GW Instek GDM-397 User manual

Handheld Digital Multimeter
GDM-397, GDM-461
USER MANUAL
GW INSTEK PART NO. 82DM-46100M01
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.
The information in this manual was correct at the time of printing. However, we
continue to improve our products and therefore reserve the right to change the
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
1
Table of Contents
OVERVIEW............................................................................................................................. 3
Unpacking Inspection.......................................................................................................................4
Safety Information.............................................................................................................................5
Rules For Safe Operation..................................................................................................................6
International Electrical Symbols .......................................................................................................8
The Meter Structure..........................................................................................................................9
Rotary Switch...................................................................................................................................10
Functional Buttons..........................................................................................................................11
Display Symbols..............................................................................................................................12
MEASUREMENT OPERATION........................................................................................... 14
A. DC/AC Voltage Measurement....................................................................................................14
B. DC/AC Current Measurement....................................................................................................17
C. Resistance Measurement ...........................................................................................................20
D. Testing for Continuity.................................................................................................................23
E. Testing Diodes ............................................................................................................................25
F. Capacitance Measurement .........................................................................................................28
G. Frequency Measurement ...........................................................................................................31
H. Temperature Measurement (GDM-397 only) ...........................................................................33
Hold Mode ......................................................................................................................................35
RANGE button ................................................................................................................................36
MAX MIN button (GDM-397 only).................................................................................................36
Peak Hold (GDM-461 only) ............................................................................................................36

GDM-397/GDM-461 User Manual
2
Outputting Data..............................................................................................................................37
The Use of Relative Value Mode.....................................................................................................38
The BLUE button.............................................................................................................................39
Turning on the Display Backlight (GDM-397 only)........................................................................39
Sleep Mode (GDM-397 only)..........................................................................................................39
GENERAL SPECIFICATIONS .............................................................................................. 40
Accuracy Specifications...................................................................................................................42
DC Voltage ......................................................................................................................................42
AC Voltage.......................................................................................................................................44
DC Current ......................................................................................................................................46
AC Current.......................................................................................................................................48
Resistance .......................................................................................................................................50
Capacitance.....................................................................................................................................52
Frequency ........................................................................................................................................54
Diode Test .......................................................................................................................................55
Continuity Test................................................................................................................................55
Temperature Measurement (GDM-397 only) ................................................................................56
MAINTENANCE .................................................................................................................. 57
General Service ...............................................................................................................................57
Replacing the Battery ......................................................................................................................58
Replacing the Fuses ........................................................................................................................60
USB and RS232C Serial Port...........................................................................................................62

GDM-397/GDM-461 User Manual
3
OVERVIEW
This User Manual covers information on safety and cautions. Please read the
relevant information carefully and observe all the Warnings and Notes.
Warning
To avoid electric shock or personal injury, read the “Safety Information” and
“Rules for Safe Operation” carefully before using the Meter.
Digital Multimeter Model GDM-397 and GDM-461 (True RMS) (hereafter referred
to as “the Meter”) are auto ranging multimeters.
The Meter can measure AC/DC Voltage and Current, Resistance, Diode,
Continuity Buzzer, Capacitance, Frequency and Temperature (˚C or ˚F). In addition
to the conventional measuring functions, there is an RS232C or USB serial port
(optional), data hold, relative mode, peak measurement (GDM-461), low battery
display, display backlight (GDM-397) and sleep mode. Except where noted, the
descriptions and instructions in this User Manual apply to both GDM-397 and
GDM-461.

OVERVIEW
4
Unpacking Inspection
Open the package case and take out the Meter. Check the following items carefully
to see if there are any missing or damaged parts:
Item
Description
Qty
1
User Manual
1 piece
2
Test Lead
1 pair
3
K-type Temperature Probe (thermocouple) (GDM-397 only)
1 piece
4
Multi-Purpose Socket
1 piece
5
9V Battery (NEDA1604, 6F22 or 006P)(built-in)
1 piece
6
RS232C Interface Cable
1 piece
7
USB Interface Cable (Optional at extra cost)
1 piece
8
Installation Guide & Computer Interface Software (CD-ROM)
(Comes with the RS232C or USB Interface Cable)
1 piece
In the event you find anything missing or damaged, please contact your dealer
immediately.

GDM-397/GDM-461 User Manual
5
Safety Information
This Meter complies with the IEC61010 standards: in pollution degree 2,
overvoltage category (CAT. III 1000V, CAT. IV 600V) and double insulation.
CAT III: Distribution level, fixed installation, with smaller transient overvoltages
than CAT. IV.
CAT IV: Primary supply level, overhead lines, cable systems etc.
Use the Meter only as specified in this User Manual, otherwise the protection
provided by the Meter may be impaired.
In this manual, a Warning identifies conditions and actions that pose as hazards to
the user, or may damage the Meter or the equipment under test.
A Note identifies the information that a user should pay attention to.
International electrical symbols used on the Meter and in this User Manual are
explained on page 8.

OVERVIEW
6
Rules For Safe Operation
Warning
To avoid possible electric shock or personal injury, and to avoid possible
damage to the Meter or to the equipment under test, adhere to the following
rules:
Before using the Meter inspect the case. Do not use the Meter if it is damaged or
if the case (or part of the case) is removed. Look for cracks or missing plastic.
Pay attention to the insulation around the connectors.
Inspect the test leads for damaged insulation or exposed metal. Check the test
leads for continuity. Replace damaged test leads with those of the same type
before using the Meter again.
Do not apply more than the rated voltage, as marked on the Meter, between the
terminals or between any terminal and ground.
To prevent damage of the Meter, the rotary switch should be placed in the right
position and the measurement range should not be changed during
measurement.
When measuring voltages over 60V in DC or 30V rms in AC, special care should
be taken to avoid electric shock.

GDM-397/GDM-461 User Manual
7
Use the proper terminals, function, and range for your measurements.
Do not use or store the Meter in an environment with high temperature,
humidity, explosives, inflammable materials or strong magnetic fields. The
performance of the Meter may deteriorate when dampened.
When using the test leads, keep your fingers behind the finger guards.
Disconnect circuit power and discharge all high-voltage capacitors before testing
resistance, continuity and diodes.
Before measuring current, check the Meter’s fuses and turn off the current that is
to be tested before connecting the Meter to the circuit. After connecting the
circuit reliably, turn the current that is to be tested on.
Replace the battery as soon as the battery indicator appears. With a low
battery, the Meter might produce false readings that can lead to electric shock
and personal injury.
When servicing the Meter, use only the same model number or identical
electrical specifications for replacement parts.
The internal circuit of the Meter shall not be altered to avoid damaging the
Meter and to prevent accidents.

OVERVIEW
8
A soft cloth and mild detergent should be used to clean the surface of the Meter
when servicing. No abrasives and solvents should be used to prevent the surface
of the Meter from corrosion or damage.
The Meter is suitable for indoor use.
Turn the Meter off when it is not in use and take out the battery when not using
it for a long time.
Constantly check the battery as it may leak when it has not been used for some
time, replace the battery as soon as leaking is detected. A leaking battery will
damage the Meter.
International Electrical Symbols
AC or DC
Ground
Double Insulated
Battery has insufficient charge
Warning. Refer to the User Manual
Conforms to Standards of European
Union

GDM-397/GDM-461 User Manual
9
The Meter Structure
(see figure 1)
1. LCD display
1
2
34
5
6
2. Functional buttons
3. Yellow button
4. Blue button
5. Rotary switch
6. Input terminals:
figure 1

OVERVIEW
10
Rotary Switch
The table below describes the relevant functions of each of the rotary switch
positions.
Rotary Switch Position
Function
V
mV
AC and DC Voltage Measurement
Ω
Resistance Measurement
Diode Test
Continuity Test
Capacitance Test
Hz %
Frequency and Duty Cycle Test
˚C
Temperature in Celsius (GDM-397 only)
˚F
Temperature in Fahrenheit (GDM-397 only)
A
DCA and ACA Measurement
mA
DCmA and ACmA Measurement
10A
10A DC and AC Measurement
OFF
Power off

GDM-397/GDM-461 User Manual
11
Functional Buttons
The table below describes what operations are performed for each of the buttons.
Button
Operation Performed
LIGHT (GDM-397)
Press and hold for 2 seconds to turn the display backlight on or off.
Hold
Press to enter or exit data hold mode.
BLUE Button
Press to select the alternate function.
Yellow (GDM-461)
Hz% (GDM-397)
Press the Hz% button (GDM-397) or the Yellow button(GDM-461) for
frequency and duty cycle measurement.
RANGE
Press RANGE to enter the manual ranging mode; the Meter beeps.
Press RANGE to step through the ranges available for the selected
function; the Meter beeps.
Press and hold RANGE for 2 seconds to return to auto range
mode; the Meter beeps
MAX/MIN(GDM-397)
Press to select the maximum and minimum value.
REL
Press to enter REL mode.
Press again to exit REL mode
For Model GDM-397: Press and hold for over 2 seconds to enter or
exit RS232C or USB mode (optional).
PEAK (GDM-461)
Press to step the display through Pmax and Pmin readings.
Press and hold for 2 seconds to exit Peak mode.
“CAL”means the meter has entered self-calibration mode.

OVERVIEW
12
Display Symbols
No
Symbol
Meaning
1
Data hold is active.
2
Sleep Mode indicator
3
Indicates negative reading.
4
AC
Indicator for AC measurement
5
DC
Indicator for DC measurement
6
The Meter is in the auto range mode in which the Meter
automatically selects the range with the best resolution.
7
MANU
Indicator for manual ranging mode.
8
OL
The input value is too large for the selected range.
10
Diode Test
11
The continuity buzzer is on.
12
MAX/MIN
Maximum and Minimum reading.
13
Data output is in progress
14
The battery is low.
Warning: To avoid false readings, which could lead to
possible electric shock or personal injury, replace the battery
as soon as the battery indicator appears.
15
The REL function is on. The Meter displays the stored value
minus the measured value.

GDM-397/GDM-461 User Manual
13
16
Ω,kΩ, MΩ
Ω:Ohm. The unit of resistance.
kΩ:Kilohm. 1 x 103or 1000 ohms.
MΩ:Megaohm. 1 x 106or 1,000,000 ohms.
V, mV
V: Volts. The unit of voltage.
mV: Millivolt. 1 x 10-3 or 0.001 volts.
A, mA, µA
A: Amperes (amps). The unit of current.
mA: Milliamp. 1 x 10-3 or 0.001 amperes
µA: Microamp. 1x 10-6 or 0.000001 amperes
nF, µF, mF, F
F: Farad. The unit of capacitance.
mF: Milli-farad. 1 x 10-3 or 0.001 farads
µF: Microfarad. 1 x 10-6 or 0.000001 farads.
nF: Nanofarad. 1 x 10-9 or 0.000000001 farads
˚C, ˚F
˚C: Centigrade. The unit of temperature.
˚F: Fahrenheit. The unit of temperature.
Hz, kHz, MHz
Hz: Hertz. The unit of frequency in cycles/second.
kHz: Kilohertz. 1 x 103or 1,000 hertz.
MHz: Megahertz. 1 x 106or1,000,000 hertz.

MEASUREMENT OPERATION
14
MEASUREMENT OPERATION
A. DC/AC Voltage Measurement
(see figure 2)
V
GDM-397
AV
GDM-461
figure 2

GDM-397/GDM-461 User Manual
15
Warning
To avoid injury to your person or damage to the Meter from electric shock,
please do not attempt to measure voltages higher than 1000V, although readings
may be obtained.
When measuring high voltage, take extra care to avoid electric shock.
1. Insert the red test lead into the Vterminal and the black test lead into the COM
terminal.
2. Set the rotary switch to V; DC measurement is the default or press the BLUE
button to switch between DC and AC measurement mode.
Connect the test leads across to the DUT. The measured value is shown on the
display.
GDM-397: Displays the effective value of a sine wave (mean value response).
GDM-461:Displays the true rms value.
3. Press Hz% (GDM-397) or the yellow button (GDM-461) to obtain the
frequency and duty cycle value.
Input Amplitude: (DC offset is zero)
Input Amplitude: ≥range×30%
Frequency response: GDM-397: ≤400Hz, GDM-461: ≤1kHz

MEASUREMENT OPERATION
16
Note
In each range, the Meter has an input impedance of 10MΩexcept for the mV
range which has an input impedance of 3000MΩ. This loading effect can cause
measurement errors in high impedance circuits. If the circuit impedance is less
than or equal to 10kΩ, the error is negligible (0.1% or less).
For GDM-397: When measuring mV, you must press RANGE manually to enter
mV range.
When voltage measurement has been completed, disconnect the testing leads
from the DUT and remove the testing leads from the input terminals of the
Meter.

GDM-397/GDM-461 User Manual
17
B. DC/AC Current Measurement
(see figure 3)
A
GDM-397
A
GDM-461
figure 3

MEASUREMENT OPERATION
18
Warning
Before connecting the Meter to the return circuit to be tested, cut off the current
of the return circuit.
If the fuse burns out during measurement, the Meter may be damaged or the
operator may be hurt.
Use the proper terminals, function, and range for each measurement.
When the testing leads are connected to the current terminals, do not connect
them in parallel to any circuit.
To measure current, do the following:
1. Insert the red test lead into the μmAor Ainput terminal and the black test lead
into the COM terminal.
2. Set the rotary switch to μA, mA, or A.
3. The Meter defaults to DC current measurement mode. To toggle between the
DC and AC current measurement function, press the BLUE button.
4. Connect the test lead in series to the return line of the circuit to be tested. The
measured value is shown on the display.
GDM-397: Displays the effective value of sine wave (mean value response).