 True RMS AC Voltage Measurements

ACV is specified for signals greater than 1mV, from 10 Hz to 100 kHz. The ACV function is AC coupled, and measures the true RMS value of the waveform. As with virtually all true-RMS measuring meters, the SMX2040 may not read a perfect zero with a shorted input. This is normal.

ACV measurements, if possible, should have the NEUTRAL or GROUND attached to the SMX2040 V,

- terminal. See Figure 4-1, below. This prevents any “Common Mode” problems from occurring (Common Mode refers to floating the SMX2040 V,

LO above Earth Ground.) Common Mode problems can result in noisy readings, or even cause the computer to hang-up under high V x Hz input conditions. In many systems, grounding the source to be measured at Earth Ground (being certain to avoid any ground loops) can give better results.

Figure 4-1. Make Voltage measurements with the source ground attached to the SMX2040 V,

- to minimize “Common Mode” measurement problems.

4.1.3 AC Peak-to-Peak and Crest Factor Measurement (SMX2044)

Measurement of Peak-to-Peak, Crest Factor and AC Median values requires a repetitive waveform between 30 Hz and 100 kHz. The DMM must be in AC voltage measurement mode, with the appropriate range selected. Knowing the Peak-to-Peak value of the waveform is useful for setting the Threshold DAC (described below). This latter function is a composite function, and may take over 10 seconds to perform.

25 Signametrics

4.1.4 AC Median Value Measurement (SMX2044)

To better understand the usage of this function, you should note that the DMM makes all AC voltage measurements through an internal DC blocking capacitor. The voltage is thus “AC coupled” to the DMM. The measurement of the

Median value of the AC voltage is a DC measurement performed on the AC coupled input signal. This measurement returns the mid-point between the positive and negative peak of the waveform. The Median value is used for setting the comparator threshold level for best counter sensitivity and noise immunity. (It is difficult to measure the frequency of a low duty cycle, low amplitude AC signal since there is DC shift at the comparator input due to the internal AC coupling. The SMX2044 overcome this problem by allowing you to set the comparator threshold level).

For further information on the usage of AC Median value and Peak-to-Peak measurements, and the Threshold DAC, see the “Frequency and Timing Measurements” section below.

This function requires a repetitive signal. The DMM must be in AC voltage measurement mode, with the appropriate range selected.

4.2 Current Measurements

The SMX2040, 42, 44 measure from 10

ηA to 2.5 A. Use the I, 4W terminals, being certain to always leave the

V,

+ & - terminals disconnected. Use the AC/DC button to switch between AC and DC.

The Current functions are protected with a 2.5 A, 250 V fuse.

Warning! Applying voltages > 35 V to the I+, I- inputs can cause personal injury and/or damage to your

DMM and computer! Think before applying any inputs to these terminals!

When making sensitive DC current measurements, be sure to use the Relative function to zero out any residual errors of the SMX2040. This is easily accomplished by opening all inputs to the SMX2040 and performing Relative in the appropriate DCI range.

Figure 4-2. AC and DC Current measurement connection.

4.2.1 Improving Current Measurements

W hen making sensitive DC current measurements, be sure to use the Relative function to zero out any residual erro rs of the SMX2040. This is easily accomplished by disconnecting all terminals to the DM M and performing

Relative in the appropriate DCI range. Using the S-Cal (DMMCalibrate()) prior to activating Relative will improve accuracy further. Although the SMX2040 family is designed to withstand up-to 2.5A indefinitely, be awa re that excessive heat may be generated when measuring higher AC or DC currents. If allowed to rise this heat may adversely effect subsequent measurements. In consideration with this effect, it is reco mmended that whenever

Signametrics 26

p ractical, higher current measurements be limited to short time. The lower two ranges of DC current may be effected by relay contamination. If the measurements seem unstable or high, while in IDC measurement, apply between 20mA and 50mA DC to the current terminals and clean the K2 relay using the DMMCleanRelay(0, 2,

200). Repeat this until the measurements are stable.

4.2.2 Low Level DC Curr ent Measurements

F or low level current measurements use the

V,

+ and V, - terminals. Using the 33V DCV range, the

SMX 2040 can measure very low currents. This hidden meas urement function is facilitated by the DMM’s low leakage front-end and a virtual 1

0.0M

input resistance. With a typical offset error of less than 100

µV in this VDC range, it is practical to measure down to 20pA. The maximum current m

value that can be easured has more to do with the user’s acceptable burden voltage (the voltage drop across the

1

0.0M

Ω shunt) then the DMM limitations. Assuming a maximum burden voltage of 3.3V the maximum current level is 330

ηA. This range is well within leakage measurements required in most semiconductor testing.

It is also a very quite and stable. Since the DMM does not have an explicit low current function, it i s necessary to calculate the current, which is equal to the measured voltage divided by

1

0.0M

Ω.

4.2.3 Extended DC Current Measurements (SM2044)

The leakage measurement function can also be used to measure low-level currents. Using a relatively high value shunt resistor and setting the leakage test voltage to 0V allows measurements of super low level currents, without any burden voltage. Read the leakage current section of the manual for more details.

4.3 Resistance Measurements

R esistance is measured with one of eight (six in the SMX2040) precision current sources, with the DMM displaying the resistance value. Most measurements can be made in the 2-wire mode. 4-wire ohms is used to make precision low resistance measurements. All resistan ce measurement modes are susceptible to Thermo-Voltaic (Thermal EMF) errors. See section section 4.3.5 for details.

4.3.1 2-wire Ohm Measurements

The DMM measure using 330

Ω to 33 MΩ ranges. The SMX2042 and SMX2044 add 33 Ω and 330 MΩ ranges.

Use the V,

+, V,- terminals, being certain to always disconnect the I+, I- terminals.

Most resistance measurements can be made using the simple 2-wire Ohms method. Simply connect V,

+ to one nd of the resistor, and the V,

- to the other end. If the resistor to be measured is less than 30 k

Ω, you should null e out any lead resistance errors by first touching the V,

+ and V,- test leads together and then performing a

Relative function. If making measurements above 300 k

Ω, you should use shielded or twisted leads to minimize noise pickup. This is especially true for measurements above 1 M

Ω.

You may also want to control the Ohms current used in making resistance measurements. (See the Specifications section, "Resistance, 2-wire and 4-wire", for a table of resistance range vs. current level.) All of the Ohms ranges of the SMX2040 have enough current and voltage compliance to turn on diode junctions. For characterizing semiconductor part types, use the Diode measurement function. To avoid turning on a semiconductor junction, you may need to select a higher range (lower current). When checking semiconductor junctions, the DMM displays a resistance value linearly related to the voltage across the junction.

For applications requiring resistance measurements higher than 330 M

Ω, the Extended Resistance Measurement method is available with the SMX2044.

4.3.2 4-wire Ohm Measurements

4-wire Ohms measurements are advantageous for making measurements below 330 k

Ω, eliminating lead resistance errors. The Voltage (V,

Ω) Input terminals serve as the current “Source” (i.e. they provide the current stimulus in the ohms measurement), and the I, 4W

Ω Input terminals are the “Sense” inputs. The Source + and Sense + leads are connected to one side of the resistor, and the Source - and Sense - leads are connected to the other side. Both Sense leads should be closest to the body of the resistor. See Figure 4-3.

4-wire Ohm makes very repeatable low ohms measurements, from 100

µΩ (10 µΩ for SMX2042, 44) to 330 kΩ. It is not not recommended to us 4W

when making measurements above 100 kΩ, although 4-wire ohms is allowed

27 Signametrics

up to 330 k

Ω. 4-wire measurements are disabled above 330 kΩ since the extra set of leads can actually degrade the accuracy, due to additional leakage and noise paths.

Figure 4-3. The I- and I+ sense leads should be closest to the body of the resistor when making 4W

Ω mea surements.

4.3.3 Using Offset Ohms function

Inadvertent parasitic leakage currents, Thermo voltaic voltages and other voltages in series can effect resistance measurements with the measured resistance. This is common particularly when doing in-circuit measurements, and it could manifest as having a significantly different readings when changing Ohms ranges. In addition to eliminating such error, this function can also be used to measure internal resistance of low value voltage sources such as variou s batteries and supplies. Use the normal 2-Wire or 4-Awire Ohms connection, and set the Offset Ohms to the enabled or disabled state using the DMMSetOffsetOhms() function. When set TRUE, the measurement rate will be about

1/10 th

of the set DMM rate. Both negative and positive polarity voltages can be handled as long as the total voltage including the Ohms source current times the measured resistance plus the parasitic voltage are less than 3.7V. To calculate this voltage consult the specification part of this manual for the specific current for each Ohms range. Th e default value of this function is FAL SE. This function is implemented for the SMX2040, SMX2042 and SMX2044.

D ue to it’s different hardware, the SMX2042 is different in that one of the DMM relays is being used to perform this operation, which can be heard.

4.3.4 6-wire Guarded Resistance Measurement (SMX2044)

The SMX2044 provides a guarded 6-wire resistance measurement method. It is used to make resistance measurements when the resistor-under-test has other shunting paths that can cause inaccurate readings. This method isolates the resistor-under-test by maintaining a guard voltage at a user-defined node. The gu ard voltage prevents th e shunting of the DMM Ohms source current from the resistor-under-test to other components. The Guard Source and Guard Sense terminals are provided at pins 1 and 6 of the DIN connector respectively.

Warning! The DIN connector pins are only protected to a maximum of 35 V with respect to the chassis or a ny other DMM terminal. Do not apply any voltages greater than 35 V to the DIN connector pins. Violating

this limit may result in personal injury and/or permanent damage to the DMM.

Example: Assume a 30 k

Ω resistor is in parallel with two resistors, a 510 Ω and a 220 Ω, connected in series. In

a normal resistance measurement, the 510

Ω and 220 Ω would shunt most of the DMM Ohms source current, causing

Signametrics 28

an inaccurate reading. By sensing the voltage at the top of the 30 k

Ω, and then applying this same voltage to the junction of the 510

Ω and 220 Ω, there is no current

S MX2044 accurately measures the 30 k

Ω resistor.

flow through the shunting path. With this “guarding”, the

Figure 4-4. 6-wire guarded in-circuit ohms measurement configuration.

The current compliance of the Guard Force is limited to a maximum of 20 mA and is short-circuit protected. The resistor connected between the low of the 4-wire terminals and the guard point is the burden resistor, or R b

. Due to the limited guard source current, this resistor can not be lower than R bmin

: R bmin

= I o

* R x

/ 0.02, where I o

is the ohms source current for the selected range, and R x

is the resistance being measured. For exa mple, selecting the 330

Ω range and measuring a 300 Ω resistor imposes a limit on R b

of at least 15

Ω or greater. Since the top burden resistor, R a

, does not have this limit imposed on it, selecting the measurement polarity, R a

can become R b

and vise versa. For cases where this limit is a problem, simply set the measurement polarity such that R a

is the higher of the two burden resistors.

To measure values greater than 330 k

Ω using the 6-wire guarded method, it is necessary to select the 2-wire ohms function, and maintain the 6-wire connection as in Figure 4-4 above.

4.3.5 Leakage Measurements (SMX2044)

The SMX2044 measures leakage currents by applying a DC voltage across the load and measuring the current through it. An external shunt resistor, R

S is used to sense the current. See Figures 4-5 for connection. The DC voltage at which leakage is measured is set using DMMSetDCVSource(), and the value of R

S

is entered using

DMMSetExternalShunt() (the default is 1 M

Ω). Leakage current is read using DMMRead(), DMMReadStr() or

DMMReadNorm() functions. Depending on the value of R

S

and the leakage current, the test voltage may be set between –10V and +10 V. Specifically; the maximum voltage is limited to 10.2V – (R

S

* I

L

). The leakage current

(I

L

) measurement range and accuracy depends on the shunt resistor being used. The range is set as 3.3V/R

S resolution of 10uV/R

S

. For instance, with R

S

, with

equal to 1M

Ω, the maximum leakage current is 3.3uA with resolution of 10pA, and at full scale the maximum test voltage is 6.7V. The test voltage is adjusted whenever a measurement is made. Therefore, if the leakage current being measured varies significantly over time, it is best to repeatedly read the DMM allowing the DMM to make corrections to the internal source voltage, compensating for drop across the shunt. Performing open terminal calibration will imrove the accuracy of this function (use

DMMOpenTerminalCal() with all terminals open). Refer to Figures 4-5. See section 2.6 for specifics. Setting the source to closed loop mode, DMMSetSourceMode(), will improve the accuracy of the test voltage.

29 Signametrics

Figure 4-5.

Leakage Test Configuration. Measurement of reverse diode leakage at 3.3V.

4.3.6 Extended Resistance Measurements (SMX2044)

The Extended Resistance measurement funct ion operates as complement of the standard resistance measurement.

W here the last forces a predefined current, this function forces sp ecified voltage. Where the normal resistance m easurement is limited to pre defined current sources, this function has a variable voltage, and it limits current flow by an external sense resistor. To perform this measurement use the connection diagram in Figure 4-6. Enter the value of the sense resistor R

S using DM MSetExternalShunt(), and set the test voltage with

D

MMSetDCVSource(). Due to the av ailability of a much higher test voltage than the normal resistance function, th is function is fit for very high value resistance measurements. On t he other hand, the ability to set to some low volt ages is significant in applications where specific test voltage is re quired such as to prevent semiconductor’s turn-on, or prevent sensitive sensors’ damage due to access voltage or current. The DMM compensates for the voltage drop across the sense resistor as to provide the specified test voltage. Each time the DMM makes a measurement using DMMRead(), DMMReadStr() or the DMMReadNorm, it adjusts the test voltage. There are several limitations that should be considered while using this function. The internal voltage source of the SM2044 i s limited to about +/-10.2V. Therefore the sum of the voltages across the sense resistor and the measured resistor is limited to this amount. Also the maximum voltage allowed across the sense resistor is limited to 3.3V. Exceeding either value will result in Over Range reading. The limit imposed by the shunt resistor may be expressed as V

L

/R

X

*

R

S

< 3.3V, where V

L

is the test voltage, R

X

is the resistance being measured, and R

S

is the external sense resistor value. The source voltage limit may be expressed as V

L

(1+R

S

/R

L

) < 10.2V. Use the DMMSetExternalShunt() to set the value of the external shunt being used. Use the DMMSetDCVSource() to set the test voltage (the voltage across the resistor being measured). For high value resistances, the shunt should be of high value and vise ve rsa.

This function is useful for testing high value resistive elements such as cables, transform ers, and other leaky objects such as printed circuit boards, connectors and semiconductors.

As an examp be 1.2122M

V si

S

. The s our

(1

. The sh un t voltage ce volta er ge l

Ω/5

Ω sh

V

S imit is rea

.001M

Ω unt

is at its limit h ched w hen V

) = 10.2

V. ol ere sin

L is set to 8 ce 1.0M

.5V and th e, the lowest resistor one can measure will

* 4V / 1.2122M

= 3.3V which is the limit for e measured resistance falls below 5.001M

Signametrics 30

Figure 4-6.

Extended Ohms range.

4.3.7 Effects of Thermo-Voltaic Offset

Resistance measurements are sensitive to Thermo-Voltaic (Thermal EMF) errors, which can be caused by poor test leads, relay contacts and other elements in the measurement path. These errors effect all measurement methods, including 2-Wire, 4-Wire, 6-Wire and 3-Wire (guarded 2-Wire ohms). To quantify this error, consider a system in which signals are routed to the DMM via a relay multiplexing system. Many vendors of switching products do not provide Thermal EMF specification. It is common to find relays that have more than 50

µV EMF. With several relay contacts in the path, the error is very significant. It is possible to measure it using the SMX2040 330mV DC range. To do this, close a single relay that is not connected to any load, wait for a short time (about 2 minutes), than measure the voltage across the shorted relay contacts. Make sure to short the DMM leads and set ‘relative’ to clear the DMM offset prior to the measurement. To calculate worst case error, count all relay contacts which are in series with the measurement (V,

+, V,- terminals in 2-Wire, and I+, I- terminals in 4-Wire mode). To calculate the worst case error, multiply this count by the Thermal EMF voltage. Use Ohms law to convert this voltage to resistance error as in the following table.

Resistance Measurement Errors due to Thermo-Voltaic offsets.

SM2042

Range

33

330

Ohms

Current

10 mA

1 mA

DMM

Resolution

10

Error due to

10

µV EMF

µΩ 1

Error due to

100

µV EMF m

Error due to 1 mV EMF

Ω 100

100

µΩ 10 m

Ω 1

3.3 k

1 mA

33 k

100 uA

1 m

Ω 10

10 m

Ω 100 m

Ω 1

330 k

10 uA

100 m

Ω 1

3.3 M

1 uA

1

Ω 10

33 M

100 nA

100

Ω 100 k

Ω 100

330 M

10 nA

10 k

Ω 1 k

Ω 100

31 Signametrics

4.3.8 Guarding High Value Resistance Measurements (SMX2044)

Measuring high value resistors using the 2-Wire function require special attention. Due to the high impedances involved during such measurements, noise pickup and leakage could be very significant. To improve this type of measurement it is important to use good quality shielded cables with a low leakage dielectric. Even with a good dielectric, if a significant length is involved, an error would result due to leakage. Figure 4.7 exemplifies this error source. It is important to emphasize that in addition to the finite leakage associated with the distributed resistance,

R

L

, there must also be a voltage present between the two conductors, the shield and the center lead, for leakage current to develop. Provided there was a way to eliminate this voltage, leakage would have been eliminated.

Figure 4-7. Error due to cable leakage.

The SM2044 provides an active guard signal that can be connected to the shield and prevent the leakage caused by the dielectric’s finite resistance. With the shield voltage guarded with Vx, as indicated in Figure 4-8, there is 0V between the shield and the high sense wire, and therefore no current flows through R

L

.

Figure 4-8. Guarding eliminates errors due to leakage associated with high resistance measurements.

4.4 RTD Temperature Measurement (SMX2044)

For temperature measurements, the SMX2044 measure and linearize RTDs. 4-wire RTD’s can be used by selecting the appropriate RTD type. Any ice temperature resistance between 25

Ω and 10 kΩ can be set for the platinum type RTDs. Copper RTDs can have ice temperature resistance values of 5

Ω to 200 Ω.

The highest accuracy is obtained from 4-wire devices, because the resistance of the test leads is nulled out. The connection configuration for RTDs is identical to 4-wire Ohms.

4.5 Internal Temperature (SMX2044)

Signametrics 32

A special on board temperature sensor allows monitoring of the DMM’s internal temperature. This provides the means to determine when to run the self-calibration function (S-Cal) for the DMM, as well as predicting the performance of the DMM under different operating conditions. When used properly, this measurement can enha nce the accuracy and stability of the DMM. It also allows monitoring of the chassis internal temperature, which is important for checking other instruments.

4.6 Diode Characterization

The Diode measurement function i s used for characterizing semiconductor part types. This function is designed to display a semiconductor device’s forward or reverse voltage. The DMM measures diode voltage at a selected current. The available source currents for diode I/V characterization include five DC current values; 100

ηA, 1 µA,

10

µA, 100 µA and 1 mA. The SMX2044 have an additional 10 mA range. The SMX2044 also has a variable current source which can be used concurrently with DCV measurement (see “Source Current / Measure Voltage”).

This allows a variable current from 10

ηA to 12.5 mA. The maximum diode voltage compliance is approximately 4

V.

Applications include I/V characteristics of Diodes, LEDs, Low voltage Zener diodes, Band Gap devices, as well as

IC testing and polarity checking. Typical current level uncertainty for diode measurements is 1%, and typical voltage uncertainty is 0.02%.

4.7 Capacitance Measurement (SMX2044)

The SMX2044 measure capacitance using a differential charge slew method, where variable currents are utilized to produce a dv/dt across the capacitor.

Use short high quality shielded probe cables with no more than 500 pF. With the exception of the 10

ηF range, each of the ranges has a reading span from 5% of range to full scale. Capacitance values less than 5% of the selected range indicate zero. Since some large value electrolytic capacitors have significant inductance, as well as leakage and series resistance, the Autoranging function may not be practical.

Because Capacitance measurement is sensitive to noise, you should keep the measurement leads away from noise sources such as computer monitors. For best measurement accuracy at low capacitance values, zero the DMM using the ‘Relative’ while in the 10

ηF range. The effect of the cable quality and its total capacitance is significant particularly on low value caps. For testing surface mount parts, use the optional Signametrics SMT Tweezer probes.

See Figure 4-9 for connection.

Figure 4-9.

Measuring capacitors or inductors is best handled with shielded probe wires.

33 Signametrics

4.8 In-Circuit Capacitance Measurement (SMX2044)

A second method provided for measuring capacitors i s the AC based method. Though not as accurate as the above fu nction, the advantage of this method is that the default stimulus is set at 0.45V peak, which is lower than a semiconductor junction on voltage. It may also be set over a wide ra nge of voltages. A further advantage is the ability of this function to measure capacitors that have a very low value parallel resistance, which is impossible to do using conventional methods. This test function operates by figuring the complex impedance and extracting from it both, the capacitance and resistance. The measurement is practical down to a few hundred Pico Farads, and up to several thousands micro Farads, with parallel resistances as low as 20

Ω to 300Ω depending on range. Once set to this function, use DMMRead(), DMMReadStr() and DMMReadNorm() to measure the capacitance value. To ge t the resistance value use DMMGetACCapsResist() following a read. Each of the ranges must be calibrated with open terminals prior to making measurements. Each range must be calibrated. Do this by activating the AC-Caps f unction, selecting the ran ge to be calibrated and issuing DMMOpenCalACCaps(). The last function normalizes the AC source signal. This open Calibration operation must be performed with the measurement cable or probes plugged into the DMM, with the other end open. See figure 4-9 above for connection. If not modified by the

DMMSetACCapsLevel() function, when making a measurement the DMM uses a default voltage of 0.45Vpk, w hich means that a sine wave that has a peak-to-peak amplitude of 0.9V. This level is used during both, open c alibration and measurements. Since the DMM is optimized for this value, and it is well below most semiconductors

On voltage, it is recommended not to change the level from this default value. The stimulus vo ltage can be set from

0.1V peak to 5V peak using the DMMSetACCapsLevel() function. Any time the stimulus level is adjusted; open calibration must be carried out. The results of DMMOpenCalACCaps() are kept in memory until the DLL is unloaded. Repeating Open calibration periodically will result in improved accuracy. AC Capacitance measurement function must be used with a DMM reading rate of 10rps. Other functions of interest for this operations are

D

MMSetACCapsDelay() and SetACCapsFre q().

4.9 Inductance Measure ment (SMX2044)

T he SMX2044 measures inductance using a precision AC so urce with a frequency range of 20 Hz to 75 kHz. Since indu ctors can vary greatly with frequency, you should choos e the appropriate generator frequency. In addition to inductance, the inductor’s Q factor can be measured. A shielded, high quality cable is highly recommended. F or best accuracy, perform the Open Terminal Calibration function within an hour of inductance measurements. The

Open Terminal Calibration function must be performed with the cables plugged into the DMM, but with the other end open circuited. This process characterizes the internal signal path inside the DMM, the open application cable , and the DMM circuitry.

For best measurement accuracy at low inductance values, zero the DMM often by using the ‘Relative’ function with the leads shorted. This must be done following Open Terminal Calibration operation. This Relative action measures and removes the inductance of the DMM signal path including that of the application cable being used.

4 .10 Characteristic Impedance Measurement (SMX2044)

To measure a transmission line’s characteristic impedance, measure the cable’s capacitance C (with the end of the cable open) and then it’s inductance L (with the end of the cable shorted). The cable’s impedance equals the square root of L/C. Be certain the cable is long enough such that both the capacitance and ind uctance are within the sp ecified measurement range of the SMX2044.

4.11 Trigger Operation

4.11.1 External Hardware Trigger

T he Trigger functions provide for a stand-alone capture of measurements. The local controller supervises the oper ation, and when conditions are valid, it captures data into its buffer, or send s it back to the PXI bus. The reading rate must be set to 10 rps or higher. The External Trigger’s isolated high and low input lines are provided at pins 7

(+) and 4 (-), respectively, on the DIN connector located on the front panel of the instrument. You may abort the

External Trigger’s wait state using the Disarm command. It is important to note that the External Hardware Trigge r is Wire-Ored with the PXI triggers. Therefore, while using the External Trigger, the PXI trigger input line selected

( see section 4.11.4) must be at a low logic level (inactive). While using the PXI trigger inputs as the trigger source, th e External Hardware trigger must at a low logic level, or disconnected. Failing to do this will result in a disabeled trigger. The PXI and External Hardware trigger software functions includes: DMMArmTrigger, which responds to

Signametrics 34

posi

tive edge, DMMSetBuffTrigRead, and DMMSetTrigRead have a se lectable edge parameter. Read about these functions in the Windows Command Language section (5.6) for details.

Warning! The DIN connector pins are only protected to a maximum of 30 V with respect to the chassis or any other DMM terminal. Do not apply any voltages greater than 30 V to the DIN connector pins. Violatin g this limit may result in personal injury and/or permanent damage to the DMM.

4.11.2 Analog Threshold Trigger

This mode trigg ers the DMM at a specific input level. A command to the DMM sets a threshold value and arms the

D MM Analog trigger. The DMM’s local controller waits for the level crossing and captures up to 64 readings, which are saved on board; at the current DMM measurement function, range and rate. The reading rate must be set to 10 rps or higher. You can abort this mode by sending the DMM a Disarm command to the Analog Trigger.

4.11.3 Software Issued Triggered Operations

There are several software trigger functions. They cause the DMM to make a single or multiple measurements, w ith or without setteling readings. These include DMMSetBuffTrigRead, DMMSetTrigRead, DMMTrigger,

DMMBurstRead, and DMMBurstBuffRead. Read about these functions in the Windows Command Language section (5.6) for details.

4.11.4 Using the PXI bus Trigger Facilities

The SMX2040 series of Digital Multimeters are designed to interface to the PXI J2 Triggers. That includes the

PXI_TRIG0 through PXI_TRIG6 and PXI_STAR trigger. The trigger to the DMM is a Wire-Ored function of the external trigger from the DIN-7 connector, and the PXI_TRIGn input. The data ready signal from the SMX2040 series can be selected to drive PXI_TRIG1 through PXI_TRIG6 or PXI_STAR trigger. Read section 4.10.1 to prevent Trigger input conflicts.

Figure 4-10.

PXI Trigger input/output selection switch is located near PXI J2 connector towards the back of the DMM.

4.11.4.1 PXI Trigger Outputs

The DMM issues a Data Ready pulse each time the A/D is done making a measurement, indicating data is ready to be read. A short (about 140

µs) negative pulse is issued for each measurement, with the positive edge indicating data is ready. The Trigger output is selected using S4, S5, and S6 DIP switch located near the PXI connector. The trigger pulse can be set to be output to any of the following lines.

35 Signametrics

Switch Settings

S6 S5 S4

0 0 0

0 0 1

0 1 0

0 1 1

1 0 0

1 0 1

1 1 0

1 1 1

Trigger Output Routing

Disables trigger output

PXI_TRIG1

PXI_TRIG2

PXI_TRIG3

PXI_TRIG4

PXI_TRIG5

PXI_TRIG6

PXI_STAR

4.11.4.2 PXI Trigger Inputs

The trigger input to the DMM is the wired-ored signal of the trigger input from the DIN-7 connector and the PXI bus trigger. Make sure that no signal is connected to the DIN-7 trigger input while the PXI trigger is in use. When using the DIN-7 trigger input make sure the the trigger input select switches are set to

Disabled position, or the selected PXI Trigger input is at a logic low level. Read about the operation of the

External Hardware trigger in the above sections, since that operation pertains to both, the external and the PXI trigger input operations. The Trigger input is selected using S1, S2, and S3 DIP switch located near the J2 connector of the DMM. The DMM trigger input may be selected from any of the following lines.

Switch Settings

S3 S2 S1

Trigger input Routing

0 0 0

0 0 1

0 1 0

0 1 1

Disables trigger input *

PXI_TRIG1

PXI_TRIG2

PXI_TRIG3

1 0 0

1 0 1

1 1 0

1 1 1

PXI_TRIG4

PXI_TRIG5

PXI_TRIG6

PXI_STAR

* - Rev-B hardware and above.

4.12 Frequency and Timing Measurements (SMX2042, 44)

While the maximum RMS reading is limited to the set range, you can use most of the timing functions even if the

RMS voltage reading indicates Overrange. This is true as long as the input peak-to-peak value does not exceed 5.75 times the selected range ( 5.75 x 330 mV = 1.9 V p-p with the 330 mV range).

4.12.1 Threshold DAC

All timing measurements utilize the AC Voltage path, which is AC coupled. You need to select the appropriate

ACV range prior to using the various frequency and timing measurement functions. The SMX2044 have a novel feature to accurately make these measurements for all waveforms. Unlike symmetrical waveforms such as a sine wave and square wave, non-symmetrical waves may produce a non-zero DC average at the frequency counter’s comparator input. Other DMMs have the comparator hard-wired to the zero crossing. The SMX2044 include a bipolar, variable Threshold DAC for improved performance of these measurements. The Threshold DAC allows the internal timing comparator to trigger at a specific DC level. Functions affected by the Threshold DAC include frequency, period, pulse-width, duty-cycle, and the totalizer.

The Threshold DAC has 12 bits of resolution. Depending on the selected ACV range, this bipolar DAC can be set from a few mV to effectively several hundred volts (referred to the input of the DMM), positive or negative. See the

Specifications sections for the limits of AC Median Value measurements and Threshold DAC settings.

The best setting of the Threshold DAC is based on the AC Median Value and Peak-to-Peak measurement described earlier. For example, a 5 V logic signal with 10% duty cycle will result in median value of 2 V, whereas a 90% duty cycle signal will have a –2 V median value. Setting the Threshold DAC to the appropriate median value will result in reliable and accurate timing measurements in each case.

Signametrics 36

Figure 4-11. AC coupled timing measurements with Threshold DAC.

With the 3.3 ACV range selected, a 10% duty-cycle square wave with 5 V peak-to-peak value, presents a peak-to-peak signal at the internal measuring circuits of –0.5 V to + 4.5 V. The AC Median Value is

+2.0 V. By setting the Threshold DAC to the Median value, the internal measuring circuits are properly biased for best performance.

Figure 4-12. Comparator and Threshold DAC Settings

4.12.2 Frequency and Period Measurements

Both Freq. and Per check boxes are only visible when ACV or ACI functions are selected. These check boxes are used to make frequency or period measurements. Freq. measures from 1 Hz to 300 kHz. When activated, the c ontrol panel alternately updates the amplitude reading followed by the frequency reading. The reading rate is slow er than indicated when frequenc y is activated. In the Windows control panel, period (Per) is also selectable.

Once the frequency range is acquired, Frequency and Period have a maximum measurement time of about 1 second.

It could take up to five measurements before the correct frequency range is auto-selected. This process is automatic.

Once within range, the next frequency measurement is made at the last selected range.

Both Frequency and Period measurement performance can be improved by properly setting the Threshold DAC, a novel feature of the SMX2044. See “Threshold DAC”, “AC Median Value”, and “Peak-to-Peak” measurements for further details.

37 Signametrics

4.12.3 Duty Cycle Measurement

Duty Cycle of signals from 1 Hz to 100 kHz can be measured. The minimum positive or negative pulse width of the signal must be at least greater than 2

µs. When measuring duty cycle precisely, the voltage at which the measurement is made is important, due to finite slew rates of the signal. The Threshold voltage can be set for precise control of the level at which duty cycle is measured. For best measurement results, set the Threshold DA C to the Median value. T his is particularly important for signals with low duty-cycle and small amplitude relative to the selected scale.

4.12.4 Pulse Width

User selectable positive or negative pulse widths may be measured for signal frequencies of 1 Hz to 100 kHz and shol a minimum pulse widths of 2

µs. The Thre d DAC feature allows measurements at a pre-defined signal level. See

Threshold DAC above for more det ails.

To measure pulse width, the DMM must be in the AC volts range appropriate for the input voltage. Keeping the peak-to-peak amplitude of the measured signal below 5.75 times the set range will guarantee the signal is within the li near regi on of the AC circuitry and gives the best performance.

4.12.5 Totalizer Event Counter

T he totalizer can be selected while the DMM is in the ACV mode. It is capable of counting events such as overvoltage excursions, switch closures, decaying resonance count, etc. The active edge polarity can be set for a positive or negative transition. A count of up to 10

9 can be accumulated. The maximum rate of accumulation is 30,000 events per second.

The Threshold DAC can be set for a negative or positive voltage value. See Threshold DAC above for more details.

Example One: To monitor and capture the AC line for positive spikes which exceed 10% of the nominal 120 V

RMS value, first select ACV 250 V range, than set the Threshold DAC to 186.7 V. This value is the peak value of

120 V RMS plus 10% (120V + 10%) X times this value was exceeded.

2

). Enable the Totalizer and read it periodically to get the number of

Example Two: Defects in coils, inductors, or transformers can be manifested as an increased decay, or greatly attenuated resonance when stimulated with a charged capacitor. The Totalizer function can be utilized to count transitions above a preset Threshold voltage as in the figure below.

Figure 4-13. Measuring inductor Q by counting transitions of decaying resonance with preset threshold.

Signametrics 38

4.13 Sourcing Functions (SMX2044)

The SMX2044 adds a number of sourcing functions, giving greater versatility for a variety of applications. All of the available sources, VDC, VAC, IDC, are isolated (floating with respect to the chassis). This allows sourcing with a significant common mode voltage as well as the ability to connect several SMX2044 units in parallel for increased

DC current, or in series for increased DC voltage.

Two digital-to-analog converters (DACs) are used for the source functions, a 12 bit DAC, and a Trim DAC. The last augments the 12 bit DAC to form a 16 bit composite DAC and adds an additional 8 bits of resolution. For functions requiring high precision, use both DACs by selecting the ClosedLoop mode, otherwise only the 12 bit

DAC is utilized. DCI source is limited to the 12 bit DAC only.

All three source functions use the V,

+, and the V,- terminals of the SMX2044.

4.13.1 DC Voltage Source

The SMX2044 has a fully isolated bipolar DC voltage source. Two modes of operation are available: fast settling or closed loop. In the Closedloop mode the DMM monitors the voltage source output, and updates it using the composite 16 bit DAC, at a rate proportional to the set measurement rate. The closedloop mode offers the best accuracy and resolution. A 10 rps or lower measurement rate is recommended for the Closedloop mode. In the fast settling mode, no adjustments are made and the 12 bit DAC is used. Up to

±10.0 V can be sourced, with 10 mA maximum drive. The output source resistance of the DCV source is approximately 250

Ω.

Figure 4-14. Sourcing DC voltage. The figure indicates the internal monitoring of the output in closed loop operation.

39 Signametrics

4.13.2 AC Voltage Source

The AC voltage source is fully isolated. It has two modes of operation: fast settling or closed loop. In the

Closedloop mode, the source voltage is monitored, and corrections are made to the composite 16 bit DAC at a rate proportional to the set measurement rate. A 10 rps or lower reading rate is recommended for the Closedloop mode.

The Closedloop mode offers the best accuracy. In the fast settling mode, the source voltage is monitored and can be displayed, but no DAC adjustments are made. Both amplitude and frequency can be set. The frequency range is

2 Hz to 75 kHz, and the amplitude is up to 20 V peak-to-peak with 10 mA maximum peak current drive. The output impedance is approximately 250

Ω.

Figure 4-15. Generating AC voltage. The figure indicates the internal monitoring of the output in closed loop operation.

4.13.3 DC Current Source

The SMX2044 has a fully isolated unipolar DC current source with five ranges. It uses the 12 bit DAC to control current level. This source function is useful for parametric component measurements as well as for system verification and calibration, where a precise DC current is necessary to calibrate current sensing components.

For improved resolution of the current source, use the Trim DAC. It has to be set separately, since it is not included in the calibration record, or the control software. Use DMMSetTrimDAC() command with a parameter of 0 to 100.

Further details are in Chapter 6.

4.13.4 Source Current - Measure Voltage

When sourcing current and measuring voltage, there are two connection configurations: 1) Four wire connection, where the current sourcing terminals and the voltage sense terminals are connected to the load, as in 4-wire Ohms measurement function; and 2) Two wire connection, where the current source terminals also serve as voltage sense probes as in the 2-wire Ohms measurement configuration. The first method eliminates lead resistance errors. One application is in semiconductor diode characterization discussed in Component Testing above. See Current Source

Output for range details. Voltage compliance is limited to 4 V in both configurations.

Signametrics 40

Figure 4-16. Sourcing DC current and meas uring voltage in the two wire configuration. This function can be used for semiconductor parametric tests.

T he SM2044 synthesizes resistance using an iterative method, which requires repeated reading of the DMM to m ake corrections to the synthesized value. While in synthesizing resistance, the readings return the measured value.

There are two basic circuit types into which resistance is synthesized; current source, such as the resistance function of another Multimeter, and voltage divider type load, as in a voltage divider circuit, where one of the two resistors in the network is being synthesized as in Figure 4-16. When synthesizing a resistance into a current source, it is important to consider its compliance voltage limits. For instance, a DMM’s 20k Ohms range will typically sources

100uA, and have a compliance limit of 2.5V. This means that the DMM current source does not behave as a curren t source when the voltage at its terminals is allowed to exceed 2.5V. Therefore synthesizing a resistance value greater than 25k

Ω (2.5V/100uA) will result in the SM2044 indicating an unstable reading.

For improved accuracy, perform open terminal calibration by using the DMMOpenTerminalCal() function with all terminals are open.

The following are limits that must be observed while synthesizing resistances:

Limitations synthesizing into current source:

1) The maximum load current, I

S

, is 10mA or 3.3/R

S

whichever is smaller. R

S

is the external resistor.

2) The maximum value that can be synthesized is 6.7/I

S

– 220 or V

C

/I

S

, whichever is smaller. V

C

is the current source compliance voltage.

3) Resistance settings resolution equals 0.1mV/ I

S.

is 100

Ω.

This means that with a source current of 1uA the resolution

Limitations synthesizing into a voltage divider:

1) The maximum current the SM2044 can provide to the load is 10mA or 3.3/R

S

, or (10 – V x

) / (R x

+ R s

+

220), whichever is smaller. R

S

is the external resistor.

2) The approximate value that can be synthesized is between 0.1 * R s

to about 100 * R s

41 Signametrics

S electing the appropriate external resistor is very important. It sets the accuracy and range of the synthesized value.

Functions associated with the synthesis of resistance include DMMSetExternalShunt(), wh ich sets the value of the external shunt, and DMMSetResistance(), which control the value to be synthesized. The external resistor shou ld be 100

Ω to 10MΩ. Set the measurement to 10 or higher. 20rps is optimal. The Closed loop flag does not hav e an effect on this function. R eselecting the function, or resetting the value has the effect of restarting the synthesis p rocess. This will speed up the acquisition time when condition change.

Figure 4-17. Synthesizing resistance into a voltage divider circuit.

Figure 4-18. Synthesizing resistance into a current source.

4.15 Interfacing to the SMX4032 series Relay Scanners

The SMX2040 series of Digital Multimeters are designed to interface to the SM4000 series relay scanners. The following section describes both, the hardware interface and the software functions required to implement a synchronized operation.

4.15.1 Triggering the SMX2040 DMMs

The SMX2040 series can accept a hardware trigger from many sources, including the SM4000 scanners. The latter can be setup to trigger a measurement any time the scanner selects a new channel. The interface requires a single jumper between the SM4000 Trig_com and Common lines, and a connection between the SM400 0 +5V and

TRIG_out to the SMX2040 Trigger inputs. The various SMX4032 auto scanning operations can run independently

Signametrics 42

from the computer, whereby the Scanner selects channels from its Scan List table, and the DMM is tri ggered to take measurements following each channel selection.

Figure 4-19. Trigger interfacing to an SMX2040 class of DMMs.

4.15.2 Multiplexing w ith th e S X20 40 DMMs

For two wire measurements, the SMX2040 DMM must be connected to the A-Bus or the scanner, or to b oth, the A-

Bus and C-Bus for 4-Wire measurements (assuming an SM4040 or SM4042 scanner). It is important to consider sy stem settling time when making measurements. Time delays exist in any measurement system. These delays are c ontributed by various sources. These include the scanner’s relay actuation times, the DMM input settling and wiring capacitance. The latter will varies with the type of measurement. For insta nce, when making high value

Ohms measurements the DMM current source level could contribute significant delay due to the c time. For example, with 1,000pf cable capacitance, apacitance charge the source current of the SMX2044 DMM using the 33M

Ω range, is 0.1

µA which translates to 33ms (dt = C*dV/I). It is also recommended to set the appropriate n umber of settling measurements for the DMM (a minimum of 4 is recommended regardless of measurement rate).

4.15.3 Interface Commands and Timing

The sequence requiring the SMX2040 DMM to make triggered measurements generated by the SMX4032 starts with the preparation of the SMX4032. Set the SMX4032 desired configuration, with Trigger Output enabled and positive polarity. Each channel selection will generate a positive pulse with duration equal to the actuation time.

This could be generated by one of the scanning. The SMX2040 must be set up for triggered readings by using the

DMMSetTrigRead() command. In the following VisualBasic® example, the SMX2040 sends readings during the scan. Since it’s on board FIFO is limited to 5 readings, and the DMM must continue to send all readings during the scan, it is important to have a tight loop that reads the measurements fast enough so that no overrun error occurs.

Refer to Figure 4-13 for proper trigger connection.

SCANTriggerOutState(nScan, Enabled, PosEdge) // Set trigger output to Positive edge. nReadings = 100

DMMSetTrigRead(nDmm, 4, nReadings, NegEdge)

// Total number of measurements to take

// Total of 100 readings and 4 settling readings

For I = 0 to nReadings -1 // read values as they come

Next while(DMMReadMeasurement(nDmm, reading) = NO

SCANOpenAllChannels(nScan)

// wait for each reading and store it

// Good idea to open all channels when done

Figure 4-20. Triggered reading process and timing of SM4042 Scanner and an SMX2044 DMMs.

Unlike the previous example, DMMSetBuffTrigRead() is not time critical since the DMM saves all measurements to it’s on-board buffer, which is read after the scan is complete. However, this function is limited to a maximum of 64 readings per scan.

SCANTriggerOutState(nScan, Enabled, PosEdge) nReadings = 50

‘ Set trigger output to Positive edge.

‘ Total number of measurements to take

43 Signametrics

D MMSetBuffTrigRead(nDmm, 4, nReadings, NegEdge) ‘ Use 4 settling readings each

S

While DMMReady(nDmm) = NO

‘ AutoScan

‘ wait for the DMM to indicate completion

W end

For I = 0 to nReadings -1 while(DMMReadBuffer(n Dmm, reading(I))

‘ read values stored in the buffer

‘ Store each reading

Next

SCANOpenAllChannels(nScan)

While SCANReady(nScan) = NO

‘ Good idea to open all channels when done

‘ Since AutoScan is a polled operation,

Wend

There are several SMX2040 family commands to considered for this operation:

DMMSetTrigRead(), DMMSetBuffTrigRead(), DMMReadMeasurement(), DMMReady(),

DMMReadBuffe

r() and DMMReadBufferStr().

Referrin g to figure 4.20, the total time it takes the DMM make a reading must be set to be shorter than t-Delay, for comp letion of the measurem ents prior to th e selection of the next channel.

Signametrics 44

5.0 SMX2040 DMM Windows Interface

5.1 Distribution Files

The main directory of the distribution diskette contains the Microsoft® Windows™ SMX2040 DMM software.

Before installing the DMM or software, read the “Quick Install” page carefully. To install this software, enter the command "A:SET UP" in the "R un Program" menu of the Windows File Manager; or double-click on the

SETUP.EXE file name from the File Explorer Tool Manager window. Most files on this disket te are compressed, and must be installed using the SETUP program.

T he SMX2040 DLL is a protected-mode Microsoft® Windows™ DLL that will control the Signametrics DMM. It is pr ovided with a sample Visual Basic™ front-panel application to demonstrate the DMM and the interface to the

D LL . Check the README.TXT file for more inform ation about the files contained on the diskette. Some important files to note are:

File

SM40CAL.DAT

SM204032.LIB

SM204032.DE

F

SM204032.DLL

SM204032.H

UserDMM.H

Msvbvm50.d

ll

SM2044.vbw

SM2044.frx

SM2044.frm

SM2044.vbp

File

2044glbl.bas

Description

Configuration file containing calibration information for each DMM.

Do not write into this file unless you are performing an external calibration! This file is normally placed at the C:\ root directory by the setup program, and should be left there. It may cont ain calibration records for several DMMs.

The Windows import library. Install in a directory pointed to by your

LIB environment variable.

SMX2040 driver DLL module definition file.

The 32 bi t driver DLL. This should be installed either in your working directory, in the Windows syst em directory, or in a directory on your m installs this file in your Windows system directory (usually C:\WINDOWS\SYSTEM for Win98/95 or

at C:\WINNT\SYSTEM32 for Windows NT).

Driver header file. Contains the definitions of all the DMM’s function prototypes for the DLL, constant definitions, and error codes. Install in a directory pointed to by your INCLUDE environment variable.

Header file contain ing all of the necessary DMM’s function, range, rate definitions to be used with the various measur e and source functions.

Visual Basic run-time interpreter. Usually, install in your

C:\WINDOWS\SYSTEM (or equivalent) directory. If it is not already installed, run Msvbvm50.exe for proper extraction and registration.

Visual Basic project file

Visual Basic binary form file

Visual Basic file with main form

Visual Basic project file

Description

Visual Basic file with all global DMM declarations

45 Signametrics

SM2044.exe

Msvcrt.dll

Windrvr.vxd

Windrvr.sys

Visual Basic DMM control panel executable

System file. Installs in your C:\WINDOWS\SYSTEM directory.

Win98/95 Virtual Device Driver. Installs by ‘setup’ in your

C:\WINDOWS\SYSTEM\VMM32 directory.

Win NT Virtual Device Driver. Installs by ‘setup’ in your

C:\WINNT\SYSTEM32\DRIVERS directory.

Install.doc

Installation instructions in MS Word

5.1.1 The SM40CAL.DAT file

The SM40CAL.DAT file contains calibration information for the specific DMM is it included. It determines th e o verall analog performance for that DMM. You must not alter this file unless you are performing an external calibration of the DMM. This file may contain multiple records for more than one DMM. Each record starts with a header line, followed by calibration data. card_id 10123 type 2044 calibration_date 06/15/1999 ; The identification should match the last digits of the SN . ad ; A/D compensation

72.0 20.0 v dc ; VDC 330mV, 3.3V, 33V, 330V range s. 1 st

entry is Offset the 2 nd

is gain parameters

-3 86 .0 0.99961

-37.

0 .999991

-8 3.

0 0.999795 vac ; VAC 1st line - DC offset.

Subsequent lines: 1 st

entry is Offset the 2

5 .303 ; starting with the 330mV range, and last line is for the 250V range. nd

is gain, 3 rd

freq. comp

0.84

0.0043

1.015461 23

1.0256 23

.

.

0.0 1.031386 0 idc ; IDC 3.3mA to 2.5A ranges. 1 st

entry is offset, 2 nd

is gain parameter

-1450.0 1.00103

-176.0 1.00602

-1450.0 1.00482

-176.0 1.0 ia c ; IAC 3.3mA to 2.5A ranges, offset and gain

1.6 1.02402

0 .0 1.03357

1.69 1.00513

0.0 1.0142

2w-ohm ; Ohms 33, 330, 3.3k,...,330Meg ranges, offset and gain

12700.0 1.002259 ;in the SMX2040, the 1 st

and last lines are placeholders

1256.0

110.0

1.002307

1.002665

0.0 1.006304

0.0 1.003066

0 .0 1 .001848

0 .0 0.995664

0.0 1.00030

The first line identifies the DMM and the calibration date. The "card-id" is stored in ROM on each DMM.

During initi alization the driver reads information from the DMM hardware such as serial number, DMM type, and allocated

I/ O space. Next it reads the corresponding calibration information from the SM40CAL.DAT file and makes sure there is compatibility between the hardware, the calibration rec od and the software. If all is checked OK, it initialize

Signametrics 46

the DMM hardware. DMMInit accepts the name and location of the calibration file. A qualified technician may modify individual entries in the calibration file, then reload them using th e DMMLoadCalFile command.

5.2 Using the SMX2040 Driver Wit h C++ or Similar Software

Install the SM204032.H and UserDMM.H header file in a directory th at will be searched by your C/C++ compiler for header files. This header file is known t o work with Microso ft Visual C++™. To compile using Borland, you will need to convert the SM 204032.DEF an d SM204032.LIB using ImpDef.exe and ImpLib.exe, provided with the co mpiler.. Install SM204032.LIB in a directory that will be searched by the linker for import libraries. The

SMX2040 software must be installed prior to running any executable code. Install the SM204032.DLL in a location where either your program will do a LoadLibrary call to load it, or on the PATH so that W indows will load the

DLL au tomatically.

In using the SMX2040 driver, first call DMMInit to read the ca libration information. Call DMMSetFunction to set the DMM function. The DM M function constants are defined in the UserDMM.H header file, and have names that clearly indicate the fun ction t hey invoke. Use DMMSetRate to set the reading rate defined in the header file.

Two functions are provided to return DMM readings. DMMRead returns the next reading as a scaled doubleprecision (double) re sult, and DMMReadStr returns the next reading as a formatted string ready to be displayed.

M -numb er parameter, which must be set to the value nDmm, which w as returned by

DMMInit() fu nction. F or multiple DMMs this value will be 0,1,2..n. Most functions return an er ror code which can b e retrie ved as a string using

DMM ErrStr().

Multiple Card Operations U nd er Windows

Single .EXE operation

A ccessin g multiple DMMs from a single e xe cutable is the most common w ay for running up to 10 DMMs using the

W indow s DLL. A combination of several SMX 2040s and SMX2044s can be cont rolled, as long as the single .EXE

( Thread) is used to control all of the units. Make sure that prior to issuin g comman ds to any DMM, it is initialized using DMMInit(). The nDmm parameter is passed with each DLL co m mand to define the DMM to be accessed.

Since this configuration utilizes the DLL to service all DMMs, it must handle a single reading or control command o ne at a tim e. For example, when one DMM reads DCV, and another reads Ca pacitan ce, the DLL must finish reading the DCV be fore it will proceed to take a Capacitance reading. Being a relatively slow measurement,

Capacitance will dictate the measurement throughput. For improved performance, one can use the following:

Multiple .EXE operation

By having several copies of SM204032.DLL, and renaming them, y ou can run multiple DMMs with separate e xecutables. For instance, having a copy named SM204032A.DLL i n C:\windows\system (Win98/95), and having two executable files, MultiExe0.exe and MultiExe1.exe, each of the executables will run independently, making calls to the respective DLL. This can provide an execution throughput advantage over the method mentioned abov e.

If using VisualBasic, the MultiExe.exe source code should define nDmm = 0, and MultiExe1.exe should define

n

Dmm = 1. In addition, the first should declare the SM204032.DLL and the second should declare

SM204432.DLL:

MultiExe0.exe VB function declarations:

Declare Function DMMInit Lib "sm204032.dll" (ByVal calFile As String) As Long

Declare Function DMMRead Lib "sm204032.dll" (ByVal nDmm As Long, dResult As Double) As Long

NDmm = 0

MultiExe1.exe VB function declarations:

Declare Function DMMInit Lib "sm20432A.dll" (ByVal calFile As String) As Long

Declare Function DMMRead Lib "sm20432A.dll" (ByVal nDmm As Long, dResult As Double) As Long

NDmm = 1

/* ************************* *********************************************

* Exmp2040.C Exmp2040.EXE

47 Signametrics

*

* A simple Windows .EXE example for demonstrating the SMX2040,44

* DMMs using "C"

* Sets Function to VDC, Range to 33V, rate to 10rps.

* Display five measurements using a Message box.

* **** ******************************************************************

* M ake sure SM204032.lib is included in the libraries. For Microsoft

* Version 4.0 C++ and above, place under 'Source Files' in the

* Workspace, along side with Exmp2040.c

* PROJECT SETTINGS:

*

* /nologo /ML /W3 /GX /O2 /D "WIN32" /D "NDEBUG " /D "_CONSOLE" /D "_MBCS"

* /FR"Release/" /Fp"Release/Exmp2 040.pch" /YX /Fo"Release/" /Fd"Release/" /FD /c

*

* C opy both SM204 032.DLL and SM204032.LIB to the project directory.

*

**** *******************************************************************/

// #d efine WINAPI __stdcall

#inc lude <windows.h>

#inc lude <string.h>

#ifde f _Windows

#define _W INDOWS

#end if

#inc lude "sm204032.h"

#inc lude "UserDMM.h" int m ain(void){ int I, nDmm = 0;

Read[16];

// functions declarations and error codes.

// All functions, range and rate info and function declarations.

// Address first DMM in the system i = DMMInit(nDmm ,"C:\\sm40cal.dat"); if(i<0)

// initialize SMX2044, and read calibration file

MessageBox(0,"Initi alization ERROR !", "Startup SM204032 DLL",MB_OK);

DMMSetFunction(nDm

DMMSetRange(nDmm m,VDC); // Set to DCV function

,_30V); // and to 33V range

// Error

DMMSetRate(nDmm,RAT E_10); strcpy(strMsg,""); for(i=1; i<= 5; i++){

// 60 samples per sec

// take 5 readings

R ead); read strcat(strMsg," ");

}

// reading

// insert space between readings

MessageBox(0,strMsg, "SM204032.DLL Read Resistance & V DC",MB_OK); return

}

// Show readings

5.3

Visual Basic Fr l lication

The Visual Basic front panel application, SM2044.EXE, is an interactiv e control panel for the SMX2040 DMM.

Dur ing loading, which takes a few seconds, it initializes and self calibrates t he hardware before the front panel is displ ayed.

The push buttons l abeled V, I, etc. control the DMM function. As you push a function, the front panel application will sw itch the DMM to the selected ran ge an d function. Autorange mo de is selected by pushing the AutoRange chec k box. The S-Cal t the D MM, leaving the DMM in the sa me state prior to operation. (This is an inte er t from the external calibration, which uses external stan dards and writes to the

SM

40CAL.DAT file. S-Cal is used to co rrect fo r any internal offset a nd gain drifts du e to changes in operating temp erature). frequency and amplitude are shown at the same time. In this mode, the reading rate is slower than indicated. When

per is enabled, the period is shown. The SMX2044 panel has additional capabilitie s, which are disabled if an

SMX2040 is detected.

Signametrics 48

T he source code file GLOBAL.BAS (in the V_BASIC directory of the distribution diskette) contains the function declarations and the various ranges, rates and other parameters, which are required. These definitions are th e d uplicates of the “C” header files required to write Visual Basic applications which interact with the driver DLL, along wi th some global vari ables required for this particular front-panel application.

Basic Simple Application

The following is a simp le panel application for VisualBasic that includes two files, Global.Bas and

Sim P ontains two objects; a Text Box to display the DMM readings, and a ding trigger.

Glo .b

contents:

Option Explicit

' Declare all functions we are going to be using: From SM204032.H file.

Declare Function DMMInit Lib "sm204032.dll" (ByVal nDmm as long, ByVal calFile A s String) As Long

Declare Function DMMSetRate Lib "sm204032.dll" (ByVal nDmm As Long, ByVal nR ate As Long) As Long

Declare Function DMMSetFunction Lib "sm204032.dll" (ByVal nDmm As Long, ByVal nFunc As Long) As Long

Declare Function DMMSetRange Lib "sm204032.dll" (ByVal nDmm As Long, ByVal nRange As Long) As Long

Declare Functi on DMMRead Lib "sm204032.dll" (ByVal nDmm As Long, dResult As Double) As Long

' Definitions from UserDMM.H

' for DMMSetFunction()

Global Const VDCFunc = 0

Global Const VACFunc = 4

Global Const Ohm2Func = 21

Global nDmm as Long

' for DMMSetRange()

Global Const Range0 = 0

Glob al Const Range1 = 1

Glob al Const Range2 = 2

Glob al Const Range3 = 3

'for DMMSetRate(): Rea ding rates

Global Const RATE_5 = 5 '5 rps

Global Const RATE_10 = 10 '10 rps

Global Const RATE_30 = 30

'Glo bal variables

Glob al nDmm As Long ' Globa l store for the DMM number

S impleP anel.frm Form file contents:

Private Sub Form_Load()

Dim i As Long

nDmm = 0

'Fomr_Load allways gets executed first.

‘Set to first DMM in the system

i = DMMInit(nDmm,"C:\sm40cal.dat") 'Initialize and load cal file

i = DMMSetFunction(nDmm, VDCFunc) 'Set DMM to DCV function

i = DMMSetRange(nDmm, Range2) 'Select the 33V range

i = DMMSetRate(nDmm, RATE_10) 'Set measurement rate to 10 rps

End Sub

Private Sub ReadBotton_Click()

Dim i As Long

Dim dReading As Double

i = DMMRead(nDmm, dReading)

TextReading.Text = dReading

End Sub

'Read Botton Click action.

'Any time this botton is pressed

'the DMM takes a reading and displays it.

'Take a reading

'display it in a Text box.

5.4 Windows DLL Default Modes and Parameters

49 Signametrics

A fter initialization, the Windows DLL default modes and parameters on your DMM are set up as follows:

• Autoranging: Off

• Function: DC Volts

• Range: 330V

Relative: Off

• Synchronized Mode: Off

• Measurement rate: 10 rps

• Temperature units are set to

°C

Offset Ohms: Off

AC Caps level: 0.45V Peak.

5.5 Using the S MX2040 DLL with LabWindow s/CVI

®

When using the SMX2040 DLL wi th LabWindows/CVI, y ou should read the LabWin.txt file included with the software diskette.

An example appl ication of SMX2040 DLL calls from LabWindows/CVI ® is shown below. It contains funct ions measur e_ohms() and measure_vdc(), with sample calls to the SMX2040.

NOTE: Although these me asurement functions use LabWindows/CVI® and the LabWindows/CVI(R)

Test Executive, they are no t necessarily coded to LabWindows® instrument driver standards.

/* function: measure_ohms , purpose: measure 2-wire ohms */ int measure_ohms(double OHMreading) { short ret, i;

DMMSetFunction

DMMSetAutoRan

/* to settle auto-ra s (0, OHMS2W); for( i = 0 ; i < 4 ; i+ ge (0, TRUE); nge and function changes ignore three readings */

+ ) ret = DMMReadNorm (0, & OHMreading);

}

/* function: measure_vdc, purpose: measure DC Volts */ int measure_vdc(double Vr eading) { short ret, i;

DMMSetFunction

DMMSetAutoRan

/* to settle auto-ra s for( i = 0 ; i < 4 ; i+

(0, VDC); ge (0, TRUE); nge and function changes ignore three readings */

+ ) ret = DMMReadNorm (0, &Vreading);

}

Signametrics 50

5.6 Windows Command Language

The following section contains detailed de scriptions of each function of the Windows command language. Tho se commands that pe rtain to onl y the SM204 0 are indicated. Most functions return an error code. The code can e ither be retrieved as a st ring usin g DMMErrStri ng function, or looked up in the SM204032.H header file. The

UserDMM.H file contains a ll the pertinen t definitions for the DMM ranges functions etc. The following description for the various functions is based on “C” f unction declarations. Keep in mind that the Window s DLL containing these functions as sumes all int values to b e windows 32bit integers (corresponds to VisualBasi c long type). TRUE is 1 and FALSE i s 0 (which is also differe nt from VisualBasic where True is –1 and False is 0) .

DMMArmAnalogTrigger

SMX20

40 ;

SM X20

44

;

Description

Remarks

#include "sm2 04032.h"

int DMMArmAnalogTrigger(int nDmm, int iSamples, double FAR *dThresh)

This function is usable for VDC, VAC, Ohms, IAC, and IDC. Setup the SMX2040 for analog level trigger operation. Foll owing reception of this command the DMM makes m easure ments continuously, waiting for a value which exceeds the threshold, dThresh.

When this occurs, a trigger is produced with identical processing as in

DMM

ArmTrigger. Threshold crossing sense is determined by the first measurement following the call o f DMMArmAnalogTrigger. If that measurement is lower than the set threshold, dThresh , subsequent measurements greater than dThresh will trigger the

DMM. If the first measurement is greater th an dThresh, subsequent measurements smaller than dThresh will trigger. For exam ple, if dThresh is 2.00000 V and the first reading after arming the D MM is 2.500000 V, then 1.999999 V (or smaller) will trigger the DMM. On the other hand, i f dThresh is 1.000000 V and the first reading after arming the DMM is 0.500000 V, then 1.000001 V (or gre ater) will trigger the DMM. example, in the 330 mV range, dThresh must be within -0.330000 and +0.330000. In the

33 k

Ω, range dThresh must be between 0.0 and 33.0e3.

Following an analog level trigger event, the DMM makes iSamples readings at the set function, range, and reading rate, and stores them in an internal buffer. Autoranging is not allowed when using DMMAnalogTrigger. Between the time the

DMMArmAnalogTrigger is issued and the time the buffer is read, no other com mand should be sent to the DMM. One exception is the DMMDisArmTrigger command.

Use the DMMReady to monitor when the DMM is ready. When ready, you can read up-to iSamples, using DMMReadBuffer or DMMReadBufferStr functions. Once DMMReady returns TRU E, it should not be used again prior to reading the buffer, since it prepares the buffer for reading when it detects a ready con dition.

51 Signametrics

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs ar e numbered starting with zero.

iSamples int The num ber of samples the DMM takes following a trigger pulse.

This number must be between 1 and 64, inclusive.

R

eturn Value

dThresh

double FAR Analog level trigger thresh

Th e retu rn value is one of the following constants. old value

Value Meaning

DMM_OKAY

Ope ration successfully terminated

Negativ e value

Example double

DMMArmAnalogTrigger(0,64,1.5); while( ! DMMReady(0)); for(i=0; i < 64 ; i++)

Buffer[i] = DMMReadBuffer(0);

DMM ArmTrig ger

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Error code.

Arm DMM for external trigger operation.

#include "sm204032.h"

int DMMArmTrigger(int nDmm , int iSamples)

Remarks

Setup the SMX2040 for external hardware trigger operation. Following reception of this command, the DMM enters a wait state. After reception of an external trigger pulse, the

DMM makes iSamples readings at the set function, range, and reading rate; and stores them in an internal buffer. No autoranging is allowed for external trigger operation .

Between th e time the DMMArmTrigger is issued and the time the buffer is read, no other command should be sent to the DMM. One exception is the DMMDisarmTrigger com mand. This function is usable for VDC, VAC, Ohms, IAC and IDC

Use the DMMR eady to monitor when the DMM is ready (following trigger and the reading of iSamples). When ready, you can read up to iSamples, using

DMMReadBuf

fer or DMMReadBufferStr functions. Once DMMReady returns

TRUE, it shoul d not be used again prior to reading the buffer, sinc e it prepares the buffer for reading when it detects a ready condition.

Parameter Type/Description

int Identifies the DMM. DMMs are numbered starting with zero.

nDmm

iSamples

int The number of samples the DMM takes following a trigger pulse.

This numb er must be between 1 and 64, inclusive.

Return Value The return value is one of the following con stants.

Signametrics 52

Value Meaning

DMM_ OKAY

Operation successfull y term inated

Negative Value

Error code.

Exa

Buffer[64];

DMMArmTrigger (0,64); while( ! DMMReady(0)); for(i=0; i < 64 ; i++)

Buffer[i] = DMMReadBuffer(0);

DMMBurstBu ffRead

SMX2040

; SMX2042

; SMX2044 ;

Description

Setup the DMM for Triggered operation.

#include "sm204032.h"

#include "UserDMM.h" int

Remarks Following reception of this command the DMM enters a burst read mode, where it takes

iSettle + 1 readings at the set measurement function, range, and reading rate; and saves the last reading to the on-board buffer. This process repeats for iSamples. No other DM M command should be issued to the DMM until the it completes the operation, and the buffer is read. One exception is the DMMDisarmTrigger command, which terminates the process. No autoranging is allowed in this mode. This function is usable for VDC,

VAC, Ohms, IAC, IDC, and RTD measurements. Measurement rate should be set to

10rps or higher. The total time it takes to complete this process is equal to iSamples * (

iSettle + 1) / (measurement rate).

Use the DMMReady to monitor if the has completed the operation, and is ready. When ready, read up to iSamples, using DMMReadBuffer or DMMReadBufferStr functions .

Once DMMRead y returns TRUE, it should not be used again until the buffer is read, since it clears som e flags in preparation for buffer read ing when it detects a ready con dition.

Parame ter Type/Description

iDmm

int Identifies the DMM. DMMs are numbered starting with zero.

iSettle

int The number of settling measurements prior to read value. Mu st be set between 0 and 250. Recommended value is 4.

iSamples int The nu mber of samples the DMM takes following the same number of trigger pulses. This num ber must be between 1 and 64, inclusive.

Return Value

The return valu e is one of t he following constants.

Value Meaning

DMM_OKAY

Operation successfully terminated

Error code.

Negative Value

Example

Buffer[50];

53 Signametrics

DM MBur stBuffRead(0, 4, 50); // 4 settling readings for each

// measurement, and take 50 readings wh ile( ! DMMReady(0) ); o 50 ; i++)

// wait for completion

// read 64 readings from DMM’s

// on-board b uffer

Buffer[i] = DMMReadBuffer(0);

DMMBurstRead

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Setup the DMM for multiple read ings operation, sending back measurements as they come.

#inc lude "sm2 04032.h"

#inc lude "User DMM.h"

Remarks Set the DMM to take multiple measurements, sendi ng readings back to the computer.

This function is similar to th e DMMSetTrigRead function, with the exception that it does not wait for a hardware trigger to start making measurements. Following reception of this c omman d the DMM enters a burst read mode, where it takes iSettle + 1 readings at the se t measu rement functio n, range, and reading rate; and sends the last reading to the computer. This process repeats for iSamples. Following the issue of this command, and until iSa mpels measur ements are read, it is necessary to read the samples from the DMM using the DMMReadMeasurement command as fast as they become available . This will prevent an Overrun communication error, which is an indication that the ra te at which measurements are read from the bus do not keep up with the DMM transmission.

The DMM has five readings FIFO to lessen this problem. No autoranging is allowed in this mode. This function is usable for VDC, VAC, Ohms, IAC, IDC, and RTD measurements. Measur ement rate should be set to 10rps or higher. The total time it takes to com plete this process is equal to iSamples * ( iSettle + 1) / (measurement rate).

Use the DMMRead Measurement to monitor when reading becomes available, and to read the data. Read as many samples as iSamples to guarantee proper conclusion of this capture process.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered st arting with zero.

iSettle

int The number of settling measurements prior to read value. Must be set between 0 and 250. Recommended value is 4.

Return Value

iSamples

int The number of samples the DMM takes following the sam e number of trigger pulses. This number must be between 1 and 32,000, inclusive.

The return valu e is one of the following constants.

Value Meaning

DMM_OKAY

Operation successfully terminated

Negative Value

Error code.

Reading [250];

DMMBurstRead(0, 10, 250); // settle 10 reads., 250 samples for(i=0; i < 250 ; i++) // read 250 meas. as they come

Signametrics 54

while( ! DMMReadMeasurement(0 , Reading[i]) );

DMMCalibrate

SMX2040 ; SM 2

Descriptio n

Internally calibrates the DMM.

#include "sm204032.h"

Remarks

T his function re-calibrates the DMM, and returns it to the current operating mode.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

The return value is one of the foll owing constants.

Value Meaning

DMM_OKAY

DMM is OK.

Erro r

Negativ e Value

Example

Comments status = DMMCalibrate(0); /* a quick internal cal.*/

DMM CleanRe lay

SMX2040

; SMX2042 ; SMX2044 ;

Des cription

This performs an internal DMM calibration an d is the same as the S-Cal command in the

VB Control Panel. It is not related to the external calibration represented in the

Cle an specified relay.

#include "sm204032.h"

Remarks This function cleans iRelay by vibrating the contact iCycles . This function is useful for removing oxides and other depos its from the relay contacts. DC Current measurements are particularly sensitive to K2 contact resistance and therefore should be cleaned periodically. It is also useful for making sound in computer without a speaker.

Parameter

Type/Description

iRelay

int The relay to clean. 1 for K2, 2 for K2 and 3 for K3.

iCycles

nDmm

int The numer of times the relay contac is shken. 1 to 1000.

int Identifies the DMM. DMMs are numbered starting with zero.

Return Value Integer error code..

Value Meaning

55 Signametrics

DMM_OKAY

Operation su ccessfully completed.

Negativ

e Value Error code

Exa

mple int status = DMMCleanRelay(0, 2, 100); // Shake K2 1000

DMMClearMinMax

SMX2040 ; SMX2042 ; SMX2044 ;

D escription

Clears the Min/Max storag e.

#include "sm204032.h"

Remarks

Return Value

This function clears the Min/Max values, and initiates a new Min/Max accumulation. See

DM

MGetMin for more details.

Param

eter Type/Description

nDmm int Identifies the DMM. DMMs ar e numbered starting with zero.

Integer error co de..

E

xample

Value Meaning

DMM_OKAY

Ope ration succes sfully completed.

Negativ

e Value Error code int status = DMMClearMinMax(0);

DMMClosePCI

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Close the PCI bus for the s pecified DMM. Not for user applications.

#include "sm204032.h"

Remarks

R

eturn Value

This function is limited for servicing the DMM. It has no use in normal DMM operation.

See also DMMOpenPCI() function.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Integer error code.

Value

Meaning

DMM_O KAY

Operation successfully completed.

Signametrics 56

Negative Value

Error code

Example int status = DMMClosePCI(0);

DMMDelay

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Wait for a given time.

#include "sm204032.h"

int DMMDelay(double dTime)

Remarks

Delay een 0.0 and 100.0 seconds.

Parameter Type/Description

R

eturn Value

dTime

double Delay time in seconds.

The return value is one of the following constants.

Value Meaning

DMM_OKAY

N

egative Value

Operation successfully terminated

Error code

Example

DMMDe lay(1.2); /* wait for 1.2 Sec */

DMMDisableTrimDAC

SMX2040 † SMX2042 ; SMX2044 ;

Description

Terminate the operation o f the Trim DAC.

#include "sm204032.h"

Remarks

This function disables the Trim DAC. Since usage of the Trim DAC consumes a lot of the on-b oard microcontroller’s resources it must be turned off with this function when not in use. See DMMSetTrimDAC, DMMSetDCVSource and DMMSetACVSource for more details .

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

Integer error code.

Value

Meaning

DMM_OKAY

Operation successfully completed.

57 Signametrics

Negative Value

Erro r code

Example

DMMDisableTrimDAC(0); // Remove Trim DAC from operation

DMMDisArmTrigger

SM X2040 ; SMX2042 ; SMX2044

;

Description

Abort trigger operation.

Remarks

T his function sends the DMM a trigger termination command. If the DMM is waiting for a trigger, it will exit the wait mode, and be ready for a new operation. I t can be used following an external hardware or analog level trigger arm command

(DMMArmAnalogTrigger, DMMArmTrigger, or DMMTrigger ). It can be used with no limitation.

Parameter Type/Description

nDmm

Return Value

Integer error code

Value

int Identifies the DMM. DMMs are numbered starting with zero.

DMM _OKAY

Negat ive Value

DMMDu tyCycleStr

SMX2040 † SMX2042 ; SMX2044 ;

Error code

Description

Operation successfully completed.

Return percent duty cycle of an AC signal in stri ng format.

#include "sm204032.h"

Remarks

This function is the string version of DMMReadDutyCycle. The measurement result is stored at the location pointed to by lpszReading. See DMMReadDutyCycle for more details.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

lpszRead ing

LPSTR Points to a buffer (at least 16 characters long) to hold t he result.

Return Value

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Valid return.

Signametrics 58

Example

Negative Va

lue

Error code char cBuf[17] ; int status = DMMDutyCycleStr(0, cBuf);

DMMErrString

SMX2040 ; S MX2042 ; SMX2044 ;

Description

Remarks

Return the string describing the error code.

#includ e "sm20 4032.h" int DMMEr rSt

ring(int iErrorCode, LPSTR lpszError, int iBuffLength)

This func tion re turns a strin g containing the error description which corresponds to the

iErrorCo

de. The error string is placed at lpszError.

Parameter Type/Description

iErrorC

ode int Error code.

Return Value

iBuffLength lpszError

int The maximum available length of the string buffer

LPSTR Points to a buffer (at least 16 characters long) to hold the error string.

The return value is the length of the error string or one of the following constants.

Value Meaning

Negative Value

Error code int length = DMMErrString( -3, cBuf, 48);

DMMFrequencyStr

SMX2040 † SMX2042 ; SMX2044 ;

Description

Remarks

Return the next DMM frequency reading, formatted for printing.

#include "sm204032.h"

int DMMFrequencyStr(int nDmm, LPSTR lpszReading)

This function makes frequency measurement and returns the result as a string formatted for printing. The print format is fixed to six digits plus units, e.g., 05.001 Hz. If the

DMM is in autorange, be certain to take an amplitude reading before using this command. It may take several calls to DMMFrequencyStr() to get the measured frequency, because the DMM frequency counter uses a frequency ranging scheme which gets activated only when a frequency or period reading function is received. If the previously measured frequency was 1 Hz and the frequency being measured is 300 kHz

(or vise versa), it might take as many as six calls to DMMFrequencyStr() or any of the other frequency measurement functions, to read the correct frequency. This function is a

Secondary function which requires the DMM to be in either VAC or IAC function and at the appropriate range.

59 Signametrics

Parameter Type/Description

nDmm

int

Identifies the DMM. DMMs are numbered starting with zero.

Return Value

lpszRead ing

LPSTR Points to a buffer (at least 16 characters lo ng) to hold the converted result.

The return value is one of the following constants.

Value Meaning

DMM_ OKAY

Operation successfully completed.

DMM_ CNT_RNG

Frequency counter is over or under range.

Negative Va

lue Error code

7]; int status; st atus = DM MFrequencyStr(0, cBuf);

Signametrics 60

DMMGetACCapsR

SMX2040 † SMX2042 † SMX2044

;

Description Return the resist ance component of the last AC Caps measurement.

#include "sm204032.h"

Remarks This t reading of AC based Capacitance measurement. It perform s all scal ing and conversion required, and returns the result as a

64-bit double-precisi on floatingpoint number in the location pointed to by lpdResult.

Returned resul t is a val ue in ohms. Read about In-Ci rcuit Capacitance Measurements in section 4.8 of this ma nual.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Ret

urn Value

lpdResult

double * Points to the location to hold the resistance value.

The re turn value is one of the following constants.

Value Meaning

DMM_OKAY

DMM initialized successfully.

Negative Value

OVER_RNG

Error code

Over range occurred, implying a very high parallel resistance value.

Example double d; int status; stat us = DM MGetACCapsR(0, &d);

DMMGetBusInfo

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Remarks

Returns the PCI Bus and Sl ot numbers for the selected DMM.

int DMMGetBusInfo(int nDmm, int *bus, int *slot)

This function reads the PCI bus and slot numbers of the selected DMM. It provides means to relate the physical card locat ion to the nDmm value by detecting the location of a DMM in the PCI system tree. This function actually scans the hardware rather then look up the information in the registry.

61 Signametrics

Return Value

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

bus slot

int *

int * A pointer to a

15)

a pointer to integer at which the bus number is stored (0 to 255) n integer where the slot number is stored (0 to

The return value is one of the following constants.

Value Meaning

Operation was successful.

DMM_OKAY

Negative number Error code

Example int bus, slot; // Find on which bus, and slot the DMM is at

&bus, &slot); // DMM#3

DMMGetCalDate

S MX2040 ; SMX2042 ; SMX2044 ;

Description

Remarks

Retu rn the calibration date string from the DMM.

int DMMGetCalDate(int nDmm, LPSTR lpszCalDate)

This function reads the cal ibration date string from the structure.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

lpszCalD ate

LPSTR Points to a b uffer (at least 16 characters long) to hold the cal date string.

R

eturn Value

The return value is one of the following constants.

Value Meaning any positive number

Negativ

e number

Length of the date string

Error code int status; status = DMMGetCalDate(0, cBuf);

DMMGet dB

SMX2040 ; SM 2

Descriptio n

Get dB deviation from the reading at the time relative was activated.

#includ e "sm204032.h"

Signametrics 62

Remarks This function returns a dou ble floating value that is the dB deviation relative to the re ading made just before the relative function was activated. This function is useful in determining measurement errors in dB. It can be used fo r bandwidth measurements or

DC evaluation.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

lpdDev

double FAR * Pointer where the dB value is to be saved.

Integer error code..

Value Meaning

DMM_OKAY

Operation successfully completed.

Negative Value Error code

Example double FAR dB; int status = DMMGetdB(0, &dB);

DMMGetdBStr

SM X2040 ; SMX2044 ;

Description

Get dB deviation from the reading at the time relative was activated.

# include "sm204032.h"

Remarks This function is the same as the DMMGetdB(), with the exception that it returns a string.

See DMMGetdB() for more details.

Parameter Type/Description

nDmm

lpszDB

int Identifies the DMM. DMMs are numbered starting with zero.

LPCSTR Points to a buffer (at least 16 characters long) to hold the resu lt. The return value will consist of a leading sign a floating-point, and a ‘dB’ units specifier

Return Value

Integer string length if successful, or an error code..

Value

Meaning

Negative Value Error code

Example

char cBuf[32]; int strLength = DMMGetdBStr(0, cBuf);

DMMGetCJTemp

SMX2040 ; SMX2042 ; SMX2044 ;

63 Signametrics

Des cription

Retrieve the currently set cold junction temperature.

#include "sm20403 2.h"

R

emarks Get the currenly set cold ju function. ncion temperature. For more details see DMMSetCJTemp()

Return Value

Parame ter Type/Description

nDmm lpdTemp

int Identifies the DMM. DMMs are numbered starting with zero.

double * Points to the location to hold the temperature.

The return valu e is one of the following constants.

Value Meaning

DMM_O KAY

Operation successfully terminated

Example

Negativ e Value

Error code.

DMMGetCJTemp(0, &temp);

DMMGetDeviation

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Get percent deviation from the reading at the time relative was activated.

#include "s m204032.h"

Remarks

This function returns a d ouble floating value that is the percent deviation relative to the reading made just before the relative functio n w as activated. T his func tion is useful in quantifying measurement errors. It can be used for ba n dwidth measur ements or DC evaluation, or percent variation of a device under test over t emperature.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

lpdDev

double FAR * Poi nter where the deviation value is to be saved.

Return Value

Integer error co de..

Value

Meaning

DMM_OKAY

Operation successfully completed.

Negative Value

Error code

Example double FAR error; int status = DMMGetDeviation(0, &error);

Signametrics 64

DMMGetDeviatStr

SMX2040 ; S MX2042 ; SM X2044 ;

Description

Get perc ent deviat ion from the reading at the time relative was activated.

#include "sm204032.h"

Rem

arks

This fun ction is the same as the DMMGetDeviation(), with the exception that it returns a string. See DMM GetDeviation() for more details.

Parame ter Type/Description

nDmm int Identifies th e D MM. DMMs are numbered sta rting with zero.

lpszDev

LPCSTR Points to a buffer (at least 16 characters long) to hold the result. The return valu e will consist of a leading sign a floating-point, and a % units specifier

Return Value

Integer string length if successful, or an error code.

Value

Meaning

Negative Value Error code int strLength = DMMGetDeviatStr(0, cBuf);

DMMGetFuncRange

SMX2040 ; S MX2042 ; SMX 2044 ;

Description

Get DMM range code.

#include "sm204032.h"

#include

Remarks

This function returns the combined DMM function/range code. See UserDMM.h for the complete set of codes.

Parame ter Type/Description

nDmm int Identifies the D MM. DMMs are numbered starting with zero.

Return Value Integer value corresponding to the currently set DMM function/range , or an error code.

The following are a few examples of the returned value.

Value Meaning

65 Signametrics

Positive value

Negative Value

See UserDM M.h for function/range codes.

Erro r code

Example

DMMGetFunction

SMX2040 ; SMX2042 ; SMX2044 ;

Description

if(DMMGetFnRange == VDC_300mV) p rintf("Lowest VDC range selected");

Get DMM function code.

#include "sm204032.h"

Remarks This function returns the DMM function code.

Return Value

Parameter Type/Description

nDmm

int Identifies the DMM nuber. Zero being the first.

Integer value corresponding to the current function, or an error code.

Value Meaning

Positive value

Negative Value

See UserDMM.h for function codes.

Error code

Example if(DMMGetFunc tion == VDC) printf("VDC Function selected");

DMMG etGrdV er

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Get DMM firmware version.

#include "sm204032.h"

Remarks

)

Thi s function ret urns the DMM firm ware version of the on-board controller.

R

eturn Value

Parameter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

Integer value. The return value is the version value or an error code.

Value

Meaning

Signametrics 66

Positive Value

Versi on

Negative

Value Error code

Ex

ample firmwarever = DMMGetGrdVer(0);

DMMGetHwVer

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Get the hardware version o f the DMM.

#include "sm204032.h"

Remarks

This function returns the DMM hardware version. A returned value of 0 corresponds to

Rev_, 1 corresponds to Rev_A, 2 to Rev_B etc.

Return Value

Parameter Type/Description

nDmm

int Identifies th e DMM. DMMs are numbered starting with zero.

DMM hardwar e code or an error code.

Val

ue Meaning

Positive value

Hardware version code

Negative

Value Error code

Example int HWVer = DMMGetHwVer(0);

DMMGe tID

SMX2040 ; S MX2042 ; SMX 2044 ;

Descriptio n

Remarks

Get DMM ID code.

#include "sm204032.h"

int DMMGetID(int nDmm)

This function returns the DMM identification code. Each DMM has a unique ID code that must match the calibration file card_ID field in SM40CAL.DAT.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are num bered starting with zero.

Return Value Integer value card ID code (serial number) or an error code.

Value Meaning

67 Signametrics

DMM_E_DMM

Invalid DMM number.

Example int id = DM MGetID(0);

DMMGetManDate

SMX2040 ; SMX2042 ; SMX2 044 ;

Description

R

emarks

Get Ma nu facturing date stamp from the DMM hardware

"

int DMMGetManDate(int nDmm, int *month, int *day, in t *year)

This function returns the DMM manufacturing date which is read from the hardware.

The month, day and year are returned as integers. This is used to track the DMM to a specific manufactur ing date.

Paramet er Type/Description

nDmm int Identi with zero.

fies the DMM. DMMs are numbered starting

int * A pointer to an integer where the m onth is stored

month day

year

int * A pointer to an integer where the day is stored

int * A pointer to an integer where the year is stored

Return Value Integer error code or.

Value

Meaning

DMM_OKAY

Operation was successful.

DMM_E

_DMM Invalid DMM number.

Example int month, day, year, status status = DMMGetManDate(0, &month, &day, &year);

DMMGe tMax

SMX2040 ; SMX2044 ;

Description

Get Maximum reading history.

#include "sm204032.h"

Remarks

This function returns a double f loating value that is the maximum (of the Min/Max function) value since either a funct ion change, range change or call to the

DMMClearMinMax func tion was made. This is only applicable to Primary read functions (those that are read usi ng DMMRead, DMMReadStr or DMMReadNorm).

This value is updated every time one of those functions is used.

Parameter Type/Description

Signametrics 68

Return Value

nDmm

lpdMax

int Identifies the DMM. DMMs are numbered starting with zero.

double FAR * Pointer where the Max value is to be saved.

Integer error code..

Value

Meaning

DMM_OKAY

Operation successfully completed.

Negative Value Error code

Example double FAR Mx; int status = DMMGetMax(0, &Mx);

DMMGe tMaxStr

SMX2040 ; SM 2

Descriptio

n Returns the maximum as a formatted string.

#include "sm204032.h"

DMMGetMaxStr

(int nDmm, LPSTR lpszReading)

Remarks

This function is the string version of DMMGetMax. It returns the result as a string formatted for printing. The print format is de termined by the range and function. See

D

MMGetMax for more details.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

lpszRead ing

LPSTR Points to a buffer (at least 16 characters long) to hold the result.

Return Value

The return valu e is one of the followi ng constants, or the string length is OK.

Value Meaning

DMM_OKAY

Negative Value

Valid return.

Error code int status = DMMGetMaxStr(0, cBuf);

DMMGetMin

SMX2040 ; SM X2042 ; SMX 2044

;

Description

Get Minimum reading history.

#inc lude "sm204032.h"

69 Signametrics

Remarks

This function returns a d ouble floating value that is the minimum (of the Min/Max fu nction) value since either a function change, range change or a call to the

DMMClearMinMax() fu nction was made. This is only applicable to Primary read functions (those that are rea d using DMMRead, DMMReadStr or DMMReadNorm).

This value is updated every time one of those functions is used.

Parameter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

lpdMax

double FAR * Pointer where the Min value is to be saved.

Integer error cod e..

Value

Meaning

DMM_OKAY

Opera tion succes sfully completed.

Negative Value r

Example double FAR M in; int statu s = DMMGetMin(0, &Min);

DMMGetMinS tr

SMX2040 ; SMX2042 ; SMX2044 ;

Description Returns the minimu m as a formatted string.

#include "sm204032.h"

DMMGetMinStr(int nDmm, LPSTR lpszReading)

Remarks

This function is the string version of DMMGetMin. It r eturns the result as a string formatted for printing. The print format is determined by the range and funct ion. See

DMMGetMin for more details.

Parameter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

lpszReading

LPSTR Points to a buffer (at least 16 characters long) to hold the result.

Return Value

The return value i s one of t he following constants, or the string length is OK.

Value Meaning

DMM_OKAY

Valid return.

Negativ

e Value Error code

E xample

int statu s = DMMGetMinStr(0, cBuf);

DMMGetRange

SMX2040 ; SMX2042 ; SMX2044 ;

Signametrics 70

D escription

Remarks

Get DMM range code.

#include "sm204032.h"

#include "UserDMM.h"

int DMMGetRange(int nDmm)

This function re turns the DMM rang e code.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

Integer value corresponding to the currently set DMM range, or an error code.

Value Meaning

Zero or positive value

Range; zero being the lowest

Negative Value Error code if(DMMGetRange == 0) printf("Lowest range selected");

DMMGetRate

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Get DMM reading rate

#include "sm204032.h"

int

le FAR *lpdRate)

Remarks

This function returns a double floating rate in readings per secon d.

Parameter Type/Description

nDmm

i

nt Identifies the DMM. DMMs are numbered starting with zero.

lpdRate

double FAR * Poin ter where the rate is saved.

Return Value

Integer value ver sion code o r an error code.

Value Meaning

Negative Value E rror code

Example

int status; double FAR ra te; status = DMMGetRate(0, &rate);

SMX2040 † SMX2042 † SMX2044 ;

D escription

Get the currently set ACV Source frequency.

#include "sm204032.h"

71 Signametrics

Remarks

Return Value

This function returns a double floating value that is the currently set ACV source frequency of the SMX2044. It can be used to display or verify the default frequency of the stimulus for the various Inductance measurement ranges.

Parameter Type/Description

nDmm

lpdFreq

int Identifies the DMM. DMMs are numbered starting with zero.

double FAR * Pointer where the frequency value is to be saved.

Integer error code..

Value Meaning

DMM_OKAY

Operation successfully completed.

Negative Value Error code

Example dou ble FAR f; int status = DMMGetSourceFreq(0, &f);

DMMG etTCTy pe

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Get the themocouple type currently selected.

#include "UserDMM.h"

Remarks

Return Value

This function returns the Themocouple type currently selected.

Parameter Type/Description

nDmm

int

Identifies the DMM. DMMs are numbered starting with zero.

DMM type Integer or an error code.

Value Meaning

Btype to TType

Type of thermocup le as specified in UserDMM.h file

Negative Value Error code

Exa

mple int TCtype = DMMGetTCType(0);

DMMGetType

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Get the type of the DMM.

#include "sm204032.h"

Signametrics 72

Remarks

This function return s the DMM type.

Parame ter Type/Description

Return Va

lue

nDmm int Identifies the DMM. DM Ms are numbered starting with zero.

DMM type Integer or an error code.

Value

Meaning

2040

SMX204 0 is at nDmm slot

2042

2044

SMX2042 is at nD mm slot

SMX2044 is at nDmm slot

Negative Val

ue Error code

Example int type = DM MGetType(0);

DMMGetVe r

SMX2040 ; SMX2044 ;

Description

Get DM M softwa re driver version.

#include "sm204 032.h"

Re

marks This function returns the DMM software driver version, which is a double floating value.

Parameter Type/Description

Return Value

nDmm

lpfResul

t

Integer error code.

int Identifies the D MM. DMMs are numbered starting with zero.

double FAR *

Pointer to the location which holds the version.

Value

Meaning

Negative Value Error code

Example int status; double ver; status = DMMGetVer(0, &ver);

DMMInit

SMX2040 ; SMX2042 ; SMX2044 ;

73 Signametrics

Description

Remarks

Initialize a DMM.

#include "sm2 04032.h"

int DMMInit(i nt nDmm, LPCSTR lpszCal)

This function m ust be the first function to be execut ed. It opens the driver for the specified DMM. The first DMM being 0, the second 1, etc... It also initializes the DMM hardware and d oes extensive self test to th e DMM hardware. It then initializes the software and reads the appropriate calibration record for the respective DMM from the file specified by lpszCal.

Parameter Type/Description

nDmm

int

Identifies the DMM. DMMs are numbered starting with zero.

lpszCal

Return Value

LPCSTR Po ints to the name of the file containing the calibration constants for th e DMM. Calibration information is normally read from the file n amed SM40CAL.DAT located in the current directory.

The return value is one of the followi ng constants.

Value Meaning

DMM_ OKAY

DMM initialized successfully.

Negative Val

ue Error code

Example

int i = DMMInit(0,"C:\SM40CAL.dat");// Initialize 1st DMM

DMMIsAutoRange

SMX2040 ; SMX2042 ; SMX2044

;

Description

Get the status o f the autorange flag.

#include "sm2 04032.h"

DMM IsAu

toRange(int nDmm)

Remarks

This function return s the DMM autorange flag state.

Parame ter Type/Description

nDmm int Identifies th e DMM. DMMs are numbered starting with zero.

Signametrics 74

Return Value

TRUE, FALSE or an error code.

Value Meaning

TRUE

A utoranging mode is selecte d.

A utoranging mode is not selected.

FALSE

DMM_E_DMM I nvalid DMM number.

Example int autorange = DMMIsAutoR ange(0);

DMMIsInitialized

SMX2040 ; SMX2042 ; SMX2044 ;

Description

G et the status of the DMM.

#include "sm204032.h"

Remarks

Return Value

This function returns the status of the DMM. If TRUE, the DMM has been initialized a nd is active. If FALSE the DMM is not initialized and should not be addressed. This function is used for maintenance and is not needed under normal operation.

Parame ter Type/Description

nDmm int Identifies the D MM. DMMs are numbered starting with zero.

TRUE, FALSE o r an error code.

Value Meaning

TRUE

DMM is initialized and active.

FALSE

DMM is not initialized.

DMM_E_DMM Invalid DMM number.

Example

int active = DMMIsInitialzied(0);

DMM IsRelative

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Get the status of the Relative flag.

#include "sm204032.h"

Remarks

This function returns the DMM Relative flag state.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

75 Signametrics

R

eturn Value

Integer TRUE, FALSE or an error code.

Value Meaning

TRUE

Relative mode is selected.

Relative mode is not selected.

FALSE

Negative Value Error code

Example int rel = DMMIsRelative(0);

DMMLoadCalFile

SMX2040 ; SM

;

Description

Reload calibratio n record from file.

#include "sm20403 2.h" int DMML oadCalFil

e(int nDmm, LPCSTR lpszCal)

Remarks This fun cti on is provides the capability to reload the calibration record. This is useful in making limited calibration adjustments to the DMM. By having a copy of the original

AL.DAT’ open with an editor, and modifying calibration entries, then reloading it using DMMLoadCalFile, one can instantly verify the corrections made. Make sure the ‘SM40CAL.D AT’ file itself is not altered since that will void the calibration.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are n umbered starting with zero.

lpszCal

Return Value

LPCSTR

constants

Points to the name of the file containing the calibration for the DMM.

The return value is one of the following co nstants.

Value Meaning

DMM_O KAY

Cal record loaded successfully.

Negativ e Value

Error code

Example

/* Lo ad a modified copy of the original calibration file to verify correction made to a specific en try */ int i = DMMLoadCalFile(0, "C:\CAL_A.dat");

Signametrics 76

DMMOpenPCI

S MX2040 ; SMX2042 ; SMX2044 ;

D escription

Open the PCI bus for the specified DMM. Not for user application.

#include "sm20403 2.h"

Remarks

penPCI(int

This fun cti on is limited for servicing the DMM . It has no use in normal DMM operation..

See also DMMClosePCI() function.

Parame ter Type/Description

Return Value

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

Integer error code.

Value

Meaning

DMM_O KAY

Operation succ essfully completed.

Negative Value

Error code

Example int status = DMMOpenPCI(0);

DMMOpenCal

ACCaps

SMX2040 † SMX2042

† SMX2044 ;

Description

Calibrate the AC based in circuit capacitance function.

#include "sm204032.h"

i DMMOpenCalACCapsl

(int nDmm)

Remarks This function characterizes the selected ra nge of the AC Capacitance measurement path and source, whic h is required prior to making measurements. For better accuracy it should be perform ed frequently. The Open Terminal calibration should be performed with the test leads c onnected and open. This function characterizes the stimulus source at the specific frequen cy associated with the selected range. It takes about fifteen seconds to complete the process. Make sure to perform this operation for each range you intend to use.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

77 Signametrics

Return Value Integer error co de.

Value Meaning

DMM_OKAY

Ope ration successfully completed.

Negativ

e Value Error code

Example int status = DMMOpenCalACCaps(0);

DMMOpenTerminalCal

SMX2040 † SM X2042 † SMX 2044

;

Description

Calibrate the Inductance measurement function with open terminal s.

#include "sm204032.h"

DMMOpenTerminalCal(int nDmm)

Remarks

This function characterizes the Inductance measurement path and source, which is required prior to making inductance measurements. It should be performed within one hour, before using the inductance measurements. For better accuracy it should be performed more frequently. The Open Terminal calibration should be performed with the test leads open. The DMMOpenTerminalCal sweeps the inductance stimulus source across the full bandwidth, and makes measurements at several points. It takes about twenty seconds to complete the process. For a complete characterization of the

Inductance measurement system it is also necessary to perform the inductance zero operation with the inductance range and frequency selected, using the Relative function and with the probes shorted.

Parameter Type/Description

Return Value

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

Integer error code.

Value Meaning

DMM_OKAY

Operation successfully completed.

Negative Value Error code

Example

int status = DMMOpenterminalCal(0);

DMMPeriodStr

SMX2040 † SMX2042 ; SMX2044 ;

Description Return the next DMM period reading, formatted for printing.

#include "sm204032.h"

int DMMPeriodStr(int nDmm, LPSTR lpszReading)

Signametrics 78

R

emarks

This function makes a period measurement and returns the result as a string formatted for printin g. The print format is fixed to five digits plus units, e.g., 150.01 ms. See

DMMFrequencyS

tr() for more details.

Parame ter Type/Description

nDmm int Identi fies the DMM. DMMs are numbered starting with zero.

Return Value

lpszReading

LPSTR Points to a buffer (at least 16 charac ters long) to hold the converted result. The return value will consis t of a leading sign, a floating-point value in exponential notation, and a units specifier.

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Operation successfu lly terminated

Negative Val

DMM_CN ue

T_RNG

Error code

Period measurement H/W is over or under range. int status; status = DMMPeriodStr(0, cBuf);

79 Signametrics

DMMPol ledRead

SMX2040 ; SMX2042 ; SMX2044

;

Description

Remarks

i

Tests the DMM for ready status, and returns the next floating-point r eading.

#include "sm2 04032.h"

DMMP olledR

ead polls the DMM for readiness. If the DMM is not ready it will return

FALSE

. If the DMM is ready with a new reading it will return TRUE , and the reading will be p laced a t the location pointed to by lpdResult. See DMMPolledReadCmd for more det ails. D o not use DM MReady to check for readiness since it will cause communication failure.

Parameter Type/Description

nDmm int Id entifies the DMM. DMMs are numbered starting with zero.

lpdResul t

double FAR * Points to the location to hold the next reading.

Return Value

The return value is one of the following constants.

Value Meaning

FALSE

TRUE

Negative Value

DMM is not ready

DMM is ready, and reading is placed at lpdResult

Error code

Example double read; if( DMMPoll edRead(0, &d)) fprintf(“%9.4f\n”,d);

DMMPolledReadCmd

SMX2040 ; SMX2042 ;SMX2044 ;

Description

R

emarks

Send DMM Polled Read com mand.

#include "sm204032.h"

olledReadCmd int nDmm )

If the DMM is not bus y with a prior Polled read process, this function will trigger the

DMM to execute a single read command. The DMM must be set to a specific range and one of the following functions to use the polled read command: VDC, VAC, IDC , IAC,

2-wire, 4-wire, 6-wire, or RTD function. Composite functions such as Capacitanc e,

Inductance, Peak-to-Peak etc. are not capable of polled read operation. Measurement rate must be 10 rps or higher. If FALSE is returned, the DMM is busy processing a prior polled read. A DM M_OKAY indicates the DMM accepted the read command and entered the busy st ate. The DMM remains busy until it is ready with the next reading.

This function is useful where it is necessary to conserve CPU time and make the DMM a polled device. Use DMMPolledRead or DMMPolledReadStr to test for readiness and read measurement. Do not use DMMReady to check for readiness since it will cause communication failure.

Signametrics 80

Return Value

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

DMM_OKAY if command accepted, else FALSE or an error code.

Value Meaning

FALSE

DMM is busy and can’t execute a polled read comm and.

DMM_OKA Y

Operation successfu l. DMM entered busy state

Negativ

e Value

Error code

Example

in t status = DMMPolledReadCmd(0);

DMMPo lledRe adStr

SMX2040 ; SMX2042 ; SMX2044 ;

Description If DMM is ready , return the next reading from the DMM formatted for printing.

#include "sm204 032.h"

DMMPo lledR

eadStr(int nDmm, LPSTR lpszR eading)

Remarks This function is the string version of DMMPolledRead. See DMMPolledRead for more details.

Parame ter Type/Description

Return Value

nDmm

lpszReading

int Identifies the DMM. DMMs are numbered starting with zero.

LPSTR Points to a buffer (at least 16 characters long) to hold the converted result. The return value will consist of a leading sign , a floating-poi nt value in exponential notation, and a units specifier.

The return value is one of the following constants, or the stri ng length is OK.

Value Meaning

FALSE

DMM is not ready

TRUE

DMM is ready, and reading is placed at lpszReading

Negative Va lue

Erro r code

Example

char strMsg [32]; if(DMMPolledReadStr(0, strMsg)) MessageBox(0,strMsg,

"S MX2044",M B_OK); // display readings;

DMMRe ad

SMX2040 ; SMX2042 ; SMX2044

;

81 Signametrics

Description

Return the next floating-point reading from t he DMM.

#include "sm204032.h"

R em

arks

DMMRead

reads the next result from the DMM, performs all scaling and conversion required, an d returns the result as a 64-bit double-precision floating-point number in the location pointed to by lpdResult. It can read all the Primary functions (those that can be selected using DMMSetFunction() and DMMSetFuncRange() )

Parameter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

lpdResult

double FAR * Points to the location to hold the next reading.

The return value is one of the following constants.

Value Meaning

DMM initialized successfully.

DMM_OKAY

Negative Value

Error code

Example

DMM_E_RANGE

DMM over range error occurred. double d; int status; status = DMMRead(0, &d);

DMMRea dBuffer

Description

Rem

arks

Return the next double floating-point reading from the DMM internal buffer.

#include "sm204032.h"

int DMMReadBuffer(int nDmm, double FAR *lpdResult)

Read the n ext measurement from the DMM internal buffer, pointed to by an internal buffer pointer, and increment the pointer. Store the measurement as a 64-bit doubleprecision floating-point number in the location pointed to by lpdResult. See

DMMArmTrigger() functions for more detail.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are num bered starting with zero.

lpdResult

double FAR * Points to the location which holds the frequency.

Return Value The return value is one of the following constants.

Value Meaning

Operation successfully completed.

DMM_OKAY

Negative Value

Error Code

Signametrics 82

status;

DMMArmTrigger(0,10); while( ! DMMReady(0));

// Set up for 10 triggered samples for(i=0; i < 10 ; i++) status = DMMReadBuffer(0, &Buffer[i]);

DMMReadBuf ferStr

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Remarks

Return the next reading, formatted for printing.

#include "s m204032.h" int DMMRead

BufferStr(int nDmm , , LPSTR lpszReading)

The same as DM MReadBuffer() except the reading is formatted as a string with un its.

Measurements are stored as a null terminated string at the location pointed to by

lp

szReading.

Parame ter Type/Description

Return Value

nDmm

lpszReading

int Identifies the DMM. DMMs are numbered starting with zero.

LPSTR Points to the location which holds the formatted reading string.

The return value is one of the following constants.

Value Meaning

Operation successfully completed.

DMM_OKAY

Negative Value

Erro r code

DMMArmTrigger(0,1) ; while( !DMMReady(0 ));

// take a single triggered sample

DMM ReadCJT emp

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Read cold junction temperature for thermocouple measurement.

#include "sm204032.h"

nDmm

83 Signametrics

Remarks

Read the cold juncion temperature sensor for su bsequent thrermocouple measurements. When measuring temperature using thermocouples it is necessary to establish a reference or cold junction temperaturem. This is the temperature at which the them ocouple wires are connected to the DMM or to the switching card’s c ooper wires. One way to do this is by m easuring the cold junction sensor using th is func tion. DMM ReadCJTemp() function reads the sensor output voltage (0 to + /-3.3V), an d converts it to cold junction temperature using the built in equation Temp = b + (Vcjs – a)/m. The default values of a, b and m are designed specifically for the temperarute sensor of the SM40T terminal block.

The value o f the cold junction temperature is saved internally for subsequent thermocouple mea surements as well as return at the location pointed to by lpdTemp.

Parame ter Type/Description

nDmm

int Identifies th e DMM. DMMs are numbered starting with zero.

lpdTemp

double * Points to the location to hold the tem perature.

Return Va

lue

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Negative Val ue

Operation successfu lly terminated

Error code.

Example

DMMReadCJT emp(0, &temp);

DMMReadCrestFactor

SMX2040 † SMX2042 ; SMX2044

;

Description

Rem

arks

Return A CV sig nal’s Crest Factor.

#include "sm2 04032.h"

int DMMReadCrestFactor(int nDmm, double FAR *lpdResult)

This is a Seco ndary function and the DMM must be in ACV measurement function, and a valid range must b e set. A double-precision floating-point Crest Factor is stored in the location pointed to by lpdResult. This measurement is a composite function, utilizing several sub functions, and could take over 10 seconds to perform. See the Crest Factor measurement section of the manual for more detail.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered st arting with zero.

lpdResult

double FAR * Points to the location to hold the Crest Factor.

Signametrics 84

Return Va

lue

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Operation successfu lly completed.

Negative Val

ue

Error code

Example

double C F; int st atus = DMMReadCrestFactor(0, &CF);

DMMReadDutyCycle

SMX2040 † SMX2042 ; SMX2044

;

Description Return p ercent duty cycle of ACV signal.

#include "sm2 04032.h"

int DMMReadDutyCycle(int nDmm, double FAR *lpdDcy)

Remarks This is a Sec

on

dary function and the DMM must be in AC measurement function, and a valid range m us t be set. It returns percent duty cycle of the signal. It is stored as double-precision floating-point numbers in the location pointed to by lpdDcy. The measured duty cycle is effected by the setting of the Thre shold DAC.

Parameter Type/Description

nDmm

int

Identifies the DMM. DMMs are numbered starting with zero.

Return Value

lpdDcy

double FAR * Points to the location which holds the duty cycle.

T he return value is one of the following constants.

Value Meaning

DMM_OKAY

Operation successfully completed.

Negativ e Value

Error code

Example

double dcy; int state; state = DMMReadDutyCycle(0, &dcy);

DMMReadFrequency

SMX2040 † SMX2042 ; SMX2044

;

Description Return t he next double floating-point frequency reading from the DMM.

#include "sm204032.h"

int DMMReadFrequency(int nDmm, double FAR *lpdResult)

85 Signametrics

Rem

arks

If frequency counter is not engaged, select it. Make a single frequency measurement, and store the result as a 64-bi t double-precision floating-point number in the location pointed to by lpdRe sult. See DMMFrequencyStr() for more details.

Parame ter Type/Description

nDmm int Identi fies the DMM. DMMs are numbered starting with zero.

Return Va

lue

lpdResul t

double FAR * Points to the location to hold the freq

The return value is one of the following constants. uency.

Value Meaning

DMM_OKAY

Operation successfu lly completed.

DMM_ E_INIT

DMM is uninitialized. Must be initialize prior to using any function .

Invalid DMM number.

DMM_E_

DMM

DMM_C NT_RNG

Frequency counter is over or under range. int status = DMMReadFrequency(0, &d);

DMMRea dFrequenc ySt r

SMX2040 † SMX2042 ; SMX2044 ;

Description

Remarks

Return the next string containing frequency reading from the DMM.

#include "sm204032.h" int DMMReadFr

equencyStr(int nDmm, LPSTR lpszFrequency)

This is the string version of DMMReadFrequency(). It returnes a form ated string containing the measured frequency. For more details read about

DMMReqadFrequency()

.

Parameter Type/Description

Return Value

nDmm

lpszFreq uency

int Identifies the DMM. DMMs are numbered starting with zero.

LPSTR Points to the location which holds the formatted reading string. Allow minimum of 64.

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Op eration successfully co mpleted.

Negative val ue

Er ror code int status = DMMReadFrequencyStr(0, buffer);

Signametrics 86

DMMReadInductorQ

SMX2040 † SMX2042 † SMX2044 ;

Description

Remarks

Return inductor’s Q value.

#include "sm2040 32.h" int D MMReadIn

ductorQ(int nDmm, double FAR *lpdResult)

This is a Seconda ry function and the DMM must be in the Inductance measurement function, and a val id inductance val ue must have been read prior to using this function.

Resulting Q is stor ed as double -precision floating-point number in the location pointed to by lpdResult.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

lpdResult

double FAR * Points to the location to hold the inductor’s Q.

Return Value

The return value is one of t he following constants.

Value Meaning

DMM_

Negativ

OKAY

e Value

Operation successfully completed.

Error code int status = DMMReadInductorQ(0, &Q);

DMMReadMeasurement

SMX2040 ; SM X2044 ;

Description

Return a readin g which is the result of DMMSetTrigRead operation.

#i nclude "sm2 04032.h"

Remarks

int DMMReadMeasurement(int nDmm, double F AR *lpdRead)

This measurem ent reading function is designed to read triggered measurements from the

DMM. It is a fast reading function. It returns FALSE while no new reading is ready. If a reading is ready , TRUE is returned, and the result in the form of a 64-bit doubleprecision floating-poi nt number is placed at the location pointed to by lpdRead.The returned value i s in base uni ts. That is, it will returns 0.3 for a 300mV input and 1e6 for

1.0 Mohm measurement. This function is designed to read bursting measurements form the DMM, resulting from DMMSetTrigRead and DMMBurstRead operations.

Parameter Type/Description

nDmm

lpdRead

int Identifies the DMM. DMMs are numbered starting with zero.

double FAR *

Pointer to a location where the reading is saved.

Return Value Integer value version code or an error code.

87 Signametrics

Value Meaning

TRUE

Measurement was read into *lpdRead

FALSE

No measurement is available

Communication timeout. No reading available within 9s.

TIMEOU T

OVERR UN

Communication overrun. C PU did not keep up with DMM transmission.

Other N egative Value

Error code .

Example

R eadin g[150];

DMMBurstRead(0, 4, 150); // 4 settel., 150 samples for(i=0 ; i < 150 ; i++) // read 150 measurements while( DMMReadMeasurement(0 , Reading[i]) == FALSE );

// wa it for a ll measur ements to be ready, and read them.

DMM ReadMed ian

SMX2040 † SMX2042

; SMX2044 ;

Des

cription

Remarks

Return ACV sign al’s Median value.

#include "sm204032.h"

int DMMReadMedian(int nDmm, double FAR *lpdResult)

This is a Secondary funct ion and the DMM must be in ACV measurement function, and a valid range must be set. A double-precision floating-point Median voltage result is stored in the location pointed to by lpdResult. This measurement is a composite function which utilizes several sub functions, and could take over 10 seconds to perform . See the

Median measurement section of the manual for more detail.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

lpdResult

double FAR * Po ints to the location to hold the median voltage.

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Operation successfully completed.

Negati

ve Value Error code

Example

double

Medi an; int status = DMMRead Median(0, &Median);

DMMRea dNorm

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Take a reading that is in base value.

#inclu de "sm204032.h" int DMMReadNorm(int

nDmm, double FAR *lpdRead)

Signametrics 88

double floating-point reading. The returned value is corrected for base units. That is, it re turns 0.3 for a 300 mV input and 1e6 for 1.0 MOhm.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

lpdRead

double FAR * Pointer to a location where the reading is saved.

Integer value version code or an error cod e.

Value Meaning

DMM_E_RANGE

Over/Under range error.

DMM_E_DMM

Invalid DMM number.

Valid return.

DMM_O KAY

Example

double reading; int status = DMMReadNorm(0, &reading);

DMMReadPeakToPeak

SMX2040 † SM X2042 ; SMX 2044

;

Description

Rem

arks

Return ACV si gnal’s peak-to-peak value.

#include "sm204032.h"

int DMMReadPeakToPeak(int nDmm, double FAR *lpdResult)

Th is is a Secondary function and the DMM must be in ACV measurement function, and a valid range must b e set. A double-precision floating-point peak-to-peak voltage result is stored in the location pointed to by lpdResult. This measurement is a composite function which utilizes several sub functions, and could take ove r 10 seconds to perform.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are n umbered starting with zero.

Return Value

lpdResul t

double FAR * Points to the location to hold the Peak-to-Peak

The return value is one of the following constants.

value.

Value Meaning

DMM_OKAY

Operation successfully completed.

Example

Negative Value Error code double ptp; int status = DMMReadPeakToPeak(0, &ptp);

DMMRe adPer iod

SMX2040 † SMX2042 ; SMX2044

;

89 Signametrics

Description

Return the next double floating-point period reading from the DMM.

#include "sm204032.h"

int DMMReadPeriod(int nDmm, double FAR *lpdResult)

This is a Secondary function and the DMM must be in ACV measurement function, and a valid range must be set It makes a single period measurement, and stores the resul t as a double-precision floating-point number in the location pointed to by lpdResul t. See

DMMFre

quencyStr() for more details.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered startin g with zero.

lpdResul t

double FA

R * Points to the location which holds the period.

Return Value

The return value is one of the following const ants.

Value Meaning

DMM_OKAY

Operation successfu lly completed.

Error code

Negative Val ue

DMM_C NT_RNG

Period measurement hardware is over or under range.

Example

double d; int status; status = DM MReadPer iod(0, &d);

DMMReadStr

SMX2040 ; SMX2042 ; SMX2044 ;

Description Return the next reading from the DMM formatted for printing.

#include "sm204032.h"

Remarks

This function is the string version of DMMRead(). It reads the next Primary measurement result, performs all scaling and conversion required, and returns the result as a string formatted for printing. The print format is determined by the range and function. See DMMRead() for more details.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

lpszReading

LPSTR Points to a buffer (at least 16 characters long) to hold the converted result. The return value will consist of a leading sign, a floating-point value in exponential notation, and a units specifier.

Return Value The return value is one of the following constants, or the string length is OK.

Value Meaning

Signametrics 90

DMM_OKAY

Negative Value

Valid return.

Error code

DMM_E_RANGE

Example

DMM over range error occurred. char cBuf[17]; int status = DMMReadingStr(0, cBuf);

DMMReadTotalizer

SMX2040

† SMX2042 ; SMX2044 ;

Description Read the totalized value accumulated by the Totalizer function.

#include "sm204032 .h" long DMMRea

dTotalizer(int nDm m)

Remarks

This function re ads the total value accumulated by the Totalizer function. For details see

DMMStartTotalize.

Parameter Type/Description

Return Value

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

The return value is the totalized count, or if negative one of the following constants.

Example

Value Meaning

Negative Value Error code long total = DMMReadTotalizer(0);

91 Signametrics

DMMReadWidth

SMX2040 † SMX2042 ; SMX2044

;

Description Return the posit ive and negative pulse widths.

#i nclude "sm20 4032.h" int DMM Read

Width(int n Dmm, double FAR *lpdPwid, double FAR *lpdNwid)

Remarks This is a Secondary function and the DMM must be in ACV measurement function, and a valid range must be set. It returns t wo parameters: positive and negative pulse widths.

These parameters are stored as double-precision floating-point numbers in the loca tion pointed to by lpdPwid and lpdNwid. The measured widths are affected by the settin g of the Threshold D AC.

Parameter Type/Description

nDmm

lpdPwid

int Identifies the DMM. DMMs are n

double FA

umbered starting with zero.

R * Points to the location which holds the positive width.

lpdNwid

double FAR * Points to the location which holds the negative width.

Return Value

The return value is one of the following constants.

Value Meaning

Example

DMM_ OKAY

Negative Va lue

Operation successfully completed.

Error code double pw,nw; int state; state = DMMReadWidth(0, &pw, &nw);

DMMReady

SMX2040 ; S MX2042 ; SMX2044 ;

Description

Remarks

Return the ready state of the DMM following trigger operation.

#includ e " sm204032.h"

int DMMReady(int n Dmm)

Following the completion of an tirggered measurement event, be it hardware or software, the DMM indicates the completion. The DMMReady function checks the DMM and returns TRUE i f ready, and FALSE otherwise. Once a TRUE status is returned, the

DMMReady fu nction should not be used again since a TRUE also indicates that some flags have been clea r, which allow further operations. See DMMArmAnalogTrigger,

DMMArmTrigger, DMMTrigger, DMMReadBuffer and DMMPolledReaed for more details on this function.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Signametrics 92

Return Value

The return value is one of the following constants.

Value Meaning

TRUE

DMM is done and buffer is ready to be read.

DMM is not ready.

FALSE

Negative Va lue

Error code

Example double Buff er[10];

DMMTrigger(0,10); while( ! DM MReady(0) ); for

(i=0; i < 10 ; i++) DMMReadBuffer(0, &Buffer[i]);

DMMSetACCapsDelay

SMX2040 † SMX2042 † SMX2 044 ;

Description

Set the me asurement delay of AC based Capac itance.

#include " sm204032.h

"

#include "UserDMM.h"

DMMSe

time the measurement system settles. The DMM ’s default value is 2.0s. This function c an set this function from 0.0 to 10.0 seconds. Since the DMM is optimized for the defalut value, it is possible that changing this value will introduce additional error.

Parameter Type/Description

int Identifies the DMM. DMMs are numbered starting with zero. nDmm

ldDelay

double The time the DMM is allowed to settle the measurement.

Can be set beetween 0 and 10.0 seconds.

Return Value

Integer error code.

Value

Meaning

DMM_O KAY

Operation successfully completed.

Example

DMMSetACCapsDelay(0, 0.25); // Set measurement delay to 0 .25s

DMMSetACCapsLevel

SMX2040 † SM X2042 † SMX2044 ;

Description

Negativ

e Value Error code

Set the DCV so urce output level.

#include "sm2 04032.h"

#include "User DMM.h"

93 Signametrics

measurem ent function. It actually sets an internal register to ldVols rather than setting the output level itself. This value is used on any of the AC Caps calibration and t is necessary to perform open calibration of the AC Capacitance ranges to be used. Since the DMM is optimized for the mmended not to use this function and keep the default 0.45V peak value.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

ldVolts

double Peak value of AC voltage to be set. Can be 0.1V to 5.0V

Integer error code.

Value

Meaning

DMM_ OKAY

Operation succe ssfully completed.

Example

Negative Value Error code

DMMSetACCapsLevel(0, 0.35); // Set source to 0.7V peak-to-peak

DMMSetACVSource

SMX2040 † SM X2042 † SMX2044 ;

Description

Set the ACV so urce output level and frequency.

#include "sm20 4032.h"

#include "User DMM.h"

int

nDmm, double FAR ldVolts, double FAR ldFreq)

function s ets the AC voltage source to RMS amplitude of ldVolts, and the frequency to ldFreq. The DMM must be in VAC_SRC operation for this function to execute properl y. When the DMM is i n VAC_SRC operation, and the

DMMSetACVSource is applied, reading the DMM (DMMRead, DMMReadStr) will return th e meas urement of th e output voltage. This function acts on the main 12 bit source DAC. If better accuracy is needed it can be accomplished by selecting the

ClosedLoop mode (DMMSetSourceMode). This mode engages the Trim DAC, which augments the 12 bit DAC to produce 16 effective bits. In the ClosedLoop mode, the source level is adjusted any time the DMM is read, making small corrections until the reading is equal to ld Volts. However, for the ClosedLoop mode to update the source level, it is necessary to read the DMM multiple times. Update rate should not exceed 5 rps when using the Closed Loop mode. Tw o ACV measurement ranges are available in

VAC_SRC mode, the 3.3 V and the 330 m V. If the Autorange mode is enabled, the

DMM will automatically s elect the appropriate range.

Return Value

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

ldVolts ldFreq

double FAR AC RMS voltage to be set. Range: 0.05 to 7.25 V RMS

double FAR DC voltage to be set. Range: 2 Hz to 76 kHz

Integer error code.

Signametrics 94

Example

Value Meaning

DMM_O KAY

Operation successfully completed.

Negativ

e Value Error code double reading; int I;

DMMSetACVSource(0, 7.0, 1000.0); // source 7V and 1kHz

DMMSetSourceMode(0, CLOSED_LOOP); // Closed loop mode for(I=0;I<100;I++) DMMRead(0,&read ing); // update 100 times

DMMSetAuto Range

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Enable/Disable autorange operation of DMM

#inc lude "sm2 04032.h"

Remarks

utoRange(int nDmm, BOOL bAuto)

This function en ables or disables autorange operation of the DMM.

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

bAuto

BOOL Determines whether or not autoranging is done. The value

TRUE enables autoranging, FALSE disables it.

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Negative Value

Function succeeded.

Error code

Example status = DMMSetAutoRange(0, TRUE); /* enable autoranging */

DMMSetBuffT rigRead

SMX2040

; SMX2042 ; SMX2044 ;

Description

Setup the DMM for Triggered operation.

#include "sm204 032.h"

#include "UserDM M.h"

95 Signametrics

Remarks

Setup the SMX2040 for external hardware trigger operation. Following reception of th is command the DMM enters a wait state. After reception of an external trigger edge of

iEdge polarity, the DMM takes iSettle + 1 readings at the set measurement function, range, and reading rate; and stores the last reading in the in an internal buffer. This process is repeated for iSamples. This function is particularly useful in conjunction wit h a triggering in struments such as the SM4042 relay scanner. No autoranging is allowed in this mode. The number of trigger edges must be equal or greater than iSamples to prop erly termin ate this mode. Betw een the time the DMMSetBuffTrigRead is issued and the time the buffer is read, no other command should be sent to the DMM. One exception is the DMMDisarmTrigger command. This function is usable for VDC,

VAC, Ohms, IAC, IDC and RTD measurements.

Use the DMMReady to monitor when the DMM is ready (following trigger(s) and the re ading of iSam ples). When ready, you can read up to iSamples, using

DMMReadBuffer or DMMReadBufferStr functions. Once DMMReady returns

TRUE, it should not be used again prior to reading the buffer, since it prepares the buffer for reading when it detects a ready condition.

Parameter Type/Description

nDmm iSettle

iSamples

int Identifies the DMM. DMMs are numbered starting with zero.

int The number of setteling measurements, prio r to read value. Must be set between 0 and 120. Recommanded value i s 4.

int

The number of samples the DMM takes following the same num ber of trigger pulses. This number must be between 1 and 64, inclusive.

iEdge

Int The ed ge polarity of the trigger signal. 1 for Positive, or leading edge, and 0 for negative or trailing edge trigger.

Return Value

The return value is one of the following constants.

Value Meaning

DMM_ OKAY

Operation successfully terminated

Error code.

E

xample double

DMMSetBuffTrigRead(0, 4, 64, 0); // Negative edge, 4

//s etteling readings, an d 64 samples/triggers while( ! DMMReady(0) ); for(i=0; i < 64 ; i++)

// wait for completion

// read buffer

Negativ e Value

DMMSetCapsAveSamp

Description

Tunes the capacitance m easurem ent function parameters for higher measurement speed.

#include "sm204032.h"

Remarks This function should be used carefully since it modifies the capacitance function basic measurement parameters; the avera ges value, iAverage, and the number of points sampled, iSamples. This function is provided only for cases where it is necessary to

Signametrics 96

improve measurement speed. W hen using this function keep in mind that the accuracy spec ification provided for capaci tance is not guaranteed. Also, modifying these values coul d have profound efect on the operation of the function. Any time a capacitance range is change, these values are set t o the default values. For instance, values of 1 and 3 for

iAverage, and iSamples will red uce measurement time on the 12nF range from 0.8s to about 50ms.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

iAverage

int The average value, must be set between 1 and 100.

Return Value

iSample s

int The number of samples must be set to at least 3.

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Valid return.

Example

Negative Value Error code int status = DMMSetCapsAveSamp(0,1,3);

DMMSetCJTemp

SMX2040 ; S MX2042 ; SMX2044 ;

Description

Remarks

Set cold ju nction tem perature for thermocouple measurement.

#includ e " sm204032.h"

DMMSetCJTemp

Set the cold junction temperature for subsequent thermocouple measurements. When measuring temperature using thermocouples it is necessary to establish a reference or cold junction temperature. This is the temperature at which the thermocouple wires are connected to the DMM or to the switching card’s cooper wires. One way to do this is by simply entering this value using DMMSetCJTemp() function. dTemp must be entered using the currently set tem perature units.

Return Value

Parame ter Type/Description

nDmm dTemp

int Identifies th e DMM. DMMs are numbered starting with zero.

double The cold junction temperature. Must be set between 0

50 o

C or the corresponding o

F. o

C and

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Operation successfu lly terminated

Negative Val ue

Error code.

Example

DMMSetCJTem p(0, 22.5);

97 Signametrics

DMMSetCompThreshold

SMX2040 † SMX2044 ;

Description

Set the Th reshold DAC level.

#include " sm204032.h

"

#include " UserDMM .h"

R em

arks This

DMM must be in AC volts. This function sets the detection threshold of the AC comparator. It is co mpared by the comparator to the AC coupled input voltage. This function is associated with the following functions: Totalizer, Frequency counter, Period,

Pulse width and Duty Cycle meas urements. ldThreshold range is determined by the se lected ACV range. For instance, when the 250 V AC range is selected, the allowed range of ldThreshold is –5 00 V to +500 V. See the specification section for more details.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

ldThresh old

double FAR DC voltage to be set. Allowed range depends on selected ACV range.

Integer error code.

Value

Meaning

DMM_OKAY

Operation successfully completed.

Negative Value Error code

Example

DMMSetCompThreshold(0,28.5); // Set comp. threshold to 28.5V

DMMSetCounterRng

SMX2040 † SMX2042 ; SMX2 044 ;

Description

Set the fre quency counter to a specific range.

#include " sm204032.h

"

#include " UserDMM .h"

int

R em

arks This functio n forces the auto-ranging frequency counter to a specific range, frange. Use this function if t he approximate frequency to be measured is known. It will eliminate the time necessary for t he counter to autorange to the appropriate range. Saves time by removing the requirement to make multiple frequency measurements in order to allow the counter to range. All ranges are defind in UserDMM.h file.

Parame ter Type/Description

nDmm

frange

int Identifies the DMM. DMMs are numbered starting with zero.

int The range to be set is a value between 0 and 7. See UserDMM.h

Signametrics 98

Return Value

Integer error code.

Value

Meaning

Negativ

e Value

Error code

Example

DMMSetCounterRng(0, COUNTR_320HZ); // Set counter to measur e a frequency between 65Hz to 320Hz

DMMSetDCISource

SMX2040 † SM X2042 † SMX2044 ;

Description

DMM_O KAY

Operation successfully completed.

Set the DCI sou rce output level.

#include "sm2 04032.h"

#include "User DMM.h"

Return Value

dary func tion sets the DC current source to ldAmps. The DMM must be in

IDC_SRC

for this function to execute properl y. Further, the appropriate DCI range must be selec ted . When the DMM is in IDC_SRC o peration, and the DMMSetDCISource is applied, re ading the DM M (DMMRead or DMMReadStr) will return the output voltage measurem ent. This fun ction acts on the main 12 bit source DAC. If better resolution is needed it can be accomplished by s etting the Trim DAC by using the

DMMSetTrimDAC function. There are five current source ranges. The D MM reads the output (load) voltage.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

ldAmps

dou

ble FAR DC current to be set. Can be 0 to 1.25 X selected range

Integer error code.

Value

Meaning

DMM_OKAY

Operation successfully completed.

Negative Value Error code

Example

DMMSetRange(0, _1uA) // Select 1uA source range

DMMSetDCISource(0, 1.1e-6); // Set source to 1.1uA

DMMSetDCVSource

SMX2040 † SMX2042 † SMX2044

;

Description

Set the DCV so urce output level.

#include "sm2 04032.h"

#include "UserDM M.h"

99 Signametrics

Example

ction to execute properly. When the DMM is in VDC_SRC operation, and the DMMSetDCVSource is applied, reading the DMM (DMMRead or

DMMReadStr) will return the measurement of the output voltage. This function acts on the main 12 bit source DAC. If better accuracy is needed it ca n be accomplished by selecting the ClosedLoop mode (DMMSetSourceMode). This mode engages the Trim

DAC, which augments the 12 bit DAC to produce 16 effective bits. In ClosedLoop mode, the so urce level is adjusted every time the DMM is read, making small corrections until the reading is equal to ldVolts. However, for the ClosedLoop mode to update the source level, it is necessary to read the DMM multiple times. Update rate should not exceed 10 rps when using the Close d Loop mode. The DMM reads voltages using the 33

V range.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are n umbered starting with zero.

Return Value

ldVolts

double FAR DC voltage to be set. Can be –10.5 to 10.5 V

Integer error code.

Value Meaning

DMM_OKAY

Ope ration successfully completed.

Negative Va

lue Erro r code double reading; int I;

DMMSetDCVSource(0, 1.25); // Set so urce to 1.25V

DMMSetSourceMode(0, CLOSED_LOOP); / / Closed loop mode for(I=0;I<100;I++) DMMRead(0,&reading); // update 100 times

DMMSetExternalShunt

SMX2040 † SM X2042 † SMX 2044 ;

Description

Set the val ue of the leakage function exte rnal shunt

#include "sm204032.h"

Rem Se

condary function sets the value of the external shunt resistor being used. The shunt value is utiliz ed in measurement functions such as Leakage and Extended resistance, Synthesized resistance etc. It is available with S/W versions 1.75 or higher.

ldShunt sets the shunt va lue, such that 10,000.0 correxponds to a 10k

shunt.

Return Value

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

ldShunt

double Shunt resistance value. A value greater than zero and smaller the 200e6 (200 Mega Ohms) is allowed.

Integer error code.

Value

Meaning

DMM_OKAY

Operation successfully completed.

Signametrics 100

Negative Va

lue

Erro r code

Example

DMMSetExternalShunt(0, 100000.0); // Set shunt to 100k

DMMSetFuncRange

SMX2040 ; SMX2042 ; SMX2044

;

Description Set the DMM f unction and range.

#include "sm2 04032.h"

#include "User DMM.h"

SetFu

ncRange(int nDmm, int nFuncRnge)

Remarks

This function sets both, the function and range used by the D MM. The table of values is defined as VDC_330mV, VAC_3.3V, IDC_330mA, OHM_4W_330K etc. definitions in the header files.

Parameter Type/Description

Return Va

lue

nDmm

nFuncRnge

int Identifies the DMM. DMMs are numbered starting with zero.

int A pre-defined constant corresponding to the desired function and range.

The return value is one of the following constants.

Value Meaning

DMM initialized successfully.

DMM_OKAY

Negative Value

Error code

DMM_E_FUNC Invalid DMM function.

Example status = DMMSetFuncRange(0, VDC_3V);

DMMSetFunction

SMX2040 ; SM X2042 ; SM X2 044 ;

Description Set the D M M function .

#include "sm204032.h"

#include "UserDMM.h"

Remarks

This function sets th e function used by the DMM. The table of values is defined by the

VDC, VAC, IDC, IAC, OHMS2W, OHMS4W … definitions in the DLL header file. Not all functions are available for all DMM t ypes. For instance the SMX2044 has

C apacitance while the SMX2040 does not.

101 Signametrics

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are num bered starting with zero.

Return Value

nFunc

int A pre-defined c onstant corresponding to the desired function.

The return value is one of the following constants.

Value Meaning

DMM_OKAY

DMM initialized successfully.

Negative Value

Error code

DMM_E_FUNC

Invalid DMM function.

Example status = DMMSetFunction(0, INDUCTANCE);

D MMSetInductFreq

SMX2040 † SMX2042 † SMX2044 ;

Des cription

Set the frequency of the Inductance Source.

#include "sm20403 2.h"

int

nDmm, double FAR lpdFreq)

Remarks

This function sets the freq uency of the Inductance measurement source. The value of the fr equency should be between 20 Hz and 75 kHz. This function overrides the default frequency for each of the inductance ranges. T herefore, setting a new Inductance measurement range changes the frequency. Use this function after setting the range.

Parame ter Type/Description

Return Value

nDmm

lpdFreq

int Identifies the D MM. DMMs are numbered starting with zero.

double FAR Freq uency to be set.

Integer error co de.

Value Meaning

Example

DMM_O KAY

Operation successfully completed.

Negativ

e Value

Erro r code int st atus = DMMSetInductFreq(0, 10e3); // Set source to 10kHz

DMMSet OffsetOhms

SMX2040 ; SM X2042 ; SMX20 44

;

Descriptio n

Enable/Disable Offset Ohms operation

#i nclude "sm204032.h"

DMMSetOffset

Ohms(int nDmm, BOOL bState)

Signametrics 102

R

emarks

This function enables or disables the Offset Ohms compensation function. The default value is FALSE, or no Offset O hms compensation. When TRUE the measurement rate is ab out 1/10 the set value. When enabling this function with the SM2042, a relay is used to perform it and therefore it will click while measuring.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

bState

BOOL Determines whether or not Offset Ohms is enabled. The value

TRUE enables, FALSE disables it.

Return Value

The return value is one of the following constants.

Value Meaning

DMM_ OKAY

Function succeeded.

Negativ

e Value Error code

Example

status = DMMSetOffsetOhms(0, TRUE); // enable OffsetOhms

DMMSet Range

SMX2040 ; SMX2042 ; SMX2044 ;

Description

Remarks

Set the DMM range for the present function.

#include "sm2 04032.h"

int DMMSetRange(int nDmm, int nRange)

This function s ets the rang e used by the DMM for the present function. The table of values is defined by the _330mV, _3mA, etc. definitions in the DLL header file. Not all ranges a re avai lable for all DMM types. For inst ance the SMX2044 has a 33 Ohms range, and the SMX2040 does not.

Parameter Type/Description

nDmm

nRange

int Identifies the DMM. DMMs are numbered starting with zero.

int A pre-defined constant corresponding to the desired range.

The re turn value is one of the following constants.

Value Meaning

DMM_OKAY

DMM initialized successfully.

Negative Value Error code

DMM_E_RANGE Invalid DMM range value. status = DMMSetRange(0, _330mA); Example

DMMSetRate

SMX2040 ; SMX2042 ; SMX2044 ;

103 Signametrics

Description S et the DMM reading rate.

#include "sm204032.h"

int DMMSetRate(int nDmm, int nRate)

Remarks This function sets the reading rate used by the DMM. The table of values is defined by the RATE_ values in the header file. It is important to note that the actual range may be effected by the speed of the CPU as well as other processes run ning in the background, cons uming CPU resources. In order to improve the

DMM’s measurement rate you may need to do one of the following. Stop or lower the thre ad priority of competing processes, and/or raise the thread prio rity of the DMM.

Thread Priorities can be manipulated manually, or in a programming environment. manually: In the Windows Task M anager, select the "Processes" tab, then right click on the process and select "Set Priority". In a programming envirmonment: Windows provides an API for managing the priority of different threads . For in stance, in C/C++, the functions S etPriorityClass() and

SetThre adPrio rity() can be used to manage the t hread priority

Parameter Type/Description

nDmm int Identifies the DMM. DMMs ar e numbered starting with zero.

nRate

int A pre-defined constant (RATE_*) corresponding to the desired reading rate.

Return Value

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Negative Value

DMM_E_RATE

DMM initialized successfully.

Error code

Invalid DMM reading rate.

Example status = DMMSetRate(0, RATE_0P1); // Set to 0.1rps

DMMSetRelative

SMX2040 ; SMX2042 ; SMX2044 ;

Signametrics 104

De

scription

Remarks

Set the DMM relative reading mode for the present function.

#include "sm20403 2.h"

bRelative)

This function selects relati ve or absolute reading mode for the DMM. If the bRelative parameter value is TRUE, th e DMM will change to relative reading mode. If FALSE, the DMM will change to absolute reading mode. Caution: Do not select

DMMSetRelative when in the autorange mode.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

bRelative

BOOL TRUE to e nter relative mode, FALSE to clear mode.

The return valu e is one of the following constants.

Value Meaning

DMM_O KAY

DM M mode changed successfully.

Example

Negativ

e Value Error code status = DMMSetRelative(0, TRUE) ;

105 Signametrics

DMMSetResistance

SMX2040 † SMX2042

† SMX2044 ;

Description

Set the re s istance value to be synthesized

#include "sm204032.h"

int

nDmm, double ldResistance)

This function sets th e value of the resistance to be synthesized. The DMM must be in

Synthesized Resistan ce function for this function to be usable. The currently set external shunt resistor value effects the Synthesized Resistance operation. The ldResistance value must be between 10.0 to 0e6 (10M

Ω). It is available with S/W versions 1.71 or higher.

Parameter Type/Description

nDmm int Identifies the DMM. DMMs are numbered starting with zero.

Return Value

ldResistance

double Resistance value to be synthesized. Value from 10 to 10e6.

Integer error code.

Value

Meaning

DMM_OKAY

Operatio n successfully co mpleted.

Negativ

e Value Error code

Example

DMMSetResistance(0, 10000.0); // Synthesize 10k

DMMSet RT D

SMX2040 † SMX2040 ; SMX2044

;

Description

Set the RTD pa rameters.

#include "sm20403 2.h"

#include "UserDMM.h"

DM M

nDmm, int iWires, doub le FAR ldRo)

Remarks

Sec on

dary functi on sets the RTD parameters. The DMM must be in RTD measurem ent function for this function to execute properly. iWires selects between

3-wire and 4-wire RTD (3-wire RTDs are not implemented in this version of software).

ldRo sets the RTD R o

(Ice point resistance). This function must follow the selection of the basic RTD type, using DMMSetRange, since it modifies the default R o

parameter for the selected R TD.

Parameter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

iWires

int RTD’s number of connecting wires RTD_4_W or RTD_3_W

ldRo

RTD type.

Return Value

Integer error code.

Signametrics 106

Value Meaning

DMM_ OKAY

Operation successfully completed.

Negativ

e Value Error code

Example

DMMSetFunction(0, RTD); // RTD measurement function

DMMSetRange(0, 1 _pt385); // Select RTD

DMM SetRTD(0 , RTD_4_W, 10 00.0); // Set Ro = 1k Ohms

DMMSet Sens oreParam s

SMX2040 ; SMX2042 ; SMX2044

;

Description

Set the cold junction t emperature sensor equation parameters.

#include "sm204032.h"

Remarks Set the col d junction temperature sensor’s equation parameters. Where the temperature of

(Vcjs - lda) / ldm + ldb, where Vcjs is the cold junction sensor output. This function is used to calculate the cold junction temperature by converting the sensor voltage to temperature. For more information read about

DMMReadCJTemp().

Parameter Type/Description

Return Value

nDmm

lda ldm ldb

int Id entifies the DMM. DMMs are numbered starting with zero.

double the ‘a’ parameter.

double the ‘m ’ parameter.

double the ‘b’ parameter.

Integer error code.

Value

Meaning

DMM_ OKAY

Operation successfully completed.

Negative Va

lue Error code

Example

DMMSetSensorParams(0, 0.558, -0.002, 22.0);// set parameters

DMMSetSourceMode

SMX2040 † SMX2042 † SMX2044

;

Description

Set the DCV and ACV sources to ClosedLoop, or OpenLoop mode.

#include "sm204032.h"

#include "User DMM.h"

107 Signametrics

Remarks This

OOP or

CLOSED_LOOP. In CLOSED_LOOP the sources use the main 12 bit source DAC. In

CLOS

ED_LOOP the Trim DAC is also used, which augments the 12 bit DAC to produce 16 effectiv e bits. Open loop updates are very quick. In ClosedLoop mode the source level is adju sted every time the DMM is read, making small corrections until the reading is equal to the set voltage. However, for the ClosedLoop mode to update the source level, it is necessa ry to read the DMM multiple times. See DMMSetDCVSource and DMMSetACVSource for more details.

Parame ter Type/Description

nDmm int Identifies the DMM. DM Ms are numbered starting with zero.

iMode

int Source adjustment mode: CLOSED_LOOP or OPEN_LOOP

Return Value

Inte ger error co de.

Value Meaning

Example

DMM_OKAY

Oper ation successfully completed.

Negative Value

Error code

DMMSetSourceMode(0, CLOSED_LOOP); // Select closed loop mode

DMMSetSynchronized

SMX2040 ; SMX2042 ; SMX2044 ;

D escript ion

Remarks

Enable or disable Synchroneous operation of the DMM.

#include "sm204032.h"

DMMSetSynch

ronized(int nDmm, BOOL bSync)

This function enables or disables t he Synchronized operation of the DMM. Default operation is non-synchronized. Sel ect the Synchronized mode when it is necessary to settle full scale input trans itions from one reading to the next, and maintain the accuracy of the DMM. This is appro priate for VDC, Ohms, Leakage, DCI, Diode and Guarded

Ohms. The result of the synchroni zed mode is a reduced measurement rate. To run synchronized, reading rate must be set to 10 rps or high er.

Parame ter Type/Description

nDmm int Identifies the DMM. DMMs are numbered st arting with zero.

Return Value

bSync

BOOL Determines whether or not synchronized operation is enabled.

TRUE enables and FALSE disables synchronization. The default is

FALSE.

The return value is one of the follow ing constants.

Value Meaning

DMM_OKAY

Function succeeded.

Negative Value Error code

Signametrics 108

Example

int status = DMMSetSynchronized(0, FALSE); // Cancell sync.

DMMSetTCType

SMX2040 ; SM X2042 ; SM X2044

;

Description

Remarks

Set Ther mocou ple type

.

#include "sm204032.h"

#include "UserDMM.h"

DMM

This function selects the thermocouple type to be measured and linearized. It must be one of the following: B, E, J, K, N, R, S or T.

Parame ter Type/Description

NDmm

int Identifies the DMM. DMMs are numbered starting with zero.

iTempUnits

int The thermocouple type to be selected. This value can be set from

BTyppe to TType as defined in the UserDMM.H file

.

Return Value

The return value is one of the following constants.

Value Meaning

DMM_ OKAY

Function succeeded.

Negativ

e Value Error code

Example

int status = DMMSetTCType(0, NType) // select N type TC

DMMSetTemp Units

S MX2040 ; SMX2042 ; SMX2044 ;

Description

Set temperature units to

°C or °F.

#include "sm204032.h"

#inc lude "User DMM.h"

Remarks

mpUnits(int nDmm, int iTempUnits)

This function se ts the temperature units to either

°C or °F. This is applicable to both the on-board tempe rature sensor and the RTD measurements.

Param eter Type/Description

nDmm

iTempUn its

int Identifies the DMM. DMMs are numbered st arting with zero.

int Temperature units can be either DEG_F for

The default is

°C.

°F,

or DEG_C for

°C.

109 Signametrics

Return Value

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Function succeeded.

Negativ

e Value

Error code

E xa mple

int st atus = DMMSetTempUnits(0, DEG_F) // set units to

°F

DMMSetTrigRead

SMX2040 ; SMX2042

; SMX2044 ;

Description

Setup the DMM for mutip le Triggered readings operation.

#include "sm204032.h"

#include "UserDMM.h"

Remarks Setup the SMX2040 for external hardware trigger operation. Following reception of this command the DMM enters a wait state. After reception of an external trigger edge of

iEdge polarity, the DMM takes iSettle + 1 readings at the set measurement function, range, and reading rate; and sends the last reading. This process is repeated for iSamples .

iSamples Trigger pulses must be issued to complete this process. This function is particularly useful in conjunction with a triggering instruments such as the SM4042 relay scanner. No autoranging is allowed in this mode. The number of trigger edges must be equal or greater than iSamples to properly ter minate this mode. Following the issue of the

DMMSetT rigRead

command, and until the sam pling process ends, it is necessary to read the sample s from the DMM usin g the DMMReadMeasurement command. This will prevent an O verrun communication error, whereby the rate at which measurem ent are read does no t keep up with the DMM transmission. The DMM has a built in 5 readings fifo to reduce t his problem. This function is usable for VDC, VAC, Ohm s, IAC,

IDC and RTD m easurements.

Use the DMMReadMeasurement to both, monitor when the DMM has new data, and to read this data. Read as many samples as iSamples to guarantee proper termination of this capture process.

Parameter Type/Description

int Identifies the DMM. DMMs are numbered starting with zero.

nDmm iSettle

int The num ber of setteling measurements, prior to read value. Must be set bet ween 0 and 120. Recommanded value is 4.

iSamples

int The number of samples the DMM takes following the same number of trigger pulses. This number must be between 1 and 250, inclusive.

Return Value

iEdge

Int The edge polarity of the trigger signal. 1 for Positive, or leading e dge, and 0 for negative or trailing edge trigger.

The return value is one of the following constan ts.

Value Meaning

DMM_OKAY

Operation successfully terminated

Signametrics 110

Negative Value

Error code.

Example

Reading[150];

DMMSetTrigRead(0, 4, 150, 0); // Negative edge, 4

//setteling readings, and 150 samples/triggers for(i=0; i < 150 ; i++) // read buffer while( ! DMMReadMeasurement(0 , Reading[i]) );

DMMSetTrimD AC

SMX20

40 †

SMX20

42 †

SMX20

44 ;

Description

Set the Trim DAC level.

#include "sm20 4032.h"

#include "UserDMM.h"

DAC can be set t o augment the main 12 bit DAC, whenever it is not automatically performed, such as in VDC and VAC source while OPEN_LOOP mode is selected. An example would be in DCI source, or when setting the Comparator Threshold. This function consumes a lot of the on-board microcontroller’s resources and must be turned off when not in use. Use DMMDisableTrimDAC to turn off. With the Trim DAC the effective re solution of the composite DAC is increased to 16 bits. With iValue set to 100, the Trim DAC adds slightly over 1 LSB of the 12 bit DAC. See DMMSetDCVSource and DM

M

SetACVSource for more details.

Parameter Type/Description

nDmm

iValue

int Identifies the DMM. DMMs are numbered sta

100% Trim DAC level. rting with zero.

int Amplitude can be set from 0 to 100, corresponding to 0% to

Return Value

Integer error code.

Value

Meaning

DMM_OKAY

Operation successfully completed.

Example

Negative Value Error code

DMMSetDCVSource(0, 5.0); // Set source to 5V

DMMSetTrimDAC(0, 50); // add about 2.5mV to output

DMMStartTotalizer

SMX20

40 †

SMX20

42 ;

SMX20

44 ;

Description

Clear the totalized value and start the totalizer.

#include "UserDMM.h"

#include "sm204032.h"

111 Signametrics

int

Remarks This is a Secondary function and the DMM must be in ACV measurement function, and a valid range must b e selected. This function clears the Totalized count, sets the edge sense, and starts the Totalizer. The totalized value can be read during the accumulation period. However, it could affect the count by the inter ruption. If no reads are performed during accumulation, the i nput rate can be as high as 45 kHz. If reads are performed during the accumulation p eriod, this rate could be as low as 20 kHz. The Threshold DAC sets the level at which signals are coun ted. During accumulation, no other command

(except DMMReadTotalizer) should be used. When done, this function must be turned off using DMMStopTotalizer. After the Totalizer is stopped, the accumulated result can be read using DMMReadTotalizer. A normal procedure would be to set the DMM to the ACV function, select voltage range, set the Thre shold DAC, start the totalizer, wait for the time required, stop and read the total. The total number of events is limited to

1,00 0,000,000.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are n umbered starting with zero.

Return Value

Edge

int Ident ifies the edge of the counter. If TRAILING (0) count negative edges, if LEADING (1) count positive edges

Integer error co de.

Example

Value Meaning

DMM_OKAY

Operation successfully completed.

Negative Va

lue

Error code int status = DMMStartTotalizer(0, LEADING);

Signametrics 112

DMMStopTota lizer

SMX2040 † SMX2042 ; SMX2044 ;

Description

Terminate the accumulation process of the To talizer.

#include "sm204032.h"

DMMStopTotalizer(int nDmm)

Remarks This function stops the accumulation process. Following this function, the totalized value can be read. For details see DMMStartTotalizer.

Return Value

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with ze ro.

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Operation was successful.

Negative Value Error code

Example int st atus = DMMStopTotalizer(0);

DMMTer mina te

SMX2040 ; SM X2042 ; SM X2044

;

Description

Remarks

Termina te DMM operation (DLL)

#include "sm2 04032.h" int DMM Term

inate(int nDmm)

Removes DMM number nDmm. This routin e is used only where it is needed to terminate one DMM and start a new one at the same n Dmm location. Otherwise, it is not recommended to use this function.

Return Value

Parame r

nDmm int Identifies the DMM to be suspended.

The return value is one of the following constants.

Example

Value Meaning

TRUE

DMM Te rminated

FALSE

DMM was not initialized, termination is redundant.

DMMTerminate(0); /* Terminate DMM # 0 */

113 Signametrics

DMMTrig ger

SMX2040 ; SMX2042 ; SMX2044

;

Description

Remarks

Software Trigg er the DMM. Take iSamples.

#include "sm2 04032.h" i nt DMMTrigg

er(int nDmm, int iSamples)

Following reception of this command, the SMX2040 DMM m akes iSamples readings at the currently set function, range and rate, and stores them in an internal buffer. Rate can be set between 10 t o 1000 readi ngs per second. No autoranging is allowed for this trigger operatio n. Between the time the DMMTrigger command is issued and the time the buffer i s read, no ot her com mand should be sent to the DMM. Use the DMMReady function to mon itor when the DMM is ready (ready implies completion of iSamples).

When ready , you can opt ional ly read a single reading or up to iSamples, using

DMMRe adBuf

fer.

Parame ter Type/Description

nDmm

int Identifies the DMM. DMMs are numbered starting with zero.

iSamples int The number of samples the DMM takes following a trigger pulse.

This number must be between 1 an d 64, inclusive.

Return Value

The return value is one of the following constants.

Value Meaning

DMM_ OKAY

DMM_E _INIT

DMM_TRIG_N

DMM_E_D

MM

Operation successfully terminated.

DMM is uninitialized. Must be initialize prior to using any function.

Measurement count is out of allowed range.

Invalid DMM number. er[64];

DMM Trigger( 0,64); while( ! DMMReady(0)); for(i=0; i < 64 ; i++) state = DMMReadBuffer(0, &Buf fer[i]);

DMMWid thSt r

SMX20

40 †

SM X20

42 ;

SMX2 0

44 ;

Description Return p ositive and negative p ulse width in string format.

#include "sm204032.h"

measurement results are stored at the location pointed to by lpszPos and lpszNeg. See

DMMReadWidth for more details.

Signametrics 114

nDmm

lpszPos

int Identifies th e DMM. D MMs are numbered starting with zero.

lpszNeg

LPSTR Points to a buffer (at least 16 characters long) to hold the positive width result.

LPSTR Points to a b uffer (at least 16 characters long) to hold the negative width result.

Return Value

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Valid return.

Error code

E

xample char cBuf[17]; int status = DMMWidthStr(0, cBuf);

SetACCapsFreq

S MX2040 † SMX2042 † SMX 2044 ;

Description

Negative Val

ue

Sets the frequency of the AC capacitance source.

#include "sm204032.h"

CCapsFreq(int nDmm, LPS TR lpszPos, doouble dFrequency)

Remarks

This ser vice function allows the modification of the AC source frequency. This is only active du ring in-circuit capacitance test. The frequency may be set between 10Hz and

75kHz.

Example

Parameter Type/Description

nDmm

dFrequency

int Identifies the DMM. DMMs are numbered starting with zero.

doulbe The frequency to be set (10 to 75,000).

Return Value

The return value is one of the following constants.

Value Meaning

DMM_OKAY

Valid return.

Negative Value Error code

SetACCapsFreq(0, 10000.0) // Set the frequency to 10kHz

115 Signametrics

6.0 Maintenance

Warning

These service instructions are for use by qualified personnel only. To avoid electric shock, do not perform

any procedures in this section unless you are qualified to do so.

This section presents maintenance information for the DMM.

Test equipment recommended for calibration is listed below. If the recommended equipment is not available, equipment that meets the indicated minimum specifications may be substituted. In general, the calibration e quipment should be at least three times more accurate than the DMM specifications.

Table 9-1. Recommended Test Equipment

Minimum Specifications

Recommended Model

Instrument Type

Multi-Function Calibrator

DC Voltage Range: 0-300 V

Voltage Accuracy: 9 ppm

AC V oltage Range: 0-250 V

Voltage Accuracy: 0.014%

Resistan ce Range: 0-330 M

Resistance Accuracy: 22 ppm

DC Current Range: 0-2.5 A

Curr ent Accura cy: 0.0

08%

AC Current Ra nge: 50 uA – 2.5

A

Current Accura cy: 0.05%

Capacitance Range: 10

ηF – 10 mF

Capacitance Accuracy: 0.19%

Fluke 5520A

Signametrics 116

6.1 Performance Tests

This test compares the performance of the SMX2040/44 with the specifications given in Section 2. The test is recommended as an acceptance test when the instrument is first received, and as a verification after performing the calibration procedure. To ensure proper performance, the test must be performed with the SMX2040 installed, with the covers on. The ambient temperature must be between 18

°C to 28°C. Allow the SMX2040 to warm up at least one-half hour before performing any of the tests. The default reading rate of the SMX2040 should be used in each test.

7

8

9

4

5

6

St ep

1

2

3

6.2 DC Voltage Test

The following procedure may be used to verify the accuracy of the DCV function:

1. If you have not done so, install the SMX2040. Ensure that the chassis has been on for at least one-half hour, with all covers on, before conducting this test.

2. Apply a high quality copper wire short to the SMX2040 V,

+ & - inputs. Select the DCV function, Autorange.

Allow the SMX2040 to settle for several seconds, and perform the Relative function.

3. Apply the following DC voltages to the V,

+ & - terminals. Check to see that the displayed reading on the

SMX2040 is within the indicated range.

T able 9-2. DC Voltage Test

Range Input Mini mum Reading Maxim um Reading

330 mV

330 mV

330 mV

3.3 V

3.3 V

33 V

33 V

330 V

330 V

0V (short)

190 mV

-190 mV

1.9 V

-1.9 V

19 V

-19 V

190 V

-190 V

-8

µV

+8

189.9787mV

-190.0213 mV

190.0213 mV

–189.9787 mV

1.899898 V

-1.900102 V

18.99834 V

1.900102 V

-1.899898 V

19.00166 V

-19.00166 V

189.9833 V

-190.0167 V

-18.99834 V

190.0167 V

-189.9833 V

117 Signametrics

5

6

7

8

Step

1

2

3

4

6.3 Resistance Test, 2-wire

The following procedure may be used to verify the accuracy of the 2-wire function.

1. If you have not done so, install the SMX2040 and place the covers back on to the computer. Ensure that the computer has been on for at least one-half hour, with the covers on, before conducting this test.

2. Connect the SMX2040 V,

Ω + & - terminals to the calibrator HI & LO Outputs. Output

0

Ω from the calibrator. Allow the SMX2040 to settle for a few seconds, and perform the Relative function. (This effectively nulls out the lead resistance of your cabling. If you are using a Fluke 5700A or 5520A Calibrator, the

2-wire Compensation feature will give a more accurate 2-wire ohms measurement. See the Fluke Operator's

Manual for further instructions.)

3. Apply the following Resistance values to the V,

+ & - terminals . Check to see that the displayed reading on the SMX2040 is within the indicated range.

Table 9-3 Resistance Test, 2-wire

Range

33

Ω [1]

Input Minimum Reading Maximum Reading

10

Ω 9.9972 Ω

330

Ω 100

3.3 k

Ω 1 k

Ω 1.000083

33 k

Ω 10 k

Ω 10.00095

330 k

Ω 100 k

Ω 100.014

3.3 M

Ω 1

M

Ω 1.00058

33 M

Ω 10

M

Ω 10.027

330 M

Ω [1]

100 M

Ω 97.92

M

[1] SMX2044 only

6.4 Resistance Test, 4-wire

The following procedure may be used to verify the accuracy of the 4-wire function.

1. If you have not done so, install the SMX2040 and place the covers back on to the chassis. Ensure that the computer has been on for at least one-half hour, with the covers on, before conducting this test.

2. Connect the SMX2040 V,

+ & - terminals to the calibrator HI & LO Output. Connect the SMX2040 I, 4W

+ & - terminals to the HI & LO Sense terminals.

3. Select the 4W

Ω function on the SMX2040, Autorange. Set the calibrator to 0 Ω. Be certain that the calibrator is set to external sense ("EX SNS" on the Fluke 5700A or “4-Wire Comp” on the 5520A). Allow the SMX2040 to settle for a few seconds, and perform the Relative function.

4. Apply the following Resistance values to the V,

+ & - terminals. Check to see that the displayed reading on the SMX2040 is within the indicated range.

Signametrics 118

Table 9-4 Resistance Test, 4-wire

5

5

6

3

4

5

Step

1

1

1

2

Range

33

Ω [1]

Input Minimum Reading Maximum Reading

0

Ω -2 m

33

Ω [1]

10

Ω 9.9972 Ω

330

Ω 0 m

Ω 6

330

Ω 100

3.3 k

Ω 0 m

Ω 33

3.3 k

Ω 1 k

Ω 1.000083

33 k

Ω 0 m

Ω 350

33 k

Ω 10 k

Ω 10.00095

330 k

Ω 0

330 k

Ω 100 k

Ω 100.014

[1] SMX2044 only.

Note: The use of 4-wire Ohms for resistance values above 300 k

Ω is not recommended.

119 Signametrics

7

8

9

4

5

6

Step

1

2

4

5

6

7

8

9

Step

1

2

6.5 AC Voltage Test

The following procedure may be used to verify the accuracy of the ACV function:

1. If you have not done so, install the SMX2040 and place the covers back on to the chassis. Ensure that the computer has been on for at least one-half hour, with the covers on, before conducting this test.

2. Apply the following AC voltages to the V,

+ & - terminals. Check to see that the displayed reading on the

SMX2040 is within the indicated readings range.

Table 9-5. Mid-Frequency AC Voltage Tests

All inputs are a sine wave at 400 Hz.

Range Input Minimum Reading Maximum reading

330 mV

330 mV

3.3 V

3.3 V

33 V

33 V

250 V

250 V

10 mV

190 mV

100 mV

1.9 V

1 V

19 V

10 V

190 V

9.865 mV

189.595 mV

0.098735 V

1.897565 V

0.98327 V

18.97313 V

9.864 V

189.756 V

10.135 mV

190.405 mV

0.101265 V

1.902435 V

1.01673 V

19.02687 V

10.136 V

190.244 V

Table 9-6. High-Frequency AC Voltage Tests

All inputs are at 50 kHz.

Range Input

330 mV

330 mV

10 mV

190 mV

Minimum Reading

9.707 mV

188.573 mV

3.3 V

3.3 V

33 V

100 mV

1.9 V

1 V

0.0978 V

1.8852 V

0.9715 V

33 V

250 V

250 V

19 V

10 V

100 V

18.9085 V

9.755 V

99.35 V

Maximum Reading

10.293 mV

191.427 mV

0.1022 V

1.9148 V

1.0285 V

19.0915 V

10.245 V

100.65 V

Signametrics 120

3

4

5

6

Step

1

2

7

8

6.6 DC Current Test

The following procedure may be used to verify the accuracy of the DCI function:

1. If you have not done so, install the SMX2040 and place the covers back on to the computer. Ensure that the computer has been on for at least one-half hour, with the covers on, before conducting this test.

2. Remove all connections from the SMX2040 inputs. Select the DCI function, Autorange. Allow the SMX2040 to settle for a few seconds, and perform the Relative function.

3. Apply the following DC currents to the I,4

+ & - terminals. Check to see that the displayed reading on the

SMX2040 is within the indicated readings range.

Table 9-7. DC Current Test

Range Input Minimum Reading Maximum reading

3.3 mA

3.3 mA

33 mA

33 mA

330 mA

330 mA

2.5 A

2.5 A

0 mA (open)

1 mA

0 mA (open)

10 mA

0 mA (open)

100 mA

0 A

1 A

-0.0004 mA

0.9986 mA

-0.003 mA

9.987 mA

-0.060 mA

99.865 mA

-0.00035 A

0.99315 A

0.0004 mA

1.0014 mA

0.003 mA

10.013 mA

0.060 mA

100.135 mA

0.00035 A

1.00685 A

4

5

6

7

8

Step

1

2

3

6.7 AC Current Test

The following procedure may be used to verify the accuracy of the ACI function:

1. If you have not done so, install the SMX2040 and place the covers back on to the computer. Ensure that the computer has been on for at least one-half hour, with the covers on, before conducting this test.

2. Remove all connections from the SMX2040 inputs. Select the ACI function, Autorange.

3. Apply the following AC currents to the I,4

+ & - terminals. Check to see that the displayed reading on the

SMX2040 is within the indicated readings range.

Table 9-8. AC Current Test

All Inputs are at 400Hz

Range Input Minimum Reading Maximum reading

3.3 mA

3.3 mA

33 mA

33 mA

330 mA

330 mA

2.5 A

2.5 A

0.1 mA

1 mA

1 mA

10 mA

10 mA

100 mA

100 mA

1 A

0.09588 mA

0.9948 mA

0.9684 mA

9.954 mA

9.758 mA

99.56 mA

0.09535 A

0.9895 A

0.100412 mA

1.0052 mA

1.0316 mA

10.046 mA

10.242 mA

100.44 mA

0.10465 A

1.0105 A

121 Signametrics

3

4

5

6

7

Step

1

2

6.8 Capacitance Test (SMX2044 only)

The following procedure may be used to verify the accuracy of the Capacitance function.

1. If you have not done so, install the DMM and place the covers back on to the computer. Ensure that the computer has been on for at least one-half hour, with the covers on, before conducting this test.

2. Connect the DMM V,

Ω + & - terminals to the calibrator HI & LO Outputs. Attach the test leads to the DMM, leaving the other end open circuited. Allow the DMM to settle for a few seconds, and perform the Relative function. (This effectively nulls out the lead capacitance of your cabling.

3. Apply the following Capacitance values to the V,

+ & - terminals. Check to see that the displayed reading on the SMX2044 is within the indicated range of readings.

Range Input Minimum Reading Maximum reading

10

ηF 10

9.785

ηF

10.215

ηF

100

99

ηF

101

1 0.99

µF

1.01

µF

10 9.9

µF

10.1

100

99

µF

101

1 mF

10 mF

1 mF

10 mF

0.988 mF

9.8 mF

1.012 mF

10.2 mF

Signametrics 122

6.9 Frequency Counter Test (SMX2044 only)

The following procedure may be used to verify the accuracy of the Frequency Counter:

1. If you have not done so, install the DMM and place the covers back on to the computer. Ensure that the computer has been on for at least one-half hour, with the covers on, before conducting this test.

2. Select the ACV function, autorange. Turn freq on.

3. Apply the following AC voltages to the V,

+ & - terminals. Check to see that the displayed reading on the

SMX2044 is within the indicated range of readings.

Table 9-9. ACV Frequency Counter Test

2

3

4

5

6

Step

1

Range

330 mV

3.3 V

33 V

330 V

330 mV

33 V

Input

33 mV, 40 Hz

330 mV, 40 Hz

3.3 V, 40 Hz

33 V, 40 Hz

250 mV, 100 kHz

25 V, 100 kHz

Minimum Reading

39.9952 Hz

39.9952 Hz

39.9952 Hz

39.9952 Hz

99.996 kHz

99.996 kHz

Maximum reading

40.0048 Hz

40.0048 Hz

40.0048 Hz

40.0048 Hz

100.004 kHz

100.004 kHz

2. Select the ACI function, autorange. Turn freq on.

3. Apply the following AC currents to the I,4

+ & - terminals. Check to see that the displayed reading on the

SMX2040 is within the indicated range of readings.

Table 9-10. ACI Frequency Counter Test

Range Input Counter Reading Tolerance Step

1

2

3

3.3 mA

33 mA

330 mA

330 uA, 40 Hz

15 mA, 40 Hz

150 mA, 40 Hz

123 Signametrics

6.10 Calibration

Each SMX2040 DMM uses its own SM40CAL.DAT calibration file to ensure the accuracy of its functions and ranges. The SM40CAL.DAT file is a text file that contains the DMM identification number, calibration date, and calibration constants for all DMM ranges. For most functions, the calibration constants are scale factor and offset terms that solve the "y = mx + b" equation for each range An input "x" is corrected using a scale factor term "m" and an offset term "b"; this gives the desired DMM reading, "y". Keep in mind that for ranges and functions that are unavailable for a particular product in the SMX2040 family, the calibration record contains a place-holder. An example SM40CAL.DAT is shown: card_id 10123 type 2044 calibration_date 06/15/1999 ad ; A/D compensation

72.0 20.0 vdc ; VDC 330mV, 3.3V, 33V, 330V ranges, offset and gain parameters

-386.0 0.99961

-37.0 0.999991

-83.0 0.999795

-8.8 1.00015 vac

5.303

; VAC 1st line - DC offset. Than offset, gain and freq each range 330mV to 250V

0.84 1.015461 23

0.0043 1.0256 23

0.0 1.02205 0

0.0 1.031386 0 idc ; IDC 3.3mA to 2.5A ranges, offset and gain

-1450.0 1.00103

-176.0 1.00602

-1450.0 1.00482

-176.0 1.00001 iac ; IAC 3.3mA to 2.5A ranges, offset and gain

1.6 1.02402

0.0 1.03357

1.69 1.00513

0.0 1.0142

2w-ohm ; Ohms 33, 330, 3.3k,33k,330k,3.3M,33M,330Meg ranges, offset and gain

1.27e+4 1.002259

1256.0 1.002307

110.0 1.002665

0.0 1.006304

0.0 1.003066

0.0 1.001848

0.0 0.995664

0.0 1.00030

The first column under any function, e.g.,"

vdc

", is the offset term "b", expressed as a value proportional to analog-to-digital (a/d) counts. The second column is the scale factor term "m". Within each function, the "b" and

"m" terms are listed with the lowest range at the beginning. For example, under "2

w-ohm

"

above, "

1.27e+4

1.002259

"

represents the offset term for the 33

Ω range, and "

1.002259

" is the scale factor for this range. This record must be for the SMX2044 since the SMX2040 does not have the 33 Ohms range, and therefore these values will be set to 0.0 and 1.0.

For the ACV function, the first line in the calibration record is the DC offset value. The rest of the lines contain the

RMS offset, gain correction factor, and a third column that represents a digital code from 0 to 31 that controls the high frequency performance of each AC function. A large value, e.g., 31, implies high attenuation.

The SM40CAL.DAT file is created by performing external calibration. The general calibration algorithm consists of applying a zero value to the DMM followed by a value of 2/3 rd

of the top of each range. Calibration of your

SMX2040 is best performed using calibration software available from Signametrics.

When using multiple DMMs in a single chassis, the SM40CAL.DAT file must have a calibration record for each

DMM. You can combine the unique calibration records of each DMM into one SM40CAL.DAT file using any

ASCII text editor.

Signametrics 124

`

7.0 Warranty and Service

The SMX2040 is warranted for a period of one year from date of purchase.

If your unit requires repair or calibration, contact your Signametrics representative. There are no user serviceable parts within the SMX2040. Removal of any of the three external shields will invalidate your warranty. For inwarranty repairs, you must obtain a return authorization from Signametrics prior to returning your unit.

8.0 Accessories

Several accessories are available for the SMX2040 DMMs, which can be purchased directly from Signametrics, or one of its distributors or representatives. These include:

• Basic DMM probes

• DMM probe kit

• Deluxe DMM probe set

• Shielded SMT Tweezer Probes

• Multi Stacking Double Banana shielded cable 36”

• Multi Stacking Double Banana shielded cable 48”

• Mini DIN-7 Trigger, 6-Wire Ohms connector

• 4-Wire Kelvin probes

125 Signametrics

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