GW Instek GDM-8246 User manual

Dual Display Digital
Multimeter
GDM-8246
USER MANUAL
GW INSTEK PART NO. 82DM-82460MH1
ISO-9001 CERTIFIED MANUFACTURER
DUAL DISPLAY DIGITAL MULTIMETER
USER MANUAL
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This manual contains proprietary information, which is protected
by copyrights. 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 City, Taipei County 236, Taiwan.

EC Declaration of Conformity
We
GOOD WILL INSTRUMENT CO., LTD.
(1) No.7-1, Jhongsing Rd., Tucheng City, Taipei County 236, Taiwan
(2) No. 69, Lu San Road, Suzhou City (Xin Qu), Jiangsu Sheng, China
declare, that the below mentioned product
Type of Product: Dual Display Digital Multimeter
Model Number: GDM-8246
are herewith confirmed to comply with the requirements set out in the Council
Directive on the Approximation of the Law of Member States relating to
Electromagnetic Compatibility (2004/108/EC) and Low Voltage Directive
(2006/95/EC).
For the evaluation regarding the Electromagnetic Compatibility and Low
Voltage Directive, the following standards were applied:
◎EMC
Electrical equipment for measurement, control and laboratory use–– EMC
requirements (2004/108/EC)
Harmonized Standard EN 61326-1:2006
EN 61326-2-1:2006
Conducted & Radiated Emission
CISPR11: 2003+A1:2004+A2:2006 Class A Electrical Fast Transients
IEC 61000-4-4: 2004+Corr.1:2006
+Corr.2:2007
Current Harmonics
EN 61000-3-2: 2006 Surge Immunity
IEC 61000-4-5: 2005
Voltage Fluctuations
EN 61000-3-3: 1995+A1: 2001 +A2: 2005 Conducted Susceptibility
IEC 61000-4-6:
2003+A1:2004 +A2 :2006
Electrostatic Discharge
IEC 61000-4-2: 2001 Power Frequency Magnetic Field IEC 61000-4-8: 1993 + A1: 2000
Radiated Immunity
IEC 61000-4-3: 2006 + A1: 2007 Voltage Dips/ Interrupts IEC 61000-4-11: 2004
Safety◎
Low Voltage Equipment Directive 2006/95/EC
Safety Requirements IEC/EN 61010-1: 2001
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TABLE OF CONTENTS PAGE
1. SAFETY SUMMARY……………………………………………… 1
2. INTRODUCTION………………………………………………….. 5
3. SPECIFICATION………………………………………………….. 6
4. OPERATION INSTRUCTION……………………………………. 12
5. MEASUREMENT TUTORIAL…...………………………………. 15
6. MEASUREMENT TECHNIQUES......…………………………… 21
7. MAINTENANCE…………………………………………………... 25

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1. SAFETY SUMMARY
Measuring Circuit
Measuring circuits are subjected to working voltage and transient stresses
from the circuit to which they are connected during measurement or test.
The circuits are divided into the following measurement categories:
Measurement category I is for measurements performed on circuits not
directly connected to MAINS.
Measurement category II is for measurements performed on circuits
directly connected to the low voltage installation.
Measurement category III is for measurements performed in the
building installation.
Measurement category IV is for measurements performed at the source
of the low-voltage installation.
Please refer to the installation category indicated on the font panel to
select adequate measurement category.
The equipment marked with measurement category I shall
not be used for measurements within measurement II, III
and IV.
Safety terms and symbols
Please take a moment to review these safety terms and symbols which
may appear in this manual or on Equipment to prevent damage to the
instrument.
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WARNING. Warning statements identify condition or
practices that could result in injury or loss of life.
CAUTION. Caution statements identify conditions or
practices that could result in damage to this product or
other property.
DANGER High Voltage
ATTENTION refer to Manual
Protective Conductor Terminal
(ground) Earth Terminal
Frame or Chassis Terminal

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FOR UNITED KINGDOM ONLY
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 colours 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 the letter E or
by the earth symbol or coloured Green or Green &
Yellow.
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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, 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 moulded mains connector that requires removal
/replacement must be destroyed by removal of any fuse &
fuse carrier and disposed of immediately, as a plug with
bared wires is hazardous if a engaged in live socket. Any
re-wiring must be carried out in accordance with the
information detailed on this label.

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2. INTRODUCTION
This is a portable, bench-type dual display digital multimeter with a
good-performance 50000 counts designed for general purpose application.
The dual display allows you to display two functions of the input signal
being measured.
Features
z50000 counts DMM
zMulti-function ACV, DCV, ACA, DCA, R, C , Hz, Continuity Beeper,
Diode Test, MAX/MIN, REL, dBm, HOLD, Autohold, Compare.
zDual display Indicate ACV and Hz, DCV (ACV) and dBm or DCV
and ACV ripple.
zManual or Autoranging
z0.02% DCV accuracy
z20Ahigh current range
z1000V high voltage range
zAC True RMS or AC+DC True RMS.
zACV frequency response 100kHz.
zThe reference impedance selectable in the dBm modifier.
zAuto-recall the setting upon power on.
zInterface RS232 (Standard) and GPIB (option).
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3. SPECIFICATIONS
The specifications are operated under the essential conditions as follows:
zA 1-year calibration cycle.
zAn operating temperature of 18 to 28℃(64.4 to 82.4℉).
zRelative humidity not exceeding 75%.
zAccuracy is expressed as ±(percentage of reading + digits).
zThe AC specification is based on the 50% of duty cycle.
zThe power cord protective grounding conductor must be connected to
ground.
1. DC VOLTAGE OR DCV OF RIPPLE FUNCTION
RANGE RESOLUTION ACCURACY INPUT IMPEDANCE
500mV 10μV10MΩ
5V 100μV11.1 MΩ
50V 1mV 10.1MΩ
500V 10mV 10MΩ
1000V 100mV
0.02%+4
10MΩ
DCV Input Impedance Approx. 10MΩin parallel with <100pF, all ranges.
DCV of Ripple Function 5V~500V 3 ranges.
DCV of Ripple Input
Impedance 10MΩ∕∕ 10MΩin parallel with <100pF.
Normal Mode Rejection Ratio >60dB at 60Hz or 50Hz.
Common Mode Rejection Ratio >90dB at 60Hz or 50Hz.
Common Mode Voltage
(Maximum) 500V dc or peak ac.
Maximum Input 450V dc or peak ac continuous on 500mV range an
d
ripple function.
1000V dc or peak ac continuous on other range.
When the input exceeds the full scale of the selected range, the display will appear
“—OL—“ of over-range indication.

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2. TRUE RMS AC, AC+DC VOLTAGE
Accuracy between 2% of range and full range.
RANGE 20Hz-
50Hz 50Hz- 2kHz 2kHz- 10kHz 10kHz- 20kHz 20kHz- 50kHz 50kHz- 100kHz
500mV
5V
50V
2%+20 5%+50
500V
0.5%+50
-------- --------
1000V
1%+10 0.3%+30 0.4%+50
-------- -------- --------
RANGE RESOLUTION INPUT IMPEDANCE
500mV 10μV 10MΩ
5V 100μV 11.1 MΩ
50V 1mV
10.1MΩ
500V 10mV
10MΩ
1000V 100mV 10MΩ
Input Impedance Approx. 10MΩin parallel with < 100pF,all ranges.
Maximum Input 450V dc or peak ac continuous on 500mV range.
1000Vrms on other range.
Crest Factor Range 3.0 at full scale.
AC+DC all ranges ±(percentage of reading + 50 counts).
When the input exceeds the full scale of the selected range, the display will appear
“—OL—“ of over-range indication.
3. ACV OF RIPPLE FUNCTION
RANGE 20Hz-
50Hz 50Hz- 2kHz 2kHz- 10kHz 10kHz- 20kHz 20kHz- 50kHz 50kHz- 100kHz
500mV 1%+10 0.3%+30 0.4%+50 0.5%+50 2%+20 5%+50
Input Impedance 10MΩ∕∕ 10MΩin parallel with < 100pF.
Maximum Input 450V dc or peak ac continuous.
Crest Factor Range 3.0 at full scale.
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When the input exceeds the full scale of the selected range, the display will appea
r
“—OL—“ of over-range indication.
4. FREQUENCY MEASUREMENT AT ACV RANGE
RANGE FREQUENCY INPUT LEVEL (SINE WAVE) ACCURACY
10Hz ~ 50kHz ≧120mV
500mV 50kHz ~ 150kH
z
≧200mV
5V 10Hz ~ 200kHz Auto range≧0.4V
Manaul range≧1.2V
50V 20Hz ~ 200kHz ≧1.2V
500V 20Hz ~ 20kHz ≧12V
0.05%+1
AC+DC measurement does not supportAC+Hz function.
Maximum Input 450V peak ac continuous on 500mV range.
500V peak ac continuous on the other range.
5. DC Current
RANGE RESOLUTION ACCURACY BURDEN VOLTAGE
500μA0.01μA
5mA 0.1μA
50mA 1μA
0.7Vmax.
500mA 10μA
0.05% +3
2A 100μA 0.8Vmax.
20A 1mA 0.2% +5 0.9Vmax.
Protection Fuse protection for 500μA,5mA,50mA,500mA,2A and 20A
ranges, 20A range input for 15 seconds max.
When the input exceeds the full scale of the selected range, the display will appear
“—OL—“ of over-range indication.

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6. TRUE RMS AC OR AC+DC CURRENT
Accuracy Between 2% of range and full range.
RANGE 20Hz-45Hz 45Hz-2kHz 2kHz-10kHz 10kHz-20kHz
500μA
5mA
50mA
500mA
1%+15 2%+15
2A —————————
20A
1%+15 0.5%+15
—————————
Protection Fuse protection 500μA,5mA,50mA,500mA,2A and 20A
ranges, 20A range input for 15 seconds max.
Crest Factor Range 3.0 at full scale.
The burden voltage is the same as the DC current.
When the input exceeds the full scale of the selected range, the display will appear
“—OL—” of over-range indication.
7. FREQUENCY MEASUREMENT AT ACA RANGE
RANGE FREQUENCY INPUT LEVEL (SINE WAVE) ACCURACY
500μA 10Hz ~ 20kHz ≧90μA
5mA 10Hz ~ 20kHz ≧0.9mA
50mA 10Hz ~ 20kHz ≧9mA
500mA 10Hz ~ 20kHz ≧90mA
2A 10Hz ~ 2kHz ≧1A
20A 10Hz ~ 2kHz ≧9A
0.05%+1
AC+DC measurement does not supportAC+Hz function.
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8. RESISTANCE
RANGE RESOLUTION ACCURACY
500Ω0.01Ω0.1%+4
5kΩ0.1Ω
50kΩ1Ω
500kΩ10Ω
0.1%+2
5MΩ100Ω0.2%+2
20MΩ1kΩ0.3%+2
Open-circuit Voltage 3.2 volts maximum on 500Ω, 5kΩ 1.3 volts maximum on all
other ranges.
Protection 450V dc or peak ac continuous.
9. CAPACITANCE
RANGE: RESOLUTION ACCURACY
5n * 0.001n ≧1nF: 2%+10
<1nF & ≧0.5nF: 2%+20
50n 0.01n ≧10nF: 2%+10
<10nF & ≧5nF: 2%+30
500n 0.1n
5μ1n
50μ10n
2%+4
*5n range tends to be interfered by the test lead’s impedance and position. For the
accuracy, please measure the range on the input terminal directly.
Protection 450V dc or peak ac continuous.
10. DIODE CHECK
Description Display read forward voltage of diode.
Open Voltage 3.1V approx.
Maximum Forward
Voltage 1.5V
Protection 450V dc or peak ac continuous.

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11. CONTINUITY BEEPER
Description Built in buzzer sounds when conductance is less than 5 ohm.
Open Voltage 3 volts maximum.
Protection 450V dc or peak ac continuous.
12. ENVIRONMENTAL
Operation
Environment
Indoor use, altitude up to 2000m.
Ambient Temperature 0℃to 50℃.
Relative Humidity 75% (Maximum).
Installation category II
Pollution Degree 2
Storage temperature -10℃to 70℃.
Relative Humidity Up to 75%, 0℃to 35℃, Up to 50%, 35℃to 50℃, except
the ranges of 2MΩand 20MΩwhich are up to75% , 0℃
to 35℃.
13. GENERAL
Maximum Common
Mode Voltage 500V dc or peak ac (low terminal potential with respect to power line ground).
Warm Up 0.5 hours to achieve rated accuracy.
Power source AC 100V/120V/220V/230V±10%, 50/60Hz, 12.5VA, 10.5W.
Accessories TestLead ×1
Instruction manual × 1, Interface manual × 1
Dimension 251(W)×91(H)×291(D) m/m
Weigh Approx. 2.6 kg
WARNING ：To avoid electrical shock, the power cord
protective grounding conductor must be connected to
ground.
CAUTION：To avoid damaging the instrument, do not use it
in a place where ambient temperature exceeds 50℃.
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4. OPERATION INSTRUCTIONS
4-1. Front panel and rear panel
The front panel, shown in Figure 4-1, contains three main elements: the
input terminals, the primary and secondary displays, and the push
buttons. The rear panel, shown in Figure 4-2, contains the AC
power-line connector, and fuse & line voltage selector, input fuse
holder, and interface terminal.
4-2. The [SHIFT] key and function keys
[SHIFT] button is used to enable the secondary function of certain
function keys that with blue symbols printed above. The SHIFT LED
will be on after pressed the [SHIFT] button. At this time, only the
buttons with blue symbols are workable. To release SHIFT function,
press [SHIFT] again. For example, to select DCmV function, press
[SHIFT], then press [DCV] ([DCmV]).
4-3. Set mode
Press [SHIFT] [SET] in sequence into SET mode, then proceed further
setting by pressing the white characters with blue background [HI],
[LO], [REF Ω], [RS232], [GPIB], [ENTER] sequentially.
4-4. Warm up
The instrument requires half-an-hour warm up to achieve rated
accuracy.
4-5. Over-range indication
An input is over-range if it exceeds the full scale of the selected range.
GDM-8246 indicates an input is over-range by lighting the “—OL—”
pattern on display.
4-6. No specification indication
On AC+Hz measured mode, when an input is less sensitivity, the
secondary display show “————”. When the frequency of an input
exceeds 110kHz, the primary display will show “————”.

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4-7. Interface Operation
This instrument equips RS-232 as standard device with a D-SUB 9 PIN
SHELL on the rear panel. Besides, the instrument also provides a GPIB
option device with a 24 PIN SHELL in blue. The configuration is
compliance with IEE488.
For further detailed operation, please refer to the Interface manual.
4-8. Input overload protection
The maximum allowable input is shown as table 4-1. Please proceed
the measurement accordingly.
Table 4-1:
FUNCTION RANGE MAXIMUN INPUT
DCV 5V~1000V 1000Vdc or peak ac
ACV (AC+DC) 5V~1000V 1000V rms continuous &
107V•Hz maximum
DCA,ACA(AC+DC) 500μA~2A fuse protected: T2A 250V 1.5kA
breaking capacity
DC,AC20A(AC+DC) 20A fuse protected: F20A 600V
100kA breaking capacity
DC,ACmV (AC+DC) 500mV 450V dc or ac peak
OHM all ranges 450V dc or ac peak
CAPACITANCE all ranges 450V dc or ac peak
RIPPLE all ranges 450V dc or ac peak
WARNING: To avoid shock hazard and/or instrument
damage, do not apply input potentials that exceed the input
overload limits shown in table 4-1.
4-9. Input connections to common
WARNING: To avoid shock hazard and/or instrument
damage, do not connect the common input terminal to any
source of more than 500 volts DC or peak AC above earth
ground.
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zFigure 4-1 Front Panel
zFigure 4-2 Rear Panel

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5. MEASUREMENT TUTORIAL
5-1. Voltage measurements (DCV, ACV, DCmV,ACmV)
1).Press the button to select desired function.
2).Press [▲]or[▼]to the desired range (if you have no idea about the
value of input, we suggest you always start at the highest range).
Press [AUTO/MAN] button for manual or auto-ranging selection.
3).Connect the test lead to the V and COM input terminals of the
instrument.
4).Connect the test lead to the measuring points and read the displayed
value.
NOTE: After measuring high voltage to 1000V dc, errors may
occur when the 100μV is measured. Allow up to one
minute prior to making low-level measurements
5-2. Current measurements (DCA, DC 20A, ACA,AC 20A)
1).Press the button to select function.
2).Press [▲]or[▼]to the desired range (if you have no idea about the
value of input. we suggest you always start at the highest
range).Press [AUTO/MAN] button to change manual or
auto-ranging.
3).Connect the test lead to the 2A or 20A and COM input terminals of
the instrument.
4).Connect the test lead to the measuring points and read the displayed
value.
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5-3. Resistance, capacitance, continuity beeper measurements
1). Press the button to select function.
2). Press [▲]or[▼]to the desired range. Press [AUTO/MAN] button
to change manual or auto-ranging.
3). Connect the test lead to the Ω, and COM input terminals of
the instrument.
4). Connect the test lead to the measuring points and read the
displayed value.
5-4. Diode test measurements
1). Press the button to select function.
2). Connect the test lead to the and COM input terminals of
the instrument.
3). Connect the test lead to the semiconductor junction (diode or
transistor) as shown in Figure 5-1,and read the displayed value.
zFigure 5-1
Connectto Connectto
“”“COM”
terminal. terminal
5-5. dBm measurements
This function converts a voltage measurement into dBm. The function
can be selected only when a voltage function (volts ac, volts dc, or
volts ac+dc) is selected. Press [dBm] button, the secondary display
shows the dBm value that reposed on the voltage value showed in the
primary display.

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For example, if [dBm] is pressed when measuring voltage in the max
mode, the maximum value is converted to dBm. To release the dBm
function, press [dBm] again. The dBm mode, AC+Hz mode and
Compare are not selected concurrently.
The reference impedance can be set to any of 21 reference
impedances listed in the Table 5-1 according to the steps as follows:
1) Press [SHIFT] [SET] in sequence into SET mode.
2) Press [REF Ω] to reference impedance selection . The value
displayed on the primary display is the current setting value.
3) Select the required impedance by using [▼] and [▲], then press
[ENTER] to save the data, or press [SHIFT] to cancel the setting.
Table 5-1 8000 300 93
1200 250 75
1000 150 50
900 135 16
800 125 8
600 124 4
500 110 2
5-6.AC+Hz measurements
The function can be selected only when ac range is selected. Press
[SHIFT], then press [AC+Hz], the secondary display shows the
frequency of the input signal that is higher than the sensitivity. The
frequency measurement does not depend on the max/min, rel, or hold
mode. In this mode, the reading rate of the DMM may be slower than
the normal state.
To release the AC+Hz function, press [AC+Hz] again. The dBm mode
and AC+Hz mode and Compare are not selected concurrently.
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5-7.AC+DC measurements
The function can be selected only when voltage or current function is
selected. Press [AC+DC] button, the primary display shows the true
rms value of the input signal including the ac component and dc
component. In this mode, the reading rate of the DMM is slower than
the normal state.
To release the AC+DC function, press other function (voltage ac or dc,
current ac or dc, R,C, Continuity Beeper, Diode Test) key.
5-8. MAX/MIN measurements
The MAX/MIN mode causes the DMM to hold the lowest and highest
readings. Press [MAX/MIN] button to the MAX mode. The highest
will be displayed in continuous input. In the MAX mode, press
[MAX/MIN] button to the MIN mode. The lowest will be displayed in
continuous input. In the MIN mode, press [MAX/MIN] button to
release the MAX/MIN mode.
5-9. RELmeasurements
When the [REL] button is pressed, the meter stores the present reading
and displays subsequent measurements as the difference between the
measured value and the stored reading.
In the MAX/MIN mode, set [REL] button to the REL mode. The
maximum or minimum reading will become the relative base.

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5-10. HOLD andAUTO HOLD measurements
The HOLD mode can keep the measured value on the primary
display. Press [HOLD] button, the last reading is held on the display
in all function. To release the HOLD function, just press [HOLD]
again.
The AUTOHOLD mode allows you to keep your eyes fixing on the
probes when taking measurements in difficult or hazardous
circumstances, then read the display when it is convenient and safe.
Press [SHIFT][AUTOHOLD] in sequence into AUTOHOLD mode,
every time when the value is more than the 8% of full scale, and
with 200 counts of different value compared with the previous
AUTOHOLD value, the data on the primary display will be updated.
In the AUTO range mode, when the value is less than 10% full
scale and more than 0.8% full scale, it will change range downward
automatically. If want to release AUTOHOLD function, press
[SHIFT] [AUTOHOLD] in sequence.
5-11. COMPARE MEASUREMENT
In Compare mode, can set the maximum and minimum value to
compare with the current measured value. The secondary display
will show “Hi” when the measured value is more than the
maximum value, will show “Lo” when the measured value is less
than minimum value, and will show “Pass” in other status. The
functions of DCV(DCmV), ACV(ACmV, AC+DC), DCA(DC20A),
ACA(AC20A), OHM, and Capacitance have their own maximum
and minimum value setting separately according to the procedure as
follows:
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1) Select the required function and range, set maximum or
minimum value by pressing [SHIFT][SET] and [HI] or [LO] in
sequence. Now the panel is displaying the current setting value,
if the setting value is more than 50000 counts, the panel will
display 60000.
2) The flickering digits can be adjusted by pressing [▲] to set the
value, and pressing [▼] to move the adjusted position. Also
can adjust the plus and minus sign through [▲] and [▼].
3) When the setting is completed, press [ENTER] to save the
setting, or press [SHIFT] to cancel the setting.
5-12. RIPPLE MEASUREMENT
The RIPPLE mode can monitor DC level and AC ripple of power
supply. In DCV voltage function, set to RIPPLE mode by pressing
[SHIFT][RIPPLE] in sequence, the primary display will show DCV
value with the ranges of 5V, 50V, and 500V, the secondary display
will show AC component of signal with the range of 500mVac,
100kHz frequency response. The function is easy to detect DC and
AC components of signal simultaneously.
If want to leave the RIPPLE mode, just switch to other main
function.

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6. MEASUREMENT TECHNIQUES
6-1. dBm measurement technique
dBm is defined as above or below a 1mW reference. A voltage
measurement is converted to dBm using the following formula:
dBm=10*log 10 (1000*voltage value2/reference impedance.)
The reference impedance can be set.
For example, the reference impedance of 600Ω, 0.7746V will be
convert to 0 dBm.
6-2. True rms measurement
The true rms (root-mean-square) value of a waveform is equivalent to
dc value that causes the same amount of heat to be dissipated in a
resistor.
Since average-responding meters have been in use for so long, you
may have accumulated test or reference data based on them. Figure
6-1 illustrates the relationship between ac and dc components for
common waveforms, and compares readings for true rms meters and
average-responding meters. Figure 6-1 will help you convert between
the two measurement methods.
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zFigure 6-1: Voltage Conversion

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6-3.AC+DC measurement
A signal includes an ac component and a dc level. The relationship
between the total rms value of the signal and the ac component and the
dc component is:
rms total= 22 component)(dcrms)componentc( +a
6-4. Crest factor
Crest factor is often overlooked in determining the accuracy of an ac
measurement. Crest factor is defined as the ratio of the peak signal
amplitude to the rms value of the signal.
If an input signal has a crest factor of 3.0 or less, voltage
measurements will not be in error due to dynamic range limitations at
full-scale.
The waveforms in Figure 6-2 show signals with increasing value of
crest factor. As you can see from the series of waveforms, a signal with
a crest factor above 3.0 is unusual.
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zFigure 6-2: Crest Factor

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7. MAINTENANCE
The following instructions are executed by qualified personnel only.
To avoid electrical shock, do not perform any servicing other than the
operating instructions unless you are qualified to do so.
7-1. Line fuse replacement
If the fuse blows, the DMM would not work. Try to determine and
correct the cause of the blown fuse, then replace the fuse with correct
rating and type shown as below:
FUSE RATING AND TYPE
100/120V T0.16A 250V
220/230V T0.08A 250V
F101 on PCB T0.5A 250V
7-2. Current fuse replacement
The current fuse protects the 500μA~ 2A range from an input
current greater 2A.To replace the current fuse, perform the following
steps:
1). Turn off the power, disconnect the power line and remove the test
leads.
2). Place the end of a flat blade screwdriver into the slot of the fuse
holder on the front panel. Push and carefully rotate the fuse carrier
turn counterclockwise till remove the fuse and the fuse carrier off
the front panel.
3). Remove the defective fuse and replace the correct fuse (T2A 250V,
1.5kA breaking capacity ).
Remark: There is a F20A fuse built inside the case located on F301,
if any damage occurred on this fuse, please return to the
manufacturer for repair.
DUAL DISPLAY DIGITAL MULTIMETER
USER MANUAL
26
7-3. Line voltage conversion
The primary winding of the power transformer is tapped to permit
operation from 100/120V, or 220/230V AC 50/60Hz line voltage.
Conversion from one line voltage to another is done by changing the
line voltage selector switch as shown in Figure 4-2. The rear panel
identifies the line voltage to which the unit was factory set. To convert
to a different line voltage, perform the following procedure:
1). Make sure the power cord is unplugged.
2). Adjust the line voltage selector switch to the desired line voltage
position.
3). A change in line voltage may also require a corresponding change
of fuse value. Install the correct fuse value as listed on rear panel.
7-4. Cleaning
To keep the instrument clean, wipe the case with a damp cloth and
detergent. Do not use abrasives or solvents.