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Models 172A, 173A
Instruction Manual
Contains Operating and Servicing Information for the
Models 172A, 173A Digital Multimeter
Publication Date: August 1978
Keithley Instruments, Inc.
Instrument Division
Cleveland, Ohio, U.S.A.
Document Number: 29662, Rev. B
INSTRUCTION MANUAL
Digltal Multlmster
Models 172A. 173A
INSTRUCTION MANUAL
Digital Multimeter
MODELS 172A/173A
COPYRIGHT 1978, KEITHLEY INSTRUMENTS, INC.
PRINTEU APRIL, 1981, CLEVELAND, OHIO, U.S.A.
DOCUMENT NO. 29662, REV. B
INSTRUCTION MANUAL
DigItal Mulllmrtw
Mod.1~17ZA. 173A
CONTENTS
,ction Page
INTENTS ......................................
.LuSTRATIoNs ...................................
GENERAL INFORMATION .............................. I-l
l-l. INTROOUCTION. .............................. 1-I
l-2. FEATURES ................................. l-1
l-3. WARRANTY INFORMATION. .......................... l-l
I-4. CHANGE NOTICE .............................. I-I
l-5. OPTIONAL MODEL 1728 RECHARGEABLE BATTERY PACK .............. l-1
1-6. OPTIONAL MODEL 1722 DIGITAL INTERFACE .................. I-I
1-7. OPTIONAL MODEL 1723 IEEE STANDARD 488 BUS INTERFACE ........... I-1
IECIFiCATIONS. .................................. I-'
INITIAL PREPARATION .............................. 2-l
2-1. GENERAL ................................ .2-l
2-2. INSPECTION. ............................... 2-l
2-3. PREPARATION FOR USE ........................... 2-I
OPERATING INSTRUCTIONS. ............................ 3-l
3-l. GENERAL .............................. ..3- 1
3-2. HOW TO SELECT POWER ........................... 3-l
HOW TO SELECT FUNCTION. ......................... 3-2
;I;' HOW TO SELECT RANGE ........................... 3-3
3-5: HOW TO MEASURE VOLTAGE. ......................... 3-4
3-6. HOW TO MEASURE CURRENT. (MODEL 172A ONLY) ................ 3-5
3-7. HOW TO MEASURE CURRENT. (MODEL 173A ONLY) ................ 3-6
3-8. HOW TO MEASURE RESISTANCE ........................ 3-7
3-9. FURTHER MEASUREMENT CONSIDERATIONS. ................... 3-8
3-10. HOW TO USE MODEL 172A/l73A OFF-GROUND .................. 3-11
3-11. HOW TO USE OPTIONAL PROBES AND SHUNTS .................. 3-12
3-12. HOW TO USE THE MODEL 1722 DIGITAL INTERFACE ............... 3-13
3-13. COMMENTS RELATIVE TO THE MODEL 172A/l73A SPECIFICATIONS ......... 3-25
3-14. MODEL 1728 OPERATING Tips if:;5
. ACCESSORIES. .. ..... ..................................................
4-1. GENERAL..................................4- I
4-2. POWER OPTIONS .............................. 4-l
4-3. ISOLATED DIGITAL OUTPUT ......................... 4-1
4-4. RACK MOUNTING .............................. 4-i
4-5. PROBE AND SHUNTS. ............................ 4-4
4-6. CABLES AND CONNECTORS .......................... 4-5
4-7. MISCELLANEOUS .............................. 4-5
THEORY OF OPERATION .............................. 5-l
. 5-l. GENERAL.................................5- I
5-2. OVERALL OPERATION ............................ 5-l
5-3. INPUT SIGNAL CONDITIONING ........................ 5-l
5-4. A/O CONVERTER AND DIGITAL CIRCUITS (SCHEMATIC 29145E, SHEET 2). ..... 5-15
5-5. DISPLAY BOARD, SCHEMATIC 274040 ..................... S-21
5-6. POWER SUPPLY, SCHEMATIC 29145E. ..................... 5-21
MODEL 1728 RECHARGEABLE BATTERY PACK, SCHEMATIC 26758C. ......... 5-23
MODEL 1722 DIGITAL INTERFACE. ...................... 5-25
I
ii
INSTRUCTION MANUAL
Digital MultImeter
Models 172A. 173A
CONTENTS (CON'S)
iect ion Page
;. MAINTENANCE. ;I;
6-i. GENERAL ...................................................................
6-2. REQUIRED TEST EQUIPMENT. ........................ 6-l
PERFORMANCE VERIFICATION ........................ 6-l
CALIBRATION REQUIREMENTS ........................ 6-7
6-5. PREPARATION FOR CALIBRATION. ...................... 6-8
6-6. CALIBRATION PROCEDURE. ......................... 6-Y
6-7. TROUBLESHOOTING AND REPAIR ....................... 6-15
FUSE REPLACEMENT ............................ 6-21/Z
6-8.
7. REPLACEABLE PARTS. .............................. 7-1
7-l. GENERAL.................................7- 1
7-2. ORDERING INFORMATION .......................... 7-I
7-3. FACTORY SERVICE. ............................ 7-l
7-4. REPLACEABLE PARTS LIST ......................... 7-l
CROSS REFERENCE OF MANUFACTURERS .................... 7-2
COVERS AND PANELS. ........................... 7-2
COMPONENT DESIGNATIONS FOR ~~-446. ................... 7-2
7-a. SCHEMATICS ............................... 7-2
7-Y. COMPONENT LAYOUTS. ........................... 7-2
7-10. SPARE PARTS KIT. ............................ 7-5
iii
INSTRUCTION MANUAL
Digital MuItlm*ter
Mod&172A.l73A
ILLUSTRATIONS
GURE NO. TITLE PAGE
1-l Model l73A Front Panel ....................... 1-3
l-2 Bottom View Showing Line Cord. ................... l-4
l-3 Tilt Bail Positions. ........................ l-5
l-4 Dimensional Data .......................... 1-6
2-l Rear Panel Showing Current Fuse. .................. 2-2
2-2 Model 1728 Rechargeable Battery Pack ................ 2-4
2-3 Installation of Battery Pack .................... 2-5
Front Panel Pushbutton Selection .................. 3-3
;:: Typical Model 172A Current Display (DCnA). ............. 3-5
Typical Model l73A Current Display (ACmA). ............. 3-6
::i Typical 2 WIRE Resistance Measurement. ............... 3-7
Typical 4 WIRE Resistance Measurement. ............... 3-V
;:; Semiconductor Diode and Transistor Testing ............. 3-10
3-7 Use of Multimeter Off Ground .................... 3-11
3-a Model 1722 Digital Output Interface. ................ 3-14
3-9 Installation of Model I722 ..................... 3-15
3-10 Connector Pin Identification For ~1006 and PllOl .......... 3-17
3-11 Card-Edge Connectors (Model 1727 Cable Set). ............ 3-17
3-12 Location of Jumpers and Pull-ups on Model 1722 ........... 3-18
4-l Model 1010 Single Rack Mounting Kit. ................ 4-2
4-2 Model 1017 Dual Rack Mounting Kit ................. 4-4
5-l Overall Block Diagram of Model 172A/l73A .............. 5-2
Simplified Block Diagram of Signal Conditioning Circuits 5-2
::; Simplified Schematic of DC Attenuator. ..... ................ 5-6
5-4 Simplified Schematic of AC/DC Converter. 5-7
5-5 Simplified Schematic of 173A I/V Converter 5-8
5-6 Simplified Schematic of Model l72A I/V Converter ..................................... 5-8
5-J Simplified Ohms Converter, Two-Wire Ohms Configuration ....... 5-10
5-a Four-Wire Ohms Measuring Technique ................. 5-10
5-9 Simplified Schematic of Clamp. ................... 5-12
5-10 Simplified Schematic of Active Filter. ............. ., . 5-12
5-11 Simplified Block Diagram of A/D Converter. ............. 5-14
5-12 A/D Converter System Timing .................... 5-15
Simplified Schematic of A/D Buffer 5-16
;:;; Simplified Schematic of the A/D Converter, .............................. 5-17
Simplified Schematic of 669 kHz Oscillator 5-19
:I;; Simplified Schematic of Reference Supply ........................... 5-20
Digital Display Multiplex Scheme 5-22
::g Model 1722 Block Diagram . ....................................... 5-24
6-l Location of Calibration fidjustments. ................ 6-10
6-2 Location of Connectors and Test Points ............... 6-14
J-1 TOD and Bottom Cover Assembly ................... 7-3
iv
INSTRUCTION MANUAL GENERAL INFORMATION
Digital Multimeter
Models 172A. 173A
-~-
SECTION 1. GENERAL INFORMATION.
I-l. INTROOUCTION. Thk Models, l72A and 173A Digital Multimeters are wide-range, general-
purpose measuring instruments, capable of measuring ac/dc voltage, ac/dc current and
resistance. (See Table 1-I for Specifications, Page l-2).
l-2. FEATURES.
a. Automatic Ranging and Polarity.
b. Manual Range Selection and Range Hold.
c. HI and LO Ohms Capability.
d. Line Operation.
e. Optional Battery Operation, Model 1728.
f. Floating Capability to +14OOV peak.
9. Optional Isolated Digital Interface, Model 1722/1723.
1-3. WARRANTY INFORMATION. The warranty is stated on the inside Front cover of the
manual. If there is a need for service, contact your Keithley representative or author-
ized repair facility as given in our catalog.
l-4. CHANGE NOTICE. Improvements or changes to the instrument not incorporated into
the manual will be explained on a change notice sheet attached to the inside back cover
of the manual.
l-5. OPTIONAL MODEL 1728 RECHARGEABLE BATTERY PACK. The Model 1728 is an accessory
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 172A/l73A chasis.
l-6. OPTIONAL MODEL 1722 DIGITAL INTERFACE. The Model 1722 is a field-installable
digital output option. It provides isolated open-collector ECD outputs and control lines.
1-7. OPTIONAL MOOEL 1723 IEEE STANDARD 488 BUS INTERFACE. The Model 1723 is a field-
installable digital interface option that provides logic and control functions necessary
to make the Model 172A or l73A bus compatible in accordance with the IEEE Standard 48B-
1975. Refer to the Instruction Manual for Model 1723 for operation and service instruction!
for this option.
IMPORTANT
The A Symbol can be found in various places in this Instruction Manual. Care-
fully read the associated CAUTION statements with regard to proper use and handling
of the instrument. Damage to the instrument may occur if these precautions are
ignored.
The \ symbol can be found in various places in this Instruction Manual. This
symbol indicates those areas on the instrument which are potential shock hazards.
Carefully read the associated WARNING statements with regard to proper use and
handling of the instrument. Serious personal injury may result if these pre-
cautions are ignored.
l-l
GENERAL INFORMATION INSTRUCTION MANUAL
Digital Multimet*r
Models 112A,. 113A
TABLE 1-1.
SPECIFICATIONS
INSTRUCTION MANUAL GENERAL INFORMATION
Digital Multimeter
Models 172A. 173A
--
FUNCTION AND UNITS DISPLAY (mV)
I INPUT HI AND LO. UPPER PAIR
FIGURE l-1. Model 173A Front Panel.
1-3
IN= I nub I I"N MANUAL
Digital Multimeter
Models 172A. 173A
r TEST POINT "A"
FIGURE l-2. Bottom View Showing Line Cord.
1-4
INSTRUCTION MANUAL GENERAL INFORMATION
Digital Multimster
Models 172A. 173A
c -I I I
NORMAL BENCH POSITION LEVEL POSITION - TILTBAIL AT FRONT
HANGING POSITION
4% 45" POSITION
-I
LEVEL POSITION - TILTBAIL AT REAR
y
FIGURE l-3. Tilt Bail Positions.
GENERAL INFORMATION INSTRUCTION MANUAL
Digital Multimeter
Models 172A. i73A
O~MENSIONS
ht
IN MILLIMETERS (INCHES)
5,-----l
FIGURE l-4. Dimensional Data
1-6
INSTRUCTION MANUAL INITIAL PREPARATION
Digital Multimeter
Models 172A. 173A
SECTION 2. INITIAL PREPARATION.
2-i. GENERAL. This section provides information needed for incoming inspection and
preparation for use.
2-2. INSPECTION. The Model 172A/173A was carefully inspected both mechanically and
electrically before shipment. Upon receiving the instrument, clieck for any obvious dam-
ages which may have occurred during transit. Report any damages to the shipping agent.
To verify the electrical specifications, follow the procedures given in Section 6.
2-3. PREPARATION FOR USE. The Model 172A/l73A is shipped ready-to-use. The instrument
can be powered from line voltage or from rechargeable nickel-cadmium batteries (when the
optional Model 1728 Rechargeable Battery Pack is installed).
a. Line Power. The Model 172A/l73A has an attached three-wire line cord which mates
with third-wire grounded receptacles (NEHA 5-l5P). The permanently installed line cord
is stored by wrapping the cord around the base of the instrument as shown in Figure 4.
CAUTION
This instrument has an internal line power selector switch that must be set
A to 234V position for operation above 125 volts rms, 50-60 Hz.
I. How to set the Internal Line Voltage Switch (S6Ol). The Model 172A/l73A has a
two position slide switch located on the main circuit board. For operation above 125
volts, the switch setting and fuse must be changed. The top cover must be 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.
Line voltage is present at various points on the circuit board and represents
t a SHOCK HAZARD.
NOTE
Optional line voltage range is available when wiring modifications are made to
transformer T60l as shown on schematic 29145E.
TABLE 2-l.
Summary of Standard and Optional Line Voltages.
----~ I I
I
1 105 to
Standard
125 V rms 90 -
opt1 -nab
105 V rms - Transformer wiring
must be modified.
210 to 250 V rms
/
2-l
INITIAL PREPARATION INS: I ItUG I ION MANUAL
oigwd MYlllnle*er
Models 172A. 173A
FUSE F501
FIGURE 2-l. Rear Panel Showing Current Fuse.
2-2
INSTRUCTION MANUAL INITIAL PREPARATION
Digital Multimeter
Models 172A. 173A
2. Line Fuse Requirement. The Model 172A/l73A uses a single line fuse to protect
the line-operated power supply. The fuse is a 3 AB or 3 AG, slow-blow type. Rep lace
with I/4 ampere for II7 volts operation or l/8 ampere for 234 volrs.
IMPORTANT
A Replace fuse with correct rating, otherwise, damage to the instrument could result.
3. How to Replace the Line Fuse. The fuse is installed on the main circuit board
as shown in Figure 6-2 (Page b-14). The top cover must be removed to gain access to
the circuit board as described in Section 6. Use Keithiey FU-I7 (l/4A) for II7 V;
FU-20 (1/8A) for 234V.
WARNI NG
Disconnect the line cord before removing the top cover of the instrument. `Line
voltage is present at various points on the circuit board and represent a SHOCK
t HAZARD.
CAUT I ON
The fuse installed on the rear panel
of the Model 172A/l73A is used only for
A current range protection. is -not a line
This fuse voltage protection fuse.
b. Battery Power. To operate the Model 172A/l73A from batteries, the Model 1723
Rechargeable Battery Pack must be installed. The /*ode1 1728 can be either field or
factory-installed (at the time the Model 172A/l73A is purchased).
NOTE
The Model 1728 Rechargeable Battery Pack can be installed by the user within me
Model 172A/l73A at any time. However, if the Model I722 Digital Output is
already installed, the Model 1728 cannot be used simultaneously.
I . How to Install the Model 1728 Rechargeable Battery Pack. The batteries furnisnec
with the Model 1728 are already installed in the battery pack. The battery pack in-
cludes 7 rechargeable "C" cells (l.2V, 2 AMP Hr) and two 19.2 volt packs (sixteen I.?`/-
cells per pack). See Figure 2-3.
=) Check the fuses on the Battery Pack. Three fuses are used. All are I ampere,
3AB or 3 AG, Slo-Blo types, Keithley Part Ho. FU-IO.
b) Check for proper installation of batteries in the Battery Pack. If reolace-
ment battery cells are to be insYalled, be certain to observe the proper polarity
of the individual cells as shown in Figure 2-3.
C) To install the Battery Pack, turn the instrument over so that the bottom cover
faces up. Loosen four slotted screws on the bottom cover. The screws are captive,
that is they cannot be removed completely. Turn over the instrument with the top
cover facing up, taking care to hold the top and bottom covers together. Carefully,
remove the top cover to gain access to the printed circuit board. There is a
connection between the top cover and the main circuit board which must be temporaril
removed in order to free the top cover. Check to see that the four insulating
spacers are in position on the circuit board as shown in Figure 2-3. Plug tile two
s-wire connectors (J401, J402) into the mating receptacles (P4Ol , ?402) taking care
to orient the connectors as shown. Place the Model I728 in position on tne spacers
with the pack oriented as shown in Figure 2-3. Replace the connector from the top
cover to the circuit board. Replace the top cover. Turn over t,\e instrument iiith
the bottom cover facing up and tighten down the four slotted-head screws.
2-3
INIT!AL PREPARATION INSTRUCTION MANUAL
Digital Mullimatsr
Models 172A. 173.4
J401
J402
FIGURE 2-2. Model 1728 Rechargeable Battery Pack.
2-4
INSTRUCTION MANUAL INITIAL PREPARATION
Digital Multimeter
Models 172A. 173A
WARNING
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.
FIGURE 2-3. Installation of Battery Pack.
2-5
INITIAL PREPARATION INSTRUCTION MANUAL
Digital Multimeter
Models 172A1.173A
TABLE 2-2.
SummarY of Batteries Used in the Model 1728
Description Quantity Voltage Keithley Part NO.
I 2v "C" cell
(; AMP-HR) 7 8.4~ BA-30
+19.2V pack
I +19.2v BA-31
(I&1.2v cells)
-19.2V pack,
I -19.2v BA-31
(16-1.2V cells)
CAUTION
The Model 1728 is shipped from the factory in an uncharged condition. There-
A fore, the pack should be installed in the Model 172A/l73A and charged prior to
"Se.
2. How to Check Batteries.
a) The Model 172A/l73A has a built-in LO BAT indicator to permit easy determination
of battery condition. The Model 172A/l73A also has an indivicuai test point on the
bottom panel usually needed only for troubleshooting purposes 'See Figure l-2).
b) The LO BAT indicator will be lighted when the Battery Pack goes be .orma I
operating voltage. When the indicator turns on, the Model 172A/l73A shouio oe switched
to LINE or OFF to permit recharging of the Pack.
C) The test point may be checked at any time using the Model l72A/173A or other
measuring instruments. The voltages are summarized in Table 2-3.
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. If the voltage is measured when the Model 172A/l73A is
operated in the LINE mode, a different reading may be observed since the batteries
are being charged.
TABLE 2-3.
Summary of Battery Voltage Levets (BAT mode)
I Test Acceptable Battery Levels Recharge Battery 1
Point Range Norma I If Below Tested
I I I I
I
4`AlI
I igv + +20.5v 19v I BT402
I
3. How to Charge the Batteries. The Model 1728 provides built-in recharging cir-
cuitry. The Model 172A/l73A must be connected to line voltage. Recharging occurs at
the most rapid rate when the Model 172A/l73A is set to OFF. Typically, the recharge
time is 2.5 hours per hour of discharge. After the batteries have been fully charged,
eithhr turn the instrument on with the LINE switch (trickle charge condition) or dis-
connect the line cord to prevent overcharging of the batteries.
CAUTION
Overcharging the batteries will raise the internal temperature of the battery
pack and may shorten the life of the batteries.
2-6
INSTRUCTION MANUAL OPERATING INSTRUCTIONS
Digital Multimeter
Models 172A. 173A
SECTION 3. OPERATING INSTRUCTIONS
3-l. GENERAL. This section provides information needed to operate the tlodel l72A/iJjh
for measurement of voltage, current and resistance.
3-2. HOW TO SELECT POWER. The Model 172A/l73A may be powered from line voltage or re-
chargeable nickel-cadmium batteries (when the Model 1728 is installed). The Model 172.V
lJ3A hasa built-in line-voltage power supply and power cord.
NOTE
The accessory Model 1728 Recharqeable Battery Pack may be ordered at the time of
purchase of the Model lJ2A/lJ3A or may be purchased and field-installed at a later
time if so desired. The Model 1728 features plug-in wiring and, as a result, no
modifications need to be made to the Model lJ2A/l73A chassis,
a. How to Operate from Line Power. The Model I JZA/lJjA can be powereo from I ine volt-
age over four ranges from a minimum of 90 V rrn5 to a maximum of 250 V vs. Table 5-i
summarizes the line voltages permitted.
I. Set the internal line voltage switch to either ll7V or 234V.
2. Plug the line cord into source of line power.
3. Depress LINE pushbutton.
NOTE
Power on will be indicated by a lighted display with one or more digits and mea-
surement unit showing.
TABLE 3-1.
How to Set Line Voltage
b. How to Operate from Battery Power.
I Install the Model 1728 Rechargeable Battery Pack. (See Section 2, page 2-3.)
2. Depress BAT pushbutton.
3. If LO BAT indicator is lighted, the battery pack must be charged a minimum of 16
hours to provide fully charged operation of the Model l72A/l73A.
NOTE
To charge the Model 1728, release both LINE and BAT pushbuttons and connect rhe
line cord to line power. If it is desired to use the Model lJ2A/lJ3A immediately,
depress LINE. The Model lJZA/l73A will be useable for measurements although the
battery charging rate is decreased considerably.
4. If the LO BAT indicator is not lighted in BAT mode,the model 172A/173A maY be
used for measurements.
3-l
OPERATING INSTRUCTIONS INSTRUCTION MANUAL
Digital MultImeter
Models ,72A. 173A
NOTE
The Model 1728 is shipped from the factory in uncharged condition. Therefore the
Model 1728 should be installed and charged prior to use. After the Model 1728 has
been charged for at least 16 hours, the Model 172A/l73A can be powered continuously
for at least 6 hours.
TABLE 3-2.
Summarv of Ooeration in LINE and BAT Modes
I Line Power Connected
Condition
Line
of
Power Connected
Instrument
Line Power Not Connected
1
Button Depressed 1728 npt installed 1728 installed 1728 installed
LINE ON ON OFF
Battery trickle charged.
BAT OFF ON ON
Battery slowly discharged.
NEITHER OFF OFF OFF
LINE NOR BAT Battery charged at max-
3-3. HOW TO SELECT FUNCTION. Function is selected by means of four pushbuttons: DC/AC,
V, A and R.
a. v. This pushbutton must be used with DC/AC to select either DC voltage or AC
Voltage.
I. DC Voltage. Depress V. Release DC/AC.
2. AC Voltage. Depress V. Depress DC/AC.
b. A. This pushbutton must be used with DC/AC to select either DC current or AC
current.
I. DC Current. Depress A. Release DC/AC.
2. AC Current. Depress A. Depress DC/AC.
c. DC/AC. This pushbutton selects whether the selected voltage or current Function
will be AC or DC. When depressed, AC is selected.
d. R. Depress R to measure resistance.
NOTE
V, A, and R pushbuttons are interlocked so that only one pushbutton is 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. (The volts or
millivolts indicator will be lighted in this instance.) R overrides DC/AC. v or
A overrides HI/LO and 2 WIRE/4 WIRE.
3-2
INSTRUCTION MANUAL OPERATING INSTRUCTIONS
Digital Multimeter
Models 17'2A. ,73A
FIGURE 3-l. Front Panel Pushbutton Selection.
3-4. HOW TO SELECT RANGE. The Model 172A/l73A provides automatic or manuai ranging.
The AUTO/MAN pushbutton determines the ranging mode, where AUTO = fully automatic
ranging.
a. AUTO. When released, the Model l72A/173A automatically selects the appropriate
range in accord with the following rules.
I. When the display exceeds 29999 the Model lj'2A/l73A upranges (that is. it changes
to less sensitivity and the decimal point moves appropriately).
2. When the display reaches 02599 the Model 172A/l73A downranges (that is, it
changes to greater sensitivity and the decimal point moves appropriateiy).
b. MAN. When depressed, the range is placed to hold. The user can cause the Model
172mto uprange or downrange by using the UP RANGE and DN RANGE pushbuttons.
I. When DN RANGE is momentarily depressed, the Model 172A/i73A will downrange one
decade of sensitivity. Each time the pushbutton is depressed and released, one down-
range will occur until most sensitive range is obtained.
2. When UP RANGE is momentarily depressed, the Model 172A/l73A will uprange one
decade of sensitivity. Each time the pushbutton is depressed and released, one uprange
will occur until least sensitive range is obtained.
3-3
OPERATING INSTRUCTIONS INSTRUCTION MANUAL
Digital Multimeter
Models 172A. 173A
?-5. HOW TO MEASURE VOLTAGE. The Model 172A/l73A measures ac and dc voltage in five
ranges : 0.3v, 3V, 3OV, 300V and \zOOV DC (IOOOVAC).
CAUTION
Maximum input voltage depends on the range selected. Table 3-3 gives the maximum
allowable continous input for each range on AC and DC. Do not exceed these volt-
A ages or damage to the instrument will occur.
TABLE 3-3.
Maximum Allowable Continuous Input
Range AC Voltage (ACV) DC Voltage (DCV)
0.3v 1000v rms 1200V peak"
3 v 1000v rms 12OC'v peak*
30 v IOOOV rills 12OOV peak
300 v 1ooov rnls 12OOV peak
1000 v IOOOV rms 12OOV peak
*Overload on manual range not to exceed 600 volts continuous or 1200~ for 3 seconds.
The Model \72A/l73A detects dc voltages from i10 microvolts/digit to
,l%$&?%%.O display). The maximum display is 29999. When the display exceeds
pggg, a 3 remains lighted, but all other digits are blanked. The display blinks above
1199.9 volts on the highest range.
I. Set to DC Volts.
2. Set to AUTO.
3. Connect the Signal to be measured between HI and LO terminals. (The terminals
are designed to accept banana style plugs, such as Keithley part no. BG-5 or accessory
test leads such as Model 1681 Clip-On Test Leads.)
4. Observe the displayed digits, polarity sign, decimal point location, and measure-
ment unit (mV or V). If no polarity sign is indicated, a positive polarity is implied.
b. AC Voltage. The Model iJ2A/i73A detects ac voltages from 10 microvolts rms to 1000
volts (1000.0 display). The maximum display is 29999. When the display exceeds 29999,
a 3 remains lighted, but all other digits are bianked. The display blinks above 999.9
volts on the highest range.
I. Set to AC Volts. (The AC indicator should be lighted.)
2. Set to AUTO.
3. Connect the signals to be measured between HI and LO terminals. (The terminals
are designed to accept banana style plugs, such as Keithley part no. BG-5 or accessory
test leads such as Model 1681 Clip-On Test Leads.)
4. Observe the displayed digits, decimal point location, and measurement unit (mV
or V).
3-4
INSTRUCTION MANUAL OPERATING INSTRUCTtONE
Digital Multimeter
Models 172A. 173A
3-6. HOW TO MEASURE CURRENT. (MODEL 172~0~~~). The Modell72A measures ac and dc current
in two ranges: 0.3A, and 2A. The current is limited by the current fuse even thouqh the
DMM is capable of displaying 2.9999A.
CAUTION
The Model 172Ais protected by a 2 ampere fuse on all ranges. If the fuse is blown,
A a replacement Keithley Part No. FU-13 should be installed in the rear panel fuse
holder. (See Figure 2-l).
a. DC Current. The Model 172Adetects dc currents from ?I0 microamperes/digit to r2
amperes. When the input exceeds 2 amperes, the current fuse will blow. When using the
MAN mode it is possible to select 30A, 300A t 3000A Ranges,but2A Max is still the limit.
1. Set to DC Amperes.
2. Set to AUTO.
3. Connect the signal to be measured at the HI terminal.
4. Observe the displayed digits, polarity sign, decimal point location, and measure-
ment unit (mA, or A). If no polarity sign is indicated, a positive polarity is implied.
b. AC Current. The Model l7ZA DMM detects ac currents from IO microamperes rnsidigir
to 2 amperes vn5. When the input exceeds 2 amperes, the current Fuse will blow.
1. Set to AC Amperes. (The AC indicator should be lighted).
2. Set to Auto.
3. Connect the signal to be measured at the HI terminal.
4.
Observe the displayed digits, decimal point location and measurement unit !AC
mA or AC A).
FIGURE 3-2. Typical Model 172ACurrent Display (DCmA).
3-r
OPERATING INSTRUCTIONS INSTAUCTION MANUAL
Digital Multimeter
Models 172A. 1?3A
3-7. HOW TO MEASURE CURRENT. (MOOELl73AONLY.) The Mode1173A measures ac and
dc current in five ranges: 0.3mA. 3mA, 30mA, 0.3A, and 3A.
CAUTION
The Model 173A DMM is protected by a 3 ampere fuse on al I ranges. If the fuse is
A blown, a replacement Keithley Part No. FU-2 should be installed in the rear panel
fuse holder. (See Figure 2-l).
a. DC current. The Modell73A DMM detects dc currents from +I0 nanoamperes to 23
amperes. The maximum display is 29999. When the display exceeds 29999, a 3 remains
lighted, but all other digits are blanked.
I. Set to DC Amperes.
2. Set to AUTO.
3. Connect the signal to be measured at the HI terminal.
4. Observe the displayed digits, polarity sign, decimal point location, and measure-
ment unit (,A, mA, or A). If no polarity sign is indicated, a positive polarity is
implied.
b. AC Current. The Model 173ADMM detects ac currents from IO nanoamperes rms/digi t
to 3 amperes rms. The maximum display is 29999. When the display exceeds 29999, a 3
remains lighted, but all other digits are blanked.
1. Set to AC Amperes. (The AC indicator should be lighted.)
2. Set to AUTO.
3. Connect the signal to be measured at the ill terminal.
4. Observe the displayed digits, decimal point location, and measurement tinit (ACiA,
AC ma, or AC A).
FIGURE 3-3. Typical Model l73A Current Display (ACmA).
3-6
INSTRUCTION MANUAL OPERATING INSTRUCTIONS
Digital Multimeter
Models 172A. 173A
3-a. HOW TO MEASURE RESISTANCE. The Modell72A/173A measures resistance from IO milli-
ohms/digit to 300 megohms. The maximum display is 29999. When the display exceeds
29999, a 3 remains lighted, but all other digits are blanked.
a. HI Ohms Measurement. When the HI/LO pushbutton is released (set to HI), the volt-
age developed across the resistance under test at full range is 3 volts. The Model 172A/
173A measures from 100 ms2 to 300 megohms in HI mode.
I. Set to HI Ohms.
2. Set to 2 WIRE.
NOTE
When the Model l72A/l73A IS set to 2 WIRE,the lower set of HI and LO input terminals
is not connected. When set to 4 WIRE, the higherset of HI an(7 LO input terminals
is used as "voltage sensing" terminals. See Section 3-9 for more detailed infor-
mation.
3. Set to AUTO.
4. Connect the resistance under test between the upper set of HI and LO terminals.
5. Observe the displayed digits, decimal point location, and measurement unit (2,
Kn, or MR).
b. LO Ohms Measurement. When the HI/LO pushbutton is depressedtset to LO), the volt-
age developed across the resistance under test at full range is 300 miljjvolts. ◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo