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Instruments
MANUAL
HM 8112
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CONTENTS
General Description
Specifications
Commencing Operation
Keyboard and Integration Setting
Offset Correction
Error Messages and Self Test
Operating
Operating
Operating
Operating
Operating
Operating
Instructions Vdc
Instructions Vac
Instructions mAdc/mAac
Instructions KOhm
SYSTEM MULTIMETER
HM 8112
Instructions for scanner/multiplexer (Option)
Instructions for External Triggering
IEEE 488-Bus-Interface
Calibration
Accessories
Service Manual
HM 8112 HAMEG GmbH - Subject to
change without notice
Sept.
88
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AUTO
HAMEL |
Instruments |
True RMS Measurement Capability
Automatic or Manual Range Setting
With the HM 8112, HAMEG extends its successful range
of professional oscilloscopes and test equipment with an
exceptionally low priced 6% digit high accuracy system
multimeter. Fully matching the dimensions of HAMEG's
Modular System 8000, very compact, efficient and flexible
test facilities can be assembled requiring only a minimum
of space.
Incorporating high stability amplifiers and a precision A/D
converter, the HM 8112 permits DC-measurements with
100nV resolution at 1sec. integration time. True RMS
measurements with DC-coupling are provided in all AC
ranges, and resistances can be determined with 1m
resolution during two-pole measurements. The digital off-
set correction feature enables easy offset voltage com-
pensation at the touch of a pushbutton. This facility is par-
ticularly useful for counteracting both undesired thermoe-
lectric EMF in measurement set-ups and test lead resi-
stance in two-wire resistance measurement.
Three integration times (0.1, 1, 10 secs.) and two display
modes (52 digits and 62 digits) can be selected via key-
board , IEEE-Bus, or manual control. An extensive start-up
self test routine with concise error messages checks all
analog functions of the instruments, including its digital
calibration state. Instrument calibration, manually or via
the IEEE-Bus, is straight forward, and does not require
removal of the case. Calibration constants for all ranges
are stored in a non-volatile memory.
6% Digit Display with 14 mm LED 2 1.999.999 digit
Resolution: 100nV, 1 m2, 10nA — Digital Offset Correction
10 Measurements per Second; Programmable Measuring Time from 0.1s-10s
IEEE-488-Bus standard — Built-in Self Test Function
High Input Resistance: 1G® (0.2 V and 2V range)
Electronic Calibration via Keyboard or via IEEE-488-Bus for all Ranges
Optional builtin 4-pole 10-Channel Scanner, Controllable via Keyboard or IEEE-488-Bus
Trigger Input for Manual or Controlled Triggering
The HM 8112 incorporates a talker/listener IEEE-Bus inter-
face as a standard feature, allowing controlled measure-
ments and calibration in all ranges. Full system integration
and compatibility with all currently available controllers is
ensured by a variety of programming and control com-
mands. This includes a selection of 9 different terminating
character combinations.
When set to “talk only” mode, all measurement data and
parameters can be transferred directly to the “Listen
only” printer for documentation purposes, without neces-
sity for an external controller or any specific software.
The HM8112's measurement versatility can be enhanced
further by an additional 4-pole/10-channel scanner option.
This measuring point selector can be activated manually
via the front panel, or by remote control via the |[EEE-Bus.
Special high quality long-life switch contacts, rated for cur-
rents up to 3A, ensure low resistance and unusually small
thermoelectric EMF of less than 1uV.
Wherever there is a requirement for fast and above aver-
age measurement accuracy, combined with high reliability
and ease of operation, the HM 8112 is an ideal solution for
monitoring and registering electronic measuring data.
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HIFAFIE I
Specifications HM 8112 (Ref temp. 23°C + 2°C)
DIRECT VOLTAGE Voc
Ranges: +0.2V, +2V, +20V, +200V, +1000V*
Accuracy: * * Temperature
24h, 23+1% 1 year, 23+5*C Coefficients”
Range %rdg. %fs. “%rdg. %fs. *[%rdg.+ %f.s.]
+0.2V 0.005 0.0007 0.012 0.0007 0.001 0.00015
+2 0.003 0.0005 0.010 0.0005 0.0003 0.0001
+20V 0.005 0.0015 0.012 0.0015 0.001 0.0001
+200V 0.005 0.0015 0.013 0.0015 0.001 0.0001
+1000V 0.005 0.0015 0.013 0.0015 0.001 0.0001
Integration Times: 0.1sec. 1+ 10sec.
Fullscale: 199.999 1.995.999
1000V Range 100.000 1.000.000
Resolution: TuV 100п\/
Input Resistance: +0.2V, £2V 1GQ
+20v, +200v, +1000 V 10MQ
Zero Stability: Temperature drift less than 0.3uV/°C
Long term stability better than 5uV in 90 days
Measuring gaps: None. 125ms for range or function changings.
Overload Protection: (between ,V/Q-HI" and , V/Q-LOW")
+0.2V, +2V ranges: for 80sec. +1000V"
continuous + 700V" |
+20V, +200V, +1000V ranges = : continuous #1000V"
Between ,V/Q-LOW" and GUARD : 125V DC or AC, eak
Between GUARD and case : 125V DC or ACpeak
Interference Rejection
(Measured by increasing the peak-peak interference signal level
until a display error of 1 digit results with 1 sec. measuring time).
Series mode interference rejection
50 Hz/60 Hz power line frequency...... : better than 60 dB
Common mode interference rejection (connected to one input ter-
minal via low resistance path, 1k inserted in series with one input
lead) DC or 50/60HZz..................—....—.... 140dB
ALTERNATING VOLTAGE Vac
Ranges: 0.2V, 2V, 20V, 700V#
Conversion Method:
True RMS value with DC coupling of the input sockets.
Input Resistance: 10M 11 <60 pF
Transient Response Time: 0.5s 100.1% гад.
Overload Limits:
Input V/Q : 41000 Vpeak O7 700 Vers
with the restriction of 10’V-Hz“
Between GUARD and case : 125V peak
Between , V/Q-LOW" and GUARD : 125 V peak
Accuracy: +[% of reading (% rdg.) + % of full scale (% f.s.)]"
(1 year, 23 + 5°С)
Range DC 20Hz 10kHz 20kHz 100kHz
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2V ........05+03......... 0,3+0.1.7::2 404515 3+0.4.........
20 sua TO 3 cua FO ac EO Arras I+0.4.....00.
200\ aus 0.5+0:3.........0.3+0.1........5+0.4........8+0.4.........
700\ .........0.5+0.3........(ОС- 100 Нг)
Temperature Coefficient:
10°C to 18°C and 28°C to 40°C / x2 at 0°C-50°C
kHz + [% rdg. + % f.s.] °С
0-20 0.01 0.004
20—100 0.04 0.005
Integration Times (sec.): Selectable ОТ
Full Scale: 199.999 (700.00 in the 700 V range)
Crest Factor: 7 :1 peak value (max. 1.5xf.s.)
1
Shield connected to ,V/Q-LOW?" input socket, sinusoidal signal
greater than 5% of full scale.
Restricted to 125 V,cax With a max. 10°V-Hz when the scanner is
incorporated.
3 +[% of reading (% rdg.) + % of full scale (% f.s.)]
4 +1 Digit after offset correction (rdg. = reading / f.s. = full scale)
* 10°C to 18°C and 28°C to 40°C / x2 at 0°C-50°C
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MULTIMETER HM 8112
CURRENT mA= mA—
Ranges: +2 mA, +2A 2mA, 2A
Integration Times (sec.): 0.1: 1:10 0.1: 1: 10
Full Scale / Resolution: 199.999/10nA 199.939/10nA
Accuracy: (1 year, 23+5°C)" DC 20 Hz-20kHz
Ranges 2 mA and 2 А 0.05 + 0.005 0.5+0.07
Temperature Coefficient:'” 0.002 + 0.001 0.01 + 0.004
Maximum Burden: Range 2mA : <10mV; 2A : <600 mV
Overload Limits: 250V (3A fuse protected)”
Crest Factor: 7:1 (Peak value max. 1.51.5.)
Transient Response Time: 0.5 sec. to reach final value within 0.1%
RESISTANCE k€2
Integration Times:
Full Scale/ Resolution:
0.1 sec. 1 +10sec.
199.999/1 mE 1.999.999/1 ma
1.200.000 (10M£2 range)
Accuracy: * * Temperature
24h, 23+1°C 1 year, 23+5°C Coefficients”
Range %rdg. % fs. %rdg. %fs. 1% гад. + % 1.5.
200Q 0.01 0.002 0.015 0.003 0.002 0.0005
2kQ 0.006 0.001 0.015 0.002 0.0015 0.0005
20kQ 0.005 0.001 0.015 0.002 0.0015 0.0005
200 k&2 0005 0001 0.015 0.002 0.0015 0.0005
2MQ 0.006 0.001 0.015 0.002 0.002 0.0005
10MO 0.05 0.003 0.1 0.0066 0.01 0.0005
Current through measured resistor:
Range 20092, 2kQ 0.7mA
20kQ 70uA
200kQ 7 uA
2MQ, 10MQ 0.7 uA
Open circuit terminal voltage: approx 14V max.
Overload limit: +300 Vea; (125 peak WIth Scanner)
SCANNER / MULTIPLEXER
Channels / Contacts per Channel / Function: 10/4/10f10
Thermoelectric EMF: Less than 1uV after 1.5h warm-up time
Max. Voltage: 125V,,,, or 10°V-Hz (whichever is less)
Max. Switch Current: 3A
Time between 2 switching actions: Shorter than 100ms/2Hz
Max. Contact Resistance (initial value): Less than 20mQ
Contact Life: 2x100.000.000 switching actions (0.1 А, 10 Мос?)
Insulation Resistance: 3 GQ at 60% relative humidity
Capacitance between the Contacts: <100pF
IEEE-488-BUS INTERFACE
Supported IEEE-488-Bus Functions:
SH1/AH1/T5/L3/RL1/DC1/DT1/SR1
Output Data: Numerical data for measurement result, function,
range, and integration time.
Input Data: Function, range, integration time, startcommand,
nominal calibration value.
Address: Selectable from 0 to 30, can be set via keyboard.
Terminator: 9 combinations available for selection.
General
Warm up time: typ. 90min. to specified accuracy.
Power requirements: 110/220V + 15%; 45-60Hz; 17VA
Ambient temperature: —40°C to + 70°C (storage)
+10°C to +40°C (operation)
Humidity: 10% — 75%, no condensation
Dimensions: 285 x75x365 mm (WxHxD). Weight: approx. 4 kg
Safety: Class |, according to IEC 348
The .,V/@-LOW" socket and the ,A-LOW”" socket are connected
together internally. The maximum permissible current between
these sockets is £0.1A (fuse 0.1 A).
Values without tolerances are meant to be guidelines and repre-
sent characteristics of the average instrument.
Control elements
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1 Power switch
2) 2nd: Switches to the second function level of the keyboard.
3) IEEE-Key: To set the device address, the end character and cal-
ling the trigger mode, in conjunction with the up and down keys.
MUX-Key: Channel selection for the 10-channel scanner option
by means of the 2nd-Key.
4. PRG: To set the integration time (measuring time) bet-
ween100ms and 10 sec. by means of the up and down keys.
The selected time is displayed together with the appropriate dis-
play resolution,
ZERO: Offset correction for compensating thermoelectric EMF
or measuring lead resistance.
5) kQ (measuring function): To select resistance measuring func-
ton.
6) V=/V~ (measuring function): To select the voltage measuring
function.
VAC is selected in conjunction with the 2nd-key.
) mA=/mAÂ-— (measuring function): To select the current measu-
ring function.
mA~ is selected in conjunction with the 2nd-key:.
8) Auto: Switches to autoranging for all measuring functions.
CAL: Together with the 2nd-key switchover to the digital calibra-
tion mode, after unlocking the protection switch on the rear panel.
9) Y :Manual range selection (down key)
10 æ: Manual range selection (up key)
17 Display: 8-digit LED display for alphanumerical readout of the
measured values and device messages,
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12 kQ (LED state indication): ON vwhen resistance measuring func-
tion is selected.
(3 Auto (LED state indication}: ON when autorange is selected.
(4 IEEE (LED state indication): ON when |EEE-Bus setting mode is
selected.
This mode enables the user to set the IEEE-Bus device number,
the end character and to call the trigger mode, in conjunction
with the up and down keys.
a5 V (LED state indication): ON when V= or V~ measuring func-
tions are selected.
16 2nd (LED state indication): ON when the second function level
Is selected (MUX/ZeroV—/mA-—/Cal.).
(7 mA (LED state indication): ON when mA= or mA~ measuring
functions are selected.
18 Input terminal (high) for voltage and resistance measurements.
a9 Input terminal (high) for current measurements.
20 Guard terminal: Guarding technique gives high rejection factor
for series mode interference, even under adverse measuring
conditions.
21) Input terminal (low) for voltage and resistance measurements.
@2 Input terminal (low) for current measurements.
23 External trigger input.
24 Pushbutton for manual triggering of a single measurement.
Rear panel elements: Mains connector with voltage selector (110/125/220/240V) and fuse holder: IEEE-488-Bus connector: Calibration
data protection switch; 10-channel scanner input {Option).
A recessed switch gives protection against unintentional changes of the stored calibration factors. Recalibration is only possible after
selecting the calibration mode with this switch,
The 24pole |IEEE-488-Bus connector and the 50pole submimiature type D socket strip connector of the optional 10-channel scanner are
situated on the rear panel. An optional adapter card can be plugged into the scanner input, permitting screw terminal connection of mea-
suring lines, providing two antiparallel 3A clamp diodes for each current channel.
A 19" rack mount kit (HZ80) with 2 HU enables rack mounting of the HM 8112.
8112
Printed in West Germany
Subject to change without notice
Warranty
Before being shipped, each instrument must pass a 10 day burn-in and a
48 hour quality test. Most failures can be detected by means of
intermittend operation during this test. Nevertheless,a component may
fail, but only after a longer period of operation.
Hameg warrants that all products of its own manufacture conform to Hameg
specifications and are free from defects in material and workmanship
when used under normal operating conditions and with the service
conditions for wich they were furnished.
The obligation of Hameg hereunder shall expire two(2) years after
delivery and is limited to repairing, or at its option, replacing
without charge, any such product which in Hameg's sole opinion proves to
be defective with the scope of this warranty.
This is Hameg's sole warranty with respect to the products delivered
hereunder. No statement, representation, agreement or understanding,
oral or written, made by an agent, distributor, representative or
employee of, which is not contained in this warranty will be binding
upon Hameg, unless made in writing and executed by an authorized Hameg
employee. Hameg makes no other warranty of any kind whatsoever,
expressed or imlplied, and all implied warranties of merchantibility and
fitness for a particular use which exceed the aforestated obligation are
hereby disclaimed by Hameg and excluded from this agreement. Under no
circumstances shall Hameg be liable to buyer, in contract or in tort,
for any special, indirect, incidental or consequential damages,
espresses, losses or delays however caused.
WARNING
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The optional Scanner is equipped with bistable relays, whose contacts
are in arbitrary state when the power supply is switched on or off. Thus
it is very important to make quite sure that the unit is switched on or
off only when no measuring cables are connected if the signal sources
can deliver voltages or currents which exceed the limit values specified
in the technical data for this unit (Limiting resistors will normally
help.) .
The arbitrary state of the relay contacts at switch-on or switch-off
time may short-circuit measured signals in an uncontrolled manner and
without due precautions this might damage your measuring circuit or the
scanner.
We expressly point out that we accept no liability for consequential
damage. Damage to the relay contacts 1s also not covered by our warranty
obligations.
Commencing Operation
Every HAMEG HM 8112 unit has been carefully tested in detail before
leaving the factory, to make sure that its function conforms to all
technical specifications. The unit should be in perfect electrical
condition on arrival at the customer. To verify this, the unit should be
HM 8112 HAMEG GmbH - Subject to change without notice —- Sept. 88
examined for transportation damage immediately on arrival. In the case
of grounds for complaint, a protocol of damage found should be drawn up
together with the deliverer.
Mains Connection
This HAMEG measuring unit is intended for connection to one of the
voltages 110V, 125V, 220V, 240V, 50/60 Hz AC mains input voltage as
power supply. Make sure you have an instrument that corresponds to your
power line voltage! |
When changing the line voltage please open up the instrument and set the
jumpers on the mains pcb to the position corresponding to the line
voltage desired. (Fig. 1)
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HANMEOG Le HM 8112 С Fuse type: Size 5x20 mm; 250V~, C;
instruments IEC 127, Sheet lil; DIN 41 662 (possibly DIN 41 571
sheet 3).
Cutoff: time lag (T).
Fig. 1 MAINS setting PCB
Voltage fluctuations of +/- 10% and frequency fluctuations of +/- 4% are
tolerated. The power consumption is about 17 VA. A cold equipment mains
connector with grounding contact, conforming to DIN, 1s located on the
rear of the unit. The unit is protected by a slow blow 0.1 A(220V, 240V
line voltage) or 0.2 A(110V/125V line voltage) miniature fuse.
Grounding
To protect the user against possible electric shock, the case of the
unit must be grounded by connecting the mains cable to a suitable power
outlet with grounding contact. The case is electrically isolated from
the shield and from the two input sockets.
Any interruption of the protective conductor inside or outside the
instrument is likely to make the instrument dangerous. Intentional
interruption is prohibited.
When removing or replacing the metal case, the instrument must be com-
pletely disconnected from the mains supply. If any measurement or
calibration procedures are unavoidable on the opened-up instrument,
these must only be carried out by qualified personnel acquainted with
the danger involved.
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Keyboard and Integration Setting
The ten element keyboard is double-assigned. All functions marked above
the keys are activated by single actuation of the respective key. All
functions marked beyond the keys are called by first pressing the "2nd"
function key and then the respective function key. The LED marked "2nd"
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
is always lit too when a "2nd"- function has been selected, 1.e. it is
lit together with the LED which is designated with the corresponding
function.
The functions direct voltage "V=", alternating voltage "Vac", direct
current "mA=", alternating current "mAac" and resistance "KOhm" are
selected by pressing the respective key. |
Range selection is automatic when the "Auto" key has been pressed, or
manual with the range keys (up and down keys). When one of these keys is
pressed, the autoranging function is switched off and the active range
is switched one step up or down for each keypress.
The fast autoranging function makes a preliminary decision within the
first third of the set measuring time, wether the active range 1s the
correct one. If the set range is retained after the preliminary decision
(fast autoranging), then two further checks are made after elapse of the
complete measuring time:
1. The next higher range is selected if the span limit is reached or
exceeded.
2. If less than 8% of the set span is reached, then the next lower
range is selected. The next measurement then commences in the new
range 100 msec after switchover.
When range selection is made via the rear input (see section headed IEEE
488 bus interface, then the range keys on the front panel are disabled.
The control unit is electrically isolated from the input.
A brief measurement with reduced accuarcy is inititated in response to
each keypress and each range change, when autoranging is switched on.
The brief measurement takes 200 ms and produces no service request when
SRO is selected in IEC bus operation.
After pressing the "Prg" key, "Pl" appears in the display for about ls.
If the "Prg" key is pressed again within the 1s delay time, then "P2"
appears, again for 1s. "P1" and "P2" stand for Program 1 and Program 2.
If no key is pressed during the 1 second delay time, then the programs
are executed.
Program 1: Setting the integration time
Program 2: Switch-on, switch-off of the external trigger facility
The up and down keys are used to set the integration time. The following
measuring times are available:
0.1 SEC. ......... 100 ms integration time, display 5 1/2 digit
1 - 5 зес. ......... 1 s integration time, display 5 1/2 digit
1- 6 зес. ......... 1 s integration time, display 6 1/2 digit
10 вес. ......... 10 s integration time, display 6 1/2 digit
Pressing any other key exits this program and the integration time
standing in the display at this instant is taken over for deter-
mining the measured values.
Switch-on and switch-off of the external trigger facility is made with
the "up" key. The display shows "trig on" or "trig off", after alternate
presses of the "up" key. Pressing any other key exits the program and
the last displayed status is taken over. If start mode has been chosen,
then the actual measured value appears in the display.
"cal", "Zero", "IEEE" and "MUX" are described in corresponding subsections
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Digital Display
The measurement results with decimal point, the negative sign and error
messages are shown on the digital display of the digital multimeter.
Certain operating modes of the multimeter are indicated here too. The
active function and the operating mode are indicated by LEDs marked with
the corresponding functions.
Offset Correction
Zero point displacement (drift) is one possible source of error. Normal-
ly this type of error is immediately evident by a display reading dif-
fering from Zero when the input is shorted. A zero point correction can
be made with the "Zero" key. For this purpose place a short circuit at
the "Vohm" input and then press the "Zero" key. The instrument makes a
zero point measurement whose duration is determined by the set integra-
tion time. With 6 1/2 digit display, the zero point measurement takes
20 seconds in the functions "Мас", "mAdc", during which time the display
shows "null" and the remaining time in seconds until the end of the
measurement. With 5 1/2 digit display, the zero point measurement takes
2 seconds and only the text message "null" appears in the display. The
keyboard is disabled during the correction measurement.
Deviations up to 1% of the measuring range span can be corrected. If the
deviation exceeds this limit, then the message " Error 4 " appears in
the display and on the IEEE 488 bus, and the old correction value is
preserved.
The sequence of the correction measurement differs slightly from the
description given above, for the functions "KOhm", "Vac" and "mAac". For
these functions the zero point is corrected immediately by continual
observation of the measured value. If autoranging was switched on before
calling the zero point measurement, then all ranges of one function are
corrected in succession for zero point. Now the zero point measurement
takes 10 seconds for each 6 1/2 digit display span, and 1 second for
each 5 1/2 digit display span. When the measurement duration is 10
seconds, the display shows "null" and the remaining time. When the
measuring time is 1 s, only the text message "null" appears in the
display. For the current measuring ranges, the zero points are corrected
with open-circuit sockets.
No short circuit; active current sink circuit!
No short circuit is placed internally in the multimeter for the offset
correction, so that the user can place the short circuit at any desired
location in the external circuit, to include external error sources in
the compensation. This is particulary important for the 2-wire resis-
tance measuring function. The error due to the finite resistance of the
measuring leads can be eliminated by the offset correction.
Error Messages and Self-Test
Self-Test
The digital multimeter executes an automatic self-test routine on mains
power-up. Progress of the individual test routines is indicated in the
main display by the message "Contr.1-3".
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
If an error occurs during the self-test, this error is reported by a
corresponding error message and the multimeter aborts further execution
of the self-test routines. To resume execution of the self-test routines
press any key. No voltage greater than 300 V may be present at the input
sockets of the multimeter during self-test.
Contr. 1 initializes the multimeter and checks for correct
functioning of the analog section.
Contr. 2 forms a checksum of the calibration factors stored in
the battery backed up RAM and compares this
recalculated checksum with the old stored value.
Contr. 3 forms a checksum for the program ROMs and compares this
recalculated checksum with a stored control checksum.
Error Messages
The digital multimeter recognizes the following error situations caused
by incorrect operation or manual control. They are reported in the main
display and via the IEEE 488 bus with the designation "Error" and a code
number. The code numbers have the following meanings:
1 - Overflow for measurement: The reading exceeds the allowed range
4 - Error during offset measurement: The offset is too large
5 — Error during calibration:
1. Nominal value smaller than 5% or greater than 100% of range
2. Calibration switch on the rear of the unit is set to "MEAS".
6 — IEEE 488 bus interface error: The multimeter has
received a message string containing more than 30 characters.
8 — Error during self-test 2: The redetermined and the old
check sum do not agree (lithium battery exhausted).
9 - Error during self-test 3: Error in the program ROMs.
Operation Instructions for Direct Voltage Measurements (V=)
Connect the voltage to be measured to the two input terminals marked
"V/Ohm” and ground on the front panel. A voltage which is positive at
the red socket relative to the black socket gives a positive readout in
the display. |
Make sure that the maximum permitted values of the "LOW" input and guard
(see section "shielding"), and 500 V DC or peak-peak AC between guard
and case, are not exceeded. This condition must be taken into consider-
ation when selecting polarity for high voltage circuits which are not
isolated from the power mains.
Input resistance 1 C ranges
In order to make full use of the excellent linearity of the measuring
method, the input resistance for voltage measurement is extremely high
in some ranges. For example, this still permits relatively accurate
measurements up to +/- 2 V even when the internal resistance of the
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
measured voltage source is 100 kOhm. In the 20 V, 200 V and 1000 V
direct voltage measuring ranges, 100 Ohms internal resistance of the
measured voltage source already give an error of 1 digit when using
100,000 digits resolution. For input resistance, display span and
resolution see the following table:
Range Display span Input Resistance max.Resolution
0,2 V . 2000000 У 1 GOhm 100 nV
2 Vv 2.000000 у 1 GOhm 1 uv
20 V 20.00000 V 10 MOhm 10 uV
200 Vv 200.0000 V 10 MOhm 100 uv
1 000 V 1000.000 V 10 MOhm 1 mV
Overload Protection
All ranges are effectively protected against destruction by voltages
greater than the full-range value. The max. overloads in this sense are:
+/-0.2V,+/-2V ranges: +/- 1000V for 60 sec or +/- 700V cont.
+/-20V, +/-200V, +/-1000V ranges: +/- 1000V continuous
However, bear in mind that heavy overloads in the lower ranges will
inevitably cause heat-up of the safety resistors and diodes, so that
subseguently thermoelectric EMFs may cause a zero displacement until
internal temperature equilibrium has been reestablished.
Common mode supression
The common mode rejection of a measuring unit is the capability of
indicating only the wanted difference signal between the "HI" and "LOW"
input, with ideally complete supression of any response to a common
voltage which both input terminals may have with respect to ground.
Whereas an ideal system would give no response to a common mode signal,
so that it would show no error due to this cause, in a practical system
stray capacitances, finite insulation resistance and resistive circuit
assymmetry will convert a portion of the common mode voltage to a series
voltage. The common mode rejection factor of this multimeter is better
than 140 dB when the resistive asymmetry of the measuring leads has any
value up to 1 kOhm.
Shielding
If problems due to common mode voltage are expected in a given measuring
task, then the guard input (blue socket) should be strapped to the "LOW"
input (black socket).
A high rejection factor for direct voltage and common mode voltage can
be obtained in critical cases by appropriate connection of the guard
input. Common mode voltages are voltages which occur between the low
point of the voltage to be measured and mains (power) ground, or between
power ground of the voltage source and ground potential of the measuring
unit. Common mode voltages attempt to send currents in the same direc-
tion via both input sockets. For optimum shielding effect, connect the
guard input to a direct voltage potential equal to that of the "LOW"
input such that currents flowing in the shield do not flow through
resistances in the voltage source circuit and voltage measuring leads,
which could disturb the voltage being measured. |
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Operating Instructions for Alternating Voltage Measurements Vac
The digital multimeter measures the true RMS value of the input voltage,
i.e. the RMS value of the applied direct and alternating voltage.
A recommenced arrangement for measuring alternating voltages consists of
a two-conductor shielded cable with the shield connected to the "guard"-
input. For all measurements, the "guard" and the "V/Ohm-LOW"-input
should be connected to the measuring point which lies closest to ground
potential.
Somewhat poorer shielding is achieved by using a single coaxial cable
and establishing a link between the "guard" and the "V/Ohm-LOW"-input.
This often used arrangement is nevertheless satisfactory for most mea-
surements except in very high ambient noise levels and/or when measuring
very small voltages.
In the 200 V and 1000 V ranges and when measuring alternating voltages
with high frequencies (above 100 kHz for the 200 V range or above 10 kHz
for the 1000 V range), it must be ensured that the applied alternating
voltage does not exceed the RMS value product of 10 million V*Hz.
Measuring Direct Current mAdc and Alternating Current mAac
When connecting the measuring circuit to the DMM, bear in mind that the
two black "LOW"-sockets of the inputs "V/Ohm" and "A" are connected
together internally. Thus it is not possible to connect simultaneously
two measuring leads for current measurement and two leads for voltage
measurements, if there is a potential difference between the respective
measuring points. The internal connection between the "V/Ohm" socket an
the "A"-"LOW" socket is protected against current overload by a 0.1 A
fuse (slow blow).
Offset correction by keypress is possible for the current measuring
ranges too. But in contrast to all other functions, the offset correc-
tion for current measuring ranges must be made with the input sockets
open circuit (see also the section headed "offset correction”).
A 0.1 Ohm shunt is used in the 200mA range. But in the 2 mA range a
current compensation circuit is used which permits load voltages smaller
than 1 mV. The current measuring ranges are protected by power diodes
and an additional quick blow 3 A fuse.
Before replacing blown fuses, disconnect the mains plug and all
measuring cable plugs.The 3A (quick blow) fuse is located near the input
sockets of the instrument and the 0.1 A (slow blow) fuse is located
close to the large blue 0.1 Ohm shunt at the front right inside the
instrument.
Operating Instructions for Resistance Measurements kOhm
Resistance measurements with this multimeter are made according to the
following principle: A load-independent current (I) is passed through
a resistance (Rx) which is to be measured. This current also flows via
a known internal range resistor. The voltage drop across Rx is measured
via the input sockets "V=" and the ratio of this voltage drop to the
voltage drop across the internal range resistor is determined. Thus any
drift or ageing of the reference voltage source has no effect on the
accuracy of the resistance measurements.
The digital multimeter makes resistance measurements in 2-wire circuit.
For measuring small resistances too with high accuracy, careful compen-
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
sation of the measuring lead resistances and of thermoelectric EMFs 1s
required, with the aid of the offset correction facility.
For this purpose connect the two measuring leads with their test clips
to one side of the resistor to be measured, and then make offset correc-
tion by pressing the "Zero" key. This correction compensates for all
possible sources of error, such as measuring lead resistance, contact
resistance and thermoelectric EMFs. Shielded measuring should be used
when measuring large resistances (100 kOhm or greater). Connect the
shield to ground potential, to prevent errors due to foreign voltages
(mains ripple).
The currents trough the resistance to be measured have the following
values in the respective ranges:
2 kOhm-range 700 uA
20 kOhn-range 70 uA
200 kOhm-range 7 uA
2 MOhm-, 10 MOhm-ranges 0,7 uA
The polarity of the current flowing trough Rx is defined such that the
end of Rx which is connected to the upper "HI" socket of the "V/Ohm"
input has a negative potential with respect to the other end of Rx.
Operating Instruction for 10-channel 4-pole Scanner/Multiplexer (Option)
When the DMM has been equipped with the scanner option, the maximum
permitted voltage at the subminiatur type D 50-pole socket on the rear
or at the "V/Ohm"-input sockets, is 125 V peak-peak, with the restric-
tion for the RMS product to be lower than 1 Million V*Hz.
The optional Scanner is equipped with bistable relays, whose contacts
are in arbitrary state when the power supply is switched on or off. Thus
it is very important to make quite sure that the unit is switched on or
off only when no measuring cables are connected if the signal sources
can deliver voltages or currents which exceed the limit values specified
in the technical data for this unit. The arbitrary state of the relay
contacts at switch-on or switch-off time may short circuit measuring
signals in an uncontrolled manner and without due precautions this might
damage your measuring circuit or the scanner.
The multiplexer is of type "1 of 10", i.e. one freely selectable channel
at a time can be connected through. The inputs are collected on a 50-
pole subminiature type D socket connector mounted on the rear of the
unit. The 4 output lines of the multiplexer are connected internally to
the multimeter input terminals "V/Ohm" and "A". The front terminals too
can be switched-in and switched-out via the IEEE 488 bus interface. When
the front terminals are switched-in, they too are connected to the "V,
KOhm" and "A" inputs of the multimeter. The front terminals are in
switched-in state immediately after power-up of the DMM. For operating
instructions for this function see section headed "IEEE 488 bus".
A shield is provided separately for each multiplexer channel and 15
connected to the "guard" terminal on the front of the unit and to pin 1
of the subminiature type D socket connector. An adapter card is also
available which plugs onto the subminiature socket connector and
provides screw terminal connections for the multiplexer inputs.
Channel selection can be made via the keyboard as well as via the IEEE
488 bus. After pressing the "Mux"-key (first press "2nd" and then press
"Mux"), the presently selected channel is shown in the display.
A new channel can now be selected with the range key. The ten channels
are numbered consecutively from 0 to 9. Between channels 9 and O there
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
is a state with indication "-" in the display, corresponding to the
state "multiplexer switched off". To exit this program and connect
through the selected channel, press any other key.
Channel selection is made via the IEEE 488 bus interface using the
command "MX" (see section headed "IEEE 488 bus interface").
input terminals D-Subminiatue
to DMM
3 à 8 Connector
LO
oo о q be 7
V/A Hi Le ==. AY pe | LS $b ———— KO
, — т” Cama) 148
O 49
O 50
LO и |
E
1
A Hi Do R?
O0" —+
Channel: | KO K1 K2 K3 K4 K5 K6 K7 K8 K9
a LO lumen 9 7 5853
pat H 48 16 14 12 10 8 6 42 Connector
LO 69 33 31 29 27 25 23 21 19 34 Cone
terminals Vv/ 4 50 32 30 28 26 24 22 20 18 35 ‘contact pian
—o1 —_ 03
н — -+ == — a> K9
© 37
O 34
O 35
Guard
O- A DN
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
EXTERNAL TRIGGERING
The digital multimeter can be triggered for a single measurement via the
BNC-Connector on the front panel or by means of the trigger key. Another
start mode under software control is posible too, via the IEEE 488 bus.
All start modes have the same time sequence.
If program 2 (see the section describing the keyboard) has placed the
digital multimeter in "trig on" status, single measurements can be
started via the trigger socket or the trigger key. The start time is the
rising flank of a trigger pulse with a time jitter not exceeding 25 ms.
Via the IEEE bus, the digital multimeter is placed in start mode by the
command "S1". Each further transmission of "S1" then corresponds to a
trigger as described above. The digital multimeter can also be started
by the addressed command GET (Goup Execute Trigger). The display and the
IEEE message are refreshed at the end of the measuring time. If service
request is switched on, then the SRQ line is activated. In "TALK ONLY"
mode, the digital multimeter sends a message to a connected device in
"LISTEN ONLY" mode. Range and function switching operations carried out
shortly before triggering may lead to delay times of up to 225 ms.
Trigger
or
"51" сет |?
Measuring о
cycle integration time
|
Start Start End End
A to +25ms te te +25ms
- End of measurement
- Change of display
- SRG
- {EC-Message renewed
IEEE 488 - Bus - Interface
Capabilities of the IEEE 488 bus interface
SH1 Handshake source function
AH1 Handshake sink function
T5 Talker function
L3 Listener function
RL1 Remote control
DC1 Reset function
DT1 Trigger function
SR1 Service request function
Programming the Digital Multimeter via the IEEE 488 bus Interface
Set the device address using the numerical keyset of the digital multi-
meter. For this purpose, first press the "IEEE"-key . The digital multi-
meter is then in status "set device address". The display shows the
present device address setting, e.g. "IEEE.07.8" which means that the
unit is set at present to device address 7 and end character type 8. The
digital multimeter is set to this device address and end character as
delivered from the factory. The "07" in the display is flashing, to
indicate that the device address can now be changed.
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Use the "up" key to change the device address. The first actuation of
this key starts a cyclic run-through of device addresses from 01 to 30.
After address 30 the characters "--" appear in the display for operating
status "TALK ONLY". When the desired address or "TALK ONLY" 1s reached,
the process is stopped by pressing the "up" key again. To select the end
character by its designation number, press the "down" key. The digit
after the decimal point now flashes, indicating that the end character
can now be changed. Selection of one of nine possible end characters is
made with the "up" key in the same manner as for selecting the device
address.
The following terminating characters and combinations are available
Designation number Terminating character (Combination)
О CR + EOI
1 CR
2 LF + EOI
3 LF
4 CR + LF + EOI
5 CR + LF
6 LF + CR + EOI
7 LF + CR
8 EOI
The desired device address including the designation number of the
terminating character combination is now present in the display. Press
any key except a range key to transfer this address information into
working memory and exit the status "set device address".
If it is desired to take over these new settings into protected memory,
set the calibration switch on the rear of the unit to position "Cal"
before takeover of the address data.
x * x * x k KK
* DO NOT FORGET TO RETURN THE CALIBRATION SWITCH TO POSITION " MEAS " *
x à de Le Le de A de k k de de de de de x x e x e Le de à e e de k e X X loo k k k A x k K k e * * X X K x k x k kX x X X k k k k à x X K X k k k * X X
The new device address will now not be lost when the digital multimeter
is switched off. The keyboard of the digital multimeter is disabled
after the digital multimeter has been accessed once via the IEEE 488 bus
interface. The keyboard is enabled again when the "REN" becomes inactive
or when the controller transmits the addressed command GTL(go to local).
The "TALK ONLY" capability in conjunction with a printer with "Listen
Only" attribute, permits set-up of a self-complete measuring station.
After each end of measurement (e.g. after a trigger), the DMM outputs a
measured value with the selected terminating characters to the IEEE bus.
The DMM does not interrupt its continuous measuring sequence within the
talker function. It understands the commands DCL (Device Clear),
SPD (Serial Poll Disable), and SPE(Serial Poll Enable). The command DCL
sets the DMM into status "DC-Volts measurement with 1000 V range".
To program the DMM, proceed as follows: Data input is possible as a
character string of length 2 to 30 characters, e.g. "VDR3AO0M3Q1L1" or
"VDR3" or "R3". Every DMM command consists of two characters. The se-
quence of several commands within one string is arbitrary, with the
exeption of the command "NV" (see description of this command).
The ISO-7-bit code is used for command transfer. Any spaces in the
transferred string are ignored. If the DMM receives more than 30 charac-
ters (excluding any spaces), then it evaluates the first 30 characters
and also reports a transmission error (see section "error messages").
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Device Messages understood by the digital multimeter
VD Direct Voltage
VA Alternating Voltage
02 Resistance measurement, 2-wire circuit
ID Direct current
IA Alternating current
Ri Range 0,2 Vdc, Vac, kOhm, ... ....
R2 Range 2 Vdc, Vac, kOhm 2mAdc 2mAac
R3 Range 20 Vdc, Vac, kOhm ..
КА Range 200 Vdc, Vac, kOhm cee ....
RS Range 1000 Vdc, Vac, 2000k0hm, 2000mAdc, 2000mAac
R6 Range 10000 ег... 12000kOhm “ee. ....
АО (A/Zero) Autoranging off
Al Autoranging on
T1 Integration time 100ms; display 5 1/2 digits
T2 Integration time 1 s; display 5 1/2 digits
T3 Integration time 1 s; display 6 1/2 digits
T4 Integration time 10 s; display 6 1/2 digits
Z0 Zero
si Start mode, Start
SO (S/Zero) continuous measuring
LO (L/Zero) DMM transmits only measurement result
Ll DMM transmits measurement and programmed status data
90 (Q/Zero) without Service Request SRQ
Q1 with Service Request SRQ
NVXXXXXX Nominal value (for calibration)
MO Multiplexer switched off |
MO Multiplexer channel O selected (M/Zero)
M1 " H 1 11
M2 LA) 11 . 2 tr
M3 " 1 3 1"
M4 1" A) 4 1"
M5 117 11 5 1"
M6 LE sf 6 LA
M7 1 i? 7 LA}
M8 1" "" 8 1"
M9 "1 n g ye
CO (C/Zero) Front terminals switched-out
Cl Front terminals switched-in
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Description of the device messages
"VD" Selects the measuring function "direct voltage"
"VA" Selects the measuring function "alternating voltage".
"O2" Selects the "resistance" measuring function.
"ID" Selects the "direct current" measuring function.
"IA" Selects the "alternating current" measuring function.
"RX" The measuring range within each function is selected
With "RX". "X" stands for the designation number of the
desired measuring range. Note that some measuring ranges
can be selected only in conjunction with a corresponding
measuring function, e.g. R6 only for function "kOhn".
"AQ" (A/Zero) switches off autoranging.
"A1" switches on autoranging.
"TX" Sets the integration time and the number of digits shown
in the display for the measurement result.
6 1/2 digits are always transmitted via the IEEE 488 bus.
"zo" Starts an offset correction.
"so" (S/Zero) Starts the continuous measuring sequence.
sil" Stops the continuous measuring sequence. The delay until exe-
cution of the commands "SO" and "s1" may amount up to 25 msec.
"MX" Selects a multiplexer channel. "MO" switches off the multiplexer
"MO" (M/Zero) to "M9" select the respective multiplexer channels
"co" (C/Zero) disconnects the front terminals when scanner is fitted
cl" Connects the front terminals when scanner is built in
"LO" (L/Zero) Short format: The multimeter transmits only
the first data block (measurement data and text messages)
"LI" Long format: The DMM transmits both data blocks
(measurement data and text messages in first block and
programming data in second block).
"ОО" (Q/Zero): The multimeter transmits no Service Request SRO.
"О" The multimeter transmits a Service Request SRQ with:
- each new measurement result, each error message, reset
"NVXXXXXX" After NV the DMM expects a 6-digit unsigned decimal integer
number as nominal value for calibration via the IEEE 488
bus. A nominal value for calibration must be transmitted
alone, 1.8. no further command from the table above may be
contained in the same string. The DMM commences the cali-
bration measurement after receiving the nominal value.
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Description of the transmitted data set
The contents cf the display are transmitted in the 12 characters of the
first data block. These are measurement results and text messages. The
measurement results are always transmitted right justified, i.e. termi-
nation with the 12th character.
The first character is always the sign, "+" or "=", for direct voltage
measurements. All not required leading digits before the measurement
result are filled with zero. No sign is output for resistance, alterna-
ting voltage and current measurements and all not required leading
digits in front of the measurement result are filled with zero.
Measurement results are output in exponential form without spaces,
e.g. +01.9876E+2
The text messages have the format "ERR. X", "NULL", "CAL."
These messages are always left justified, 1.е. they commence with the
first character of the data block. All not required characters are
filled with spaces (blanks).
The second data block always commences with the 13th character. This
data block outputs the programmed status of the multimeter. Output of
the second data block can be enabled or disabled with the digital multi-
meter command "L1" or "LO" (L/Zero) respectively (see section headed
"Programming the digital multimeter via the IEEE bus interface").
Device Messages Transmitted from the Multimeter (IEC 625 Part2)
The device messages transmitted from the DMM consist of a data set which
is generated and transmitted as a block, with end specification. The
data set consists of two data blocks. The first data block contains
programming status data. Each data block consists of a character string
with a fixed number of characters, so that no end character is required
or sent between the two data blocks. The first character string contains
12 characters and the second character string contains 16 characters +
terminating character(s).
Tf character transmission from the DMM is discontinued before the DMM
has gone to TIDS status, transmission commences with the first character
of the data set after a new call.
The terminating character(s) of the data set are as chosen according to
the section "Programming the DMM via the IEEE 488 bus interface”.
The ISO-7-bit code is used for transmitting the device messages.
ist. character 28.th character
| |
+X . XXXXXXE+XVDRXAOTXS0QOCOMXEND
VA A1 S1Q1C1
02
ID
IA
(---------- ; --------------- )
1st. data 2nd. data
block block
+ Sign of mantissa for VD and ID,
Zero for VA,02 and IA
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
X. XXXXXX 7 digit mantissa
E+X l-digit exponent with sign
VD, VA,02,ID,IA Measuring function:
VD - Direct voltage
VA - Alternating voltage
O2 - Resistance, 2-wire-circuit
ID - Direct current
IA - Alternating current
R1-R6 Measuring range:
Ri = 0,2 Vdc, Vac, kOhm, «oe ...
R2 = 2 Vdc, Vac, kOhm, 2 mAdc, 2 mAac
R3 = 20 Vdc, Vac, - kKOhn, ce ce
R4 = 200 Vdc, Vac, kOhm, ... ...
RS = 1000 Vdc, Vac, 2000 kOhm, 2 Adc, 2 Аас
R6 = 10000 ..., ..., 12000 kOhm, ... “eo
AO, Al Autoranging (0(Zero) = off, 1 = on)
T1-4 Integration time, number of display digits
T1 100ms , 5 1/2 |
T2 ls , 5 1/2
T3 is , 6 1/2
T4 10s , 6 1/2
so, si Start, Stop
00, Q1 SRQ-status (0(Zero)=without, 1=with SRQ)
MO, MO-9 MO = multiplexer is switched off
MO (M/Zero)-M9 = multiplexer channel
0...9 selected
co, Cl Front sockets switched-out (C/Zero) or
Front sockets switched-in
END Terminating character(s) as selected when
setting the device address. For terminating
character No.8, EOI is transmitted together
with the final (26th.) string character.
Service request function (SR interface function)
The IEEE 488 bus interface of the digital multimeter is equipped with a
service request function (SR function, SRQ). The individual status bits
transmitted with a service request have the following meanings:
Bit 1: End of measurement
Bit 3: Overflow during measurement
Bit 4: Error messages
Bit 6: Reset
Bit 7: SRQ
Bit 1, end of measurement, can appear together with the other status
bits, in order not to falsify the SRQ in the case of fast measurement
sequences. |
Bit 6 appears with a reset, i.e after power-up or in the case of a
strong external source interference event. A reset always takes the
multimeter to basic status (DC, 1000V, etc.), so that the control com-
puter must reprogram the multimeter according to section 11.1 after
detecting a reset. |
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Programming examples for the IEEE 488 bus interface
Before the digital multimeter can be operated via the IEEE 488 bus
interface, the device address and the end character(s) must be set as
described at the beginning of this section. Address 7 and the end
character number 8 (only EOI) are recommended in the following examples
for Commodore and Tektronix computers.
Number sign (double cross) < = greater than
"at"“-character (5) = square bracket
Signs and Symbols: @
&
COMMODORE CBM 3032
Control of the DMM by CBM 3032. The DMM is listener.
100 print " your entry please "
110 input a$
120 open 1,7 "7" is the device address of the DMM
130 [email protected], as
140 close 1
Reading the character string with the CBM. The DMM is talker.
200 open 2,7 "7" is the device address of the DMM
210 [email protected],b$
220 close 2
230 print bs
240 goto 100=
TEKTRONIX 4051:
Control of DMM by Tektronix 4051. The DMM is listener.
100 PRI " YOUR ENTRY PLEASE "
110 INP AS |
120 PRI £ 7:AS "7" is the device address of theDMM
130 GO TO 100
Reading the character with the Tektronix 4051. The DMM is talker.
140 INP « 7:B$S "7" is the device address of the DMM
150 PRI BS
160 GO TO 100
HEWLETT PACKARD HP 85
The device address of the multimeter is 7, the end character No.5
Control of the DMM by HP 85. The DMM is listener.
130 PRINT " YOUR ENTRY PLEASE "
140 INPUT BS
160 OUTPUT 707;BS
190 END
Reading the character string with the HP 85. The DMM is talker.
530 DIM AS” (50%) choose string size at least 29 characters
550 ENTER 707;AS
580 DISP AS
590 END
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 38
HEWLETT PACKARD HP 87
The device address of the multimeter is 7, the end character 1s No.5
10 DIM AS “(407), BS “ (307) string size at least 29 characters
Control of the DMM by HP 87. The DMM is listener.
20 INPUT BS via HP 87 keyboard (voltmetercode), up to 30 char.
30 OUTPUT 707;BS string transfer from the HP 87 to the DMM
Reading the character string with the HP 87. The DMM is talker.
40 ENTER 707 ;A$ string transfer from DMM to HP87 (26-28 char.
50 PRINT AS
60 GOTO 20
HEWLETT PACKARD HP 87 (but now with SRQ)
The device address of the multimeter is 7, the end character is No.5
10 ON INTR 7 GOSUB 500 checks IRQ from IEEE 488 bus
20 DIM AS “ (307), BS ~ (407) string size at least 29 char.
30 Input BS entry via HP 87 keyboard
40 OUTPUT 707;BS string transfer from the HP 87 to DMM
50 ENABLE INTR 7;8 enable IRQ initiated by SRQ
60 GOTO ..... line number of user program
500 STATUS 7,1; W
510 P=SPOLL (707) transfer of the SRQ status register
520 IF P<63 THEN GOSUB 1000 (evaluation of register contents)
530 ENABLE INTR 7,8 enable IRQ initiated by SRQ
540 RETURN
1000 ENTER 707;AS read in the message from the DMM
1010 PRINT AS, P, "DEVICE NO.7"
1020 RETURN
P 9816 (200 Series)
1000 |xx*****x Data transmission HP 9816 *****
1020 !Declaration of variables
1040 COM / DMM 5000/ € Dmmnr, Setup$ “ (307), DISPLAYS “ (307)
1060 ! Adress assignment -- 7 = € Dmmnr
1080 ASSIGN & Dmmnr TO 707
1085 ON INTR 7,1 CALL Serialpoll
1100 READING THE DESIRED SETUP VIA THE KEYBOARD
1120 INPUT Setup$
1130 OUTPUT & Dmmnr ; Setup$S
1150 ! ENABLE INTERRUPT
1170 ENABLE INTR 7;2 !IRQ by appearence of an SRQ signal
1180 Haupt: !
1190 GOTO Haupt
1200 END
1230 SUB Serialpoll
1240 | CHECKS DEVICE FOR SERVICE REQUEST, READS IF REQUIRED AND
1250 ! RETURNS TO THE WAITING LOOP OF THE MAIN PROGRAM
1280 COM /Dmm5000/ & Dmmnr, Setup$ (307), DISPLAYS “ (307), P
1300 P=SPOLL ( € Dmmnr)
1320 IF P<63 THEN CALL Measval
1330 ENABLE INTR 7
1340 SUBEND
1370 SUB Measval
13930 !'READS IN THE PRESENT MEASURED VALUE FROM THE VOLTMETER
1410 COM/Dmm5000/ & Dmmnr, Setup$ (307), DISPLAYS “(30),P
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
142
143
144
50
60
70
80
90
100
HM
0 ENTER € Dmmnr; DISPLAYS
0 PRINT DISPLAYS, P
0 SUBEND
LE II with CCS Interface Module 7490
PRINT
PRINT "SET DMM 5000 TO ADDRESS 07.0 ."
PRINT
PRINT "WHEN YOU HAVE DONE SO,"
PRINT "PRESS THE RETURN KEY."
INPUT CS
DIM AS(30), BS(30) dimension the string arrays sufficiently large
PRINT:PRINT
PRINT "YOUR ENTRY PLEASE:"
INPUT BS
PR @3 initialize slot 3 for output
PRINT "&':" & switches to address mode; REN and ATN active;
' transmits listener address 7;
: switches back to Command mode;
PRINT "'";BS;"' the message 15 transmitted;
' switches text mode on and off;
PRINT "&G:" & switches to address mode;
G transmits talker address 7;
: switches back to Command mode;
PR 20 data from IEEE bus are printed directly on screen
INPUT "";AS read-in the message from the IEEE bus
IN @O
GOTO 20
8112 HAMEG GmbH - Subject to change without notice - Sept. 88
CALIBRATION
Allow a period of 2-3 hours to elapse after switching on, before commen-
cing calibration, so that the digital multimeter has reached thermal
equilibrium.
The DMM has a digital calibration facility which permits
individual range or complete recalibration. It is not necessary to open
the unit for recalibration. Recalibration is possible under front panel
keyboard control or via the IEEE 488 bus. The correction values from the
first calibration carried out in the HAMEG factory are stored in the
programm EPROM and in a CMOS RAM with a lithium battery as backup power
supply. The multimeter normally uses the correction values which are
stored in the CMOS RAM. The battery service life is about 10 years.
To prevent unintentional destruction of the correction values, they are
protected in memory by setting a recessed sliding switch S2 which is
above the IEEE- Bus connector at the rear of the unit. The settings of
this switch are marked "MEAS" and "CAL". To recalibrate the digital
multimeter, move the switch S2 with the aid of a small screwdriver or
similar tool from "MEAS" to "CAL".
The "CAL" operating mode is indicated by periodic appearance of the
legend "CAL" in the main display. In this status the correction values
stored in the CMOS RAM are unprotected and can be overwritten. If
correction values have been lost accidently by improper calibration
attempts and recalibration is not possible because no calibration stan-
dards are available, then the correction values which have been stored
by HAMEG in the program EPROM at the time of initial calibration of the
instrument, can be copied into the CMOS RAM. For this purpose, set the
mains switch of the multimeter once to "OFF" and then to "ON" again,
whereby the calibration switch on the rear side of the instrument must
be left in setting "CAL". Hereby the calibration correction factors are
automatically copied from the EPROM to the battery backed-up CMOS RAM
and all correction values for the input offset are cleared. Thus it 15
necessary thereafter to make new compensation of the input offset for
all functions and ranges.
For this purpose, place a short circuit at the input sockets "V/Ohm" of
the digital multimeter, select measuring function "Vdc" and "Auto" for
autoranging and then press the "Zero" key. The multimeter now corrects
all Vdc measuring ranges in automatic succession and places the found
correction values in the RAM which can subsequently be protected. To
correct a single measuring range, select just this range, leaving auto-
ranging ("Auto") switched off.
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Calibrating the Direct Voltage Measuring ranges
First select the measuring range which is to be calibrated and then
connect an exactly known positive or negative reference voltage to the
input terminals. This reference voltage should not be less than 5% or
more than 100% (preferably 50% to 100%) of the range span. The multi-
meter now displays a measurement result which has been calculated using
the old calibration factor. If this actual value differs unacceptably
from the nominal value (known value of the reference voltage), then call
the calibration program by first pressing the "2nd" function key and
then the "Cal" key. The nominal value can now be set using the "up" and
"down" keys.
The "down" advances the digit opened for correction. When the digit to
be corrected in the display has been reached, it starts counting
cyclically 0-9 by pressing the "up" key . This counting can be stopped
and started again with the "up" key. When all digits have been corrected
to the nominal value, start the actual calibration measurement by
pressing the "enter" key
"CAL." thereupon appears in the display and the remaining time of the
calibration measurement is counted down to Zero in the display, similar
to the sequence of events for a Zero point measurement.
Thereafter the unit exits the calibration program and new functions and
ranges can be selected. The calibration program is also aborted when any
other key except "up", "down" or "enter" is pressed, in which case the
old calibration factor is retained and no change has been made. To
recalibrate several measuring ranges individually, start the entire
procedure as described above for each range. After completing all
intendend recalibrations, make quite sure that the recessed switch S2 on
the rear panel of the unit is returned from "Cal" to "Meas", so that the
calibration data are protected again.
Calibration procedure via the IEEE 488 bus is basically analogous to the
described procedure via the front panel keyboard. The nominal value 1s
set as integer number with the command "NVXXXXXX" (see calibration
program in the section headed "IEEE 488 bus interface"). The calibration
program and the calibration measurement are started automatically on
transmission of the nominal value. When no further ranges and functions
are to be calibrated, terminate the calibration procedure by returning
the switch $2 on the rear panel of the unit from setting "Cal" to
setting "Meas".
Calibrating the Resistance Measuring Ranges
The resistance measuring ranges are calibrated in 2-pole circuit. First
connect the zero point by the procedure described in before. Also
observe the instructions given in the section headed "operating instruc-
tions for resistance measurements Ohm/kOhm", in particular regarding
compensation of the measuring leads resistance. Calibration procedure
for the resistance measuring ranges is otherwise analogous to calibra-
tion of the direct voltage measuring ranges.
Calibrating the Alternating Voltage Measuring Ranges
The alternating voltage measuring ranges should be calibrated with a
sinusoidal alternating voltage with a frequency of 1 KHz. For the
function Vac too, the zero point must be compensated with function
setting "zero". The calibration procedure is analogous to calibration of
the direct voltage measuring ranges.
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
Calibration of the Direct and Alternating Current Measuring Ranges
For the current measuring ranges too, make the same calibration prepara-
tions as specified before. The zero point measurement must be made with
open circuit input sockets (no short circuit).
Do not leave any measuring cables connected to the input sockets for the
zero point measurement (see also operating instructions for mAdc and
mAac). 1kHz sinusoidal reference currents are required for calibrating
alternating current measuring ranges. The calibration current (reference
current) must not be greater than 1 A in the 2 A range.
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* DO NOT FORGET TO RETURN THE CALIBRATION SWITCH TO THE POSITION "MEAS"
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ACCESSORIES
Mating Plug for Sub-D (HZ 82)
For connecting the measuring leads to the scanner, a 50-pole
subminiature type D plug can be used for each group of 10 channels.
This plug connector has soldered connections.
Adapter Card (HZ 81)
One adapter card can be plugged externally onto the 50-pole subminiature
type D socket of the HM 8112, for connecting the measuring leads at
screw terminals. The adapter card is also fitted with two antiparallel
3A clamp diodes for each current path, (see circuit diagram of adapter
card). These clamp diodes may be removed for other applications,
especially when switching currents greater 0.5A-peak shall be switched
(diode forward voltage drop!). One adapter card is required for connec-
ting all 10 channels.
Maximum current (without clamp diodes) 2 A
Maximum current (with clamp diodes) 0,5 A peak
Maximum voltage 40 V
Dimensions about 115 x 123 mm/4.5 x 4.8 in
Ve de Le x x x k k k k X
* WARNING *
kk kk kk kkk kk
Safety consideration
require that no voltages gereater than 40 V with respect to ground may
be connected, because the screw terminals are not protected against
accidental human contact entailing danger of electric shock.
HZ 72 IEEE-488-Bus-Cable, 60 inch
HZ 42 19" rack mount kit 2HU
HZ 15 Silicon test leads with test probes and sheathed banana plug
HZ 14 Test probe kit with two sprung hooks to stackup HZ 10 - HZ 13
HZ 13 Silicon test leads with fixed sheathed banana plug
HZ 12 Silicon test leads with stackup banana plug each end
(retractable sheath)
HZ 10 Silicon test leads with stackup banana plug each end. Set of 5
peaces (one color). Colors: red, black, blue, yellow, green
HM 8112 HAMEG GmbH - Subject to change without notice - Sept. 88
INTRODUCTION
These service instructions for the HAMEG Digital Multimeter 8112 are
intended as a supplement to the user manual, to give the experienced
electronics engineer the information required for maintenance, fault
tracing and repair of the instrument.
WARNING
The service tasks described here may be carried out only by qualified
technicians. When the cover of the instrument is removed, human contact
with points carrying potentially lethal voltages 1s possible. Thus the
following safety precautions must be observed.
a) Before opening the case, disconnect the mains plug and all connec-
tions at the measuring sockets.
b) Always use an isolating transformer when making measurements and
adjustments in the opened instrument.
с) When the instrument is in the opened state, connect only non-dange-
rous voltages to the measuring inputs.
This instrument is guaranteed to be in perfect condition when leaving
the factory. HAMEG accepts no liability for any damage caused by
incorrect operation or improper handling of this instrument.
WARNING
The analog section of the Digital Multimeter HM 8112 is aligned with
respect to alternating voltages. Replacement of components and especial-
ly replacement of the printed circuit board to repair the instrument may
make realignment and recalibration necessary. The data stored ain the
battery backed-up RAM may be lost during repair work, due to a short
circuit on the printed circuit board, disconnection of the RAM from the
battery or even by electrostatic discharge. As a general rule, any
repairs of the HM 8112 should be carried out only at a workplace which
is suitably protected against static electricity. Bear in mind that the
lithium battery may explode if it is short-circuited.
Functional principles of the HAMEG Digital Multimeter 8112
The measured signal is taken via the attenuator and via the preamplifier
to the converter. The converter transforms the analog signal into a
proportional pulse group which is sent via the "MEASUREMENT RESULT" line
(CB=U9, Pin 8) to the microprocessor circuit board. The pulses are
transmitted in basic state HIGH or LOW, depending on the polarity of the
measured signal. A sub-measurement is complete after every 25 ms. This
is reported to the SERIAL TO PARALLEL CONVERTER (U12) via the line "END
OF SUB-MEASUREMENT" (U9,Pin 11) by means of a pulse. The converter and
preamplifier offset of the measured data is subtracted in the micropro-
cessor section. The data are then multiplied by a calibration factor.
The subtrahend and the calibration factor are determined at the time of
zero measurement and calibration respectively (see user manual) and
stored in battery backed-up RAM. The results are then filtered by soft-
ware according to the set integration time and finally output to the
seven segment display and to the IEEE 488 bus. The data from the key-
board evaluator (U 4) are sent via (U 12) and Q 5 to the relay
control circuit (U 10), for function and range selection of the DMM.
Service Manual HM 8112 - Hameg GmbH - Subjekt to change without notice
Attenuator Preamp. ADC Microproc. Display
+rms „CB +CD
O UT
v/ >
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A
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Attenuator +CE EPROM RAM [EEE - 488
Range +
Function
ASSEMBLY / DISASSEMBLY
Microprocessor printed circuit board
Unsolder the transformer connecting wires from the mains PCB, the mains
ground connection from the floor of the case and the two connecting
wires of the trigger socket. Disconnect the plug connectors to the
display and analog circuit board. Remove the screws: 2 x IEEE 488 bolts,
4 x transformer mounting screws , 1 X screw on printed circuit board, 1
X screw on the 5 V regulator.
The heat dissipated by the 5V regulator (on the underside of the micro-
processor circuit board) must be removed by an adequately dimensioned
heat sink even when the circuit board is operated briefly in the removed
state (e.g. by a 40x100x20 mm ribbed heat sink). When remounting the
microprocessor circuit board, the case of the 5V regulator must be
attached to the case of the instrument in electrically isolated manner
(using the insulating nipple and the mica disc).
The washer, the insulating nipple and mica insulating disc below this
nipple on the 5V regulator must be remounted in this order.
Analog circuit board
Release the three mounting screws of the circuit board and the plugged
ribbon cable connection to the microprocessor circuit board (observe the
correct DIP-PLUG ORIENTATION). The analog circuit board can now be
folded out to the front for repair. To take out this circuit board
completely, it is also necessary to disconnect the five leads which go
to the display board (or to the scanner board).
Scanner circuit board (option)
Release the mounting screw of the printed circuit board and the plugged
ribbon cable connection to the analog circuit board (observe the correct
DIP-PLUG ORIENTATION). Unscrew the two bolts of the 50-pole subminiature
D plug) out of the rear panel of the instrument. The scanner circuit
board can now be pulled slightly towards the front panel and can then be
folded out upwards. To take it out completely, also disconnect the leads
which go to the analog and display circuit board.
Service Manual HM 8112 - Hameg GmbH - Subjekt to change without notice
Functional tests
Aids: 20 MHz single-channel oscilloscope (HM 203/204 or similar)
Auxiliary digital multimeter ( 6 1/2 digits)
Power supply voltages
Microprocessor circuit board:
+ SV: Power supply for the microprocessor board and for display board.
+/- 15V: Power supply for the analog board and for the scanner board.
A 5\ regulator on each of these circuit board produces another
internal power supply voltage from the +15V supply (U8 and U4).
The "DIGITAL" ground (5V supply ground) on the microprocessor board and
display board is electrically isolated from the case of the Digital
Multimeter and from the "ANALOG" ground (+/- 15V suppiy ground) of the
analog board and scanner board. Thus voltage measurements must be refe-
renced to the corresponding ground potential. The fourth line which 15
totally electrically isolated is the GUARD connection.
The 5V regulator (U 1) on the underside of the microprocessor board 15
screwed directly but electrically isolated (mica disc) to the case of
the instrument for efficient heat removal. R 1 and R 2 (each 10 Ohms on
microprocessor board) are safety resistors for the +/- 15V supply. К 1
and R 2 must be replaced after current overload (repair).
Analog circuit board
The +/- 15V supplies transferred by the plug connector between the
microprocessor board and the analog board, must be present at the refe-
rence element (U 4) on the analog circuit board: +15 V at pin 3, -15 V
at pin 2, analog ground at pin 4, the reference voltage of about 7V at
pin 1. +5V with respect to +/-15V "ANALOG" ground must be present at
the cathode of CR 4 and at pin 10 of U 9. An auxiliary voltage of 1.2 V
is also present at pin 6 of U 9.
Scanner circuit board
+15 V transferred by the plug connector between the analog board and
the scanner board, are present at pin 1 of U 1 and the generated +5 V
supply should be measured at pin 16 of U 3, in each case with respect to
+/-15V "ANALOG" ground.
DIGITAL SIGNALS
Microprocessor circuit board
CLOCK: The microprocessor clock signal (about 800 kHz) is generated in
U 9 on the analog circuit board and lies at U 9, pin 7. The opto-coupler
U 13, pin 6 transfers the "CLOCK" signal to the microprocessor board.
ERG: The RESULT signal lies at U 9, pin 8 on the amalog board. The
opto-coupler U 14, Pin 6 transfers the "ERS" (RESULT) signal to the
microprocessor board.
UME: The sub-measurement end signal lies at U 9, pin 11 on the analog
board. The opto-coupler U 15, pin 5 transfers the "UME" signal to the
microprocessor board.
Service Manual HM 8112 - Hameg GmbH - Subjekt to change without notice
U 16, U 17 and U 18 service the IEEE 488 ROUTINES. U 4 evaluates the
keyboard and handles the display elements.
Analog circuit board
The ranges and functions of the HM 8112 are set with BISTABLE relays
which are driven by HIGH (greater than or equal to 13 V) and LOW
(smaller than or equal to 0.6 V) signals at the outputs of U 10 (Pin 4,
5, $6, 7, 8, 9, 10, 12). U 10 obtains its data from the microprocessor
via the interface U 12 (Pin 18) and the opto-coupler Q 5 on the analog
board. When repair is necessary (Q5 defective), it may be necessary to
adjust the base resistor R38 (100K), to improve the transfer performance
of 05.
Scanner circuit board
U 1 on the scanner board is, amalogously to U 10 on the analog board,
responsible for the relay drive and thus for channel selection in the
scanner: HIGH (greater than or equal to 13 V) at pin 1 to pin 10 of U 1
connects through the respective channels 0 (KO) to 9 (K9). The relays Rl
and R2 are driven from U 1 pin 11 and pin 12. In instruments with the
scanner option fitted, R1 and R2 connect and disconnect the front panel
sockets.
ANALOG SIGNALS
Functional test for attenuator + preamplifier
Direct voltage measurement:
Switch the DMM to the Vdc function. Connect a reference voltage (e.g.
Uref = 1 V DC) to the V/Ohm input of the instrument. Using the auxiliary
DMM (6 1/2 digits), measure the voltage Uvv at the output of the pre-
amplifier (U3, pin 6) with respect to +/-15V analog ground. Switch
through the respective Vdc measuring ranges and in each case measure the
voltage Uvv. Table 1 lists the nominal values for Uvv in the respective
measuring ranges, for input reference voltages of 0.1 VDC and 1 VDC.
V DC Uref Uvv
Range Volt Volt
0.2 0.1 1.000
2 1 1.000
20 1 0.100
200 1 0.010
1000 1 0.001 Table 1
Resistance measurement
Switch the Digital Multimeter HM 8112 to the kOhm measuring function.
Connect a reference resistor (e.g. Rref = 1 kOhm) to the V/Ohm input of
the instrument. Using the auxiliary digital multimeter (6 1/2 digits),
measure the voltage drop Ua across Rref (see sketch). The current source
(U 1) produces the voltage drops Ua across the reference resistor as
listed in Table 2 in the respective measuring ranges:
Service Manual HM 8112 ~- Hameg GmbH - Subjekt to change without notice
KOhm-Range Rref/kOhm Ua/Volt
0.2 1 - 0.7
2 l - 0.7
20 1 - 0.07
200 1 - 0.007
2000 1 - 0.0007
10000 1 - 0.0007 Table 2
Current measurement
Switch the DMM HM 8112 to the mA DC measuring function. Feed a reference
current (e.g. Iref = 1mA) through the A input of the instrument. Using
the auxiliary digital multimeter (6 1/2 digits), measure the voltage Uvv
at the output of the preamplifier (U3, pin 6) with respect to +/-15V
analog ground. The readings listed in Table 3 should be obtained for the
two direct current measuring ranges (Iref = 1mA).
mA-Range Iref/mA Uvv/Volt
2 + 1 - 1.000
2000 + 1 + 0.001 Table 3
Integrator output signal
The integrator output signal can be measured at U 9, pin 12 with an
oscilloscope (with respect to +/-15V analog ground). With negative
direct voltage applied to the V/Ohm input of the Digital Multimeter HM
8112 , the oscillogram shown belowin should be obtained.
oo U
Integrator 9 INPUT
Output ov
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Service Manual HM 8112 - Hameg GmbH - Subjekt to change without notice
CIRCUIT BOARD REPLACEMENT
Aids
1. Replacement circult boards
2. "Extension": l6-pole ribbon cable, 50 cm long, fitted with DIP plug
on each end.
Execution
In the instrument which is to be repaired, disconnect the circuit board
which is suspected to be defective and connect a replacement circuit
board vía the "extension". When it has been verified in this manner,
which circuit board(s) is/are defective, replace it/them in the HM 8112.
The instrument must be recalibrated and a new Vac alignment made after
every replacement of a circuit board.
WARNING
Data may be lost in the course of repairs on the microprocessor circuit
board. Thereafter the HM 8112 may not start at all, or may start
incorrectly, after switch-on. In this case switch to "CAL" (CAL-MEAS
switch on the rear panel) and then switch the instrument off and on
again. Thereby bear in mind the following:
Offset correction values are erased permanently.
Calibration factors: The values for all ranges and functions which have
been determined in the HAMEG factory and stored in the EPROM, as well as
the initialization values for the IEEE address (07.8), for the inte-
gration time ( 1 sec, 5 1/2 digits) and for channel preselection (no
channel selected) are loaded into the battery backed-up RAM.
The analog circuit board must always be replaced together with the EPROM
which contains the specific calibration data for this circuit board.
When only the microprocessor board has been replaced and the "old"
analog board remains in the instrument, the corresponding "old" EPROM
with the calibration data for this "old" analog board must be inserted
again into the now "new" microprocessor board. The procedure for loading
the calibration data from the EPROM into the battery backed-up RAM 15
described in user manual for this instrument.
FREQUENCY ALIGNMENT
Aids: AC calibrator (voltage and current)
Auxiliary digital multimeter (6 1/2 digits)
Preparations
The offset of the rms value rectifier (TRUE RMS CONVERTER, U 5) must be
compensated before carrying out the frequency alignment of a Digital
Multimeter HM 8112. For this purpose, switch the instrument to the 2V AC
measuring range. Plug a shorting jumper into the V/Ohm input sockets.
Using the auxiliary digital multimeter (6 1/2 digits), measure the
voltage Ua rms with respect to +/-15V analog ground at the output of the
true rms converter (pin 10, U 5). Adjust the trimmer R 23 (to make Ua
rms zero (tolerance +/-50 microvolts). The frequency alignment of the HM
8112 can then be carried out.
Service Manual HM 8112 - Hameg GmbH - Subjekt to change without notice
IMPORTANT
For checking the frequency response, it is essential to close and effi-
ciently
access to the trimmers is ideal.
Execution
Frequency alignment
а.
2.
ground the cover of the case. А special cover with holes for
0.2 Vac: No alignment required
2 Vac: No alignment required
20 Vac: 1. INPUT: 10V/90Hz; note the display reading
2. INPUT: 10V/10kHz: adjust the trimmer capacitor
C 5 (20Vac) to make the display reading the
same as for 10V/90Hz.
NOTE : The 10V/90Hz display reading changes. Thus repeat the
| steps 1. and 2. alternately until both are correct.
200 Vac: 1. INPUT: 100V/90Hz; note the display reading
2. INPUT: 100V/10kHz; adjust the trimmer capacitor
C 3 (200Vac) to make the display reading the
same as for 100V/S0Hz.
The 100V/90Hz reading should not change.
1000 Vac: 1. INPUT: 100V/90Hz; note the display reading
2. INPUT: 100V/1kHz; adjust the trimmer capacitor C7
(1000Vac) to make the display reading as
closely as possible equal to the display reading
for 90 Hz (deviations up to 2000 digits are
tolerated).
NOTE: The alignment of the 200 Vac range may change,
thus repeat alternately until both are correct.
Service Manual HM 8112 - Hameg GmbH - Subjekt to change without notice
FAULT TRACING
Some faults and their possible causes are described below. First an
explanation of the terms "INITIALIZATION" and "RESET":
1. INITIALIZATION in setting "MEAS"
Set the MEAS-CAL switch to "MEAS": switch the HM 8112 off, then SWITCH
IT ON again. The instrument thereupon runs through a sequence of inter-
nal check routines: CONTROL 1, 2, 3. Thereafter, the instrument 1s set
to the 1000 Vdc range and the display reads 0000.00.
2. INITIALIZATION in setting "CAL"
WARNING: All calibration data are erased.
Switch the HM 8112 off, set the MEAS-CAL switch to "CAL" and then switch
the instrument on again. The instrument thereupon runs through a
sequence of internal check routines: CONTROL 1, 2, 3. The display
flashes alternatingly: "CAL" and (1000 Vdc) 0019.XX or 0025.XX.
These digits (=CONVERTER OFFSET) appear in all functions and measuring
ranges.
RESET: The HM 8112 carries out an INITIALIZATION.
FAULT-SYMPTOMS POSSIBLE CAUSES
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1. No INITIALIZATION, not even in 1. RAM (U 7)
in "CAL" setting 2. Socket Jb
3. U 9
2. No clock signal 1. Opto-coupler U 13
| 2. Plug connector
3. U 9
4. Crystal Yl
3. No ERG signal (Result) 1. Opto-coupler U 14
2. Same as for Fault 2.
4. No UME signal (end of sub- 1. Opto-coupler U 15
measurement) 2. Same as for Fault 2.
5. Incorrect INITIALIZATION in 1. U 12
setting "CAL" 2. U 10
3. SH 10
6. RESET on HV INPUT The microprocessor board is not
screwed down firmly (C 18 with
respect to case GROUND)
Plug connector
Control IC U 16-
Driver IC U 17, 18
7. IEEE 488 function
Lo D +—
U 12
U 10
U 9
Relays
8. Fault in RANGE SELECTION
> WN HH
Service Manual HM 8112 - Hameg GmbH - Subjekt to change without notice
9. "NULL" impossible + Uy
10. No current measurement 1. 3.154 fuse
2. 100mA fuse
11. Vac offset can not be corrected U 5
12. SCANNER FUNCTION 1. U 1
2. U 3
3. Plug connector
4. RC-combinations around U 3
5. U 9
6. U 10
7. U 12
8. 05
13. Display reading runs up until
"ERR 1" appears U 9
"ERR 1" in "KOhm" 1. 01
2. 02
3. Ul
4. U4 7V reference
"ERR 1" Uvv lies above the
RANGE LIMIT (greater than 2V); there are
many possible causes for this.
Uvv o.k.; then check U 6, U 7, C 18, Q 3
"ERR 1" o.k. in "kOhm" with open V/Ohm input;
("ERR 4") o.k. in "Vde", "Vac" 0.1V, 1V with
open V/Ohm input
"ERR 8" 1. Data loss |
2. Lithium battery low; nominal
terminal voltage at least 3.2 V
3. See explanations below.
Explanations for "ERR 8":
Unusually severe electrical disturbance in the immediate environment of
the HM 8112 (electric fields, induction currents, etc.) may affect the
data held in the battery backed-up RAM (U 7), so that some or even all
the data (calibration factors, offset correction values, IEEE address,
integration time and channel preselection) may be changed or lost. The
error display "ERR 8" then indicates this state of the instrument. The
HM 8112 must now be recalibrated and/or the lost data must be reloaded.
The lost data can be reloaded into the RAM as follows:
Switch-off the HM 8112. Move the CAL-MEAS switch to "CAL". Then switch
on the HM 8112 again. Thereby the data which have been stored into the
EPROM in the factory are reloaded into the RAM. The offset correction
values for the zero points in all ranges and for all functions must be
redetermined. Thereafter return the CAL-MEAS switch to the MEAS-setting.
Service Manual HM 8112 - Hameg GmbH - Subjekt to change without notice
HM8112
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HIRAM EL=
Oscilloscopes
Multimeters
Counter Timers
Power Supplies
Calibrators
Signal
Generators
Check Point
Testers
Printed in West Germany
West Germany
HAMEG GmbH
Kelsterbacher Str. 15-19
6000 FRANKFURT am Main 71
Tel. (069) 67805-0 - Telex 413866
Telefax (069) 6780513
France
HAMEG S.a.r.l.
5-9, av. de la République
94800-VILLEJUIF
Tél. (1) 46778151 ; Télex 270705
Telefax (1) 47263544
Spain
HAMEG S.A.
Villarroel 172-174
08036 BARCELONA
Teléf. (93) 2301597 / 2301100
Telex 99816 - Telefax (93) 3212201
Great Britain
HAMEG LTD
74-78 Collingdon Street
LUTON, Bedfordshire LU1 1RX
Tel. (0582) 41 31 74 - Telex 825484
Telefax (0582) 456416
United States of America
HAMEG, Inc.
88-90 Harbor Road
PORT WASHINGTON, NY 11050
Phone (516) 883-3837
Telex (023) 497-4606
Telefax (516) 883-3894
HAMEG, Inc.
Hancock Business Park
4790 Wesley Drive
ANAHEIM, CA 92807
Phone (714) 970-9575
Telefax (714) 970-0328
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