GW Instek GDM-531 User manual

Handheld Digital Multimeter
GDM-531
USER MANUAL
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 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
rights to change specification, 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
GETTING STARTED .......................................................... 7
GDM-531 Overview .................................................8
OPERATION .................................................................. 10
Operating Instructions .......................................... 11
AC/DC Voltage Measurement ................................ 11
Resistance Measurement....................................... 13
Continuity Measurement ....................................... 15
Diode Measurement .............................................. 16
Capacitance Measurement..................................... 17
DC Current Measurement...................................... 19
Battery Measurement ............................................ 21
NCV Measurement ................................................ 23
Others ................................................................... 25
SPECIFICATIONS ........................................................... 26
General Specifications........................................... 26
Technical Specifications ........................................ 27
MAINTENANCE ............................................................. 31
General Meintenance ............................................ 31
Replacements ........................................................ 31

GDM-531 User Manual
4
SAFETY INSTRUCTIONS
This chapter contains important safety
instructions that you must follow during
operation and storage. Read the following before
any operation to ensure your safety and to keep
the instrument in the best possible condition.
Safety Standards
 EN 61326-1; EN 61326-2-2
 EN 61010-1; EN 61010-2-030; EN 61010-2-033
 CAT III 600V, double insulation standard, over voltage standard,
and RoHS, pollution grade II

SAFETY INSTRUCTIONS
5
Electrical Symbols
These safety symbols may appear in this manual or on the
instrument.
Low battery
Direct current
Alternating current
Warning
Double insulation
Caution, possibility of electric shock
Grounding
Comply with European Union Standards
CAT III
It is applicable to test and measuring circuits
connected to the distribution part of the building's
low-voltage MAINS installation.

GDM-531 User Manual
6
Safety Instructions
Do not use the device if the rear cover is not covered up or it will
pose a shock hazard
Do not use the device if the device or test leads appear damaged
or if you suspect that the device is not operating properly. Pay
particular attention to the insulation layers.
During measurement, keep your fingers behind the finger guard.
Do not input over 600V voltage between the device and the
grounding.
Use caution to measure voltage >DC 60V or AC 30Vrms.
Never input voltage and current exceeding the value listed on the
device.
Functional dial should be switched to proper position.
Do not switch the functional dial during measuring.
Do not change the internal circuit of the device in order to avoid
the damage to the device and users.
Replace the fuse with the specified model.
To avoid false reading, replace the battery when the battery
indicator appears.
Do not use or store the device in high temperature, high
humidity, flammable, explosive or strong magnetic field
environments.
Use damp cloth to clean the case; do not use detergent containing
solvents or abradants.
Before each use verify meter operation by measuring a known
voltage or current. If the equipment is used in a manner not
specified by the manufacturer, the protection provided by the
equipment may be impaired.

GETTING STARTED
7
GETTING STARTED
This chapter describes the GDM-531 in a nutshell,
including its main features and front/ rear panel
introduction.
GDM-531 Overview .................................................8
Overview ............................................................................................. 8
Features................................................................................................ 8
Accessories .......................................................................................... 8
External Structure .............................................................................. 9
Function Buttons ............................................................................... 9

GDM-531 User Manual
8
GDM-531 Overview
Overview
GDM-531 is a 6000 count palm sized multimeter with auto and
manual range respectively. These CE certified multimeters are CAT
III 600V, which can withstand 6000kV surge voltage. GDM-531 is
designed with high voltage warning and over range alarm, making
this series great for a wide range of measurement needs.
Features
Smart appearance with comfy handle
Pass 2-meter drop test
Large LCD screen with 6000 counts display, RMS measurement,
fast ADC digital converter (3 times/s)
Overload protection with alert
Extensive range for capacitance measurement, short response
time. E.g. When measuring ≤10mF,response time ≤6s
Support NCV and battery measurement.
Support up to 600V/10A AC/DC current and voltage
measurement.
Backlight installed for dim occasions.
Energy saving
Accessories
Before using the GDM unit, check the package contents to make
sure all the accessories are included.
Standard Accessories
Description
User manual*1 pc
Test leads*1 pair
1.5V AAA Battery*2

GETTING STARTED
9
External Structure
Item Index
Description
1
LCD display
2
Functional buttons
3
Functional dial
4
10A input terminal
5
COM input terminal
6
Other input terminals
Function Buttons
Button
Description
HOLD/SELECT:
Press to turn on/off data hold function (except
at continuity/diode position)
REL
The capacitance mode, press this button to
remove the base.
LIGHT:
Press this button to turn on/off the backlight.

GDM-531 User Manual
10
OPERATION
Operating Instructions .......................................... 11
AC/DC Voltage Measurement ................................ 11
Resistance Measurement.......................................13
Continuity Measurement ....................................... 15
Diode Measurement .............................................. 16
Capacitance Measurement.....................................17
DC Current Measurement...................................... 19
Battery Measurement ............................................ 21
1.5V battery: resistance=30Ω.........................................................22
9V battery: resistance=900Ω..........................................................22
NCV Measurement ................................................ 23
Others ................................................................... 25

OPERATION
11
Operating Instructions
To avoid false reading, replace the battery if the battery low power
symbol
appears. Also pay special attention to the warning sign
besides the test lead housing, indicating that the tested voltage
or current must not exceed the values listed on the device.
AC/DC Voltage Measurement
Wire Connection
Diagram
Steps of
Measurement
1. Switch the dial to ACV or DCV position
2. Insert the red test lead to VΩmA jack, black to
COM jack.
3. Connect test leads with the load in parallel.
4. At mV position, press SELECT to enter
frequency measurement (10Hz~1MHz).
5. Reading is displayed.

GDM-531 User Manual
12
Warnings
Do not input voltage over 600Vrms, or it may
pose shock hazard.
Be cautious when measuring high voltage
Note
Before using the device, if the voltage is
unknown, switch the dial to the maximum
range position and reduce the range according
to the practical reading.
Test a known voltage to verify the device.
When input impedance about 10MΩ, there
may be errors when measurement high
voltage. Input impedance≤10kΩ,
measurement errors can be ignored (≤0.1%)

OPERATION
13
Resistance Measurement
Wire Connection
Diagram
Steps of
Measurement
1. Switch the dial to resistance position.
2. Insert the red test lead to VΩmA jack, black to
COM jack.
3. Connect test leads with the load in parallel.
4. Reading is displayed.

GDM-531 User Manual
14
Note
If the resistor is open or over the range, the
“OL” symbol will be displayed on the screen.
Before measuring resistance, switch off the
power supply of the circuit, and fully
discharge all capacitors.
When measuring low resistance, the test leads
will produce 0.1Ω~0.2Ω measurement error.
To obtain accurate measurement, short the
test leads and use REL function.
If the resistance when shorted is more than
0.5Ω, please check if test leads are loosened or
damaged.
Resistance measurement can be used to
inspect device’s internal fuses.
Do not input over 60V DC or 30V AC or it will
pose shock hazard.

OPERATION
15
Continuity Measurement
Wire Connection
Diagram
Steps of
Measurement
1. Switch the dial to continuity position.
2. Insert the red test lead to VΩmA jack, black to
COM jack.
3. Connect test leads with the load in parallel.
4. Reading is displayed. Measured resistance
>51Ω, circuit is in open status.
Measured resistance ≤10Ω, circuit is in good
conduction status, buzzer will go off.
Warnings
Switch off the power supply to the circuit, and
fully discharge all capacitors

GDM-531 User Manual
16
Diode Measurement
Wire Connection
Diagram
Steps of
Measurement
1. Switch the dial to diode position.
2. Insert the red test lead to VΩmA jack, black to
COM jack.
3. Red test lead to positive pole, black to
negative pole.
4. Reading is displayed.
5. “OL” symbol appears when the diode is open
or polarity is reversed. For silicon PN
junction, normal value: 500 ~ 800mV (0.5 ~
0.8V).
Note
Switch off the power supply to the circuit, and
fully discharge all capacitors Voltage for
testing diode is about 4.0V/1.5mA.

OPERATION
17
Capacitance Measurement
Wire Connection
Diagram
Steps of
Measurement
1. Switch the dial to capacitance measurement.
2. Insert the red test lead to VΩmA jack, black to
COM jack.
3. Reading is displayed.

GDM-531 User Manual
18
Note
Switch off the power supply to the circuit, and
fully discharge all capacitors
Before measuring capacitors (especially for
high voltage capacitors), please fully
discharge them.
If the tested capacitor is shorted or its capacity
is over the specified range "OL" symbol will
be displayed on the screen.
When measuring large capacitors, it may take
a few seconds to obtain steady readings.
When there is no input, the device displays a
fixed value (intrinsic capacitance).
For small capacitance measurement, to ensure
measurement accuracy, the measured value
must be subtracted from intrinsic capacitance.
Or users can measure small capacity
capacitors with relative measurement function
(REL) (the device will automatically subtract
the intrinsic capacitance)

OPERATION
19
DC Current Measurement
Wire Connection
Diagram
Steps of
Measurement
1. Switch the dial to DC current position.
2. According to the current being measured.
Insert the red test lead to VΩmA jack or 10A
jack, black to COM jack.
3. Connect test leads with the circuit in series.
4. Reading is displayed.

GDM-531 User Manual
20
Note
Before measuring, switch off the power
supply of the circuit.
If the range of the measured current is
unknown, select the maximum range and then
accordingly reduce.
There are fuses inside VΩmA jack and 10A
jack. Do not connect the test leads with any
circuits in parallel.
If the tested current is about 10A, each
measurement time is about 10 seconds(less
than 30s) and the next test should be after 15
minutes.