Keithley 196 Service manual

Model 196

System DMM

instruction Manual

Contains Operating and Servicing Information

WARRANTY

Keithley Instruments, Inc. warrants this product to be free from defects in material and tiorkmanship for a period of 1 year from date of shipment.

Keithley Instruments, Inc. warrants the following items for90 days from the date of shipment: probes, cables, rechargeable batteries,

diskettes, and documentation.

During the warranty period, we will, at OUT option, either repair or replace any product that proves to be defective.~~ :

To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in Ct&e.land, Ohio. YOU will be given Prompt assistance and return instruciions. Send the product, transport&~ prepaid, to the indicated service facility. Repairs will be made and the product returned, transportation prepaid. Repaired or replaced products are warranted for the balance of the original warranty period, or at least PO days.

LIMITATION OF WARRANTY

This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or misuse of any product or part. This warranty also does not apply to fuses,~software, non-rechargeable batteries, damage from battery leakage,~or problems arising~55Zi-i ncmii~l wear or failure to follow instructions.

THIS WARRANTY IS IN LIEU OF ALL OTtiERWARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES PRO\IIDED HEREIN ARE BUYER’S SOLE AND EXCLUSIVE REMEDIES.

NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT, JNDIRECT, SPECIAL, INCIDENTALOR CONsE:QUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS JNSTRIJM.ENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED To: COSTS OFT REMOVAL

AND INSTALLATION, Lossm SUSTAINED As THE RESULT OF IN3URY TO ANY PERSON, OR DAMAGETO PROPERTY.

Model 196~ System DMM

Instruction Manual

01986, Keithley Instruments, Inc.

Test Instrumentation Group

Cleveland, Ohio, U.S.A.

Fourth PrintingJanuary 1992

Document Number: 196-901-01 Rev. 0

Safety Precautions

The following safety precautions should be observed befoE using this product and any associated inshvmentation. Although some instruments and accessories would normally be used with non-hazardousvoltages, therearesituatio~iis where hazardous conditions may be present

This product is intended for use by qualiied personnel who iecognize shock hazards and are familiar with the safety precautions required to avoid possible injury. Read the operating information carefully before using the product.

Exercise extreme caution when a shock hazard is present. Lethal voittige may be present on cable connector jacks or test f?xtures. The American National Standards Instih~te (ANSI) states that a shock hazard exists when voltage levels greater

than 30V RMS, 42.4V peak, or 60VDC are present. A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring.

Before operating an inskutient, make sure the line cord is connected to a properly grounded power receptacle. Inspect the connecting cables, test leads, and jumpers for possible wear, cracks, or breaks before each use.

For maximum safety, do not touch the product, test cables, or any other instruments while power is applied to the circuit under test. ALWAYS remove power from the entire test systern and discharge any capacitors before: connecting or disconnecting cables or jumpers, installing or removing switching cards, or making internal changes, such as installing or removing jumpers.

Do not touch any object that could provide a current path to the common side of the circuit under test or power lie (earth) ground. Always make measurements with dry hands while standing on a ~JY, insulated surface capable of withstanding the voltage being measured.

Do not exceed the maximum signal levels of the instruments and accessories, as defined in the specifications and operating inform&ion, and a~ shown on the instrument or test fixture rear panel, or switchiig card.

Do not connect switching cards directly to unlimited power circuits. They are intended to be used with impedance limited sources. NEVER cbnnect switching cards directly to AC tin. When connecting sources to switching cards, install $~~tive devices to lit fault current and voltage to the card.

When fuses are used in a product, replace with same type and rating for continued protection against fire hazard.

Chassis connections must only be used as shield connections for measuring circuits, NOT as safety earth ground connections.

If you are using a test fxtwe, keep the lid closed while power is applied to the device under test. Safe operation requires the u.s$of a lid interlock.

Ifa @saew ispresenton~hetest tixhm?,connectit tbsafety earth ground using #18 AWG or larger wire.

The $ symbol on an instrument or accessory indicates that 1oOOV or more may be present on the terminals. Refer to the product manual for detailed operahlng information.

Instrumentation and accessories should not be connected to humans.

Maintenance should be performed by qualified service personnel. Before perfo&ng any maintenance, disconnect the line cord~and all test cables.

DC~ VOLTS 6% Digits,

SPECIFICATIONS

ANALOG SETTLING TIME: <lm.s (<2ms on 300mV range), to 0.01%

of step change.

CMRR: >lZOdB at dc, MHz or 6OHz (iO.O5%) with lkQ in either lead.

NMRR: >M)dB at50Hz or60Hz (iO.0546). ~~

RESPONSE: Tiue root mean square, ac coupled. CREST FACTOR (ratio of peak to rms)z Up to 3:l allowable. NONSINUSOIDAL INPUTS: For fundamental frequencies < -, mest

factor ~3, add 0.25% of reading to specified accuracy for 3oomV and 3V ranges; add 0.6% of reading to specified accuracy for 30V and 3fXlV

ranges. INPUT IMPEDANCE: lMlI shunted bv <12OoF. 3dBBANDWIDTHz 3WkHzfypical. ’ ’ MAXIMUM ALLOWABLE INPUT: 3oOV -, 425” peak, 10’ VHz,

whichever is less. SETTLING TIME: 1 second to within 0.1% of change in reading.

LINEARI’IY Linearity is defined as the timurn deviation from a straight

line between the readings at zero and full range: 1Oppm of range for

~3V-3ooV ranges; 15ppm of range for 3OOmV range; at 23OC il°C.

MAXIMUM ALLOWABLE INPUT: 300V rms. 425” peak, whichever is

less.

TBMF’ERATURE COEFFICI@‘JT (0=18”C & 28Y?,*C):

< i(O.l x app!icable accuracy specification)K below 2OkHz,

f(0.2.x) for 2okHz to 1ook?iz.

CMRR: >6OdB at 5OHz or 6OHz (*0.05%) with IkR in either lead.

dB (Ref. = 1”):

INPUT *OHa-~0gz

.4CC”RAcY *a

1 Year, IP-WC

?OW-?c!

-. P??LUnoN

WNETGURATION: Automatic 2- or&,ire. Offset compensationavai!ab~e OBN CIRCUIT VOLTAGE: 5.5V maxinwm.

on 3wiXOkO ranges, requires proper zeroing. Allowable compensation of ilOmV on 3OilQ range and ilWmV on 3ktl and 3OkO ranges.

MAX, ALLOWABLE INPIJZ 3wV rms, 425V peak, whichever is less.

JJNEARIlY Linetity is defined as the madmum deviation from a &might

line between the readings at zero and full range: 20ppm of range for SCO@3OkO ranges, at 23°C iYC.

3mA

3iE

3 A

‘4wigit count error is 20. 3K-digit CO”“t error is 5.

MAXIMUMALLOWABLHINPUT: 3A, 250”. OVERLOAD PROTECTION: 3A fuse (25OV), accessible from reii~ panel. TEMPERATURE COEFFICIENT (O”-18’C & 2S”-500C):

c iCO.1 x applicable accumw svecification)PC.

1 For Sinewave inputs >x.m EOuntS. For 4Vdigit accuracy, divide cou*t error by

10. .%3lidigit accuracy, count errOI b 5. Jn 3vl- and 4K.digit modes, specificati‘J”d apply for stnew.we inputs ,200Hz.

RESPONSE: True mot mean square, ac coupled. CREST FACTOR (ratio of peak to rms): Up to 3:l allowable at % full scale. NONSINUSOIDAL INPUTS: Spe&d accwacy for fundamental fquen-

ctes <lkJ&, CI& factor <3. SEmING TIME: 1 second to within 0.1% of change in reading. MAXIMUM ALLOWABLE INPUT: 3A, 250V. OVERLOAD PROTECTION: 3A fuse (UOV) accessibl&fiom rear panel.

TEMPERATURE COEFFICIENT (O’-18’C & 28%d”Qi~ ~’

< f(O.l x applicable accuracy specification)i°C.

dB (Ref. = ImA): ‘4CC”RAcY *a

INPUT

-34 to +69 dB (ZOJ4.4 to 3.4) 0.2 0.01 dB

-54 to -34 dB

@!A to 20PA)

10 n.4 0.05 + 10

1ooP.A

10 K.4 0.09 + 10

1 Year, 1S%B’C

2oH51okHz

0.05 0.05 + +~ 10 10

0.9 0.01 dB

* v

~~~

RE8OLuTION ~~~~

tiAXIMUM READING RAT&

DCV, DCA, ACV, ACA READINGS/SECOND

conttn”ovs into Extemal Rigger into Triggered via

Internal Buffer I”temd Buffer

IEEE488 Bus

IEEE-488 BUS IMPLEMENTATION

MULTILINE COMMANDS: DCL, LLO, SDC, GET, GTL; UNT, UNL,

.~- SPE, SPD.

UNILINE COMMANDS: IFC, REN,~EOI, SKQ, ATN.

INTERFACE FUNCTIONS: SHl. AHl, T6, TBO, L4, LEO, SRl, RLl, ?PO,

DCI. DTl, CO, El.

PROGRAMMABLE PARAMETERS: Range, Function, zero, Integration

Period, Filter. EOI. Trigger, Terminator, Delay, ?OO-Reading storage, Calibration. Display, Multiplex, Status, Service Request, Self Test, Output Format. TRANSLATOR.

GENERAL

RANGING: Manual or autoranging. MAXIMUM READING: 3029999 counts in 6%.digit mode. ZERO: Control subtract: on-scale value from subseqtient readings or allows

value to be prog&nmed.

CONNECTORS: Analog: Switch selectable front or rear, safety j&s.

Digital: TRIGGER input tid VOLTMETER COMPLETE &put on iear

panel, BNCs. WARMUP: 2 hours to rated accuracy. DISPLAY: 10, 0.5-in. alphanumeric LED digits with decimal point and

polarity. Function and IEEE-488 bus status also indicated.

ISOLATION: Input Lo to IEEE Lo orpower line ground: 5oOVpeak. 5~xlC+

max. VI+ product. >lO’D paralleled by 4OOpF.

DATA MEMORY: 1 to 500 locations, programmable. Measurement inter-

vals selectable from lms to 999999,&s or triggered.

BENCH READING RATE: 5 readings/second (2lsecond on 30M8 and

3COMtl ranges).

FILTER: Weighted average (exponential). Programmable weighting, 1 to

l/99.

OPERATING ENVIRONMENT: O”-500$ 0%.80% relative humidity up

to 35T; linearly derate 3% RH/“C, 35’C-5Ci’C (0%.60% RH up to 28OC

on 3oOMB range).

STORAGE ENVIRONMENT: -25” to +65OC. POWER: 105.125V or 210.UOV, rex panel switch selected, 5OHz or 6OHz,

30VA max. YO-1lOV and 18022OV versions available upon request.

DIMENSIONS, WEIGHT: l27mm high x 216mm wide x 359mm deep

(5 in. x 8% in. x 14% in.). Net weight 3.7kg (8 Ibs.).

ACCBSSORIES AVAILABLE:

Model lOlYA-1: 5%.in. Single Fixed Rack Mounting Kit Model lOlYA-2: 5’%-in. Dual Fixed Rack Mounting Kit Model 10195-1: 5’%-in. Single Slide Rack Mounting Kit Model 10195-2: 5X-b,. Dual Slide Rack Mounting Kit Model 1651: 5&Ampere Shunt Model 1681: Model 168s RFPmbe Model 1685: Model 1751: Model 1754: Model 5806: Model 7W7-I: Shielded IEEE-488 Cable, lm Model 7007-2: Shielded IEEE-488 Cable, 20, Model 7008.3: IEEE-488 Cable, 3 ft. (O.Ym) Model 7008-6: IEEE488 Cable, 6 ft. (1.8m)

Prices and specifications Subject to change without notice.

Clip-On Test Lead Set

Clamp-On Current Pmbe General Purpose Test Leads Universal Test Lead Kit Kelvin clip Leads

TABLE OF CONTENT!3

SECTION l-GENERAL INFORMATION

1.1

1.2

1.3

1.4

1.5~ :p7

1.8

1.9

1.10

INTRODUCTION. ...........................................................................

FEAI-URES ...... .;. ................

WARRANTY INFORMATION .................................................................

MANUAL ADDENDA ..........

SAFETY SYMBOLS AND TFRMS SPECIFICATIONS

INSPECTION ..............................................

USING THE MODEL 196 MANUAL

GE’JTMG STARED .............................

ACCESSORIES .................... .~: .~.~;~.~..~;~..~~.~;-;;~.‘;~.~. .~;~; ;:~.~.

............................................................................

;~:~.~ .... .;.e:.;. .. .;. .......................................

; ..............................................................

............................................................... l-l

SECTION 2-BASIC DMM OPERATIONS

2.1

2.2

2.2.1

2.2.2

2.2.3

2.2.4

2.3

23.1

2.3.2

2.33~

2.3.4

2.4

2.4.1

2.4.2

2.4.3

2.5

2.6

2.6.1

2.6.2

2.6.3

2.6.4

2.65

2.6;6

2.6.7

2.68

2.6.9

2.6.10

2.6.u.

2.7

27.1

2.7.2

2.7.3

2.%4

2.75

2.7.6

2.7.7

2.7.8

2.7.9

INTRODUCTION ...........................................................................

POWER UP PROCEDURES .........

Line rower ...................................................

Power-Up sequence. Factory Default Conditions

User Programmed Conditions .................................................................

FRONT PANEL FAMILIARIZATION

DisplayandIndicators

controls..

~1nputTermine.k

Calibration Enable Switch

REAR PANEL FAMILIARIZATION

Controls Connectors and Terminals

Fuses.. ERROR DISPLAY MESSAGES. ..~.;Z:..; BASIC MEASUREMENTS

WarmUpPeriod

Zero.........................~............~.~.......~

Filter

DCVolta eMeasurements..

.Low-Leve Measurement Coiisiderations

Resistan& Measurements ...................................................................

TRMS ACVoltageMeasurements Current Measurements (DC or TRMS~~AC)

dBMeasurements

:TRMS Considerations

~~dBApplications .......................

FRONT PANEL PROGRAMS

Program 0 (Menu) Program2(Resolution) Program4(MX+B)~.

Program5~/LO/Pass).....................;

Program 6 (Multiplexer, Auto/CAL)

Program30(Save)..................~.....~

Program 31 (IEEE Address).

Program 32 (Lie Frequency) .......................................................

Program 33 (Diagnostic).

........................................................................................

................................................................................... 2-5

.....

_. ....... .

.......................................................................................

............................................................................

......................................................................

.............................................................................

...................................................................

....................................................................

.............................................................................

.....................................................................

...........................................................................

.........................................................................

...................................................................... 2-15

........................................................................

....................................................................

........................................................................... 2-18

.....................................................................

_._.~ .............................. ..I..

.................................................................

....................................................... __

...

~.~~..~...=_

...........................................................

................................................................... 2-17

.......................................................................... ~2-21

l-1 ..

.~.-.~:.: l-l

l-1 l-l

l-2

....

l-2

2-l 2-1

2-l 2-l

2-2 2-2

2-2 2-4 2-4 2-5

2-5 Z-6

2-6

2-7

2-8 2-9 ~~~

2-11 2-12 2-13 2-13

2-17 2-18

2-18

2-20

2-22

. ....................................

.......................................................... l-2

.; .........................

.... : .... .;~;;

: .................................

.......................................................... 2-2

.....................

......................................... 2-7

.................

..................................................... 2-10

.... ;. ........... .I ...............................

................

.............................................. 2-19

..........................................................

.................................................. 2-20

~...~;. ... .

..: . ..*-.

..........

:.~

....................... .~.

..~~...._~. ..~..: .. .;. ....... 1-2

.~~.-.: . :~.-;~; : .~: ;~. ........ l-3

....................... 2-l

...... ........

.;...:~;.=;

:..~: .............. .

_. ........... 2-21

;~~;~;::~ 2-6.

........

2.7.10

2.7.11

2.%x?

27.13

2.7.14

2.7.15

2.7.16

2.7x7

2.8

2.8.1

2.8.2

2.9

2.9.1

2.9.2

2.9.3

Program 34 (MX+B Pammeters) ............................................

Program 35 (HI/LO Limits) ..............................

Program36(Calibration) ...................................................................

mgram 37 (Reset) ..................

Programn ................................................................................

Program ZERO.. .............. .: .~;:.~.~.

Program FILTER

................. ..~.._~~

Program dB .................................

FRONT PANEL TRIGGERING .................................................................

One-ShotTrigge~ring.. ........ I.~...;..~

Triggering Readings Into Data Store.

EXTEEWAL TRIGGERING ...........................................

ExternalTrigger.. ..........................................................................

Voltmeter Complete ...................

~Trigering Example..

......................................................................

SECTION 3-IEEE-488 PROGRAMMING

., ..... _~. ... _ _ .... 2-22

., ...... ., ............................

., .... __. ................. -. ............................

.............................. .I. ..

. ... I~.~:.-. .......... .l~. 2-24

................................................... .._. 2-24

_,_,_ ............................................

.................. .;..... T . ..I. .............................

..................... ., .... __ .............................

., .. Z-25

_. ........................

.~._ .. .._. ............. ___~. ........................

._ .... 2-26

2-22 2-23 2-23 2-24

2-25 2-25 2-25

2-26 2-26

2-27

3.1

3.2

3.3

3.4

3.5 ~~~,

3.6

3.6.1

3.6.2

3.7

3.7.1

3.%2

3.8

3.8.1

3.8.2

3.8.3

3.8.4

3.8.5

3.8.6

3.8.7

3.8.8

3.9 ~

3.9.1

3.9.2

3.9.3~

3.9.4

3.9.5

3.9.6

3.9.7

3.9.8

3.9.9

3.9.10

3.9.11

3.9.32

3.9.13

3.9.14

3.9.15

3.9.16

3.9.17

3.9.18

INTRODUCTION.. ........................................................

A SHORTCUT TO IEEE-488 OPERATION BUS CONNECTIONS..

...................

........................................................ 3-l

. . ..~.~_~..~_ ............................................

INTERFACE FUNCTION CODES ..............................................................

PRJMARY ADDRESS SELECTION ......................................

CONTROLLER PRO%

RAMMING

........ _.

................................................... ~3-6

Controller Handler Softwae ..................................................................

BASIC Interface Programming Statements.

FRONT PANEL ASPECTS OF IEEE-488 OPERATION

FrontPanelErrorMessages.. ... ~;.;~.~..:...:~~ ...

IEEE-488 Status Indicators and LOCAL Key

GENERAL BUS COMMAND PROGRAMMIN

....................................................

..........................................

. ....................... ~..~..~...~;.~ ..............

....................................

G ................................................

REN (Remote Enable) .....................................................................

IFC (Tnterface Clear) .......................

__ _., .............................................

LLO (LocalLockout).......................................................~

GTL(GoToLocal). ........................................................................

DCL(Devi?e Clear) ........................................................................

~SDC t Selective De& Clear), ..................

1. _.~. .... -. ........... ._ ..........................

GET Group Execute Trigger) ..................................

Se&d Polling (SPE,SPD). .1.. ................

DEVICE-DEPENDENT COMMAND PRWWNG

Execute(x).

Fur&on (F) ................

Range(R). ......................

................................................. .._.

;

..............................................................

.._ ......................................................

.-;. ........ .: ....................................

............................. _..:. . ;,

zero(Z). .........................................................

Filter(P).......................~~............................................................3-

Rate (S).

........

......................................................................... 3-19

.;.

Trigger Mode Q ............................................................................

Reading Mode (B) .............................

Data Store Interval (Q) and Size (I) Value (V) and Calibration (C)

...............................................................

..........................................................

__ ..........................................

Default Conditions (L) ..............................................................

DataFormat(G). .... .

............. ;~:.

SRQ Mask (M) and Serial Poll Byte Format

...............

:I;.....; .:.

..................................................

EOI and Bus Hold-off Modes (K) ................................................................

Terminator(Y) .............. ~..~..~...~...l~.~ _.

........ _ ..........................................

status (u) ...................................................................................

Auto/Cal Multiplex (A). Delay (W)

.................................................................................... 331

....................................................................

...................

_ ........... _ ......... 3-6

__ __ ,3-7

.~I. .... ._ ....... 3-10

................ 3-11

-~.~. ........

t. ................. 3-n

....

........................... 3-17

..- .......................

.~: .... : 3-23

........................ 3-23

3-l

3-4 3-5

3-7 3-7

. 57

3-n

., . 3-ll

3Xl

3-12 3-12 3-13

3-13 3-14

3-17 3-18

3-18

3-20 3-20 3-20 3-22

3-24 3-26 :I!

3-29

3.9.19 ~Sem&~).

3.9.20

whit Button (H)

3.9.21 Display (D)

3.9.22

3.10

3.10.1

3.10.2

3.10.3

3.108

3.10.5

3.10.6

3.10.7

3.10.8

3.10.9

3.11

lntemalFilter(N) .........................................................................

TRANSLATOR SOFIWARE

Translator Format. WildCard($).

NEW and OLD ................. .;~,..~..~.~.

Combining Translator Words Combining Translator Words With Keithley IEEE-488 Commands Executing Translator Words and Keithley IEEE Commands

SAVE.. ..................... ~;~.~...~v ................................

~LIST

FORGET ............. :.I;

BUS DKC.4 TRANSMISSION TIMES

...................................................

...................................................................... ~...~.~.~__ .. 3-31

...............................................................................

..................................................

.............................................................

...............................................

..............

.........................

.......

_.~.

......

.._

.....................

..........................................................

SECTION 4-PERFORMANCE VERIFICATION

.._. . .._. . .- ................. 331

....

._.

.........

.......

_.,_~ ., . .,

. . c____. ... .._

.............. 335

....

...................... I. ... ,:~. ......................... 3-35~

..................

..............

................

.,_

..............................

....................................

.........................

1;:.

..........

.: ........................ 3-37

;.~.

;...;. 3-37

....

..~ ...................................

332 3-33

3-33

~3-34

3-35 3-36 3-36

3-37 3-37

...

4.1

4.2

4.3

4.4

4.5

4.5.1

4.5.2

4.5.3

4.5.4

4.5.5

INTRODUCTION ENVIRONMENTAL CONDITIONS

INITIAL CONDITIONS. ..... -

RECOMMENDEDTESTEQUIPMENT..

VERIFICAXION PROCEDURES.

DC Volts Verification ........................................ __ __ _._ ___ __

TRMS AC Volts Verification ......

Ohms Verification

DCCurrentVerification.. .... ;I;. ....... ;~ ................

TRMS AC Current Verification

..............................................................................

............................

_*_..._..__._ ................ ~.~_~. ................... ..--

.................................................................

..~.~......................~...I..~...........~.......~ ..........

.........

..~.._~:.

............

..............................

SECTION 5-PRINCIPLES OF OPERATION

5.1

5.2

5.3

5.3.1

5.3.2

5.3.3

5.3.4

5.4

5.5

5.6

5.61

5.6.2

5.7

INTRODUCTION OVERALL FUNCTIONAL DESCRIPTION ANALOG CIRCUITRY..

Input Signal Conditioning. Multiplexer

~+2.1V Reference Source ...........

Input Buffer Amplifier

A/D CONVERTER ...............

CONTROL CIRCUITRY DIGITAL CIRCUITRY

Microcomputer.

Display Circuitry ................

POWER SUPPLIES ....................

...........

.___ ~.~_~.~.~._.

............................................

....................

.................................................................................

.............

.........................................................

.._..~~.~_~_..................................~......_....._~ ...

.......................................................................

........................................................................................................................................................

..~._.......................~....................~ ...........

..................................

......

~.;;.

~...~.;~;.

...............

................................

.........

. ._

. .m .,._

.....

~_-_.

........................................................

...........................................................

. .......... _:~ ................. 5-l

.~.~.~~-. . .~; _.

................................

. .................... -. .... ~~~.~~:.~~. .................

..~.~...._..~ .............................................

......

...............

.........

......................

..... ;..~; ..:.

.~;~.~.-;.-;.......;. 4-4

......

................

...........

;

............

..-- ...

.~..;

...

....

41 4-1 41

41 42 4-2 4-2

4-3 4-5

5-l

5-4

5-7 .55

5-8 ;

5-9 5-9

SECTION B-MAINTENANCE

6.1

6.2

6.3

6.3.1

6.3.2

6.4

6.4.1

6.4.2

INTRODUCTION LINE VOITAGE SELECTION FUSE REPLACEMENT

Line Fuses CurrentFuse

CALIBRKION .....

RecommendedCalibrationEquipment Environmental Conditions.

..............................................................................

..................................................................................

....................... . ................

..................................................................

....................................................

..,

____.:

...

.......................

.........

.._....................~

..................

..~~.~...~..-*~~

. .._

__:.:

........

-;~

..................

I,;;...;..;;.~....;.~~~:

...................

.................................................................................

.~_.

6-l

....

6-l

2;;

iii

6.4.3

6.4.4

6.4.5

6.4.6

6.4.7

Warn-UpPeriod..

............

CALENABLE Switch.. .................

Front Panel Calibration ...............

IEEE-488Bus~CaIibration.. ..............

Calibration Sequence .... ! ........ ,.._._

DC V&s CaI’b 1 *alon.. t’ ............................

6.4.10

6.4.11

6.4.72

6.5

6.6

6.7

6.7.1

6.7.2

67.3

6.7.4

6.7.5

6.7.6

Resistance Calibration. .......... .I

TRMS~ACVtiltsCalibration.. ...................

DC Current Calibration .............

TRMS AC Currefit Calibration ................................................................

DISASSEMBLYINSi-RUCTIONS ..........

SPECIAL HANDLING OF STATIC-SENSI’?IVE DEVICES

TROUBLESHOOTING ............. .~I,~_.

Recommended Test Equipment .........

Power Up Self Test ..................

Program 33 - Self Diagnostic Program

Power Supplies ...................

Signal COnditioning Check .-. .. .:.:~~.

Digital and Display Circuitry Checks

SECTION 74iEPLACEABLE PAFITS

... I......,: ..:. .... ..:.~:..:...~ ..;

..I...

...........

........................................................

_.-.

.......................

......

.....

.......................................

.._. __.__ _...................,

.. :&.-. _. ...... ‘~-. ,_. ... .~_ .............................

.._ ..........................................

.... _, .......................................................

;~. .._ .. :.:~:.~ ... . ...............................

_. . __ ......... ... ._. .....................................

~...__._ . ,........I_ .......... ...............................

........

.................... .~:.

- ..l..: ..........

... ., .........................

-., .. ..I. ................ ._,_ _~. .,..__.

.-~- ._.~_._. .......... ._~.~.~.~.~.~.~. ., . ___.,

................ ._ ....... . _, ...............

.~.~_.__-. ..... .___“.,_. ............. _. .........................

....... .~-.:~. ....... _. ....... ._. ........................

........................................................

. ............. 6-3

6-3 6-3

.. ~.~6-4

__ . _ .. ,6,-4

6-5

6-6 6-7

., . 6-9

6-10 6-11

_I...~ ............ ~&lZ

: ......

., ... 6-12

...................... 6-14

. ., ...................... 6-14

__. ............. 6-14

6-15

_. .. 6-15

6-15

7.1 Z2 z3 %4

7.5

INTRODUCTION...~.~..~:~...;..;~..~.~..; .._.....I.... _......_......................_.._......_ _..

PARTS UST..............................................~....................~..~......-.... 7-1

ORDFRINGINFORMATION ..,................,. _.._ __........... ~-~ . . . . ~~.-- _..... ~-...1.~...~...-~~1~3~

FACTORY SERVICE . . . . . . . . ;..;.;....;...;;~-__.~.~-;; ._.. ~..__ . . . . . . . . . . . . . . I_ . . . . . . . . f . . . _ . . . . . . . . . . . .

SCHEMp;TIC DIAGRAMS ps;rrj: COMPG&T LOC&TIOti DRAWINGS . . . . : .~ .~. ; _ _ . . .~. __ . 7-l

APPENDIX A

ASCII CHARACTER CODES AND IEEE-488 MULTILINE INTERFACE COMMAND MESSAGES.. 1. A-1~

APPENDIX B

IBM PC/XT and MODEL 8573A PROGRAMMING . _ _. . . . . . _. . . _ _ _ _. _. . _ . _ __. . . k-1

APPENDIX C

CONTROLLER PROGRAMS. .‘, . .‘:. . ., . . . ::. .~. . __ . . . _ . .~. . . . _ . . . . . . , . . . . . :. . . _. .

APPENDIX D

IEEE-488 BUS OVERVIEW . . . . ._ . . . . . . . . . . . . . . . . _ . . . _ . , . _ . . _ __ _. . . _ . . . . . . _ . _ _.

7-1

;rl

C-l

D-l

LIST OF TABLES

SECTION 2-BASIC DMM OPERATION

2-l 2-2 23

Et 2-6 2-7 2-8

Factory Default Conditions ......

ErrorMessages ResistanceRanges..

Corresponding Voltage +ferenceJev$@for Impedance !7eference.

Comparison of Average and TRMS Meter Readings .............................................

FrontPanelPrograms..

Display Resolution ........................... .............

ExampleMX+BReadings.:.

.......... ..~.......;-.....................,......................;

............................

...... ~.:.

.~I. :. . : .;

.... . ..... :z.:. ... ~.:. ...

......

SECTION 3-IEEE-488 PROGRAMMING

3-l 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 3-ll 3-12

3-13 3-14 3-35 3-16

IEEE-488 Commands Used to Select Function and Range ........................................

~lEEE Contact Designation. ..............................

Model 196 Interface Function Codes ............................................

BASIC Statements Necessary to Send Bus Commands ...............................

FrontPanelIEEE488Messages.. General Bus Commands and Associated BASIC Statements ;~. FactoryDefaultConditiotis

Device-Dependent Command Summary ............................................

Range Co~andSummary...~..,,:. Rate Command Summary High Speed Data Store SRQ Command Parameters Bus Hold-off Ties

Translator Reserved Words and Chxacter ....................................

Translator Error Messages ... z

Trigger To Reading-Ready Times (DCV Funct&~n) ...............................................

........................................

..........................................................................

............................................

~~;I.~;.~~...;.;.~~; ....... ;;...~.J:.:..~..: ...

.......

..................................................

....................................................................

:~.

...

.................................................

. ............................................

.:~. ............... . .......

........

I...;

......................

:I............... l............

.....................

.z.:..~ .:. .................

.__

.... _ .............................

. ............. ~;;.;;~;;.

i ......................................

.................

:r:..~-..~.~ ~..~i: ..%.

._.

.......

. .... -..I~;~.~ 1..

..... ...........

... _ .. _ ................

.~.~.:.

......

.............. 2-6

.: ...... ;~. ..... 2-15

:.~. .......... 2-l7

... i...;;. 2-19~

...

........

1..

...........

..................

.~;.

...............

............ 3-12

..........

............

................

-.!L. 3-l$

......

3-22

__ 3-25

__ 3-26

3-33 3-34

3-37

2-2 2-12 2-16 2-18

3-3 35

3-6

3-7

3-8~

3-10 3-E 3-19

SECTION 4-PERFORMANCE VERIFICATION

4-2

22 45 46

RecommendedTest Equipment

Limits for DCV Volts Verification LimitsforTRMSACVoltsVerifibation..

Limits for Ohms Verification ... .:~. ;~.~.~. ....... ;...~

Limits for DC Current Verification

Limits for AC CurretifVerification

................................................................

........ .

.............................................................

.......................

SECTION 5-PRINCIPLES OF OPERATION

5-1

Input Buffer Amplifier (U35) Gain Co*gt&ation . . . . . . ‘. . . . . .‘; i . . . . ~ . . . . . _~. _ . _ . 5-7

.......

....................

.....................................

MY..;

....

t..

~.I;

......................

i-3

.:. ...................... 4-4

4-4

........

4-5

SECTION 6-MAINTENANCE

6-l 6-2 6-3 6-4 6-5 6-6

6-7 6-8

6-9 6-J.0 6-12 6-12 6-13 6-14

LineVoltage Selection LineFuseReplacement Current~Fuse Replacement Recommended Calibration Equipment

DCVoltsCalibration......................~.....-

ResistanceCalibration TRMS AC Volts Calibration. DC Current Calibration TRMS AC Currefit calibration Recommended Troubleshooting Equipment Model I.96 Troubleshooting Mode Power Stipply Checks. Digital Circuitry Checks. Display Circuitry Checks

............ ..L

.......................................................................

...................................

........................................................................

.................

............ .~.....................

.......................................

................................................

........................................................................

.....................

.........................................................

..........................................................

..............................................................

_. ....... __. ......................

..............................................

_, .. _._ ...............................................

.......................................

....................................................

., .. __ .............

_. ............................

.........................

_ ............ _

..... ., .. ., ., 6-18

6-l 6-2 6-2 6-2 6-5 6-6

6-7

6-10 6-11

6-14

6-15

6-18

6-19

SECTION 7-REPLACEABLE PAFKS

7-1 Display Board, Parts List.. . . . . . . . . . . , . . . . _ _ .-. .: . _ . _ :. . . . _:. . . . . _. . . . . . :. . . . .‘. . ._ _. 7-3

7-2

7-3 AnalogBoard,Parts List . . . . . . . . . . . . . . . . . . . . ..~.............................................. 719

7-4 Model196MiscellaneousParts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._........................

DigitalBoard,PartsList........................-~.............................................. 7-S

7-33

APPENDIX B

B-1 BASIC Statements Necessary to Send Btis

APPENDIX D

D-l lEEE488Bus Command So D-2 D-3 Typical Addressed Command Sequence.

;;

Hexadecimal and Decimal Command Codes Typical Device-Dependent Commiind Sequence

IBEE Co

mmaid

Group ................

............................................................

mmands........................................... B-1

...................................................

.......... D-7

.............................................

.. ;~. ...................

_ ..... ; ....................................

.; ..... . .. .;~..~ ............

., .......

D-3

D-7 D-7

., .... D-7

LIST OF ILLUSTRATIONS

SECTION 2-BASIC DMM OPERATION

2-l 2-2 2-3 2-4 2-5 2-6

2-7 2-8 2-9

2-10

Model196FrontPanel................................................~.......~.......~-

Model 196 Rear Panel

DCVoltageMeasurements ........................... ..~....~.....-...............~.-...~-

Two-Terminal Resistance Measurements Four-Terminal Resistance Measurements TRMSACVoltageMeasuremement Current Measurements. External Trigger Pulse Specifications Voltmeter Complete Pulse Specifications External Triggering Example

.............................................................

....................................................................................................................................

.........

SECTION 3-IEEE-466 PROGRAMMING

3-l 3-2

2 3-5 3-6 37 3-8 3-9 3-10

TypicalProgramFlo~ Chart..

IEEE-488 Connector .. ................ .......

IEEE-488Connections~. IEEE-488 Connector Location ...

Contact Assignments

~Generd Data Format

SRQMask and Serial Poll Byte Fo~at.........................................~.....-...-..-

UO Machine Status Word and Default V&es

Ul Error Status Word .... .... ........

Hit Button Command Numbers

...................................

.........................................................................

........................

..............................................................

.._ ........

.................................................

........................

..........................................................

.._..............._ .................

.....................................

~.y.:~I.T ._ ~.~--.~:~.~.~.

....................

~.:.~ ..;

.......................

......................................................

.............................................................................................................

................................

.~.- .. . _~_.~_ _,_

......................................

............................ .

.......

.....

..-

........

..*........~

...... _ .

_,__

........................

.................

.......

...

......

...

.~_.

-.:-~. :;4j

.....

;;.~:3: ...

2-3 2-5

2-10 2-11

2-p $E

2-26 i;g

3-5 3-23 3-24

i;;: 3-32

SECTION 4-PERFORMANCE VERIFICATION

42 43

E 4-6

Conmctions ‘for DC Volts Verification CoMectionsforTRMSACVoltsVeriCication~ Connections for Ohms Verification (300%#$! Range) Connections for Ohms Verification (3OOkn--3OOMQ Ranges) Connections for DC Current Verification Connections for TRMS AC Cur&t Verification ._.

..........................................................

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

SECTION &PRINCIPLES OF OPERATION

5-l 5-2 5-3

S-4 5-5 5-6

Overall Block Diagram. Input Configuration During 2 and 4Terminal Resistance Measurement. Resistance Measurement Simplified Circi&y

JFET Multiplexer

Multiplexer Phases A/D Converter Simplified Schematic

.......................................................................

.........................................................................................................

...........................................................

......

.....

....................................................

...................................................

_:.

.........

...............

......................................

..!.

.......

.........................

........................... 5-3

...............................................

...................

42 43 44 44

4-5

5-2 5-4

5-8

Vii

SECTION 6-MAINTENANCE

DC Volts Calibration Confii&on (300mV ani ,y @nges)

DC Volts Calibration Confi~atio~ (3OV-300V Ranges) ...........................................

Four-Wire Resistance Calibration Configuration (3000-3OkQ Ranges) Two-Wire Resistance Calibration Configuration (300kO3OOMQ Ranges). Flowchart of AC Volts Calibration Procedure TRMS AC Volts Calibration Configuration :.I

TRMS~ AC Volts Calibration Adjustments .......................................................

DC Current Calibration Configuration., .......................................................

ACCurrent CalibrationConfiguration

Analog Board Conne~ors~. ..........

Model196ExplodedViav

....................................................................

SECTION 7-REPLACEABLE PARTS

7-1 7-2 7-3

z 7-6

Display Board, Comporient Location Drawing, Dwg. No. 196-110. Display Board, Schematic Diagram, Dwg. No. 196.XL6 Digital Board, Component Location Drawing, Dwg. No. 196-100 Digital Board, Schematic Diagram, Dwg. No. 196-106. Analog Board, Component Location Drawing, Dwg. No. 196.120

Analog Board, Schematic Diagram, Dwg. No. 196-126

APPENDIX D

D-l D-2 D-3

tEEEBusCon@ration

IEEE Handshake Sequence .......

CommandCodes

............................................................................

......................................................................

......................................

....................................................

.. ;

..................................................

.........................................................

.........................................

..............................................

...............................

...........................................

;Y;~;

..............................................

...............................

............................

.~.-i..

..............

..................................

.................... ;. .. ; . ~; ;

‘.‘~.

.........

..................................

.;.

.............

6-5 6-5 6-6

6-7

6-8

1. ... 6-8

6-9

6-10 6-U.

6-12~

6-l3

~7-4

7-5

....... ; . 7-12

7-13

7-24 7-25

D-l

D-3

D-6

viii

SECTION 1

GENERAL INFORMATION

1.1 INTRODU~ION

The Keithley Model 196 System DMM is a five function autoranging~ digital multimeter. At 6% digit resolution, the LED display can display ~*3,@0,1lOO coo@s. The ran@ of this analog-to-digital (A/D) converter is greater t+q the nor: mal *l,999,999&tit~AAID converter used in many 6% &St DMMs. The built-in IEEE-488~ interface makes the instrument fully programmable over the IEEE-488 bus. The Model 196 can make the following basic measurements:

1. DC voltage measurements from lOOnV to 3OOV.

2. Resistance measurements from lOOpI tb’3OOM62.

3. TRMS AC voltage measurements from 1pV to 300V.

4. DC current me&urements from lnA to 3A.

5. TRMS AC current measurements from lnA to 3A.

In addition to the above~ mentioned measurement capabilities, the Model 196 can make:AC dB voltage and current measurements.

1.2 FEATURES

1.3 WARRANTY INFORMATION

Warranty information may be found on the inside front cover of this manual. Should it become necessary to exq c@e the warranty, contact your Keithley represent&e or the ~factory to determine the proper course of action. Keithley Instruments maintains service facilities in the United States, United Kingdom and throughout Europe. Information concerning the application, operation or service of your instrument may be directed to the applications engineer at any of these locations. Check the inside front cover for addresses.

1.4 MANUAL ADDENDA

Information concerning improvements or changes to the instrument which occur after the printing of this manual will be found on an addendum sheet included with the manual. Be sure to review these changes before attempting to operate or service the instrument.

1.5 SAFETY SYMBOLS AND TERMS

Some important Model 196 features include:

l 10 Character Alphanumeric Display-Easy to read 14seg-

ment LEDs used for readings and front panel messages.

*High Speed Measurement Rate-l000 readings per

second.

l Zero-Used to cancel offsets or establish baselines. A zero

value can be programmed from the front panel or over

the IEEE-488 bus.

l Filter-The weighted average digital filter can be set from

the front panel or over the bus.

l Data Store-Can stoti tip to 500 readings and is accessl%le

only over the bus.

l Digital Calibration-The instrument may be digitally

calibrated from either the front panel or over the bus.

l User Programmable Default Condition&&y inshument

measurement configuration can be established as the power-up default conditions.

l Translator Softwze-User defined words (stored in non-

volatile memory) can be used to replace standard command strings over the IEEE-488 bus.

l Offset Compensated Ohms-Used to correct for small er-

ror voltages in the measurement circuit.

The following safety symbols and terms are used in this manual or found on the Model 196.

The A

symbol on the instrument denotes that the user

should refer tom the -operating instruction iq this manual. The I/y on the instrument denotes that a potential of

300V or more may be present on the terminal(s). Standard safety practices should be observed when such dangerous levels are encomitered.

The WARNING used in this manual explains dangers that could result in personal injury or death.

The CAUTION used in this manual explains hazards that could damage the instrument:

1.6 SPECIFICATIONS

Detailed Model 196 specifications may be found preceding the 7hble of Contents oft &is manual. ~. ~~~~

l-l

1.7 INSPECTION

1.9 GETTING STARTED

The Model 196 System DMM was carefully inspected, both electrically and mechanically before shipment. After unpacking all items from the shipping carton, check for any obvious signs of physical damage that may have occurred during transit. Report any damage to the shipping~agent. Retain and use the original packing materials in case reshipment is necessary. The following items are shipped with every Model 196 order:

Model 196 System DMM Model 196 Instruction Manual

Safety Test Leads (Model 3751) Additional accessories as ordered.

Jf an additional instruction manual is required, order the manual package (Keithley Part Number 196-901-00). The manual package includes an instruction manual and any applicable addenda.

1.8 USING THE MODEL 196 MANUAL

This manual contains information necessrny for operating and servicing the Model 196 System DMM. The information is divided into the following sections:

l Section 1 contains general information about the Model

396 includiig that necessary to inspect the instrument and get it operating as quickly as possl%le.

l Section 2 contains detailed operating information on

using the front panel controls and programs, making connections and basic measuring techniques for each of the available measuring functions.

l Section 3 contains the information necessary to connect

the Model 196 to the IEEE488 bus and program operating modes and functions from a controller.

l Se&on 4 contains performance verification procedures

for the instrument. This information will be helpful if you wish to verify that the instrument is operating in compliance with its stated specifications.

l Section 5 contains a description of operating theory.

Analog, digital, power supply, and IEEE-488 interface operation is included.

0 Section 6 contains information for servicing the instru-

ment. This section includes information on fuse replacement, line voltage selection, calibration and troubleshooting.

l Section 7 contains replaceable parts information.

The Model 196 System DMM is a highly sophisticated instrument with many capabilities. To get the instrument up &id running quickly use the following procedure. For complete information on operating the Model 196 consult the appropriate section of this manual.

Power up

1. Plug the line cord intom~the rear anel power jack and plug the other end of the cordpinto an appropriate,

grounded power source. See paragraph 2.2.1 for more complete information.

2. Press in the POWER switch to apply power to the in-

shument. The instrument will power up in the 3CW DC

*ange.

Making Measurements ‘L Connect safety~shrouded testy leads to the front panel

VOLTS H.I and LO input terminals. Make sore the INPUT switch on the rear panel is in the in (FRONT)

position.

2. To make a voltage measurement, simply connect the in-

put leads to a DC voltage source (up to 3OOV) and take the reading from the display.

3. To change to a different measuring function, simply press the desired function button. For -pie, to measure resistance, press the OHMS button.

Using Front P.&e1 Programs Program selection is accomplished by pressing the PRGM

button followed by the button(s) eat corresponds to the program number or name. For example, to select Program 31 (IEEE), press the PRGM button and then the 3 and 1 buttons. ‘Ihble 2-7 lists and briefly describes the available front panel programs. Once a program is selected the following general rules will apply:

1. A displayed program condition can be entered by pressi”p the ENTER button.

2. Program conditions that prompt the user with a flashing

digit can be modified using the data buttons (0 through 9 and i).

3. Programs that contain alternate conditions can be

displayed by pressing one ofthe range buttons. Each press of one of these buttons toggles the display between the two available conditions.

1-2

GENERAL INFORMATION

4. A program will be executed when the ENTER button is pressed.

5. A program can be exited at any time and thus not eyecuted, by pressing the PRGM button.

Paragraph 2.7 provides the detailed information for using the front panel programs.

1.10 ACCESSORIES

The following accessories are available to enhance the Model l96s, capabilities.

Models lOl9A and 1019s Rack Mounting Kits-The Model

~1019A is a stationary rack mounting kit with two front

panels provided to enable either single or dual side-by-side mounting of the Model 196 or other similar Wthley instruments. The Model 10195 is a similar rack mounting kit with a sliding mount configuration.

Model X301 Temperature Probe-The Model 1301 is a rUgged low cost temperature probe designed to allow temperature measurements from -55 to I5O’C.

Model 16008 High Voltage Probe-The Model 16008 extends

DMM measurements to 40kV. Model 165150Ampere Current Shunt-The Model 1651 is

an external 0.00161 +J% 4terminal shunt, which permits current measurements from 0 to 50A AC or DC.

Model l&31 Clip-On Test Lead Set-The Model l68l’con tains two leads, 1.2m (4 ft.) long terminated with banana plugs and spring action clip probes.

Model 1754 Universal Test Lead Kit--The Model 1754 is a

12 piece test lead kit, with interchangeable plug-in accessories. Included in the kit is one set of test leads (l-red, l-black), two spade lugs, two standard b-a plugs, two phone tips (0.06 DIA.), two hooks and miniature alligator clips (with boots).

Model 5804 Test Lead Set-The Model 5804, used for 4terminal measurements, includes: two test probes with spring-loaded plunger clip adapters to fit test probes, two spring-loaded plunger test clips with in-line banana jacks, and four solid copper alligator clips with insulator boots.

Model 5805 Kelvin Probes-The Model 5805 includes two spring-loaded Kelvin test probes (one red, one black), with 48-inch banana plug cable assemblies. A set of eight replacement contacts for the Model 5805 Kelvin test probes is also available (Keithley PIN CS-551).

Model 5806 Kelvin Clip Lead Set-The Model 5806 includes

~two I+in clip test lead assemblies with banana plug ter-

mination (one red, one black). A set of eight replacement rubber bands for the lviode1~5806 is also available (Keithkey PIN GA-22).

Model 7087 IEEE-&3 Shielded Cables-The Model 7007 connects the Model 196 to the IEEE-488 bus using shielded cables to reduce electromagnetic interference (EMI). The Model 7Ow-1 is one meter in length and has a EMI shielded IEEE-488 connector at: each end. The Model 7007-2 is identical to the Model 7007-1, but is two meters in length.

Model 7088 IEEE488 Cables-The Model 7008~connects the Model 196 to the IEEE-488 bus. The Model 7008-3 is D.9m

(3 ft.) in length and has a~standard IEEE488 connector at each end. The Model 7008-6 cable is identical to the Model 7008-3, but~is 1.8m (6 ft.) in length.

Model 1682A RF Probe-The Model 1682A permits voltage measurements from lOOkHa to 25OMHz. AC to DC transfer accuracy is *ldB from lOOkFIr to 25OhJH.z at IV, peak responding, calibrated in RMS of a sine wave.

Model 1685 Clamp-On AC Probe-The Model 1685 measures AC current by clamping on to a single conductor. Interruption of the circuit is unnecessary. The Model

1685 detects currents by sensing the chsnglng magnetic field

produced by the current~flow.

Model I751 Safety Test Leads-Finger gu$.s and shrouded banana plugs help minimize the chance of making contact

with live circuitry.

Model 8573A IEEE488 Interface--The Model 8573A is an IEEE1188 standard interface designed to interface the IBM PC or XT computers to Keithley instrumentation over the

~IEEE-488 bus. The interface system contains two distinc-

tive parts an interface board containing logic~ to perform

the necessary hardware functions and the handler software (supplied on disk) to perform the required control func-

tions. These two important facets of the Model 857ZA join together to give the IBM advanced capabilities over lXE-488 interfaceable instrumentation.

l-311-4

SECTION 2

BASIC DMM OPERATION

2.1 INTRODUCTION

Operation of the Model 196 can be divided into two general

categories: front panel operation and IEEE-488 bus~operation. This section contains information necesssay to use the instrument from the front panel. Theses functions can also be programmed over the lEFE-488 bus, as described in Section 3.

2.2 POWER UP PROCEDURE

2.2.1 Line Power

Use the following procedure to connect the Model 196 to line power and power up the instrument.

1. Check that the instrument is set to correspond to the available line power. When the instrument leaves the factov, the internally selected line voltage is marked on the rear panel. Ranges are 105W25V or 2kW!5OV 5016OHz AC. If the line voltage setting of the instrument needs to be changed, refer to Section 6, paragraph 6.2 for the procedure. If the line frequency setting of the instrument needs to be checked and/or changed, utilize front panel Program 32 (see paragraph 2.7.8) after the instrument completes the power up sequence.

2. Connect the female end of the power cord to the AC receptacle on the rear panel of the instrument.~ Connect the other end of the cord to a grounded AC outlet.

WARNING The Model 196 is equipped with a 3-wire power cord that contains a separate ground wire and

is designed to be used with grounded outlets,

When proper connections are made, instrument chassis is connected to power line ground.

Failure to use a gmunded outlet may result in personal injury or death because of electric shock.

CAUTION

Be sure that the power line voltage agrees with the indicated range on the rear panel of the instrument. Failure to obsenre this precaution may result in instrument damage.

2.2.2 Power Up Sequence

The instrument can be turned on by pressing in the front panel POWER switch. The switch will be at the inner most position when the instrument is turned on. Upon ower up, the instrument will do a number of tests on itse 9 Tests are performed on memory (ROM, RAM and ETROM). If RAM or ROM fails, the instrument will lo& up. If ETROM FAILS, the message ‘TINCAL!’ will be displayed. See paragraph 67.2 for a complete description of the power up self test and recommendations to resolve failures.

2.2.3 Default Conditions

Default conditions can be defined as setup conditions that the instrument will return to when a particular feature or command is asserted. The Model 196 will return to either factory default conditions or user saved default conditions.

Factory Default Conditions Ate the factory, the Model 196 is set up so that the instru-

ment is configured to certain setup conditions on the initial power up. These factory default conditions are listed in Tables 2-l and 37 (located in Section 3). If alternate setup conditions are saved (see User Saved Default Conditions), the instrument can be returned to the factory default con-

ditions by running Program 37 (Reset). To retain the fac-

tory default condihons as power-up default conditions, run Program 30 (Save} immediately after executing kograrn 37 (Reset).

Sending device-dependent comman d I.0 over the IEEE-488 bus is equivalent to running Program 37 (Reset) and then Program 30 (Save).

2-l

Table 2-1. Factory Default Conditions

2.3 FRONT PANEL FAMILIARIZATION

Control/kahw

Zero value (rrogram ZERO)

dB dB Reference Value

(program dB) Filter Filter Value (Program FILTER)

MX+B Status (Program 4)

MX+B Parameters (Program 34) Multi

NOTE: The Model 196 is initially set for an IEEE address of 7. The line frequency is set to 50 nor 6OHz.

User Saved Default Conditions

Each function oft the Model 196 “remembers”~ the last measurement configuration that it was set up for (such as range, zero value, filter value, et+ Switching back and forth between functions will not affect the unique tonfiguratioq of each function. However, the instrument will “forget” the configurations on power-down unless they are saved.

Unique setup conditions can be saved by running front panel Program 30 (Save) or by sending device-dependent command Ll aver the IEBE-488 bus. These~tiser saved default conditions will prevsjl over the factory default conditions on power-up, or when a DCL or SDC is asserted over the bus.

IEEE Address and Lie Frequency Any IEEE address and line frequency setting can be saved

as default conditions by running Program 30 (Save) or by sending Ll over the bus. See paragraph 2.7 for complete information on Programs 31 (IEEE Address) and 32 (Line Frequency).

lexer (Program 6) ‘-’

HI/ LB

/l’ASS~~(l’rogrsm 5)

HI/Lo Limits (Program 35)

Ohms Compensation (Program R

kfault Condition

DCV 3cQV

6% Di ‘ts

Diiabgd

000.0000

Disabled

1.000000

Disabled

M=1.0OWOO~ ;~~

3=000.0000

Enabled

Disabled

+3.030000,

-3.o3clooo

Disabled

The front panel layout of the Model 196 is shown in Fiie Z-l. The following paragraphs describe the various components of the front panel in detail.

2.3.1 Display and Indicators

Display-The 10 character, alphanumeric, LED display is used to display numeric conversion data, range and function mnemonics (i.e. mv) and messages.

Function Indicators-The indicator that is on identifies which of the five operating functions is currently selected.

Rsnge Jndicator-When the instrument is in autorange the AUTO indicator light will be on.

Modifier Indicators-When the zero feature is enabled, the ZERO indicator will torn on. When filter is enabled, the FKTER indicator will turn on.

IEEE Status Indicators-These three indicators apply to instrument operation over the IEEE-488 bus. The RMT indicator shows when the instrument is in the IEEE-488 remote state. The TLK and LSN indicators show when the instrument is in the talk and listen states respectively. See Section 3 for detailed information on oueration over the bus.

2.3.2 Controls

.&lI front panel co&ols, except the POWER and C%L ENABLE switches, are momentary contact switches. Indicaton are located above certain buttons to show that they are enabled. Some buttons have secondary functions that are associated with front panel program operation. See paragraph 2-7 for detailed information on front panel prOg.3lllS.

POWER-The POWER switch controls AC power to the insbxment . Depressing and releasing the switch once tams the power on. Depressing and releasing the switch a second time turns the power off. The correct positions footi\and off are marked on the front panel by the POWER

El FUNCTION GROUP

NOTE

An ‘TJNCAI!’ error will set the IEEE address to 7 and the line frequency to 6OHz.

2-2

DCV-The DCV button places the instrument in the DC volts measurement mode. The secondary function of this

button is to enter the i sign. See paragraph 2.6.4 for DCV

measurements.

BASIC DMM OPERATION

Figure 2-1. Model 196 Front Panel

ACV-The ACV button places the instrument in the AC volts measurement mode. The secondary function of this button is to enter the number 0. See paragraph 26.7 for ACV measurements.

&The fl button places the instrument in the ohms measurement mode. The secondary function of this button is to enter the number 1. See paragraph 2.6.6~for resistance measurements.

DCA-The DCA button places the instrument in the DC amps measurement mode. The secondary function of this button is to enter the number 2. See paragraph 26.8 for DC4 measurements.

ACA-The ACA button places the instrument in the AC

amps measurement mode. The secondary function of this

button is to enter the number 3. See paragraph 2.6.8 for ACA measurements.

RANGE GROUP

!zl

Manual-Each time the A button is pressed, the instrument will move up one range, while the V button will move

the instrument down one range each time its is pressed. Pressing either of these buttons will cancel autorange, if it was previous selected. The secondary functions of these buttons are tom enter the number 4 (V) and number 5 (A).

AUTO-The AUTO button places the instrument in the autorange mode. While in this mode, the instrument will go to the best range to measure the applied signal. Autoranging is available for all functions and ranges. Autoranging may be cancelled by pressing the AUTO button or one of the manual range buttons. The secondary function of this button is to enter the number 6.

ZERO-The ZERO button turns on the ZERO indicator and causes the displayed reading to be subtracted from subsequent readings. This feature allows for zero correction or storage of baseline values. The secondary function of this

button is to select the ZERO program and enter the number

Z Refer to paragraph 2.62 for detailed information on the

zero feature.

2-3

SAS\C DMM OPERATION

FIUER-The FIWER button turns on the FIUEl7 indicator and causes the instrument to start weighted averaging (1 to l/99) fhe readings. The factory default weighted average is l/10, but may be changed using the PIITER program (see paragraph 2.7.16). See paragraph 2.6.3 for filter operation. Selectin the PILTEK rogiam is one of the secondary functionsof&isbutton.&eothersecondaryfunctionisto~nter the number 8.

dB-The dB button places the inshument~~in the dB measurement mode and may be used with the ACV and ACA functions. Under factory default conditions, measure-

ments are referenced to 1V or lmA. However, the dB program may be used to change the referqce @ell. ‘JTh$ seconY day function of this button is to select the dB program and enter the number 9. See paragriph 2.6.9 for dB measurements.

CONTROL GROUP

PRGM-This button is used tom enter the fronts panel pro-

gram mode.

ENTER-This button is used to enter program parameters. This button will also trigger a reading when the instruments

is in a one-shot trigger mode.

the LOCAL button will be inoperative. See Section 3 for informa$on on operating the instnunent-over the IEEE488

bus.

2.3.3 Input Terminals q

The ~input terminals are intended to be used with safety shrouded test leads to help minimize the possibility of contact with live cikuits. Note that the terminals sre duplicated sideways on the rear panel and that the INPUT switch (also located on the rear panel) determines which set of termin& is Bctive.

VOLTS 0HMS~i-J.I akd LQ-l’he VOLTS OHMS Hl atid LO terminals are used for making DC volts, AC volts and two-

wire resistance measurements. AMPS and LO-The AMPS and LO terminals are used for

making DC current and AC cUrrent measurem&s. OHMS SENSE HI and LO--The OHMS SENSE HI and LO

terminals are used with the VOJXS OHMS HI and LO terminals to make four-wire resistance measurements.

El LQCA&When the instrument is in the IEEE-488 remote state (RM’I indicator on), the LOCAL button will return the instrument to front panel operation. However, if local lockout (LLO) was asserted over the IEEE-488 bus,

2.3.4 Calibration Enable Switch q

Calibration of the Model 196 can only be done if the CAL ENABLE switch is in the enable position. See paragraph

6.4 for details.

2-4

BASIC DMM OPERATION

2.4 REAR PANEL FAMILIARIZATION

The reax panel of the Model 196 is shown in Figure 2-2.

2.4.1 Controls

ra T TkTc TIC%TTA,-C -t-L:- a.r.2~L -A,-~ the hment

Iable lme voltage. see paragrapn 6.2 for the proset this switch.

INPUT-The INPUT switch connects the instrument to either the front panel input terminals or the rear panel input terminals. This switch operates in same manner as the power switch. The front panel input terminals are selected when the switch is in the “in’ position and the rear panel input terminals are selected when the switch is in the “0uV position.

2.4.2 Connectors and Terminals

~~~ pJ

AC Receptacle-Power is applied through the supplied power cord to the 3-terminal AC receptacle. Note that the selected supply voltage is marked on the rear panel near the line voltage switch.

El Input Terminals-The rear panel input terminals per-

form the same functions as the front panel input terminals. Paragraph 2.3.3 contains the description of the input terminals.

mu IEEE-488 Car

nect the ins,e functions ym -rl-l

used to apply pulses to trigger the Model 196 to take one or more readings, depending on the selected trigger mode.

x5 14,&ed below the connector.

EXTERNAL TRIGGER Input-This BNC~connector is

mector-This connector is used to connt to the IEEE-483 bus. IEEE interface

Figure 2-2. Model 196 Rear Panel

2-5

BASIC DMf.4 OPERATION

VOITMFXER COMPLETE Output-T% BNC output connector provides a TTLcompatible negative-going pulse when the Model 196 has completed a reading. It is useful for triggering other inshumentation.

2.4.3. Fuses

LINE FUSE-The line fuse provides protection for the AC power line input. Refer to paragraph 6.3.1 for the line fuse replacement procedure.

CURRENT FUSkhe 3A current fuse provides protection for the current measurement circoits of the instrument. Refer to paragraph 63.2 for the cwr$nt fuse replacement procedure.

To optimize safety when measuring voltage in high energy distribution circuits, read and use the directions in the following warning.

WARNING Dangerous arcs of an explosive nature in a high energy circuit can cause severe personal injury or death. If the meter is connected to a high energy circuit when set to a current range, low resistance range or any other low impedance range, the circuit is virtually shorted. Dangerous arcing can also result when the meter is set to a voltage range if the minimum voltage spacing is reduced.

2.5 ERROR DISPLAY MESSAGES

Table 2-2 lists and explains the various display messages assodated with incorrect front panel operation of the Model

196.

Table 2-2. Error Messages

Message

UNCAL

NO PROGRAM

O.VERFLO KQ

TRIG-ERROR

AC ONLY

NO RANGE

CONFLICI

Explanation

EIPROM failure on power up. See paragraph 6.7.2. Invalid entry while trying to select program. Overrange-Decimal point position and mnemonics define function and range (3kfl range shown).~ Th: number of characters in the “OVERFLO” message defines the display resolution (6Yzd resolution

shown). Trigger received while still processing reading from last trigger.

Selecting dB with in&ument fitit in ACV or ACA. Pressing a range button while in ACV dB or ACA dB. 196 in invalid state (i.e. dB function), when entering calibratioti p*ogram.

2.6 BASIC MEASUREMENTS

When making measurements in high energy circuits use test leads that meet the follcwing requirements:

l Test leads should be folly insulated. l Only use test leads that can be connected to the circuit

(e.~,jz~~~~.clips, spade lugs, etc.) for hands-off

l Do not use test leads that decrease voltage spacing. This

diminishes arc protection and creates a hazardous condition.

Use the following sequence when testing power circuits:

1. De-energize the circuit using the regular installed connect-disconnect device such as the circuit breaker, main switch, etc.

2. Attach the test leads to the circuit under test. Use appropriate safety rated lead~s for this application.

3. Set the DMM to the proper function and range.

4. Energize the circuit using the installed connectdisconnect device and make measurenwnts without disconnecting the DMM.

5. De-energize the circuit using the installed connectdisconnect device.

6. Disconnect the test~leads from the circuit under test.

WARNING The maximum common-mode input voltage (the voltage between inout LO and chassis around) is 506J peak. Exceeding this value may create s shock hazard.

The following paragraphs describe the basic pwxdures for making voltage, resJs@~ce, current, and~dB measurements.

2-6

BASIC DMM OPERATION

2.6.1 Warm Up Period

The Model 196 is usable immediately when it is first turned on. However, the instrument must be allowed to warm up for at least~ two hours to achieve rated accuracy.

2.6.2 Zero

The zero feature serves as a means of baseline suppression by aIlowing a stored offset value to be subtracted from

subsequent readings. When the ZERO button is pressed, the instrument takes the currently displayed reading as a baseline value. All subsequent readings represent~the difference between the applied signal level and the ~stored baseline.

A baseline level can be established for any or all measure-

ment functions and is remembered by each function. For

example, a 1OV baseline can be established on DCV, a 5V

baseline can be established on ACV and a 1Okll baseline

can be established on OHMS. Theses levels will snot be

cancelled by switching back and forth between functioti.

Once a baseline is established for a measurement function,

that stored level will be the same regardless of what range

the Model 196 is on. For example, if 1V is established

as the baseline on the 3V range, then the baseline will also

be 1V on the 30V through 30lV ranges. A aem baseline level

canbeaslaigeasfullrange. ~~

NOTE

The followirg discussion on dynamic range is

based on a display resolution of 6% digits. At 5’/zd resolution, the number of counts would be reduced by a factor of 10. At 4Yzd resolution, counts would be reduced by a factor of 100 and 3%d resolution would reduce counts by a factor of 1000.

Example l-The instrument is set to the 3V DC range and a maximum -3.03OOOOV is established as the zero value.

When -3.03OOOOV is connected to the input of the Model 196, the display will read O.OMlOOClV. When +3.03OCEOV is co.nnected to the input, the display will read +60600ooV. Thus, the dynamic measurement range of the Model 196 is OV to 6.06V, which is 6060000 counts.

Example 2-Ihe instrument is still set to the 3V DC range, but a maximum +3.03oOOOV ia the zero level. When

+3.03oO~CGV is connected to the input of the Model 196, the display will read O.O@XtOOV When Y3.0~ is connected to the input, the display will read -6.06OOOCV. Thus the dynamic measurements range of the instrument is -6.06V to OV, which is still 6060000 counts.

Zero Correction-The Model 196 must be properly zeroed when using the 3OOmV DC or the 3OOB range in order to

achieve rated accuracy specifications. To use ZERO for zero

correction, perform the following steps:

Disable zero, if presently enabled, by pressing the

ZERO button. The ZERO indicator will turn off. Select the 3oOmV DC or the 30022 range.

2. Connect the test leads to the input of the Model 196 and

3. short them together. If four-wire resistance measurements are to be made, connect and short all four leads together. Allow any thermals to stabilize.

Note: At5% and 6%~digit resolution, low level measurement techniques need to be employed. Use Kelvin test leads or shielded test leads. See paragraph 2.6.5 for low level measurement considerations.

Press the ZERO button. The display will read zero.

4. Remove the short and connect thetest leads to the signal

5. or resistance to be measured.

Note: Test lead, resistance is also~ compensated for when zeroing the 3OO’J range with the above procedure.

By design, the dynamic measurement range of the Model

196, at 6%-d@ resolution, is M)60000 counts.1 With zero disabled, the displayed reading range of the instrument is

*303ooOO counts. With zero enabled, the Model 196 has

the capability to-display ~606OCOO counts. This increased

display range ensures that the dynamic measurement range of the instrument is not reduced when using a zero baseline

value. The following two examples will use the maximum

allowable zero values (3030000 counts and -3030008 counts) to show that dynamic measurement range wilI not

be reduced. It is important to note that the increased display

range does not increase the to the instrument. For example, on the 3V range, the Model 196 will always overrange when more than k3.03V is connected to the input.

maximum allowable input level

Baseline Levels-Baseline values can be established by either applying baseline levels to the instrument or by setting baseline values with the front panel ZERO program. paragraph 27’15 contains the complete procedure for using the ZERO program. To establish a baseline level by applying a level to the Model 196, perform the following steps:

1. Disable zero, if presently enabled, by pressing the ZERO button. The ZERO indicator will turn off.

2. Sele&a function and range that is appropriate for the

anticipated measurement.

3. Chnect the desired baseline level to the input -of the

Model 196 and note that level on the display

2.7

BASIC DMM OPERATION

4. Press the ZERO button. The display will zero and the ZERO indicator will be enabled. The previously

displayed reading will be the stored baseline. The rero baseline value will also be stored in Program ZERO, replacing the previous zero value.

WARNING

With ZERO enabled, a hazardous voltage

baseline level (rt4OV or more), not displayed, may be present on the input terminals. If not sure what is applied to the input, assume that a hazardous voltage is present.

5. Disconnect the stored signal from the input and connect the signal to be measured in its place. Subsequent~

readings will be the difference between the stored value and the applied ‘signal.

Notes:

1. Disablmg zero cancels the zero baseline value on that

selected function. However, since the zero value is automatically stored in Program ZERO, the zero baseline value can be retrieved by using the program as long as

the ZERO button is not ~again pressed (see paragraph

2.Xi5 for details). Pressing the ZERO button, thus enabling zero, will wipe out the previous baseline value in Pro-

gram ZERO. Baselines established on other functions are not affected.

2. To store a new baseline on a selected function, zero must first be disabled and then enabled again. The new value will be stored with the first triggered conversion. The baseline value wi.lI also be stored as~the zero value in Program ZERO, cancelling the previously stored value.

3. Setting the range lower than the suppressed value wi.lI overrange the display; the instrument will display the

overrange message under theses conditions.

4. When the ZERO button is pressed to enable zero, the ZERO indicator light will blink until an on scale reading is available to use as a zero level.

2.6.3 Filter

The Model 196 incorporates two filters; a digital filter controlled from either the front panel or over the IEEE-438 bus,

and an internal filter controlled exclusively from over the

bus.

The factory default filter weighting is l/l@ but can be changed to a weighting from 1 (l/l) to-1199 with the use of the FILTER program. While in the program, the Model 196 will only display the denominator of the filter Weighting. For example, if the current filter weighting is l/lo, the FILTER program will display it as the value l0. Thus, filter value as usecl in this discussion refers to the values displayed by the Model 196 when in the FILTER program.

A falter value can be set for any or all measurement functions and is remembered by each function. For example, a filter value of 20 can be set for DCV and a filter value of 53 can be set~for ACV These filter values will not be cancelled by switching back and forth between functions.

An advantage of using the filter is to stabilize the reading

-of a noisy input level. A consideration of filter usage is that the larger the weighting, the longer the response time of the display. Perform the following procedure to use the filter:

1. If it is desired to cb.eck and/or change the filter value, utilize Program FIITER as explained in paragraph 27.16.

2. Press the FILTER button. The FILm indicator will turn on.

Notes:

1. When the filter is enabled, readings will be filtered before being displayed. See Digital Filter Theory.

2. Pressing the FILIER button a second time will disable the filter.

3. After a reading is triggered (continuous or one-shot), the FIITER indicator light will blink for three time constants. A time constant is measured in readings. The number of readings in one time constant is equal to the filter value. For example, for a filter value of IO, one time constant~ is equal to 10 readings and three time constants would be equal to 30 readings. The blinking duration will be shorter in the 3%d mode since that has the fastest reading rate.

4. In a continuous trigger mode, a reading that is outside the filter window wiIl cause the FILTER indicator to blink for one time constant.

Digital Filter Theory-The mathematical representation of the weighted average digital Elter is as follows:

Digital Filter-The Model 196 utilizes a digital filter to attenuate excess noise present on input signals. This filter is a weighted average type.

2-6

(new reading -AVG(t-I))

AVG(t) = AVG(t-1) +

BASIC DMM OPERATION

where,

AVG(t) = displayed average AVG(t-1) = old displayed average

F = weighting factor (filter value)

As with any filter, the Model 196 digital filter will affect reading response time. The step response for this fiker~is of the form:

step response = l-K’“+”

Where,

“K” is a constant based on the filter weighting~ factor

The step occurs when n=O. n=l is the first ream after

the step, n=2 is the second reading, etc. Therefore:

a+1

step response = l-

Example: F=10

n=5

l- Y-

( )

displayed value will be the new reading, and weighted averaging WilI start from this point. The step response was one reding to tbis change. The window in the Model 196 filter is lO,OoO counts for 6Yzd resolution, 1000 counts for 5Yzd, 7.00~ counts for 4Yzd and 10 counts for 31/2d.

Internal Filter-In addition to the front panel digital filter, an inter& running avenge digita~fiher & -cd when msking high ~oh$ion and high sensitivity rriek+reme$k qe enable&able status of the filter is controlled over the IEEE bus. However, under factory default conditions, the in&~ment powers up with the filter enabled. When enabled, this filtering only occurs when the instniment is in the 5Yz OI blh-digit resolution niode.

Notes:

1. The front panel FILTER indicator light does not turn on when the internal filter is activated. The indicator is only used with the front~panel digital filter.

2. Contding the internal filter (on/off) over the IEEE bus

is explained in paragraph 3.9.22.

3. In a one-shot trigger mode, the Model 196 will not output a reading until both filters have settled. Three time

constants are used to allow the filters to settle. A time constant is measured in readings. The number of readings in one time constant is equal to the filter value. For example, for a filter value of lo,, three time constants would be equal to 30 readings. If both the internal filter and the front panel filter are in use, the time constant is the sum of both filter values.

4. Filter windows for the internal filter function in the same

manner as the windows for the front panel filter. However, the window sizes of the internal filter are much bnaller than the front panel filter window sizes.

Five readings sfter the step occurs, the display will be at

47% of the step change. After 10 readings (n=lO), the display will be at 168% and after 20 readings, the display wiU be at ~88%. The more the readings, the closer the display will be to the step change.

To speed the response to large step changes, the Model 196

digital filter employs a “windo+ around the displayed average. As long as new readings are within this window,

the displayed value is based on the weighted avemge equa-

tion. If a new reading is outside of this window, the

2.6.4 DC Voltage Measurements

The Model 196 can be.~ used tom make DC voltage measurements in the range oft-*XlOnV to k3OOV. Use the following procedure to make DC voltage measurements.

1. Select the DC volts fundion by pressing the DCV button.

2. Select a range consistent with the expected voltage or use autorange.

3. Select the front or rear panel input terminals with the INPUT switch.

NOTE

The 3oOmV DC range requires zero to be set in

order to achieve rated accuracy. The zero correction procedure can be found in paragraph 2.6.2.

2-9

BASIC DMM OPERATION

4. Connect the signal to be measured to the selected input terminals as shown in Figure 2-3.

5. T&e the reading from the display

CAUTION:

MAXIFIUM INPUT

INPUT RESISTANCE

= 300V RtlS. 425V PEAK = WJdiM:;Vs > IGIl

300G: 10.llln

Figure 2-3. DC Voltage Measurements

2.6.6 Low-Level Measurement Considerations

Accuracy Considerations-For sensitive measurements,

other external considerations besides the Model I.96 will affect the accumcy. Effects not noticeable wheti working

with higher voltages sre significant in nanovolt and

microvolt signals. The Model 196 reads only the signal received at its input; therefore, it is important that tb.is signal be properly bansmitted from the source. The following paragraphs indicate factors which affect accuracy noise, source resistance, thermal emfs and stray pick-up.

Noise and Source Resistance-The limit of sensitivity in

measuring voltages with the Model 196 is determined by

the noise present. The noise voltage at the Model 1% input increases with sauce resistance.

For high impedance sources, the generated ~noise can become significant when using the most sensitive mnge

(3COmV, 6Yzd) of the Model 196. As an -pie of determining e, (noise voltage generation due to Johnson noise of the somce resistance), assume that the Model 196 is con-

nected to a voltage source with an internal resistance of

lM0. At a mom temperature of 20°C, the p-p noise Voltage

generated over a bandwidth of lHz will be:

635xXP’~Rxf

e, = e, = 6.35 x lP d/(1 x W) (1)

Thus, an e, of 0.635pV would be displayed at 6Yzd resolulion as an additional six diaits of noise on the Model 196. To compensate for the dispgyed noise, use digital filtering and then zero out the settled offset.

..~

Shielding-AC voltages ‘Which &e extremely k&i cornpared with the DC signal may erroneously produce a DC output. Therefore, if there is AC interference, the~~circuit

should be shielded with the shield connected to the Model

196 input Lo (particularly for low-level sources). Impropw shielding can cause the Model 1% to behave in one or more of the following ways:

1. Unexpected offset voltages.

2. Inconsistent readings between ranges.

3. Sudden shifts in reading.

To minimjze pick-up, keep-the voltage source and the Model 196 away from strong AC magnetic sources. The voltage induced due to magnetic flux is proportional to the area of the loop formed by the input leads. Therefore, minimize the loop area of the input leads and connect each

signd at ody one point.

T&rmal EMFs-Thermal emfs (thermoelectric potentials) are generated by thermal differences between the junction of dissimilar metals. These can be large compared to the

signal which the Model 196 can measure. Thermal emfs can cause the following problems:

-1. Instability or zero offset is much higher than expected.

2. The reading is sensitive to (and responds to) temperature changes. This can be demonstrated by touching the circuit, by placing a heat source near the circuit or by a

regular pattern of instability (corresponding to heating and air-conditioning systems or changes in sunlight).

3. To minim&e the drift caused by thermal emfs, use copper leads to connect the circuit to the Model 196. A banana plug is generally suitable and generates just a few microvolts. A clean copper conductor such ss #lO bus wire is about the best for this application. The leads

to the input may be shielded or unshielded, as necessary.

Refer to Shielding.

Widely varying temperatwes within the circuit can also create thermal ends. Therefor& maintain Constant temperatures to

minimize these thermal ends. A card-

board box around the circuit under test also helps by

minimking air currents.

5. The ZERO cOntro1 can be used to null out constant off-

set voltages.

2-10

e, = 0.635fiV

BASIC DMM OPERATION

2.6.6 Resistance Measurements

The Model 196 can make resistance measurements from

lOO#-l to 3CGMtI. The Model 196 provides automatic selection of 2-terminal or 4terminal resistance measurements. This means that if the ohms sense leads are not connected, the measurement is done Zterminal. If the sense leads are connected, the measurement is done 4terininaI. For 4terminal measurements, rated accuracy can be obtained

as long as the msximum lead resistance does not exceed the values listed in Table 2-3. For best results on the 3008

3kQ and 3OkQ ranges, it is recommended that 4terminal

measurements be made to eliminate errors caused by the

voltage drop across the test leads which will occur when

2-terminal measurements are made. The Model 5806 Kelvin

Test Lead Set is ideal for low resistance 4terminal

Offset-Compensated Ohms-Offs&-compensated ohms is used to compensate for voltage potentials (such as thermal EMFs) across the device under test. This feature eliminates errors due to a low level external voltage source configured in series with the unknown resistor. Offsets up to KhnV on the 3OOn range and up to BlOmV on the other ranges

can be corrected with offset-compensation. This feature can be used for both 2-terminal and 4terminal resistance measurements up to 30k61. Offset-compensation is selected through front panel Program !I (see paragraph 27.14).

especially the 3000 range. After offset-compep.sation is enabled, the Model 1% should be properly zeroed.

To make resistance measurements, proceed as follows:

L Select the ohms function by pressing the Q button.

2. Select a range consistent with the expected resistance or

use autorange.

3. Select the f&t or rear panei input terminals using the INPUT switch.

4. Turn offset-compensation on or off as needed, using Pm-

gram 0.

NOTE

If offset-compensatio~n is being used, the 3ooI1,

3ka and 3OkQ ranges require zero to be set in

order to achieve the best accuracy. The zero car-

rection procedure is located in paragraph 2.6.2.

5. For 2-terminal measurements connect the resistance to the instnunent as shown in Figs 2-4. For 4terminal measurements connect the resistance to the instrument as shown in F&ire 2-5.

CAUTlON

During ohms offset compensated resistance measurements, the Model 196 performs the following steps for each conversion:

1. Makes a normal resistance meaS,mment of the device. In general, this consists of sourcing a current thmu the device, and measuring the voltage dmp acro~ device.

2. Turns off the internal -nt source and again measures

the voltage drop across the device. This is the voltage caused by an external source.

3. Calculates and displays the corrected resistance value.

Offset-Compensated ohms not only cowxts for small error voltages in the measurement circuit, but also compensates for thermal voltages generated withim the Model 196. In normal ohms, these thermal EMF offsets are accounted for during c&ration. Therefore, enabling offset-compensation wilI cause these offsets to appear in the’ readings, Figure 2-4. Two-Terminal Resistance Measurements

tfz

The maximum input voltage between the HI anti LO input terminals is 425V peak or 300V

RMS. Do not exceed these values or instru- ment damage may occur.

6. Take the reading from the’display.

OPTIONAL SHIEY

SHKEf~D

NODEL 196

---

I-

L---~-I

UNDER TEST

2-11

BASIC DMM OPERATION

OPTIONAL SHIELO

-~~- -

B.&rward bias the diode by connecting the red terminal

of the Model 196 to positive side of the diode. A good diode will typically measure between 3OOn to IkQ.

C.Reverse bias the diode by reversing the connections

on the diode. A good diode will overrange the display.

MODEL 196

Figure 2-5. Four-Terminal Resistance Measurements

MODEL 196

CAUTION:

MAX I MUM INPUT = 300V RMS, 425V PEAK. 1O’V.H. INPUT IMPEDANCE = 1Hf-1 SHUNTED BY < 120pF

Figure 2-6. TRMS AC Voltage Measurement

Notes:

1. With ohms compensation active (Progam a), the 61 indicator light will blink when the ohms function is

selected.

2. Table 2-3 shows the current output for each resistance range.

3. It helps to shield resistance greater than IOOkQ to achieve a stable reading. Place the resistance in a shielded enclosure and electrically connect the shield to the LQ input terminal of the instrument.

4. Diode Test-The 3kQ range can be used to test diodes as

MlOWS: A. Select the 3kO range.

Table 2-3. Resistance Ranges

Maximum Test Lead

6%d Nominal Resistance (Q) for

Range 1 Resolutim I-Short 1 -3 Count Error (Wzd)

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*5%d resolution only

NOTE: Typical open circuit voltage is 5V.

2.6.7 TRMS AC Voltage Measurements

The instrument can make TRMS AC voltage measurements from l$I to 3OOV. To measwe AC volts, proceed as follows:

1. Select the AC volts function by pressing the ACV button.

2. Select a range con$stent with the expeqed voltage or use autorange.

3. Select the front or rear panel input terminals using the

INPUT switch.

NOTE

There is a small amount of offset (typically 150

counts at 5%d) present when using the ACV function. Do not zero this level o-ut. Paragraph 2.6.10

provides an explanation of AC voltage offset.

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4. Connecbthe signal to be measured to the selected input

terminals as shown in Figure 2-6.

5. Take the reading from the display.

BASIC DMM OPERATION

Clarifications of TRMS ACV Spedfications:

”

Msximum Allowable Input-The following graph summarizes the maximum input based on ~the lWV*Hz

specification.

MAXIIIUH INPUT TRt4S AC VOLTS

FREOUENCY-HZ

2.8.8 Current Measurements (DC or TRMS AC)

The Model 196 can m&e DC or TRW AC current measure:

ments from lnA (at 5Yrd resolution) to 34. Use the following procedure to make current measurements.

1. Select the DC current or AC current function by pressing the DCA or ACA button respectively.

2. Select a range consistent with the expected current or use autorange.

3. Select the front or rear panel input terminals using the

INPUT switch.

4. Connect the signal to be measured to the selected input

terminals as shown in Figure 2-7.

5. Take the reading from the display.

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CAUTION: MAXIMUM CONTINUOUS INPUT=3A

_ ._..

~. .-

Settling Time-lsec to within 0.1% of change in reading.

This the specification is for analog circuitry to settle and

does not in&de AID conversion time.

Notes:

1. See paragraph 26.10 for TRMS measurement conSid&

&iOllS.

2. When making TRMS AC voltage measurements below

45Hz, enable the front panel filter modifier to obtain stable readings. A filter value of 10 is recommended.

3. To make low frequency AC mea%uenients in the range

of lOHz to 2oH.z: A. The ACV function must be selected. B. Digital filtering must be used to obtain a stable

reading.

C. Allow enough settling time before taking the reading.

Figure 2-7. Current Measurements

2.8.9 dB Measurements

The dB measurement mode makes it pocisible to compress

a large range of~measurements into a much smaller scope. AC dB measurements can be made with the instrument in the ACV or AC4 function. The relationship between dB and voltage and currentxan be expressed by the followmg equations:

dB = 20 log .%

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