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                                    The PM2535 is a digital, automatic multimeter controlled by
a microcomputer.
The instrument has the following capabilities:
- Standard multimeter functions
- Help functions
- Input of figures
- Extended capabilities via the IEC-625/IEEE-488 interface
The standard multimeter functions (white text) are:
- Direct voltages 
- Alternating voltages (V~) true RMS, ac coupled.
- Direct currents (A—)
- Alternating currents (A~) true RMS, ac coupled.
- Resistance, in two-wire (Ω-2 W) and four-wire (Ώ-4 W)
configuration
- Temperature °C
Ranges can be selected manually, automatically or remote.
Beside the standard functions the user can alter the speed
to increase the number of measurements per second, or to
obtain a higher resolution.
The filter function switches in a frequency filter in the
function and A~; in all other functions (except °C) it acts
as a digital filter.
Offset in the lowest dc range can be compensated by using
the NULL function.
Measurements can be started with an internal, manual or
external facility. External starting is possible via the
trigger input, or via the IEC/IEEE-bus interface.
The help functions (green text) are:
- Mathematical functions, processing the measuring data such as:
AX + B
Δ%
dBm
ZERO
- Aquisition/presentation of the measuring data such as:
DELAY, LIMITS, BURST.
RD.BUF, MIN/MAX, LIMITS, DIGITS
- Function programming such as:
To store and call combinations of instrument settings. PROG,
SEQU (SYSTEM 21)
- General
Beeper on/off, CHECK, ENTER, CLR (CLEAR)

THIS SERVICE MANUAL REPLACES:
the first edition Service Manual 4822 872 35302 the second
edition Service Manual 4822 872 35312
-Service note SME 126, 4822 872 38308
-Service note SME 130, 4822 872 38313
-Service note SME 132, 4822 872 38315

CONTENTS III
1. SAFETY INSTRUCTIONS 1-1
2. CHARACTERISTICS AND PERFORMANCE TEST 2-1
3. CIRCUIT DESCRIPTION 3-1
3.1 Explanation of the block diagram................ 3-1
3.2 Detailed description ............................ 3-6
3.3 Analog section ................................. 3-6
3.3.1 V dc measurement ................................ 3-7
3.3.2 V ac measurement .............................. 3-9
3.3.3 DC/AC current measurements ...................... 3-11
3.3.4 Resistance measurement .......................... 3-11
3.3.5 Temperature measurement ......................... 3-12
3.3.6 Multiplexer .................................... 3-12
3.3.7 Control of analog section ....................... 3-12
3.3.8 Guard circuit .................................. 3-12
3.3.9 Analog to Digital conversion .................... 3-13
3.3.9.1 General ........................................ 3-13
3.3.9.2 ADC principle .................................. 3-13
3.3.9.3 Automatic zero ................................. 3-14
3.3.9.4 DAC ............................................ 3-14
3.3.10 Reference voltages .............................. 3-14
3.3.11 Inguard-outguard connection ..................... 3-15
3.4 Digital section ................................. 3-15
3.4.1 Software description ............................ 3-15
3.4.2 RAM/ROM ........................................ 3-16
3.4.3 I2C bus ........................................ 3-16
3.5 IEEE/IEC interface .............................. 3-17
3.5.1 Receiving ...................................... 3-17
3.5.2 Transmitting ................................... 3-17
3.6 Display/keyboard ................................ 3-18
3.7 Data of components .............................. 3-18
3.7.1 8031 AH microcomputer ........................... 3-18
3.7.2 MAF 8441 ....................................... 3-22
3.7.3 DAC 08 E ....................................... 3-24
3.7.4 TL 7705A ....................................... 3-25
3.7.5 OM 503 ......................................... 3-26
3.7.6 SA 1045 ........................................ 3-27
3.7.7 OQ 0300......................................... 3-28
3.7.8 OQ 0301 ........................................ 3-29
3.7.9 SA 1300 ........................................ 3-31
3.7.10 PCF 8574 ....................................... 3-31
3.7.11 OQ 0068 ........................................ 3-33
3.7.12 LTC 1052 ....................................... 3-34
4. DISMANTLING THE INSTRUMENT 4-1
4.1 Removing the cover .............................. 4-1
4.2 Removing the top screening ......................4-2
4.3 Removing the bottom screening ...................4-2
4.4 Removing the front assembly ..................... 4-2
5. CHECKING AND ADJUSTING 5-1
5.1 General information ............................. 5-1
5.2 Calibration adjustments.......................... 5-1
5.3 Adjusting the PM2534/PM2535 using a controller.... 5-4
6. CORRECTIVE MAINTENANCE 6-1
6.1 Special parts .................................. 6-1
6.2 Replacing parts ................................ 6-2
6.2.1 Parts on the PCB ................................6-2
6.2.2 LX-display, window and interconnection rubber .... 6-2
6.2.3 Input unit ..................................... 6-3
6.2.4 Interchanging input unit ........................ 6-4
6.2.5 Fuses .......................................... 6-4
6.3 Trouble shooting ................................ 6-5
7. SAFETY INSPECTION AND TESTS AFTER REPAIR AND MAINTENANCE
IN THE PRIMARY CIRCUIT 7-1
7.1 General directives ...............................7-1
7.2 Safety components ................................7-1
7.3 Checking the protective earth connection ..........7-1
7.4 Adaption to the local mains ......................7-2
7.5 Adaption to the local mains frequency .............7-2
8. PARTS LIST 8-1
8.1 Mechanical parts ................................ 8-1
8.2 Electrical parts ................................ 8-3
9. CIRCUIT DIAGRAMS AND PRINTED CIRCUIT BOARDS LAY-OUTS 9-1
10. GLOSSARY OF TERMS 10-1
11. MODIFICATIONS
11.1 Hardware modifications .......................... 11-1
11.2 Software modifications .......................... 11-7

1. OPERATOR SAFETY 1-1E
1.1 General
information............................................................................
......................................1-1E
1.2 Safety
precautions................................................
............. ................. . 1-1E
1.3 Caution and warning
statements..............................
......................................... - 1-1E
1.4 Symbols.................
............................................................................................................1-1E
1.5 Impaired safety protection........................ ... 1-1E
2. GENERAL INFORMATION 2-1E
2.1
Introduction......................................................................................................................................2-1E
2.2
Characteristics.................................................................
...................................................2-2E
2.2.1 Safety characteristics...............
.................................
..........................................2-2E
2.2.2 Performance characteristics..........................
................................................................2-2E
2.2.3
Vdc......................................................................................................................................................2-3E
2.2.4
Vac......................................................................................................................................................2-5
E
2.2.5 Resistance .............
............................................................................................2-6E
2.2.6 Idc
......................................................................................................................................................2-8E
2.2.7
lac..........................................................................
................................................................2-9
E
2.2.8 Temperature ........................ ...........
............. ....................................2-11E
2.2.9 Converter characteristics
............................................................. .................................2-11E
2.2.10 Time function........................ ...
...........................2-12E
2.2.11 Input terminal arrangement. ...
..............................................................2-12E
2.3 Operational data.................
........................................... ...
.........................2-13E
2.3.1 Display..................................... ...
.................................................2-13E
2.3.2 IEC/IEEE
interface...................................................................
..........................................2-14E
2.3.3 System 21
interface..........................................................................................................................2-14E
2.3.4 External
control...............................................................
........................................................2-14E
2.4 Environmental conditions ... ...
........................ ... 2-14E
2.4.1 Climatic conditions
...........................................................................................................................2-14E
2.4.2 Mechanical
conditions.....................................................................................................................2-15E
2.4.3 Line supply
conditions.....................................................................................................................2-15E
2.4.4 Power consumption. ...........
................................... .. 2-15E
2.4.5
Accessories.............................................................................................
....... . 2-15E
3. INSTALLATION INSTRUCTIONS 3-1E
3.1 Initial inspection. .................
...................................................................................................3-1E
3.2 Safety
instructions............................................................................................................................3-1E
3.2.1 Earthing (grounding)............................ . 3-1E
3.2.2 Mains voltage setting and
fuses................................
.......................................................3-1E
3.3 Operating position of the
instrument..................................................
................. . 3-2E
3.4 19-Inch
rack-mounting......................................................................................................................3-2E
4. OPERATING INSTRUCTIONS 4-1E
4.1 General information........................
...................................................................................4-1E
4.2 Switching-on
..............................................................................................................................
. 4-1E
4.3 Display indications...............
........................................................................
. 4-3E
4.4 Keyboard.........................................
..........................................................................4-5E
4.4.1 Multimeter functions, direct action .
.......................... ........... ...........4-5E
4.4.2 Help
functions...................................................................................................................................4-6E
4.4.2.1 Function programming
..................................................................................4-6E
4.4 2.2 General .....................................
................................
..............................................4-6E
4.4.2.3 Mathematic
functions......................................................................................................................4-6E
4.4.2.4 Aquisition/presentation of measuring data . . 4-6E
4.4.2.5 Input of
figures...................................................................................................................................4-7E
4.4.3 Inputs............. ........... .................
.............................................4-7E
4.4.4 Guard
Usage.....................................................................................................................................4-7E
4.5 Rear panel Controls . ..........................
................................. .................4-8E
4.6 Detailed multimeter functions explanation .
..........................................................................4-9E
4.6.1 Function Selection........
........................................................4-9E
4.6.2
Ranging..........................................................................
.......................4-9E
4.6.3
Trigger................................................................................................................................................4-10E
4.6.4 Speed .
.....................................................................
..........4-11E
4.6.5 Filter
..............................................................................................................................4-12E
4.6.6. Null......................... . 4-12E
4.6.7 Selfdiagnostics................... ...................
.......................................4-13E
4.6.8
Reset..................................................................................................................................................4-13E
4.6.9
Calibration..........................................................................................................................................4-13E
4.7 Measuring functions
explanation..............................................
........ ...........4-14E
4.7.1 Direct voltage
measurements..............................
...........................................................4-14E
4.7.2 Alternating voltage measurements . . .
................... ........................4-15E
4.7.3 Resistance two-wire measurements ... ...........
..........................................................4-16E
4.7.4 Resistance four-wire measurements. . . . . 4-17E
4.7.5 Direct current
measurements..........................................................................................................4-18E
4.7.6 Alternating current
measurements..................................................................................................4-19E
4.7.7 Temperature
measurements.......................................
................................. .... 4-20E
4.7.8 Clipping-Crest-factor indication
.............................................4-20E
4.8 Help functions Explanation...............
.......................... ..............................4-21E
4.8.1 Mathematical functions explanations . 4-21E
4.8.1.1 AX + B scaled
measurements..........................................................................................................4-21E
4.8.1.2
dBm......................................................................................................
.....................................4-23E
X-C
4.8.1.3 Δ% ------ x 100%
......................................................................................................4-24E
c
4.8.1.4
Zero....................................................................................................................................................4-25E
4.8.2 Aquisition/presentation of measuring data.
..............................4-26E
4.8.2.1
Delay..................................................................................................................................................4-26E
4.8.2.2 Limits..............................
.................................................................................................................4-27E
4.8.23
Burst......................................................................................................................................................4-29E
4.8.2 4 RD.BUF. (read buffer)
.........................................................................4-31E
4.8.25
MIN/MAX.................................................................
... ... 4-35E
4.8.26
Digits.......................................................................................
....................................4-36E
4.8.3 Function programming
...............................................................
.......................................4-37E
4.8.3.1 PROG
function...................................................................................................................................4-37E
4.8.3.2
Sequence............................................................................................................................................4-38E
4.9 General
....................................................... . 4-42E
4.9.1 Bleeper· . . 4-42E
4.9.2 OLR
(Clear).............................................................................................................................................4-43E
4 9.3 Check........................... 4-44E
4.9.4 SHIFT and ENTER . . . 4-44E
4.9.5 Input of figures.. . 4-44E
5. OPERATING INSTRUCTIONS FOR REMOTE OPERATION VIA
IEC-625/IEEE-488 INTERFACE 5-1E
5.1 General 5-1E
5.2 Specifications..............................
....................................... ............... 5-1E
5.2.1 Functional specification... 5-1E
5.2.2 Code specification . . 5-1E
5.2.3 Connector pinning .... ........... 5-1E
5.2.4 Timing specification... 5-2E
5.3 Programming the PM2535 . 5-3E
5.3.1 General information. . . 5-3E
5.4 Interface programming . 5-3E
5.4.1 Explanation................. 5-3E
5.4.2 Remote/local selection ........... 5-4E
5.4.3 Talk only selection. 5-4E
5.4.4 Address selection .... ............. 5-5E
5.4.5 Interface program data . 5-5E
5.4.6 Sending program data. . 5-5E 5 4.7 Separators . . 5-7E
5.4.8 Identity............... 5-7E
5.4.9 Interface test . ........... . 5-7E
5.5 Device programming . . 5-7E
5.5.1 Function selection . 5-8E
5.5.2 Range selection.......................... 5-8E
5.5.3 Measuring Speed/Resolution 5-9E
5.5.4 Filter................. 5-9E
5.5.5 Trigger modes........... . 5-10E
5.5.6 Internal settling time . . 5-1OE
5.5.7 Start command .. 5-10E
5.5.8 Display mode. 5-10E
5.5.9 Output mode 5-11E
5.5.10
Null.....................................................................................................................................................
5-11E
5.6 Help functions (Device programming) . 5-12E
5.6.1 Mathematic functions ... 5-12E
5.6.1.1 AX + B ... 5-12E
5.6.1.2 dBm . 5-13E
5.6.1.3 Δ% . 5-13E
5.6.1.4
Zero.................................................................
. 5-14E
5.6.2 Aquisition/presentation of measuring data . 5-14E
5.6.2.1 Delay 5-14E
5.6.2.2 Limits . . . 5-15E
5.62.3 BURST.............. . 5-15E
5.6.2 4 RD.BUF (Read Buffer) 5-16E
5.62.5
MIN/MAX...............................................................................................................................................■
5-17E
5.6.26 DIGITS........................... 5-18E
5.6.3 Function programming 5-18E
5.6.3.1 PROG function............. 5-18E
5.6.3.2 Sequence ■ 5-18E 5 6.3.3 Bleeper . 5-19E
5.7 System 21 mode 5-19E
5.8 Survey of commands 5-20E
5.9 Calibration via the controller 5-23E
5.10 Selfdiagnostics via the controller 5-23E
5.11 Output data . 5-23E
5.11.1 Measuring data 5-23E
5.11.2 Dump................. 5-25E
5.11.3 Output of settings 5-26E
5.11.4 Device status data . 5-28E
5.11.5 Identity........ 5-29E
5.11.6 Interface test 5-29E
5.12 Reasons for service request . 5-29E
5.13 SYSTEM 21 master function.. . 5-31E
5.13.1 General
............................................................. 5-31E
5.13.2 Contact assignment of System 21 connector...........
5-32E
5.13.3 Addressing a message 5-32E
5.13.4 Commands. . 5-32E
6. GLOSSARIES 6-1E
6.1 Glossary of terms ........... ........... . 6-1E
6.2 Short survey of program commands
...........................................................................................
6-3E
APPENDIX A 1S0-7 BIT CODING TABLE A-1
APPENDIX B PROGRAM EXAMPLES

1. INTRODUCTION 1-1E
2. SPECIFICATION OF THE RS232-C/V24 INTERFACE 2-1E
2.1
SPECIFICATION...........................................................................................................................
2-1E
2.2 SWITCH
SETTINGS......................................................................................................................
2-1E
2.2.1 Baudrate
.......................................................................................................................................
2-1E
2.2.2 Character length, parity,
handshake............................................................................................
2-1E
2.2.3 Multidrop
mode.............................................................................................................................
2-2E
2.3 CONNECTOR
PINNING................................................................................................................
2-4E
2.4 CABLE FOR CONNECTION BETWEEN THE P3200/IBM AT AND THE
PM9190 .................... 2-4E
2.5 CABLE FOR CONNECTION BETWEEN THE PM3102/IBM XT AND THE
PM9190.................. 2-4E
3. PROGRAMMING THE PM2534 AND PM2535 3-1E
3.1. INTERFACE
MESSAGES...............................................................................................................
3-1E
3.1.1 Remote/local
functions...................................................................................................................
3-1E
3.1.2 Device
clear...................................................................................................................................
3-1E
3.2 INTERFACE
PROGRAMMING......................................................................................................
3-1E
3.2.1
Separators.....................................................................................................................................
3-2E
3.2.2
Identity...........................................................................................................................................
3-2E
3.2.3 Interface
test.................................................................................................................................
3-2E
3.3 DEVICE
PROGRAMMING..............................................................................................................
3-2E
3.4 OUTPUT
DATA.............................................................................................................................
3-2E
3.4.1 General
rules.................................................................................................................................
3-2E
3.4.2 Measuring
data.............................................................................................................................
3-3E
3.4.3 Device status
data..........................................................................................................................
3-3E