Keithley 1728, 1722, 173, 172 Service manual

Models 172,173

Instruction Manual

Contains Operating and Servicing/Calibration Information for Models 172,173,1722, and 1728

Publication Date: October, 1977

Keithley Instruments, Inc.

Instrument Division

Cleveland, Ohio, U.S.A.

Document Number: 28262

INSTRUCTION MANUAL

Dlgltat Multlmeter

Models 172,173

[Contalnr Operating and SafuWno/~bmtlon In!omuNon For Moddr 172,173,1722, and 1728.1

‘1

KEITHLEY

INSTRUMENTS

m

INSTRUCTION MANUAL

Digital Multimeter

Models 172,

173

THIRD PRINTING,

DOCUMENT NO. 28262, REVISION CODE CC

OCT. 1977, CLEVELAND, OHIO U.S.A.

CONTENTS

INSTRUCTION MANUAL

Dlgltal hlultlmeler

Models 172,173

I Section

CONTENTS

ILLUSTRATIONS.

SPECIFICATIONS ............

I. GENERAL INFORMATION.

l-l.

I

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

l-3. 1-4.

I

l-5. l-6.

OPERATING INSTRUCTIONS

3-l.

3-2.

;I;. HOW TO SELECT FUNCTION

;I?;. HOW TO USE MODEL 172/173 OFF-GROUND: : : : : : : : : :

I ,

I

3-11. HOW TO USE OPTIONAL PROBES AND SHUNTS. ........

3-12. HOW TO USE THE MODEL 1722 DIGITAL INTERFACE. .....

4.

ACCESSORIES ....................

4-l.

4-4. 4-5. 4-6.

4-7.

I:

THEORY OF OPERATION.

5.

5-l. GENERAL ........................

I i

I

5-9.

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

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

QARRANTY INFORMATION . . . : : : : : : : : : : : : :

CHANGE NOTICE. . . . . . . . .

OPTIONAL MODEL 1728 RECHARGEABL; ;A;T;R; PACK: : : :

OPTIONAL MODEL 1722 DIGITAL INTERFACE. . . . . . . .

GENERAL ........................

HOW TO SELECT POWER. HOW TO SELECT RANGE.

HOW TO MEASURE VOLTAGE ........

HOW TO MEASURE CURRENT (MODEL 172 ONLY): : : : : : : : HOW TO MEASURE CURRENT (MODEL

HOW TO MEASURE RESISTANCE. .. .. ... : : : : : : :

FURTHER MEASUREMENT CONSIDERATIONS

GENERAL..................:::: ::

POWER OPTIONS.

ISOLATED DIGITAL OUTPUT. ........

RACK MOUNTING. PROBE AND SHUNTS CABLES AND CONNECTORS. MISCELLANEOUS.

INPUT SIGNAL CONDITIONING. ..............

POWER SUPPLY, SCHEMATIC NO. 28067D ..........

DISPLAY BOARD PC-403 SCHEMATIC NO. 274780. ......

CURRENT BOARD, SCHEMATIC NO. 27478D. .........

MODEL 1728 RECHARGEABLE BATTERY PACK .........

ANALOG-TO-DIGITAL CONVERTER. MODEL 1722 DIGITAL INTERFACE DETAILED II-WIRE OHMS OPERATION ... : : : : : : : : :

.......

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

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

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

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

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

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

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

: : : : : : : : : : : : : : : : : : : : : :

: : : : : : : : : : : : : : : : : : : : : : I-I

. . . .

.

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

.

173

ONLY).

. . . . .

. . .

. . * .

: : : : : : :

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

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

....

. . . * . . . . . . . . . . . . . . . . . . . . . . . .

.. ii

. . . . . .

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

. I-l . l-1

. l-l

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

. . . .

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

. . . .

. . . 3-11

. . . . 3-12

. .

. . . .

. * . .

. . . .

. * . . * . . .

. . . .

. . .

. 5-9

. . . .

Page

iii

"

l-l

1-I

2-l

3-l 3-l 3-l 3-2 3-3 3-4 3-5 3-6 3-7 3-8

3-13

4-l

4- 1 4-l 4-l 4-l 4-4 4-5 4-5 5-l 5-1 5-2

5-10 5-12

S-13 5-13 5-22

5-26

ii

AA

I

INSTRUCTION MANUAL

Digllel Mulllmeter Model8 172. 173

I /section

6.

MAINTENANCE.

6-1.

6-2.

6-3.

6-4. ADJUSTMENT/CALIBRATION PR&D;R; : : : : : : : : : : : : : : : : : : : :

6-5.

REPLACEABLE PARTS. . . . . . . . . . : : : : : : : : : : : : : : : : : : : : :

7.

7-1.

7-2.

J-3.

GENERAL. REQUIRED TEST EQUIPMENT.

PERFORMANCE VERIFICATION TROUBLESHOOTING AND REPAIR , .

GENERAL. . . ORDERING INFORMATiON : : : : : : : : : : : : : : : : : : : : : : : : : :

SCHEMATICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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

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

>_I

CONTENTS (continued)

: : : : : : : : : : : : : : : : :

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

ILLUSTRATIONS

Page

6-1 6-1 6-I

6-3

6-15 /

6-19,

J-1 1 ;:; j

J-1 )

Title Fi ure No. g

I

:

4

2 z

9 IO II Typical 2 WIRE Resistance Measurement 12

13

I4 I5

16

17

18

19

20

21

22

23 24

25 26

27

28

29 30

;:

;:a.

-

34b. Four-Wire Ohms Measuring Technique .................

Dimensional Data. Tilt Bail Positions Front Panel Bottom View Showing Line Cord

Rear Panel Showing Current Fuse and Check Points. ..........

Model

Installation of Battery Pack.

Front Panel Pushbutton Selection. Typical Model Typical Model

Typical 4 WIRE Resistance Measurement

Semiconductor Diode and Transistor Testing. .............

Illustration of Floating Operation.

Model

Installation of Model Connector Pin Identification. Card-Edge Connectors. Location of Jumpers and Pull-Ups on Model

Model 1010 Single Rack Mounting Kit. ..............

Model Overall Block Diagram of Model DC Volts Input Circuit

Simplified AC Attenuator Circuit AC Converter Circuit Digital Display Multiplex Scheme Basic Functional Blocks of A/D Converter Basic Charge-Balance Converter Operating Waveforms of A/D Converter Simplified Schematic of A/D Converter. Detailed Schematic of A/D Converter.

A/D Converter System Timing. Model

Simplified Ohms Diagram (Shown in Z-WIRE Configuration). ......

1728

1722

1017

1722

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

Rechargeable Battery Pack.

Digital Output Interface

Dual Rack Mounting Kit.

Block Diagram

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

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

172

Current Display

I73

Current Display

1722.

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

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

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

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

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

lJ2/173

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

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

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

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

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

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

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

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

1722. ...........

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

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

.......

1 : ‘.‘.‘: : : : : : :

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

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

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

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

................ .5-20

: :

:

.

Page

iv

vi

t-2

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

3-J

3-9 3-10 3-11 3-14 3-15 3-17 3-17

3-18

.4-Z .4-4 .5-l

.5-4 .5-6

.5-6

.5-II .5-14

.5-15 .5-16 .5-18

.5-21 .5-24 .5-25

.5-25

n b

I

na

12.75

(324)

I

INSTRUCTION MANUAL

Digltal

Multimeter

Models 172, 173

DIMENSIONS IN INCHES (MM)

FIGURE 1.

Dimensional Data.

I

INSTRUCTION MANUAL

Digllal Multimeter Model, 172, 173

SPECIFICATIONS

AA

INSTRUCTION MANUAL

Digital Mullimeler

Models 172.173

LEVEL POSITION - TILTBAIL AT FRONT

45' POSITION

r

HANGING POSITIOI;

SHELF POSITION

LEVEL POSITION - TILTBAIL AT REAR

vi

FIGURE 2.

Tilt Bail Positions.

AA

INSTRUCTION MANUAL

~

Digital Multimeter

Models 172. 173

GENERAL INFORMATION

I

SECTION I. GENERAL INFORMATION

l-l. INTRODUCTION. The Models

purpose measuring instruments, capable of measuring ac/dc voltage, ac/dc current, and

resistance. l-2. FEATURES

a. Automatic Ranging and Polarity

Manual Range Selection and Range Hold

b.

HI and LO Otxns Capability

C.

Line Operation

d. e. Optional Battery Operation, Model

Floating Capability to ?lbOOV peak

f.

Optional Isolated Digital Interface, Model

9.

l-3.

manual.

ized repair facility as given in OUT catalog.

WARRANTY INFORMATION.

If there is a need for service, contact your Keithley representative or author-

172

and

173

Digital Multimeters are wide-range, general-

1728.

1722

The warranty is stated on the inside front cover of the

l-4.

manual will be explained on a change notice sheet attached to the inside back cover of

the manual.

l-5. batterY pack which enables either line or battery operation. The Model 1728 has built-

in recharging circuitry. The Model 1728 is field-installed on the Model 172/173 chasis.

l-6. OPTIONAL MODEL

~~~~ digital output option. It provides isolated open-collector BCD outputs and control lines.

CHANGE NOTICE.

OPTIONAL MODEL

The A

read the associated

instrument. Damage to the instrument may occur if these precautions are ignored.

The

indicates those areas on the instrument which are potential shock hazards.

read the associated WARNING statements with regard to proper use and handling of the

instrument. Serious personal injury may result if these precautions are ignored.

symbol can be found in various places in this Instruction Manual.

t

Improvements or changes to the instrument not incorporated into the

1728

RECHARGEABLE BATTERY PACK. The Model

1722

DIGITAL INTERFACE.

CAUTION

IMPORTANT

statements with regard to proper use and handling of the

The model 1722 is a field-installable

1728

is an accessory

Carefully

This symbol

Carefully

cc

l-l

GENERAL INFORMATION

I

INSTRUCTION MANUAL

Digital Multimeter

Models 172.173

FUNCTION AND UNITS DISPLAY (my)

INPUT HI AND LO, UPPER PAlR (OHMS SOURCE. LOWER PAIR)

l-2

VOLTAGE FUNCTION (OUT) AHPERES FUNCTION (IN)

DC FUNCTION

AUTORANG, NG (OUT)

\\

LINE POWER

(LINE AND EAT MUST BE OUT FOR BATTERY CHARGE)

MANUAL RANGING (IN)

FIGURE 3.

Model 173 Front Panel

CC

INSTRUCTION MANUAL GENERAL INFORMATION

Dlgllal Multlmeler

Modelr 172,173

I

-3

I

GENERAL INFORMATION

INSTRUCTION MANUAL

Digllal Mullimeter

Models 172.173

I

ME&RE SELECTION (SE%%f,

II

172. 173 CONDENSED OPERATING INSTRUCTIONS

FUNCTION

,

, 3, 101.9999A

1 ( HlllOD

OVERRANGE:

FIRST DIGIT 3.

1

LP'.. .I.... '"".q /

REMAINING IIICITS

I

l-4

LINE

RAT.

SELFTEST(REARPANEL))

DC

IIAC 1 II n

l‘

TO OPEN INSTRUMENT:CAUTION-DISCONNECTLINE CORD.LOOSEN (4) SCREWS (THIS SIOE). HOLD INSTRUMENT TOGETHER AND TURN OVER.TltT TOP COVER DISCONNECT (2) CONNECTORS (CURRENT FUSE LINE AND SELF CHECK).

OUl.CHARGES DISCHARGED 1728 IN I6 HOURS, IN.OPERATESlNSTRUMENTfOR6HOUASFROM 1728BAT PACK,

IfINSTAtLEO.FRON7PANELLOBAT LlGHTCIIMFSflNIf RdTTlAY

1 OPERATlONWOULOCAUSEfAULTYREAOlNGS

CONNECT~NG~NPUTHITODCTERMINALW~~~CAIJSE~NSTRUMENT ~~~~~~~f'PROX.5VINOCVOLTSANOImAINOCAMPS.

CONNECTlNGlNPUTHITOACTERMINALWlttCAUSElNSTRUMENT

T""'*"""PROX.6VINACVOLTSANDl.2mAINACAMPS. ) CONNECTlNGlNPUTHITOQlERMINAtWIttCAUSElNSTRUMENT 1 TIJREADAPPROX.10kIN2TERMlNALOHMS.

IRICKLECHARGES

BACK

AND UP,

I

AB

INSTRUCTION MANUAL

Digital Mulllmeler

Models 172. 173

INITIAL PREPARATION

I

SECTION 2.

2-l. GENERAL. This section provides information needed for incoming inspection and preparation for use.

2-2.

trically before shipment.

which may have occurred during transit.

verify the electrical specifications, 2-3. PREPARATION FOR USE. The Model 172/173 is shipped ready-to-use.

can be powered from line voltage or from rechargeable nickel-cadmium batteries (when the

optional Model 1728 Rechargeable Battery Pack is installed).

third-wire grounded receptacles (NEMA 5-l5P). The permanently installed line cord is stored by wrapping the cord around the base of the instrument as shown in Figure 4.

INSPECTION. The Model 172/173 was carefully inspected both mechanically and elec-

Upon receiving the instrument, check for any obvious damages

Line Power.

a.

This instrument has an internal line power selector switch that must be set to

234V position for operation above 125 volts rms, 50-60 HZ.

The Model 172/173 has an attached three-wire line cord which mates with

INITIAL PREPARATION

Report any damages to the shipping agent. To

follow the procedures given in Section 6.

The instrument

CAUT I ON

1.

How to Set the Internal Line Voltage Switch (~601).

two position slide switch located on the main circuit board.

operation above I.25 volts the switch setting must be changed.

removed to gain access to the circuit board as described in MAINTENANCE section.

WARNING

Disconnect the line cord before removing the top cover of the instrument.

voltage is present at various points on the circuit board and represents a SHOCK

t

HAZARD.

NOTE

Other line voltage ranges are available when wiring modifications are made to

transformer T601 as shown on schematic 28067~1.

TABLE 2-l.

Summary of Standard and Optional Line Voltages

Standard

I05 to 125 V rms 90 - 105 v rills

210 to 250 v rms

Optional

195 - 210 v rms

Transformer wiring must be modified

>

The Model 172/173 has a

To set the switch for

The top cover must be

Line

2-l

.INITIAL PREPARATION

INSTRUCTION MANUAL

Digital Mullimeler

Models 172.173

SELF

FUSE

2-2

FIGURE 5.

Rear Panel Showing Current Fuse and Check Points

AA

STRUCTION MANUAL

.gllel MultImeter

~~Modelr 172, 173

INITIAL PREPARATION

2. Line Fuse Requirement. line-operated power supply. l/4 ampere for 117 volts operation or l/8 ampere for 234 volts.

A

t

A

Rechargeable Battery Pack must be installed. factory-installed (at the time the Model 172/173 is purchased).

Replace fuse with correct rating

How to Replace the Line Fuse.

3.

as shown in Figure 36 (page 6-10). circuit board as described in Section

Disconnect the line cord before removing the top cover of the instrument. voltage is present at various points on the circuit board and represent a SHOCK HAZARD.

The fuse installed on the rear panel of the Model 172/173 is used only for current range protection.

b. Battery Power.

This fuse is not a line voltage protection fuse.

To operate the Model 172/173 from batteries, the Model 1728

The Model 172/173 use a single line fuse to protect the

The fuse is a 3 AB or 3 AG, slow-blow type.

IMPORTANT

otherwise damage to the instrument could result.

The fuse is installed on the main circuit board

The top cover must be removed to gain access to the

6.

Use Keithley FU-17 for 117 V; FU-20 for 234V.

WARNING

CAUTION

-

The Model 1728 can be either field or

Replace

Line

with

NOTE

The Model 1728 Rechargeable Battery Pack can be installed by the user within the

Model 172/173 at any time.

installed,

1. How to Install the Model

with the Model 1728 are already installed in the battery pack. The battery pack in-

cludes 7 rechargeable “C” cells (l.ZV, 2 AMP Hr)

cells per pack). See Figure

Check the fuses on the Battery Pack.

a)

3AB or 3 AG, Slo-Blo types, Keithley Part No. FU-IO.

b) Check for proper installation of batteries in the Battery Pack.

battery cells are to be installed,

individual cells as shown in Figure 6.

c) To install the Battery Pack, faces up. screws are captive,

ment with the top cover facing up, gether. There are 2 connections between the top cover and the main circuit board which must be temporarily removed in order to free the top cover.

insulating spacers are in position on the circuit board as shown in Figure

the two S-wire connectors (J401, J402)

ing care to orient the connectors as shown. spacers with the pack oriented as shown in Figure 7. top cover to the circuit board. the bottom cover facing up and tighten down the four slotted-head screws.

the Model 1728 cannot be used simultaneously.

Loosen four slotted screws on the bottom cover as shown in Figure 4.

that is they cannot be removed completely.

Carefully remove the top cover to gain access to the printed circuit board.

However, if the Model 1722 Digital Output is already

1728

Rechargeable Battery Pack.

and two 19.2 volt packs (sixteen l.ZV-

The batteries furnished

6.

Three fuses are used.

be certain to observe the proper polarity of the

turn the instrument over so that the bottom cover

taking care to hold the top and bottom covers to-

Check to see that the four

into the mating receptacles (~602, P606) tak-

Place the Model 1728 in position on the

Replace the connectors from the

Replace the top cover.

Turn over the instrument with

All are I ampere,

If replacement

Turn over the instru-

7.

Plug

The

I B

2-3

INITIAL PREPARATION

INSTRUCTION MANUAL

Digilal Mullimeler

Models 172. 173

J402

a..-- - .~

FIGURE 6.

Model 1728 Rechargeable Battery Pack.

INSTRUCTION MANUAL Digital

Models 172.173

Multimeter

Disconnect the line cord on the instrument before the Battery Pack is installed, Line voltage is present at various places on the circuit board and is a SHOCK

t

HAZARD.

INITIAL PREPARATION

WARN I NG

I

CB

FIGURE

7.

Installation of Battery Pack.

2-5

INITIAL PREPARATION

TABLE 2-2.

Summary of Batteries Used in the Model 1728

INSTRUCTION MANUAL

Digilal Multimeler

Models

172.173

Description

I 2V “C” ccl I (; AMP-HR)

+19.2V pack

(l6-l.2V cells)

-19.2V pack (16-l.2V cells)

The Model 1728 is shipped from the factory in an uncharged condition.

A

the pack should be installed in the Model 172/173 and charged prior to use.

2.

How to Check Batteries.

The Model 172/173 has a built-in LO BAT indicator to permit easy determination

a)

of battery condition. bottom panel usually needed only for troubleshooting purposes (see Figure 4.).

b) The LO BAT indicator will be lighted when the Battery Pack goes belag normal

operating voltage.

to LINE or OFF to permit recharging of the Pack.

The test point may be checked at any time using the Model 172/173 or other mea-

C)

suring instrument. Then voltages are summarized in Table 2-3.

When the indicator turns on the Model 172/173 should be s,+jitched

Quantity

7

1

I

CAUTION

The Model 172/173 also has an individual test point on the

Voltage

8.4v

+19.2v

I

-19.2v BA-3 I

Keithley Part No.

BA- 30

I

BA-31

I

Therefore

IMPORTANT

The instrument must be operated in BAT mode in order to obtain a valid battery condition at test point “A”. This will ensure that the batteries are supplying power to the instrument.

in the LINE mode a different reading may be observed since the batteries are being

charged.

Test Point Range

I’A”

How to Charge the Batteries. The Model 1728 provides built-in recharging cir-

3.

cui try.

most rapid rate when the Model 172/173 is set to OFF.

2.5 hours per hour of discharge.

A

Overcharging the batteries will raise the internal temperature of the battery pack and may shorten the life of the batteries.

The Model 172/173 must be connected to line voltage.

If the voltage is measured when the Model 172/173 is operated

TABLE 2-3.

Summary of Battery Voltage Levels (BAT mode)

Acceptable Battery Levels

) Normal

ITV + t20.5V

+19.2

CAUT I ON

Recharge Battery

if Below Tested

ITV

Recharging occurs at the

Typically,

BT402

the recharge time is

2-6

CB

INSTRUCTION MANUAL

Digital Multimeter

Models 172. 173

SECTION 3. OPERATING INSTRUCTIONS

3- 1. GENERAL. This section provides information needed to operate the Model 172/173

for measurement of voltage, current and resistance.

OPERATING INSTRUCTIONS

3-2. chargeable nickel-cadmium batteries (when the Model 1728 is installed).

173 has a built-in line-voltage power supply and power cord.

age over four ranges from a minimum of 90 V rms to a maximum of 250 V rms. summarizes the line voltages permitted.

HOW TO SELECT POWER. The Model 172/173 may be powered from line voltage or re-

The Model l72/

NOTE

The accessory llodel 1726 Rechargeable Battery Pack may be ordered at the time of purchase of the Model 172/173 or may be purchased and field-installed at a later

time if so desired.

modifications need to be made to the Model 172/173 chassis.

a. How to Operate from Line Power. The Model 172/173 can be powered from line volt-

Set the internal line voltage switch to either ll7V or 234V.

I .

2. Plug the line cord into source of line power.

3. Depress

Power on will be indicated by a lighted display with one or more digits and measurement unit showing.

LINE

pushbutton.

The Model 1728 features plug-in wiring and, as a result, no

Table 3-l

NOTE

TABLE

How to Set Line Voltage

3-1.

_.

Range

Desired

go- 105V

lO5-125V 195-2lOV

210-25ov

b. How to Operate from Battery Power.

Install the Model 1728 Rechargeable Battery Pack.

I.

2. Depress If LO BAT indicator is lighted

hoz;s to provide fully charged opera;ion of the Model 172/173.

To charge the Model 1728, release both LINE and BAT pushbuttons and connect the

line cord to line power. depress LINE. The Model 172/173 will be useable for measurements although the battery charging rate is decreased considerably.

If the LO BAT indicator is not lighted in BAT mode,the model 172/173 may be

4.

used for measurements.

CB

BAT

pushbutton.

If it is desired to use the Model 172/173 immediately,

Switch

5601

ll7V

117v 234V 234V

the battery pack must be charged a minimum of 16

NOTE

Transformer Modification:‘:

yes ;‘;

NO

Yes 7:

NO

-; <<For these ranges the

leads must be rewired

(See Section 2, page

Z-3.)

3-l

3PERATING INSTRUCTIONS lNSTRUCTlON MANUAL

Digital Mullimeler

Models 172, 173

NOTE

The Model Model 1728 should be installed and charged prior to use. been charged for at least 16 hours, for at least 6 hours.

Button Depressed

LINE

BAT

NE I THER

LINE NOR BAT

I

3-3.

V/A,

rent fu#lct ions.

HOW TO SELECT FUNCTION.

and R

d. DC. This pushbutton must be used with

1728

is shipped from the factory in uncharged condition.

Summary of Ooeration in LINE and BAT Modes

Line Power Connected Line Power Connected Line Power Not Connected

1728

not installed 1728 installed

ON

OFF

Function is selected by means of four pushbuttons AC, DC,

Therefore the

After the Model 1728 has

the Model 172/173 can be powered continuously

TABLE

Battery trickle charged.

Batteryslowly discharged.

Battery charged at max-

imum rate.

3-2.

Condition of Instrument

ON

ON ON

OFF

V/A to

select either DC voltage or DC cur-

1728 installed

OFF

1.

DC Voltage. Depress DC

2. DC Current. Depress

b.

AC.

rent fe Ict ions.

I.

2. AC Current. Depress AC

t. V/A. This pushbutton selects either voltage V or current A. When

along with DC or AC, vide current sensing.

d. {I.

DC. AC,

depressed at a time. However, it is possible to have all pushbuttons out which

disconnects the input HI and LO terminals and no measurement can be made.

R indicator will be lighted in this instance.)

This pushbutton must be used with

AC Voltage. Depress AC

a shunt resistor is connected

Depress0 to measure resistance.

and Sl pushbuttons are interlocked so that only one pushbutton is

DC

Release Uepress

V/A

V/A to

Release Depress V/A

V/A

NOTE

select either AC voltage or AC cur-

across

the HI and LO terminals to

V/A is depressed,

pro-

(The

AA

INSTRUCTION MANUAL

I

Dlgllal Mulllmeler

I

Models

172. 173

OPERATING INSTRUCTIONS

FIGURE

3-4.

AmO/M4N pushbutton determines the ranging mode, where AUTO = fully automatic ranging.

range in accord with the following rules.

172/173

HOW TO SELECT RANGE.

a. AUTO.

I. When the display exceeds 29999 the Model 172/173 upranges (that is, it changes

to less sensitivity and the decimal point moves appropriately).

When the display reaches 02599 the Model 172/173 downranges (that is

2.

to greater sensitivity and the decimal point moves appropriately).

b. MAN. When depressed the range is placed in hold. The user can cause the Model

to uprange or downrange by using the UP RANGE and DN RANGE pushbuttons.

1. When DN RANGE is momentarily depressed the Model decade of sensitivity. Each time the pushbutton is depressed and released, one downrange will occur until most sensitive range is obtained.

2. When UP RANGE is momentarily depressed the model 172/173 will uprange one decade

of sensitivity. Each time the pushbutton is depressed and released, one uprange will

,occur until least sensitive range is obtained.

When released ,

8.

Front Panel Pushbutton Selection.

The Model 172/173 provides automatic or manual ranging.

the Model 172/173 automatically selects the appropriate

it changes

172/173

will downrange one

The

I

AA

3-3

OPERATING INSTRUCTIONS

INSTRUCTION MANUAL

Digital Multimeter

Models 172.173

3-S.

ranges: 0.3V, 3V,

,law.O display). The maximum display is 29999. When the display exceeds

29999, a 3 remains lighted,

1199.9 volts on the highest range.

HOW TO MEASURE VOLTAGE.

3OV, 300V

Maximum input voltage depends on the range selected. allowable continous input for each range on AC and DC. Do not exceed these voltaqes or damage to the instrument will occur.

The Model

I.

Set to DC Volts.

2.

Set to AUTO.

The Model

and 12OOV DC (1000VAC).

Maximum Allowable Continuous Input

172/173

but all other digits are blanked. The display blinks above

172/173

CAUTION

TABLE

detects dc voltages from +I0 microvolts/digit to

measures ac and dc voltage in five

Table

3-3

gives the maximum

3-3.

Connect the Signal to be measured between HI and LO terminals.

3.

are designed to accept banana style plugs. Such as Keithley part no. BG-5 or accessory test leads such as Model I681 Clip-On Test Leads.)

4.

Observe the displayed digits, polarity sign, decimal point location, and measure-

ment unit (mV or V).

b. AC Voltage. The Model l72/173 detects ac voltages from IO microvolts rms to 1000

volts (1000.0 display). The maximum display is 29999.

a 3 remains lighted, but all other digits are blanked.

volts on the highest range.

I.

Set

to AC Volts. (The AC indicator should be lighted.)

2. Set to AUTO.

Connect

3.

are designed to accept banana style plugs, such as Keithley part no. BG-5 or accessory test leads such as t+odel 1681 Clip-On Test Leads.)

4.

Observe the displayed digits, decimal point location, and measurement unit (mV

or V).

the signals to be measured between HI and LO terminals. (The terminals

If no polarity sign is indicated,

a positive polarity is implied.

When the display exceeds 29933,

The display blinks above 999.9

(The terminals

CB

INSTRUCTION MANUAL

Dlgltal MultImeter

Models 172.173

OPERATING INSTRUCTIONS

3-6.

in two ranges:

DMM is capable of displaying 2.9999A.

A

.3”pZl-l?S.

MAN mode it is possible to select 30A, 300A & 3000A Ranges,but 2A Max is sti)) the limit.

tobj amperes rms. The maximum display is 29999.

remains lighted, but all other digits are blanked.

How TO MEASURE CURRENT. (MODEL

0.3A,

The Model 172 is protected by a 2 ampere fuse on all ranges. a replacement Keithley Part No.

holder. (See Figure 5.)

DC Current.

a.

When the input exceeds 2 amperes, the current fuse will blow. When using the

Set to DC Amperes.

I .

Set to AUTO.

2.

Connect the signal to be measured at the HI terminal.

3.

Observe the displayed digits, polarity sign, decimal point location, and measure-

4.

ment unit (LIA, mA, or A).

implied.

AC Current.

Set to AC Amperes. (The AC indicator should be lighted.)

I .

and ZA.

The Model 172 detects dc currents from ?I0 microamperes/digit to 22

The Model

The current is limited by the current fuse even though the

If no polarity sign is indicated, a positive polarity is

173

172

ONLY).

CAUTION

FU-13 should be installed in the rear panel fuse

DMM detects ac currents from 10 nanoamperes rms/digit

The Model

When the display exceeds 29999, a

172

measures ac and dc current

If the fuse is blown,

3

Set to Auto.

2.

Connect the signal to be measured at the HI terminal.

3.

Observe the displayed digits, decimal point location, and measurement unit (AC

4.

PA, AC ma, or AC A).

- L

OAC .,,,A

:I /Ill ‘ql 1:; lq on

.

mV

0,”

okn OWU-I

CB

FIGURE

Typical Model 172 Current Display (DCmAJ.

9.

3-5

OPERATING INSTRUCTIONS

3-7. HOW TO MEASURE CURRENT. (MODEL 173 ONLY.) The Model 173 measures ac and

dc current in five ranges:

0.3mA, 3mA, 30mA, 0.3A, and 3A. CAUTION

INSTRUCTION MANUAL

Digital Multimeter

Models 172.173

The Model I73 DMM is protected by a 3 ampere fuse on all ranges. blown, a replacement Keithley Part No. fuse holder. (See Figure 5.)

a.

DC Current.

amperes.

lighted, but all other digits are blanked.

1. Set to DC Amperes.

2.

3.

4.

ment unit ( A, mA, or A).

implied,

b. AC Current.

3 amperes rms. The maximum display is

:o

-emains lighted, but all other digits are blanked. I . Set to AC Amperes. (The AC indicator should be lighted.)

2.

3.

The maximum display is

Set to AUTO. Connect the signal to be measured at the HI terminal. Observe the displayed digits, polarity sign, decimal point location, and measure-

Set to AUTO. Connect the signal to be measured at the HI terminal.

The Model 173 DMM detects dc currents from ?I0 nanoamperes to 13

29999.

If no polarity sign is indicated, a positive polarity is

The Model 173 DMM detects ac currents from IO nanoamperes

FU-2 should be installed in the rear panel

When the display exceeds

29999.

When the display exceeds 29999, a 3

29999,

If the fuse is

a 3 remains

rms/digit

4.

Observe the displayed digits, decimal point location, and measurement unit

A, AC ma, or AC A).

FIGURE

.AC OmV OV

on 0ki-i OMa

o,M .mA OA

Typical Model 173 Current Display (ACmA).

10.

(AC,

3-6

CB

INSTRUCTION MANUAL

Dlgltal MulIimeler Models 172. 173

OPERATING INSTRUCTIONS

3-8.

ohms/d iq i t to

29999, a 3 remains lighted, but all other digits are blanked.

age developed

173 measures to 300 megohms in HI mode. is not used.

age developed across the resistance under test at full range is 300 millivolts. Model 172/173 measures to 30 megohms in LO mode. terminals is not used.

HOW TO MEASURE RESISTANCE.

300

megohms.

a.

HI Ohms Measurement.

~CTOSS

I .

Set to HI Ohms

2. Set to 2 WIRE.

When the.Ilodcl 172/173 is set to 2 WIRE,

are not cnnncctcd. are used as “voltage sensing” terminals. mation.

Set to AUTO.

3.

Connect the resistance under test between the upper set of HI and LO terminals.

4.

Observe the displayed digits, decimal point location, and meaSurement unit (c,

5.

KR, or MC).

b. LO Ohms Measurement.

Set to LO Ohms.

I.

the resistance under test at full range js 3 volts,

The maximum display is

When

When set to 4 WIRE,

When the HI/LO pushbutton is released (set to LO), the volt-

The Model

the

HI/LO pushbutton is released (set to HI), the Volt-

172/173

For the 2 wire method the lower set of terminals

NOTE

the Iov~er set of HI and LO in;,ut terr!iiials

the higher set of HI il~~(l LO input terr;i~lals

See Section 3-S for more detailed infor-

measures resistance fro-, 10 milli-

23939.

For the 2 wire method the lower set of

When the display erceeds

The Model 172/

The

2.

Set to

Set to AUTO.

3.

Connect the resistance under test between the upper set of HI and LO terminals

4.

Observe the displayed digits, decimal point location, and measurement unit (:.,

5.

Kc!, or MR)

2

WIRE.

This illustration is typical of a Z-terminal ohmmeter design.

ifF-~/--qiy=j OHMMETER

When measuring resistance less than 1OOOohms it may be necessary

to use the 4-wire mode to eliminate the measuring error of the test leads.

For example a pair of IOft leads made from I8 AWG copper wire has 0.14 ohms resistance.

iB

FIGURE 11.

Typical 2 WIRE Resistance Measurement.

3-7

I

OPERATING INSTRUCTIONS

INSTRUCTION MANUAL

Dlgilal Multimeler

Models 172. 173

3-Y.

FURTHER MEASUREHENT CONS I OERATI ONS.

a. DC Voltage Measurements.

1. Overloads. When the display exceeds ?lZOO.OV DC all digits blink to indicate

an overload condition.

2.

Input Resistance.

IO MC? on the 3OV, 3OOV, and 3000V ranges.

considered when evaluating total accuracy of measurement.

Accuracy.

3.

a % df range.

would be + (0.03 mV + 0.01 mV) or +0.04 mV. Measurements from relatively high source.

resistances could cause an additional reading error. loading can be determined by the following relationship:

Self-Check Feature.

4.

functional check of the Model 172/173 in DC Volts. To use this feature, connect.the

input HI terminal to the rear panel white terminal. Verify a display of approximately

5 volts dc.To check dc current,

b. AC Voltage Measurements

1. Overloads. When the display exceeds 1000.0 V AC (t-m) all digits blink to in-

dicate an overload condition.

The Model 172/i73 accuracy is specified in terms of 4 of reading and

For a full range reading of 299.99 mV DC the accuracy of measurement

The input resistance is 1,000 HR on the 0.3V and 3V ranges;

The effects of circuit loading should be

(See Accuracy.)

The amount of error due to

% error = 100 x Rs i (Rs + RI)

where Rs

The Model 172/173 has a rear panel Voltage test point for

depress V/A andverify a display of 1 mA.

= source resistance in ohms

RI -

input resistance of Model 172/173 in ohms

2. Input Impedance. The input impedance is 2 megohms shunted by less than 50

picofarads. total accuracy of measurement.

AC-to-DC Conversion.

3. calibrated in terms of the root-mean-square (rms) of a sine wave. exact for sinusoidal waveforms in the specified frequency range.

4. Frequency Response.

mum and maximum frequencies which accuracy is valid.

Accuracy.

5. and a % of range. additional reading error.

the following relationship:

6. Self-Check Feature.

functional check of the Model 172/173 in AC Volts. To use this feature, connect the HI terminal to the rear panel red terminal. Verify a display of approximately 6 volts ac. To check ac current, depress V/A and

verify a display of approximately 1.2 mA.

The effects of circuit loading should be considered when evaluating the

(See Accuracy. )

The Model 172/173 operates as an average-reading voltmeter,

The calibration is

The frequency range given in the specifications is the mini-

The Model 172/173 accuracy is specified in terms of a % of reading

Measurements from relatively high source impedance could cause an

The amount of error due to loading can be determined by

% error = 100 x zs fsZin

where Zs = source impedance

Zin = effective input impedance of Model 172/173

The Model 172/172 has a rear panel Voltage test point for

Connect the line cord to line voltage.

AA

1 INSTRUCTION MANUAL

Digital MultImeter

Models 172, 173

c.

Current Measurements.

Overloads.

I .

Shunt Resistance.

2.

input terminals at full range.

OPERATING INSTRUCTIONS

Fuses are as follows: Model 172: 2A Model 173: 3A

The Model 173 develops approximately 300 millivolts across the

The 172 has 1.3 R on all ranges.

For example,

in a voltage drop of 0.3 x 1.3 =

3. Accuracy. The Model 172/173 accuracy is specified in terms of a % of reading and a pl of range. An additional reading error should be considered if the source resistance is not greater than 1000 times the shunt resistor. be determined by the following relationship:

d. Resistance Measurements.

Maximum Allowable Voltage Input. The maximum input should not exceed 250V rms

I.

sine wave or t250V dc.

Polarity of Ohms. The Model 172/173 provides a positive voltage at the HI

2.

terminal.

3. Maximum Open-Circuit Voltage.

HI or LO ohms,

on the 300 milli-ampere range the shunt resistor is 1.3 ohm, which results

390

millivolts at full range.

The amount of error can

where Rin = shunt resistance of the Model 172/173

Rs = source resistance.

When the HI and LO terminals are open in either

the maximum voltage developed between HI and LO is +5 volts.

This illustration is typical of a 4-terminal measuring technique using a separate Voltmeter and Current Source. combines these features.

The Model 172/173

“HI” LEADS

“LOW” LEADS

When using the 4-WIRE method, connect one pair of

“current” leads to n SOURCE input.

second pair of “voltage” leads to HI and LO.

Then set to 4 WIRE.

Care should be taken to connect "current" leads and “voltage” leads properly. The LO terminal1 and R Source low must always connect to the same

side of the unknown resistance.

FIGURE 12. Typical 4 WIRE Resistance Measurement

RSOURCE HIGH

R SOURCE LOW

Connect a

CB

3-v

OPERATING INSTRUCTIONS

Four-terminal Measurements.

4.

terminals

are the current carrying terminals while the upper terminals are the voltage sensing

terminals. This arrangementeliminatesthe error due to voltage drop across the current-carrying leads.

Semiconductor Diode and Transistor Testing. The Model 172/173 can be used to

5.

test diodes and transistors to determine the relative condition of the device.

semiconductor diodes, the voltage applied must be sufficient to cause conduction in the

forward direction.

I milliampere.

nections should be made as shown in Figure 13 to cause forward conduction of diodes. Since the maximum current is available on the 3 K:. range, depress AUTO/HAN (Set to

MAN) and manually range to the 3 KI: range (down-range!.

to the DMM ohmmeter source.

The “HI OHMS” mode provides a voltage up to 3 volts at a current “pto

Since the HI terminal is positive with respect to LO terminal, con-

The II-WIRE mode connects the lower set of R SOURCE

As shown in Figure I2 the lower terminals

INSTRUCTION MANUAL

Digital Multimeler

Models 172.173

For

Self-Check Feature.

6.

functional check of the Model 172/173 in OHMS. To use this feature, place the DMM in OHMS and 2 WIRE mode. of approximately IO kilohms.

The Model 1;12/173 has a rear panel ohms test point for

Connect the HI terminal to the blue terminal.

HI

i

Verify a display

TYPICAL DIODE

FIGURE 13.

TYPICAL PNP TRANSISTOR

Semiconductor Diode and Transistor Testing.

AA

INSTRUCTION MANUAL

Dlgllsl Models 172, 173

Multimeter

OPERATING INSTRUCTIONS

3-10.

ground at potentials of up to ?14OOV. ground is specified at IOOOMR, or IO'ii (shunted by 300pF).

resistance from LO to CND is two decades greater than 10qR

excellent isolation,

loading (from LO to GND) of a floating source.

173

accounts for the high common-mode rejection ratio of the Model 172/173. Even with the

"HI" terminal driven and a source resistance of lkR, 1000 VDC (from HI to GND) will

produce typically only IOuV DC error. the ratio of the source resistance to the "isolation" resistance (See Figure 14).

The "isol ation" capacitance frwn LO to GND is important when AC cornnon-mode signals are present.

of

driven and a source impedance of lkn, a IOOOV p-p, 60 Hz, common-mode signal will

produce a voltage of only IOOmV p-p across the input terminals. p-p signal will be further rejected by the input filter and A-D converter so that the total rejection at the digital display is at least 120 dB (HI d

impedance).

the

a need for even greater isolation from LO to power line ground, or where there is a need

to float at potentials greater than 1400 volts above power line ground the Model

Battery Pack should be used.

HOkl TO USE MODEL

will require, typically, only IOnA from the source.

, - lOOOV -

to"n

In the Model

60~2,

Model 1721173 LO terminal is driven, rather than the HI terminal.

300 picofarads has a reactance of approximately IOHR. With the HI terminal

For DC voltage measurements, rejection is much greater than specified when

172/173

operating the Model

10-sA

172/173

OFF-GROUND.

this capacitance is specified at 300 pF. At a frequency

The "LO" terminal can be operated off

Isolation from the

172/173

This error voltage is determined directly from

V

across Ik = I x Iki: = IO-' x IO3 = 1O;VDC

off ground results in very little

At IOOOV above ground, the Model 172/

"LO" terminal to power line

Ty ically, the isolation

(10

PI n).

The excellent isolation also

Because of this

This IOOmV

riven, IkT. source

Where there is

1728

I

(7ERNAL :"IIQCF

lKI!

SOURCI

SlSTANCL

,

FIGURE 14.

1

II:PlJl I

l+L&

1

- L----------r

-

GROiND

Use

of

Multimeter Off Ground.

r-------------I

I I

*

DIGllAL MULlIMEliF.

10l'n 1s

I

TYPlCAL

~OLAllON

RE SISTANCE

,

I I I

I I I I

I I

I

OPERATING INSTRUCTIONS

I

INSTRUCTION MANUAL

Digital Mullimeler

Models 172. 173

3-11. How

a. Model 1600 High Voltage Probe. range. The input resistance on the 30 volt range is IO megohms so that no shunt resistor is needed. The Model 1682 has a 1OOO:l division ratio. instructions furnished with the Model 1600 probeabove 30kV, switch to the 300V range.

The alligator clip (ground) must be connected to the source low so that high volt-

A

Model

volt range. The Model

age is not applied between low and ground.

occur if the alligator clip is not connected.

b. Model 1682 RF Probe. Set the Model 172/173 to DC volts and 30 volt range. 100 MHz.

For use on the should be used since the Model 172/173 input resistance is >lOOO megohms on the 3 ‘volt and 0.3 volt ranges.

Model

C. rms input. Review the instructions furnished with the Hodel 1685 to achieve best pos-

sible accuracy.

TO USE OPTIONAL PP!IBFS AND SHUNTS.

Set the Model 172/173 to DC volts and 30 volt

For maximum safety review the

CAUTION

Severe damaqe to the instrument will

1682

has a IVdc output corresponding to I V rms input over the range 100 kHz to

IMPORTANT

3

volt range the banana plug adapter (with IO megohm resistor)

1685

Clamp-On AC Current Probe.

1685

provides a 0.1 volt rms output corresponding to a I ampere

Set the Model

172/173

to AC volts and 0.3

The

d. Model 1651 Current Shunt. Set the Model 172/173 to AC or DC volts (as appropriate) and 0.3 volt range. Connect the voltage leads to the Model 172/173 input terminals. Connect separate leads (not furnished) between the source and the Model 1651 hex-head

bolts. The Model 1651 shunt resistance is 0.001 ohm which produces a sensitivity of I millivolt per ampere.

AA

INSTRUCTION MANUAL

Dlgllsl Multimeter

Models 172, 173

OPERATING INSTRUCTIONS

3-12.

a.

control lines.

This accessory is available either "factory installed" or "field-installable".

Model 1722 consists of a two-layer circuit with card-edge and mating output connectors.

b.

screws are captive, that is, they cannot be removed completely.

the top and bottom covers together.

There are 2 connections between the top cover and the main circuit board which must be temporarily removed in order to free the top cover (see Figure 40.)

disconnect connectors from the mother board.

HOW TO USE THE MODEL 1722 DIGITAL INTERFACE.

General.

installation.

Disconnect the Model 1?2/173 line cord from line voltage,

I.

Turn the instrument over so that the bottom cover faces up.

2. Loosen four slotted screws on the bottom cover as shown in Figure 4.

3.

Turn over the instrument with the top cover facing up, taking care to hold

4.

Carefully remove the top cover to gain access to the printed circuit board.

5.

Remove the Model 1728 Rechargeable Battery Pack.(if installed).

6.

THE Model 1722 provides binary coded decimal outputs (8421) and range Outputs are open-collector positive true unless otherwise specified.

NOTE

The

Carefully

The Models 1722 and 1728 cannot be installed on the Model 172/173 chassis

at the same time.

Check to see that the four insulating spacersare in position on the circuit

7.

board as shown in Figure 16.

Place the Model 1722 on the spacers as shown in Figure

8.

Lift up the Model 1722 slightly to gain access to the Model 172/173 mother

9.

board, and plug in connectors JlOO3, JlOO2, and JIOOI (in order given).

10.

transformer TIOI.

11.

12.

13.

pi:j

and PI101 (26-pin).

cardedge connectors as shown in Table

I

Connect ground return wire from the Model 1722 to the extra lug on

Replace the connections to the top cover. Reinstall the top cover. Turn the instrument over and tighten the four screws.

Connector Terminations.

The Model

Ribbon cable style of mating connectors may be used with these

I722

uses two card-edge connectors ~1006 (40-

3-5.

PllOl

TABLE

Sumnary of Mating Connectors

Manufacturer

3M

3-5.

Crimped Ribbon-Cable Style

3462-0000

16.

P1006

3M

3464-0000

3-13

OPERATING INSTRUCTIONS

INSTRUCTION MANUAL

Digital Multimeter

Models 172,173

J1002

J1003

AA

INSTRUCTION MANUAL

Dlgltsl Mullimeler

Mode18 172,173

OPERATING INSTRUCTIONS

CB

bllr”Kt IO.

PI01

Installation of Model

.~

3 SPACER

1’ c

\, \\

'1 'J

3k-T

1722.

i (4 Places)

‘\

3-15

1 OPERATING INSTRUCTIONS

Pin No.

1

:

4 6

TABLE 3-b.

Sumnary of Digital Output at ~1006 I I

Signal

CASE GND COMMON COMMON COMMON

Pin No.

21

22 23

24 25

I

PRINTER HOLD

E

-. .-T

26

27

28

INSTRUCTION MANUAL

Digital Multimeter

Models 172,173

Signal

104-2 103-l

104-l

103-l

lo*-8 101-8 IO’-4 101-4

10 II I

-15

16 OHMS

.t;

19 104-4

20 103-4

Summarv of Remote Commands at PI101

Pin No.

Command CASE GND"

COMMON COMMON

AUTORANGED STROBE TRIGGER MODE

AUTOMOOE STROBE

HOLD OVERFLOW STROBE

~___

LOAD RANGE FLAG/FLAG STROBE

Rl

FUNCTION STROBE R2

VOLTS

R4

AMPS R2

AC

Rl

lo”-8 103-8

TABLE

3-7.

Pin No.

14

15 16

17 18

I9

20 21 22 23

24 2

OVERFLOW POLARITY

Comnand RANGE STROBE

R4 POLARITY STROBE R8 IO4 STROBE

TRIGGER

I03 StROBE

FLAG RESET IO2 STROBE

TR GGER MODE

I

10 STROBE

AUTORANGED

loo STROBE

DISABLE

3-16

CB

INSTRUCTION MANUAL

Digllal Multimeter Models 172.173

OPERATING INSTRUCTIONS

r_--__-_--------------

2 4 6 61@1?14161820222426

’

/ PIIOI

I

I’

I 3 5 7 3 lll3151719212325

; 1 ’ m : : : ; : : :1

-I

I I

L--------------------J

I 2 4 6 e 1012i41618202~24262e303234~~384; I , PI006 I’

: ----- 1 ------------------ 3 5 7 9 111315 II11I~IIIIIIi~ 1719212>252729313335373~ ______

FIGURE 17.

’ ’ I ’ 11111111111111

Connector Pin Identification for pt006 and PIIOI.

1

FIGURE 18.

How to Select Vext Using Internal Jumper.

d.

internal or external voltage references and internal pull-up resistors. (See Figure 16.)

Jumper A. When this jumper is installed,

I.

the external reference Vext (pin 8, ~1006).

2. Jumper 8. When this jumper is installed,

the internal reference (+5V).

Jumper C. When this jumper is installed,

3.

reference. reference is rated at 40 mA maximum.

The pull-up resistors are not connected in this instance.

Card-Edge Connectors (Model 1727 Cable Set).

The Model 1722 may be wired for use with

the pull-up resistors are connected to

Vext is connected to internal +5V

The +5 volt

3PERATING INSTRUCTIONS

INSTRUCTION MANUAL

Digital Mullimeler

Models 172. 173

1 3-18

FIGURE 13.

Location

of

Jumpers and Pull-Ups on Model 1722.

AA

INSTRUCTION MANUAL

Digltal Multimeler Models

r

172,173

Name

OPERATING INSTRUCTIONS

TABLE 3-8.

Digital Output Lines Grouped By Function

FUNCTION STROBE

-AUTORANGE

TRIGGER MODE

LOAD RANGE

FLAG RESET

FLAG/FLAG STROBE

CB

3-19

QPERATING INSTRUCTIONS

I

TABLE 3-g.

General Characteristics of Model 1722 Digital Interface.

INSTRUCTION MANUAL

Digital Mullimeler

I

DIGITAL OUTPUTS:

Logic: BCD (8421) Open-collector positive true unless otherwise specified. Data: 4 full digits, I partial digit (0, I, 2, 3)

1 Function: 4-bit code (n, AC VOLTS, AMPS) 1 Polarity: HIGH : +.

Overflow: : Autorange: ! Automode:

FLAG (m): HIGH (logic “0” : no output change occuring. , Logic Levels: HIGH f open collector to output LO. LOW 5 closure to output LO. / device (2N5134) greater than 20V breakdown,

pull-up resistors may be installed on these open collector outputs. value is recommended when using internal

OUTPUT TIMING: Data is updated typically every 320 msec (non-trigger mode).

I .

time strobe is active. The FLAG will go low (Logic “0”) typically 2 msec before update and

go high typically 100 usec after update.

long as the flag is high.

“0”) until the end ~of the next data update.

REMOTE CONTROLS:

1 Strobe: Strobe lines permit word serializing in 4-bit increments or multiples thereof.

HIGH inhibits controlled output lines from conduction, LOW enables conduction.

Range In: 4-bit exponential code. L& Range: Low enables remote ranging as set by Range code.

Hold:

( Printer Hold:

I

Trigger Mode:

, Trigger Mode Disable: LOW disables TRIGGER.

Trigger: Flag Reset: Low sets FLAG (FLAG) Control Logic Levels G Source Requirements: HIGH 3 either an open circuit or a

I

ISOLATION: All digital outputs and remote controls are isolated from 172/173 analog

input by 10’ 0 and 5OOpF, 1200 VDC, 1OOOV rms AC maximum. All digital outputs and remote controls are isolated from chassis ground by I06 R and 0.0l~F; 250V

is

conversions) . printer.

voltage between +2.4V and 5V referred to output LO. LOW : closure to outcut LO

within 0.8V while sinking +T.6 milliamperes (ITTL load). and LOAD RANGE code bits are all HIGH (inactive) the 172/173 is under front panel

control. panel setting once activated.

LOW s >

LOW s range change.

HIGH s autorange mode.

typically 1.2 msec. Data will appear at an output only if its respective

LOW inhibits display update,

Same as hold but grouped with outputs for convenience in interfacing LOW enables TRIGGER control.

LOW to HIGH transition initiates a new A/D conversion.

These REMOTE CONTROL inputs have priority and will override any front

23333.

<0.5V at 5mA sink (3TTL loads).

5

volt power supply.

Data can be expected to be unchanging so

If FLAG RESET is activated,

output update and autorange (A/D continues

t0

LOW (HIGH),

and exponential range code.

4.7K minimum

the FLAG will reset (go to Logic

When TRIGGER MODE, HE

Models 172.173

Output

Internal

Update

rms

maximum.

I

I 1

I

AA

INSTRUCTION MANUAL

DiQllEd

MUttbW!W

Model8 172.173

Detailed Explanation of Model 1722.

e.

TRIGGER MODE AND TRIGGER: When TRIGGER MODE is active (Low), output data and dis-

(See schematic 28248E)

OPERATING INSTRUCTIONS

play will not be updated. Conversion starts within 1.6 milliseconds after TRIGGER.

Integration starts 120 milliseconds after start of

conversion.

TRIGGER MODE enables TRIGGER.

HOLD:

LOAD RANGE :

REMOTE CONTROLS :

If either HOLD or PRINTER HOLD is low the output data

and the display wi 11 not be updated and the FLAG wi I1

stay at HIGH (unless reset by FLAG RESET).

When LOAD RANGE is low the 172/173 will go to the range as set by the RANGE IN code (Table 3-10) at the beginn-

ing of the next conversion.

held low each instrument will remain on its programed

range overriding front panel UPRANGE, DOWNRANGE and

AUTORANGE.

of table3-IO will result in the nearest valid range

to that programmed.

range change. be held (not updated) during TRIGGER MODE or HOLD. Referring to timing schematic 28249~,it is possible to just miss a REMOTE CONTROL update prior to data output.

This can be misleading,especially in the case of HOLD. A HOLD just missed (unknown to the user), just before

data begins to change,could result in erroneous data. To check if this occurred, it is suggested that the FLAG be examined no sooner than 10 usec after activation

of the HOLD bit. If flag is low wait until it goes to HIGH before expecting the HOLD bit to have been accepted. Other REMOTE CONTROL bits such as TRIGGER MODE and TRIGGER, LOAD RANGE and the RANGE IN code can be kept active for longer than an output data update time, i.e.

>3.2 msec to insure proper REMOTE CONTROL acceptance.

RANGE IN codes programmed outside the 1 imi ts

LOAD RANGE will always cause a DMM

However, the display and output data will

As long as LOAD RANGE is

A6

TRIGGER MODE DISABLE: When in TRIGGER MODE and triggering into an autoranging

(See Schematic 28249D)

condition, normal operation will give an output for each

range encountered during the autorange.

this is undesirable the AUTORANGED output bit can be

tied to TRIGGER MODE DISABLE and FLAG RESET. This will

prevent the FLAG from being set and ignore further

triggering until the final range is reached.

However, if

3-21

OPERATING INSTRUCTIONS

INSTRUCTION MANUAL

Digital Multimeter

Models 172.173

v

ext:

LINE GROUND:

GROUNDS: 4 pins for digital outputs, 2 pins for remote control.

CONNECTORS: One ho-pin card edge and one 26-pin card edge.

ENVIRONMENT :

installed in a 172/173: Operating 0°C to 55°C. humidity 80% @ 35’C.

Internal jumpers (user installedjselect internal or

external voltage reference for user-installed pullup

resistors for all open-collector outputs, or applies

internal +5V to v (maximum external current load on internal +5v is

mended is 4.7K.

One pin on each output connector.

Storage:

-25. to +65OC

GiGA).

Minimum pull-up resistor recom-

Modifications to Model 172/173 Specifications. When operating a 172/173 with a

f.

lj’2Z in TRIGGER MODE, only the accuracy specifications for the top two ohms ranges change

as follows:

HI n 3OOMQ Range: HI R 30tln Range:

LO fi 30M Range: From 0.5% of reading to 1% of reading. LO n 3H Range:

Also when operating in TRIGGER MODE, repeatability of readings may be up to:

0.5% on 300MQ Hi $I and 3OMQ Lo R ranges, and

0.05% on 30Mn Hi R and 3MQ Lo n ranges.

Accuracy of all other ohms ranges and all other functions is not affected by the Model

1722.when operating in TRIGGER MODE.

3-22

From 1% of reading to 1.5% of reading.

From

From 0.1% of reading to 0.15% of reading.

0.15% of reading to 0.2% of reading.

AB

I

INSTRUCTION MANUAL Dlgllsl

Models 172. 173

Multimeter

OPERATING INSTRUCTIONS

TABLE 3-10

FUNCTION

DC VOLTS

AC VOLTS

DC AMPS

MODEL

OUTPUT FUNCTION CODE (1)

VAACQ

100 0

101 0

I 0 0 oC2)

1722

RANGE t FUNCTION COOING FOR MODEL

RANGE

300 mv

3.ov

30 v

300 v

1200 v

300 mv

3: “v

300 v

1000 v

300 mA

2 A

OUTPUT RANGE CODE (I)

%I R4 R2 Rl

0 IO I 0 110 0 Ill

I 0 0 0 IO 0 I

0 IO I 0 1 1 0 0 ill

I 0 0 0 IO 0 I

0 IO I 0110

(EXP)

17-i’

III1 IO IO

IO 0 I

Ill1 AUTORANGE IO IO IO 0 l IO 0 0

0 I I I

Ill1 AUTORANGE !

AUTORANGE

I I

4C AMPS

LOW n

il R

(I) Coding in this table is defined to be HIGH (POSITIVE) TRUE. "I" = HIGH and "0" =

LOW.

(2) Function code for Model 172 current is volts.

(3)

Note that except for AUTORANGE CODE, PUT RANGE CODE, i.e. the INPUT RANGE CODE is the LOW TRUE BCO code of (EXP).

101 oC2)

300 mA

2 A

000 1

300 R

3

I-

001 0

kn

30

kn

300 kfi

3 MI2

30 MC

3 kn

30 ka

300 kn

3 m

30

nfi

I

Refer to output and remote control logic levels for definitions of HIGH & LOW.

300 MR

0 IO I 0 II0

0 010 0 0 II 0 IO 0 0 IO I 0 110 0 Ill

0 0 II 0 I 0 0 0 IO 1 0 I I 0 0 Ill

IO 0 0

INPUT t RANGE CODE is the compliment of the OUT-

IO IO

I 0 0 1 Ill 1

II0 1 I IO 0 IO I1 IO IO IO 0 1 I 0 0 0

Ill1 AUTORANGE I I 0 0 IO II

IO IO

IO 0 I 10 0 0 0 Ill

AUTORANGE

AA

3-23

OPERATING INSTRUCTIONS

MODEL 1722 RANGE G FUNCTION CODING FOR MODEL I73

INSTRUCTION MANUAL

Digital Multimeter

Models 172. 173

TABLE 3-11

(Same as Table 3-loexcept as follows)

AC AMPS

OUTPUT FUNCTION CODE (I)

VAACR

010

011

0

RANGE

300 PA

3 mA

30 mA

300 mA

3 A

VA

300

3 mA

30 mA

mA

300

3 A

OUTPUT RANGE CODE (I)

R8 R4 R2 R~

0 IO I 0 II0 01 I I

1000 ll IO 0 I

9

0 I 0 1 2 0110 0 Ill

1 D 0 0 87 1001,g

(EXP)

INPUT RANGE CODE (1) (3)

R8 R4 R2 R~

I II 1 IO 10 IO 0 I

IO 0 0

0 Ill 0 II0

Ill1

1 0 1 0

10 0 I

IO 0 0

I

AUTORANGE

'-24

AA

INSTRUCTION MANUAL

Dlgltal Multimeter

Models 172.173

OPERATING INSTRUCTIONS

3-13.

decrease in accuracy. This decrease in accuracy is due toself heatingand the temperature coefficient of the resistors that are used in these currents. acy will not exceed those values that are listed in the specification sheet. prolonged operation at the high currents 3 amperes on the Model 173) may give temporary zero shifts because of the thermals which are generated due to the self heating of the devices.

listed down to 1% of range.

accuracy. This does not occur immediately at the 1% level, but gradually as the level

is decreased, because the zero of the ac/dc converter is not very well defined. It has

to overcome the threshhold level of various semiconductor devices (a MDS FET and diode). As a result there will typically be a IO digit offset at zero even with the input shorted on the 300 millivolt range and on the 30 volt range. The 30 volt range offset will be

somewhat smaller because the noise will be somewhat less. For best accuracy use the

Model 172/173 on whatever range gives the largest reading. Autoranging will accomplish

this automatically.

3-14.

eries used in the

once a cell is fully charged, the energy fed to the cell is converted to heat, which

increases the temperature of the cell. ed periods of time’(weeks), this may cause cell degradation. the 1728 not be overcharged for extended periods to maximize useful battery life. Trickle

charging should have no effect on useful battery life. hibit a memory effect.

short periods of time (I or 2 hours) the 1728 may not be able to provide the full operat-

ing time of 6 hours.

COMMENTS RELATIVE TO THE MODEL

Below 1% of range an additional IO digits is added to the

MODEL

1728

OPERATING TIPS.

1728

claim that their cells can be charged at a C/IO rate indefinitely,

If the 1728 is only used to operate the instrument for relatively

172/173

Although the manufacturers of the nickel cadmium batt-

If cells are overcharged at C/IO rate for extend-

SPECIFICATIONS. Above I ampere there is a

This degradation in accur-

However,

(for instance, 2 amperes on the Model 172, or

AC voltage specifications are

Keithley recommends that

Nickel Cadmium batteries also ex-

Do not operate the Multimeter in BAT mode after the LO BAT indicator is lighted. The

discharge characteristic of Nickel Cadmium batteries is such that it maintains a fairly constant l.2V through most of its discharge cycle.

the cell voltage drops fairly rapidly to zero volts. pack drops to zero it is reverse charged by the rest of the cells in series with it.

Although the cells used in the 1728 are guaranteed by the manufacturer to withstand re-

verse charge for 10% of their discharge time,

reverse charge cells, as more rapid cell degradation may occur.

The cells used in the 1728 should give a minimum of 250 discharge/charge cycles and

typically 500 discharge/charge cycles.

day) the battery pack should give a minimum of one year operation and typically two years.

Longer life’should.be expected for less frequent useage.

Thus, based on daily useage (5 day week, one per

it is not a good practice to continually

At the end of the discharge curve

After a given cell in the battery

AB

3-25

I

urtHATlNG

INSTRUCTIONS

Summarv of Fuses and Miscellaneous Replaceable Parts

INSTRUCTION MANUAL

Digilal Multimeter

Models 172,113

TABLE 3-12

-

ITEM

:use, 3 AB/3 AG, l/4 A, Slo-Blo :use, 3 AB/3 AG, l/8 A, Slo-Blo ‘use, 3 AB/3 AG, I A, Slo-Blo ‘use, 3 AB/3 AG, 2 A Quick :use, 3 AB/3 AG, 3 A Quick .op Cover (less metalcal) lottom Cover (less metalcal) landle (less insert)

+ Insert

:ubber Foot

WHERE USED

ll7V Line Volts

23411 Line Volts Model 1728 Model 172 Amperes

Model 173 Amperes

KEITHLEY PART NO.

FU-17 FU-20 FU-IO FU-13

FU-2

27979C 25727E 25729D 260YOA FE-IO

-

-26

AA

INSTRUCTION MANUAL Dlgllsl Mullimeler

Models 372.173

ACCESSORIES

SECTION 4. ACCESSORIES

4-l. use with the Model !72/173 Digital Multimeter.

b-2. or rechargeable Battery Pack (Model 1728). described in Section 2.

installable.

4-3.

factory-installed or field-installable.

(paragraph 3-12.)

4-4. RACK MOUNTING. THE Model 172/173 can be rack mounted in a full rack (I9 inch

width) in either a single or dual mounting configuration.

Description:

The Model 1010 is a single rack mounting kit with overall dimensions 5-i/4 in. (133

mm) high and 19 in. (483 mm) wide. The

hardware included in this kit includes a

19 inch wide panel and other miscellaneous

hardware.

Parts List:

GENERAL.

POWER OPTIONS.

ISOLATED DIGITAL OUTPUT.

The Model 1722 and 1728 cannot be installed and used at the same time since both options occupy the same location on the Model 172/173 chassis.

This section describes the various accessories and options available for

The Model 172/173 can be powered by line voltage (105-125V standard)

Other line voltage ranges are available as

The Model 1728 is available factory-installed or field-

The Model 1722 Digital Output Interface is available

Complete specifications are given in Section 3

IMPORTANT

MODEL IO10 SINGLE RACK MOUNTING KIT

Application: The Model 1010 adapts one Keithley Style “K”

instrument for Standard 5-l/4 in. (I33 mm)

x 19 in. (483 mm) rack mounting with II in.

(280 mm) depth behind the front panel. For

dual rack mounting of Style “K” instruments

the Model 1017 Dual Rack Mounting Kit must

be used.

I tern

I

40.

I Front Panel 2 Support Plate (Shelf)

3

4

5

6 Flat Washer, #6

7

AB

Description

Bracket, Left Side Bracket, Right Side Slotted Screw,

Phillips Screw, #8-32 x l/2 in.

#b-32

x 2-l/4 in.

Illustration

-

4-I

4CCESSORIES

Assembly Instructions:

I .

Using two Phillips Screws (Item

(Item I).

INSTRUCTION MANUAL

Digital Multimeter

7)

attach Support Plate (Item 2) to Front Panel

Models 172. 173

2.

Using four Phillips Screws (Item 7),

3

and

4)

to Front Panel (Itw I).

Using four Phillips Screws (Item

3.

port Plate (Item 2).

4.

Assembly of rack hardware is complete except for mounting of Instrument.

5.

Rotate

dle can be removed completely if desired by separating top and botto- covers.)

6. Remove two Slotted Screws (l-l/4 in.

gether near front feet.

Position Instrument so that holes in bottom of Instrument align with two front

7.

holes on Support Plate.

Using two Slotted Screws (Item 5) and two Flat Washers (Item 6). secure Instru-

a.

ment to Support Plate.

“handle” of Instrument so that handle is toward rear of Instrument.

attach left and right side Brackets (Items

secure left and right side Brackets to Sup-

7).

long) used to hold top and bottom covers to-

(Han-

I 4-2

FIGURE 20.

Model 1010 Single Rack Hountinq Kit.

AA

I

INSTRUCTION MANUAL

Digllal Multimeter

Model. 372. 173

ACCESSORIES

MODEL I017 DUAL RACK MOUNTING KIT

Description:

The Model 1017 is a single/dual mounting kit with overall diwnsions high and I9 in.

included in this kit includes a I9 inch wide

panel,

Parts List:

and other miscellaneous hardware.

(483

5-l/4

mm) wide.

in.

(I33 mm)

The hardware mn) x I9 in. (483 mm) rack mounting with Ii

teni

lo.

I

2

3

4 5

6

7

Description Front Panel

Support Plate (Shelf) Bracket, Left Side I

Bracket, Right Side I Slotted Screw, i6-32 x 2-l/4 in. Flat Wasner, ;6 4 Phillips Screw, !8-32 x l/2 in.

Application: The Model 1017 adapts two Keithley Style

“K” instruments for’standard

in.

(280

mm) depth behind the front oanel.

Qtv

Req’d

I

4

Kei thley Part No.

28092D 28OY4C 280968

280978

-_

__ __

IlluStralion

a

cs f”TJj

5-l/4

in. !I33

-I

=?

Blank Cover Plate I 28098B

8

9

handle.

and remove handle. Replace the top cover and tighten the four screws on the bottom cover

6.

gether near the front feet on each instrument. nose pliers should be used to pull the screw out after it is loosened with a screwdriver.

7.

the two front holes in the Support Plate.

8.

ment to the Support Plate.

Hole Plug 2 HP-20

Kep Nut, ,“8

Loosen four screws on the bottom cover of the instrument, lift off the top cover

Remove two Slotted Screws (i-l/4 in.

Position the Instrument so that holes in the bottom of the Instrument align with

Using two Slotted screws (Item 5) and two Flat Washers (Item 6) secure the Instru-

5

long) used to hold top and bottom covers to-

These screws are captive and a needle-

-_

a

AB

4-3

I

ACCESSORIES

INSTRUCTION MANUAL

Digital Mullimeler

Models 172. 173

FIGURE 21. Model 1017 Dual Rack Mounting Kit.

4-5.

Model 172/173.

Description:

Description: The Model 1682 is an RF probe for measurement up to 100 MHz. The Model

Description: The Model 1685 is a clamp-on current probe for measurement of ac current

PROBE AND SHUNTS.

The Model 1600 is a divider probe for measurement of high voltage up to

40 kilovolts dc. The probe is optimized for use with a dc voltmeter having 10

megohms input resistance.

1682 is optimized for use with a dc voltmeter having 10 Megohms input resistance.

up to 200 amperes. The Model 1685 is used with an AC voltmeter and provides an outp,ut of 0.1 volt rms per ampere.

The following probes and shunts extend the capabilities of the

MODEL 1600 HIGH VOLTAGE PROBE

MODEL 1682 RF PROBE

MODEL 1685 CLAMP-ON AC CURRENT PROBE

4-4

AA

INSTRUCTION MANUAL

Dlgltal Multlmeler

Models172,173

ACCESSORIES

MODEL

Description: The Model

having at least 100 microvolts resolution. The shunt is rated at up to

4-6.

use of the Model 172/173.

Description:

Description: The Model

CABLES AND CONNECTORS. The following cables and cpnnection Kits enable effective

The Model 1683 is a set of flexible test leads, 40 in. (Im) in length,

with interchangeable screw-on adapters.

by a banana plug and spring-action clip-on probe.

1651

is a 0.001 ohm shunt for use with an AC or DC voltmeter

MODEL 1683 UNIVERSAL TEST LEAD KIT

MODEL

1681

is a set of test leads,

MODEL 1727 DIGITAL OUTPUT CABLE SET

1651

CURRENT SHUNT

1681

CLIP-ON TEST LEAD KIT

48

in. (1,2m) in length, terminated

50

amperes.

Description:

cable terminated by mating card-edge connectors to the model 1722.

is 3 feet long (I m),

Description: The Model 7004 cable is a shielded cable,

terminated by 2 tinned leads plus shield. use with Models 172/173.

Application: The Model 7004 cable is useful when making low-level voltage connections

to the Model 7021'7029 Low-Voltage Scanner,

may be connected to the GUARD terminal.

4-7.

Description: The Model 1725 contains a specially punched calibration cover for access-

MISCELLANEOUS.

ability to adjustment controls on the Model 172/173 chassis.

The Model 1727 is a cable set consisting of 26- and 40- conductor ribbon

The Model 1727-3

and the Model 1727-10 is ten feet long (3,l m).

MODEL 7004 SHIELDED CABLE

42

inches O,l m) long and is

Two banana plug adapters are furnished for

both analog INPUT and OUTPUT.

MODEL 1725 MAINTENANCE KNIT

The shield

AP

4-5

I

ACCESSORIES

MODEL 702/7029 LOW-VOLTAGE SCANNER

Description: The Model 702/7029 is a ten-channel low-voltage scanner. The 702/7029 can

be used for manual, scan,

or remote scanning operation.

INSTRUCTION MANUAL

Digital Multimeter

Models 172, 173

I

MODEL 750 PRINTER WITH MODEL 7501-1722 PRINTER INTERFACE

AA

INSTRUCTION MANUAL Digllel Mullimeter

Models

172.173

THEORY OF OPERATION

5-l.

172/173.

GENERAL. This section contains circuit description information for the Model

The description is broken down into the following major categories.

a.

Input Signal Conditioning.

b.

Power Supply

c.

Display Board

d.

Durrent Board

e. Battery Pack (Model 1728).

f. A/D Converter

Digital Interface (Model 1722).

4.

POWER

SUPPLY

(SCHEMATIC 286560)

SHEET 3 OF 3

SECTION 5.

f----c

THEORY OF OPERATION

(OPTION)

MODEL

(SCHEMATIC

1728

BATTERY

PACK

27903~)

-&CHEMATIC 28656C) SHEET I OF 3

MODEL 173

CURRENT

BOARD

(SctiE~ATic 27478~)

FIGURE 22.

SCHEMATIC

(OPTION)

Overall Block Diagram of Model 172/173.

27902E

28019~

THEORY OF OPERATION

INSTRUCTION MANUAL

Digital Mullimefer

Models 172. 173

5-2.

switching,

function.

1 BAT

I

-__-~--

I-~

I

INPUT SIGNAL CONDITIONING.

a. Switching.

Switch

Line Line ~

AUTO/MAN

(Schematic

overload protection, ohms converter, ac/dc converter, and filter.

The interlocked pushbutton switches set the DMM to the appropriate

Table 5-l summarizes the switching scheme.

TABLE S-1.

Sumnary of Pushbutton Switching

Style

Push-Push I” Push-Push

Push-Push / IN

I Push-Push j Out

I

L

~ Push-Push

Push-Push

ISetting I

: out

I

I” DMM is set to MAN (Manual mode).

Out

27903E).

1 DMM is powered by ac line power. j pack (if installed)has a trickle charge. I DMM is disconnected from line power.

pack (if installed) is charged at maximum rate

if line cord is connected to power.

DMM is powered by internal Battery Pack.

i DMM is disconnected from Battery Pack.

i Interlock preveots both pushbuttons IN at the

/ same time. 1 OUT before either can be set to IN. 1 Push means that a single depression will

place the pushbutton to IN, a second depress-

oon will release the pushbutton to OUT.

--

range depress either DN RANGE or UP RANGE. See also REMOTE PROGRAMMING OPTION. DMM is set to AUTO (Automatic Ranging Mode.) DMM range is set automatically

This circuit consists of input

Remarks

NOTE

Both pushbuttons must be set to

Battery

Push-

To change

DN Range

j (

.-UP Range

5-2

Momentary

__--__

“Interlock

In

I”

--__

Momentary depression causes the DHM to down

range one decade to lesser sensitivity. Operable only when AUTO/MAN is IN.

Momentary depression causes the DHM to up

range one decade to greater sensitivity.

Operable only when AUTO/MAW is IN.

t

I”

%%Ts set to DC mode. Overrides AC and n

functions due to interlocked pushbuttons. DMM is set to AC mode. functions due to interlocked pushbuttons.

DMM is set to R mode. Overrides AC and DC

functions due to interlocked pushbuttons,

1

also overrides V/A switch.

Overrides DC and R

-

__

j

i

AB

I

lNSTRUCTlON MANUAL

Dlgilal Mulllmeler

Models 172, 173

THEORY OF OPERATION

TABLE 5-1 (Continued)

Summary of Pushbutton Switching

Switch '7 ;':

Can be depressed and held IN simultaneously

V/A

V/A H,,LO;::>::

” , /LO i:‘l :;

w , R E , 4 w , R E 5 :i i’

Push-Push

Push-Push Push-Push

Push-Push

Setting

out

Out

I

I"

Remarks

;'NOTE

If DC, AC, and n pushbuttons are OUT simultan-

eously,

input terminals will be open-circuited, and

the DMM will display R.

ing is meaningless.

DNM

DC). DMM

DC). DMM DMM IS set to high ohms range. 2.:

Only functional when set to i:. DMM is sat for 4-WIRE ohms measurements.

upper pair of terminals are used for Voltage sensing.

used for ohms source.

minals are useable only in 4 WIRE r. mode and are open circuited for all other cond-

itions.

DMM is Set for conventional Z-WIRE ohms measurements.

must be used. open-circuited.

L

no function will be selected, the

The displayed read-

s set to measure current (either AC or

Not functional when set to :I.

s set to measure voltage (either AC or s set to low ohms range. :+;b

..,

Lower pair of terminals are

Lower pair of ter-

Upper pair of Terminals Lower pair of terminals are

AB

TABLE 5-2.

Gain Chart For AC/DC Voltage

RANGE CONTROL LINES

RANGE ATTENUATION

300 mV +l Xl0 +a v

3v il

30 v

300 v

1000 v

+I00 SIOO

ilOO

A/D GAIN RL

Xl +8 v

Xl0

Xl ov Xl

ov

ov -8 v

H

-12 V

-12 v

5-3

EORY OF OPERATION

DC Volts input Circuit.

DC Volts input circuitry is used to attenuate the input if necessary and filter

I. It unwanted AC signals. ive ranges of DC Volts.

A combination of attenuation and A/D converter gains allows See Table 5-2on page 5-3.

INSTRUCTION MANUAL

Digilal Mullimeler

Models 172.173

There is no attenuation on the 300 m V and 3 V ranges.

2.

mown in this position.

rester than 109 ohms.

Above 3 volts,

3. evels, f at least ilOO so that normal mode rejection is maintained. RL line controls K901 and

line controls QYOl (See table 5-2).

4. sltage is applied on the 300 m V or 3 V ranges, fter R929. 307 keeps the relay voltage from becoming large enough to cause arcing or plazma effects.

Ti

he clamp is essentially an open circuit between ?5 Volts.

. Filtering Circuit.

I. ale active filter with 3 db frequency of 5Hz and a settling time of less than 300 ms o within 0.01%. he other ISOK!? comes from various sources in the following manner:

ilO0 with FET switch QYOI off and +I000 with Q901 on.

Overload protection is assured by the clamp circuit, RY29, and

RY29 absorbs the input voltage.

The DC filter is used in front of the A/D Converter on all functions.

It requires an input resistance of 200K9, bY.YK< of which is RYl8.

In DC Volts, 300 m V and 3 V range: RY2Y, In AC Volts, all ranges: R801

I" il

The attenuator is bypassed which allows the input resistance of

relay KY01 switches in the attenuator.

the clamp limits the voltage to i5 V

As the relay switches in the attenuator,

30 V and 300 V range: RYlY + R908 + RYll+RYl0

, all ranges: RY.28

Relay KY01 (Figure 23) is

There are two attentuation

C9Ol assures AC attenuation

C907.

If a large

It is a 3-

j-4

INPUT

-.OluF

FIGURE 23.

DC Volts Input Circuit.

AA

i

INSTRUCTION MANUAL Dlgltal

Models 172. 173

This ZOOKR is also maintained so that the etfect of A/D input current is autozeroed out

(See A/D discussion, section 5-7). path. They are blocked by C905 & C904. circuit. R92lisacurrent limiting resistor and C903 frequency compensates U901.

d.

ered and passed on to the A/D converter.

with maximum gain of unity.

relay K801 and FET ~804 respectively.

(see table 5-2).

Multimeter

The DC filter contributes no DC offsets to the signal

R922, R917, C902 G U901 complete the filter

AC Attenuator.

AC voltages are first attenuated if necessary, converted from AC to DC, then filt-

1.

2.

The AC attenuator (Figure 24) is really a frequency compensated summing amplifier

Its other gains are ~100 and

RL line controls K80i and H line controls ~804

+lOOO which are switched by

THEORY OF OPERATION

C908 blocks DC signals up to +-lOOOV,

3.

pressure of DC voltages. The attenuator is referenced to -6 Volts to keep the DC bias

voltage on ~808 and C809 (figure 25) near zero.

-2 f

The gain of the attenuator is

4.

of Zf equal to the RC t im constant of 2 IN, the gain of the attenuator is constant with

frequency,

limited by RC time constan

values of resistance and capacitance are shown in Figure 24.

Amplifier ~803 is powered from +3 V and -15 V.

agz*at minimizes settling time when autoranging.

e. AC Converter.

The AC converter is a transconductance amplifier. The simplified circuit shows

1.

the basic operation. The AC input voltage (Ein) is converted to a current (Iin) because of the summing amplifier configuration. This current flows through the FET when negati* and through the diode when positive. Thus Eout is a half wave rectified signal if the

polarity is negative. Eout is the input current flowing through Rout. of the converter amplifier is referenced to a negative voltage to allow voltage swing

across the FET (~801).

and equal to

the output is -6 Volts which keeps DC voltage off of C808 and C809.

-.

This is true in the midband region. Low frequency is

R!‘of ~908 and RIN (R818)

TN= Ri (l+jwRfCf).By making the RC time constant

so that AC signals may be looked at in the

-Rf (1cjwRiC~i)

and high frequency by ~803. Nominal

When overloaded the average volt-

This

The + terminal

The ac converter consists of dual FET Q803, operational amplifier ~801 and HOSFET

2.

Q801, diode CR801, and transistor ~802, semiconductor elements.

is ~812 and R807, and the output resistance is ~802 in series with ~803 adjustment pot. FET Q801 is located in the feedback loop of the converter amplifier and the gate of this FET is driven from the output of the amplifier for one polarity.

For the other polarity the feedback path for ~801 and input FETs Q803 (a,b) is

3.

through diode CR801 and transistor ~802. When the

side of ~812, current flows into the summing junction of the amplifier which is the gate

(Pin 3) of the base emitter junction of Q802 and pulls current through diode CR801 so that the

connection path is through ~812, R807, CR801 and ~802 emitter to collector to -15 volt SUPPlY.

load on amplifier ~801 in each of its two polarities, tion which might occur in ~801 because of unequal output current Loading.

AA

~803

The reason that Q802 is a transistor and not a diode is to equalize the output

and this current causes the output of Q8Ol to go negative.

‘ignal is positive at the input

and avoid any parasitic oscilla-

The input resistance

This turns on

5-5

Tt iORY OF OPERATION INSTRUCTION MANUAL

Digital Mullimefer

Model* 172.173

TO AC

CONVERTER

0

C808

Ein

~809

--l(--AANb-

FIGURE

lin

4804

24.

4

I

Simplified AC Attenuator Circuit.

-lin

t-

158.4

pF

K801

\

Rout

Eout

~802

~803

5-6

Rin

~812, R807

r

+lin

~802

k”’

-V

FIGURE 25. AC Converter Circuit.

AA

INSTRUCTION MANUAL

Dlgilsl Mulllmeter

Models 172. 173

4. When the input voltage is negative to the input side of R812 the current will flow out ~807 and ~812 and thus the output of Q801 will go positive, thus forward biasing the gate of Q801. This turns on Q801 pulling current through resistors R802 and ~803 from signal ground.

is a half cycle sine wave of negative polarity.

and

~802

DC with only 6 volts available from Q8Ol. needed.

I Volt DC out.

5.

The 10 m V adjustment feeds a small correction current to the summing junction to adjust

for leakage current errors.

300 m V and 3 V ranges.

(Section 5 C) whose input is R801 & ~801 in this case.

6.

converter. They keep voltage offsets of ~803 (AC attenuator) and Q803 and ~801 from reaching the output.

which filters the DC voltage. The transfer gain of the AC converter is unity.

Q803 is a dual FET used as source followers with source resistors R805 and R806.

The only blocking capacitors needed are C808 and C805 on the input of the AC

Thus Q801 only conducts for negative input signals and the output current

This output current flows thru CbO3

This filtering action allows the necessary 3 V

Without ~803, more than 9 V swing would be

One volt AC RHS sine in causes

The I Volt IKHz adjust calibrates the system gain on the

Additional output filtering is provided by the DC filter

THEORY OF OPERATION

The AC System common is the -6 Volt reference.

7.

~802

between 6V and signal lo to minimize AC noise pickup.

f.

used. the summing amplifier and connecting the unknown resistor in the feedback loop of U702

3.3444 V or the .33444 V reference is connected to buffer amplifier U701 thru, switching FETs Q702 or Q703.

334.44K, 33.444MG) to give six decade values of current from 10 “anoamperes to I milli.3tllpere,

a fixed resistor and the on resistance of a FET (no FET for 33.44&M:;).

which can turn on semiconductor junctions for on scale readings.

which do not turn on semiconductor junctions for on scale readings. See Table5-3.

and input divider ~811 and R810.

Ohms Circuit.

The ohms circuit is a current generator.

I .

The current is generated by applying a reference voltage to the input resistor of

to force the current through the unknown resistor.

The output of the buffer drives one of three resistors (3.3444K,

and thus six ohms ranges.

High ohms puts the A/D converter on the 3 Volt range,

2.

Low ohms puts the A/D converter on the 300 m V range,

3.

C807 is used to provide a low impedance AC path

Each resistor consists of a” adjustment potentiometer,

A summing amplifier configuration is

It is composed of voltage follower

Refer to Figure 34a. Either the

allowing 6 resistance ranges

1

There are time and temperature drifts associated with amplifiers U701 and U702.

4.

These effects are compensated for by the A/D converter.

the A/D converter in R function is the output of U7Ol.

compensated for every conversion cycle.

zero” one is calibrated to every conversion cycle. current is a function of only the stability of the R resistor. high terminal of the ohms source amplifier is compensated for by connecting it to

“auto-zero” 2 when in the ohms mode.

In 2-wire ohms the leads connect at the front panel binding post. Therefore a 4-terminal

ohms system exists up to the front panel terminals.

A6

The negative input of U702 is what “auto”

Therefore,

“Auto-zero” 2 is the zero for the input signal.

The reference used to calibrate

Therefore, any drift in U7Ol is

the stability of the ohms

The lead drop in the

See Section 5-9.

5-7

iEORY OF OPERATION

The ohms switching FETs (Q703, Q702)

5. Q710 is driven from the A-line and Q707 is driven from the B-line. used and decodes to operate the Model 173 autoranging current.

FET input amplifier. connected to the signal ground, clamp transistor.

the output side of U702 are allowed.

normal operating conditions Q704 is operated in the saturated mode, overload conditions, Q704 becomes a current source with its collector to emitter breakdown handling large voltage excursions when signals are positive with respect to the ohms source high. However, if signals are negative with respect to the ohms source high, CR703 reverse biases, cutting off that portion of the circuit. All of these high voltages will cause current to flow through R703 (IZOKR) which is connected to the +I5 volt supply.

of R703 (a half watt resistor), and Q704’s 400 volt breakdown.

RANGE RANGE

HIR LOR

3;:

300K

3M

3OM

300M 3::

The maximum limitation of 250 volts rms is a function of the power rating

300:: 3.3444K 3.3444”

3:: 334.44K

300K 334.44K .33444”

This amplifier is overload protected by Q709 base emitter junction

and Q708 base emitter junction connected through Q706

Thus the input swing is clamped.

This is done by Q704, Q705, and CR703. Under

TABLE 5-3. OHMS RANGES

I

R

3.3444K

33.444M

33.444M .33444”

/

I

-33444”

3.3444”

are driven by transistor Q701 and the C-line,

Very large voltage excursions on

REF

“I

OHMS

I

CURRENT

I mA

IOOuA

IOuA

IvA

100 nA

IO nA

INSTRUCTION MANUAL

Digital Multimeter

Models 172.173

These lines are also

Amplifier U702 is a

However, under

RANGE LINES

Range Selection.

9.

Ranging is accomplished by RSA t RSB lines going to LSI circuit UlO3. by the front panel switches AUTO/MAN, DN & UP, according to Table 5-4.

edge sensitive, causing range changes when their levels are changed. uprange or one downrange per button push.

TABLE 5-4.

Range Selection

Range Switches

AUTO/MAN DN

OUT X X 0”

IN OUT IN IN

X E DON’T CARE

IN

OUT

UP

OUT OUT +8v

IN +8” +8” UPRANGE

Range Lines RSA

0”

RSB Action

+8”

0”

AUTORANGE

0” HOLDRANGE

DOWNRANGE

They are controlled

RSA & RSB are

This causes one

5-8

AA

INSTRUCTION MANGAL

Digllsl Mullimeler

Models 172, 173

h. Function Switching.

THEORY OF OPERATION

TABLE

Function Select

FUNCTION SWITCHES

FUNCTION DC AC

DC”

DCI ACV AC I OUT Hln

LOI!

X s DON’T CARE

Function selection is accomplished by connecting function lines R, AC/DC, & VI according to Table

5-5.

IN IN

DUT IN OUT OUT

OUT OUT OUT X IN

The function lines are level sensitive.

OUT OUT

IN

OUT

V/A

OUT OUT X

IN

X

OUT X

i:

IN

5-5.

H I /LO

inn

X

OUT

IN

FUNCTION LINES

c

AC/DC VI

+8v +8v +8v

+8”

+8v

+8v +8”

ov 0”

+8v

0” 0”

0”

+8v +8v

(172)

0”+;;73)

+8v (172)

0” (173)

+8”

5-3.

line transformer, line voltage switching and power switching for the Models 172/173.

There are three separate regulators used in the Model 172/173. One is a ?15 volt regula-

tar , VR603,

+I5

173.

the LSI chip, (UlO3 on A/D converter schematic 27904F). There is also a +5 volt regulatar , VR602.

the A/D converter, and all the relays. VR603 is a 215 volt dual tracking regulator. It is an integrated circuit with complete regulated circuitry and reference elements built

into the unit. It is either driven by T60l transformer, the Model 1728 Battery pack. Connected to the transformer is a full wave rectifier, then two filter capacitors, C607 and ~611,

These voltages are higher than VR603 needs because they are used to recharge the battery pack. generated.

If

1728

resistors, ~604, R610, and ~605, feed the charge inputs on the battery pack. resistors drop the charging current down to the trickle charge level.

When the instrument is in the 1 ine operated mode,

to R601, which goes to the + input of VR603. ~602 and goes to the - input on VR603.

excess power, which is not necessary to be dissipated in the regulator.

POWER SUPPLY, SCHEMATIC 28656E. This schematic contains the voltage regulators,

which has three percent accuracy, typically 0.1% regulation, and delivers

volts at approximately a

There is also an 8 volt regulator,

This regulator is used to drive the display, the digital logic circuitry in

65

milliampere level to most of the circuitry on the l72/

VR601, which is used as the positive supply to

or from ?19.2 volt batteries in

~~602,

supply + and - 30 volts unregulated to VR603.

If the instrument is off but the line cord is powered, unregulated voltages are

a Model 1728 battery pack is installed in the Model 172/173 the batteries of the Model

will be charged through the unregulated voltages.

the +3D volts unregulated is connected

The -30 volts unregulated, passes through

These resistors are used to absorb swne of the

When instrument is line powered,

These

AB

5-9

i

‘HEORY OF OPERATION

INSTRUCTION MANUAL

Digilal Mullimeler

Models

172, 173

The 8 volt regulator, VR601, gets its unregulated input from the unregulated Vt input on

~~603,

lown to an acceptable level for ~~601.

irom transformer secondary 7 and 8, full wave rectifier CR601 and R603.

also changes the 8.4V batteries.

latteries connect to the input terminals of VR603 and VR602. VR6Ol ( ‘s fed through the 270 ohm resistor.

transformer to the Model 1722 for its regulated 5 volt supply.

This input goes through a dropping resistor,

The input for VR602 (5V regulator) is derived

In BAT mode,

the t19.2 volt batteries and the +8.4 volt

The line switch applies ac voltage from the

R606, to further reduce the voltage

This voltage

the 8 volt regulator,

Thus, when the 172 or I73

are turned off the 1722 turns off.

Transformer T601 has two internal shields, one secondary shield tied to pin IO, and one qrimary shield tied to power ground. This shielding provides line isolation. When the

dual primary of T6Ol are tied in parallel by switch 5601, the Model 172/173 is connected

for 117 volt operation.

operation,

as indicated on the schematic. Provision for 100 volt line is interchanging

Switch ~601 also puts these primaries in series, for 230 volt

connections 5 and 6 and connections 2 and 3 on the primaries. This is a physical wire

change that must be made on the printed circuit board, and is a factory option.

rhere are two connectors for the Model I728 battery pack, ~602 and P606. terminals are on the rear panel.

“ohms” self-check.

Connect from the appropriate self-check terminal to the input high

terminal to exercise the instrument. ~:urrents are only apptoximate. checking of the +19.2 volt battery in the Model 1728.

indicate when the batteries have become low and need recharging.

There is an “a? self-check, “dc” self-check, and an

The self-check is not accurate, the voltages and

A battery test point on the bottom of the instrument alIars

Normally the low battery light will

However, it could be

The self-check

Jsed to troubleshoot for a defective cell. 5-4. DISPLAY BOARD, SCHEMATIC 27404D.

This schematic shows the display digits,

a.

drivers and timing mux generator.

indicators are fully multiplexed. The mux (UlO3, Schematic 27904F).

times are generated by shift register U3Ol whose inputs come from the

These time slots are referred to as to, t,, ~2, r3, t4, t5.

The entire display, This is accomplished with six time slots (timing mux).

the LED function indicators, all display

including minus sign and function

LSI

chip

The common anodes of each digit and the common anodes of the function indicators are

driven from the appropriate mux line, See fiqure 26.

operating digital interfaces (See Section5-8, 1722).

sequence to thru t5, seconds each.

b.

The data mux lines, a, b, c, d,

One complete mux cycle is 1.53 milliseconds.

segments and the function indicators.

tg and t, are 383 microseconds each, and t2 thru t5 are 191 micro-

e, f, g. and dp drive the cathodes of the display

See Table 5-6.

These mux times are also used in The mux times occur in the

The data mu lines are generated in

the LSI chip (UlO3, Schematic 27904F).

c. The 10,000 digit only indicates 1, 2, or 3 in overrange.

zero, it is blanked by the data mux lines.

It is necessary to operate the function indicator and minus sign twice as long as the digits. juring tl,

same brightness as the other digits,

the 10,000 digit time, tl is as long as to.

a,b,c,d,e and f data mux lines for this digit are on

Since “AC” and I’-” are activated

To keep the 10,000 digit the

If the 10,000 digit is

for half of tl time.

d. The anode driver transistors are saturating switches (Q301 thru Q306). The segment

driver transistors are emitter followers (Q307 thru Q314). R302A thru R302H are current

limiting resistors. Segment current is approximately 30 milliamperes peak. 17303 &

C3Ol decouple current spikes from the 5 volt power supply. C302 decouples U301 from power supply.

CR301 and R304 prevent parasitic oscillation of segment driver transistors. 1

5-10

AB

INSTRUCTION MANUAL Dlgltsl MultImeter

Models 372, 173

THEORY OF OPERATION

8

LINES

-

a

b b (b b

I ic ‘,

d

e

f f f

9

d

e e

g / g g g / g for last 5 of ti k:: indicator

DRIVES DISPLAY SEGMENT OF INDICATOR LIGHT DURING

t5 I t4 ‘3

a

a a

I ic

d

/

c

d id

e

f

TABLE

Display Data MUX Lines.

t2

a

/ b for last ‘, of tl ,

b

I Off other half.

C

e

f

j AC indicator / all of t,

5-6.

-_ ~~~ tl

a for last L! of t,, Off other half

c Same as above.

d Same as above.

e Same as above.

_~- -.

mV indicator-173

mV/mA indicator-172

V indicator-173

V/A indicator-172 :

uA indicator-173

mA indicator-173

A indicator-173

C indicator

t0

not used-172

I

dp

POLARITY--

dp

dp dp

dp

Off other half “-” indicator

All of t,

MT? indicator

ov I OMSl’

OA !

---

CB

FIGURE 26.

Digital Display Multiplex Scheme.

5-

I I

’ iEORY OF OPERATION INSTRUCTION MANUAL

Digilal

5-5. CURRENT BOARD. Schematic 27478D contains all of the current circuitry which is

( Nntained in the Model 173 and also in the 172. The current circuitry for the Model 172,

I mown at the bottom of the schematic consists of a 2 ampere fuse and a one ohm resistor.

It is switched in front of the ac voltmeter or dc voltmeter for ac or dc amps.

200 milliamperes on the 300 millivolt range, and up to 2 amperes on the 3 volt range. / limit of 2 amperes limits the power in the I ohm resistor. The input impedance is approximately I.3 ohms on both the 300 milliampere and the 2 ampere range. ampere the self-heating effect and TC of the resistor causes the reading error to

ICreaSE!.

rur Model 173 the voltmeter is held on the 300 millivolt range and resistors are switched by means of relays K501, 502, 503, 504, or 505. KS01 connects the input on the 300

I croampere range, K502 on the 3 milliamp range, K503 on 30 milliamps, K504 on 300 milli-

,ps, and K505 on the 3 ampere ranqe. The current resistors are connected in series.

ix502 is connected to the high of the voltmeter (high sense).

me). >tentiometer R512, the 300 milliampere range by R509, and the 30 milliampere range with

R506.

7 diode drops in either positive or negative polarity.

‘me center connection of these diodes. This assures good performance on the 300 micro-

ampere range which nas IO nanoampere sensitivity.

limits the maximum current. The fuse is rear panel accessible. The relay drive tran-

istors are driven by U502. Spike suppression diodes across the relay coils prevent

Jmage to the transistor drivers.

autorange the ohms function,

-:O to decimal decoder U502. See Table 5-7. There is a possibility of a small period of

;me during ranging where all relays may be open.

to the source because the diode bridge will conduct. “gnal lines, A, B, and C from reverse biasing the inputs of U502 when at -12V.

;l5, 516, 517, 513G, 513H

protect U502. Resistors for the top three current ranges are adjusted in shunt rather than in series.

lthough adjustment ranges are equal plus and minus from the nominal value, the adjust-

dnts are non1 inear. Resistors R5l 1, R508, and R505 limit the range of the adjustment

in one direction.

2posite direction. 3 the 300uA current range).

The measurement is thus done four terminal. The 3 ampere range is adjusted with

Input protection is provided by diode bridge CR501, which limits the voltage to

Unity gain amplifier US01 guards

A 3 amp medium acting fuse

Range lines from the LSI chip, lines A, B, and C

and the Model 173 current function.

This will not present an open circuit

DiodesCR507, 508, 509 block the

and 513F are input dividers to drop +8 volts to 5 volts to

Resistors R513D,C, A, B and E limit base current to the transistor drivers.

The pots plus these resistors limit the adjustment range in the

U5Ol hasamaximum input current of 7 nanoamperes (less than 1 digit

R510 goes to signal low (low

They are decoded in

Above I

Multimeter

Models 172, 173

it

allows

Resistors

I

5-12

173 Current Rangina

RANGE RANGE

ACA t DCA RESISTANCE

300~A IKR

3mA 3A

300mA

3A

1 OOR

IOR

IO

0.1n

TABLE 5-7.

RELAY

OPERATED

KS01 KS02

KS03 KS04

A

+8v +8v

-12v

UGE LINE .EVELS

B

-12v

-12v +8v +8v

-12v

+8v

-12v +8v

- 12v +8v

INSTRUCTION MANUAL

Dlgltsl MultImeter Models 172. 173

THEORY OF OPERATION

5-6. MODEL 1728 RECHARGEABLE BATTERY PACK. volts from nickel-cadimum batteries. cadmimum packs which are fused by lA, 3AG Slo-Blo fuses. of seven 1.2 volt “C” cells and is also fused by a IA, 3AG, Slo-Blo fuse. has a built-in recharging circuit which operated from iZ9.5V unregulated supplied by the DMH I ine-power supply.

BT40l Charging.

a. and ~~402 and resistor R402 place a diode drop across R401. maximum charging current.

Q4Ol. charge is maintained when the DMM is line operated,

inserting a limiting resistor in series with the charging circuit (not shown on Schematic 26758~). ln full charge, BT402, & 200mA for BT403). When trickle charged,

line voltage G battery condition from a minimum of C/l00 rate to a maximum of C/20 rate.

Thus I trickle charge may never fully charge the batteries, but is intended to put

sufficient charge into them for short intermittent use.

b. BT402 & ET403 &argi ng.

or Q40l respectively. These circuits operate similarly to the above circuit, except that

they are powered byunregulated +29.5V.

The maximum charging current occurs only when the DWM is set to OFF. A trickle

BT401 is charged via a constant current from Q4Ol. Diodes CR401

Diode CR403 prevents the battery from supplying current through

the batteries are charged at a C/IO rate (45 mA for ET401 t

ET402 & ET403 are charged via a constant current from Q402

ET401 and BT402 are 19.2 volt, .45 AH nickel

The hodel 1728 provides tl9.2 “OILS and +8.4

ET403 is an 8.4~ pack composed

The Model 1728

The resulting current is the

The reduced current is obtained by.

the charge rate varies according to

5-7.

AB

ANALOG-TO-DIGITAL CONVERTER. (Schematic 28656E).

Introduction.

a.

I. The A/D converter,

digital representation of an analog voltage applied to its input.

tional blocks involved in this process are shown in Figure 27. has several distinct modes of operation, broadly grouped as “signal-measurement mode” and “error-correct ion mode”.

is shown in heavy lines in Figure 27. voltage input to display output occurs in two major blocks. Converter) generates a digital pulse train whose frequency is proportional to the

input voltage. incoming pulses for a fixed time period, producing a total count which is proportional to the average of the input voltage over that time period.

The digital chip (a custom HOS LSI circuit) which performs the pulse counting

2.

function also performs a number of other functions necessary for the analog-todigital converter, and for other portions of the DMH. of this digital subsystem will not be given in the following discussion.

ever,

er of the A/D converter will be referred to when necessary.

various of its outputs which are necessary for the operation of the remaind-

The second block (digital chip) contains circuitry which counts the

as its name implies, performs the function of generating a

The basic func-

This A/D converter

The signal flow in the signal-measurement mode

It can be seen that the transformation from

The first block (V/F

Details of the operation

How-

S-13

THEORY OF OPERATION INSTRUCTION MANUAL

Digital Multimeter

Models 172, 173

3.

The first step of the A/D conversion process,

sion, is performed using a principal known as charge balancing.

output pulse train has the property that its average frequency over a given time

period is proportional to the average of the input voltage over the same time period.

Thus,

representation of the trueintegral of the analog input over any specified sampling time. The circuitry which performs the V/F~function is explained in detail in

Section b.

4. The charge-balance circuitry described in Section b, although highly linear, has certain intrinsic scale factor and zero offset errors. converter these errors are corrected for by the use of additional circuitry.

so-called Auto-Zero and Auto-Calibrate circuitry is described in Section c. Section d contains a description of overall A/D converter system operation, combin-

ing the circuit functions described in sections b and c into a complete A/D conver-

sion cycle.

the charge balance technique has the property that the digital output is a

the Voltage-to-Frequency conver-

The resulting

In the complete A/D

This

j-14

FIGURE

27.

Basic Functional Blocks of A/D Converter.

AB

INSTRUCTION MANUAL

Dlgllal hlullimeler Models 172.173

b.

Voltage-to-Frequency Converter.

THEORY OF OPERATlbN

The greatly simplified circuit shown in Figure 28

1 .

principles

in Figure 29. Assume the integrating capacitor voltage, Vi, to be initally negative.

As the input signal current Ix is integrated by the capacitor, Vi rises and even-

tually becomes more positive than the threshhold of the comparator (time t1 in Figure 29.). The comparator output voltage V,, rises to a logic ‘one’. At the next positive-going edge of the clock CID (time t2

in Figure 29), this ‘one’ is latched by the flip flop and appears as the latched

output QR. A quarter of a clock period after that event, (at tj), the out-of-phase clock, Cl, goes high and enables the output of the AND gate,thereby turning on the

current switch.

I is forced to flow out of the integrating capacitor, VT to a negative value. c:osses the comparator threshhold in a negative direction and Vc goes to a loglcal

‘zer0l.

is still a zero and therefore the flip flop output also becomes a zero.

r ference current consequently is not turned on during that clock period, and in

2

fact stays off until the next time the integrator voltage once again rises above the comparator threshhold.

of the charge-balance V/F converter.

For the next half clock period, from t

Sometime (t,) during this reference current pulse, Vi

At the next positive-going edge of clock CID,

Its operating waveforms are shown

which is a logical variable, then

illustrates the basic

Ji :;,& ii’; ;e;~;e;Y”;;;;ent

(t,), the comparator voltage

The

Ix

COMPARATOR

m”,, h

AB

FIGURE 28.

Basic Charge-Balance Converter.

5- IS

THEORY OF OPERATION

INSTRUCTION MANUAL

Digital

Multimeter

Models 172. 173

2. For relatively large values of the input,

the time required for the integrating

capacitor to be recharged above the comparator threshhold is relatively small, and

the charging-discharging cycle described will occur at a high frequency.

values of input current,

ingly longer and the events described will occur at a lower rate.

the recharging time of the integrator will be correspond-

Thus the repeti-

For lower

tion rate of reference current pulses (and digital output pulses) is a function of the input curre,,t.

Notice that the amount of charge removed from the integrating capacitor during.

3. each discharge cycle is equal to the product of the reference current, I , and one-

half the clock period.

be made very stable, with the result that,

cycle is high or low,

pulse) is precisely the same size.

Through appropriate circuit design these two parLmeters can

whether the frequency of the discharge

each increment of charqe removed (i.e., each reference current

Since the total charge removed from the capacitor

in any given time period is equal to the total charge that flowed in during the same time period (within a resolution of one discharge increment) the uniformity of size of the reference current pulse guarantees that the total number of such pulses

is precisely proportional to the time-integral of the input current.

5-16

FIGURE 29.

Operating Waveforms of A/D Converter.

AB

INSTRUCTION MANUAL -

Dlgital Multimeter Models 172, 173

THEORY OF OPERATION

4. Figure to perform the V/F conversion.

already discussed, Figure 30 mentioned.

The input buffer amplifier, U202, serves two functions. First it provides a

a) high impedance input to the A/D converter. Second, it provides a selectable voltage gain of 10, giving the A/D converter in effect two voltage ranges, selected by the

line labeled GIO (an output from the LSI chip).

b) The transconductance amplifier, consisting of op amp UlOl and its associated

MOS FET (QlO4) and resistors, converts the voltage which appears at the output of

buffer amplifier LIZ02 into a proportional current, Ix,

integrating capacitor.

The reference diode and the resistor connected from it to the summing junction

c)

of op amp UIOI provide a fixed current component of I in addition to the variable component I (which is proportional to the input voltsge). This fixed offset current, labeled I allows the overall A/D converter to handle both positive and

negative input vol?iges. half of its maximum possible value when the input voltage to the entire converter

is zero. This transposi.~tion is accounted for in the digital subsystem (LSI chip) by

subtracting a fixed number from the accumulated count before displaying it.

d) The remaining circuitry in Figure 30 is functionally equivalent (with some added details) to the basic charge-balance loop shown in Figure 28. signals QR and CLK are used by the digital subsystem, in effect, to reconstitute the

pulse train discussed in connection with Figure

C.

Auto-Zero and Auto-Calibrate Circuitry.

is a simplified schematic diagram of the c

30

.~

In addition to some added details of the circuitry

shows three major circuit elements not previously

With this arrangement, the output pulse frequency is one

,ircuitry actually employed

which is used to charge the

The digital output

28.

1 . The charge balance system shown in Figure 30. is inherently highly linear, but

both its zero and full-scale calibration (scale factor) are susceptible to drift

with time and temperature, due to a variety of effects. Through the use of a pair

of related circuit functions, referred to as Auto-Zero and Auto-Calibrate, these

intrinsic errors can be cancelled, resulting in a system whose scale factor is

essentially as stable as the voltage of a reference zener diode and whose zero stability is limited principally by thermo-electric offsets.

achieve this performance are described in this section.

It can be shown that all zero-error sources in the charge balance system (such

2.

as offset voltage drift of amplifiers U202 and UIOI, input current drift of amp-

lifier UIOI, etc.) can be represented as a total effective error current at the

summing junction of amplifier UlOl. In a similar way,

lent to an error current at the emitter of the reference current output transistor,

Ql02B.

approprrate correction current at each of these two locations in the circuit.

function of the Auto-Cal and Auto-Zero circuitry, then, is to discover the proper

values of these two currents and to supply them during the measurement of the input

signal.

3.

follows:

volt input would cause the charge-balance loop to deliver reference-current pulses

fo the integrator at exactly l/2 the clock frequency. buffer input is supplied with zero volts, forced to deliver reference-current pulses at precisely l/2 the clock frequency. In a real system with finite offset errors,

It is thus possible to correct for all such errors by introducing an

The method used to “discover

Consider first the Auto-Zero operation.

” the proper value of the correction signals is as

and the current switch is digitally

the current being delivered to the integrat-

all gain errors are equiva-

In an error-free system, a zero-

In the Auto-Zero mode, the

The techniques used to

The

THEORY OF OPERATION

INSTRUCTION MANUAL

Digilal Mullimrler

Models 172.173

I

5-18

FIGURE 30.

Simplifiea bcnematbc or V/F Converter.

AB

5

INSTRUCTION MANUAL

DiglIal Mulllmeler

Models 172,173

or through the transconductance amplifier (I ) does not exactly match this forced

reference current; the difference exactly eq:als the correction current required to cancel the offset errors. balance sawtooth waveform like that shown in Figure 29., Superimposed on a much slower ramp whos.e slope is proportional to this difference current.

feedback system adjusts a correction current which flows into the sumning junction of amplifier UIOI so that the slope of the ramp is equal to zero. zero errors are oreciselv cancelled.

4. The Auto-Calibrate system works in an analogous manner,

of detail:

a) The voltage supplied to the input of buffer amplifier U202 is the exact

amount voltage which the charge balance system can measure.

b) The current switch is forced to a frequency equal to the clock frequency

rather than one half of it.

The feedback correction current is delivered to the emitter of the reference

C)

current output transistor (QIOZB).

5. ‘;

The circuitry which performs the operations described above is shown in Figure 31, together with most of the charge balance system redrawn from Figure 30. The added circuitry is grouped in five major blocks:

Thus the integrator voltage, V., exhibits a charge

THEORY OF OPERATION

The auto-zero

In this way, all

with three differences

Input Multiplexer,

a)

b) Reference current forcing circuitry,

Comparator filter,

C) d) Auto-Zero feedback and storage circuitry,

e) Auto-Cal feedback and storage circuitry.

6.

This circuitry will be described block by block with reference to the above description of its basic mode of operation.

The input multiplexer supplies the necessary

=I

the buffer amplifier at appropriate times, signal source when that signal is to be measured. switches controlled by signals from the LSI chip. shown in Figure 31.

order to minimize the A/D input current.)

b) The reference current forcing circuitry controls the input of the comparator

latch flip flop. alternate between one and zero on successive clock periods. current pulse rate is equivalent to an output frequency from the charge balance system of l/2 the clock frequency. constantly with the result that the reference current is on at every opportunity;

reference-current pulse frequency thus equals the clock frequency. puts,

both Auto-Zero and Auto-Calibrate,

wise.

FON and COFF, are used to control these two operating modes:

are used primarily to neutralize the JFET switching charge in

In the Auto-Zero mode,

In the Auto-Calibrate mode QR is forced to a one

and COFF is zero during Auto-Zero and one other-

and connects the buffer amplifier to the

it forces the output of this flip flop to

“known”

The multiplexer consists of JFET

(the two adjustable capacitors

voltages to the input of

The resulting reference

Two chip out-

FON is oneduring

AB

5-19

rHEORY OF OPERATION

INSTRUCTION MANUAL

Digital Multimeter

Models 172, 173

FIGURE

31.

Simplified Schematic of Complete A/D Converter.

AB

INSTRUCTION MANUAL

Dlgltal Mulllmeler Model8 172, 173

The block labeled “Comparator Filter”, not previously mentioned, serves an

C)

important function in the Auto-Zero and Auto-Calibrate feedback loops. As discussed

above, the component of the integrator voltage which is of interest for Auto-Zero

and Auto-Cal purposes is the slow ramp arising from the effective error currents. Because this ramp has superimposed on it a relatively high frequency triangle waveform, the combination of comparator and comparator-filter functionsas a switching-

mode (class D) amplifier for the ramp voltage, with gain equal to the ratio of the V,

switch to the triangle amplitude.

the switching output of the comparator so that only the low-frequency amplified

ramp signal is passed on to the remainder of the Auto-Zero (or Acal) feedback loop.

d) The Auto-Zero feedback and storage block completes the control loop used to. generate the Auto-Zero correction current. capacitors and consider only the direct signal path via the Auto-Zero loop switch and the JFET source follower. Consider the following circuit elements: uctance amplifier, comparator f i 1 ter) ,

FET source and UlOl summing junction. constitute a simple low-frequency and dc feedback loop which will strive to adjust the voltage across the integrating capacitor to a value near zero. tion has been achieved,

on the desired value, must now be exactly balanced by the switched reference current.

integrating capacitor,

auto-zero loop switch, source follower and the resistor between

then the Auto-Zero correction current I must have taken

since the total current being fed to the %tegrating capacitor

The comparator-filter’s function is to smooth

Ignore for the mcment the two storage

switching mode amplifier (comparator and

Examination shows that these circuit elements

THEORY OF OPERATION

Transcond-

Once this condi-

The remainder of the auto-zero system operation is quite simple. Once the stable

closed loop condition has been achieved, closed and the gate voltage on the source follower (which has the value necessary to produce the correct value of I switch finally opens at the en

was established during the Auto-Zero phase thus remains in effect until the next

Auto-Zero operation.

ONE A/D CONVERSION

4

\

ERROR CORRECTION

IS stored on that capacitor.

gz’

of the Auto-Zero phase, the value of I

one of the two capacitor switches is then

When the loop

which

AZ

P

S I GNAL I NTEGRATE

200ms

*

J

SIGNAL

MEASUREMENT

AB

FIGURE 32.

A/D Converter System Timing.

5-21

THEORY OF OPERATION

e) The Auto-Cal feedback and storage block works in a manner identical to that of the Auto-Zero feedback and storage block, with the exception that its output current is fed to the emitter of QlO2B instead of the summing junction of UIOI. Although the Auto-Zero and Auto-Cal correction operations interact to some degree, a few

sequential iterations of these operations suffice to establish the correct values of

the two correction currents.

d. Overall A/D System Operation.

In the preceeding two sections the structure and function of each major analog

1.

circuit block has been explained. This section contains a description of the manner

in which these elements are combined in a complete A/D conversion. The description is based on Figure 32, an overall A/D converter timing diagram showing one complete

conversion.

The first major division of the conversion period is into an error-correction

2. segment (120 ms long) and a signal-measurement segment (200 ms long). former,

and (as described in Section c ) the correction currents I and I

During the latter,

applied to its input, and its output pulses are counted by the digital chip.

next conversion period begins, plays the result.)

the input multiplexer supplies known reference voltages to the V/F block,

the now error-corrected V/F converter hatZthe un

the chip processes the resulting pulse-count and dis-

INSTRUCTION MANUAL

Digital Multimeler

Models 172.173

During the

are established.

tl

%%n

signal voltage

(As the

The error-coirection segment of the conversion cycle is further divided into

3.

three 40-msec. phases. During the first two of these phases, the buffer amplifier gain is held constant at either IX or IOX (depending on DMM range and function). During the AZ1 phase,

voltage, and the Auto-Zero feedback loop is closed. The value of IAZ required to

correct any system zero-err-ors is established,

(see Figure 31) causes the source-follower gate voltage which produces this current

to be stored on the corresponding Auto-Zero storage capacitor.

During the ACAL phase,

4.

reference voltage (either 3.34 or 0.334 V, depending on buffer gain), and a similar process results in a scale-factor correction voltage being stored in the Auto-Cal storage capacitor.

Buffer gain during the AZ2 phase is always the same as it is during the signal-

5.

measurement phase; it may differ from its value during AZI and ACAL.

(possibly) changed buffer gain, second Auto-Zero operation is required to prepare the V/F converter for an error-

corrected signal measurement.

stored on the capacitor controlled by the AZC2 switch (Figure 31.).

5-a.

MODEL 1722 DIGITAL INTERFACE.

the input multiplexer supplies the buffer with a zero-reference

and the closure of the AZCI switch

the multiplexer connects the buffer input to a full-scale

Because of the

the effective system offsets may have changed so the

This new value of the Auto-Zero correction voltage is

a. Overall Block Diagram. As shown in Figure 33

associated clock lines are first isolated. Output data DOWNDAT goes to the output register block where it is converted to parallel

form and then to the output buffers.

decides where the data is going, out or in,

i-22 AA

The clock lines go to the control block which

Bidirect\onal data line SERDAT is then split.

and also generates the flag.

Serial data from the DMM and its

INSTRUCTION MANUAL

Digltal Mulllmeler

Models 172, 173

THEORY OF OPERATION

Control input data and strobes are first buffered by the input buffer block.

strobes go to the output buffer to gate the outputs.

input register and control block where they are converted from parallel to serial form

and sent to the isolation block. based on control data input,

for the 1722 is provided by transformer TIOOI which is powered by a secondary winding

of the DMN power transformer.

b. Signal Isolation. SERCLK and INCLK each drive an emitter follower made up of transistors 41036, QlO35, and QlO37 whose loads are LED’s in the opto-isolators are pulled up by resistors RIOIO, RI009 and ~1018, which is driven by QlO34 similar to the three just mentioned. put pullup on ~1018 is on the DMM mainframe.

is taken directly from the DMM +5 volts through ~1016 and ~1018 and ClOl7, which provide

the coupling.

Power Supply.

plF;d via pins B and C on JIOIA.

Switching for the power for TIOOI provided at J1003 Pins A and B and comes via the Dtlti mainframe through its Power On switch. and rub through an integrated circuit +SJregulator TRlOOl, where it is again filtered by ClOl5, Cl002, ClOO3, ClOO4, ClOl4. by a green wire to a screw on the DHM mainframe or transformer.

filtering is performed by RI008 and cl006 between output low and chassis ground.

Low voltage ac from the secondary of the DMM transformer is sup-

whether there is to be an output update.

The bidirectional data line SERDAT and the two clock lines

The input register and control block also decides,

Power for the DMM side of the isolatidn

The secondary of TlOOl is rectified, filtered

The core of TIOOI is connected to chassis ground

The control data inputs go to the

Power isolation

Also common mode

The

The out-

Control Block.

d.

El017 timer. A buffered version of UPCLK is also run via diode gate CR1002 to the

threshhold input of UlOl7. edge goes into trigger. since this threshhold is clamped low through diode CRIOOZ. out in the time period of the clock pulses on INCLK until the last rising edge of INCLK. at which time it will clock out at 30 microseconds, therefore UPTIME, the output of UlOl7,

which is the time in which data will be flowing from the 172 to the DMM.

conversion (See Schematic 27902E). flip-flop UlOl5A. The beginning of downtime also defines the time when the flag is set high, change time, or resetting the flag, Downtime also gates DOWNCLK thru UlOl4C & UlO14D where it is called GATECLK and goes to

the output register.

IO;,, & B, IOIOA & B, 1011 A & 8. It is a 32-bit shift register, of which only 30 are

used.

the parallel clock, GATECLK.

shifted in and are presented in parallel to the output buffer.

f.

gates UIOOI thru 1007 and UlOl2 and 1013. and drive transistors QIOOI thru 1030 to output connector Rl006.

will be length of the INCLK pulse stream plus approximately 30 microseconds,

that is when data has finished being updated. Setting the flag lo,,; during data

Output Register.

Serial data enters U1008B and is clocked through all of the shift registers by

Output Drive and Buffer.

UPCLK, the isolated form of INCLK, is run to the trigger input of

UlOl7 is such that its output will go high when a falling

A filter made up of RI007 and ~1008 will try to charge, however,

It will not be able to time

The beginning

This is done by clocking DOWNCLK with UPTIME in

is accomplished in two ways: FR or UPDATE.

The output regi’ster is made up of shift registers UlOO8A & 8,

At the end of the clocking time all 30 bits have been

Parallel data on the output registers goes to output

Here they are gated with the output strobes

Input Buffers.

9.

output drive and buffer block. u1105.

triggering.

UllO4 is a Schmitt trigger and is put on certain control lines to prevent false

Strobelines are buffered by UIIOI and UllO2 and go out to the

Remote control inputs are buffered by UllO4. Ullll,

IORY OF OPERATION

INSTRUCTION MANUAL

Olgltal Multimeter

Models 172.173

-

: b

FIGURE 33.

Model 1722 Block Diagram

7 IEORY OF OPERATION

INSTRUCTION MANUAL

Olgltal Multimeter

Models 172, 173

5-9.

u ing the voltage drop across Rx. a summing amplifier (G AMP) the input to this amplifier being a reference (0 Vref) voltqe

t’ rough an input resistor (RR).

for time & temperature variation of n VRef and R Amp, r sistance. The A/D looks at each of these inputs in time sequence in the following

IT 2ner.

and the voltage across RR.

DETAILED 4 WIRE OHMS OPERATION.

a. The circuit measures a resistor by putting a constant current through Rx and meas-

This is accomplished by putting Rx in the feedback of

a. AZ-I, ACAL, AZ-2, & A/D Signal are the 4 A/D inputs.

as well as compensating for lead

I) AZ-I looks at

2) ACAL looks at :: VREF for 40 ms and calibrates itself to the difference between AZ-l and ACAL. Thus, it is calibrated to the voltage across RG . stable resistor the value of I is now known. Since I flus through Rx the calibration

is fixed.

3)

AZ-2 looks at the voltage at the top of Rx for 40 ms. This is defined as the

zero level for signal measurement and is stored in A/D.

4) A/D Signal looks at the bottom of Rx for 200 m seconds. The A/D thus measures

the difference between A/D signal and AZ-2 without polarity sign.

Rx is displayed. c. The measurement i’s essentially a ratio measurement between the voltage across Rx

!? AMP input for 40 ms and stores this zero level.

This A/D operation compensates

Since Rc! is a fixed

The voltage across

Note that the voltage at the top of Rx is essentially at signal LO of the instru-

d.

ment (2 nAMP offset and lead resistance drop) and the voltage at the bottom of Rx is

negative. Thus, the high impedance terminal is guarded and relative fast response is

i ilieved at high resistance values.

,-26

AA

INSTRUCTION MANUAL

Digilal Mullimeler Models 172.173

MAINTENANCE

SECTION 6.

6-1. GENERAL. Included are procedures for Electrical Performance Verification, Calibration, Trouble-

shooting, and Battery Replacement and Charging.

b-2.

the instrument is given in Table b-l. specifications equal or exceed the stated characteristics.

REQUIRED TEST EQUIPMENT.

TEM

A

DESCRIPTION

DC Calibrator

AC Calibrator

This section contains information necessary to maintain the instrument.

Recommended test equipment for checking and maintaining

Alternate test equipment may be substituted if

TABLE 6-l.

List of Test Eat

lip

Nment For Performance Verification.

T

SPECIFICATION +0.2 V through +lOOO Vdc j

0.2 through 20 v rms ?0.022% + touv

MAINTENANCE.

+0.002% or 2ouv

HFR I HFR MODEL I

FLUKE

343A ~

I

High Voltage Amplifier

Decade Resistor 2Kci through 1OMR

Current Source 200uA through 20 mA

200V through 1000.0 v rmr,

10.04%

10.01%

200Mr. +O.l%

HP ,

ESI

CADDOCK 1

FLUKE

i 0.006%

200mA and 2A 20.02%

Ohmmeter

The equipment listed here in many cases will introduce an additional

uncertainty in the Performance Verification.

should be used when evaluating the displayed reading on the DHH.

1070 21% 109n 25%

NOTE

The Absolute Acc~lracy

FLUKE

KI

74bA

DBb2

MG75C

33306

382A

616

cc

b-l

INSTRUCTION MANUAL

Dlgltsl Mulllmeler Models 172. 173

6-3. PERFORMANCE VERIFjCATION. Use the following procedures to verify basic operation of the instrument. All measurements should be made at ambient temperature of 25°C. and

relative humidity less than 80%. If the instrument is out of specification at any point, perform a complete calibration as given in paragraph 6-4. For each function that is checked,

if the ambient temperature is different from 25” C. Example:

add 5°C of temperature coefficient specification.

a. Battery Check. (With the Model 1728 Rechargeable Battery Pack installed.)

1. Check for proper installation of individual cells in the battery pack as shown

in Figure 7

an additional uncertainty due to temperature coefficient should be considered

If calibrated at 3O”C,

NOTE

This procedure is intended to verify only the basic accuracy of the Model 172/173

in voltage, current, and resistance modes.

Xl0 better than measurement accuracy. In many cases the equipment listed is not

Xl0 better than instrument accuracy because such equipment is not commercially

available.

Test equipment accuracy should be

MAINTENANCE

Depress BAT pushbutton.

2. Verify that the “LO BAT” indicator is not lighted. If lighted, recharge batteries.’

3.

b. How to Charge the Batteries.

sufficiently charged.)

Set the internal line switch 5601 to the appropriate line voltage range.

I.

2. Connect the line cord to the appropriate line voltage.

Release LINE and BAT.

3.

4. Recharge for at least I6 hours to fully charge. Input Resistance Check. (DC VOLTS)

C.

I. Depress MAN.

2. Depress BAT. Select the 3 volt DC range using UP RANGE or DN RANGE pushbutton.

3.

4. Measure the input resistance between HI and LO using DMH (F). Input resistance should be >I x IO3 ohms.

5.

scale).

6. Select the 30 volt DC range using UP RANGE pushbutton.

Measure the input resistance between HI and LO using DMM (F).

7.

(Perform this procedure only if the batteries are not

-

(Make sure that 173 does not read off

AB

Input resistance should be IO megohms ?Zti%.

8.

“NOTE

Battery pack may be discharged to the point where the LO BAT indicator circuit

will not operate. If in doubt,recharge the battery pack at least I6 hours.

6-3

MAINTENANCE

I

Voltage Accuracy Check.

d.

1. DC Voltage. =)

b) Connect the DC Calibrator (A) to the instrument.

INSTRUCTION MANUAL

Digital Mulhmeler

Models 172,173

Set to DC Volts and AUTO.

Set the DC Calibrator to the output specified in Table

C) d) Verify that the instrument reading is within the limits specified.

Repeat steps c) and d) with negative voltages.

e)

DC Voltage Performance Check

Range

300mV

3v 3ov

3oov

1ooov

:tDoes not include the uncertainty of

the DCCalibrator.

1 Voltage

Applied +0.20000Vdc

+2.0000 Vdc

+20.000 ~200.00

+lOOO.O Vdc

Vdc Vdc

Relative Accuracy" Absolute Accuracy:'" kO.l9997 to +0.20003Vdc ~0.19995to *0.20005 vdc

k1.9997 i19.997

~199.97

399.8

TABLE

6-3.

Allowable Reading (at 25'C)

t0

k2.0003

to

+20.003

to t200.03 Vdc

to ?1000.2 Vdc

+*Does include the uncertainty of the

vdc

Vdc

DC Calibrator,

6-3.

?1.9996 to i2.0064 Vdc

119.996 +199.96

?999.7

to

t20.004

to

i200.04

to

t1000.3

Vdc Vdc

Vdc

I

2.

AC Voltaqe.

=)

Set to AC Volts.

b) Set to AUTO.

Connect the AC Calibrator (8) to the instrument input terminals.

cl

d) Set the AC Calibrator to the output specified in Table

50

Hz, then repeat at 20 KHz.

Connect the High Voltage Amplifier (C) to the instrument input terminals.

4

f) Set the High Voltage Amplifier as shown in Table

Verify a displayed reading as shown in Table

9)

6-4

6-4.

Set frequency to

INSTRUCTION MANUAL

Digltal MultImeter Models 172.173

MAINTENANCE

TABLE 6-4.

AC Voltage Performance Check

Rangu

Voltage

Applied

I

300 mv

3V 3OV

3oov

IOOOV

*Does not include the uncertainty of the

DC Calibrator.

e.

Resistance Accuracy Check.

I. High Ohms.

a) Set to ?(OHMS).

b) C)

d)

i-

0.20000 Vrms

2.0000 Vrms

20.000 Vrms

200.00 Vrms

1000.00 Vrms

Set to HI. Set to 2 WIRE.

Set to AUTO.

0.19964

1.9964

19.964

199.64

997.4

Allowable Reading (at 25°C)

to 0.20036 Vrms to 2.0036 Vrms to 20.036 Vrms to 200.36 Vrms to 1002.6 Vrms

**Does include the uncertainty of the DC

Calibrator

0.19959 to

1.9960 to

19.960 to

199.56 to

0.20041 Vrms

2.0040 Vrms

20.040 Vrms

200.44 Vrms

1003.0 Vrms

to

Connect the Decade Resistor (D) to the instrument input terminals.

e)

f) Set the Decade Resistor to the resistance specified in Table 6-5. Verify

the readings given.

TABLE 6-5.

Resistance Performance Check (HI OHMS)

Range

3KQ 30Kn 3ODKn

3Mo 30MR

3DOMn *Does nqt include the uncertainty of the

Resistance Source.

Resistance Setting Relative Accuracy"

2.00DOKn

20.000Ka

200.00Kn

2.0000Mn

20.000MR lg.969 to 2.003lK

200.00MR

I

1.9993 to 2.0007K

19.993 to 2D.OD7K

199.93 to 200.07K

1.9991 to 20.009K

197.99 to 202.01K

Allowable Re< ng (at 25'C)

Absolute Accuracy""

1.9991. to 2.0009KR

19.991 to i'O.Oo9KQ

199.91 to 200.09Kn I.9989 to 2.0011~~

19.967 to 20.033Mn

197.79 to 202.2lMCl

**Does include the uncertainty of the

Resistance Source.

cc

6-5

,

MAINTENANCE

Measure the resistance of the leads and subtract from the resistance reading on

the Model

Low Ohms.

2. Set to cl (OHMS

=) b) Set to LO.

c) set to 2 WIRE. d) Set to AUTO.

e) Connect the Df

f) Set the Decade Resistor to the resistance specified in Table 6-6. Verify

the readings given.

172/173.

INSTRUCTION MANUAL

Dlgllel hl”mmetcr

IMPORTANT

,I

!C

ade Resistor (D) to the instrument and R source terminals.

TABLE

Resistance Performance Check (LO OHMS)

6-6.

Models172,173

Range

3oon

3KQ

30Kn

300KR

3MT:

3OM:i

Resistance Setting

200.00

2.0000K~

20.000KR ZOO.OOKI!

2.0000MR

20.000M!:

I

/

Relative Accuracy"

199.93 to 2DD.07Q I.9993 to 2.0007KQ lg.993 to 20.007KR

199.91 to 200.09KQ I.9979 to 2.002lMn lg.899 to 20,lOlMS!

1

*Does not include the uncertainty of the

Resistance Source.

IMPORTANT

Measure the resistance of the leads and subtract

on the Model

172/173.

Allowable Reading (at 25.C)

Absolute Accuracy""

199.91 to 200.09 I.9991 to z.ooogKn lg.991 to 20.DO9Kn

lgg.89 to 200.llKD

1.9977 to 2.0023M1,

19.897 to 20.103Mfi

""Does include the uncertainty of the

Resistance Source.

from the resistance reading

INSTRUCTION MANUAL

Dlgllal Mulllmeter

Models 172. 173

f.

Current Accuracy Check.

1. DC Current. Set to DC Amperes.,

a)

Set to AUTO.

b)

Connect Current Source (E) to the instrument input terminals.

C)

MAINTENANCE

(Model 173 only)

d) Set the Current Source to the current specified in Table

readings given.

TABLE

DC Current Performance Check (Model

Current

Applied ;tZOO.OOuA *2.0000mA

+-20,OOOmA i-200.00mA +2.0000A

"Does not include the uncertainty of the

CurrentSource.

Relative Accuracy>?

199.78 to 200.22uA 199.77 to 200.23uA

I.9978 to 2.0022mA

19.978

0.19978 to 0.20022A

1.9958 to 2.0042A

to 20.022mA

6-7.

173

Allowable Reading (at 25'C)

""Does include the uncertainty of the

Current Source.

6-7.

only)

Absolute Accuracy**

1.9977 to 2.0023mA

19.977

0.19858 to 0.20142A

1.9838 to 2.0162A

Verify the

to 20.023mA

Current Accuracy Check (Model 172 only)

9.

DC Current

I .

Set to DC Amperes

a) b) Set to AUTO.

Connect Current Source (E) to the instrument input terminals.

C)

d) Set the Current Source

Set the Current Source to the IA.

d

Readings do not account for source inaccuracy. Add 0.02% uncertainty if Current Source (E) is used.

to

cc

200mA.

Verify a reading of 199.48 to 200.52mA.e

Verify a reading of 0.9973 to 1.0027A."

*NOTE

6-7

MAINTENANCE

INSTRUCTION MANUAL

Digllal Multimeter

Models 172,173

Circuit Desig

C203

c205 c817 ~819 ~820

C82l

RI03 R201

R208

R209

R213 RZl7

R704 L

R705 R707 R709 R803 R809 R816

R817

Surrmary of Adjustment Controls

Description

INPUT Current ADJ

OHMS Zero

lOOV @ 20kHz ADJ IV @ 20 kHz ADJ IKV @ 20 kHz ADJ

IKV @ 20 kHz ADJ

Auto Cal

Auto Zero

0.3V Ref

Xl0 Gain

2.9V

Buffer Zero

290KQ ADJ

R Bias

'2.9Kn ADJ

IV I&' IkHz ADJ lOmV @ IkHz ADJ 1OOV @ 1kHz ADJ lKV@lkHz ADJ

Cal

1OMR ADJ

TABLE

T

6-8.

Paragraph

6-4 c2

6-4 c2 6-4 6-4 e7 6-4 e7

6-4 .e7

6-4

6-4 fig 6-4 6-4

6-4 cl

6-4 6-4

6-4 e7 6-4 e7

b-4 e7

6-4~~7

(el (i)

e7

(h)

cl

(i)

cl

d2 (d)

(j)

f24 f7 f9,

tzg

13

T

Schematic Shown

27904F 27904F

27903E 27903E 27903E 27903E

27904F 27904F 27904F 27904F 27904F 27904F

27903E 27903E

27903E 27903E 27903E

27903E

R901 R904

R9ll

R913 R506 (173 only)

R509 (173 only) R512 (173 only)

I-

IKV DC ADJ

300mV Zero

290V DC ADJ

3ov Zero

IOmA DC ADJ IOOmA DC ADJ

IA DC ADJ

6-4

d2 (d)

6-4

dl (d)

6-4

d2 (d)

6-4

dl (g)

b-4 96 b-4

glo

6-4 912

27903E

27903E 27903E

27903E 274780

27478D

-i

AE

INSTRUCTION MANUAL

Dlgllal

Models 172,173

Mulllmeter

MAINTENANCE

TOP COVER

27979c

SPACER 257628

INSERT

26090A

FRONT PANEL 27958A (173)

2802YA (172)

COVER

i

257290

HANDLE

AA

rlbunr ,3.

lop and Bottom Cover Assembly.

6-9

MAINTENANCE

INSTRUCTION MANUAL

Dlgltal Mullimeler

Models 172.173

;;;;ECTS TO

LINE FUSE

F601

LINE VOLTAGE SWITCH

5601

-

FIGURE 36.

NOTE: DRESS WIRES

BETWEEN SHELI AND POSTS BEFORE TOP COVER IS

PLACED IN POSITION.

MODEL I73 SHOWN WITH CURRENT

BOARD

INSTALLED.

Location of Line Fuse and Line Switch.

c-10

AB

INSTRUCTION MANUAL

Dlgilsl Mulllmelar Models 172.113

MAINTENANCE

List of Test Equipment Required For Adjustment/Calibration

ITEM DESCRIPTION

DC Calibrator

AC Calibrator

High Voltage Amplifier

Decade Resistor Oscilloscope

Current Source+

DHM

TABLE

MINIMUM SPECIFICATION NEEDED

6-9.

+0.290005v, +2.90005v, +29.0005v,

+290.005\1, +lOOO.O5V. to within

20 rw

IOmV, IV, IOOV, IOOOV @ IkHz

IV, IOOV, IOOOV @ 20kHz See B above

2KR through 20MR +O.Ol%

IA. IOOmA, IOmA f 0.02%

1.0000v 1 0.001%

HFR

Fluke

HP

ESI

TEK

FLUKE

KI

HFR MODEL

343A

745A

746~

RS725

465 382~

5900

Test Circuit

An alternate Current Source may be assembled using a precision Ii resistor stabilized at constant temperature, adjusted to obtain a 1.0000 V reading across the IR resistor.

to accurately monitor the voltage drop.

6-4.

when a specification has been determined to be out of tolerance.

strument to its maximum published specifications, the Performance Verification procedure should be used.

ical components. Ambient temperature should be maintained at 25-C +I*C.

facing up. and will only unscrew until the screw head is flush with the top of the holes). over the instrument. Carefully lift off the top cover,

to the rear panel.

ADJUSTMENT/CALIBRATION PROCEDURE.

The “tolerance on reading”

a. How to Open the Instrument.

Loosen the four slotted screws in the bottom panel (the screws are captive

Resistor, 2MG Capaci tar,

“NOTE

and a Keithley Model 227 wiich has been

The following adjustments should be performed

is adjusted to allow for time drift of crit-

Turn the instrument over so that the bottom cover is

CAUTION

IuF

Paralleled

1

and disconnect the wires going

KI KI

Use DMM (H)

For checking the in-

.-253-2t1

-215-1uF

Turn

cc

Disconnect the line cord from the line voltage before opening the instrument. should be taken to avoid contact with line voltages at various points on the pc board when the line voltage cord is connected. disconnect the line cord and depress LINE.

To discharge voltage on capacitors

Care

6-11

IV~H,N I LNANCE

INSTRUCTION MANUAL

Digital Mullimeler

Models 172. 173

b.

Power Supply Check.

in Llt3E or BAT modes (if the Model

1. Set the internal Line Switch 5601 appropriately for the line voltage being used.

2.

Using DMM ( H ) measure the voltages listed in Table 6-10.

The following measurements can be made using the instrument

1728

is installed).

TABLE

6-10.

5V to +5.25V

+14.5 to +15.5

NOTE

To achieve calibration to published specifications the instrument should be calibrated using the Model 1725 Calibration Cover. The instrument should be allowed to stabilize for approximately 1 hour after the Calibration Cover is put in place.

It is important that the calibration sequence be followed exactly, because the ad-

justments are interrelated and dependent on prior calibration steps.

c. A/D Calibration.

NOTE

This procedure must precede

that

the

instrument will meet all rated specifications.

the

regular analog section calibration to ensure

1.

Capture Range Adjustments.

Set the DMM to MAN.

a) b) Set to 300mV DC.

Place a short between input HI and LO.

c)

d) Connect a Berg-type Z-pin housing (Keithley ~~-266) with approx. 30 inch leads

at TPlOl and TPl02 on PC-407 (See Figure 38).

Connect Oscilloscope (G) between the following points.

4

Oscilloscope Ext. TRIGGER to TPlOl (FON).

I.

Oscilloscope VERTICAL INPUT to TPIOZ (Prefilter).

2.

Oscilloscope GND to signal ground test point

3.

f) Set the Oscilloscope controls as follows:

1. Trigger: +, DC coupled. Vertical : DC, 0.5 V/division

2.

Time Base:

3.

For the following adjustments refer to trace shown in Figure 39.

9) h) Adjust potentimeter RI03 (AUTO CAL ACAL) for a level of +lV +O.ZV during

AUTO CAL time period.

20 ms/division

~1001~ (lo,.,).

AB

INSTRUCTION MANUAL Digltal Mulllmeler Models

172,173

IMPORTANT

When adjusting trimmer capacitors C203, C205, C817, C819, &20 and ~821 use an

insulated screwdriver to avoid shorting to the metal shield.

screwdriver should be rigid so that adjustments can be made with minimum backlash.

In addition the

MAINTENANCE

~803

ii .

Ii

c

ii C8,7

.-

51.

R8og

R9Oi

R8l6

~817

~819

R91 I

!I !

R913

h’

._

I

c82

C820

I

Model 173 is shown above (with Current Board Installed.) Model 172 has a In, Low Resistor (R514) mounted on the

metal shield (Not shown).

FIGURE 37.

AB 6-13

Location of Calibration Adjustments.

hlAlNTENANCE

Regulator VRb03 requires the use of heat sink assembly, Keithley part no. 28203~.

If the regulator must be removed, clearance. original condition to avoid a short circuit to the metal shield or other conduct-

ing surfaces adjacent

t’601

TPIOI

red

After a new regulator is installed,

to the reaulator.

bend the tabs on the heat sink to provide

bend the heat sink tabs to their

INSTRUCTION

MANUAL

Digital Mullimeler

Models 172. 173

,P603

P604

_ green

wire

TPIOi

black

J2Ol

Pi01

P605

P606

PYOI

P902

14

FIGURE 38.

Locations of Connectors and Test Points.

AA

INSTRUCTION MANUAL =

Dlgllal Multimeler Models 172,173

PREFILTER ,

OUTPUT

I AZi I

I

I I

ACAL ;

I

A22 I

I

~/y-

I I I

I

MAINTENANCE

SIGNAL INTEGRATION

I

FON j-----i

,I--120 ms~~*~200 ms-

Adjust potentiometer R20l (AUTO ZERO AZ,) for a level of +lV ?0,2V during

i)

period.'

AZ1

Adjust potentiometer R217 (AUTO ZERO AZ2) for a level of +lV ?O.ZV during

j)

A22 Period.

k) Repeat steps h,i, and j

I) Depress HI/LO ohms (Set to LO).

Release 2 WIRE/4 WIRE (Set to 2 WIRE).

m)

Set range to 3K ii.

")

I. Adjust potentiometer R707 ($2 BIAS) for a level of +IV +O.ZV during AUTO ZERO

AZ1 and AUTO ZERO A22 periods.

Adjust potentiometer R208 (0.3V Ref) fora level of +IV 10.2V during AUTO CAL

(A:AL) period.

until all levels are within IV ?0.2V simultaneously.

I_

3. Repeat steps I and 2 until both conditions are met simultaneously.

2. Zero and Offset Current Adjustments. Set the DMM to 300 mV DC range.

a) b) Place a short across INPUT HI and LO.

Record the reading on the DMM.

c)

d) Remove the short and connect the Test Circuit (H) across input HI and LO.

Adjust variable capacitor C203 (Input Current) to obtain the same reading as

e)

in step c) to within + 2 digits.

f) Remove the Test Circuit and replace the short.

Set the DMM to 2-WIRE and LO ohms.

9)

6-15

MAINTENANCE

h) Set range to 3 KQ.,

INSTRUCTION MANUAL

Digital Multimeter

Modelo172.173

i) Adjust variable capacitor C205 (OHMS zero) for a zero reading

on

the DMM. j) Set the DMM to 300mV DC. k) Adjust potentiwneter RYO4 (300 mV Zero) for a zero reading on the

DMM.

1) Verify that during the 200 ms INTEGRATION period the output at TP102 (Prefilter)

has no more than 10 transitions from positive slope to negative slope (and vice-versa).

d. DC Voltage Calibration.

(Depress DC, release V/A, depress AUTO/MAN.)

1. Zero Adjustments. Connect the DC Calibrator to the input terminals.

a) b) Set the instrument on the 300 mV range by using DOWN RANGE.

NOTE

It may be necessary to compensate for dc offset of the DC Calibrator.

For example,

if the dc offset is -2 uV dc then the DC Calibrator should be adjusted +2 uV to

compensate for the offset. Use a Keithley Model 155.

Set the DC Calibrator for’an output of +5 PV (see note above).

C)

d) Adjust the “300 mV ZERO” (RV04) f or a display which flashes between “-0” and

“+I”.

Set the instrument on the 30 V range.

e)

f) Set the DC Calibrator for an output of +.5 mV.

g) Adjust the “30 V ZERO” (R913) for a display which flashes between “-0” and “+I”.

2.

Full Range Calibration.

Connect the DC Calibrator to the input termillals.

a) b) Set the instrument to the range given in Table 6-11

Set the DC Calibrator to the output given in Table 6-11

C) d) Adjust the control given in Table 6-11to achieve the display specified.

NOTE

Perform the calibration in the exact order given.

TABLE 6-11

Full Range DC Calibration

rnge Setting Applied input Control Display Required”*

3 v

300 v +290.005 v 290 V ADJ (R911)

30 v

1200 v

+2.90005 v 2.9 V ADJ (R213) +2.9000 to +2.9001 v

+290.00 to +290.01 v +2g.o005 v X10 GAIN (R209) +Tooo.o5 v 1 KV ADJ (RYOI)

+29.000 to +29.001 v

+1000.0 to +1000.1 v

*The DC Calibrator output should be adjusted to compensate for dc offset voltage.

;+-L Display should flash alternately between readings.

6-‘6

I

cc

INSTRUCTION MANUAL

Dlgllal Multlmeler Modela 172.173

e.

AC Voltage Calibration.

1 .

Depress AC.

2.

Release V/A. Depress AUTO/MAN.

3.

4. Connect the AC Calibrator to the input terminals. Set the instrument to the range given in Table 6-12.

5. Set the AC Calibrator for the voltage and frequency given in Table 6-12.

6.

MAINTENANCE

Adjust the Control given in Table

7.

Lange Setting Applied Input

z-

ii

300 mv 010.00 mv

* 3 v

300 v

1000 v

;t;t

,ooo ” ;L;>t 3 v ?;A 300 v

1.0000 v I KHz

100.00 v 1 KHZ

1000.0 v 1 KH.;

1000.0

v

1.0000 v

100.00

v

Frequency

I KHz

20

KHz

20

KHz

20

KHz

6-12

to achieve the display specified.

TABLE 6- 12.

Control 1 KHz ADJ I KHZ ADJ (~803)

1 KHz ADJ (R816)

1 KHZ ADJ (11817) 20 KHz ADJ (C820, 20 KHz ADJ 20 KHz ADJ

(R8og)

(C819) (C817)

C821)

Display Required

009.99

0.9999

099.99

999.9

0.9999

99.99

to 010.01 mv to 1.0001 V to 100.01 v to 1000.1 v to 1000.1 v to 1.0001 v

to 100.01 v

14.

Connect the Oscilloscope to the test points shown in Figure 38. should be connected between power supply low and Oscilloscope low. should be connected between pre-filter output and Oscilloscope vertical input.

“red” wire should be connected between FON and the Oscilloscope trigger.

AB

The “green” wire

The “black” wire

The

6-17

1 f I\INTENANCE

INSTRUCTION MANUAL

Digital Mullimeler

Models 172, 173

Set the Oscilloscope to lV/div.

15.

Set the instrument to 3Kf1 range.

16.

Depress HI/LO Ohms and release 2 WIRE/4 WlRC.

17.

Connect a short across INPUT HI and LO.

18. AdjustO.PVREF (R208) for +lV tO.lV during Auto Cal.

13.

Verify that level is +lV kO.PV during Auto Zero.

20. until all conditions are satisfied.

Set the instrument to 3OOKn range. (HIQ)

21.

22.

Connect the Decade Resistor (0) to the upper set of terminals. Set the Decade Resistor to 290.000Kfi.

23.

Adjust the 290Kn ADJ (R704) for a reading of 230.00 fl diqit.

24.

Set the instrument to 3KQ range, HIR.

25.

Depress 2 WIRE/4 WIRE.

26.

Connect the 4-WIRE test cable between-the input terminals and Decade Resistor

27.

Set the Decade Resistor to 2.9000KR.

28.

Adjust the Z.PKn ADJ (R709) for a reading of 2.3OOOKn il digit.

29.

sensitivity and a time base of 20 ms/cm.

Repeat steps e.2 through e.20

I

Current Calibration (Model

9.

I. Depress DC.

2. Depress V/A. Depress AUTO/MAN.

3.

4.

Set the Model 173 to the 3 ampere range.

5.

Connect the Current Source (G) to the Model 173. Adjust the I A ADJ (R512) for a reading of 1.0000 A.

6.

Set the Model 173 to the 300 mA range.

7.

8.

Connect the Current Sourceto the Model 173.

Set the Current Sourcefor (A) for lOO.00 mA.

9. Adjust 100 mA ADJ (R509) for a reading of 100.00 mA.

IO.

Set the Current Sourcefor 10.00 mA.

II.

Adjust

12.

Current Calibration For Model 172.

h.

which determines accuracy is resistor R514 (In, 0.1X, IOU. Ww).

10

mA ADJ (R506) for a reading of 10.000 mA.

173

only).

No adjustments can be made.

Primary component

2

INSTRUCTION MANUAL

MAINTENANCE

Dlgllel Mulllmeler

Models 172,173

6-5.

fundamentals is needed to troubleshoot and repair the Model recommended that the user review the Theory of Operation (Section

Calibration procedure (paragraph

TROUBLESHOOTING AND REPAIR. An understanding of basic analog and digital circuit

6-4)

172/173.

before any attempt is made to repair the Model

It i5 strongly

5)

and the Adjustment/

172/173.

a. Troubleshooting Hints.

Component for a variety of possible malfunctions.

Instruction Manual to list all possible symptoms. Therefore, the Keithley represenative in your area should be contacted in the event repair is needed.

within the continental U.S.A. contact the factory for shipping instructions.

SYMPTOM

No display

a)

(LINE mode)

b) No display.

(BAT mode)

No display

c)

(Al I modes)

d) Display is blank.

or some segment on.

Table

PROBABLE CAUSE

I) Line switch set

2) Fuse FlOl is missing

3)

4) Batteries need recharg-

2) Battery fuses blown.

3)

4.

1) Display cable P3Ol not

2) LSI module improperly

3)

1) Clock waveform is miss-

6-13

Troubleshooting Hints

incorrectly.

or open.

Line voltage connector J601 improperly connected to pc board at ~601.

ing. indication.)

Batteries improperly

installed on battery pack. Battery cables improp-

erly installed.

properly connected.

installed.

Power supply malfunction

ing.

describes the Symptoms and Probable Faulty

It is beyond the scope of this

TABLE 6-13

(Check for LO BAT

For In-Warranty repairs

CORRECTIVE ACTION Check connection to line power.

Check LINE switch setting to conform to line voltage

available. See Figure

Check fuse. per rating. Check connection to DC board as shown in Figure 39,

Connect instrument to I

power. Check F401, F402, and F

Check battery pack for proper polarity on all batteries, See Figure 7 .

Check battery connections at

~602

Check plug P3Ol and mating connector J2Ol. al 1 pins are making proper contact (pins should not be bent). Check for proper orien-

tation of the connector Check UlO3 for proper installation. are making contact (pins

should not be bent).

Check power supply voltages as described in Section 6-4b.

Check pin 4 of LSI (UlO3) for a clock waveform of approx.

Release LINE.

and R606. as in Figure 7.

Make certain all pins

334 kHz,

and 0V.

LSI U103 is probably faulty.

If waveform is not present, integrated circuits UOO3, UO04.

transistor QO03, or ceramic

resonator CR003 may be faulty.

Reptace with pro-

Make certain

swinging between +4V

If waveform is present

36.

ine

403.

AA

6-19

,lAlNTENANCE

INSTRUCTION MANUAL

Digital Multimeter

Models 172. $73

JIOOI

6-20

FIGURE 40.

Plug-In Connections on PC-407

CB

INSTRUCTION MiNUAL

DIgItsI Multimeter Models 172,173

TABLE 6-13 (Con’t)

Troubleshooting Hinl

MAINTENANCE

ts

SYMPTOM

One display bar

e)

missing on all

digits.

f) One digit missing.

10,000 digit missing.

9)

(except if reading is less than 10,000

counts)

h) Function indicator

off.

Faulty reading on R

i)

function.

j) Faulty reading on

Current function.

PROBABLE CAUSE

1) Faulty connection between P3Ol and

f

JZOI. Cathode driver cir-

2)

cuitry faulty. schematic 27404D

Faulty connection

I)

between R30l and J2Ol. Anode driver circuitry

2)

faulty. See schematic

27404D.

Q301

Transistor Q306

DMM set for 4 WIRE

1)

ohms and R SOURCE

terminals are not

connected.

DMM set for 4 WIRE

2)

ohms, but leads are

reversed. Current fuse F5Ol

is blown.

see

CORRECTIVE ACTION

Check plus P3Ol and matins

connecior-J201.

f

all pins are making contact. “a” bar:

for signal. When "ON", voltage

should be approx. +l.8~.

"b" bar: Check R3O2 pin 16 "c" bar:

"d" bar:

'e" bar: "f" bar: Check R302 pin 10 "g" bar:

decimal point: Check R302 Check plug P3Ol and mating

connector JZOI.

If units digit missing, check collector of Q305 for signal.

When "ON"

approx. 418~.

If tens digit missing, check collector of 4304.

If hundreds digit missing, check collector Q303.

If thousands digit, minus sign and function indicator missing, check collector Q302. On 10,000 digit, check collec-

tor Q301. present problem could be tran-

sistor or integrated circuit u301.

Set to 2 WIRE.

Connect HI input to the same side of unknown as the + R

SOURCE lead.

Replace fuse on rear panel.

Check R3O2 pin 14

Check R3O2 pin ,l5 Check R3O2 pin 9 Check R302 pin I2

Check R302 pin 13

voltage should be

If no signals are

t4ake cergain

pin II

AA

6-21

INSTRUCTION MANUAL

I

Digilal

Multimeter

Models 172,173

b. How to Repair Circuits and/or Components Which Have a “Conformal Coat”. The

172/173 circuit board has a conformal coat which protects the circuit from moisture, and

lables the 172/173 to function over a range of environmental conditions.

The circuits and/or components are covered by a Conformal Coating manufactured by

I.

Dow Corning Corporation.

one-part silicone elastoplastic resin.

Parts coated with QR4-3117 coating can be repaired by either of two methods.

2. a) Apply a small amount of solvent (see below) and allow the coating to dissolve.

After cleaning, Coating.

b) For minor repairs, a soldering iron can be used to melt through the coating to

unsolder or resolder a component lead.

with Conformal Coating.

Cleaning may be accomplished using a small brush or cotton swab and solvent, such

3.

as FREON-TE, TOLUENE, XYLENE OR CHLOROTHENE.

Use solvent on circuit tape-side only.

Recoat with undiluted Conformal Coating using a small brush or other applicator.

4.

Shelf life of the coating material is approximately I2 months.

5.

coating material in order to maintain the properties of the material.

make the repair (unsolder component, etc.).

Dow Corning@ QR4-3117 Conformal Coating is a transparent,

Recoat with Conformal

After cleaning the soldered area, recoat

CAUTION

Solvent may adversely affect components.

Always use fresh

Model

The Conformal Coating is combustible. adequate ventilation.

ed skin contact. cable manufacturers data sheets.

Take necessary precautions when using cleaning solvents.

Avoid prolonged breathing of vapor. Avoid prolonged or repeat-

WARN I NG

Keep away from heat and open flame.

Use with See appli-

--22

AA

INSTRUCTION MANUAL

Digital MultImeter Models 172, 173

REPLACEABLE PA&S

I

SECTION

7-l.

parts list is arranged in alphabetical order of their Circuit Designations. 7-2.

replacement parts,

front cover of the catalog for addresses. When ordering, include the following infor-

mat ion.

7-3.

input switching,

designation series is 700, 800, and 900.

GENERAL.

ORDERING INFORMATION.

Instrument Model Number

a.

Instrument Serial Number

b.

Part Description

t.

Circuit Designation (if applicable)

d.

Keithley Part Number

e.

SCHEMATICS.

a.

Input Signal Conditioning. (28656E, Sheet I of

This section contains information for ordering replacement parts. The

To place an order or to obtain information concerning

contact your Keithley representative or the factory.

ac/dc conversion, filtering, attenuating, and ohms source.

REPLACEABLE PARTS

7.

3).

See the inside

This schematic describes the

Circuit

b. A/D Converter (28656E, Sheet 2 of 3).

digital converter and the range selection circuitry.

100, and 200.

c. Display (274040). This schematic describes the display driver circuitry. Circuit

designation series is 300.

her supply

d.

Circuit designation series is 600.

Battery Pack.)

e. Current Board (27478D).

the Models I72 and

f.

9.

cui try.

h.

cuitry.

i.

Model

Digital Interface, Bottom (27902E).

Digital Interface, Upper (28019E).

Timing Diagrams for Model 1722.

1728

Circuit designation series is 1000.

Circuit designation series is 1100.

(28656E,

173.

Rechargeable Battery Pack(26758C).

Sheet 3 of 3).

(See schematic

This schematic describes the current circuitry for both

Circuit designation series is 500.

(28247E, 28248E, 28249D) .

This schematic describes the analog-to-

Circuit designation series is 000,

This schematic describes the line power supply.

26758~

Circuit designation series is 400.

This schematic describes the Model 1722 cir-

for the Model 1728 Rechargeable

I

AB

( REPLACEABLE PARTS

MFR.

ICODE

NAME AND ADDRESS

1 ,A- B

Allen-Bradley Corp. Milwaukee, WI 53204

I

;A-D

AMP

Analog Devices Inc. Cambridge, MA 02142

T

Amp Inc. Harrisburg, PA I7105

TABLE 7-1

Cross-Reference of Manufacturers

FEDERAL

jUPPLY ZODE

II 121

24355

DO779

MFR.

CODE C

CLR

CTS

DIC

NAME AND ADDRESS

Clarostat Mfg. Co.. Inc. Dover, NH 03820

CTS Corporation Elkhart, IN 46514

Dickson Electronics Corp. Scottsdale, A2 85252

INSTRUCTION MANUAL

1

FEDERA

SUPPLY

CODE

12697

71450

12954

APH

APX

BEC

BLD

BRG

BRN

BUS

C-l

Amphenol

Broadview, IL, 60153 AlllperC%

Elkgrove Vlg, IL 60007

Beckman Inst. Inc. Fullerton, CA 9'2634

Belden Mfg. Co. Chicago, IL 60644

Berg Electronics Inc. New Cumberland, PA 17070

Bourns, Inc.

Riverside, CA 92507

Bussman Mfg. Div. St. Louis, MO 63017

Components, Inc. Biddeford, ME 04005

02660

73445

73138

70903

22526

30294

71400

36751

DTN

ECI

EDI

EFJ

ERI

F- I

FUS

G-E

Dielettron (Consolidated) New York City, NY IO013

Electra Cube Inc. San Gabriel, CA VI776

Electronic Devices Inc. Yonkers, NY 10710

E F Johnson Co. Waseca, MN 56093

Erie Technological Prod. Erie, PA 16512

Fairchild lnst Corp.

Yountain VieW,CA 94043

Bussman Mfg. (Fusetron) St. Louis, MO 63107

General Electric Company Syracuse, NY 13201

14752

74970

72982

07263

71400

03508

c-w

CAD

CAN

CLB

-

Continental-Wirt Elec. Corp.

Warminster, PA 18974

Caddock Riverside, CA 92507

ITT Cannon Electric

Santa Ana, CA 92702

Centralab Division

Milwaukee, WI 53201

79727

I9647

71590

--

-.+-

G-I

GLD

H-P

DLE

General Instrument Corp. Newark, NJ 07104

Gould, Inc. St. Paul, MN 55165

Hewlett-Packard Palo Alto, CA 94304

Dale Electronics Inc. Columbys, NE 68601

726%

52431

50434

91637

.

INSTRUCTION MANUAL

Dlgllal Mulllmeler

Model8 172. 173

AEPLACEbLE PARTS

MFR.

CODE NAME AND ADDRESS

INT lntersil Inc.

Cupertino, CA 95014

I RC IRC Division

Burlington, IA 52601

<- I Keithley Instruments, Inc.

Cleveland, Ohio 44139

.-F

$OL Holex

10T Motorola Semi Prod. Inc.

Littlefuse, Inc.

Des Plaines, IL 60016

Downers Grove, IL 60515

Phoenix, AZ 85008

TABLE

FEDERAL

SUPPLY CODE

32293 Manchester, NH

07716

80164

75915

27264

04713

7-l

(Cont'd)

MFR. CODE NAME AND ADDRESS

RCL

SIE

SIG

SIL

SPG

T-l

RCL Electronics, Inc.

Siemens Corporation

Iselin, NJ

Signetics Corp. Sunnyvale, CA 94086

Siliconix Inc. Santa Clara, CA 95054

Sprague Electric Co.

Visalia, CA 93278

Texas Instruments, Inc. Dallas, TX 75231

08830

03102

FEDERAL SUPPLY CODE

01686

j

25088

18324

17856

14659

01295

IAT National Semi Corp.

Santa Clara, CA 95051

'68

'AK

'OM Pomona Electric

UN

IAY Raytheon Company

{CA

Potter & Brumfield Princeton, IN 47670

Paktron Vienna, VA

Pomona, CA 91766 Q-Tron

Santa Ana, CA 92705 Laconia, NH 03246

Quincy, MA

RCA Corporation

tloorestown, NJ 08050

22180

27014

05276

94144

02734

TEP

TPL

TRW

VIS

VRN

WAB

Tepro Electric Corp. Rochester, NY 14606

Temple Tecate, CA 92080

TRW Capacitor Div. Ogallala, NB 69153

Vishay Resistor Products

Malvern, PA 19355

Vernitron

Wabash-Magnetics

Wabash, IN 46992

02985

29505

844

II

18612

13150

01101

AB

7-3

IEPLACEABLE PARTS

INSTRUCTION MANUAL

Digital M”ltime‘er

Models 172.173

BATTERIES (ET)

"400" SERIES (Schematic 26758C)

rircuit Mfr.

esig. Description Code

BT40l

-T402 Multicell~ lP.ZV, NickE T403 set of Seven "C" cells, 8.4

:i

irccit

esig. Description' Code Desig. Part

COOI

002 0.1 "F, 16V, CerD.

003

coo4 0.1 PF, 16V, CerD.

-005 006

coo7 O.oluF, 16v, CerD. ~008 0.01 uF, 16v, CerD

009

LO10

Multicell.

Nickel-Cadmium, "C" ccl

volts (used for BT403; seven

required) . . . . .

0.1 IIF, l6V, CerD.

0.1 PF,

0.1 uF, 16V, CerD. 33pF, IOOOV, Cero

2.2 uF, 2OV, ETT

0.47pF, SW, Cer Film

lP.ZV, Nickel-Cadmium

!I

"000" SERIES (Schematic 28656E)

........

16v, CerD. ........

........

.........

GLD

-Cadmium

GLD

volts -- --

I

, 1.2

. . . . .

CAPACITORS (C)

GLD

Mfr. Mfr.

CLB CLB CLB CLB CLB CLB CLB CLB C-l

ERI

Mfr.

Desig.

403041 403041

2.OSCB

~~16-104 ~~16-104

~~16-104 ~~16-104 U~l6-104 DD-330 UKl6-103 UKl6-103 TDl-20-225-20

813l050651474~

Keithley Part No.

BA-31

BA-jl

:’

BA-30

Keithley

Nc.

C-238-.lh C-238-.IM

C-238-.lM

C-238-.IM C-238-.ln C-64-33~

c-238-.01" C-238-.OIM

C-179-2.2" C-237-0.47t'

"100" SERIES (Schematic 28656E)

Cl01 0.1 "F, l6v, CerD.

102

-103 0.1 pF, 16v, CerD.

Cl04

105 106

Cl07 .0022 ,,F, ZOOV, My, 10%

'108 0.01 pF, loov, My! lo%

109 Cl10 Clll

:I I2

cll3

Cl14

:\I5

7-4

0.1 ,,F, 16~. CerD.

0.1 uF, 16v, CerD.

0.1 uF, I~v, CerD.

0.022 pF, 5OV, MPC

33 pF, IOOOV, CerD

0.1 uF, 16v, CerD.

0.1 "F, l6v, CerD.

0.22 PF, 5OV, MPC.

0.22 uF, 5OV, MPC.

0.22 "F, 5OV, MPC.

8.2 pF. 50~. Ce,-

........ CLB

........

........ CLB

........

........ CLB

........

......

~~16-104

CLB

ECI

E-C

PAK

CLB CLB

ECI ECI

ECI

CLB C40c8R2~

~~16-104

U~l6-104

uKl6-lo4

625BlA223-J

6258l~222 PT420

DD-330 ~~16-104 ~~16-104 625BlA224J 625BlA224J 625BlA224J

C-238-.IH C-238-.ltl

C-238-.IH C-238-.ltI C-238-.IH C-ZOI-.022M

C-ZZI-.0022M C-38-.OlM

C-64-33P C-238-.ln C-238-.ln C-20l-.22H C-ZOI-.22M c-ZOI-.22t4 C-282-8.2~

AB

Keithley 1728, 1722, 173, 172 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual