RAGU 81D User manual

RAGU 81D DIGITAL MULTIMETER
OPERATION MANUAL

Contents
I. General...................................................- 1 -
Ⅱ. Open-package Inspection....................- 2 -
III. Safety Considerations......................... - 3 -
IV.Instrument Panel & Button Function
Description................................................- 9 -
V. Other Functions.................................. - 12 -
VI、Property...........................................- 13 -
1．General Property ......................- 13 -
2．Technical Property....................- 14 -
2-2-1. DCV.............................- 15 -
2-2-2. ACV True RMS........... - 16 -
2-2-3. DCA.............................- 18 -
2-2-4. ACA True RMS........... - 20 -
2-2-5. Resistance (Ω)............. - 23 -
2-2-6.Diode and Continuity Test- 25 -
2-2-7. Capacity (C).................- 28 -
2-2-8. Frequency (F).............. - 29 -
2-2-9. Temperature (℃/℉).... - 31 -
VII. Instrument Maintenance.................. - 33 -
VIII. Fault Elimination............................- 36 -

I. General
The RAGU 81D digital multimeter,
equipped with the LCD display of text height
18.9mm, is a 3 3/4 digital multimeter which
has merits of clear reading, stable
performance and high reliability.
It could be used to measure DC voltage,
AC voltage, DC current, AC current,
resistance, temperature, capacity, frequency /
duty cycle, diode and to make on-and-off test.
Meanwhile, it is available for unit symbol
display, automatic/manual range switching,
automatic power off and alarm function. The
complete machine takes an integrated circuit
which can directly drive LCD 8-bit
microprocessor and double-integrating A/D

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switching and a digital display drive offering
high resolution and high precision. Due to its
complete functions, high measurement
accuracy and convenient operation, the
multimeter is the ideal tool in laboratory and
factory as well as for radio fans and family.
Ⅱ. Open-package Inspection
Open the package box and take out the meter,
check carefully if the following accessories
are absent or damaged. If there were any
absence or damage, please contact the
distributor immediately.
Digital Multimeter 1 PC
Instruction Manual 1 copy
Test Leads 1 pair
Temperature Probe (K-Thermocouple) 1 PC

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AAA (1.5v) 7# batteries 2 PCs
III. Safety Considerations
The design of meter is in accordance
with IEC1010 clause (the safety standard
issued by International Electrotechnical
Commission). Prior to the operation of the
instrument, please read the safety
considerations first.
1. When DC voltage is higher than 30V, AC
voltage is higher than 25V, current is
higher than 10mA, AC power line with
inductive load or power line during electric
fluctuation is measured. Please beware of
electric shock.
2. Prior to measurement, check if the
measurement function switch is at the

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correct position. Check if the test lead is
contacted reliably, connected correctly, and
grounded well and etc. in order to avoid
electric shock.
3. Only if the meter is used with the matched
test lead, can it meet the requirements of
safety standard. When the line of the test
lead is damaged, it is necessary to replace
another one of the same model or the same
electrical specification.
4. Don’t use other unconfirmed or
disapproved fuse to replace the original
one inside the meter. Only the fuse of the
same model or same specification can be
replaced. Before the replacement, the test
lead must leave the measuring point and
ensure there is no any signal at the input

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terminal.
5. Don’t use other unconfirmed or
disapproved batteries to replace the
batteries inside the meter. Only the
batteries of the same model or same
electrical specification can be replaced.
Before the replacement, the test lead must
leave the measuring point and ensure there
is no any signal at the input terminal.
6. When the electrical measurement is made,
never let your body get in touch with the
ground directly, and don’t touch uncovered
metal terminal, output port, lead clamp etc.
Dry clothes, rubber shoes, rubber cushion
and other insulating material are usually
used to keep your body insulated against
the ground.

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7. Don’t store and use it in the
high-temperature, high-humidity,
inflammable environment and strong
magnetic field.
8. It may cause damage to the meter and
endanger the operator’s safety if you take
any voltage measurement that exceeds
the limits. The ultimate voltage value
permitted for measurement is marked on
the instrument panel. Never take
measurement or input the ultimate value
which exceeds the standard in order to
avoid electric shock and damage to the
meter.
9. When the test lead is inserted into the
current socket, don’t take any voltage

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measurement to prevent damaging the
meter and endangering the operator’s
safety.
10. Don’t try calibrating or repairing the
meter. When necessary, only the qualified
professional personnel who have had
special training or gained approval can
make it.
11. During measurement, the requirement of
measurement function must be in
accordance with LCD display. Please be
sure to disconnect the line of the test leads
with the measured object first and ensure
there is no any input signal. It is forbidden
to switch the function/range selection

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switch during measurement.
12. When “ ”is shown on LCD display,
please replace battery immediately to
ensure the measurement precision.
13. It is not allowed to insert the test lead into
the current terminal to measure voltage!
14. Please don’t change the circuits of the
meter by yourself to prevent damaging
the meter and endangering the
operator’s safety.
15. Description of Safety Symbols

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F
Hz
FUSED
400mA MAX
mA
V
COM
10A
C
Hz
1
2
3-1
3-2
3-3
3-4
4
5-1
5-2 5-3
IV. Instrument Panel & Button Function
Description
1. Instrument
Model
Number
2.LCD
Display:
Display the
measured data
and unit.
3. Function
Button
3.1.SELECT(function
switch)：Press this button, the function
could switch between DC/AC/

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3.2.RANGE(auto/manual range switch):
The meter is in automatic range when starts
up, press the “RANGE” button to activate
manual range mode. In the mode of manual
range, each press lets the meter skip to the
previous shift. When it goes to the highest
shift, it goes back to the lowest shift
automatically. The procedure repeats again
in the same order. Press the “RANGE”
button over 2 seconds, it will exit from
manual range measurement mode and shift
to automatic range measurement mode.
3.3. HOLD（Data Hold）：Press this button,
the reading shall be hold and kept on
LCD; Press it again, the meter enters
into normal measurement status.

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3.4 REL (Relative Value Measurement):
The relative value measurement of all
functions could be conducted by
pressing this button except the Hz/Duty
function. Frequency/duty cycle: press
this button to select frequency or duty
cycle measurement mode.
4.Function/Range Selection Switch：It could
be used to change the measurement
function and range.
5. Input Terminals
5.1.Current, Voltage, Diode, Resistance,
Capacity, Frequency, Buzzer,
Temperature“-”Input terminal.
5.2.10A“+”input terminal.

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5.3.Voltage、Diode、Resistance, Capacity,
Frequency, Buzzer, Temperature and“+”
Input terminal with current less than
400mA.
V. Other Functions
Automatic Power off
During measurement, the meter will
automatically shut down (enter sleeping
mode) to save power if function buttons and
function/range selection switch are not
operated in 15 minutes. In auto power off
mode, press any function buttons or rotate the
function/range selection switch, the
instrument will get into the auto power on
mode (working mode); the auto power off
mode will be canceled by pressing the

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SELECT button to turn on the instrument.
VI、Property
1．General Property
1-1. Display：LCD
1-2. Max Display ：3999 （3 3/4 ）counts
automatic polarity display and unit
display
1-3. Measuring Method ：Dual integral A/D
converter
1-4. Sampling Rage：Approx. 3 times / sec.
1-5. Over Range Indication：Display“OL”
1-6. Low Battery Indication：“ ”symbol
appears；
1-7 ．Operation Environment: (0 ～40) ℃ ，
Relative Humidity: ＜80% ；
1-8 ．Storage Environment: (0 ～50) ℃ ，

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Relative Humidity: ＜80% ；
1-9．Power: 2pcs 1.5V batteries (“AAA”7#
battery)
1-10．Dimension (size): 145×74×36mm
1-11．Weight: Approx. 190g（Including 2pcs
1.5V batteries）
1-12．Accessories: Instruction Manual (1 pc),
Holster (1 pc), Outer packing box (1 pc),
10A test leads (1 pair), K-Thermocouple
and 1.5V batteries (2 pcs).
2．Technical Property
2-1. Accuracy:±(a%×reading＋number of
digits)，at (23±5)℃，relative humidity ＜
75%. Warranty is one year, starting on shipping
date.
2-2.Technic Specification

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2-2-1. DCV
1. Turn the function/range selection switch
to " " Range;
2. The initiate state of the meter is in
automatic range status, which shows
"AUTO" symbol;
3. Make the test leads contacted to the testing
points. The voltage and polarity of the
point where the red test lead is contacted
will be displayed on the screen.
Caution:
1. Don't measure voltage over 600V.
Otherwise, it may cause damage to the
meter.
2. When measuring high voltage, more
attention should be paid to personal safety
and avoid your body getting in touch with

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high voltage circuit.
Range
Accuracy
Resolution
400mV
±(0.5%+4d)
100uV
4V
1mV
40V
10mV
400V
100mV
600V
±(1.0%+4d)
1V
Input Impedance: 400mV>40MΩ; 10MΩ at
other Ranges.
Overload Protection: 600V DC or 600V AC
Peak Value.
2-2-2. ACV True RMS
1. Insert the black test lead into the hole of
“COM” and red one into " ";
2. Rotate function switch to " " gear,

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press “SELECT” button to select the AC
measurement mode.
3. The initiate state of the meter is in
automatic range status, which shows
“AUTO" symbol;
4. Make the test leads contacted to the testing
points. The voltage of the point where the
red test lead is contacted will be displayed
on the screen.
Caution:
1. Don't measure voltage over 600V.
Otherwise, it may cause damage to the
meter.
2. When measuring high voltage, more
attention should be paid to personal safety
and avoid your body getting in touch with
high voltage circuit.

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Range
Accuracy
Resolution
4V
±(0.8%+6d)
1mV
40V
10mV
400V
100mV
600V
±(1.0%+6d)
1V
Input Impedance: >10MΩ;
Overload Protection: 600V DC or 600V AC
Peak Value;
Frequency Response: (50～200) Hz;
Display: Average value response (RMS of
sine wave).
2-2-3. DCA
1.Insert the black test lead into the "COM"
input terminal and red one into the " "
input terminal(Max 400mA), or 10A input