GW Instek GOM-802 User manual

D.C. Milli-Ohm Meter
GOM-802
USER MANUAL
GW INSTEK PART NO. 82OM-80200MF1
ISO-9001 CERTIFIED MANUFACTURER

This manual contains proprietary information, which is protected by
copyright. All rights are reserved. No part of this manual may be
photocopied, reproduced or translated to another language without
prior written consent of the Good Will company.
The information in this manual was correct at the time of printing.
However, Good Will continues to improve products and reserves
the right to change specifications, equipment, and maintenance
procedures at any time without notice.
Good Will Instrument Co., Ltd.
No. 7-1, Jhongsing Rd., Tucheng Dist., New Taipei City 236, Taiwan.

Table of Contents
3
Table of Contents
SAFETY INSTRUCTIONS ....................................................4
Safety Symbols....................................................4
Safety Guidelines ................................................5
GETTING STARTED............................................................8
GOM-802 Characteristics....................................9
Key Features...................................................... 11
Front Panel Overview ........................................ 12
Rear Panel Overview ......................................... 16
Set Up ............................................................... 17
MEASUREMENT...............................................................21
Measurement Overview .................................... 22
Resistance Measurement .................................. 23
Compare Function............................................. 26
Temperature Measurement ............................... 32
Temperature Compensation .............................. 34
HANDLER/SCAN/ INTERFACE.........................................36
Handler Overview ............................................. 37
Scan Overview................................................... 38
Configure Interface ........................................... 42
FAQ ..................................................................................45
APPENDIX........................................................................46
Fuse Replacement ............................................. 47
Temperature Measurement ............................... 48
Specifications.................................................... 51
Declaration of Conformity................................. 54
INDEX ..............................................................................55

GOM-802 User Manual
4
SAFETY INSTRUCTIONS
This chapter contains important safety instructions that
you must follow when operating the GOM-802 or when
keeping it in storage. Read the following before any
operation to insure your safety and to keep the
GOM-802 in the best possible condition.
Safety Symbols
These safety symbols may appear in this manual or on the GOM-802.
WARNING
W
arning: Identifies conditions or practices that could
result in injury or loss of life.
CAUTION
Caution: Identifies conditions or practices that could
result in damage to the GOM-802 or to other properties.
DANGER High Voltage
A
ttention Refer to the Manual
Protective Conductor Terminal
Earth (ground) Terminal
Do not dispose electronic equipment as unsorted
municipal waste. Please use a separate collection facility
or contact the supplier from which this instrument was
purchased.

SAFETY INSTRUCTIONS
5
Safety Guidelines
General Guideline
CAUTION
Do not place any heavy objects on the GOM-802.
Avoid severe impact or rough handling that leads to
damaging the GOM-802.
Do not discharge static electricity to the GOM-802.
Use only mating connectors, not bare wires, for the
terminals.
Do not disassemble the GOM-802 unless you are
qualified as service personnel.
(Note) EN 61010-1:2001 specifies the measurement categories and
their requirements as follows. The GOM-802 falls under category
I.
Measurement category IV is for measurement performed at the source
of low-voltage installation.
Measurement category III is for measurement performed in the
building installation.
Measurement category II is for measurement performed on the
circuits directly connected to the low voltage installation.
Measurement category I is for measurements performed on circuits
not directly connected to Mains.
Power Supply
WARNING
AC Input voltage: 100V/ 120V/ 220V/230 V AC,
50/60Hz, 27VA, 22W
The power supply voltage should not fluctuate more
than 10%.
Connect the protective grounding conductor of the AC
power cord to an earth ground, to avoid electrical
shock.
Fuse
WARNING
Fuse type:
Line Voltage Rating Fuse
100V 90-110V T0.3A 250V
120V 108-132V T0.3A 250V
220V 198-242V T0.25A 250V
230V 216-250V T0.25A 250V
Make sure the correct type of fuse is installed before
power up.
To avoid fire, only replace the fuse with the specified
type and rating.
Disconnect the power cord before fuse replacement.
Make sure the cause of a fuse blowout is fixed before
fuse replacement.

GOM-802 User Manual
6
Cleaning the
GOM-802
Disconnect the power cord before cleaning.
Use a soft cloth dampened in a solution of mild
detergent and water. Do not spray any liquid into the
GOM-802.
Do not use chemicals or cleaners containing harsh
material such as benzene, toluene, xylene, and acetone.
Operation
Environment
Location: Indoor, no direct sunlight, dust free, almost
non-conductive pollution (Note below)
Relative Humidity: < 80%
Altitude: < 2000m
Temperature: 0°C to 40°C (operation)
(Note) EN 61010-1:2001 specifies the pollution degrees and their
requirements as follows. The GOM-802 falls under degree 2.
Pollution refers to “addition of foreign matter, solid, liquid, or
gaseous (ionized gases), that may produce a reduction of dielectric
strength or surface resistivity”.
Pollution degree 1: No pollution or only dry, non-conductive pollution
occurs. The pollution has no influence.
Pollution degree 2: Normally only non-conductive pollution occurs.
Occasionally, however, a temporary conductivity caused by
condensation must be expected.
Pollution degree 3: Conductive pollution occurs, or dry,
non-conductive pollution occurs which becomes conductive due to
condensation which is expected. In such conditions, equipment is
normally protected against exposure to direct sunlight, precipitation,
and full wind pressure, but neither temperature nor humidity is
controlled.
Storage
Environment
Location: Indoor
Temperature: −10°C to 70°C
Disposal
Do not dispose this instrument as unsorted municipal
w
aste. Please use a separate collection facility or contact
the supplier from which this instrument was purchased.
Please make sure discarded electrical waste is properly
recycled to reduce environmental impact.

SAFETY INSTRUCTIONS
7
Power cord for the United Kingdom
When using the GOM-802 in the United Kingdom, make sure the power cord
meets the following safety instructions.
NOTE: This lead / appliance must only be wired by competent persons
WARNING: THIS APPLIANCE MUST BE EARTHED
IMPORTANT: The wires in this lead are coloured in accordance with the
following code:
Green/ Yellow: Earth
Blue: Neutral
Brown: Live (Phase)
As the colours of the wires in main leads may not correspond with the
coloured marking identified in your plug/appliance, proceed as follows:
The wire which is coloured Green & Yellow must be connected to the Earth
terminal marked with either the letter E, the earth symbol or coloured
Green/Green & Yellow.
The wire which is coloured Blue must be connected to the terminal which is
marked with the letter N or coloured Blue or Black.
The wire which is coloured Brown must be connected to the terminal marked
with the letter L or P or coloured Brown or Red.
If in doubt, consult the instructions provided with the equipment or contact
the supplier.
This cable/appliance should be protected by a suitably rated and approved
HBC mains fuse: refer to the rating information on the equipment and/or
user instructions for details. As a guide, a cable of 0.75mm2should be
protected by a 3A or 5A fuse. Larger conductors would normally require 13A
types, depending on the connection method used.
Any exposed wiring from a cable, plug or connection that is engaged in a live
socket is extremely hazardous. If a cable or plug is deemed hazardous, turn
off the mains power and remove the cable, any fuses and fuse assemblies. All
hazardous wiring must be immediately destroyed and replaced in accordance
to the above standard.

GOM-802 User Manual
8
GETTING STARTED
This chapter describes the GOM-802 in a nutshell,
including its main features as well as its front and rear
panels. After going through the panel overview, follow
the Power-up sequence before attempting to use the
instrument.
Please note the information in this manual was correct at
the time of printing. However as GW Instek continues
to improve its products, changes can occur at any time
without notice. Please see the GW Instek website for the
latest information and content.
Characteristics GOM-802 Characteristics.........................................9
Key Features........................................................... 11
Panel Overview Front Panel Overview............................................. 12
Rear Panel Overview .............................................. 16
Setup Tilt Stand ............................................................... 17
Power Up ............................................................... 18
4 Wire Kelvin Connection....................................... 19
Zeroing (Relative Function) ................................... 20

GETTING STARTED
9
GOM-802 Characteristics
GOM-802 is a high precision programmable DC
Milli-ohm meter suitable for low resistance
measurements of switches, relays, connectors, PCB
tracks and a variety of other devices. With the
easy-to-use features, superior performance, and
automatic test interfaces, the GOM-802 is a dependable
instrument for resistance measurements.
Easy to Use
Features
The GOM-802 includes an easy to use comparator
function (HI-LO-GO) that is able to easily set upper and
lower limits for pass/fail testing. The alarm buzzer can be
used with the comparator function. The flexible handler
interface can be used to monitor the status of the
pass/fail testing.
The relative feature enables the GOM-802 to easily
compensate for any stray resistance. Up to 20 different
sets of HI-LO-GO settings can be stored to satisfy a
number of different testing conditions. The GOM-802 is
also able to recall the last test setting that was used every
time it is turned on.
Performance The GOM-802 has nine selectable measurement ranges
from 30mΩto 3MΩ, a constant current source of 1uA
to 1A, an accuracy of 0.05%, a 1uΩresolution and
performs measurements using four wire Kelvin
connections for accurate, consistent measurements.
The ability to choose between high measurement
accuracy with 7 samples/sec (full scale at 30000) or high
speed measurements with 30 samples/sec (full scale at
3000) allows the GOM-802 the flexibility to fulfill a
number of different measurement roles.

GOM-802 User Manual
10
Temperature
Compensation
Temperature Compensation (Optional):
The optional temperature probe (PT-100) can be used to
extrapolate the resistance of a DUT at a certain
temperature. When the temperature coefficient and the
required temperature (of the resistance measurement) is
keyed in under TC mode, the GOM-802 will display the
extrapolated measurement.
Automatic
Testing
For automatic testing The GOM-802 has a handler
interface designed for automatic testing. The handler
interface outputs the status of PASS, FAIL, HI, LO,
READY and EOT signals and inputs a trigger control
signal. An RS-232 and GPIB option is also available for
computer control applications.
Applications Production testing for contact resistance of switches,
relays, connectors, cables and printed circuit boards
and other low resistance devices.
Component testing of resistors, motors, fuses and
heating elements.
Incoming inspection and quality assurance testing.
Conductivity evaluation for product design.

GETTING STARTED
11
Key Features
30,000 counts.
Measurement Range: 30mΩ~3MΩ.
0.05% accuracy.
Hi/Lo comparator and limit percentage setting with
20 memory sets.
REL, Actual and % value measurements.
Manual or Auto-ranging.
Continuous or Triggered measurement modes.
Temperature compensation and measurement.
Four-wire measurement method.
Auto-recall last setting on power-up.
Diode test.
Alarm setting for PASS/FAIL test result.
Sampling rate: 7 or 30 sampling/sec.
Standard interface: Scan/Handler, optional interfaces:
RS-232 + GPIB.

GOM-802 User Manual
12
Front Panel Overview
Power Switch
Turns On or Off the main
power. For details about the power up
sequence, see page 18.
Primary Value
Display
Shows the primary measurement results.
Normal Display
Shows the Normal (nominal) value setting.
Comparator
Indicators
The comparator indicators indicate the
status of comparison judgments.
HI: measurement exceeds the HI limit
LO: measurement exceeds the LO limit
GO: measurement is within the HI and
LO limits.

GETTING STARTED
13
Function Control
Indicators
Indicates when a function key is active.
Measurement
Terminal s
Sense HI and Sense LO terminals.
Current Source
Terminal s
Current Source Terminals, Source HI
and Source LO.
Negative
Terminal
Negative Terminal. This terminal has
the same potential as earth, but cannot
be substituted for it.
Function Keys
The COMPTEMP key activates the
comparator function. The secondary
function turns on the temperature
compensation function.
Temperature
compensation
The Cursor keys are used to edit
parameters and navigate the menu tree.
The Up/Down arrow keys are used to
change the values and range of the
different parameters.
The secondary function recalls
previously saved settings.
Recall settings
The AUTO/MANSPEED key toggles the
range between automatic and manual
and toggles between 7 samples per
second and 30 samples per second.

GOM-802 User Manual
14
Sample speed
The REL%VALUE key is used to perform
a zero adjustment to the test leads or a
DUT. Using the shift key will display
the measured values as a percentage of
the normal value.
Percentage
values
The LOCALGPIB/RS232 key will switch the
milliohm meter between local and
remote mode.
The secondary function will set the I/O
interface to GPIB or RS-232.
GPIB/
RS232 mode
Sets the High limit % values. The
secondary function activates the
Handler function.
SHIFT
HANDLER
HIGH
Handler mode
Sets the normal (Nominal) value for the
comparator function.
Scan function
Sets the lower % limit for the
comparator function and turns the
buzzer on for either a PASS or FAIL
judgment or turns the buzzer off.
Buzzer
ON/OFF

GETTING STARTED
15
Turns the external trigger on to allow
the MANUAL TRIGTRIG key to be used
as a manual trigger. The secondary
function will set the trigger to internal.
Turns the
internal trigger
ON/OFF
Enter key.
The SHIFT key is used to access the
secondary functions.
Lower Limit
Display (LO)
Displays the lower limit as as a
percentage.
Upper Limit
Display (HI)
Displays the upper limit as a percentage.
Interface
Indicator
The interface indicator shows the status
mode of the GOM-802. Remote mode
(RMT), Handler mode (HAND) or
Scan mode.

GOM-802 User Manual
16
Rear Panel Overview
AC Input
A
ccepts the power cord. AC 100/120V
or 220/230V; 50/60Hz.
For the power on sequence, see page
18.
Fuse Socket
Holds the main fuse:
100/120V: T0.3A 250V;
220/230V: T0.25A 250V;
For the fuse replacement details, see
page 47.
RS-232C port
A
ccepts an RS-232C cable for remote
control; DB-9 male connector.
For remote control details, see page 43.
GPIB port
A
ccepts a GPIB cable for remote
control (page 42).
Handler / Scan
port The Handler/Scan port is used to
output pass/fail/high/low comparison
results.
Temperature
Sensor The temperature sensor input for the
optional PT-100 temperature probe.

GETTING STARTED
17
Set Up
Tilt Stand
Steps 1. Pull handle base away from the casing.
2. Turn handle into any of the preset positions.
Stand Position Carry Position

GOM-802 User Manual
18
Power Up
1. Ensure that the correct voltage is lined up with the
arrow on the fuse cover on the rear panel.
100V 120V 220V 230V
100
220
120
230
100
220
120
230
100
220
120
230
100
220
120
230
Steps 2. Connect the power cord to the AC Voltage input.
220
100
120
230
CAUTION Ensure the ground connector of the power cord is
connected to a safety ground. This will affect the
measurement accuracy.
3. Press the main power switch on the front panel.
POWER
4. The display will light up and show the last setting
used before the last shut down.

GETTING STARTED
19
Example:
Resistance
measurement
mode
4 Wire Kelvin Connection
Background The GOM-802 uses 4 wire Kelvin connections for
accurate measurements.
Diagram
+
-
Description Source HI The Source HI carries the measuring
current source. It is connected to the +
side of the DUT.
Source LO The Source LO terminal accepts the
signal return current. Connects to the –
side of the DUT.
Sense HI Monitors the positive (+) potential.
Sense LO Monitors the negative (-) potential.
GND If the component has a large metallic
area not connected to either terminal,
connect it to ground to reduce noise.

GOM-802 User Manual
20
Zeroing (Relative Function)
Background The Relative function is used to perform a zero
adjustment on the test leads.
A
fter the Relative value is pre-set, each measurement that
is displayed is equal to the actual value – relative preset
v
alue.
If the measured value minus the relative value is a
negative, a minus sign is shown on the MSB (most
significant bit). At low measurement speeds the minus
sign will alternate with the displayed measurement.
1. Short the
cables
Short the test
cables together
using a short thick
copper wire if
necessary.
1. Set the
Reference value
Press the REL%VALUE key.
2. Relative mode
display appears
REL Indicates the Relative function is active
Note
The Auto-range function will be disabled when using
compare mode with the relative function.