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Instruction Manual
Model 175
Autoranging Multimeter
01983, Keithley Instruments, Inc.
Cleveland, Ohio, U.S.A.
Document Number 175-901-01
SPECIFICATIONS
TABLE OF CONTENTS
Paragraph Title Peg.3
`SECTION l-GENERAL INFORMATION
1.1 Introduction ............................. ................. ...... .......... ...... 1-l
1.2 Getting Started .......................... ................. ...... .......... ...... 1~1
1.3 Unpacking and Inspection ................. ................. ...... .......... ...... l-l
1.4 Specifications ........................... ................. ...... 1-2
1.5 Warranty Information ..................... ................. ...... .......... l-2
1.6 Manual Addenda ......................... ................. ...... 1-2
1.7 Safety Symbols and Terms. ................ ................. ...... .......... 1-2
1.8 Optional Accessories. ..................... ................. ...... .......... 1-2
SECTION 2-BENCH OPERATION
2.1 Introduction .................................... 2-1
2.2 High Energy Circuit Precautions. ................... 2-1
2.3 Preparation for Use .............................. 2~1
2.3.1 LinePower.. ................................. 2-l
2.3.2 Battery Pack Power. ........................... 2-l
2.3.3 Batten, Charging .............................. 2-1
2.4 Front Panel Familiarization ........................ 2~2
2.4.1 Display ...................................... 2-2
2.4.2 Front Panel Controls ........................... 2-2
2.4.3 Input Terminals ............................... 2-3
2.4.4 Current Fuse Replacement ...................... 2-3
2.5 Error Messages ................................. 2-3
2.6 Operating Conditions ............................ 2-3
2.6.1 Environmental Conditions. ...................... 2-3
2.6.2 Maximum Allowable Input ...................... 2-4
2.7 Basic Bench Measurements ....................... 2-4
2.7.1 Power-Up .................................... 2-4
2.7.2 Relative Mode ................................ 2-4
2.7.3 DC Voltage Measurements. ..................... 2-4
2.7.4 TRMS AC Voltage Measurements. ...............
2.7.5 Resistance Measurements ......................
2.7.6 Current Measurements (DC or TRMS AC) .........
2.7.7 AC Plus DC Measurements .....................
2.7.8 dl3 Measurements .............................
2.7.9 dl3 Measurement Considerations and Applications
2.7.10 MINtMAX and 100 Point Logger Operation .......
2.7.11 DiodeTest ................................... 2-9
2.8 TRMS Consideration ............................. 2-9
2.8.1 AC Voltage Offset ............................. 2-9
2.8.2 TRMS Measurements Comparison ...............
2.8.3 Crest Factor ..................................
2.8.4 Extended Frequency Response ..................
SECTION 3-PERFORMANCE VERIFICATION
3.1 Introduction .................................... ..........
3.2 Environmental Conditions ......................... .......... ......
3.3 Recommended Test Equipment. ................... .......... ......
3.4 Initial Conditions ................................ .......... ......
3.5 Verification Procedure ............................ ..........
3.5.1 DC Voltage Accuracy Check .................... .......... ......
3.5.2 AC Voltage Accuracy Check .................... .......... ... .. 3-2
3.5.3 Resistance Accuracy Check ..................... .......... ...... 3-2
3.5.4 DC Current Accuracy Check .................... .......... 3-2
3.5.5 AC Current Accuracy Check .................... .......... 3-3
TABLE OF CONTENTS
Paragraph Title Page
SECTION 4-THEORY OF OPERATION
4.1 Introduction .................................................................................. 4-l
4.2 Overall Functional Description ................................................................... 4-1
4.3 AnalogCircuitry ............................................................................... 4-l
4.3.1 Multiplexer ................................................................................. 4-2
4.3.2 InputBufferAmplifier ........................................................................ 4-2
4.3.3 ~2VRefetenceSource ........................................................................ 4-2
4.3.4 AiDConverter .............................................................................. 4-2
4.3.5 Input Signal Conditioning ..................................................................... 4-3
4.3.6 ACConverter ............................................................................... 4-4
4.4 DigitalCircuitry ............................................................................... 45
4.4.1 Microcomputer ............................................................................. 4-5
4.4.2 AddressDecoding ........................................................................... 4-5
4.4.3 PIA ....................................................................................... 4-5
4.4.4 Display Board ............................................................................... 4-5
4.5 DigitalCalibration ............................................................................. 4-5
4.6 PowerSupply ................................................................................ 4-5
4.7 Model17588atten/Option ...................................................................... 4-5
SECTION 5-MAINTENANCE
5.1 Introduction .................................................................................. 5-1
5.2 Top Cover Removal/Installation ................................................................. 5-l
5.3 Batten/ Pack (Model 1768) Installation ............................................................. 5-l
5.4 Troubleshooting .............................................................................. 5-l
5.4.1 RecommendedTestEquipment ................................................................ 5-l
5.4.2 SelfDiagnosticProgram ...................................................................... 5-2
5.4.3 PowerSupplyChecks ........................................................................ 5-4
54.4 AfDConverterandDisplay ................................................................... 5-4
5.4.5 Signalconditioning .......................................................................... 5-4
5.5 LineFuseReplacement ......................................................................... 5-6
5.6 Special Handling of Static Sensitive Devices ....................................................... 5-6
5.7 Front Panel Calibration ......................................................................... 5-7
5.7.1 Recommended Calibration Equipment .......................................................... 5-7
5.7.2 CalibrationJumper.. ........................................................................ 5-7
5.7.3 Environmentalconditions ..................................................................... 5-7
5.7.4 DC Voltage Calibration ....................................................................... 5-7
5.7.5 ACVoltageCalibration .........................................................................
5.7.6 Resistance Calibration. ....................................................................... 5-8
5.7.7 Frequencycompensation ..................................................................... 5-8
5.7.8 CalibrationStorage ............................................................................ 59
SECTION 6-REPLACEABLE PARTS
6.1 Introduction .................................................................................. 6-l
6.2 ReplaceableParts ............................................................................. 6-l
6.3 Orderinginformation ........................................................................... 6-l
6.4 FactoryService.. ............................................................................. 6-l
6.5 Component Location Drawings and Schematic Diagrams ........................................... 6-l
LIST OF ILLUSTRATIONS
Figure Title Page
2-1 Model175FrontPanel .................................................. 2-2
2-2 DC Voltage Measurements. .............................................. 2-5
2-3 TAMS AC Voltage Measurements. ........................................ 2-5
2-4 Resistance Measurements ............................................... 2-6
2-5 Current Measurements Between 2000mA and 20A. .......................... 2-6
2-6 Current Measurements up to 2000mA ..................................... 2-6
2-7 Model 175 Typical AC Frequency Response ................................ 2.11
4-1 Simplified Block Diagram ................................................ 4-l
4-2 Simplified Schematic of the Multiplexer .................................... 4-2
4-3 Simplified Schematic of the Input Buffer Amplifier ........................... 4-2
4-4 AIDConverter ......................................................... 4-3
4-5 Resistance Measurements Ratiometric Technique. ........................... 4-4
4-6 Simplified Schematics of Ohms Circuitry ................................... 4-4
5-l Segment Identification .................................................. 5-2
5-2 CalibrationJumper.. ................................................... 5-9
6-l Modell75ExplodedView ................................................ 6-2
6-2 Model 175 Display Assembly ............................................. 6-3
6-3 Display Board, Component Location Drawing, Dwg. No. 175-110. .............. 6-9
6-4 Model 1758 Battery Pack, Component Location Drawing, Dwg. No. 1755.100 .... 811
6-5 Mother Board, Component Location Drawing, Dwg. No. 175-100 .............. 6-13
6-6 Mother Board, Schematic Diagram, Dwg. No. 175.106 ....................... 6-17
6-7 Display Board, Schematic Diagram, Dwg. No. 175.116 ....................... 6-21
6-8 Model 1758 Battery Pack, schematic Diagram, Dwg. No. 1758-106 ............. 6-23
iii
LIST OF TABLES
Table Title Page
2-l ErrorMessages ..................................... ...... ...... ...... ......
2-2 Model 175 Maximum Allowable Inputs .................. ...... ...... ...... ...... ......
2-3 dB Specifications for DC Volts (6OOL1Refl ............... ...... ...... ...... ...... ......
2-4 d8 Specifications for AC Volts (6OOfl Refl ............... ...... ...... ...... ...... ......
2-5 Levels for Other Reference Impedances ................. ...... ...... ...... ...... ......
2-6 Comparison of Average and TRMS Meter Readings ....... ...... ...... ...... ...... ......
3-l Equipment Specifications. ............................ ...... ...... ...... ...... ......
3-2 Limits for DC Voltage Verification ...................... ...... ...... ...... ...... ......
3-3 Limits for AC Voltage Verification ...................... ...... ...... ...... ...... ......
3-4 Limits for Resistance Verification ....................... ...... ...... ...... ...... ......
3-5 Limits for DC Current Verification ...................... ...... ...... ...... ...... ......
5-l Recommended Troubleshooting Equipment. ............. ...... ...... ......
5-2 Troubleshooting Modes .............................. ...... ...... ...... ...... ......
5-3 Power Supply Checks. ............................... ...... ...... ...... ...... ......
5-4 A/D Converter Checks ............................... ...... ...... ...... ...... ......
5-5 Display Board Checks.. .............................. ...... ...... ...... ...... ......
5-6 Static Sensitive Devices .............................. ...... ...... ...... ...... ......
5-7 Recommended Calibration Equipment .................. ...... ...... ...... ...... ......
5-8 DC Voltage Calibration ............................... ...... ...... ...... ...... ......
5-9 AC Voltage Calibration ............................... ...... ...... ...... ...... ......
5-10 Resistance Calibration. ............................... ...... ...... ...... ...... ......
6-l MotherBoard,PartsList .............................. ...... ...... ...... ...... ......
6-2 Display Board, Parts List. ............................. ...... ...... ...... ...... ......
6-3 Model 1758 Battery Pack, Parts List .................... ...... ...... ...... ...... ......
6-4 Model 1758 Spare Pats List. .......................... ...... ...... ...... ...... ......
iv
SAFETY PRECAUTIONS
The following safety precautions should be observed before operating
the Model 175.
This instrument is intended for use by qualified personnel who
recognize shock hazards and are familiar with the safety precautions re-
quired to avoid possible injury. Read over the manual carefully before
operating this instrument.
Exercise extreme caution when a shock hazard is present at the instru-
ment's input. The American National Standards Institute (ANSI) states
that a shock hazard exists when voltage levels greater than 30V rms or
42.4V peak are present. A good safety practice is to expect that a
hazardous voltage is present in any unknown circuit before measuring.
Inspect the test leads for possible wear, cracks or breaks before each
use. If any defects are found, replace with test leads that have the same
measure of safety as those supplied with the instrument.
For optimum safety do not touch the test leads or the instrument while
power is applied to the circuit under test. Turn the power off and
discharge all capacitors, before connecting or disconnecting the instru-
ment.
Do not touch any object which could provide a current path to the
common side of the circuit under test or power line (earth) ground.
Always make measurements with dry hands while standing on a dry,
insulated surface, capable of withstanding the voltage being measured.
Exercise extreme safety when testing high energy power circuits (AC
line or mains, etc.). Refer to the operation section.
Do not exceed the instrument's maximum allowable input as defined in
the specifications and operation section.
MODEL 175 AUTORANGING DMM
Features: l dBm/Relative Functions
l Min/Max Reading Hold
04% Digit LCD Display *Safety Input Jacks
*Fast Autoranging *lOA Capability
*Bench or Portable l lOOkHz Specified AC Bandwidth
*Digital Calibration
l lOO Point Data Logger Options:
l 10~V/10mW10nA Sensitivity *Model 1758 Rechargeable Battery Pack
~0.03% Basic DCV Accuracy
l TRMS AC *Model 1753 IEEE-488 Interface
SECTION 1
GENERAL INFORMATION
1.1 INTRODUCTION D. Select DC volts by releasing (outi the AC DC
pushbutton (V still selected]. The AC annunciator will
This instruction manual contains the necessary information turn off.
for operating and maintaining the Model 175 Autoranging E. Select autoranging ohms by pressing in the !!
Multimeter and the Model 1758 Rechargeable Battery Pack. pushbutton (DC still selected) and AUTO pushbutton.
The information is divided into the following sections: The n annunciator will turn on. Press the AC:DC
Section 1 contains general information and provides pushbutton in (AC selected) and note the "Err"
guidelines for using this manual. Important safety infor- message indicating that this is an invalid mode.
mation is also presented here. F. Select AC or DC current by setting the AC DC
Section 2 contains detailed bench operation information pushbutton accordingly and pressing I,? ihe A
for the Model 175. pushbutton. The annunciator that reflects the selected
Section 3 contains the information needed to verify the range will turn on. Note that current will not autorange
accuracy of the Model 175. Performance verification can and that the 10 AMPS and COM input jacks must be
be done upon receipt of the unit or whenever the basic used on the 10A range.
accuracy is in question. G. Select dB by placing the Model 175 in AC or DC volts
For the more technically oriented, information on theory and pressing the dB pushbutton. The dB annunc~etor
of operation, and maintenance and servicing is contained will turn on. Press the dB button again fo take the
in Section 4 through 6. Model 175 out of the dB measurement mode.
H. REL (relative) can be used with any measurement furw
NOTE tion: volts, ohms, amps or dB. For example, place the
The Model 1753 IEEE-488 interface comes sup- Model 175 in ohms and autorange. The display wll
plied with its own instruction manual. read approximately 00.141!, which is the test lead
resistance. Press the REL pushbutton. The REL any
nunciator will turn on and the display will now reed
1.2 GE-iTING STARTED
OO.OOI2. The relative level of 0.1411 will be subtracted
from all subsequent ohm measurements. Press the
Perform the following steps in sequence to acquaint yourself
REL pushbutton a second time to cancel the REL
auicklv and safelv with the basic operation of the Model 175.
level.
Verify that the Model 175 was not damaged in transit, es
explained in paragraph 1.3. I. To activate the 100 point DATA LOGGER with
MIN/MAX, press and hold in the STOiCLR pushbut-
Carefully read the safety precautions and warnings found
preceding this section and the first two sections (General ton. When the reading rate A = 0 is displayed let go of
the button, The ST0 annunciator will turn on Press
Information and Bench Operation) of this manual.
the RCL pushbutton and the last data point will be
Referring to paragraph 2.3.1 (Line Power) set the line displayed briefly followed by the reading (data]. Other
voltage switch and plug the power cord into a properly data points can be displayed by holding in the RCL but-
grounded outlet. If the optional battery pack is installed ton. Turn off the DATA LOGGER by pressing the
the charge circuitry will be activated. STOlCLR pushbutton again.
Acquaint yourself with the controls and display of the 5. When you are comfortable with the controls of the Model
Model 175 as follows: 175, go on and make the desired meaeurements using
A. Turn on the Model 175 by pressing in the ON/OFF Section 2, Bench Operation es a guide.
pushbutton. All of the zeroee will be displayed briefly.
B. Connect the supplied test leads to the 1.3 UNPACKING AND INSPECTION
VOLTS/OHMS/mA and COM input jacks, and short
them together. The Model 175 Bench DMM was carefully inspected, both
mechanically and electrically, before shipment. Upon recelv
C. Select AC volts and autoranging by pressing in the
ing the Model 175, carefully unpack all items from the ship-
AC/DC, V and AUTO pushbuttons. The AC, mV and
ping carton and check for any obvious signs of physical
AUTO annunciators will be displayed. Pressing any of
damage that might have occurred during shipment. Report
the other range pushbuttons will put the Model 175 in
the damage to the shipping agent immediately. Retain the
manual ranging es indicated by the absence of the
AUTO annunciator.
1-l
original packing materials in case reshipment becomes Model 1017 Dual Rack Mounting Kit-Use to mount two
necessan/. The following items are included with every Model Model 175's in a standard 5 x X 19" rack.
175 order: Model 1301 Temperature Probe-A rugged low cost
temperature probe designed to allow precision temperature
*Model 175 Autoranging Multimete! measurements from -55OC to 150◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo