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

@COPYRIGHT 1976, KEITHLEY INSTRUMENTS, INC.

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

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173

ONLY).

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* .

: : : : : : :

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....

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.. ii

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. I-l
. l-1

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. 1-l
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. . . 3-11

. . . . 3-12

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* . . .

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. 5-9

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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.

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

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

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

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

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

I

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