GW Instek GOM-804, GOM-805 User Manual

D.C. Milli-Ohm Meter

GOM-804 & GOM-805

USER MANUAL

GW INSTEK PART NO. 82OM-80500E01

ISO-9001 CERTIFIED MANUFACTURER

Find Quality Products Online at: [e-mail]

www.GlobalTestSupply.com

Table of Contents

Table of Contents

SAFETY INSTRUCTIONS .................................................... 5

Safety Symbols .................................................... 5

Safety Guidelines ................................................ 6

GETTING STARTED ............................................................ 9

GOM-804/805 Characteristics........................... 10

Key Features ...................................................... 13

Model Lineup .................................................... 14

Front Panel Overview ........................................ 15

TFT-LCD Overview ............................................ 19

Rear Panel Overview ......................................... 21

Set Up ............................................................... 23

MEASUREMENT ............................................................... 27

Resistance Measurement .................................. 29

Compare Function ............................................. 41

Binning Function ............................................... 46

Temperature Measurement ............................... 50

Temperature Compensation .............................. 52

Temperature Conversion ................................... 56

Measurement Settings ...................................... 60

System Settings ................................................ 69

HANDLER/SCAN INTERFACE .......................................... 77

Handler Overview ............................................. 78

Pin Definitions for the Handler Interface .......... 80

Scan Overview ................................................... 82

Configure Interface ........................................... 90

SAVE/RECALL ................................................................... 99

COMMAND OVERVIEW ................................................. 102

Command Syntax ............................................ 102

Command List ................................................. 105

Find Quality Products Online at: [e-mail]

3

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

BINNing Commands ....................................... 108

Calculate Commands ...................................... 113

Memory Commands ........................................ 120

Sense Commands ............................................ 122

Source Commands .......................................... 126

Status Commands ........................................... 127

System Commands.......................................... 128

Temperature Commands ................................. 133

Trigger Commands .......................................... 138

Userdefine Commands .................................... 141

IEEE 488.2 Common Commands ..................... 143

Status system .................................................. 146

FAQ ................................................................................ 147

APPENDIX ...................................................................... 148

Temperature Measurement ............................. 149

Specifications .................................................. 152

Dimensions ..................................................... 155

Declaration of Conformity ............................... 156

INDEX ............................................................................ 157

Find Quality Products Online at: [e-mail]

4

www.GlobalTestSupply.com

SAFETY INSTRUCTIONS

WARNING

Warning: 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 instrument or to other properties.

DANGER High Voltage

Attention 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

This chapter contains important safety instructions that you must follow
when operating the GOM-804/805 or when keeping it in storage. Read the
following before any operation to insure your safety and to keep the
GOM-804/805 in the best possible condition.

Safety Symbols

These safety symbols may appear in this manual or on the GOM-804/805.

Find Quality Products Online at: [e-mail]

5

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

General Guideline

CAUTION

 Do not place any heavy objects on the instrument.
 Avoid severe impact or rough handling that leads to

damaging the instrument.

 Do not discharge static electricity to the instrument.
 Use only mating connectors, not bare wires, for the

terminals.

 Do not disassemble the instrument unless you are

qualified as service personnel.

(Note) EN 61010-1:2010 specifies the measurement categories and
their requirements as follows. The GOM-804/805 doesn’t fall
under category II, III or IV.

 Measurement category IV is for measurements performed at the

source of low-voltage installation.

 Measurement category III is for measurements performed in the

building installation.

 Measurement category II is for measurements performed on the

circuits directly connected to the low voltage installation.

Power Supply

WARNING

 AC Input voltage: 100 - 240 V AC, 50 - 60Hz, 25VA
 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.

Cleaning the
GOM-804/805

 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
instrument.

 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)

Safety Guidelines

Find Quality Products Online at: [e-mail]

6

www.GlobalTestSupply.com

SAFETY INSTRUCTIONS

(Note) EN 61010-1:2010 specifies the pollution degrees and their
requirements as follows. The GOM-804/805 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
waste. 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.

Find Quality Products Online at: [e-mail]

7

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

Green/ Yellow:

Earth

Blue:

Neutral

Brown:

Live (Phase)

Power cord for the United Kingdom

When using the instrument 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:

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 0.75mm2 should 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.

Find Quality Products Online at: [e-mail]

8

www.GlobalTestSupply.com

GETTING STARTED

Characteristics

GOM-804/805 Characteristics ................................ 10

Key Features ........................................................... 13

Model Lineup ......................................................... 14

Panel Overview

Front Panel Overview ............................................. 15

TFT-LCD Overview ................................................. 19

Rear Panel Overview ............................................... 21

Setup

Tilt Stand ................................................................ 23

Power Up ................................................................ 24

4 Wire Kelvin Connection ....................................... 25

Zeroing (Relative Function) .................................... 26

GETTING STARTED

This chapter describes the GOM-804/805 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.

Find Quality Products Online at: [e-mail]

9

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

Easy to Use
Features

Each test function on the GOM-804/805 can be easily
activated by pressing a single front panel key. All the
settings and measurement results are displayed and set on
the TFT-LCD panel at the same time making each
function naturally intuitive to use.

Each primary and secondary measurement result is
displayed prominently on the display along with any
corresponding settings. For sequential measurement
results, such as those from the scan or binning function,
are tabulated in an intuitive and easy-to-read format.

In addition, the meters can recall previously used settings
upon startup, allowing the meter to be ready the next
time it used in a matter of moments. The meters can also
save or recall up to 20 sets of function settings.

Performance

The GOM-804/805 has nine selectable measurement
ranges from 50mΩ to 5MΩ, a constant current source of
1uA to 1A, an accuracy of up to 0.05%, a 1uΩ resolution
and performs measurements using four wire Kelvin
connections for accurate, consistent measurements.

The ability to choose between high accuracy
measurements at 10 samples/sec (full scale at 50000
counts) or high speed measurements at 60 samples/sec
(full scale at 50000 counts), allows the GOM-804/805 the
flexibility to fulfill a number of different measurement
roles.

GOM-804/805 Characteristics

GOM-804 and GOM-805 are modern high precision programmable DC
Milli-ohm meters suitable for low resistance measurements of switches, relays,
connectors, PCB tracks and a variety of other devices. The meters feature a
color TFT-LCD screen with easy-to-read measurement results. With the
easy-to-use features, superior performance and automatic test interfaces, these
meters are dependable instruments for resistance measurements.

Find Quality Products Online at: [e-mail]

10

www.GlobalTestSupply.com

GETTING STARTED

Advanced
Temperature
Measurements

The GOM-804/805 has a number of advanced
temperature functions that can be used with the optional
temperature probe, PT-100.

The temperature compensation function can extrapolate
what the resistance of a DUT will be at a desired
temperature, if the temperature coefficient of the DUT
and the resistance of the DUT at ambient temperature
are known.

The temperature conversion function can be used to
extrapolate what the temperature rise of a DUT will be at
specified resistance if the initial resistance, initial
temperature and the constant for the DUT are known.

Drive Signals

The GOM-805 can select a number of different drive
signals to suit a number of different measurement
scenarios, for example the Pulse setting can be used to
cancel the effects of thermoelectric EMF on the
measurement results.

Dry Circuit
Testing

Dry circuit testing allows the GOM-805 to measure the
contact resistance of switches and connectors according
to the DIN IEC 512 and ASTM B539 standards. The
open circuit voltage will not exceed 20mV in this mode
to prevent the oxidization layer on metal switches and
connector points from breakdown. GOM-805 only.

Automatic
Testing

For automatic testing The GOM-804/805 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. Automatic testing is used with the binning,
compare and scan functions.

For computer control applications, RS-232 and USB are
standard remote interfaces, with GPIB as standard only
for the GOM-805 and GOM-804G.

Find Quality Products Online at: [e-mail]

11

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

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.

Find Quality Products Online at: [e-mail]

12

www.GlobalTestSupply.com

GETTING STARTED

 50,000 counts
 Measurement Range: 50mΩ~5MΩ
 Accuracy of up to 0.05%
 Compare function
 Binning function
 Manual or Auto-ranging
 Continuous or Triggered measurement modes
 Temperature measurement, temperature

compensation and temperature conversion

 Four-wire Kelvin measurement method
 Selectable power-on settings
 Diode test
 Alarm settings for function-specific PASS/FAIL test

results

 Sampling rate: 10 or 60 sampling/sec
 Standard interfaces:

USB/RS232/Scan/Handler/GPIB(GOM-805,
GOM-804G)

 Save/Recall settings: 20 memory sets
 External I/O logic function

Key Features

Find Quality Products Online at: [e-mail]

13

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

Feature / Mode l

GOM-804

GOM-804G*

GOM-805

Ohm Measurement

✔

✔

✔

Compare Function

✔

✔

✔

Diode Measurement

✔

✔

✔

Temp. Compensation

✔

✔

✔

Temp. Conversion

✔

✔

✔

Temp Measurement

✔

✔

✔

Dry Circuit

✘ ✘ ✔

Drive Selection

✘ ✘ ✔

Binning Function

✘ ✘ ✔

GPIB Interface

✘

✔

✔

* The GOM-804G is simply the GOM-804 with the factory-installed
GPIB option. Please note that the GPIB option cannot be
user-installed on the GOM-804. The option must be ordered prior to
purchase.

Model Lineup

Find Quality Products Online at: [e-mail]

14

www.GlobalTestSupply.com

GETTING STARTED

SOURCE SENSE

POWER

SENSE SOURCE

Rx

DC Milliohm Meter

GOM-805

Ohm Compare Binning

TEMP

TCONVTC

Speed

REL RT

Trigger

DryScan

Display

Diode

Drive

ESC

GND

GUARD

Enter

Local

Range

ESC key

GND
terminal

Function keyLCD display

Power key

Arrow keys,
Enter keys

GUARD
terminal

Sense+, Source+Sense-, Source-

Power Switch

POWER

GND

GUARD

Range

Turns On or Off the main
power. For details about the power up
sequence, see page 24.

Measurement Terminals

Source, Sense
Terminals

Rx

SOURCE SENSE SENSE

SOURCE

Sense + and Sense - terminals.

Current source terminals: Source + and
Source -.

CAUTION

When measuring components
with polarity, connect Source+
to the positive potential and
connect Source- to the negative
potential of the component.

WARNING

Discharge any DUT before
measurement to avoid
damaging the GOM-804/805.

Front Panel Overview

Find Quality Products Online at: [e-mail]

15

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

GND Terminal

GND

Connect the GND (ground) terminal to
the earth ground.

GUARD Terminal

GUARD

The GUARD terminal has the same
potential as earth, but cannot be
substituted for it. Connect the GUARD
terminal to the cable shield layer of the
test leads to help reduce noise.

Function Keys

Ohm

The Ohm key activates the resistance
measurement function.

Compare

The Compare key activates the
comparator function.

Binning

The Binning key activates the binning
function to grade the DUTs into eight
bins according to the tolerance settings.
GOM-805 only.

TC

The TC key activates the TC
(temperature compensation) function
which calculates the resistance of a
DUT at a specified temperature given
the resistance of the DUT at the
ambient temperature and the
temperature coefficient of the DUT is
known.

TCONV

The TCONV (Temperature
Conversion) function calculates the
temperature of a DUT given an initial
temperature, initial resistance, measured
resistance and a constant (inferred zero
resistance temperature) for the DUT.

TEMP

The TEMP key activates the
temperature measurement function.

Find Quality Products Online at: [e-mail]

16

www.GlobalTestSupply.com

GETTING STARTED

Speed

The Speed key toggles between 10
samples per second and 60 samples per
second (Slow rate and Fast rate).

REL

The REL key is used to perform a zero
adjustment to the test leads or a DUT.

RT

The RT key is used to display the
real-time (not averaged) measured
resistance value.

Scan

The Scan key is used to turn on the
Scan function.

Dry

The Dry key is used to turn on the dry
circuit measurement mode which allows
the GOM-805 to measure the contact
resistance of switches and connectors
according to DIN IEC 512 and ASTM
B539 standards. GOM-805 only.

Trigger

When in the internal trigger mode,
pressing the Trigger key will turn on the
external trigger mode. When in the
external trigger mode, pressing the
Trigger key will perform a manual
trigger.

A long press of the Trigger key when in
external trigger mode will reset the
trigger mode back to the internal trigger
mode.

Display

The Display key toggles between the
standard display mode and the
simplified display mode (sans menus
and display icons).

Local

The LOCAL key will switch the
milliohm meter between local and
remote mode.

Diode

The Diode key is used to turn on the
Diode measurement function.

Find Quality Products Online at: [e-mail]

17

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

Drive

+

Enter

The Drive key in conjunction with the
up/down arrow keys is used to select
the measuring signal: DC+, DC-, Pulse,
PWM, Zero. In particular, the Zero
setting can be used as a +/-10mV DC
voltmeter to measure the EMF of
passive components. See page 33 for
details. GOM-805 only. The drive signal
is fixed to DC+ on the GOM-804.

Range

Long pressing the Range key will
activate the auto ranging mode.

Range

+

Enter

The Range key in conjunction with the
up/down arrow keys is used to select
the resistance measurement range.

When in auto ranging mode, pressing
the Range key will activate the manual
ranging mode.

ESC

The ESC key cancels the current setting
and returns the cursor to its default
location or returns to the previous
menu, depending on the circumstances.

Arrow Keys,
Enter Key

Enter

The arrow keys and Enter key are
used to edit parameters, to navigate
the menu system and to select
parameter ranges.

Find Quality Products Online at: [e-mail]

18

www.GlobalTestSupply.com

GETTING STARTED

Drive signal

RangeFunction mode

Function
mode
settings

Trigger mode

Main
measurement
display

Secondary menus

REL value

Memory
number

Function control
indicators

Average value Dry circuit

Rate

Remote mode

Remote error

Function Control
Indicators

The function control indicators show all the currently
active settings for the selected function mode:

Func

Currently selected function mode

Range

The measurement range. Auto
indicates that auto ranging is
active

Trigger mode

Int/Ext

Rate

Slow/Fast

Drive:

DC+, DC-, Pulse, PWM, Zero

Rel

Shows the relative (nominal)
reference value

Avg

Number of samples used for the
Average function.

Dry

Indicates that the dry circuit
function is active

Err

Indicates a remote command
error

TFT-LCD Overview

Find Quality Products Online at: [e-mail]

19

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

RMT

Indicates that the unit is in
remote control mode

Mem No.

Indicates which memory setting
has been recalled

Main
Measurement
Display

Shows all measurement results for the selected function
mode.

Function Mode
Settings

Shows any function mode-specific settings.

Secondary
Menus

The secondary menus show global menus (Meas. Setup),
System, Memory) as well as function-specific secondary
menus.

Meas. Setup

Goes to the global Measurement Setup
menu.

System

Goes to the global System menu

Memory

Allows you to save, recall and clear
memory settings.

View

Shows the all results for all the channels
when a scan has finished.

Clear

Clears the measurement results in the
Binning function when the display
mode is set to Count.

Find Quality Products Online at: [e-mail]

20

www.GlobalTestSupply.com

GETTING STARTED

REMOVE INPUTS BEFORE OPENING.

TO AVOID SHOCK,

WARNING

RS232

SER.NO. LABEL

100 240V , 50 60Hz

25VA MAX

AC

HANDLER / SCAN / EXT I/O

TC SENSOR

GPIB

RS232 portGPIB port Handler/Scan/Ext I/O

USB B
port

Temperature sensor portAC power input

AC Input

100 240V , 50 60Hz

25VA MAX

AC

Accepts the power cord. AC 100 ­240Vac; 50 - 60Hz.

For the power up sequence, see page

24.

RS-232 Port

RS232

Accepts an RS-232C cable for remote
control; DB-9 male connector.

For remote control details, see page 92.

GPIB Port

GPIB

Accepts a GPIB cable for remote
control. See page 93 for details.

USB Device Port

USB device port for remote control.
See page 90 for details.

Handler / Scan /

EXT I/O Port

HANDLER / SCAN / EXT I/O

The Handler / Scan / EXT I/O
port is used to output
pass/fail/high/low comparison
results. This port is also used for
the user-programmable EXT I/O
pins.

Rear Panel Overview

Find Quality Products Online at: [e-mail]

21

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

Temperature
Sensor Port

TC SENSOR

The temperature sensor input is for the
optional PT-100 temperature probe.

Find Quality Products Online at: [e-mail]

22

www.GlobalTestSupply.com

Set Up

Tilt

To tilt, pull the legs forward, as shown below.

Stand Upright

To stand the unit upright, push the legs back under the
casing as shown below.

Tilt Stand

GETTING STARTED

Find Quality Products Online at: [e-mail]

23

www.GlobalTestSupply.com

Power Up

1. Connection

Ensure that the input AC power voltage is within the
range of 100~240 V.

Connect the power cord to the AC Voltage input.

CAUTION

Ensure the ground connector of the power cord is
connected to a safety ground. This will affect the
measurement accuracy.

1. Power up

Press the main power switch on the front panel.

The display will light up and show the last setting used
before the last shut down.

Example:
Resistance
measurement
mode

GOM-804 & GOM-805 User Manual

Find Quality Products Online at: [e-mail]

24

www.GlobalTestSupply.com

GETTING STARTED

Background

The GOM-804/805 uses 4 wire Kelvin connections for
accurate measurements.

Connection
Diagram

GUARD

SOURCE SENSE SENSE

SOURCE

shielding

+

-

Description

Source +

The Source + terminal carries the
measuring current source. It is
connected to the + side of the DUT.

Source -

The Source - terminal accepts the signal
return current and connects to the –
side of the DUT.

Sense +

Monitors the positive (+) potential.

Sense -

Monitors the negative (-) potential.

Guard

Grounds the shielding layer of the test
lead cables to reduce noise.

GND

Provides a reference ground for the
GOM-804/805.

4 Wire Kelvin Connection

Find Quality Products Online at: [e-mail]

25

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

Background

The Relative function is used to perform a zero
adjustment on the test leads.

After the Relative value is pre-set, each measurement that
is displayed is equal to the actual value minus the relative
preset value.

1. Short the
cables

Short the test cables together as shown in the diagram
below:

SOURCE SENSE SENSE

SOURCE

Source+
/Sense+

Source­/Sense-

2. Set the
Reference value

Press the

REL

key.

3. Relative mode
display appears

Before REL

After REL

Rel:

Indicates the Relative function is active

Zeroing (Relative Function)

Find Quality Products Online at: [e-mail]

26

www.GlobalTestSupply.com

MEASUREMENT

Ohm

TC

Speed

Compare Binning

TCONV TEMP

REL RT

Scan Dry

Display Local Diode Range

ESC

Enter

Trigger

Drive

Resistance

Resistance Measurement ....................................... 29

Select the Resistance Range ................................... 30

Drive Signal

Measuring Signal (Drive) Overview ........................ 31

Select Measuring Signal (Drive) ............................. 33

Rate

Select Measurement Rate ....................................... 34

Display Mode

Display Mode ......................................................... 35

Real-Time

View Real-Time Measurement ................................ 36

Dry-Circuit

Dry-Circuit Measurement ....................................... 37

Trigger

Using the Trigger Function ..................................... 38

Diode

Diode Function ....................................................... 40

Compare
Function

Compare Function .................................................. 41

Binning
Function

Binning Function .................................................... 46

MEASUREMENT

Find Quality Products Online at: [e-mail]

27

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

Temperature
Measurement

Temperature Measurement .................................... 50

Temperature
Compensation

Temperature Compensation ................................... 52

Temperature
Conversion

Temperature Conversion ........................................ 56

Measurement
Settings

Average Function ................................................... 60

Measure Delay ....................................................... 61

Trigger Delay .......................................................... 63

Trigger Edge ........................................................... 64

Temperature Unit ................................................... 65

Ambient Temperature ............................................ 66

Line Frequency ....................................................... 67

PWM Setting .......................................................... 68

System Settings

System Information ............................................... 69

Power On Status Setup .......................................... 70

Interface................................................................. 71

Brightness .............................................................. 72

User Define Pins .................................................... 73

Handler Mode ........................................................ 74

Beep ....................................................................... 76

Find Quality Products Online at: [e-mail]

28

www.GlobalTestSupply.com

MEASUREMENT

1. Se lect the
Resistance
function.

Press

Ohm

to access the Resistance measurement

mode.

2. Resistance
mode display
appears.

Ohm measurement

function indicator

Ohm measurement

Resistance range

and mode

3. Connect the
test lead and
measure

4-wire resistance:

Use the SOURCE + and the SOURCE - terminal for
measurement, and the SENSE +, and SENSE - terminal
for sensing.

GUARD

SOURCE SENSE SENSE

SOURCE

shielding

Note

When switching between measurement ranges, please
allow a moment for the circuits to settle before
measuring.

Resistance Measurement

Find Quality Products Online at: [e-mail]

29

www.GlobalTestSupply.com

GOM-804 & GOM-805 User Manual

Background

The resistance range can be used with normal resistance
measurement as well as the temperature compensation
function.

Manual

Press the

Range

key and use the up and down arrow

keys to manually select the resistance range.

Ohm range

Ohm measurement

Range select

indicator

Set range

Auto Range

Long press the

Range

key to turn on automatic

ranging.

Range, Auto range

Selection List

Range

Resolution

50mΩ

1uΩ

500mΩ

10uΩ

5Ω

100uΩ

50Ω

1mΩ

500Ω

10mΩ

5kΩ

100mΩ

50kΩ

1Ω

500kΩ

10Ω

5MΩ

100Ω

Note

For detailed specifications, please see the specifications
on page 152.

Select the Resistance Range

Find Quality Products Online at: [e-mail]

30

www.GlobalTestSupply.com

MEASUREMENT

Background

Resistance measurement has 5 different measuring signals
that can be applied to obtain a resistance measurement:
DC+, DC-, Pulse, PWM, Zero.
These 5 signals are described in below.

Note

The drive function is only applicable to the GOM-805.
The drive signal for the GOM-804 is fixed to DC+.

DC+

~ +6.5V

Open circuit

voltage

0V

V

t

Default drive
signal.

DC-

~ -6.5V

Open circuit

voltage

0V

V

t

Negative drive
signal.

Pulse

~-6.5V

0V

V

t

~+6.5V

50ms

50ms

This mode can be used to
eliminate the thermoelectric
EMF formed on the contact
between a test lead and a
DUT.

PWM

0V

V

t

~+6.5V

ON duty

This mode can be used to
avoid heating up the DUT
and thus avoid having the
measurement accuracy
compromised on
temperature-sensitive DUTs.

Zero

0V

V

t

In this mode, GOM-805
outputs no measuring signal
on the Source loop; therefore,
the Sense loop can be used as
a voltage meter which can
measure up to +/-10mV for
thermoelectric EMF
measurement. This function
is useful for measuring the
Vemf of thermocouple wires.

Measuring Signal (Drive) Overview

Find Quality Products Online at: [e-mail]

31

www.GlobalTestSupply.com