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INSTRUCTION MANUAL
MODEL 174
DIGITAL MULTIMETER
COPYRIGHT, 1977, KEITHLEY INSTRUMENTS, INC.
THIRD PRINTING, AUGUST, 1980, CLEVELAND, OHIO, U.S.A.
DOCUMENTNO. 28263, REV. 8
INSTRUCTION MANUAL
Digital Multlmeter
Model 174
CONTENTS
kction Page
:ONTENTS.
LLUSTRATlbNs : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : i;i
iPECIFICATIONS. .................................. iv
. GENERAL INFORMATION .............................. l-l
I-1. INTRODUCTION. .............................. I'-1
l-2. FEATURES. l-l
l-3. WARRANTY INF6RMA;I6N: : : : : : : : : : : : : : : : : : : : : : : : : : : l-l
l-4. CHANGE NOTICE .............................. l-1
.. INITIAL PREPARATION .............. ..... 2-1
2-l. GENERAL ................. : : : : : : : ........... 2-l
2-2. INSPECTION. .. .............................................. 2-l
2-3. PREPARl iTION FOR USE ,: : : : : 2-l
o--- .- .._ .
i. FtKAIlNti INSTRUCTIONS. ............................ 3-l
3-l. G~iENERAL .................... 3-l
3-2. HOW TO SELEC- --T POWER. .......................... 3-1
3-3. HOW TO SELECT FUNCTION. ......................... 3-3
3-4. HOW TO SELECT RANGE ........................... 3-5
3-5. HOW TO MEASURE VOLTAGE. ........ 3-6
3-6. HOW TO MEASURE RESISTANCE ....... : : : : : : : : : : : : : : : : : 3-8
3-J. HOW TO MEASURE CURRENT. . . . 3-9
3-8. FURTHER MEASUREMENT CONSIDERATiOk: : : : : : : : : : : : : : : : : : . . 3-g
.. ACCESSORIES .................................. 4-l
4-l. G,ENERAL .-z, ................................
,^__.
4-2. MuutL I/ZU KECHAKG---~~---EABLE BATTERY PACK. ................. . 2
4-3. MODEL II722 DIGITAL INTERFACE. ...................... 4-6
4-4. RACK MC XJNTING 4-21
4-5. PROBES AND SHUNTi : : : : : : : : : : : : : : : : : : : : : : : : : : : : 4-23
4-6. CONVENIENCE CABLES AND CONNECTORS .................... 4-24
4-7. LOW-THERMAL CABLES. . 4-24
MODEL 1727 DIGITAL OUThi cAeLE iE+ ' ' ' ' : : : : : : . * * * ' ' ' ' : 4-24
;I,": MODEL 1743 MAINTENANCE KIT. .... : : : : ...... : : : : : : : : . 4-26
4-10. MODEL 1723 IEEE INTERFACE ........................ 4-25
!
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INSTRUCTION MANUAL
Dlgllel Mulllmeler
Model 174
CONTENTS (Cont'd)
#ection Page
15 . THEORY OF OPERATION . . . . . . . . . . . . . . . . . . . . . . 5-l
5-l. GENERAL.........................::::::::5-,
5-2. SIGNALFLOW............................... 5-l
5-3. SWITCHING (Schematic 27935E). . . . . . . . . . . . . . . 5-2
5-4. NANOVOLT PREAMP (Schematic 279370 E block diagram, Figur; i2.j : : : : : . 5-4
MODEL 1740 AC OPTION (Schematic 279440) . 5-5
MODEL 1744 OHMS OPTION (Schematic 27941Cj : : : : : : : : : : 1 : : : : . 5-8
MODEL 1745 AMMETER OPTION (Schematic 2794OC). . . 5-12
5-8. ANALOG-TO-DIGITAL CONVERTER (Schematic 2J936F). : : : : : : : : : : : : , 5-12
5-9. DISPLAY BOARD (Schematic 279391)). . . 5-21
5-10. DIGITAL BOARD (Schematic 28209E). . : : : : : : : : : : : : : : 1 : : : . 5-23
5-l I. POWER SUPPLY (Schematic 279380) . . . . . . . . . . . . 5-25
MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . : : : : : : : : : 6-1
' 6-1. GENERAL.................................6-I
6-2. REQUIRED TEST EQUIPMENT . . . . . . . . . . . . . . . . . . . . . , . . . 6-1
6-3. PERFORMANCE VERIFICATION . . . . , , . . . . . . . . . . . . . , . . , . 6-1
6-4. ADJUSTMENT/CALIBRATION PROCEDURE . . . . . . . . . . . . . , . . . . . . 6-g
6-5. TROUBLESHOOTING. . . . . . . . . . . . . . . . . . , . . . . . . . . . . 6-21
7 REPLACEABLE PARTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-l
* J-l. GENERAL...... . . . . . . . . . . . . . . . . . . . . . . . . ...7-I
7-2. ORDERING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . 7-l
7-3. SCHEMATICS . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-l
i
AA ii;
INSTRUCTION MANUAL
Dlgital Multlmeter
Model174
ILLUSTRATIONS
igure No. Title Page
I Dimensional Data ........................... v
2 Rear Panel Connections ........................ 1-2
View of Chassis With Cover Removed . . 1-4
T, Installation of Models 1740, 1744, 1745: : : : : : : : : : : : : : : : 2-3
Typical Display For Non-Valid Function ................ 3-2
65 Front Panel Controls and Input Terminals ............... 3-4
Manual Ranging on the Model 174. ................... 3-5
ii Model 1728 Rechargeable Battery Pack ................. 4-3
9 Installation of Model 1728 ...................... 4-4
IO Installation of Model 1722 Digital Interface ............. 4-7
Ila Connector Pin Identification For Model 174/1722. ........... 4-9
lib Connector Pin Identification For Model 174/1722. ........... 4- I(
Installation of Model 1722 Digital Interface ............. 4- 11
6 Location of Jumpers t Pull-Ups For Model 1722. ............ 4-l:
14 Model 1722 Block Diagram ....................... 4-I(
15 Model 1007 Dual Rack Mounting Kit. .................. 4- 2C
16 Model 2000 Rack Mounting Kit ..................... 4-2;
17 Model 1746A Low-Thermal Shorting Plug ................. 4-Z:
18 Model 1747A Low-Thermal Cable Set ................... 4-Z!
I9 Model 1743 Maintenance Kit ...................... 4-2;
20 Typical Installation of Extender Card on Model 1722. ......... 4-2t
21 Diagram of Signal Flow ........................ 5-l
22 Simplified Diagram of Nanovolt Preamp. ................ 5-4
23 Diagram of AC Attenator (Model 1740) ................. 5-5
24 Diagram of AC/DC Converter (Model 1740). ............... 5-7
Simplified Diagram of Model 1744 Ohms Option ............. 5-9
2 Detailed Diagram of Model 1744 Ohms Option .............. 5-IC
27 Basic Functional Blocks of A/O Converter ............... 5-1:
28 Basic Charge Balance Converter .................... 5-IL
Operating Waveforms of A/D Converter ................. 5-11
:: Simplified Schematic ......................... 5-1;
Simplified Diagram of Complete A/O Converter ............. 5-2C
:: A/O Converter System Timing. ..................... 5-21
Digital Display Multiplex Scheme ................... 5- 2i
;t Test Circuit For 30 mV DC Accuracy Check ............... 6-3
35 Test Circuit For 3uA Verification. .................. 6-7
36 Model I74 Top View With Cover Removed. ................ 6-1~
37 Model I74 Calibration Adjustments. .................. 6-11
38 Waveform For A/D Calibration ..................... 6-11
Model I74 Chassis Assembly ...................... 6-25
2'0 Model I74 Bottom Cover Assembly. 6-21
41 Component Layout, PC-412 (Part I). ....................... : : 1 : : : : 7-53
Component Layout, PC-412 (Part 2). .................. 7-54
:: Component Layout, PC-421 ....................... 7-57
Component Layout, PC-410 ....................... 7-58
2: Component Layout, PC-414 ....................... 7-59
Component Layout, PC-408 ....................... 7-60
:; Component Layout, ~~-409 ....................... 7-61
48 Componen r. Layout, Model 1728 ..................... 7-62
49 Component Layout, Model 1722, Upper Board (PC-415) . * * . . * . + ' ' 7-67
50 Component Layout, Model 1722, Lower Board (PC-416) * * * * . * * ' ' * J-65
iv BB
INSTRUCTION MANUAL
Dlgital MullimeIer
Model 174
SPECIFICATIONS
AS AN AUTOJMANUAL RANGINQ DC VOLTMETER
WITI AUTO/MANUAL RANGING AC VOLTAGE OPTION ,740 ASANACAMMSTER WlTHOPTlONSl740ANO~7~5
vi AA
INSTRUCTION MANUAL
DigItat MultImeter
Model 174
8.5" (217mm)
t
I
FIGURE I. Dimensional Data.
INSTRUCTION MANUAL GENERAL INFORMATION
DigItal MultImeter
Model 174
SECTION I. GENERAL INFORMATION
l-l. INTRODUCTION. The Model 174 Digital Multimeter is a wide-range, general purpose
measuring instrument, capable of measuring ac/dc voltage, ac/dc current, and resistance.
l-2. FEATURES.
a. Standard
I. Sensitivity to 0.1 microvolt dc.
2. 30000 count display for high resolution.
0.013% basic dc accuracy
t : Manual, automatic or remote ranging.
5. Lo to CASE isolation to 10'0.
b. Optional.
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. WARRANTY INFORMATION. The warranty is stated on the inside front cover of the
manua I . If there is a need for service, contact your Keithley representative or author-
ized repair facility as given on the inside front cover of this manual.
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.
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 hand-
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. 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.
1-l
AA
GENERAL INFORMATION INSTRUCTION MANUAL
Digital Multimeter
Model 174
3mV DC,
REMOVE TOP COVER 30mV DC, CONNECTION TO
'HILLIPS TO GAIN ACCESS ANALOG MODEL 1722 OR PHILLIPS
iCREWS TO CHASSIS (4 SCREWS) OUTPUT 1723 INTERFACE SCREWS
LINE LiNE
FUSE INPUT
F401 P405
FIGURE 2. Rear Panel Connections.
l-2 AA
INSTRUCTION MANUAL GENERAL INFORMATION
Dlgltat MultImeter
Model 174
TABLE I-l
Summary of Options and Accessories
ptions: Remarks:
Model 1740 AC Option Factory or Field-Installed. To field-
install, refer to Section 2, paragrap" 2-3~
Model 1744 Ohmmeter Option Factory or Field-Installed. To field-
install, refer to Section 2, paragraph Z-3d
Model 1745 Ammeter Option Factory or Field-Installed. To field-
install, refer to Section 2, paragraph 2-3e
upplied Accessories:
Model 1746~ Low-Thermal Short See ACCESSORIES, Section 4, paragraph 4-7a.
mther Accessories:
Model 1600 High Voltage Probe See ACCESSORIES, Section 4, paragraph 4-5a.
Model 1651 50-Ampere Shunt See ACCESSORIES, Section 4, paragraph 4-5b.
Model 1682 RF Probe See ACCESSORIES, Section 4, paragraph 4-5~.
Model 1685 Clamp-On AC Current Probe See ACCESSORIES, Section 4, paragraph 4-jd.
Model 1722 Digital Interface See ACCESSORIES, Section 4, paragraph 4-3.
Model 1723 IEEE Interface Described in separate Instruction Manual.
Model 1727 Digital Interface Cable Set See ACCESSORIES, Section 4, paragraph 4-8.
Model 1728 Rechargeable Battery Pack See ACCESSORIES, Section 4, paragraph 4-2.
Model 1743 Maintenance Kit See ACCESSORIES, Section 4, paragraph 4-9.
Modell747A Low-Thermal Input Leads See ACCESSORIES, Section 4, paragraph 4-7b.
BB l-3
INSTRUCTION MANUAL
GENERAL INFORMATION Digital Multimeter
Model 174
LINE
SWITC :HES -
-MOUNTING
BRACKET
SHIELD FOR
'NANOVOLT
PREAMP
MODEL 1740
VIOLET WIRE
,TO MODEL
1740
MODEL 1744
MODEL 1745 -FUSE
FIOOI
FIGURE 3. View of Chassis With Cover Removed.
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INSTRUCTION MANUAL INITIAL PREPARATION
Dlgltal Multlmeter
Model 174
SECTION 2. INITIAL PREPARATION.
2-l. GENERAL. This section provides information needed for incoming inspection and
preparation for use.
2-2. INSPECTION. The Model 174 was carefully inspected both mechanically and electricai-
ly before shipment. Upon receiving the instrument, check for any obvious damages 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 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. If any one of accessory
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. If any of the Models 1740, 1744, 1745 Options
are to be field-installed, the top cover must be removed and the installation procedures
in following paragraphs c, d, and e must be used.
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.
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 a SHOCK
HAZARD.
TABLE 2-l.
Summary of Line Voltage Settings
b. Line Fuse Requirement. The Model 174 uses a single line fuse to protect the
line-operated power supply. The fuse is a 3 AE, slow-blow type. Verify that the
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.
2-l
INITIAL PREPARATION INSTRUCTION MANUAL
Digital MultImeter
Model 174
C. How to Install the Model 1740 AC VOLTS Option. Cut the tie wrap holding the "violet"
wire. Connect the "violet" input lead (P301) coming from the Function Switch to Jl203.
Install the plug-in board for the Model 1740 on the Model 174 chassis at PSOI and P502
as shown in Figure 4. The plug-in board (PC-414) edges should mate with the teflon card
edge guides which support the board. The component side of PC-414 faces the front of the
instrument.
IMPORTANT
The AC VOLTS circuit must be calibrated prior to use as in Section 6-4e.
d. How to Install the Model 1744 OHMS Option. The plug-in board (PC-408) for the Model
1744 is installed on the Model I74 chassis at P503 as shown in Figure 4. The component
side of ~~-408 faces the front of the Instrument.
IMPORTANT
The entire 174 Calibration Procedure must be performed prior to use as in Section 6-4.
e. How to Install the Model 1745 AMPERES Option. The plug-in board (PC-409) for the
Model 1745 is installed on the Model I74 chassis at P504 and P505 as shown in Figure 4.
The component side of PC-409 faces the front of the instrument. Check fuse FIOOI for
proper rating and condition. Replacement fuse is a Keithley Part No. FU-39; 4 amperes
rating.
IMPORTANT
The AMPERES circuit must be calibrated prior to use as in Section 6-49.
2-2 AA
INSTRUCTION MANUAL INITIAL PREPARATION
Digital Mulllmeler
Model 174
FIGURE 4. Installation of Models 1740, 1744, 1745.
2-3
NITIAL PREPARATION INSTRUCTION MANUAL
Digital Multimeter
Model 174
TABLE 2-2.
Summary of Detailed 74 Max Rating at Input Terminals
FUNCTION HI TO LO MAXIMUM
DC VOLTS
300 mV - 1 KV 12OOV Peak
3 mV and 30 mV 250V RMS sine, <60Hz or 250~
Peak .
AC VOLTS IOOOV RMS, ,
OHMS 240V RMS sine, ~60Hz or 350~
Peak ,
AMPS
3OOpA-3A 4A, ~250~ PK or c60Hz RMS if
fuse blows
30~A 25mA or 25OV RMS on fixed range
I- 3uA 2.5mA or 25OV RMS on fixed range
2-4 AA
INSTRUCTION MANUAL OPERATING INSTRUCTIONS
DIgItal MultImeter
Model 174
SECTION 3. OPERATING INSTRUCTIONS.
3-l. GENERAL. This section provides information needed to operate the Model 174 for
measurement of voltage, current, and resistance, when the appropriate option is installed.
3-2. HOW TO SELECT POWER. The Model 174 may be powered from line voltage or recharge-
able nickel-cadmium batteries. The Model 1728 must be installed to permit battery opera-
tion. The I ine-voltage supply is built-in. The power cord is detachable and is 6 feet
(2 m) long.
NOTE
The accessory Model 1728 Rechargeable Battery Pack may be ordered at the time of
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. The Model 174 can be powered from line voltage over
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.
1. Set the internal line voltage switches (S4Ol and 5402) to the appropriate position
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, order Keithley Model 7003 Power
Cord (2 foot long).
3. Check the line fuse for proper rating as described in Section 2, paragraph 2-3,
4. Plug the line cord into a source of line power.
5. Depress LINE pushbutton.
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.
I. Install the Model 1728 Rechargeable Battery Pack. (See Section 4, paragraph 4-Z.)
2. Depress BAT pushbutton.
3. If the LOW BAT indicator is lighted in BAT mode, refer to Section 4-2~ for re-
charging; otherwise, the Model 174 may be used for measurements.
3-l
OPERATING INSTRUCTIONS INSTRUCTION MANUAL
Digital Multimeter
Madei 174
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 I6 hours, the Model 174 can be powered continuously for
at least 3 hours.
TABLE 3-2.
Summary of Operation in Line and Bat Modes
Condition of Instrument
Line Power Connected Line Power Connected Line Power Not Connected
Button Depressed 1728 Not Installed 1728 Installed 1728 Installed
LINE ON ON OFF
Batterv trickle charaed.
BAT OFF ON ON
Battery slowly discharged.
NEITHER OFF OFF OFF
LINE NOR BAT Battery charged at maximum
rate.
LIGHTED DECIMAL 60lNTS.
FIGURE 5. Typical Display For Non-Valid Function.
3-2 AA
INSTRUCTION MANUAL OPERATING INSTRUCTIONS
Dlgltal MultImeter
Model 174
3-3. HOW TO SELECT FUNCTION. Function is selected by means of a front panel rotary
switch (5302).
a. V AC (~1. When the Function Switch is set to V AC the Model 174 will be set to
ac voltage function. Refer to paragraph 3-6 for operating information.
IMPORTANT
The Model I74 can be used to measure ac voltage only when the Averaging AC Voltage
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 5.
b. vDc(=) . When the Function Switch is to V DC the Model 174 will be set to dc
voltage function. Refer to paragraph 3-b for operating information.
When the Function Switch is set to HI0 or LOR the Model I74 will be sef
to -9res 1stance ohms) function. Refer to paragraph 3-6 for operating information.
IMPORTANT
The Model 174 can be used to measure resistance only when the Ohmmeter Option 1744 is
installeo: If this option is not installed, the Model 174 will display all four deci-
mal points to indicate a non-valid function as shown in Figure 5.
1. HIR. When the FUNCTION Switch is set to Hln, the Model I74 permits resistance
measurements in 6 ranges from 3K0 to 300MO. Full range voltage is 3 V.
2. LOR. When the FUNCTION Switch is set to LOQ, the Model I74 permits resistance
measurements in 6 ranges from 300~ to 30MR. 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. If this option is not installed the Model 174 will display all four
decimal points to indicate a non-valid function as shown in Figure 5.
e. A AC ("J). Whkn the FUNCTION Switch is set to A AC the Model I74 will be set to
ac current function. Refer to paragraph 3-7 for operating information. Neither
autoranging nor remote ranging are available on Amperes.
IMPORTANT
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 I74 will display all four decimal points to indicate a non-valid function
as shown In Figure 5.
AA 3-3
OPERATING INSTRUCTIONS INSTRUCTION MANUAL
Digital Multimeter
Model 174
LOW mv FUNCTION
BATTERY ZERO -`ITCH
LINE BAT SEE FIGURE 7 VALID FOR CASE INPUT INPUT
FOR RANGE SELECTION VOLTS AND GROUND LO HI
PZN OHMS ONLY J304 J303
DETAILS J302
FIGURE 6. Front Panel Controls and Input Terminals.
3-4 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.
a. Manual Ranging. (Al I functions). The Model 174 can be set to Hanual Mode by depress-
ing the appropriate range pushbutton. See Figure 7 for detailed explanation of manual
ranging. NOTE
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. The Model
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). Remote ranging is available only when
the Model 1722 or Model 1723 is installed and the REM oushbutton is depressed. Refer to
Section 4 ACCESSORIES for information regarding Models I722 or 1723.
NOTE
The REM pushbutton determines range control only, and does not affect timing controls,
Trigger, Hold, and Trigger Mode.
C. Autoranging. (V AC, V DC, and OHMS only). The Model I74 will be placed in Auto-
ranging mode under the following conditions.
I. If AUTO is depressed the Model I74 will be set to autoranging mode.
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.
FIGURE 7. Manual Ranging on the Model 174.
AA 3-5
OPERATING INSTRUCTIONS INSTRUCTION MANUAL
Digital Multimeter
Yodet~74
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).
3-5. HOW TO MEASURE VOLTAGE. The Model 174 measures dc voltage in seven ranges: 3mV,
30mV, 300mV, 3V, 3OV, 3OOV, and IOOOV DC. When the Model 1740 Option is installed, the
Model 174 measures ac voltage in five ranges, 300 mV, 3V, 3OV, 3OOV, and IOOOV.
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 voltages
or damage to the instrument will occur.
TABLE 3-3.
Maximum Allowable Continuous Input
IOOOV rms ( 1000~ rms ( IOOOV rms (*107V.Hr 1200V Peak
IOOOV rms ( 1OOOV rms (
*NOTE
When 3mV or 30mV range pushbuttons are depressed, the 300mV range will be selected
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. The display blinks above 1200.0
volts on the highest range.
1. Select V DC on Switch 5302.
2. Depress AUTO, REM or desired Manual Range pushbutton.
3. Connect the signal to be measured between HI and LO terminals. The terminals are
designed to accept banana or "bunch pin" plugs, such as the accessory Keithley Model
1747 Low-Thermal coaxial input cable. These leads are recommended for measurements
below IO microvolts dc resolution.
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.
A "zero" reading will always be displayed as -.OOOO.
3-6 AA
INSTRUCTION MANUAL OPERATING INSTRUCTIO