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Operator's Manual
Model SMU2055 6½ Digit USB Digital Multimeter
Corporation
April, 2010
Compatible with Rev 1.62 Hardware
CAUTION
In no event shall Signametrics or its Representatives be held 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 from of the use of or inability to use Signametrics products, even if Signametrics
Corporation 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 be applicable to you.
2008 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
3 Signametrics
Signametrics 4
5 Signametrics
1.0 Introduction
Congratulations! You have purchased a USB Digital Multimeter. The SMU2055 Digital Multimeter (DMM) has sophisticated analog and digital circuitry to provide repeatable measurements, and its protected to handle any unexpected situations your measurement environment may encounter. Your new DMM is easy to setup and use. To get years of reliable service from your DMM, please take a few moments to review this manual before installing and using this precision instrument.
This manual describes the SMU2055 USB module.
1.1 Safety Considerations
Safety Considerations
The SMU2055 DMM is capable of measuring up to 240 VDC or 240 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 set to the common mode voltage. These voltages can be lethal and may KILL!
The DMM comes installed in a plastic chassis with 4 components (bottom, top, front and back) that must
not be removed due to performance as well as safety reasons. Removal of these shields and/or improper assembly of the shields can expose lethal voltages. The plastic screws are required for safety reasons.
Warning
Check to see that all measurement wires are separated from the USB communication cable. If measurement wires come into contact with the USB cable, this may apply measurement voltages to
your computer, causing personal injury and/or damage to your computer!
When making any measurements above 50 VDC or 40 VAC, use only approved Safety Test Leads
such as Signametrics Basic Test Leads or Deluxe Test Leads, offered as optional accessories with the
Signametrics DMM’s.
1.2 Minimum Requirements
The SMU2055 DMMs are precision modules that are compatible with any USB 2.0 or higher computer port. A mouse must be installed when controlling the DMM from the Windows Control Panel. The SMU2055 comes with a Windows' DLL, for operation with Windows Version 95/98/Me/2000/XP, Vista and LINUX.
1.3 Feature Set
The SMU2055 is a traditional 6-1/2 digit DMM and can be used as a general purpose DMM. Signametrics also offers the high precision 7-1/2 digit USB DMM, the SMU2060, which adds capacitance measurements, triggered operation and a high resolution frequency counter. If your requirements call for a High Workload, then the Multi
Function SMU2064 will probably fit the ticket with its timing measurements, inductance, sourcing and higher speed. The SMU2064 specialized measurements can replace costly instruments and thus shrinking the size and cost of a test system.
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SMU2055 basic features:
Volts DC; four ranges, 240mV to 240V
Volts AC; TRMS; four ranges, 240mV to 240V
2-Wire Ohms, six ranges 240 to 24 M
4-Wire Ohms, six ranges 240 to 24 M
DC current, four ranges 2.4 mA to 2.4 A
AC current, four ranges 2.4 mA to 2.4 A
Diode V/I Five ranges, 100 A to 1mA
Auto range, Relative
Min/Max, dB and percent deviation functions
High Dynamic range; ±2,400,000 counts
Measurement rate selectable: 0.5 to250 readings/s
2.0 Specifications
The following specifications are based on both, verification of large number of units as well as mathematical evaluation. The specifications should be considered for the specified environment.
It is important to note that a specified range for a DMM is expressed as a numeric value indicating the highest absolute measurement that can be displayed using that range. The lowest value that can be detected is expressed by the corresponding resolution for the range.
2.1 DC Voltage Measurement
Input Characteristics
Input Resistance 240 mV, 2.4 V Ranges: >10 G, with typical leakage of 50pA
Input Resistance 24 V, 240 V Ranges: 10.00 M
Accuracy ± (% of reading + Volts) [1]
Scale
6-½ Digits
240 mV
2.4 V
24 V
240 V
240.0000 mV
2.400000 V
24.00000 V
240.0000 V
Resolution 24 hours
23 C 1C
100 V
1 V
0.003 + 2 V
0.003 + 3 V
90 Days
23 C 5C
0.005 + 3 V
0.004 + 4 V
One Year 23 C
5C
0.007 + 3.5 V
0.005 + 10 V
10 V 0.004 + 200 V 0.005 + 250 V 0.007 + 300 V
100 V 0.004 + 600 V 0.005 + 800 V 0.007 + 1 mV
[1] With reading rate set to < 2/sec, and within one hour from Self Calibration (S-Cal).
For resolution at higher measurement rates, see the following table. Use this table for DC Volts, DC
Current and Resistance measurements.
Maximum reading rate
1 / second
Digits of Resolution
6-1/2 22 bits
250 / second 5-1/2 18 bits
DCV Noise Rejection Normal Mode Rejection, at 50, 60, or 400 Hz ± 0.5%, is better than 95 dB for Rates of 6rps and lower. Common Mode Rejection (with 1 k lead imbalance) is better than 120 dB for these conditions.
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2.2 DC Current Measurement
Input Characteristics
Number of built-in shunts Two
Currents greater than 2.4A require external shunt
Protected with 2.5A Fast blow fuse
Accuracy ± (% of reading + Amps) [1]
Scale
Reading
2.4 mA 2.40000 mA
24 mA 24.0000 mA
240 mA 240.000 mA
2.4 A 2.40000 A
Burden
Voltage
10 A 25mV
100 A 250mV
1 A 55mV
24 hours
23 C 5C
90 Days
23 C 5C
One Year 23 C
5 C
0.05 + 300 A 0.06 + 700 A 0.07 + 1 A
0.05 + 350 A 0.065 + 800 A 0.08 + 1 A
0.05 + 50 A 0.055 + 60 A 0.065 + 80 A
10 A 520mV 0.3 + 60 A 0.4 + 70 A 0.45 + 90 A
[1] With reading rate set to < 2/sec, and within one hour from Zero (Relative control).
2.3 Resistance Measurements
Characteristics
Number of current sources Five
Maximum Test Voltage 2.4V
2.3.1 2-wire
Accuracy ± (% of reading + ) [1]
240
2.4 k
24 k
6 ½ Digits
240.0000
2.400000 k
24.00000 k
240 k 240.0000 k
2.4 M
24 M
2.400000 M
24.0000 M
Resolution Source
100 current
1 mA
24 hours
23 C 1C
90 Days
23 C 5C
One Year
23 C 5C
0.004 + 4.5 m [2] 0.005 + 5 m [2] 0.008 + 6 m [2]
1 m 1 mA 0.0025 + 28 m
10 m 100
0.004 + 32 m 0.007 + 33 m
0.004 + 330 m 0.007 + 350 m
100 m
1
100
10
1
0.008 + 3.2
0.02 + 40
100 nA 0.2 + 400
0.012 + 4
0.03 + 50
0. 3 + 500
0.02 + 5
0.04 + 70
0.4 + 600
[1] With reading rate set to < 2/sec, and within one hour from Self Calibration (S-Cal).
[2] Use of S-Cal and Relative to improve measurement floor.
2.3.2 4-wire
Accuracy ± (% of reading + ) [1]
Range
[3]
Full Scale
6 ½ Digits
Resolution Source current
24 hours
23 C 1C
240 240.0000 100
2.4 k 2.400000 k 1 m
1 mA
1 mA
0.004 + 3 m
90 Days
23 C 5C
One Year
23 C 5C
[2] 0.005 + 4 m [2] 0.008 + 5 m [2]
0.0025 + 28 m 0.004+ 32 m 0.007 + 33 m
24 k 24.00000 k 10 m 100 0.004 + 330 m 0.007 + 350 m
240 k 240.0000 k 100 m 10 0.008 + 3.2 0.012 + 4 0.02 + 5
[1] With reading rate set to < 2/sec, and within one hour from Self Calibration (S-Cal).
[2] Use of Relative to facilitate indicated floor.
[3] The 2.4MΩ and 24MΩ ranges are functional but not specified for 4-Wire operations.
2.4 AC Voltage Measurements
Input Characteristics
Input Resistance 1 M, shunted by < 300 pF
Max. Crest Factor 4 at Full Scale, increasing to 7 at Lowest Specified Voltage
AC coupled Specified range: 10 Hz to 200 kHz
Typical Settling time < 0.5 sec to within 0.1% of final value
Common Mode rejection: at 50Hz to 60Hz, 1 k imbalance in either lead, is better than 60 dB.
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2.4.1 AC Voltage True RMS Measurement
Range [1]
240 mV
2.4 V
24 V
240 V
Full Scale 6-½ Digits
240.0000 mV
2.400000 V
24.00000 V
240.0000 V
Lowest specified Voltage
5 mV
20 mV
200 mV
2 V
Resolution
100 V
1 V
10 V
100 V
[1] 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.
2.4.2 AC Volts Accuracy
Settles to rated accuracy within 0.5 seconds for signals >50% of scale.
May take up to 2s to settle to rated accuracy for signals < 5% of scale.
Accuracy ± (% of reading + Volts) [1]
Range Frequency
240 mV
2.4 V
24 V
240 V
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 1C
3 + 300 V
0.45 + 150 V
0.13 + 100 V
0.3 + 180 V
2 + 0.6 mV
3 + 2 mV
0.45 + 1.3 mV
0.07 + 1 mV
0.35 + 2 mV
2+ 2.5 mV
4 + 25 mV
0.50 + 20 mV
0.07 + 15 mV
0.2 + 25 mV
1.5 + 35 mV
3 + 250 mV
0.45 + 230 mV
0.07 + 180 mV
0.28 + 250 mV
1.5 + 350 mV
90 Days
23 C 5C
3.4 + 500 V
0.47 + 170 V
0.14 + 110 V
0.35 + 220 V
2.1 + 0.8 mV
3.3 + 2.2 mV
0.47 + 1.5 mV
0.075 + 1.1 mV
0.37 + 2.3 mV
2.1 + 2.8 mV
4.3 + 16 mV
0.55 + 25 mV
0.075 + 20 mV
0.25 + 30 mV
1.6 + 28 mV
3.1 + 350 mV
0.+ 300 mV
0.075 + 220 mV
0.29 + 300 mV
1.6 + 400 mV
One Year
23 C 5C
3.6 + 0.6 mV
0.5 + 0.35 mV
0.16 + 0.25 mV
0.4 + 0.35 mV
2.2+ 1 mV
3.5 + 2.5 mV
0.5 + 1.7 mV
0.08 + 1.2 mV
0.4 + 2.5 mV
2.2 + 5 mV
4.5 + 35 mV
0.65 + 30 mV
0.085 + 23 mV
0.3 + 35 mV
1.7 + 50 mV
3.3 + 400 mV
0.+ 350 mV
0.08 + 250 mV
0.55 + 350 mV
1.8 + 500 mV
[1] With reading rate set to ≤ 2/sec
ACV Noise Rejection Common Mode rejection, for 50 Hz or 60 Hz with 1 k imbalance in either lead, is better than 60 dB.
Specs in red indicate change from last manual release.
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2.5 AC Current Measurement, True RMS
Input Characteristics
Crest Factor 4 at Full Scale
Number of built-in shunts Two
Currents greater than 2.4A require external shunt
Protected with 2.5A Fast blow fuse
2.5.1 AC Current True RMS Measurement
Range
2.4 mA
24 mA
240 mA
2.4 A
Full Scale 6 1/2 Digits
2.400000 mA
24.00000 mA
240.0000 mA
2.400000 A
Lowest Specified
Current
60 A
300 A
3 mA
30 mA
Maximum Burden
Voltage (RMS)
55mV
520mV
Resolution
100 nA
1 uA
Accuracy ± (% of reading + Amps)
Range Frequency [1]
2.4 mA
24 mA
240 mA
2.4 A
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
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
24 hours
23 C 1C
3.8 + 4 A
0.9 + 4 A
0.04 + 1.5 A
0.12 + 4 A
1.8 + 30 A
0.6 + 30 A
0.07 + 10 A
0.21 + 30 A
1.8 + 400 A
0.6 + 400 A
0.1 + 100 A
0.3 + 300 A
1.8 + 4 mA
0.66 + 4 mA
0.3 + 3.8mA
0.4 + 4mA
90 Days
23 C 10C
2.7 + 4 A
0.9 + 4 A
0.08 + 3 A
0.14 + 4 A
2.6 + 30 A
0.9 + 30 A
0.15 + 20 A
0.3 + 40 A
2.7 + 400 A
0.9 + 400 A
0.17 + 180 A
0.35 + 350 A
2.5 + 4.5 mA
0.8 + 6 mA
0.33 + 3.8 mA
0.45 + 4.5 mA
One Year
23 C 10C
2.9 + 4 A
1.0 + 4 A
0.12 + 4 A
0.22 + 4 A
2.8 + 30 A
1.0 + 30 A
0.16 + 30 A
0.4 + 40 A
2.8 + 400 A
1.0 + 400 A
0.2 + 220 A
0.4 + 400 A
2.7 + 5 mA
0.9 + 6 mA
0.35 + 4 mA
0.5 + 5 mA
2.6 Diode Test Function
Test Currents Five
Current sources voltage compliance 4 V
Accuracy ± (% of reading + Volts) [1]
Resolution One Year 23 C 10C
0.1 A
1 A
10 A
100 A
1 mA
5-½ Digits
2.40000 V 10 V
0.022 + 15 V
0.018 + 12 V
0.015 + 10 V
0.014 + 8 V
0.014 + 8 V
[1] With measurement rate set to 2rps or lower rate
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2.7 Measurement Rates Control
Use DMMSetRate() using the following codes.
Rate
(Readings/sec)
0.5
Symbol Code Power line Rejection
RATE_p5 0
50Hz 60Hz 400Hz
3
2.8 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, Self Calibration must be performed once a day or as indicated in the specification table. This is a simple software operation that takes a few seconds. It can be performed by calling Windows command DMMCal(), or selecting S-Cal in the Control Panel.
These products are capable of continuous measurement as well as data transfer rates of up to 250 readings per second (rps). In general, to achieve 6-1/2 Digits of resolution, the rate should be set to 2rps or lower.
Since the DMM is powered via a USB calbe (AM/BM 6’ cable), it is important to make sure it gets the required 5V supply. Using the right USB cable is very important. Make sure this cable has a 24 AWG wires for power supply, indicated by marking on the cable such as 28/1P + 24/2C. Be aware that there are a lot of cables which are marked 28/1P + 28/2C. These have high resistance, and will not be adequate.
Another issue can be with powered USB hubs. Some of the lower quality units can have upwords of 8V rather than the required 5V +/-5%. On initialization (DMMInint) the DMM measures its internal supply voltage and returnes an error or warning code if the power is inadequate. See DMMGetSupplyV function.
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2.9 Other Specifications
Temperature Coefficient
Size
Less than 0.1 x accuracy specification below 18 C and over
28 C
Hardware Interface
Overload Protection (voltage inputs)
Isolation
Temperature Range Operating
250 VDC, 250 VAC
300 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).
Safety
Calibration
Designed to IEC 1010-1, Installation Category II.
Calibrations are performed by Signametrics in a computer at
23 C internal temperature rise. All calibration constants are stored in an onboard memory and in a text file.
-10 C to 65C
Temperature Range Storage -40 C to 85C
Single 3U USB or CompactPCI slot
Note: Signametrics reserves the right to make changes in materials, specifications, product functionality, or accessories without notice.
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2.10 Accessories
Several accessories are available for the SM2060 series DMMs, which can be purchased directly from Signametrics
Corp, or from one of its approved distributors or representatives. Some of the accessories available:
DMM Probes SM-PRB ($15.70)
6 ft. USB 2.0 AM/BM cable SMU-CBL6ft
3 ft. USB 2.0 AM/BM cable SMU-CBL3ft
10 ft. USB 2.0 AM/BM cable SMU-CBL10ft
DMM Probe kit SM-PRK ($38.50)
Deluxe Probe kit SM-PRD ($95.00).
Shielded SMT Tweezers 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).
Lab View VI’s library SM204x.llb (free).
Linux Driver kit (free).
Extended 3 Year warrantee (calibration not included) $120.00 for SM2055.
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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 package includes the Digital Multimeter; Installation CD, a Floppy Disk containing the calibration and verification records, 6’ USB cable and Certificate of Calibration.
3.1 Setting the DMM
The DMM is provided with plug-and-play installation software, and does not require any switch settings, or other adjustments prior to installation.
3.2 Installing the Software.
Before connecting the DMM Hardware, it is necessary to install the DMM software. Insert the
Signametrics Product Installation CD into your CD drive. A menu will appear automatically on most computers. Otherwise, double-click on the autorun.exe file in the root directory of the Installation CD.
A menu will appear, allowing you to choose which Signametrics product to install. Select the product you would like to install, "SMU2055/2060/2064 USB DMMs". A Software Setup Wizard will begin.
Follow the installation process, selecting which components you would like installed, and where they should be installed. The Hardware Driver and the Front Panel are required components to run and test the product. On the last page of the wizard, click Install.
After the software has been installed, The Signametrics USB Driver Wizard will appear. Click "next". A windows message may appear asking if you are sure you wish to install this driver. Continue the installation. Afterwards, you should now see a screen that indicates the drivers have been sucsessfully installed on this computer.
3.3 Installing the DMM Module
Warning
To avoid shock hazard, install the DMM only into a personal computer that has its power line connector connected to an AC receptacle with an Earth Safety ground.
Use extreme care when plugging the DMM module(s) into a USB port on your computer. Make sure no cable is connected to the front panel of the DMM while you plug it into the USB port.
Connect the SMU2055/2060/2064 to one of the USB ports on your computer. On Windows 2000, XP, or
Vista a "Found New Hardware" Wizard dialog box should appear. On Windows 7, the drivers may automatically be detected and installed without a Found New Hardware Wizard Appearing.
The Wizard asks "Can Windows connect to Windows Update to search for software?" Select "No, not this time" and click on "Next". Select "Install the software automatically" and click on "Next". Windows should be able to find the drivers automatically since they were copied to the system (section 3.2).
Windows may double check whether you want to install the software. If this is the case, click "Continue
Anyways". The Wizard should say "The wizard has finished installing software for: [multimeter product name]". Click "Finish" to complete the installation.
3.4 Calibration File
The SM60CAL.DAT file supplied with your DMM has a unique calibration record for that DMM (See
"Calibration" at the end of this manual.). In most cases, the installation of the calibration file is handled automatically by the DMM software.
Signametrics 14
A copy of the calibration file resides on an EEProm on the DMM and is copied to your computer the first time you use the instrument. A backup copy of the calibration file is included on a diskette that comes with the DMM.
The default location of the Calibration File is “C:\SM60CAL.DAT”. If your system uses multiple
DMMs, the software will append the Calibration Records of each DMM into a single SM60CAL.DAT file. The SM60CAL.DAT file is a text file, and can be opened using a text editor such as Notepad, should it be necessary.
3.5 DMM Input Terminals
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 computer or application may result.
Figure 3-1. The DMM input connectors consist of four Banana jacks.
V, 2 + This is the positive terminal for all Volts, 2-Wire Resistance and diode test. When in 4-Wire resistance measurement mode, it serves as the positive terminal of the current source. The maximum input across V, 2 + and V, 2 - is 240 VDC or 240 VAC.
V, 2 - This is the negative terminal for all Volts, 2-Wire Resistance and diode test. When in 4-Wire resistance measurement mode, it serves as the negative terminal of the current source. Do not float this
terminal or any other DMM terminal more than 240 VDC or 240 VAC above Earth Ground.
I , 4 + This is the positive terminal for all Current measurements. While in 4-Wire resistance measurement mode it is the high sense. The maximum input across I, 4 + and I, 4 - is 2.5 A. Do not apply more than 5 V peak across the I,4 + and I,4- terminals.
I,4 - This is the negative terminal for Current measurements. While in 4-Wire resistance measurement mode it serves as the low sense. 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.
The I,4 - Current function is protected by a 2.5 A, 250 V Fast Blow fuse (PCT type).
3.6 DMM Rear Panel
The rear panel includes various compliance and warning text and graphics, the unit serial number, its modle number and the installed options. The USB connector provides for both, compueter interface and power to run the DMM..
15 Signametrics
Figure 3-2. The Rear panel has the USB BF type connector. Compatible with BM cable.
3.7 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, StartSMU2060 Series
MultimetersSMU2064 Multimeter. 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 SM60CAL.DAT file does not correspond to the installed DMM.
When the DMM is started for the first time, it takes a few extra seconds to extract its calibration data from the on-board memory, and write it to the calibration file C:\SM60CAL.DAT
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 SMU2055 front panelstarts up in DCV, and 240 V range. If the DMM is operated in
Autorange, with an open input, it will switch between the 2.4V and 24V ranges every few seconds, as a range change occurs. This is perfectly normal wth high end DMM’s such as the SM2055. This phenomenon is caused by the virtually infinite input impedance of the 2.4V DC range. 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 SM2055 will change ranges, causing the range switching. This is normal.
3.8 Using the Control Panel
Figure 3-2. The Control Panel. The two main groups include Measurement Function and Range buttons.
The Range buttons are context sensitive such that only “240m, 2.4, 24 and 240 appear when in a Voltage
Measurement Function is selected, and 2.4m, 24m, 240m and 2.4 appear when a Current Measurement
Function is selected, etc.
Signametrics 16
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. The software command language provides a powerful set of capabilities. Some of the functions are not included in the control panel, but are in the software.
DC/AC This function switches between DC and AC. This is applicable for the Voltage and Current
DMM functions.
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 . For example, when using 2W, 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 V 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 internal offsets. The Relative button can also be used in the Percent and dB deviation displays (shown below), which are activated using the Tools in the top menu.
Rate Box: Controls the DMM Measurement rate. As rate decreases, the measurement noise decreases.
Also consider the power line frequency (50/60 Hz) of operation when setting it, as certain rates have better noise rejection at either 50 or 60 Hz. (See “Specifications” for details.). When measuring VAC values, there is no point setting the Rate to a value greater than 2rps.
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. Autorange is not recommended
for automated test applications 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 240 mV and 2.4 V ranges have virtually infinite input impedance, while the 24 V and 240 V ranges have 10 M 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 accuracy specifications. It is recommended 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. This function takes 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.
17 Signametrics
4.0 DMM Operation and Measurement Tutorial
Most of the 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 DMM, 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 V to 240 VDC or VAC. Use the V, 2+ and V, 2- terminals, being certain to always leave the I,4 + and I,4- 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 (<1 mV), you should first place a copper wire shorting plug across the V, 2 + and V, 2 - terminals and perform Relative operation to eliminate zero errors.
A common source of error can come from your test leads, which can introduce several Volts 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 front panel powers up in 2rps, DCV, 240 V range. If the DMM is operated in Autorange, with an open input, The DMM will keep changing ranges. This is perfectly normal with ultra high impedance
DMM’. The virtually infinite input impedance of the 240 mV and 2.4 V DCV ranges causes this phenomenon. On these ranges, an open input will read whatever charge is associated with the signal conditioning of the DMM. As this electrical charge accumulates, the DMM will change ranges.
4.1.2 True RMS AC Voltage Measurements
ACV is specified for signals greater than 1mV, from 10 Hz to 50 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 DMM 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 V,2 - terminal. This prevents any “Common Mode” problems from occurring (Common Mode refers to floating the DMM V,2 - above Earth Ground.) Common Mode problems can result in noisy readings, or even cause the PC 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.
The settling time and low frequency limits of the RMS functions (AC Voltage and current) are effected by both, the value of the input as a percentage of range, and the frequency of the signal.
Take into account the amount of time it takes for the RMS circuit to settle. With a setteling time of 0.5s, you may use a measurement rate of 2 readings/s and take two readings. The first will provide the 0.5s to settele, and the second will make a stable reading. Do not average since the first reading will introduce an error.
For improved accuracy and stability while measuring low frequency signals, the measurement time
(1/rate) should be at least ten (10) times the period of the measured signal.
4.2 Current Measurements
The DMM measures AC and DC currents between 100 A and 2.5 A. Use the +I, 4W terminals, being certain to always leave all other terminals disconnected. Use the AC/DC button to switch between AC and DC. The AC current is an AC coupled True RMS measurement function. See figure 4-2 for connection.
Signametrics 18
The Current functions are protected with a 2.5 A, 250 V fuse internal to the DMM. The 2.4mA and 24mA ranges utilize a 10 shunt, while the 240mA and 2.4A ranges use a 0.1 shunt. In addition to the shunt resistors, there is some additional parasitic resistance in the current measurement path associated with the fuse and the internal wiring. The maximum burden voltage is about 250mV.
Warning! Applying voltages greater than 35 V to the I+, I- terminals can cause personal injury and/or damage to your DMM! Think before applying any inputs to these terminals!
4.2.1 Improving DC Current Measurements
When making sensitive DC current measurements disconnect all terminals not associated with the measurement. User the Relative function while in the desired DC current range to zero out any residual error. Using the S-Cal (DMMCalibrate ()) prior to activating Relative will improve accuracy further.
Although the DMM is designed to withstand up-to 2.4A indefinitely, be aware 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 recommended that whenever practical, higher current measurements be limited to short time intervals.
4.3 Resistance Measurements
The key for stable and accurate Resistance measurements, with low test voltage, is in the number of current sources used. This DMM uses five. The V, 2 + provides the positive terminal and the V, 2- negative terminal of the current source. The DMM measures resistance by forcing a current, and measuring a voltage, which the DMM converts and displays as a resistance value. Most measurements can be made in the 2-wire mode. The 4-wire ohms is used to make low value resistance measurements.
All resistance measurement modes are susceptible to Thermo-Voltaic (Thermal EMF) errors. See section
4.3.5 for details.
4.3.1 2-Wire Ohm Measurements
In the 2-Wire resistance measurement the DMM sources current and measure resuting voltage. The DMM measure Resistance using six ranges; 240 to 24 M. Use the V,2+, V,2- terminals for this function.
Disconnect the I,2 + and I,2- terminals in order to reduce error due to leakage and noise, as well as better safety.
If the resistor to be measured is less than 24 k , you may null out any lead resistance errors by first shorting the ends of the V,2 + and V,2- test leads together and performing a Relative operation
(DMMSetRelative under program control). Making measurements above 200 k , you should consider shielded or twisted leads to minimize noise pickup. Further improvement can be achieved using guarding
(section 4.3.5).
It is a good idea to be aware of the test voltages, particularly when measuring a circuite that includes semiconductors. To reduce this voltage, select a higher resistance range (lower current). For instance, measuring 10k resistor using the 24k range (100uA), results in 1V test voltage, which will turn on semiconductor junctions, resulting in lower resistance reading. To avoid this error, select the 240k range
(10uA), which will result in 100mV and will read the 10k a lot more accurately (see section 2.3 for resistance ranges vs. current). For characterizing semiconductor part types, use the Diode measurement function.
For applications requiring voltage and current controlled resistance measurements, use the SMU2064, which has Extended Resistance Measurement function as well as active guarding.
4.3.2 4-Wire Ohm Measurements
4-wire Ohms measurements are advantageous for making measurements below 200 k , eliminating lead resistance errors. The V,2 + and V,2- terminals apply a current source stimulus to the resistance, and the I,4 + and I,4- 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.
19 Signametrics
4-wire Ohm makes very repeatable low ohms measurements, from 10 m to 200 k. It is not recommended to use 4W when making measurements above 200 k.
Figure 4-1. The I,4 + and I,4- sense leads should be closest to the body of the resistor when making 4-
Wire resistance measurements.
4.3.3 Effects of Thermo-Voltaic Offset
Resistance measurements are sensitive to Thermo-Voltaic (Thermal EMF) errors. These error voltages can be caused by poor test leads, relay contacts and other elements in the measurement path. They affect all measurement methods, including 2-Wire and 4-Wire. 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, and it is not uncommon to find relays that have more than 50 V. With several relay contacts in the path, the error can be significant. This error can be measured using the DMM’s 240mV 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). Multiply this count by the Thermal EMF voltage. Use Ohms law to convert this voltage to resistance error as in the following table.
Range Ohms
240
Current
1 mA
2.4 k 1 mA
DMM
Resolution
0.1m
10 m 1
1 m
Error due to
10 V EMF
10
Error due to
100 V EMF
Error due to
1mV EMF m 1
24 k 100 uA 10 m 100
240 k 10 uA 0.1 1
2.4 M 1 uA 1 10
24 M 100 nA 10 100 k 100
Figure 4-2. Resistance measurement errors contributed by Thermo-Voltaic offset.
4.4 Diode Characterization
The Diode measurement function is used for characterizing semiconductor part types. This function is designed to display a semiconductor device’s forward or reverse voltage. The DMM forces a current and measures voltage drop. The available source currents for diode I/V characterization include five DC current values, 100 A, 1 A, 10 A, 100 A and 1 mA. The maximum diode voltage that can be measured with this function is 2.4V. For higher voltages see the leakage test function.
Applications include I/V characteristics of Diodes, LEDs, Low voltage Zener diodes, Band Gap devices, as well as IC testing and polarity checking.
Signametrics 20
5.0 Windows Interface
The SMU2060 Windows interface package provided, contains all required componenets for the following products: SMU2055, SMU2060 and SMU2064. It is a 32bit DLL based modules, which includes windows Kernel driver. This package is sufficient for most windows based software applications.
5.1 Distribution Files
The distribution CD contains all the necessary components to install and run the DMM on computers running any of the Microsoft® Windows™ operating systems. It also provides means for various software packages to control the DMM. Before installing the DMM or software, read the “Readme.txt” file. To install this software "Run Program" menu select ‘autorun.exe’ from the provided CD by doubleclick. Most files on this CD are compressed, and are automatically installed by running ‘autorun’, which in turn executes the setup.exe file located on the CD in the respective product directory.
The DLL is a protected-mode Microsoft® Windows™ DLL that is capable of handling up to ten
Signametrics DMM’s. Also provided are samples Visual Basic™ front-panel application and a C++ sample, to demonstrate the DMM and the interface to the DLL. Check the README.TXT file for more information about the files contained on the diskette. Some important files to note are:
File
SM60CAL.DAT
SMU2060.LIB
SMU2060.DLL
Description
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 the first time the DMM is used. It may contain calibration records for several DMM’s.
The Windows import library. Install in a directory pointed to by your
LIB environment variable.
The 32-bit driver DLL. This should be installed either in your working directory, in the Windows system directory, or in a directory on your
PATH. The installation program installs this file in your Windows system directory (usually C:\WINDOWS\SYSTEM for Win98/95 or
at C:\WINNT\SYSTEM32 for Windows NT).
SMU2060.H 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.
USBDMMUser.H Header file containing all of the necessary DMM’s function, range, rate definitions to be used with the various measure and source functions.
The file SM60CAL.DAT contains calibration information for each DMM, and determines the overall analog performance for that DMM. The first time you startup your DMM, this file will be created from the stored calibration data on-board the 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 8123 type 2055 calibration_date 06/15/2005
72.0 20.0 1.0 vdc ; VDC 240mV, 2.4V, 24V,… 330V ranges. 1 st
entry is Offset the 2 nd
is gain parameters
-386.0 0.99961
-37.0 .999991
-83.0 0.999795
-8.8 1.00015
0 vac
1.0 ;Place holder on SMU2055
; VAC 1st line - DC offset. Subsequent lines: 1 st
entry is Offset the 2 nd
is gain, 3 rd
freq. comp
21 Signametrics
0.0
0.84
0.0043
1.015461 23
1.0256 22
0.4 1.031386 1
0 idc
1.0 0
; IDC 240nA to 2.5A ranges. 1 st
;Place holder on SMU2055
entry is offset, 2 nd
is gain parameter
0 1.0 ;Place holder on SMU2055
0 1.0
0 1.0
0 1.0
;Place holder on SMU2055
;Place holder on SMU2055
;Place holder on SMU2055
; 2.4mA range -10.0 1.00083
-16.0 1.00222
-50.0 1.0034
-176.0 1.0 ; 2.4A range iac ; IAC 2.4mA to 2.4A ranges, offset and gain
1.6 1.02402
0.0 1.03357
1.69 1.00513
0.0 1.0142
2w-ohm ; Ohms 24, 240, 2.4k,...,240Meg ranges, offset and gain
1256.0
110.0
1.002307
1.002665
0.0 1.006304
0.0 1.003066
0.0 1.001848
;240 Ohms range
…
The first line identifies the DMM and the calibration date. The "card-id" is stored on each DMM. During initialization the driver reads it from the DMM and matches it to that in the calibration record.
During initialization (DMMInit()), the driver reads various parameters such as DMM type (SM2060/55/64), and serial number, and then reads the corresponding calibration information from the SM60CAL.DAT file.
The DMMInit() function reads the information from these files to initialize the DMM. DMMInit accepts parameters that are the names of these files. A qualified technician may modify individual entries in the calibration file, then reload them using the DMMLoadCalFile command.
5.2 Using the SMU2060 Driver Set With C++ or Similar Software
The SMU2055 uses the SMU2060 driver package. Install the SMU2060.H and USBMMUser.H header file in a directory that will be searched by your C/C++ compiler for header files. This header file is known to work with
Microsoft Visual C++™. To compile using Borland, you will need to convert the SMU2060.DEF and
SMU2060.LIB using ImpDef.exe and ImpLib.exe, provided with the compiler. Install SMU2060.LIB in a directory that will be searched by the linker for import libraries. The SMU2060 software must be installed prior to running any executable code. Install the SMU2060.DLL in a location where either your program will do a
LoadLibrary call to load it, or on the PATH so that Windows will load the DLL automatically.
In using the SMU2060 driver, first call DMMInit which read the calibration information, performs self test and auto-calibration. Call DMMSetFunction to set the DMM to a measurement function. The DMM function constants are defined in the DMMUser.H header file, and have names that clearly indicate the function they 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) result, and DMMReadStr returns the next reading as a formatted string ready to be displayed.
All functions accept a DMM-number parameter. This value, nDmm, is used to identify the DMM number in a multiple DMM system. This value will be 0,1,2.. n. Most functions return an error or warning code, which can be retrieved as a string using DMMErrStr().
Signametrics 22
5.3 Visual Basic Front Panel Application
The Visual Basic front panel application, SMU2064.EXE, is an interactive control panel for the SM2060 family of
DMMs. When it loads it will take a few seconds to initialize and self calibrate the hardware before the front panel is displayed.
The push buttons labeled V, I, etc. control the DMM function. As you push a function, the front panel application will switch the DMM to the selected range and function. Autorange mode is selected by pushing the AutoRange check box. The S-Cal box recalibrates the DMM, leaving the DMM in the same state prior to operation. (This is an internal calibration only, and is different from the external calibration, which writes to the SM60CAL.DAT file.
S-Cal is used to correct for any internal offset and gain drifts due to changes in operating temperature).
The source code file 2060Glbl.BAS (in the V_BASIC directory of the distribution diskette) contains the function declarations and the various ranges, rates and other parameters that are required. These definitions are the duplicates of the “C” header files required to write Visual Basic applications which interact with the driver DLL, along with some global variables required for this particular front-panel application.
5.3.1 Visual Basic Simple Application
The following is a simple panel application for Visual Basic, which includes two files, Global.Bas and
SimplePanel.frm. It has a panel that contains two objects, a Text Box to display the DMM readings, and a
Command Button that acts as a reading trigger.
Global.bas module file contents:
Option Explicit
' Declare all functions we are going to be using: From SMU2060.H file.
Declare Function DMMInit Lib "SM2060.dll" (ByVal nDmm as long, ByVal calFile As String) As Long
Declare Function DMMSetRate Lib "SM2060.dll" (ByVal nDmm As Long, ByVal nRate As Long) _
As Long
Declare Function DMMSetFunction Lib "SM2060.dll" (ByVal nDmm As Long, ByVal nFunc As Long) As Long
Declare Function DMMSetRange Lib "SM2060.dll" (ByVal nDmm As Long, ByVal nRange As Long) As Long
Declare Function DMMRead Lib "SM2060.dll" (ByVal nDmm As Long, dResult As Double) As Long
' Definitions from DMMUser.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
Global Const Range1 = 1
Global Const Range2 = 2
Global Const Range3 = 3
'Measurement Rate for use with DMMSetRate()
Global Const RATE_1R60= 4 '1rps with 60Hz line rejection
Global Const RATE_1R50 = 5 '1rps with 50Hz line rejection
Global Const RATE_2R60= 6 '2rps
Global Const RATE_4R60 = 8 '4rps
Global nDmm As Long ' Global store for the DMM number
SimplePanel.frm Form file contents:
Private Sub Form_Load() 'Fomr_Load allways gets executed first.
Dim i As Long
nDmm = 0 ‘Set to first DMM in the system
i = DMMInit(nDmm,"C:\SM60CAL.dat") 'Initialize and load cal file
i = DMMSetFunction(nDmm, VDCFunc) 'Set DMM to DCV function
i = DMMSetRange(nDmm, Range2) 'Select the 24V range
i = DMMSetRate(nDmm, RATE_2R60) 'Set measurement rate
End Sub
23 Signametrics
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
After initialization, the Windows DLL default modes and parameters on your DMM are set up as follows:
Auto ranging: Off
Function: DC Volts
Range: 240V
Relative: Off
Measurement Rate: 2rps
5.5 Using the DLL with LabWindows/CVI
When using the SM2060 DLL with LabWindows/CVI, you should read the LabWin.txt file included with the software diskette.
An example application of SM2060 DLL calls from LabWindows/CVI ® is shown below. It contains functions measure_ohms() and measure_vdc(), with sample calls to the SM2060.
NOTE: Although these measurement functions use LabWindows/CVI® and the LabWindows/CVI(R)
Test Executive, they are not necessarily coded to LabWindows® instrument driver standards.
/* function: measure_ohms, purpose: measure 2-wire ohms */ int measure_ohms(double OHMreading) { short ret, i;
DMMSetFunctions (0, OHMS2W);
DMMSetAutoRange (0, TRUE);
/* to settle auto-range and function changes ignore three readings */ for( i = 0 ; i < 4 ; i++ ) ret = DMMReadNorm (0, & OHMreading);
}
/* function: measure_vdc, purpose: measure DC Volts */ int measure_vdc(double Vreading) { short ret, i;
DMMSetFunctions (0, VDC);
DMMSetAutoRange (0, TRUE);
/* to settle auto-range and function changes ignore three readings */ for( i = 0 ; i < 4 ; i++ ) ret = DMMReadNorm (0, &Vreading); return ret; }
5.6 Windows Command Language
The following section contains detailed descriptions of each function of the Windows command language. Those commands that pertain to only the SM2060 are indicated. Most functions return an error code. The code can either be retrieved as a string using DMMErrString function, or looked up in the SMU2060.H header file. The
DMMUser.H file contains all the pertinent definitions for the DMM ranges functions etc. The following description for the various functions is based on “C” function declarations. Keep in mind that the Windows DLL containing these functions assumes all int values to be windows 32bit integers (corresponds to VisualBasic long type). TRUE is 1 and FALSE is 0 (which is also different from VisualBasic where True is –1 and False is 0).
Grayed out functions are either, untested or unimplemented.
Signametrics 24
DMMCalibrate
Description Internally calibrate the DMM.
#include "SMU2060.H"
Remarks
nDmm
This function performs self calibration of the various components of the DMM, as well as an extensive self test. At the end of this operation it returns the DMM to the current operating mode. Using this function periodically, or when the DMM internal temperature varies, will enhance the accuracy of the DMM. Using this function does not remove the requirement to perform periodic external calibration.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value
Value
The return value is one of the following constants.
DMM_OKAY
Negative Value
Meaning
DMM is OK.
Error
Example
Comments status = DMMCalibrate(0); /* a quick internal cal.*/
This performs an internal DMM calibration and is the same as the S-Cal command in the
VB Control Panel. It is not related to the external calibration represented in the
SM60CAL.DAT file.
DMMCleanRelay
Description Service function that cleans specified relay.
#include "SMU2060.H"
Remarks
Return Value iRelay
This function cleans iRelay by vibrating the contact iCycles times. This function is useful for removing oxides and other deposits 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
int The relay to clean. 1 for K2, 2 for K2 and 3 for K3. iCycles
nDmm
int The number of times the relay contact is shaken. 1 to 1000.
int Identifies the DMM. DMMs are numbered starting with zero.
Integer error code..
25 Signametrics
Value Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
Example
Example int status = DMMCleanRelay(0, 2, 100); // Shake K2 1000
DMMClearMinMax
Description Clears the Min/Max storage.
#include "SMU2060.H"
DMMClearMinMax(int
Remarks
nDmm
This function clears the Min/Max values, and initiates a new Min/Max detection. See
DMMGetMin for more details.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value Integer error code..
Value Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code int status = DMMClearMinMax(0);
DMMCloseUSB
Description Close the USB bus for the specified DMM. Not for user applications.
#include "SMU2060.H"
Remarks
nDmm
This function is limited for servicing the DMM. It has no use in normal DMM operation.
See also DMMOpenUSB() function.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value
Value
Integer error code.
Meaning
DMM_OKAY Operation successfully completed.
Signametrics 26
Negative Value Error code
Example
DMMDelay
int status = DMMCloseUSB(0);
Description Wait for a given time.
#include "SMU2060.H"
int DMMDelay(double dTime)
Remarks dTime seconds. dTime must be a positive double number between 0.0 and 100.0 seconds.
Parameter Type/Description
dTime double Delay time in seconds.
Return Value
Value
The return value is one of the following constants.
DMM_OKAY
Negative Value
Meaning
Operation successfully terminated
Error code
Example DMMDelay(1.2); /* wait for 1.2 sec */
DMMErrString
Description
Remarks
Return the string describing the warning or error code.
#include "SMU2060.H"
int DMMErrString(int iErrorCode, LPSTR lpszError, int iBuffLength)
This function returns a string containing the error or warning description which corresponds to the iErrorCode. The string is placed at lpszError. Error codes are negative numbers, while warning codes are positive numbers.
Parameter
iErrorCode
Type/Description
int Error code. iBuffLength int The maximum available length of the string buffer
Return Value lpszError LPSTR Points to a buffer (at least 64 characters long) to hold the error/warning string.
The return value is the length of the error string or one of the following constants.
Value Meaning
27 Signametrics
Negative Value Error code int length = DMMErrString( -3, cBuf, 48);
DMMGetBusInfo
Description
Remarks
Returns the PCI Bus and Slot numbers for the selected DMM.
int DMMGetBusInfo(int nDmm, int *bus, int *slot)
nDmm
This function reads the PCI bus and slot numbers for the selected DMM. . It provides means to relate the physical card location 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.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero. bus int * a pointer to integer at which the bus number is stored (0 to 255)
int * A pointer to an integer where the slot number is stored slot
Return Value
Value
The return value is one of the following constants.
Meaning
DMM_OKAY
Negative number
Operation was successful.
Error code
Example int bus, slot; // Find on which bus, and slot the DMM is at
DMMGetBusInfo(3, &bus, &slot); // DMM#3
Signametrics 28
DMMGetCalDate
Description
Remarks
Return the calibration date string from the DMM.
int DMMGetCalDate(int nDmm, LPSTR lpszCalDate)
nDmm
This function reads the calibration date string from the structure. This is the date the
DMM was calibrated last.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpszCalDate LPSTR Points to a buffer (at least 64 characters long) to hold the cal date string.
The return value is one of the following constants.
Value any positive number
Negative number
Meaning
Length of the date string
Error code int status; status = DMMGetCalDate(0, cBuf);
DMMGetdB
Description Get dB deviation from the reading at the time relative was activated.
#include "SMU2060.H"
Remarks
nDmm
This function returns a double floating value that is the dB deviation relative to the reading made just before the relative function was activated. This function is useful in determining measurement errors in dB. It can be used for bandwidth measurements or
DC evaluation.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpdDev double * 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 dB; int status = DMMGetdB(0, &dB);
29 Signametrics
DMMGetdBStr
Description Get dB deviation from the reading at the time relative was activated.
#include "SMU2060.H"
Remarks
nDmm
This function is the same as the DMMGetdB(), with the exception that it returns a string.
See DMMGetdB() for more details.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero. lpszDB LPCSTR Points to a buffer (at least 64 characters long) to hold the result. The return value will consist of a leading sign a floating-point, and a ‘dB’ units specifier
Return Value
Value
Integer string length if successful, or an error code..
Meaning
Negative Value Error code
Example char cBuf[64]; int strLength = DMMGetdBStr(0, cBuf);
DMMGetDevLocation
Description Get a string containing the location of the DMM in the USB structure.
#include "SMU2060.h"
Remarks This service function retrieves the location of the USB DMM specified by nDmm in the
USB bus. A zero terminated string of length 8 is returned in lpszLoc. This function must be used prior to opening the DMM. That is, prior to initializing or opening it by
DMMInit() or DMMOpenUSB().
Parameter Type/Description
nDmm int Identifies the DMM. DMMs are numbered starting with zero. lpszLoc LPCSTR Points to a buffer (at least 8 characters long) to hold the result.
Return Value Integer string length if successful, or an error code.
Value
Negative Value
Meaning
Error code
Positive Value < 100 The length of the returned string
Postive Value ≥ 100 Warning code int i = DMMGetDevLocation(0, cBuf);
DMMGetDeviation
Description Get percent deviation from the reading at the time relative was activated.
#include "SMU2060.H"
Signametrics 30
Remarks
nDmm
This function returns a double floating value that is the percent deviation relative to the reading made just before the relative function was activated (DMMSetRelative). This function is useful in quantifying measurement errors. It can be used for bandwidth measurements or DC evaluation, or percent variation of a device under test over temperature. The absolute value of lpdDev can be used as a pass/fail window for production.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpdDev double * Pointer where the deviation value is to be saved.
Integer error code..
Value Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
Example double error; int status = DMMGetDeviation(0, &error);
DMMGetDeviatStr
Description Get percent deviation from the reading at the time relative was activated.
#include "SMU2060.H"
Remarks
nDmm
This function is the same as the DMMGetDeviation(), with the exception that it returns a string. See DMMGetDeviation() for more details.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpszDev LPCSTR Points to a buffer (at least 64 characters long) to hold the result. The return value will consist of a leading sign a floating-point, and a % units specifier
Integer string length if successful, or an error code.
Value Meaning
Negative Value Error code int strLength = DMMGetDeviatStr(0, cBuf);
DMMGetDiffMnMxStr
Description Returns the difference between the max and min values as string.
#include "SMU2060.H"
31 Signametrics
int (int nDmm, LPSTR lpszReading)
Remarks This function return the difference between the current Max. and Min values, which is the peak-to-peak range of recent readings. It returns the result as a string formatted for printing. The print format is determined by the range and function.
Parameter
nDmm
Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpszReading LPSTR Points to a buffer (at least 64 characters long) to hold the result.
The return value is one of the following constants, or the string length is OK.
Value
DMM_OKAY
Negative Value
Meaning
Valid return.
Error code int status = DMMGetDiffMnMxStr(0, cBuf);
DMMGetFunction
Description Get DMM function code.
#include "SMU2060.H"
DMMGetFunction(int nDmm)
Remarks This function returns the DMM function code. The codes are defined in the DMMUser.h file.
Parameter Type/Description
Return Value
nDmm int Identifies the DMM. DMMs are numbered starting with zero.
Integer value corresponding to the current function, or an error code.
Value
Positive value
Negative Value
Meaning
See DMMUser.h for function/range codes.
Error code
Example if(DMMGetFunction == VDC) printf("VDC Function selected");
DMMGetGrdVer
Description Get DMM firmware version.
#include "SMU2060.H"
Signametrics 32
Remarks
int DMMGetGrdVer(int nDmm)
This function returns the DMM firmware version of the on-board controller.
Return Value
Parameter
nDmm
Type/Description
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
Positive Value Version
Negative Value Error code
Example firmwarever = DMMGetGrdVer(0);
DMMGetHwVer
Description Get the hardware version of the DMM.
#include "SMU2060.H"
Remarks
Return Value
nDmm
This function returns the hardware version. A returned value of 0 corresponds to Rev_, 1 corresponds to Rev_A, 2 to Rev_B etc.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
DMM hardware code or an error code.
Value
Positive value
Meaning
Hardware version code
Negative Value Error code
Example int HWVer = DMMGetHwVer(0);
DMMGetHwOption
Description Get the hardware option installed in the DMM.
#include "SMU2060.h"
Remarks This function returns the hardware options installed. It returns a single character value corresponding to the option. For instance, if option ‘R’ in installed, 0X12, the ASCII equivalent or the letter ‘R’ is returned.
33 Signametrics
Parameter
nDmm
Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value DMM hardware code or an error code.
Value
Positive value
Meaning
Hardware version code
Negative Value
Example
DMMGetID
Error code int HWOption = DMMGetHwOption(0);
Description
Remarks
Get DMM ID code.
#include "SMU2060.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 SM60CAL.DAT. This code must reflect the last digits of the DMM serial number.
Parameter
nDmm
Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value Integer value card ID code (serial number) or an error code.
Value
DMM_E_DMM
Meaning
Invalid DMM number.
Example int id = DMMGetID(0);
Signametrics 34
DMMGetManDate
Description
Remarks
Get Manufacturing date stamp from the DMM hardware
#include "SMU2060.H"
int DMMGetManDate(int nDmm, int *month, int *day, int *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 manufacturing date.
Parameter
nDmm month
Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
int * A pointer to an integer where the month is stored
int * A pointer to an integer where the day is stored day
Return Value
year
Value
int * A pointer to an integer where the year is stored
Integer error code or.
DMM_OKAY
DMM_E_DMM
Meaning
Operation was successful.
Invalid DMM number.
Example int month, day, year, status status = DMMGetManDate(0, &month, &day, &year);
DMMGetMax
Description Get Maximum reading history.
#include "SMU2060.H"
Remarks
nDmm
This function returns a double floating value that is the maximum (of the Min/Max function) value since either a function change, range change or call to the
DMMClearMinMax function was made. This value is updated every time a measurement is performed using DMMRead, DMMReadStr or DMMReadNorm.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpdMax double * Pointer where the Max value is to be saved.
Integer error code..
35 Signametrics
Value Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
Example double Mx; int status = DMMGetMax(0, &Mx);
DMMGetMaxStr
Description Returns the maximum as a formatted string.
#include "SMU2060.H"
Remarks This function is the string version of DMMGetMax. It returns the result as a string formatted for printing. The print format is determined by the range and function. See
DMMGetMax for more details.
Parameter
nDmm
Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpszReading LPSTR Points to a buffer (at least 64 characters long) to hold the result.
The return value is one of the following constants, or the string length is OK.
Value
DMM_OKAY
Negative Value
Meaning
Valid return.
Error code int status = DMMGetMaxStr(0, cBuf);
DMMGetMin
Description Get Minimum reading history.
#include "SMU2060.H"
Remarks This function returns a double floating value that is the minimum (of the Min/Max function) value since either a function change, range change or a call to the
DMMClearMinMax() function was made. This value is updated every time a measurement is performed using DMMRead, DMMReadStr or DMMReadNorm.
Signametrics 36
Parameter
nDmm
Type/Description
int Identifies the DMM. DMMs are numbered starting with zero. lpdMax double * Pointer where the Min value is to be saved.
Return Value
Value
Integer error code..
Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
Example double Min; int status = DMMGetMin(0, &Min);
DMMGetMinStr
Description Returns the minimum as a formatted string.
#include "SMU2060.H"
Remarks
nDmm
This function is the string version of DMMGetMin. It returns the result as a string formatted for printing. The print format is determined by the range and function. See
DMMGetMin for more details.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpszReading LPSTR Points to a buffer (at least 64 characters long) to hold the result.
The return value is one of the following constants, or the string length is OK.
Value
DMM_OKAY
Negative Value
Meaning
Valid return.
Error code int status = DMMGetMinStr(0, cBuf);
DMMGetNumDevices
Description Get the number of USB DMM devices connected to the USB structure.
#include "SMU2060.h"
int DMMGetNumDevices(int * nDevices)
Remarks This function retrieves the number of USB DMM devices connected to the USB bus. The number of devices is saved at a location pointed to by nDevices. This function must be used prior to opening the DMM. That is, prior to initialized or opening it by DMMInit() or DMMOpenUSB(). See also DMMGetDevLocation().
37 Signametrics
Parameter
nDevices
Type/Description
* int Points to a location at which the number of devices is saved.
Return Value Integer string length if successful, or an error code.
Value
Negative Value
Meaning
Error code
Positive Value < 100 The length of the returned string
Postive Value ≥ 100 Warning code
Example int I; int number;
I = DMMGetNumDevices(& number);
DMMGetRange
Description
Remarks
Get DMM range code.
#include "SMU2060.H"
#include "DMMUser.h"
int DMMGetRange(int nDmm)
This function returns the DMM range code. The range codes are in the sequence of 0, 1,
2, 3, … where 0 is the lowest range.
Parameter
nDmm
Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value
Value
Integer value corresponding to the currently set DMM range, or an error code.
Meaning
Zero or positive value Range; zero being the lowest
Negative Value Error code if(DMMGetRange == 0) printf("Lowest range selected");
DMMGetRate
Description Get the currently set reading rate
#include "SMU2060.H"
DMMGetRate(int
Remarks This function returns a double floating rate in readings per second. See DMMSetRate for details
Parameter Type/Description
nDmm lpdRate
int Identifies the DMM. DMMs are numbered starting with zero.
double * Pointer where the rate is saved to.
Return Value Integer value version code or an error code.
Value Meaning
Signametrics 38
Example
Negative Value Error code int status; double rate; status = DMMGetRate(0, & rate);
DMMGetSupplyV
Description Returns the one of the DMM supplies voltages.
#include "SMU2060.H"
Remarks
nDmm
This function makes a measurement of one of the DMM power supplies voltages as an indication of the USB supply voltage level. The nominal value is -12V. The USB interconnect and some off the shelve hubs can make this voltage higher or lower than is required. The acceptable value should be -10.5 to -13.5V. Voltages higher than -13.5V may damage the SMU2055 and voltages below -9.0 are inadequate for proper operation, and is usually indicative of poor USB cable. The value of this voltage is stored at a double precision location pointed to by lpdVoltage.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpdVp;tage LPSTD Points to a double to hold the result.
The return value is one of the following constants, or the string length is OK.
Value
DMM_OKAY
Negative Value
Positive Value
Meaning
Valid return.
Error code
Warning code int status = DMMGetSupplyV(0, @v);
DMMGetStoredReading
Description Get a single stored reding.
#include "SMU2060.h"
Remarks User this function to retrieve readings previously captured by DMMReadNsamples.
Return a double precision reading number iIndex by placing it at a location pointed to by lpdRdng. iIndex can have a value between 0 and the total number of measuremens taken by DMMReadNsamples minus 1 (iN – 1).
Parameter Type/Description
39 Signametrics
nDmm iIndex
int Identifies the DMM. DMMs are numbered starting with zero.
int Index to the stored reading, can be 0 to the total of number of readings taken mins 1.
Return Value lpdRdmg double * Pointer where the reading value is to be saved.
Integer error code..
Value Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
Example double v; int status = DMMGetStoredReading(0, 0, &v); // get the 1 st reading
DMMGetType
Description Get the type of the DMM.
#include "SMU2060.H"
Remarks This function returns a value identifying the DMM model.
Parameter Type/Description
Return Value
nDmm int Identifies the DMM. DMMs are numbered starting with zero.
DMM type Integer or an error code.
Value
2055
Meaning
SM2055 is at nDmm slot
Other positive value Warning code
Negative Value
Example
DMMGetVer
Error code int DMMtype = DMMGetType(0);
Description Get DMM software driver version.
#include "SMU2060.H"
Remarks This function returns the DMM software driver version, which is a double floating value.
Parameter Type/Description
Signametrics 40
Return Value
nDmm
lpfResult
Integer error code.
int Identifies the DMM. DMMs are numbered starting with zero.
double * Pointer to the location which holds the version.
Value
Negative Value
Meaning
Error code
Example int status; double ver; status = DMMGetVer(0, &ver);
DMMInit
Description
Remarks
Initialize a DMM.
#include "SMU2060.H"
int DMMInit(int nDmm, LPCSTR lpszCal)
nDmm
This function must be the first function to be executed. It opens the driver for the specified DMM. The first DMM being 0, the second 1, etc.. It also initializes the DMM hardware and does extensive self test to the DMM hardware. It then initializes the software and reads the appropriate calibration record for the respective DMM from the file specified by lpszCa, followed by self calibration. If the calibration record is outdated, it opens a warning window. If an error is detected, an error code is returned.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
lpszCal LPCSTR Points to the name of the file containing the calibration constants for the DMM. Calibration information is normally read from the file named SM60CAL.DAT located in the current directory.
Return Value
Value
The return value is one of the following constants.
Meaning
DMM_OKAY
Negative Value
DMM initialized successfully.
Error code
Example /* initialize DMM */ int i = DMMInit(0,"C:\SM60CAL.dat");// Initialize the first DMM
DMMIsAutoRange
Description Get the status of the autorange flag.
#include "SMU2060.H"
41 Signametrics
Remarks This function returns the DMM autorange flag state.
Parameter Type/Description
Return Value
nDmm int Identifies the DMM. DMMs are numbered starting with zero.
TRUE, FALSE or an error code.
Value
TRUE
FALSE
DMM_E_DMM
Meaning
Autoranging mode is selected.
Autoranging mode is not selected.
Invalid DMM number.
Example int autorange = DMMIsAutoRange(0);
DMMIsInitialized
Description Get the status of the DMM.
#include "SMU2060.H"
Remarks
nDmm
This function returns the status of the DMM. If TRUE, the DMM has been initialized and is active. If FALSE the DMM is not initialized. To use the DMM, it must be initialized using DMMInit function. This function is used for maintenance and is not needed under normal operation.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value
Value
TRUE
FALSE
TRUE, FALSE or an error code.
Meaning
DMM is initialized and active.
DMM is not initialized.
DMM_E_DMM Invalid DMM number.
Example int active = DMMIsInitialzied(0);
DMMIsRelative
Description Get the status of the Relative flag.
#include "SMU2060.H"
Signametrics 42
Remarks This function returns the DMM Relative flag state.
Parameter Type/Description
nDmm int Identifies the DMM. DMMs are numbered starting with zero.
Return Value
Value
Integer TRUE, FALSE or an error code.
Meaning
TRUE
FALSE
Relative mode is selected.
Relative mode is not selected.
Negative Value Error code
Example int rel = DMMIsRelative(0);
DMMOpenUSB
Description A service function which open the USB bus for the SMU2055. Not for user application.
#include "SMU2060.H"
Remarks
nDmm
This function is limited for servicing the DMM. It has no use in normal DMM operation..
See also DMMCloseUSB() function.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value Integer error code.
Value Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
Example int status = DMMOpenUSB(0);
DMMRead
Description
Return the next floating-point reading from the DMM.
#include "SMU2060.H"
43 Signametrics
Remarks DMMRead function causes the DMM to perform a single conversion and retrieve the result. The DMM, performs all scaling and conversion required, and 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 DMMSetRange() ). Returned result is a scaled value which is normilized to the selected range. That is . That is, it returns 200 for 200mV input in the
240 mV range, and 100 for 100 k input in the 330k range. Alternatively use the
DMMReadNorm() function for base units read function, or DMMReadStr() to return the results as formated string of the DMMRead().Very large values are indication of over range condition.
Parameter Type/Description
nDmm int Identifies the DMM. DMMs are numbered starting with zero.
double * Points to the location to hold the next reading. lpdResult
Return Value
Value
The return value is one of the following constants.
Meaning
DMM_OKAY
Negative Value
Positive Value
DMM initialized successfully.
Error code
Warning code, including over range.
Example double dResults[100]; int status;
For(i=0; I < 100; i++) DMMRead(0, &dResults[i]);// Read to a buffer
DMMReadNorm
Description
nDmm
Take a reading that is in base value.
#include "SMU2060.H"
int DMMReadNorm(int nDmm, double *lpdRead)
Remarks This function returns a double floating-point reading. Unlike DMMRead() the returned value is in base units. That is, it returns 0.2 for a 200 mV input and 1e6 for a 1.0 M .
Very large values are indication of over range condition.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value lpdRead double * Pointer to a location where the reading is saved.
Integer value version code or an error code.
Value
DMM_E_RANGE
Negative Value
DMM_OKAY
Meaning
Over/Under range error.
Error code
Valid return.
Signametrics 44
Example double reading; int status = DMMReadNorm(0, &reading);
DMMReadNsamples
Description
nDmm
Take a reading that is in base value.
#include "SMU2060.h"
int DMMReadNsamples(int nDmm, int iN)
Remarks In response to this command the DMM take iN measurements, and sends them back to the USB bus. In order not to loose any, and cause overrun, use
DMMGetStoredReading() in a tight loop. Measurements are made using the currently selected function, range and aperture.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value iN Int The number of measurements to be taken. This value must be between 2 and 10,000.
Integer value version code or an error code.
Value
POS_FS or NEG_FS
Negative Value
DMM_OKAY
Meaning
Positive or Negative Full Scale, or overrange
Error code
No error
Example int status = DMMReadNsamples(0, 100);
DMMReadStr
Description Return the next reading from the DMM formatted for printing.
#include "SMU2060.H"
Remarks
Return Value
nDmm
This function is the string version of DMMRead(). It reads the next 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
int Identifies the DMM. DMMs are numbered starting with zero. lpszReading LPSTR Points to a buffer (at least 64 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.
The return value is one of the following constants, or the string length is OK.
45 Signametrics
Value Meaning
DMM_OKAY
Negative Value
Valid return.
Error code
DMM_E_RANGE DMM over range error occurred.
Example char cBuf[64]; int status = DMMReadingStr(0, cBuf);
DMMSetAutoRange
Description Enable/Disable autorange operation of DMM
#include "SMU2060.H"
Remarks This function enables or disables autorange operation of the DMM.
Parameter Type/Description
Return Value
nDmm bAuto
int Identifies the DMM. DMMs are numbered starting with zero.
int Determines whether or not autoranging is done. The value TRUE
(1) enables autoranging, FALSE (0) disables it.
The return value is one of the following constants.
Value
DMM_OKAY
Negative Value
Meaning
Function succeeded.
Error code
Example status = DMMSetAutoRange(0, TRUE); /* enable autoranging */
DMMSetFunction
Description Set the DMM function.
#include "SMU2060.H"
#include "DMMUser.h"
Remarks This function selects the DMM’s measurement function. The DMMUser.h file contains a table of values defined as VDC, VAC, IAC, IDC, OHMS4W, OHMS2W etc... Not all functions are available for all DMM types.
Signametrics 46
Parameter
nDmm
Type/Description
int Identifies the DMM. DMMs are numbered starting with zero. nFunc int A pre-defined constant corresponding to the desired function.
Return Value
Value
The return value is one of the following constants.
Meaning
DMM_OKAY
Negative Value
DMM initialized successfully.
Error code
DMM_E_FUNC Invalid DMM function.
Example status = DMMSetFunction(0, IDC); // Set for DC current
DMMSetRange
Description
Remarks
Set the DMM range for the present function.
#include "SMU2060.H"
int DMMSetRange(int nDmm, int nRange)
This function sets the range used by the DMM for the present function. The table of values is defined by the _240mV, _2400uA, etc. In general, the lowest range is 0, next is
1 etc. Each function has a pre defined number of ranges as specified in the specification section of this manual. Not all ranges are available for all DMM types. For instance the
SM2064 has a 24 Ohms and 240Meg range, while the SM2060 and SMU2055 do not.
Parameter Type/Description
nDmm int Identifies the DMM. DMMs are numbered starting with zero.
int A pre-defined constant corresponding to the desired range. nRange
Return Value
Value
The return value is one of the following constants.
Meaning
DMM_OKAY
Negative Value
DMM initialized successfully.
Error code
DMM_E_RANGE Invalid DMM range value.
Example status = DMMSetRange(0, _24mA);
47 Signametrics
DMMSetRate
Description Set the measurement rate.
#include "SMU2060.h"
#include "USBDMMUser.h"
Remarks
nDmm
int DMMSetRate(int nDmm, int iRate)
This function sets the rate at which the DMM makes measurements. The allowed values are defined in the DMMUser.h file. The rate (iRate) can be set from 0.5rps (RATE_p5) to 250rps (RATE_250). Some of the rates have specific power line rejection as indicated in the specification part of this manual. See DMM
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value iRate int A pre-defined constant corresponding to the desired rate.
The return value is one of the following constants.
Value
DMM_OKAY
Meaning
DMM initialized successfully.
Negative Value Error code
ERR_PARAMETER Invalid measurement rate value entered.
Example status = DMMSetRate(0, RATE_2); // Set to 2rps
Signametrics 48
DMMSetRelative
Description Set the DMM relative reading mode for the present function.
#include "SMU2060.H"
Remarks This function selects relative or absolute reading mode for the DMM. If the bRelative parameter value is TRUE (1), the DMM will change to relative reading mode. If
FALSE, the DMM will change to absolute reading mode.
Parameter Type/Description
nDmm int Identifies the DMM. DMMs are numbered starting with zero.
int TRUE (1) to enter relative mode, FALSE (0) to clear mode. bRelative
Return Value
Value
The return value is one of the following constants.
Meaning
DMM_OKAY
Negative Value
DMM mode changed successfully.
Error code
Example status = DMMSetRelative(0, TRUE);
DMMTerminate
Description
Remarks
TRUE
FALSE
Terminate DMM operation (DLL)
#include "SMU2060.H"
int DMMTerminate(int nDmm)
Removes DMM number nDmm. This routine is used only where it is needed to terminate one DMM and start a new one at the same nDmm location. Otherwise, it is not recommended to use this function.
Parameter Type/Description
int Identifies the DMM to be suspended. nDmm
Return Value
Value
The return value is one of the following constants.
Meaning
DMM Terminated
DMM was not initialized, termination is redundant.
Example DMMTerminate(0); /* Terminate DMM # 0 */
5.7 Calibration Service Commands
49 Signametrics
AC_zero
Description Disable AC measurement zero funciton.
#include "SMU2060.H"
#include "UseroDMM.h"
int
Remarks ith bACZero FALSE, the AC zero function is disabled. If TRUE it is enabled. The default value is TRUE. Diabeling the AC Zero funciton allows the derivation of the value to be set as offset parameter for the selected ACV range. This function is used during calibration.
Parameter Type/Description
Return Value iDmm bACZero
Identifies the DMM. DMMs are numbered starting with zero.
Forces the AC zero to be active or inactive. Allowed values are TRUE of FALSE.
The return value is one of the following constants.
Value
DMM_OKAY
Negative Value
Meaning
Valid return.
Error code
Err = AC_zero(0, FALSE); // disable AC Zero.
DMMLoadCalFile
Description
Remarks
Reload calibration record from file.
#include "SMU2060.H"
int DMMLoadCalFile(int nDmm, LPCSTR lpszCal)
This function provides the capability to reload the calibration record. This is useful in making limited calibration adjustments, and verifying them. By having a copy of the original calibration file ‘SM60CAL.DAT’ open with an editor, modifying calibration parameters and then reloading using DMMLoadCalFile, one can instantly verify the corrections made. Make sure the ‘SM60CAL.DAT’ file itself is not altered since that will void the calibration.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero. nDmm
lpszCal LPCSTR Points to the name of the file containing the calibration constants for the DMM.
Signametrics 50
Return Value The return value is one of the following constants.
Value
DMM_OKAY
Negative Value
Meaning
Cal record loaded successfully.
Error code
Example /* Load a modified copy of the original calibration file to verify correction made to a specific entry */ int i = DMMLoadCalFile(0, "C:\CAL_A.dat");
SetGain
Description Set currently set gain during service.
#include "SMU2060.H"
#include "UseroDMM.h"
int
Remarks This function sets the currently set gain,. Sets the gain of the the currently selected function and range. The gain is returned as double-precision floating-point number
Gaint. This function is useful while performaing calibration. Set GetGain() function for additional details.
Parameter Type/Description
Return Value iDmm Identifies the DMM. DMMs are numbered starting with zero.
The return value is one of the following constants.
Value Meaning lpdGain
DMM_OKAY
Negative Value
double the gain.
Valid return.
Error code
Example
GetGain
SetGain(0, 1.00023); // set gain
Description Retrieve currently set gain.
#include "SMU2060.H"
#include "UseroDMM.h"
GetGain(int
51 Signametrics
Remarks This function returns the currently set gain,. This is the gain associated with the currently selected function and range. The value should be the same as that set in the calibration record for this function and range. The gain is returned as a 64-bit double-precision floating-point number in the location pointed to by lpdGaint. This function is useful while performaing calibration. Set SetGain() function for additional details.
Parameter Type/Description
Return Value iDmm Identifies the DMM. DMMs are numbered starting with zero.
The return value is one of the following constants.
Value Meaning lpdGain
DMM_OKAY
Negative Value
double * Points to the location to hold the gain.
Valid return.
Error code
GetOffset
Description
GetGain(0, &gain); // read gain
Retrieve currently set gain.
#include "SMU2060.H"
#include "UseroDMM.h"
Remarks This function returns the currently set offset,. This is the offset associated with the currently selected function and range. The value should be the same as that set in the calibration record for this function and range. The offset is returned as a 64-bit doubleprecision floating-point number in the location pointed to by lpdOffsett. This function is useful while performaing calibration. Set SetOffset() function for additional details.
Parameter Type/Description
Return Value iDmm Identifies the DMM. DMMs are numbered starting with zero.
The return value is one of the following constants.
Value Meaning lpdOffset
DMM_OKAY
Negative Value
double * Points to the location to hold the offset.
Valid return.
Error code
GetOffset(0, &offst); // read gain
Signametrics 52
SetFcomp
Description Set the ACV Frequency compensation factor during service.
#include "SMU2060.H"
Remarks
nDmm
This function sets the value of the ACV frequency compensation DAC. It is used for calibration the ACV bandwidth..
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value iFcomp int Freqeuncy Compnensation DAC value to be set. Allowed value is between 0 and 31.
Integer error code.
Value Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
Example
SetOffset
SetFcomp(0, 12); // set the frequency compensation
Description Set the the offset correction factor
#include "SMU2060.H"
Remarks
nDmm
This function sets the value of the offset correction factor for the currently set function and range..
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value dOffset double Offset value to be set.
Integer error code.
Value Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
53 Signametrics
Example
Linearize_AD
SetOffset(0, 11212.0); // Assert the offset factor
Description Activate/Deactivate A/D linearization correction during service.
#include "SMU2060.H"
#include "UseroDMM.h"
Remarks If is TRUE. Diabeling allows for the derivation of the parameters for calibration purposes.
This function is used during calibration only.
Parameter Type/Description iDmm
Identifies the DMM. DMMs are numbered starting with zero.
Return Value bACZero Forces the AC zero to be active or inactive. Allowed values are TRUE of FALSE.
The return value is one of the following constants.
Value
DMM_OKAY
Negative Value
Meaning
Valid return.
Error code
Err = Linearize_AD(0, FALSE); // disable AC Zero.
Read_ADcounts
Description Read A/D offset counts during calibration.
#include "SMU2060.H"
int
Remarks This function returnes the A/D raw counts. It is useful for retrieving the offset parameter for various functions, including VDC, 2-W and 4-W ohms and DC current. It is limited for service and calibration use.
Parameter Type/Description
Return Value
nDmm int Identifies the DMM. DMMs are numbered starting with zero.
Integer error code.
Value Meaning
Example
Any value int Offset reading. int i = Read_ADcounts(0)
; // read offset parameter
Signametrics 54
5.8 Maintanance Commands
GrdXingTest
Description Perform the specified test
#include "SMU2060.H"
Remarks Perform the specified test as indicated by iTest. Repeat it for iNumber times. This function is used to perform basic H/W tests.
Parameter Type/Description
nDmm iTest
int Identifies the DMM. DMMs are numbered starting with zero.
int Test type. 0: Basic Read/Write. 1: Toggle Reset line iNumber times. 2: High Speed Guard Crossing stimulation. 3: Guarded controller communication test. 4: Guard Crossing loopback test. 5:
High Speed Guard Crossing test (SM2064). iNumber int Number of tests to be repeated.
Return Value
Value
Integer error code.
Meaning
DMM_OKAY Operation successfully completed.
Negative Value Error code
Example int i =
GrdXingTest(0, 1, 3); // Test Guarded controller
WrCalFileToStore
Description
Remarks
nDmm
Transfer the contents of a cal file to the on-board cal store.
#include "SMU2060.h"
int WrCalFileToStore (int nDmm,LPCSTR lpszCal)
This function copies the specified calibration file, pointed to by lpszCal, to the on-board none volatile store of the DMM. This is appropriate following calibration operation. The currently stored on-board record is replaced with the contents of the speified file. Make sure that the calibration file only contains only one record, for the specified DMM.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero. lpszCal LPCSTR Points to the name of the file containing the calibration constants for the DMM. Calibration information is normally read from the file named SM60CAL.DAT located in the C:\ root directory.
Return Value Integer error code.
55 Signametrics
Value Meaning
Any value not 0 int Eror or warning code
Example int i = WrCalFileToStore (0,
"C:\\SM60CAL.dat"
)
;
WrCalStoreToFile
Description
Remarks
Transfer the contents of the on-board cal store to a file.
#include "SMU2060.h"
int WrCalStoreToFile (int nDmm,LPCSTR lpszCal, int mode)
nDmm
This function copies the calibration record stored in the on-board none volatile memory of the DMM to the specified calibration file, pointed to by lpszCal. If mode is ‘a’ and a file exists, the record is appended to the end of this file. If mode is ‘w’, a new file is created, wiping out the old if it exists.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value mode lpszCal
int Sets the file creation mode.
LPCSTR Points to the name of the file containing the calibration constants for the DMM. Calibration information is normally read from the file named SM60CAL.DAT located in the C:\ root directory.
Integer error code.
Value Meaning
Any value not 0 int Eror or warning code
Example
EraseCalStore
int i = WrCalStoreToFile (0,
"C:\\SM60CAL.dat", ‘a‘
)
;
Description Service function that wipes the Calibration record off the internal memory.
#include "SMU2060.h"
Remarks
nDmm
This function reformats the none volatile calibration store on-board the DMM, preparing it for storing a calibration record. This function will remove the currently stored calibration record and is not necessary during calibration.
Parameter Type/Description
int Identifies the DMM. DMMs are numbered starting with zero.
Return Value Integer error code.
Signametrics 56
Value Meaning
Any value int Eror or warning code.
Example int i = EraseCalStore(0)
; // Erase/Format cal store EEProm
5.9 Error Codes
Operation of the DMM may be impaired, should be aborted or is not possible following an Error. Use the
DMMErrString() function, to retrieve the string describing the error.
DMM_E_INIT
DMM_E_CAL_R
ERR_AD_HW
NO_CAL_RECORD
TRIG_ERR
GUARD_COM
TIMEOUT
GUARD_XING
WRONG_TYPE
UNKNOWN_ERROR
CANT_OPEN_USB
GENERAL_ERR
CAL_STORE
CREAT_CAL_FILE
OPEN_CAL_FILE
-1
-2
-3
-4
-5
-6
-7
-9
-10
-11
-12
-13
-14
-15
// DMM is not initialized. Use DMMInit() prior to using
// cannot find valid calibration record
// A/D does not respond. H/W error
// can't find cal record for DMM
// Trigger circuit error
// Microcontroller communication error
// process timed out Error
-8 // Guard crossing is broken
// Wrong Cal record for DMM type
// Undefined Error
// can’t open USB device. Already open or an SMU403X
// General Error
// Error reading Cal record from local storage
// can’t create named cal file to write to
// can’t open cal file for reading cal record
CREAT_CAL_RCRD -16 // can’t create on-board Cal Record
ERROR_EEPROM_DTYPE -17 // Invalid dmm type in EEProm
ERROR_READBYTES
ERROR_WRITEBYTES
-18
-19
// unexpected number of bytes read
// unexpected number of bytes written
ERROR_DTYPE -20 // invalid input, bad DMM Type parameter
ERROR_READ_EEPROM -21 // invalid data on the EEPROM
ERROR_USB_IO
ERROR_USB_PWR
-22
-23
// I/O error from USB bus
// USB 5V supply is too low
MCU_COM_ERROR -24 // Microcontroller communication error
5.10 Warning Codes
Following a warning, the DMM will continue to run normally with the exception of the fault indicated by warning code. Use the DMMErrString() function, to retrieve the string describing the warning. This string may be used to notify the user. Based on it, an action may be taken to correct the source of the warning. Several of the warning codes are part of a normal operation. Such are DMM_CNT_RNG, which indicates that the counter requires additional iterations, or the POS_FS and NEG_FS are indication that the signal level is too high for the selected range, which is normal.
APERTR_TOO_HIGH 101 // Aperture value is too high for operation
DMM_E_FUNC 102 // Invalid function value used
DMM_E_RNG
DMM_CNT_RNG
103
104
// Invalid range value used
// DMM counter out of range
DMM_E_IS_INIT
CAP_RATE_ERR
ERR_FUNC
ERR_APERTURE
105 // Dmm already initialized: in use
106 // Can't change rate in Cap mode.
107 // Illegal function selection
108 // Wrong Aperture selected, see rate definition
57 Signametrics
TRIG_SAMPL_ERR 109 // Wrong number of Trigger samples
ERR_PARAMETER 110 // wrong parameter value
UN_CALIBRATED 111 // Expired Calibration. Needs service
TOO_COLD 112 // Temperature too low
TOO_HOT
BAD_TC_TYPE
MC_STOP
POS_FS
113 // Temperature too high
114 // Wrong TC type
115 // Microcontroller was stopped/interruped during an operation
116 // Positive Over Range
NEG_FS
BUSY
117 // Negative Over Range
118 // DMM is busy, wait for ready
FUNC_INACTIVE 119 // Function can not be selected, or not available for this type DMM.
READ_INTERVL 120 // Read Interval value incompatible with Aperture,
FAIL_OPEN_CAL 121 // Failed to perform Open-Cal operation
CAL_2usOffset 122 // Failed to Cal offset in 2.5uS Aperture
CAL_2usGain 123 // Failed to Cal gain in 2.5uS Aperture
USB_LOW_POWER 124 // USB supply is too low for this opereation
USB_HIGH_POWER 125 // USB supply is too high
WRONG_GRD_VER 126 // MCU Firmwhare does not support operation
5.11 Parameter List
The following definitions are from the DMMUser.H file.
5.11.1 Measurement and Source Functions
The following list contains values that set the DMM functions. Use the DMMSetFuncction() function to set these values. Use DMMGetFunction() to retrieve the value of the currently set function
#define VDC
#define VAC
0
5
DC Volts
AC Volts
#define IAC
#define IDC
#define OHMS4W
#define OHMS2W
10
14
22
29
AC Current
DC Current
2-Wire resistance
4-Wire resistance
#define DIODE 37 Diode test
5.11.2 Range Values
The following list contains the allowed values for range setting with DMMSetRange() function. Use the
DMMGetRange() function to retrieve the currently set range
// AC and DC Volts
#define _240mV
#define _2400mV
#define _24V
0
1
2
// four AC and DC voltage ranges
#define _240V
// AC Current
#define _2400uAAC
#define _24mAAC
#define _240mA
#define _2400mA
// 2 Wire and 4 Wire Ohms
3
#define _240mAAC
#define _2400mAAC
0
1
2
3
// 2.4mA
// 24mA
// 2.4A
// DC Current
#define _2400uA 4 // 2.4mA
24mA
6
7
// 240mA
// 2.4A
Signametrics 58
#define _240
#define _2400
#define _24k
#define _240k
1
2
3
4
#define _2400k
#define _24MEG
5
6
// Two Meg range
// 2-Wire
// Diode test
#define _D100n 0 //Test current = 100nA
1uA
10uA
1mA
5.11.3 Measurement Rate parameters
The following list contains the definitions for the available Rates. Use DMMSetRate() and
DMMGetRate() to set and retrieve the currently set measurement rate..
#define RATE_1
#define RATE_2
#define RATE_3
#define RATE_7
#define RATE_14
#define RATE_27
#define RATE_50
#define RATE_90
14
27
50
90
1
2
3
7
// 1rps with 60Hz line rejection
// 2rps with 50Hz line rejection
// 3rps with 60Hz line rejection
// 7rps with 50Hz line rejection
// 14rps with 60Hz line rejection
// 27rps with 50Hz rejection
// 50rps with 60Hz rejection
// 90rps with 50Hz rejection
59 Signametrics
6 Calibration
Each SMU2055 DMM uses its own SM60CAL.DAT calibration record to ensure the accuracy of its functions and ranges. The SM60CAL.DAT file is a text file that contains the DMM identification number, calibration date, and calibration constants for all DMM ranges. When the DMM is installed this file is generated from an internally stored record. Once extracted, the DMM reads it from a file rather than from its on-board record, since it is faster to read from a file. For most functions, the calibration constants are scale factor and offset terms that solve an "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 SM2060 family. The following calibration record is for the SMU2055 and it contains some placeholders for ranges that are not available with the product. An example SM60CAL.DAT follows: card_id 8123 type 2055 calibration_date 06/15/2008
2.0 10 0.99995 vdc #VDC 240mV, 2.4V,24V, 240V, 330V ranges, offset and gain parameters
-386.0 0.99961
-37.0 0.999991
-83.0 0.999795
-8.8 1.00015 vac #VAC 1st line - DC offset. Than offset, gain and freq each range240mV to 330V
0.84 1.015461 23
0.0043 1.0256 23
0.0 1.02205 0
0.0 1.031386 0 idc # IDC 240nA to 2.5A, 8 ranges, offset and gain
-1450.0 1.00103 ;2.4mA range
-176.0 1.00602
-1450.0 1.00482
-176.0 1.00001 iac
;2.4A range
# IAC 2.4mA 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 24, 240, 2.4k,24k,240k,2.4M,24M,240Meg ranges, offset and gain
1256.0 1.002307
110.0 1.002665
0.0 1.006304
0.0 1.003066
0.0 1.001848
0.0 0.995664 ;24
…
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 24 range, and "
1.002259
" is the scale factor for this range.
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.
Signametrics 60
The SM60CAL.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 SM/SMU2055/60/64 is best performed using calibration software available from Signametrics.
When using multiple DMMs in a single chassis, the SM60CAL.DAT file must have a calibration record for each DMM. You can combine the unique calibration records of each DMM into one
SM60CAL.DAT file using any ASCII text editor such as “notepad.exe”.
61 Signametrics
7.0 Warranty and Service
The SMU2060, SMU2064 and SMU2055 are warranted against defects in manufacturing and materials for a period of one year from date of purchase. Removal of any of the three external shields or any attempt to repair the unit by other than unauthorized Signametrics service personnel will invalidate your warranty. Operating the Signametrics products outside their specified limits will void the warranty. For in-warranty repairs, you must obtain a return materials authorization (RMA) from Signametrics prior to returning your unit. Customer ships products at customer’s expense. Within the USA Signametrics will ship serviced or replaced unit at Signametrics’ expense.
Warranty extensions are available at the time of purchase for terms up to 36 months, in increments of 12 months.
If your unit requires repair or calibration, contact your Signametrics representative. There are no user serviceable parts within these products.
8.0 Accessories
Several accessories are available for the SM2055 DMM, 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
Signametrics 62
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