Unit VC820 User manual

VC820/VC840OPERATINGMANUAL
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Table of Contents
Title Page
Overview
Unpacking Inspection
Safety Information
Rules For Safe Operation
Electrical Symbols
Functional Structure
Rotary Switch
Functional Buttons
Display Symbols
Manual Ranging and Autoranging
Measurement Operation
A. DC Voltage Measurement
B. AC Voltage Measurement
C. Measuring Resistance
D. Testing for Continuity
E. Testing Diode
F. Capacitance Measurement
G. Frequency or Duty Cycle Measurement
H. Temperature Measurement
I. DC or AC Current Measurement
Operation of Hold Mode
The Use of Relative Value Mode
POWER Button

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SELECT Button (blue)
General Specification
Accuracy Specification
A. DC Voltage
B. AC Voltage
C. Resistance
D. Continuity Test
E. Diode Test
F. Capacitance
G. Frequency & Duty Cycle
H. Temperature
I. DC Current
J. AC Current
Maintenance
A. General Maintenance & Service
B. Testing the Fuses
C. Replacing the Battery
D. Replacing the Fuses
RS232C Serial Port
A. Connect with computer
B. RS232C Port Cable
C. Setting of RS232C Serial Ports
D. System Requirements for Computer Interface Software

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Overview
This Operating Manual covers information on safety and cautions. Please read the relevant information carefully and
observe all the warnings and notes strictly.
Warning
Read the Rules for Safety Operation carefully before using the Meter
Digital Multimeter Model VC820 and VC840 (hereafter referred to as “the Meter”) has autorange and manual range options
with maximum reading 3999. The enclosure structure design adopted advanced “co-injection” technique in order to provide
sufficient insulation.
In addition to the conventional measuring functions, there is a RS232C standard serial port is equipped with this Meter for
easy connection with computer to realize macro recording and monitoring and capture of transient dynamic data, displaying
change of waveform during the measurement, providing data and evidence to engineering technicians for scientific research.
This is also a highly applied digital multimeter of high performance with full input protection. VC840 also has true rms
reading for AC voltage and AC current measurements.
Except where noted, the descriptions and instructions in this Operating Manual apply to both the VC820 and VC840.
Unpacking Inspection
Open the package case and take out the Meter. Check the following items carefully to see any missing or damaged part:

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Item Description Qty
1 Operating Manual 1 piece
2 Test Lead 1 pair
3RS232C(I) Interface cable 1 piece
4 Installation Guide & Software (CD-ROM) 1 piece
5Test Clip 1 piece
6 Temperature Probe (VC840 ONLY) 1 piece
In the event you find any missing or damage, please contact your dealer immediately.
Safety Information
In this manual, a Warning identifies conditions and actions that pose hazards to the user, or may damage the Meter or the
equipment under test.
This Meter complies with the standards GB4793.1 & IEC1010-1: In pollution degree 2, overvoltage category (CAT II
1000V, CAT III 600V) and double insulation.
CAT II: local classification of CAT II electronic equipment, portable units. Its transient overvoltage shall be less than that of
CAT III.
CAT III: Distribution level, fixed installation, with smaller transient overvoltage than CAT IV
Rules For Safe Operation

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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:
1. Do not use this Meter in the event you find the test lead, LCD display, or insulation of the case is/are obviously
broken, or you believe this Meter being malfunctioned.
2. If the test lead is/are damaged, replace new test lead with same model no. or identical electrical specifications.
3. When using the test leads, keep your fingers behind the finger guards.
4. Do not impose any effective voltage over 1000V on the terminal and earth of the Meter to prevent electric shock and
damage to the Meter.
5. When the Meter working at an effective voltage over 60V in DC or 30V in AC, special care should be taken for there is
danger of electric shock.
6. Do not operate the Meter with the case (or part of the case) removed; there is danger of electric shock.
7. When replacing fuse or battery, the test leads should be disconnected from the tested circuit and the POWER should be
pressed off before opening the case.
8. Identical nominal fuse of quick response must be used for replacement of a broken fuse.
9. The rotary switch should be placed in the right position and no any changeover of range shall be made during
measurement is conducted to prevent damage of the Meter.
10. The internal circuit of the Meter shall not be altered at will to avoid damage of the Meter and any accident.
11. 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.
12. Soft cloth and neutral detergent should be used to clean the surface of the Meter when servicing. No abrasive and
solvent should be used to prevent the surface of the Meter from corrosion, damage and accident.
13. Do not use the Meter in an environment of high temperature, humidity, and storage of explosive or inflammable
materials. Particularly not to put the Meter in a humid condition for storage. The performance of the Meter may
deteriorate after dampened.
14. Use the proper terminals, function, and range for your measurements.

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Electrical Symbols
AC (Alternating Current) Deficiency of Built-In Battery
DC (Direct Current) Continuity Test
AC or DC Diode
Grounding Fuse
Double Insulated Conforms to Standards of European Union
Warning
Functional Structure (see figure 1)
LCD Display

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Functional Button
Rotary Switch
HzVΩInput Terminal:
Insert the red test lead for testing voltage, frequency/duty cycle, resistance, diode, continuity and capacitance.
COM Terminal:
Insert black test lead.
µAmA Input Terminal: (VC820 ONLY)
Insert red test lead for testing current µA or mA .
µAmA0C Input Terminal: (VC840 ONLY)
Insert red test lead for testing current µA or mA or temperture.
20A Input Terminal:
Insert red test lead for testing current A
Rotary Switch
Switch Position Function
VAC or DC Voltage Measurement
Ω(VC820 ONLY) Continuity or Diode or Resistance Test
Ω(VC840 ONLY) Continuity or Diode or Resistance or Capacitance Test
(VC820 ONLY) Capacitance Test
Hz Frequency Measurement
(VC840 ONLY) Temperature in Celsius
µAAC or DC Current Measurement from 0.1µA to 4000µA
mA AC or DC Current Measurement from 0.01mA to 400.0mA
AAC or DC Current Measurement from 0.001A to 20.00A

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Functional Buttons
Button Function O
p
eration Performed LCD Dis
p
la
y
POWER
(the red button) Power Switch Turn the power on and off.
SELECT
(the blue button) Function Selector Press SELECT to select function when there is more than one function at one rotary switch position; the Meter
beeps.
RANGE Manual or Auto
Range Selection 1. Press RANGE to enter the manual ranging mode; the Meters beeps.
Manually selecting a range causes the Meter to exit
the Hold and REL modes.
2. Press RANGE to step through the ranges available
for the selected function; the Meter beeps.
3. Press and hold RANGE for 2 seconds to return to
autoranging; the Meter beeps.
Hz or %Hz % Frequency or Duty
Cycle Test a. In frequency mode, press Hz % to toggle between frequency measurement (Hz) and duty cycle (%)
mode; the Meter beeps.
b. In voltage or current mode, press Hz % to toggle
between voltage (V) or current (A) measurement
and frequency measurement (Hz) and duty cycle (%)
mode; the Meter beeps.
V or µA or mAor
Aor Hz or %

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REL Relative Value
Mode Press REL to enter and exit the REL mode in any
mode; the Meter beeps.
HOLD H Data Holding Press HOLD to enter and exit the Hold mode in any
mode.
Display Symbols (see figure 2)
Number S
y
mbol Meanin
g
1AC Indicator for AC voltage or current.
VC820: The displayed value is the mean value.
VC840: The dis
p
la
y
ed value is the true rms value.
2TRMS
(VC840ONLY) Indicator for true rms value.

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3The Meter is in the auto range mode in which the Meter automatically selects the
range with the best resolution.
4RS232C Data output is in progress.
5 % Indicator for duty cycle.
6Data hold is active.
7The relative value mode is on to display the stored value minus the present value.
8The 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
a
pp
ears.
90CCentigrade. The unit of temperature.
10 Test of diode
11 The continuit
y
buzzer is on.
Ω,kΩ,MΩΩ:
kΩ:
MΩ:
Ohm. The unit of resistance.
kilohm. 1 x 103or 1000 ohms.
Megohm. 1 x 106or 1,000,000 ohms.
µF, nF F:
µF:
nF:
Farad. The unit of capacitance.
Microfarad. 1 x 10-6 or 0.000001 farads.
Nanofarad. 1 x 10-9 or 0.000000001 farads.
12~16
Hz, kHz, MHz Hz:
kHz:
MHz:
Hertz. The unit of frequency.
Kilohertz. 1 x 103or 1000 hertz.
Meghertz. 1 x 106or1,000,000 hertz.

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V, mV V:
mV Volts. The unit of voltage. Millivolt. 1 x 10-3 or 0.001 volts.
A, mA, µAA:
mA:
µA:
Amperes (amps). The unit of current.
Milliamp. 1 x 10-3 or 0.001 amperes.
Microamp. 1x 10-6 or 0.000001 amperes.
17 Indicates negative reading.
18 OL The in
p
ut value is too lar
g
e for the selected ran
g
e.
Manual Ranging and Autoranging
The Meter has both manual range and autorange options:
zIn the autorange ( ) mode, the Meter selects the best range for input signals.
This allows you to switch test points without having to reset the range.
zIn the manual range mode, you may select the range.
This allows you to override autorange and lock the Meter in a specific range.
The Meter defaults to the autorange mode in measurement functions that have more than one range. When the Meter is in
the autorange mode, is displayed.
To enter and exit the manual range mode:
1. Press RANGE.
The Meter enters the manual range mode and turns off

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Each presses of RANGE increments the range. When the highest range is reached, The Meter wraps to the lowest
range.
NOTE
If you manually change the measurement range after entering the REL or Hold recording modes, the Meter exits these
modes..
2. To exit the manual range model, press and hold RANGE for two seconds.
The Meter returns to the autorange mode and is displayed.
Measurement Operation
A. DC Voltage Measurement
Warning
To avoid harms to you or damages to the Meter from electric shock, please do not attempt to measure voltages higher
than 1000V / 750V TRMS although readings may be obtained.
The DC Voltage ranges are: 400.0mV, 4.000V, 40.00V, 400.0V and 1000V. To measure DC Voltage, connect the Meter as
follows:
1. Insert the red test lead into the HzVΩterminal and the black test lead into the COM terminal.
2. Set the rotary switch to V(DC measurement is default)
3. Connect the test leads across with the object being measured.

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The measured value shows on the display.
In each range, the Meter has an input impedance of 10MΩ. 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).
When DC voltage measurement has been completed, disconnect the connection between the testing leads and the circuit
under test, and remove the testing leads away from the input terminals of the Meter.
B. AC Voltage Measurement
Warning
To avoid harms to you or damages to the Meter from electric shock, please do not attempt to measure voltages
higher than 1000V / 750V TRMS although readings may be obtained.
The AC Voltage ranges are: 400.0mV, 4.000V, 40.00V, 400.0V and 750V. To measure AC Voltage, connect the Meter as
follows:
1. Insert the red test lead into the HzVΩterminal and the black test lead into the COM terminal.
2. Set the rotary switch to V and press SELECT (blue button) to select AC measurement.
3. Connect the test leads across with the object being measured.
The measured value shows on the display.
In each range, the Meter has an input impedance of 10MΩ. 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).
Effective value stability period:

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When the reading obtained is less than “100”, the effective value converter needs a longer time to become stabilize. When
there is no input voltage, the maximum reading displayed is “10”.
When AC voltage measurement has been completed, disconnect the connection between the testing leads and the circuit
under test, and remove the testing leads away from the input terminals of the Meter.
C. Measuring Resistance
Warning
To avoid damages to the Meter or to the devices under test, disconnect circuit power and discharge all the high-
voltage capacitors before measuring resistance.
The resistance ranges are: 400.0Ω, 4.000kΩ, 40.00kΩ, 400.0kΩ, 4.000MΩand 40.00MΩ. To measure resistance, connect
the Meter as follows:
1. Insert the red test lead into the HzVΩterminal and the black test lead into the COM terminal.
2. Set the rotary switch toΩand press SELECT (blue button) to selectΩmeasurement mode.
3. Connect the test leads across with the object being measured.
The measured value shows on the display.
The test leads can add 0.1Ωto 0.2Ωof error to resistance measurement. To obtain precision readings in low-resistance
measurement, that is the range of 400.0Ω, short-circuit the input terminals beforehand, using the relative measurement
function button REL to automatically subtract the value measured when the testing leads are short-circuited from the
reading.
The LCD displays OL indicating open-circuit for the tested resistor or the resistor value is higher than the maximum range

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of the Meter.
When the value of shorted test lead is higher than 0.5Ω, check the test lead connection, proper terminal, function and range
are made properly.
For high-resistance measurement (>1MΩ), it is normal that it will take several seconds to obtain a stable reading.
When resistance measurement has been completed, disconnect the connection between the testing leads and the circuit under
test, and remove the testing leads away from the input terminals of the Meter.
D. Testing for Continuity
Warning
To avoid damages to the Meter or to the devices under test, disconnect circuit power and discharge all the high-
voltage capacitors before testing for continuity.
To test for continuity, connect the Meter as below:
1. Insert the red test lead into the HzVΩterminal and the black test lead into the COM terminal.
2. Set the rotary switch toΩand press SELECT (blue button) to select measurement mode.
3. The buzzer sounds if the resistance of a circuit under test is less than around 50Ω.
When continuity testing has been completed, disconnect the connection between the testing leads and the circuit under test,
and remove the testing leads away from the input terminals of the Meter.

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E. Testing Diode
Warning
To avoid possible damage to the Meter and to the device under test, disconnect circuit power and discharge all
high-voltage capacitors before testing diodes.
Use the diode test to check diodes, transistors, and other semiconductor devices. The diode test sends a current through the
semiconductor junction, then measures the voltage drop across the junction. A good silicon junction drops between 0.5V and
0.8V.
To test a diode out of a circuit, connect the Meter as follows:
1. Insert the red test lead into the HzVΩterminal and the black test lead into the COM terminal.
2. Set the rotary switch toΩand press SELECT (blue button) to select measurement mode.
3. Connect the test leads across with the object being measured.
The measured value shows on the display.
Connect the test leads to the proper terminals as said above to avoid error display. The LCD will display OL indicating open-
circuit for wrong connection. The unit of diode is Volt (V), displaying the positive-connection voltage-drop value.
When diode testing has been completed, disconnect the connection between the testing leads and the circuit under test, and
remove the testing leads away from the input terminals of the Meter.
F. Capacitance Measurement
Warning

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To avoid damage to the Meter or to the equipment under test, disconnect circuit power and discharge all high-
voltage capacitors before measuring capacitance. Use the DC Voltage function to confirm that the capacitor is
discharged.
The Meter’s capacitance ranges are: 40.00nF, 400.0nF, 4.000µF, 40.00µF, and 100.0µF. To measure capacitance, connect the
Meter as follows:
1. Insert the red test lead or the red test clip into the HzVΩterminal and the black test lead or black test clip into the COM
terminal.
2. Set the rotary switch to . (For VC820 switch toΩand press SELECT to select nF measurement mode.)
3. Connect the test leads or the test clips across with the object being measured.
The measured value shows on the display.
The LCD displays OL indicating the tested capacitor is short or it exceeds the maximum range.
For testing the capacitor with polarity, connect the red clip to positive & black clip to negative.
When capacitance measurement has been completed, disconnect the connection between the testing leads and the circuit
under test and remove the testing leads away from the input terminals of the Meter.
To minimize the effect of capacitance stored in the test leads, the test lead should be as short as possible. To measure a small
quantity of capacitance, use REL mode to remove the leads capacitance. Remaining voltage, insulated impedance, &
dielectric absorption from the capacitor may cause the measurement error.
G. Frequency or Duty cycle Measurement

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The measurement range is from 5Hz to 10MHz. To measure frequency, connect the Meter as follows:
1. Insert the red test lead into the HzVΩterminal and the black test lead into the COM terminal.
2. Set the rotary switch to Hz.
3. Connect the test leads across with the object being measured.
The measured value shows on the display.
In frequency mode, press Hz % to toggle between frequency measurement (Hz) and duty cycle (%) mode.
In voltage or current mode, press Hz % to toggle between voltage or current, frequency measurement (Hz) and duty cycle
(%) mode.
Connect the Meter as above mentioned when carrying out duty cycle measurement. The duty cycle measurement range is:
0.1%~99.9%. The LCD displays OL indicating the inputted signal is high or low level.
When Hz or % measurement has been completed, disconnect the connection between the testing leads and the circuit under
test, and remove the testing leads away from the input terminals of the Meter.
H. Temperature Measurement (VC840 ONLY)
Themeasurement range is -40℃1000℃. To measure temperature, connect the Meter as follows:
1. Insert the red temperature probe into the µA mA℃terminal and the black temperature probe into the COM terminal.
2. Set the rotary switch to .
3. Place the temperature probe to the object being measured.
The measured value shows on the display.

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The Meter’s LCD automatically displays the temperature value inside the Meter when there is no temperature probe
connection.
The included point contact temperature probe (Part no. 41700103) can only be used up to 230or 446. For any
measurement higher than that, the rod type temperature probe (Part no. 41700109) must be used instead.
I. DC or AC Current Measurement
Warning
Never attempt an in-circuit current measurement where the open-circuit voltage between the circuit and ground is
greater than 600V.
If the fuse burns out during measurement, the Meter may be damaged or the operator himself may be hurt. Use
proper terminals, function, and range for the measurement. When the testing leads are connected to the current
terminals, do not parallel them across any circuit.
The current measurement has 3 measurement positions on the rotary switch: µA,mA and A .
The µAhas a 400.0µA and 4000µA range, with auto ranging; the mA has a 40.00mA and 400.0mA range, with auto
ranging; A position has only a 4A and 20.00A range.
To measure current, do the following:
1Turn off power to the circuit. Discharge all high-voltage capacitors.
2VC820: Insert the red test lead into the µAmA or 20A terminal and the black test lead into the COM terminal.
VC840: Insert the red test lead into the µAmAor 20A terminal and the black test lead into the COM terminal.

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Use the 20A terminal and Arange if the current value to be tested is an unknown.
3. Set the rotary switch to µA , mA , or A .
4. The Meter defaults to DC current measurement mode. To toggle between DC and AC current measurement function,
press SELECT (blue button).
VC820: AC current is displayed as an mean value (calibrated against sine wave effective value).
VC840: AC current is displayed as true rms value.
5. Break the current path to be tested. Connect the red test lead to the more positive side of the break and the black test
lead to the more negative side of the break.
6. Turn on power to the circuit.
The measured value shows on the display.
Effective value stability period:
When the reading obtained is less than “100”, the effective value converter needs a longer time to become stabilize. When
there is no input voltage, the maximum reading displayed is “10”.
For safety sake, the measuring time for high current should be less than 10 seconds for each measurement and the interval
time between 2 measurements should be greater than 15 minutes.
When current measurement has been completed, disconnect the connection between the testing leads and the circuit under
test, and remove the testing leads away from the input terminals of the Meter.
Operation of Hold Mode
Warning
To avoid possibility of electric shock, do not use Hold mode to determine if circuits are without power. The Hold
mode will not capture unstable or noisy readings.