twintex VC9901 Operation Manuals

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3 / DIGITAL MULTIMETER OPERATION MANUAL
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1.SPECIFICATIONS

1.1 GENERAL SPECIFICATIONS

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Display : 3 / digit LCD with a max reading of 1999.
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Polarity : Automatic negative polarity indication.
Zero adjustment : Automatic.
Over range indication : Only the MSD "1" displays.
Low battery : The " " displays.
Safety standards : EMC/LVD. The meter is up to the standards of
IEC1010 Pollution Degree 2, Over voltage categoryⅡor double insulationⅡ.
Operating environment : Temperature 32 to 104℉ (0℃ to 40℃), humidity<85%RH.
Storage environment : Temperature -4 to 140℉(-20℃ to 60℃), humidity<95%RH.
Power : Single, standard 9 volt battery. NEDA 1604IEC6F22
Dimension : 140(H)X65(W)X40(D)mm
Weight : Approx. 170g(including 9V battery)

1.2 ELECTRICAL SPECIFICATIONS

Accuracy is ±(percentage of reading + number of digit) at 23±5℃,<75%RH.
DC Voltage
Range Accuracy
200mV
2V
±(0.5%+3d)
20V
200V
±(0.8%+5d)
1000V
Impedance： 10MΩ
AC Voltage
Range Accuracy
20V
±(0.8%+5d)
200V
±(1.2%+5d)
700V
Impedance : 10MΩ
Frequency response : 20V/200V range: 40-400Hz
700V range : 40-200Hz
Resistance
Range Accuracy
±(0.8%+5d)
200Ω
2kΩ
20kΩ
±(0.8%+3d)
200kΩ
2MΩ
±(1.2%+8d)
20MΩ
Over Load protection ：250V DC/AC RMS
DC Current
Range Accuracy
±(1.2%+3d)
20mA
±(1.5%+3d)
200mA
±(2.0%+5d)
10A
Over Load protection：Fast 0.2A/250V fuse, 10A/250 fuse.
AC Current
Range
20mA
200mA
10A
Over Load protection：Fast 0.2A/250V fuse, 10A/250 fuse
Capacitance
Range
20nF
200nF
20uF
Over Load protection ：36V DC/AC RMS
Diode Test
Range Description
Read & display approx. forward
voltage of diode
Buzzer sounds if resistance
Between terminals V/Ωand
COM is less than about 90Ω.
Resolution
Over load Protection: 250V DC/AC RMS
100uV
Temperature
1mV
Range
10mV
-40℃ ~ 400℃
100mV
400℃ ~ 1000℃
1V
Using F type thermocouple probe

2. FRONT PANEL DESCRIPTION

1. LCD display
Resolution
2. DATA HOLD switch
10mV
3. FUNCTION and RANGE switch
100mV
4. INPUT terminal
1V
Resolution
0.1Ω
1Ω
10Ω
100Ω
1kΩ
10kΩ
3.OPERATION
1.Check the 9-volt battery by setting the ON-OFF switch to ON. If the battery is weak,
a sign will appear on the display. If this does not appear on the display, proceed as
Resolution
below. See MAINTENANCE if the battery has to be replaced.
10uA
2.The mark, or sign next to the lead jacks, is for warning that the input voltage or
100uA
current should not exceed the indicated values.
10mA
This is to prevent from damaging to the internal circuits.
3.The function switch should be set to the range that you want to test before operation.

3.1 DC and AC Voltage measurement

Accuracy Resolution
±(1.2%+5d)
10uA
±(1.5%+5d)
100uA
±(2.0%+8d)
10mA
Accuracy Resolution
10pF
±(4%+10d)
100pF
10nF
Test Condition
Forward DC Current approx.
1mA. Reversed DC voltage
approx. 3V.
Open voltage is approx. 3V
Accuracy Resolution
± ( 0.75% + 3d)
1℃
± ( 1.5% + 15d)
1℃
1. Connect the BLACK test lead to "COM" jack and RED test lead the "V/Ω" jack.
2. Set the FUNCTION switch to desired DCV or ACV position and connect the probes
across the source or load under measurement.
Note:
1) If the voltage ranges is unknown beforehand set the FUNCTION switch to a high
range and work down.
2) When only the figure "1"is displayed, over range is being indicated and the
FUNCTIN switch must be set to a higher range.
3) : Do not apply more than DCV1000V/AC700Vrms to the input. Indication is
possible at higher voltages but there is danger of damaging the internal circuitry.
4) Be careful when measuring high voltage.

3.2 DC and AC Current measurement

1. Connect the BLACK test lead to "COM" jack and RED test lead to "mA" jack for
measurement up to 200mA.
2. Set the FUNCTION switch to desired current range position.
3. Connect the probes in series with the current source to be measured.
4. For current measurement from 200mA to 10A follow generally the above procedure but
connect the RED test lead to "10A" jack.
Note:
1) If the current range is unknown beforehand, set the FUNCTION switch to a high
range and work down.
2) When only the figure "1" is displayed over range is being indicated and the
FUNCTION switch must be set to a higher range.
3) : The max input current is 200mA,or 10A depending upon the jack used.
Excessive current will blow the fuse so that must be replaced.
The 10A range is not protected by a fuse.
4) The max terminal voltage drop (burden voltage) is 200mV.

3.3 Resistance measurement

1. Connect the BLACK test lead to "COM" jack and RED test lead the "V/Ω" jack.
2. Set the FUNCTION Switch to desired resistance range position.
3. Connect the probes across circuit to be tested.
Note:
1) If the resistance value being measured exceeds the max value of the range selected,
and over range indication will be displayed ("1"). Select a higher range, for resistance
of approx. 1MΩand above, the meter may take a few seconds to stabilize. This is
normal for high resistance readings.
2) When the input is not connected, i.e. at open circuit, the figure "1" will be displayed
for the over range condition.
3) When checking in-circuit resistance, be sure the circuit under test has all power
removed and that all capacitor are fully discharged.
4) Open circuit voltage is approx. 3V.
Max input overload: 250Vrms<10sec.

3.4 Capacitance measurement

1. Before connection the test capacitor, note the display which may have readings other than
zero each time the range is changed. This offset reading will not affect the accuracy for it
can be overridden by true value.
2. Connect the test capacitor to the input sockets, noting the polarity connections when
required.
Note:
1) If the capacitance value being measured exceeds the max value of the range selected,
and over range indication will be displayed ("1"). Select a higher range.
2) Before insert the capacitor into Cx socket, the LCD display may not be zero, the