Unit UT90A User manual

Model UT90A: OPERATING MANUAL=VC220
1
Table of Contents
Title Page
Overview
Unpacking Inspection
Safety Information
Rules For Safe Operation
International Electrical Symbols
The Meter Structure
LCD Indicators
Rotary Switch
Functional Buttons
Measurement Operation
A. AC/DC Voltage Measurement
B. AC/DC Current Measurement
C. Resistance Measurement
D. Diodes Measurement
E. Continuity Measurement
F. Power Voltage Measurement
General Specifications
Accuracy Specifications
A. DC Voltage
B. AC Voltage
C. DC Current
D. AC Current
E. Resistance
F. Diodes Test
G. Continuity Test
Fuse Replacement
Maintenance

Model UT90A: OPERATING MANUAL
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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
To avoid electric shock or personal injury,
read the “Safety Information” and “Rules for
Safety Operation” carefully before using the
Meter.
The Model UT90A(hereafter referred to as “the
Meter”) is a 1999 counts low power waste
electrical tester with and stabilize functions,
safety operations, and reliable performance.
In addition to the conventional measuring
function, such as DC/AC voltage, resistance,
diode and continuity and power voltage test, it is
also a highly applied digital electrical tester of
good performance with big size full functions
symbols indication, full overload protection and
special appearance.
Unpacking Inspection
Open the package case and take out the Meter.
Check the following items carefully to see any
missing or damaged part:
Item
Description
Qty
1
Operating Manual
1
piece
2
Test Lead
1
pair

Model UT90A: OPERATING MANUAL
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3
certificate
1 piece
In the event you find any missing or damage,
please contact your dealer immediately.
Safety Information
This Meter complies with GB4793 standard for
safety electrical measuring and test equipment,
and IEC61010-1: in pollution degree 2,
overvoltage category (CAT II 1000V, CAT III
600V) and double insulation.
Use the Meter only as specified in this operating
manual, otherwise the protection provided by the
Meter may be impaired.
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.
A Note identifies the information that user should
pay attention on.
International electrical symbols used on the
Meter and in this Operating Manual are
explained on page XXX.
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

Model UT90A: OPERATING MANUAL
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to the following rules:
lBefore using the Meter inspect the
case. Do not use the Meter if it is
damaged or the case (or part of the
case) is removed. Look for cracks or
missing plastic. Pay attention to the
insulation around the connectors.
lInspect the test leads for damaged
insulation or exposed metal. Check the
test leads for continuity. Replace
damaged test leads with identical
model number or electrical
specifications before using the Meter.
lWhen using the test leads, keep your
fingers behind the finger guards.
lDo not apply more than the rated
voltage, as marked on the Meter,
between the terminals or between any
terminal and grounding.
lWhen the Meter working at an effective
voltage over 60V in DC or 30V in AC,
special care should be taken from there
is danger of electric shock.
lUse the proper terminals, function, and
range for your measurements.
lThe 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.
lDisconnect circuit power and discharge
all high-voltage capacitors before
testing resistance, diodes or continuity.
lCharge as soon as the Meter indicator
appears to keep precision of the

Model UT90A: OPERATING MANUAL
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readings.
lRemove test leads from the test circuit
before changeover of range. Turn the
Meter power off before connect the
Meter to circuit and check the fuse
before measuring current.
lWhen servicing the Meter, use only the
same model number or identical
electrical specifications replacement
parts.
lThe internal circuit of the Meter shall not
be altered will to avoid damage of the
Meter and any accident.
lSoft cloth and mild 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.
lTurn off the Meter when it is not in use
for a long time.
lDo not use or store the Meter in an
environment of high temperature,
humidity, explosive, inflammable and
strong magnetic field. The performance
of the Meter may deteriorate after
dampened.
International Electrical Symbols
AC (Alternating Current).
DC (Direct Current).
Grounding.
Double Insulated.

Model UT90A: OPERATING MANUAL
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Deficiency of Built-In Battery.
Warning. Refer to the Operating
Manual.
China Technology Supervision
Bureau, license for measuring
instrument Manufacture
Conforms to Standards of European
Union.
The Meter Structure (see figure 1)
?LCD Display.
?Impedance changeover button.
?Rotary Switch.
?Input Terminals.
?Power Button.
LCD indicators(see figure 2)
?~appear at AC measurement, disappear
at DC measurement.
?display the minus readings.
?high voltage indicator.
?battery deficiency indicator.
?continuity measurement indicator.
?diodes measurement indicator.
?Connect Terminal terminal connect indicator.
?
O?KO?MOResistance unit
MV?VVoltage unit
µA?mA?ACurrent unit
Rotary Switch

Model UT90A: OPERATING MANUAL
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Below table indicated for information about the
rotary switch positions.
Rotary
Switch
Positio
n
Function
V DC voltage measurement range
from 200.0mV to 1000V.
VAC voltage measurement range
from 2.000V to 750.0V.
OOResistance measurement range
from 200.0Oto 20.00MO.
Diode test.
Continuity test.
ADC current measurement range
from 200.0mA to 20.00A.
AAC current measurement range
from 200.0µA to 20.00A.
Power voltage measurement
Turn on/off the Meter.
Functional Buttons
Below table indicated for information about the
functional button operations.
Button Measur
ing
Functi
on
Operation Performed

Model UT90A: OPERATING MANUAL
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Impeda
nce
change
over
button
AC/DC
voltage
range
It is used to inspect
the resistance of
supply power under
250V
MAX.(??????)
Any
rotary
switch
position
Turn the power of the
Meter on or off.
Measurement Operation
A.AC/DC Voltage Measurement (see figure
3)
Warning
To avoid harms to you or damages to the
Meter from electric shock, please do not
attempt to measure voltages higher than
1000V DC/750V AC although readings may be
obtained.
Impedance Changeover Button turn on time
should=3 seconds. To avoid damages to the
Meter, please do not use the Impedance
Changeover Button when the measured
voltage is higher than 250V.
The DC voltage ranges are: 200.0mV, 2.000V,
20.00V, 200.0V, 1000V; The AC voltage ranges
are: 2.000V, 20.00V, 200.0V, 750.0V. To measure

Model UT90A: OPERATING MANUAL
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AC/DC voltage, connect the Meter as follows:
1. Insert the red test lead into the“VO)”
terminal and the black test lead into the
COM terminal.
2. Set the rotary switch to“V”or“V”,and
Connect the test leads across with the
power or load being measured.
3. The measured value shows on the
display,which is an effective value of sine
wave (mean value response).
4. In each range, the Meter has an input
impedance of 10MO. This loading effect
can cause measurement errors in high
impedance circuits. If the circuit impedance
is less than or equal to 10kO, the error is
negligible (0.1% or less).
5. Manual Impedance Changeover
Button“10MO/400kO”can be used to check
inside impedance of supply power under
250V MAX.
Note
lWhenAC/DC voltage measurement has
been completed, disconnect the connection
between the testing leads and the circuit
under test.
lPay attention to avoid harms to you from
electric shock during high voltages
measurement.
B.AC/DC Current Measurement (see figure
4)
Warning

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To avoid damages to the built-in fuse and the
Meter, please do not attempt parallel connect
the test leads with any circuit while the test
leads are inserted into the current terminal.
For the safety requirement, when measure
high current, every measure time should<10
seconds and the time between two
measurements should >15 minutes.
The measurement ranges of DC current are:
200mA,2mA,20mA,200mA,20A; The
measurement ranges of AC current are:
200.0µA,2.000mA,20.00mA,200.0mA and
20.00A. To measure current, do the following:
1Insert the red test lead into the“µA
mA ”or“20A”terminal and the black test
lead into the COM terminal.
2Set the rotary switch to“A”or“A”,and
Connect the test leads across with the
circuit being measured.
3. The measured value shows on the display,
it is an effective value of sine wave (mean
value response).
Note
lTurn off the power of circuit being
measured before series connection
between the Meter and the circuit.
lUse proper terminals and ranges for the
measurement.
lPlease use the ranges from high to low if
the current not being confirmed.
lWhen current measurement has been

Model UT90A: OPERATING MANUAL
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completed, disconnect the connection
between the test leads and measured
circuit.
C.Resistance Measurement(see figure 5)
Warning
To avoid injury to the user, please do not
attempt the voltage higher than 60V/DC or
30V/AC.
The resistance ranges are: 200.0O, 2.000kO,
20.00kO, 200.0kO, 2.000MOand 20.00MO. To
measure resistance, connect the Meter as
follows:
1. Insert the red test lead into the VO
terminal and the black test lead into the
COM terminal.
2. Set the rotary switch toO, parallel connect
the test leads across with the object being
measured.
3. The measured value shows on the display.
Note
lThe LCD will display “1”indicating open-
circuit for the tested resistor or the resistor
value is higher than the maximum range of
the Meter.
lTo measure online resistance, please turn
off power of the circuit and discharge all
capacitors.
lThe test leads can add 0.1Oto 0.2Oof error
to resistance measurement. To obtain

Model UT90A: OPERATING MANUAL
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precision readings in low-resistance
measurement, that is the range of 200.0O,
short-circuit the input terminals beforehand
and record the reading obtained (called this
reading as X). (X) is the additional
resistance from the test lead.
Then use the equation:
measured resistance value (Y) -(X) =
precision readings of resistance.
lWhen the resistance reading=0.5Oin the
shorten-circuit, please check for loose test
leads or other reasons.
lFor high-resistance measurement (>1MO),
it is normal taking several seconds to
obtain a stable reading, and it is better to
choose short measuring cable.
lWhen resistance measurement has been
completed, disconnect the connection
between the testing leads and the circuit
under test.
D.Diodes Measurement (see figure 6)
Warning
To avoid injury to the user, please do not
attempt the voltage higher than 60V/DC or
30V/AC.
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.

Model UT90A: OPERATING MANUAL
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To test a diode out of a circuit, connect the Meter
as follows:
1. Insert the red test lead (anode “+”) into the
VOterminal and the black test lead
(cathode “-”) into the COM terminal.
2. Set the rotary switch to , place the red
test lead on the component’s anode and
place the black test lead on the
component’s cathode.
3. For forward voltage drop readings on any
semiconductor component, the measured
value shows on the display and the unit of
diodes measurement is mV.
Note
lIn a circuit, a good diode should still
produce a forward voltage drop reading of
500mV to 800mV.
lConnect the test leads to the proper
terminals as mentioned above to avoid
error display. The LCD will display “1”
indicating open-circuit or polarity for wrong
connection.
lOpen-circuit voltage of diodes
measurement is about 3V.
lTo measure online capacity, please turn off
power of the circuit and discharge all
capacitors.
lWhen diode testing has been completed,

Model UT90A: OPERATING MANUAL
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disconnect the connection between the
testing leads and the circuit under test.
E. Continuity Measurement(see figure 7)
Warning
To avoid injury to the user, please do not
attempt the voltage higher than 60V/DC or
30V/AC.
To avoid damages to the Meter or to the
devices under test, disconnect circuit power
and discharge all the capacitors before
measuring continuity.
To test for continuity, connect the Meter as
below:
1. Insert the red test lead into the VO
terminal and the black test lead into the
COM terminal.
2. Set the rotary switch to , connect the
test leads across with the power being
measured.
3. The resistance of a open circuit under test
is>100O.
4. The buzzer sounds continuously if the
resistance of a circuit under test is =10O,
and that shows the circuit is well
connected.
5. The measured approximate circuit
resistance value shows on the display, the
unit O.
Note
lTo measure online capacity, please turn off
power of the circuit and discharge all

Model UT90A: OPERATING MANUAL
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capacitors.
lOpen-circuit voltage of continuity
measurement is about 3V.
lWhen continuity testing has been
completed, disconnect the connection
between the testing leads and the circuit
under test.
F. Power Voltage measurement(see figure 8)
Warning
To avoid damage to the inside fuse and the
Meter, please do not attempt using battery
and power of any other specification to
measure except prescribed as Note.
The measure the power voltage, connect the
Meter as follows:
1. Insert the red test lead into theµA
mA terminal and the black test lead
into the COM terminal.
2. Set the rotary switch to , place the red test
lead on the anode of the power under test
and place the black test lead on the cathode
of the power under test.
3. The measured value shows on the display.
Note
lThe range of 1.5V only fit for the measure
of 1.5V Battery, inside load resistance is
38O.

Model UT90A: OPERATING MANUAL
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lThe range of 9V only fit for the measure of
9V Battery, inside load resistance is 38O.
General Specifications
lMaximum Voltage between any Input
Terminals and COM Terminal: 1000Vp.
lFuse protection of µA mA terminal: 300mA
250V fast melt fuse.
lFuse protection of 20Aterminal: 20mA 250V
fast melt fuse.
lEquipped with full icons display.
lMaximum Display: Display: 1999.
lMeasurement Speed: Updates 2-3 times
/second.
lRange: Manual.
lPolarity: Automatically display.
lOver load indicator: “1”.
lBattery Deficiency: Display .
lTemperature:
Operating: 0?~40?(32?~104?).
Storage: -10?~50?(14?~122?).
lRelative Humidity: =75% @ 0?- 30?;
=50% @ 31 - 40?.
lSupply Power: 6F229V.
lDimensions (HxWxL): 179 x 88 x 39mm.
lWeight: ?g.
lSafety/Compliances:
IEC61010: CAT II 1000V?CAT III 600V.
lCertification: CMC(94) 03000148
Accuracy Specifications

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Accuracy:±(a%reading + bdigits), guarantee
for 1 year.
Operating temperature:18 - 28?.
Relative humidity:=75%RH.
A.DC Voltage
Range Resolution Accuracy:
±(a%reading +
bdigits)
200mV 0.1mV
2V 1mV
20V 10mV
200V 100mV
±(0.5%+2)
1000V 1V ±(0.8%+3)
Remark:
?Input impedance: 10MO.
?Overload Protection: 1000V DC or 750V AC
continuously measure(except 200mV 230V AC).
B.AC Voltage
Range Resolution Accuracy:
±(a%reading + b
digits)
2V 1mV
20V 10mV
200V 100mV ±(0.8%+5)
750V 1V ±(1.0%+5)
Remarks:
?Input impedance: 10MO.
?Overload Protection: 1000V DC or 750V AC
continuously measure.
?Frequency response: 40Hz ~ 400Hz.
?Displays effective value of sine wave (mean
value response).

Model UT90A: OPERATING MANUAL
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C.DC Current
Range Resolution Accuracy:
±(a%reading +
bdigits)
200mA 0.1µA
2mA 1µA
20mA 10µA
200mA 0.1mA
±(0.8%+2)
20A 10mA ±(1.2%+5)
Remarks:
?Overload Protection:
AtµA mA range: Fuse 5×20mm F0.3A 250V.
At A range:
Fuse 6×25mm F20A 250V.
continuous measure time<10 seconds.
time between two measurements>15 minutes.
D. AC Current
Range Resolution Accuracy:
±(a%reading +
bdigits)
200µA0.1µA
2mA 1µA
20mA 10µA
200mA 0.1mA
±(1.0%+5)
20A 10mA ±(2.0%+5)
Remarks:
?Frequency response: 40Hz – 400Hz.
?Overload Protection:
AtµA mA range: Fuse 5×20mm F0.3A 250V.
At A range:
Fuse 6×25mm F20A 250V.
continuous measure time<10 seconds.

Model UT90A: OPERATING MANUAL
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time between two measurements>15 minutes.
E. Resistance
Range Resolution Accuracy:
±(a%reading + b
digits)
200O0.1O
2kO1O
20kO10O
200kO100O
2MO1kO
±(0.8%+3)
20MO10kO±(1.2%+5)
Remarks:
?Overload Protection: 230V rms.
F. Diodes Test
Range Resolution Remark
1mV
Open-circuit
voltage is about 3V;
transistor PN
normal voltage is
about 0.5~0.8V.
Remarks:
?Overload Protection: 230V rms.
G. Continuity Test
Range Resolutio
nRemark

Model UT90A: OPERATING MANUAL
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1O
Open circuit voltage is
about 3V; Set the
resistance of a open
circuit>100O,buzzer will
not sound; Set the
resistance of a well
connected circuit=10O,
buzzer sounds
continuously.
Remark:
?Overload Protection: 230V rms.
Fuse Replacement(see figure 9)
Warning
To avoid electrical shock or injury to the user
because of wrong readings of the Meter,
please inspect the damage of fuse inside
when there is not any response on the
display during current measurement. Replace
the damaged fuse with identical model
number or electrical specifications.
To replace the fuse as follows:
1. Turn the Meter to OFF position, and remove
the test leads from terminals.
2. Take off the holster as figure 9 shows.
3. Remove the 3 screws from the case bottom,
separate the case bottom, then replace the
damaged fuse.
MAINTENANCE
This section provides basic maintenance
information including battery replacement
instruction.