Keithley 174 Service manual
INSTRUCTION MANUAL
MODEL 174
DIGITAL MULTIMETER
COPYRIGHT, 1977, KEITHLEY INSTRUMENTS, INC.
THIRD PRINTING, AUGUST, 1980, CLEVELAND, OHIO, U.S.A.
DOCUMENT NO. 28263, REV. 8
CONTENTS
INSTRUCTION MANUAL
Digital Multlmeter
Model 174
kction
:ONTENTS.
LLUSTRATlbNs : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : i;i
iPECIFICATIONS.
. GENERAL INFORMATION
I-1. INTRODUCTION.
l-2.
l-3.
l-4.
.. INITIAL PREPARATION
2-l.
2-2.
2-3.
o--- .- .._ .
i.
FtKAIlNti INSTRUCTIONS.
3-l. G ~iENERAL
3-2. HOW TO SELEC-
3-3.
3-4.
3-5.
3-6.
3-J.
3-8.
ACCESSORIES
..
4-l. G
4-2.
4-3.
4-4.
4-5.
4-6.
4-7.
;I,“:
4-10. MODEL 1723 IEEE INTERFACE
FEATURES.
WARRANTY INF6RMA;I6N: : : : : : : : : : : : : : : : : : : : : : : : : : : l-l
CHANGE NOTICE
GENERAL
INSPECTION.
PREPARl iTION FOR USE
HOW TO SELECT FUNCTION.
HOW TO SELECT RANGE
HOW TO MEASURE VOLTAGE.
HOW TO MEASURE RESISTANCE
HOW TO MEASURE CURRENT. .
FURTHER MEASUREMENT CONSIDERATiOk: : : : : : : : : : : : : : : : : : . . 3-g
,ENERAL
,^__.
MuutL I/ZU KECHAKG
MODEL I
RACK MC
PROBES AND SHUNTi : : : : : : : : : : : : : : : : : : : : : : : : : : : : 4-23
CONVENIENCE CABLES AND CONNECTORS
LOW-THERMAL CABLES. .
MODEL
MODEL
..................................
..............................
..............................
..............................
..............
.................
..
..............................................
............................
....................
--T POWER.
..................................
.-z, ................................
---~~---EABLE BATTERY PACK.
I722
DIGITAL INTERFACE.
XJNTING
1727
DIGITAL OUThi cAeLE iE+ ’ ’ ’ ’ : : : : : : . * * * ’ ’ ’ ’
1743
MAINTENANCE KIT.
..........................
.........................
...........................
........
.......
......................
....................
.... : : : :
........................
: : : : : : :
: : : : : : : : : : : : : : : : :
.................
......
...........
: : : : : : : :
.....
,: : : : : 2-l
. . 3-9
. 2
: 4-24
.
Page
iv
l-l
I’-1
l-l
l-1
2-1
2-l
2-l
3-l
3-l
3-1
3-3
3-5
3-6
3-8
4-l
4-6
4-21
4-24
4-24
4-26
4-25
!
ii
AA
INSTRUCTION MANUAL
Dlgllel Mulllmeler
Model 174
CONTENTS (Cont'd)
#ection
. THEORY OF OPERATION . . . . . . . . . . . . . . . . . . . . . .
15
5-l. GENERAL.........................::::::::5-,
5-2.
5-3.
5-4.
5-8. ANALOG-TO-DIGITAL CONVERTER (Schematic
5-9.
5-10. DIGITAL BOARD (Schematic 28209E). . : : : : : : : : : : : : : : 1 : : : . 5-23
5-l
MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . : : : : : : : : : 6-1
’ 6-1.
6-2.
6-3.
6-4.
6-5.
REPLACEABLE PARTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-l
7
* J-l.
7-2.
7-3.
SIGNALFLOW...............................
SWITCHING (Schematic
NANOVOLT PREAMP (Schematic
MODEL
MODEL
MODEL
1740
AC OPTION (Schematic
1744
OHMS OPTION (Schematic
1745
AMMETER OPTION (Schematic
27935E). . . . . . . . . . . . . .
279370
E block diagram, Figur; i2.j : : : : : . 5-4
279440)
27941Cj : : : : : : : : : : 1 : : : : . 5-8
2794OC). .
2J936F). : : : : : : : : : : : : , 5-12
DISPLAY BOARD (Schematic
I. POWER SUPPLY (Schematic 279380) . . . . . . . . . . . .
GENERAL.................................6-I
REQUIRED TEST EQUIPMENT . . . . . . . . . . . . . . . . . . . . . , . . . 6-1
PERFORMANCE VERIFICATION . . . . , , . . . . . . . . . . . . . , . . , . 6-1
ADJUSTMENT/CALIBRATION PROCEDURE . . . . . . . . . . . . . , . . . . . .
TROUBLESHOOTING. . . . . . . . . . . . . . . . . . , . . . . . . . . . .
GENERAL...... . . . . . . . . . . . . . . . . . . . . . . . . ...7-I
ORDERING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . 7-l
SCHEMATICS . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-l
279391)). .
Page
5-l
5-l
. 5-2
. 5-5
. 5-12
. 5-21
5-25
6-g
6-21
i
AA
ii;
ILLUSTRATIONS
INSTRUCTION MANUAL
Dlgital
Multlmeter
Model174
igure No.
I
2
T,
65
ii
9
IO
Ila Connector Pin Identification For Model 174/1722. ...........
lib
6
14
15
16
17
18
I9
20
21 Diagram of Signal Flow
22
23
24
2
27
28
::
::
;t
35
36
37
38
2’0
41
::
2:
:;
48
49
50
Title
Dimensional Data
Rear Panel Connections
View of Chassis With Cover Removed . .
Installation of Models
Typical Display For Non-Valid Function ................
Front Panel Controls and Input Terminals ...............
Manual Ranging on the Model
Model
Installation of Model 1728 ......................
Installation of Model
Connector Pin Identification For Model
Installation of Model 1722 Digital Interface .............
Location of Jumpers t Pull-Ups For Model
Model 1722 Block Diagram
Model 1007 Dual Rack Mounting Kit.
Model 2000 Rack Mounting Kit .....................
Model 1746A Low-Thermal Shorting Plug
Model 1747A Low-Thermal Cable Set ...................
Model 1743 Maintenance Kit ......................
Typical Installation of Extender Card on Model 1722. .........
Simplified Diagram of Nanovolt Preamp. ................
Diagram of AC Attenator (Model
Diagram of AC/DC Converter (Model 1740). ...............
Simplified Diagram of Model 1744 Ohms Option .............
Detailed Diagram of Model 1744 Ohms Option .............. 5-IC
Basic Functional Blocks of A/O Converter ...............
Basic Charge Balance Converter ....................
Operating Waveforms of A/D Converter .................
Simplified Schematic
Simplified Diagram of Complete A/O Converter .............
A/O Converter System Timing. ..................... 5-21
Digital Display Multiplex Scheme ...................
Test Circuit For
Test Circuit For 3uA Verification. .................. 6-7
Model
Model
Waveform For A/D Calibration .....................
Model
Model
Component Layout, PC-412 (Part I). ....................... : : 1 : : : :
Component Layout, PC-412 (Part 2).
Component Layout, PC-421 .......................
Component Layout, PC-410 .......................
Component Layout, PC-414
Component Layout, PC-408 .......................
Component
Componen r. Layout,
Component Layout, Model
Component
1728
Rechargeable Battery Pack .................
I74
Top View With Cover Removed.
I74
Calibration Adjustments. ..................
I74
Chassis Assembly ......................
I74
Bottom Cover Assembly.
Layout,
Layout, Model
...........................
........................
1740,
1744, 1745: : : : : : : : : : : : : : : :
174. ...................
1722
Digital Interface .............
174/1722. ........... 4- I(
1722. ............
....................... 4-I(
..................
.................
........................
1740) .................
.........................
30
mV DC Accuracy Check ............... 6-3
................
..................
.......................
~~-409
Model 1728 .....................
.......................
1722,
1722,
Upper Board (PC-415) . * * . . * . + ' ' 7-67
Lower Board (PC-416) * * * * . * * ' ' *
Page
v
1-2
1-4
2-3
3-2
3-4
3-5
4-3
4-4
4-7
4-9
4- 11
4-l:
4- 2C
4-2;
4-Z:
4-Z!
4-2;
4-2t
5-l
5-4
5-5
5-7
5-9
5-1:
5-IL
5-11
5-1;
5-2C
5-
2i
6-1~
6-11
6-11
6-25
6-21
7-53
7-54
7-57
7-58
7-59
7-60
7-61
7-62
J-65
iv
BB
SPECIFICATIONS
AS AN AUTOJMANUAL RANGINQ DC VOLTMETER
INSTRUCTION MANUAL
Dlgital MullimeIer
Model 174
WITI AUTO/MANUAL RANGING AC VOLTAGE OPTION ,740
vi
ASANACAMMSTER WlTHOPTlONSl740ANO~7~5
AA
INSTRUCTION MANUAL
DigItat MultImeter
Model 174
t
8.5" (217mm)
I
FIGURE I.
Dimensional Data.
INSTRUCTION MANUAL
DigItal MultImeter
Model 174
GENERAL INFORMATION
SECTION I.
l-l. INTRODUCTION.
measuring instrument,
l-2. FEATURES.
Standard
a.
Sensitivity to 0.1 microvolt dc.
I.
30000
2.
0.013% basic dc accuracy
t :
Manual, automatic or remote ranging.
Lo to CASE isolation to 10’0.
5.
Optional.
b.
1. Model 1728 Rechargeable Battery Pack.
Model 1722 Digital Interface.
Model 1723 IEEE Iriterface.
;:
Model 1740 AC Option.
5:
Model 1744 Ohmmeter Option.
6. Model 1745 Ammeter Option.
l-3.
manua I .
ized repair facility as given on the inside front cover of this manual.
WARRANTY INFORMATION.
count display for high resolution.
If there is a need for service,
The Model 174 Digital Multimeter is a wide-range, general purpose
capable of measuring ac/dc voltage, ac/dc current, and resistance.
The warranty is stated on the inside front cover of the
GENERAL INFORMATION
contact your Keithley representative or author-
l-4.
the manual will be explained on a change notice sheet attached to the inside back cover
of the manual.
CHANGE NOTICE.
The A symbol can be found in various places in this Instruction Manual.
fully read the associated
ling of the instrument. Damage to the instrument may occur if these precautions
are ignored.
The\ symbol can be found in various places in the Instruction Manual.
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.
cautions are ignored.
Improvements or changes to the instrument not incorporated into
IMPORTANT
Care-
CAUTION
statements with regard to proper use and hand-
This
Serious personal injury may result if these pre-
AA
1-l
GENERAL INFORMATION
INSTRUCTION MANUAL
Digital Multimeter
Model 174
'HILLIPS
iCREWS
3mV DC,
REMOVE TOP COVER 30mV DC,
TO GAIN ACCESS ANALOG
TO CHASSIS (4 SCREWS)
OUTPUT
CONNECTION TO
MODEL 1722 OR
1723 INTERFACE
PHILLIPS
SCREWS
l-2
LINE
FUSE
F401
FIGURE 2. Rear Panel Connections.
LiNE
INPUT
P405
AA
INSTRUCTION MANUAL
Dlgltat MultImeter
Model 174
GENERAL INFORMATION
TABLE I-l
Summary of Options and Accessories
ptions:
Model 1740 AC Option
Model 1744 Ohmmeter Option
Model 1745 Ammeter Option
upplied Accessories:
Model 1746~ Low-Thermal Short
mther Accessories:
Model 1600 High Voltage Probe
Model 1651 50-Ampere Shunt
Model
Model 1685 Clamp-On AC Current Probe
Model
Model 1723 IEEE Interface
Model 1727 Digital Interface Cable Set
1682
RF Probe
1722
Digital Interface
Remarks:
Factory or Field-Installed. To field-
install, refer to Section
Factory or Field-Installed.
install, refer to Section 2, paragraph Z-3d
Factory or Field-Installed.
install, refer
See ACCESSORIES, Section 4, paragraph 4-7a.
See ACCESSORIES, Section 4, paragraph 4-5a.
See ACCESSORIES, Section 4, paragraph 4-5b.
See ACCESSORIES, Section 4, paragraph 4-5~.
See ACCESSORIES, Section 4, paragraph 4-jd.
See ACCESSORIES, Section 4, paragraph 4-3.
Described in separate Instruction Manual.
See ACCESSORIES, Section 4, paragraph 4-8.
to
Section 2, paragraph
2, paragrap” 2-3~
To field-
To field-
2-3e
Model 1728 Rechargeable Battery Pack
Model 1743 Maintenance Kit
Modell747A Low-Thermal Input Leads
See ACCESSORIES, Section
See ACCESSORIES, Section 4, paragraph 4-9.
See ACCESSORIES, Section 4, paragraph 4-7b.
4, paragraph
4-2.
BB
l-3
GENERAL INFORMATION
LINE
SWITC :HES -
INSTRUCTION MANUAL
Digital Multimeter
Model 174
-MOUNTING
BRACKET
SHIELD FOR
'NANOVOLT
PREAMP
l-4
MODEL
MODEL
MODEL
1740
1744
1745
VIOLET WIRE
,TO MODEL
1740
-FUSE
FIOOI
FIGURE 3. View of Chassis With Cover Removed.
AA
INSTRUCTION MANUAL
Dlgltal Multlmeter
Model 174
INITIAL PREPARATION
SECTION 2. INITIAL PREPARATION.
2-l.
preparation for use.
2-2.
ly before shipment. Upon receiving the instrument,
may have occurred during transit.
the electrical specifications,
2-3. PREPARATION FOR USE. The Model 174 may require soie preparation before placing the
instrument in use, depending on the field-installable options or accessories to be used.
For line operation the Line Voltage switches and Line Fuse should be checked to verify
correct settings or value for the line power voltage to be used.
Models 1722, 1723, or 1728 are to be field-installed, the top cover will need to be removed.
See ACCESSORIES, Section 4 in this manual.
are to be field-installed,
in following paragraphs c, d, and e must be used.
GENERAL.
INSPECTION.
a. How to Set the Internal Line Voltage Switches (S4Ol and 5402). The Model 174
has two slide switches located on the main circuit board as shown in Figure 3. The
top cover must be removed to gain access to the circuit board as shown in Figure 2.
This section provides information needed for incoming inspection and
The Model 174 was carefully inspected both mechanically and electricai-
check for any obvious damages which
Report any damages to the shipping agent. To verify
follow the procedures given in Section 6.
If any one of accessory
If any of the Models 1740, 1744, 1745 Options
the top cover must be removed and the installation procedures
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
HAZARD.
TABLE 2-l.
Summary of Line Voltage Settings
Line Fuse Requirement.
b.
line-operated power supply.
fuse rating is 1/2A for 90-125V range, l/4A for IgO-250V range. The line fuse is
located on the rear panel as shown in Figure 2.
The Model 174 uses a single line fuse to protect the
The fuse is a 3 AE, slow-blow type.
Verify that the
Line
2-l
INITIAL PREPARATION
INSTRUCTION
Digital MultImeter
MANUAL
Model 174
C.
How to Install the Model 1740 AC VOLTS Option.
wire.
Install the plug-in board for the Model 1740 on the Model 174 chassis at PSOI and P502
as shown in Figure 4.
edge guides which support the board.
instrument.
d. How to Install the Model 1744 OHMS Option.
1744 is installed on the Model I74 chassis at P503 as shown in Figure 4.
side of ~~-408 faces the front of the Instrument.
e.
Model 1745 is installed on the Model I74 chassis at P504 and P505
The component side of PC-409 faces the front of the instrument. Check fuse FIOOI for
proper rating and condition.
rating.
The AMPERES circuit must be calibrated prior to use as in Section 6-49.
Connect the “violet” input lead (P301) coming from the Function Switch to Jl203.
The plug-in board (PC-414) edges should mate with the teflon card
The component side of PC-414 faces the front of the
IMPORTANT
The AC VOLTS circuit must be calibrated prior to use as in Section 6-4e.
IMPORTANT
The entire 174 Calibration Procedure must be performed prior to use as in Section 6-4.
How to Install the Model 1745 AMPERES Option.
Replacement fuse is a Keithley Part No. FU-39; 4 amperes
IMPORTANT
Cut the tie wrap holding the “violet”
The plug-in board (PC-408) for the Model
The component
The plug-in board (PC-409) for the
as
shown in Figure 4.
2-2
AA
INSTRUCTION MANUAL
Digital Mulllmeler
Model
174
INITIAL PREPARATION
FIGURE 4.
Installation of Models 1740, 1744, 1745.
2-3
NITIAL PREPARATION
Summary of Detailed
INSTRUCTION MANUAL
Digital Multimeter
Model 174
TABLE 2-2.
74 Max Rating at Input Terminals
I-
FUNCTION
DC VOLTS
300 mV - 1 KV
3 mV and 30 mV
AC VOLTS
OHMS
AMPS
3OOpA-3A
30~A
3uA
HI TO LO MAXIMUM
12OOV Peak
250V RMS sine, <60Hz
Peak
. <lO'V~Hz
IOOOV RMS, ,<lO'V.Hz
240V RMS sine, ~60Hz or 350~
Peak
, <lO'V*Hz
~250~ PK or c60Hz RMS if
4A,
fuse blows
25mA or 25OV RMS on fixed range
2.5mA or 25OV RMS on fixed range
or
250~
2-4
AA
INSTRUCTION MANUAL
DIgItal MultImeter
Model 174
OPERATING INSTRUCTIONS
SECTION 3.
3-l.
measurement of voltage, current, and resistance,
3-2.
able nickel-cadmium batteries.
tion. The I ine-voltage supply is built-in.
(2 m) long.
four ranges, from a ininimum of 90 V rms to a maximum of 250 V rms. Table 2-1 (pg 2-l)
summarizes the I ine voltages permitted.
GENERAL.
HOW TO SELECT POWER.
The
accessory
purchase of the Model 174 or may be purchased and field-installed at a later time
if so desired.
a. How to Operate From Line Power.
Set the internal line voltage switches (S4Ol and 5402) to the appropriate position
1.
as described in Section 2, paragraph 2-3a.
2. Attach the line cord (CO-7) to the Model I74 at power input receptacle (P405) on
the rear panel. If a shorter I ine cord is desired,
Cord (2 foot long).
This section provides information needed to operate the Model 174 for
The Model 174 may be powered from line voltage or recharge-
The Model 1728 must be installed to permit battery opera-
Model 1728 Rechargeable Battery Pack may be ordered at the time of
OPERATING INSTRUCTIONS.
when the appropriate option is
The power cord is detachable and is 6 feet
NOTE
The Model 174 can be powered from line voltage over
order Keithley Model 7003 Power
installed.
Check the line fuse for proper rating as described in Section 2, paragraph 2-3,
3.
4. Plug the line cord into a source of line power.
Depress LINE pushbutton.
5.
NOTE
Power on will be indicated by a lighted display with one or more digits and measurement
units showing.
b. How To Operate From Battery Power.
Install the Model 1728 Rechargeable Battery Pack. (See Section 4, paragraph 4-Z.)
I.
2. Depress BAT pushbutton.
If the LOW BAT indicator is lighted in BAT mode, refer to Section 4-2~ for re-
3.
charging;
otherwise, the Model 174 may be used for measurements.
3-l
OPERATING INSTRUCTIONS
NOTE
The Model 1728 is shipped from the factory in uncharged condition. Therefore, the
Model 1728 should be installed and charged prior to use.
been charged for at least I6 hours,
at least 3 hours.
Summary of Operation in Line and Bat Modes
the Model 174 can be powered continuously for
TABLE 3-2.
Condition of Instrument
After the Model 1728 has
INSTRUCTION MANUAL
Digital Multimeter
Madei 174
Line Power Connected
Button Depressed 1728 Not Installed
LINE ON
BAT
NEITHER
LINE NOR BAT
OFF
OFF
Line Power Connected Line Power Not Connected
1728 Installed 1728 Installed
ON
Batterv trickle charaed.
ON
Battery slowly discharged.
OFF
Battery charged at maximum
rate.
OFF
ON
OFF
3-2
LIGHTED DECIMAL 60lNTS.
FIGURE 5.
Typical Display For Non-Valid Function.
AA
INSTRUCTION MANUAL
Dlgltal MultImeter
Model 174
OPERATING INSTRUCTIONS
3-3.
switch (5302).
ac voltage function.
voltage function.
to
HOW TO SELECT FUNCTION.
a. V AC (~1.
The Model
Option 1740 is installed. If this option is not installed the Model I74 will display
all four decimal points to indicate a non-valid function as shown in Figure
b. vDc(=)
res 1 stance ohms) function.
-9
The Model
installeo:
mal points to indicate a non-valid function as shown in Figure
1. HIR. When the FUNCTION Switch is set to Hln, the Model I74 permits resistance
measurements in
2.
measurements in 6 ranges from 300~ to 30MR.
I74
174
LOR. When the FUNCTION Switch is set to LOQ, the Model I74 permits resistance
When the Function Switch is set to V AC the Model 174 will be set to
Refer to paragraph 3-6 for operating information.
can be used to measure ac voltage only when the Averaging AC Voltage
. When the Function Switch is to V DC the Model 174 will be set to dc
Refer to paragraph 3-b for operating information.
When the Function Switch is set to HI0 or LOR the Model I74 will be sef
can be used to measure resistance only when the Ohmmeter Option 1744 is
If this option is not installed,
6
ranges from 3K0 to 300MO.
Function is selected by means of a front panel rotary
IMPORTANT
5.
Refer to paragraph 3-6 for operating information.
IMPORTANT
the Model 174 will display all four deci-
5.
Full range voltage is 3 V.
Full ranoe voltage is 300 mv.
d. A DC (ZJ. When the FUNCTION Switch is set to A DC the Model 174 will be set to dc
current function. Refer to paragraph 3-7 for operating information. Neither auto-
ranging nor remote ranging are available on Amperes.
IMPORTANT
The Model I74 can be used to measure dc current only when the DC Amneter Option I745
is installed.
decimal points to indicate a non-valid function as shown in Figure 5.
e. A AC (“J).
ac current function. Refer to paragraph 3-7 for operating information.
autoranging nor remote ranging are available on Amperes.
The Model I74 can be used to measure ac current only when both the AC Voltage Option
1740 and the DC Amneter Option 1745 are installed. If these options are not installed
the Model
as shown In Figure
If this option is not installed the Model 174 will display all four
Whkn the FUNCTION Switch is set to A AC the Model I74 will be set to
Neither
IMPORTANT
I74
will display all four decimal points to indicate a non-valid function
5.
AA
3-3
OPERATING INSTRUCTIONS
INSTRUCTION MANUAL
Digital Multimeter
Model 174
LOW
BATTERY
mv
ZERO
FUNCTION
-‘ITCH
3-4
LINE BAT
PZN
SEE FIGURE 7
FOR RANGE SELECTION
DETAILS
FIGURE 6.
Front Panel Controls and Input Terminals.
VALID FOR
VOLTS AND
OHMS ONLY
CASE
GROUND LO HI
J304 J303
INPUT INPUT
J302
AA
INSTRUCTION MANUAL
OPERATING INSTRUCTIONS
Digllsl MulIlmeIar
Model 174
3-4. HOW TO SELECT RANGE. On VAC, VDC, and :1 the Model I74 provides automatic, remote,
or manual ranging. Remote ranging is available only when the Model 1722 or 1723 is
installed.
Manual Ranging. (Al I functions).
a.
ing the appropriate range pushbutton.
ranging.
If A AC or A DC is selected and none of the valid current range pushbuttons
are depressed the Model 174 will be placed in the following condition: The input
resistance will be 100 KR in parallel with overcurrent protection diodes.
174 display will read near zero (independent of the signal applied) and the decimal
position will be the same as for the 3 uA range (0.0000).
b.
Remote Ranging. (V AC, V DC, and OHMS only).
the Model 1722 or Model 1723 is installed and the REM oushbutton is depressed.
Section 4 ACCESSORIES for information regarding Models I722 or 1723.
The REM pushbutton determines range control only,
Trigger, Hold, and Trigger Mode.
C.
Autoranging. (V AC, V DC, and OHMS only).
ranging mode under the following conditions.
The Model 174 can be set to Hanual Mode by depress-
See Figure 7 for detailed explanation of manual
NOTE
The Model
Remote ranging is available only when
Refer to
NOTE
and does not affect timing controls,
The Model I74 will be placed in Auto-
If AUTO is depressed the Model I74 will be set to autoranging mode.
I.
2. If none of the manual range nor REM pushbuttons are depressed (that is, all are
released),
then the Model 174 will be set to autoranging mode as a default condition.
AA
FIGURE 7.
Manual Ranging on the Model 174.
3-5
OPERATING INSTRUCTIONS
NOTE
The following rules govern the autoranging feature:
a) When the display exceeds 29999, the Model 174 upranges (that is, it changes to
less sensitivity and the decimal point and measuring unit changes appropriately).
b) When the display reaches 02599 the Model I74 downranges (that is, it changes
to greater sensitivity and the decimal' point and measuring unit changes appropriately)
until it reaches the most sensitive range (except 3mV dc and 30 nV dc).
INSTRUCTION MANUAL
Digital Multimeter
Yodet~74
3-5.
30mV, 300mV, 3V, 3OV, 3OOV, and IOOOV DC.
Model 174 measures ac voltage in five ranges, 300 mV, 3V, 3OV, 3OOV, and IOOOV.
HOW TO MEASURE VOLTAGE.
Maximum input voltage depends on the range selected.
allowable continous input for each range on AC and DC. Do not exceed these voltages
or damage to the instrument will occur.
The Model 174 measures dc voltage in seven ranges:
When the Model 1740 Option is installed, the
CAUTION
Table 3-3 gives the maximum
TABLE 3-3.
Maximum Allowable Continuous Input
IOOOV rms (<lO'V.Hz
1000~ rms (<lO'V.Hz
IOOOV rms
IOOOV rms (<lO'V*Hz
1OOOV rms
(*107V.Hr
(<lO'V~Hz
*NOTE
12OOV Peak
1200V Peak
12OOV Peak
12OOV Peak
3mV,
When 3mV or 30mV range pushbuttons are depressed,
and thus the allowable input will be 1000 V rms
DC Voltage. The Model 174 detects dc voltages from f0.1 microvolts/digit to t1200
voy;s (1200.0 display). The maximum display is 29999. When the display exceeds 29999,
a 3 remains lighted, but ail other digits are blanked.
volts on the highest range.
Select V DC on Switch 5302.
1.
2. Depress AUTO, REM or desired Manual Range pushbutton.
Connect the signal to be measured between HI and LO terminals. The terminals are
3.
designed to accept banana or "bunch pin" plugs,
1747 Low-Thermal coaxial input cable.
below IO microvolts dc resolution.
4. Observe the displayed digits, polarity sign,
ment unit (mV or V).
A "zero" reading will always be displayed as -.OOOO.
3-6
If no polarity sign is indicated,
These leads are recommended for measurements
the 300mV range will be selected
(<IO'V*Hz).
The display blinks above 1200.0
such as the accessory Keithley Model
decimal point location, and measure-
a positive polarity is implied.
AA
INSTRUCTION MANUAL
Digital Multimeter
Model 174
OPERATING INSTRUCTIONS
On the 3 mV and 30 mV DC ranges the front panel "mV ZERO" control must
5.
adjusted to obtain rated accuracy.
Make low-thermal connections to the Model
a)
Model 1747 cable or satisfactory equivalent is recommended.
b) Set the Model 174 to the 3 mV range.
Allow the thermal emfs generated by the input connections
C)
d) Some circuits may need to be enclosed in polyurethane foam, a cardboard box,
or other suitable enclosure to prevent zero fluctuations due to air movement at the
connection point.
Make certain that a "Zero Signal"
e)
be measured (e.g., a zero current condition for a resistance thermometer measurement).
f) Adjust the "mV ZERO" control for a display indication of-.0000 mV f .OOOl mV.
The "mV ZERO"
effect on any
Proceed
9)
h) The "mV
control operates only on the 3 mV DC and 30 mV DC ranges.
other range or function.
with the measurement and apply the signal.
ZERO" control setting will also be valid for the 30 mV range if used.
condition is established for the circuit to
NOTE
174
as described above. Use of tne
to
stabilize.
be
It has no
AC Voltage.
b.
(1000.0 display).
The Maximum display is 29999.
all other digits are blanked.
Maximum input voltage is 1000 V rms or
I.
Select V ac on Switch 5302.
Depress AUTO, REM or desired Manual Range pushbutton.
2.
Connect the signals to be measured between HI and LO terminals.
3.
are designed to accept banana or "bunch pin" plugs,
1747 Low-Thermal coaxial input cable.
4.
Observe the displayed digits, decimal point location,
v) .
The Model 174 detects ac voltages from IO microvolt5 to 1000 volts
The Model
174
is average-reading,
When the display exceeds 29999, a 3 remains lighted, but
The displa
blinks above 1000.0 volts on the highest range.
7
10 V*Hz on all ranges.
calibrated in terms of rms sinewave
(The terminals
such as the accessor Keithley Model
and measurement unit (mV or
3-7
OPERATING INSTRUCTIONS
INSTRUCTION MANUAL
Digital Multimeter
Model 174
3-6.
measures resistance from IO milliohms/digit to 300 megohms. The maximum display is 29999.
When the display exceeds 29999, a 3 remains lighted,
Maximum allowable input voltage is 240V rms or 350 V peak up to 60 Hz.
the resistance under test at full range is 3 volts. The Model 174 measures from 3Kn to
300 megohms full range in HI mode.
the resistance under test at full range is 300 millivolts.
3OOC to 30 megohms full range in LO Mode.
HI and LO terminals. For measurement on low resistance ranges where lead resistance may
cause an error the following procedure should be performed.
HOW TO MEASURE RESISTANCE. When the Model 1744 Option is installed, the Model 174
but all other digits are blanked.
a. HI Ohms Measurement.
I. Select Hlfl on Switch 5302.
2. Connect the resistance under test between HI and LO terminals.
Depress AUTO, REM, or the desired Manual Range pushbutton.
3.
4. Observe the displayed digits, decimal point location, and measurement unit (Kfi or
MR) .
b. LO Ohms Measurement. When Switch 5302 is set to LOO,
1. Select LO n on Switch S302.
2. Connect the resistance under test between HI and LO terminals.
Depress AUTO, REM, or the desired Manual Range pushbutton.
3.
Observe the displayed digits, decimal point location, and measurement unit (iI,
4.
KR, or Mn).
Lead Resistance Compensation.
c.
When Switch S302 is set to HIR, the voltage developed across
the voltage developed across
The Model 174 measures from
The Model I74 measures the total resistance between
1. Connect the measuring circuit to the INPUT terminals on the 174 using appropriate
test leads or cables.
2. Substitute a temporary short circuit in place of the circuit to be measured.
fn the case of the Model 1747, temporarily clip together the alligator connectors.
3.
4.
Record the reading on the Model 174 as RO (residual lead resistance under a
shorted condition).
Remove the shorted condition and connect the active circuit to be measured.
5.
6. Record the new reading in the Model 174 as R,.
The true value of “Ri’ is R = R - Rg, within the stated accuracy of the Model
7.
174.
method.
No additional errors in theTresi:tance measurement are added when using this
3-8
AA
INSTRUCTION MANUAL
Digital Multlmeler
Modal 174
OPERATING INSTRUCTIONS
3-7.
measures dc current in seven ranges:
both the Model I740 and 1745 Options are installed, the Model 174 measures ac current over
the same ranges. Range selection is via manual range pushbuttons only.
peres. The maximum display is 29999. When the display exceeds 29999, a 3 remains lighted
but all other digits are blanked.
HOW TO MEASURE CURRENT.
The Model I74 DMM is protected by a 4 ampere fuse on all ranges except 3uA and
3OuA.
250V input voltage. If the fuse is blown,
should be installed in the fuse holder on the 1745 option.
MAINTENANCE, Paragraph 6-5, for fuse replacement.
a. DC Current.
I. Select A dc on Switch S302.
2.
3.
4.
ment unit (uA,. mA, or A).
implied.
On the 3uA and 30uA ranges the maximum allowable input corresponds to a
The Model 174 DMM detects dc currents from to.1 nanoamperes to ?3 am-
Depress the desired Manual Range pushbutton.
Connect the signal to be measured at the HI and LO terminals.
Observe the displayed digits, polarity sign, decimal point location, and measure-
A "zero" reading will always be displayed as -.OOOO.
When the Model 1745 option is installed, the Model 174
3uA, 30uA, 300pA, 3mA,
CAUTION
a replacement Keithley Part No. FU-39
If no polarity sign is indicated, a positive polarity is
30mA, 300mA, and 3A. When
Refer to Section 6,
b. AC Current. The Model I74 DMM detects ac currents from 0.1 nanoamperes/digit to
3 amperes in AC function. The Model 174 is average reading calibrated in rms of a sine
wave. The maximum display is 29999. When the display exceeds 29999, a 3 remains lighted,
but all other digits are blanked.
Select A AC on Switch S302.
I.
Depress the desired Manual Range pushbutton.
2.
Connect the signal to be measured at the HI and LO terminals.
3.
Observe the displayed digits, decimal point location, and measurement unit (PA,
4.
ma or A).
3-8.
FURTHER MEASUREMENT CONSIDERATIONS.
Grounding Considerations.
a.
the line cord are provided to avoid electrical shock in the event of an electrical
malfunction. The ground (CASE) terminal,
ground,
ground is at a safe potential at all times.
Always ensure that the instrument Is grounded either through the third wire on
the line cord or through a separate connection between CASE terminal and reliable
earth ground.
injury due to electrical shock.
serves as a return current path and ensures that the instrument chassis
Failure to follow these precautions could result in serious personal
The CASE terminal and the third wire ground on
when properly connected to a reliable
WARNING
AA
3-9
OPERATING INSTRUCTIONS
INSTRUCTION MANUAL
Digital Multimeter
Model 174
How to Use the Model 174 Off-Ground.
b.
at’potentials of up to ilOO volts.
(CASE terminal) is specified at 103n shunted by less than O.OluF. In general, the LO
terminal should be connected to the point in the measurement circuit which has the lowest
impedance to power I ine ground or the “effective guard” or “shield” mode in the circuit.
If the measurement circuit is independent of power line ground LO and CASE should be
connected to a cornnon point in the circuit.
c.
3mV/30mV Accuracy. The 3mV/30mV accuracy specifications assume that the instrument
has been in thermal equilibrium with the environment for I hour or more, and that the
front panel
obtain a “zero” indication of -.OOOO mV ? .OOOl mV. The “mV Zero” control is used in
this manner to compensate for thermal emfs generated in the circuits connected to the
input terminals. These externally generated thermal emfs must re,nain constant during
the measurement in order to obtain stated accuracy.
d.
300mV Accuracy. The 300mV accuracy is given down to 1% of range. Below 1% of
range an additional .
the 1% level, but gradually as the level is decreased below 3OOuV.
e.
mV Analoq Output.
is specified.
ranges and functions output voltages up to +l5V may exist.
varying within this span,
Analog Output” point is the output of the nanovolt preamp, which has a fixed gain of 100,
and no switching is done,
the “mV Analog Output” provides continous Xl00 output for signal levels as low as the
Model 174 noise level (typically IOOnV to 15OnV p-p, up to 30mV).
“mV ZERO” control has been used imnediately prior to the measurement to
l5mV is added to the accuracy. This does not occur immediately at
This output is active only on 3mV and 30mV ranges. No accuracy
Typically the output is within 2 (2 x accuracy spec + digit). On other
or have step changes within this span. Notice that the “mV
except in the A/D converter between 3mV and 30mV ranges. Thus,
Isolation from the
The “LO” terminal can be operated off ground
“LO” terminal to power I ine ground
Output may be randomly
f. Overload on 3mVdc and 30mVdc.
from DC up
lO7V *
exceed the overload specification on the 3mV/30mV ranges until IO ms after the range
change command is given. (e.g. IOms after Load Range goes active or a new range pushbutton is depressed).
4.
Offset Current. The offset current is adjusted to IOpA at the factory or by
executing the calibration procedure given in Section 6-4.
with time and temperature, but is is unlikely to exceed 200pA at any environment within
the specified region up to 6 months after calibration.
that peak-to-peak noise in the Model 174 will be larger (than that exhibited with a
short circuit) for source resistances in excess of about 30KG to 70Kfi.
Settling Time. Table 3-4 gives typical and worst expected settling times express-
h.
ed as the number of conversions (320 ms) for the Model 174. The numbers in the table
assume that the proper range and function have been selected and previous transients have
“settled” before a “step change” in the signal is applied.
effects of input cabling time constants.
to
60HZ.
HZ product. When switching from 3mV/30mV to higher ranges the voltage must not
Up to 180~ RMS may be applied continuously at any frequency up to
Up to 250V may be continuously applied at frequencies
Offset current wi 1 I change
Short term variations are such
The numbers do not include
3-10
AA
INSTRUCTION MANUAL
Digltsl MultImeter
Model 174
OPERATING INSTRUCTIONS
TABLE
Source R
3mV, 30mV
3mV, 30mV
OHMS
DC AMPS
AC VOLTS
AC AMPS
particular Model I74 will have repeatable settling time characteristics for a fixed
or low) source resistance.
oft instruments ('Itypical values") and the maximum settling time of a "slow" but properly
peratinq instrument ("worst expected values").
All except
3OOMn HI
30Mn LO
3OOMn HI
30MR LO
All
All
All
<lOKn
i-OOKn
LEnd Range
End Range
Any
<lOOKn
Any
The above is a rough indication of what can be expected of
-4.
Number of Conversions Required to
Settle to Within 0.01% of a "Step
Change".
Tvpical
I
20
AA
3-11
INSTRUCTION MANUAL
Dlgllel Multimeter
Model 174
ACCESSORIES
SECTION
4-l.
Model
1722 Digital Interface,
probes, test leads,
only be installed and used one at a time.
4-2.
use, or for complete freedom from ac power lines for critical measurements where near-
infinite commonmode rejection is needed.
recharging is needed from the built-in charger.
operation from full charge. The Model I728 recharges completely in I6 hours with instrument off.
screwdriver and adds I,
-25°C to +35’C when installed in the Model 174.
“NC--
GENERAL. This section describes various accessories available for use with the
174.
Models
Section 2 INITIAL PREPARATION and Section 3 OPERATING INSTRUCTIONS.
MODEL
These accessories include the Model 1728 Rechargeable Battery Pack, the Model
the Model 1723 IEEE Interface,
and other convenience accessories.
1740, 1744,
1728
RECHARGEABLE BATTERY PACK.
Trickle char
Model 1722. 1723 and
and
1745
are field-installable options which are described in
es with instrument on.
;i
kg
(3
pounds) to
1728
can only be installed and used one at a time.
4.
ACCESSORIES
rack mounting kits and various
Model 1722, 1723 and 1728 can
NOTE
The Model 1728 powers the 174 for portable
A front panel low-battery indicator shown when
174.
NOTE
Ni-Cd rechargeable batteries give
The Model 1728 is field installable with
Storage and ambient operating temperatures
3
hours
The Model 1728 Rechargeable Battery Pack can be installed by the user within the
Model I74 at any time. However (
1723 IEEE Interface is already installed,the Model 1728 cannot be used simultaneously
a, How to l’nstall the Model I728 Recharqeable Battery Pack.
nished with the Model 1728 are already installed in the battery pack.
pack includes 7 rechargeable “C” cells (1.2V, 2 AMP tir) and two 19.2 volt packs
(sixteen l.2V cells per pack). See Figure 8.
Check she fuses on the Battery Pack.
I .
F403. All are 1 ampere, 3AB or 3AG, Slo-Blo types, Keithley Part No. FU-IO.
Check for proper installation of batteries in the Battery Pack.
2.
battery cells are to be installed see paragraph 4-2d.
To install the Battery Pack,
3.
shown in Figure 2.
circuit board. Temporarily remove the plastic spacers installed on the Mode) I74
chassis. Separate the two halves of the spacer and reinstall on the Model 1728
board as shown in Figure
assembly.
(P401, P402) taking care to orient the connectors as shown. If the Model 1740 AC
Option is installed,
to permit access to connector P4Ol as in Fiaure 9.
on the spacers with the pack oriented as shown in Figure 9 and tighten down the four
screws which hold the Model
tighten down the four Phillips screws.
Plug the two 5-wire connectors (J401, J402)
Carefully renwve the top cover to gain access to the printed
9.
it will be necessary to temporarily renwve the 1740 pc board
1728
if the Model I722 Digital Interface or the Model
The batteries fur-
The battery
Three fuses are used, F401, F402, and
If replacement
loosen four Phillips screws on the top cover as
The rubber “0” ring retains the spacer and screw
into the mating receptacles
Place~the Model 1728 in position
to the Model I74 chassis. Replace the top cover and
AA
4-l
ACCESSORIES
b.
How to Check Batteries.
INSTRUCTION MANUAL
Digital MultImeter
Modal 174
IMPORTANT
The Model 1728 is shipped from the factory in an uncharged condition.
the pack should be installed in the Model 174 and charged prior to usa
The Model
I.
battery condition.
The LOW BAT indicator will be lighted when the
2.
operating voltage.
LINE or OFF to permit recharging of the Pack.
c. How to Charge the Batteries. The Model 1728 provides built-in recharging circui try.
rapid rate when the Model
and may shorten the life of the batteries.
d.
rechargings before replacement is necessary.
batteries,
the batteries used in the Model 1728.
The Model 174 must be connected to line voltage.
Overcharging the batteries will raise the internal temperature of the battery pack
How to Replace Batteries.
use only the equivalent types as supplied by the factory. Table 4-l summarizes
I74
has a built-in LOW BAT indicator
When the indicator turns on, the
I74
is set to OFF.
CAUTION
The rechargeable batteries will normally provide many
TABLE
Summary of Batteries Used in the Model 1728.
However,
4-l.
to permit easy determination of
Battery Pack goes below normal
Model I74 should be switched to
Recharging occurs at the most
if it is necessary to replace the
Therefore,
Description
I .2v “C” ccl I
(2 AMP-HR)
+19.2V pack
(16-l.2V cells)
-19.2V pack
(16-l .2v ccl IS)
Quantity Vo I tage Keithley Part No.
7
I +19.2V BA-31
I -19.2v BA-3 I
8.4~
BA-30
4-2
AA
INSTRUCTION MANUAL
Digital MultImeter
Model 174
J4Ol
ACCESSORIES
(MATES WITH)
P4Ol
F401
r,uunc 0.
PIO(I~I I/L" nechargeable Battery Pack.
ACCESSORIES INSTRUCTION MANUAL
Digital MultImeter
Med.4
174
4-4
FIGURE 9.
Installation of Model 1728.
AA
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