UNI-T UT90B Operating Manual

Table of Contents

Title Page

Overview
Unpacking Inspection
Safety Information
Rules For Safe Operation
International Electrical Symbols
The Meter Structure
Rotary Switch
Functional Buttons
Display Symbols
Measurement Operation
A. DC & AC Voltage Measurement
B. AC & DC Current Measurement
C. Test for Diodes & Continuity
D. Resistance Measurement
E. Power Charging
The Impedance Changeover Button
The POWER Button
General Specifications
Accuracy Specifications
A. DC Voltage
B. AC Voltage
C. AC Current
D. DC Current
E. Diodes & Continuity Test
F. Resistance
Maintenance
A. General Service
B. Replacing the Fuses

3
4

5
6
8

9

10

11
12
14
14
15
17
20
22

23
23
24

26
26
26
27
27
28
28
29

29
29

Model UT90B: OPERATING MANUAL

1

Model UT90B: OPERATING MANUAL

2

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 Safe Operation"
carefully before using the Meter.

The Model UT90B (hereafter referred to as “the Meter”)
is a 1999 counts 3 1/2 digits multimeter with stabilized
functions, safe design, and reliable performance.

In addition to the conventional measuring function, such
as DC/AC voltage, DC/AC current, resistance, diode and
continuity , it is equipped with advanced design of charging
power through 220V AC or 12-36V AC/DC or solar energy .
With such design, the Meter can be used without battery ,
therefore it will not cause chemical pollution. This is also
a highly applied digital electrical tester of good
performance with full icons display LCD, overload
protection and streamline outlook.

Model UT90B: OPERATING MANUAL

3

Unpacking Inspection

Open the package case and take out the Meter. Check
the following items carefully to see any missing or
damaged part:

In the event you find any missing or damage, please
contact your dealer immediately.

Model UT90B: OPERATING MANUAL

4

Item

1
2

3

Description

English Operating Manual
Test Lead

Holster

Qty

1 piece

1 pair

1 piece

Safety Information

This Meter complies with standards IEC61010: 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 8.

Model UT90B: OPERATING MANUAL

5

Rules For Safe Operation (1)

Warning
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:

l Before 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.
l Inspect 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.
l When using the test leads, keep your fingers
behind the finger guards.
l Do not apply more than the rated voltage, as
marked on the Meter, between the terminals or
between any terminal and grounding.
l 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.
l Use the proper terminals, function, and range
for your measurements.
l 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.
l Disconnect circuit power and discharge all high­ voltage capacitors before testing current,
resistance, diodes or continuity.

l 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.

Model UT90B: OPERATING MANUAL

6

Rules For Safe Operation (2)

l When servicing the Meter, use only the same
model number or identical electrical specifications
replacement parts.
l The internal circuit of the Meter shall not be
altered at will to avoid damage of the Meter and
any accident.
l Soft 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.

l Turn off the Meter when it is not in use.
l Do 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.
l The Meter is suitable for indoor use.

Model UT90B: OPERATING MANUAL

7

International Electrical Symbols

AC (Alternating Current).
DC (Direct Current).
Grounding.
Double Insulated.

Deficiency of Power.
Fuse
Warning. Refer to the Operating Manual.
Conforms to Standards of European Union.

Model UT90B: OPERATING MANUAL

8

The Meter Structure (see figure 1)

9

( figure 1)

1 LCD Display.
2 Solar Panel.
3 Impedance Changeover Button.
4 Rotary Switch.
5 Input Terminals.
6 Power Button.

Model UT90B: OPERATING MANUAL

10

Rotary Switch

Below table indicated for information about the rotary
switch positions.

µ

µ

Model UT90B: OPERATING MANUAL

11

Functional Buttons

Below table indicated for information about the functional
button operations.

AC voltage measurement.

Turn the power on and off.
Impedance changeover between

10MΩ and 400kΩ

LOW imp.

400k Ω

Model UT90B: OPERATING MANUAL

12

Display Symbols(1) (see figure 2)

( figure 2)

No. Symbol Meaning

1

The 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 appears.

2

4

Indicates negative reading.

5

Test of diode.

The continuity buzzer is on.

3

CHARGE

Charge indicator.

6

Indicator for AC voltage or current.
The displayed value is the mean
value.

Model UT90B: OPERATING MANUAL

Display Symbols(2) (see figure 2)

Ω: Ohm. The unit of resistance.
kΩ: kilohm.1 x 103 or 1000 ohms.
MΩ: Megaohm. 1 x 106 or
1,000,000 ohms.

µA, mA, A

A: Amperes (amps). The unit of
current.
mA: Milliamp. 1 x 10-3 or 0.001
amperes.

µA: Microamp. 1x 10

-6

or 0.000001

amperes.

V: Volts. The unit of voltage.
mV: Millivolt. 1 x 10-3 or 0.001 volts.

No. Symbol Meaning

7

Ω,kΩ,MΩ

mV, V

13

Model UT90B: OPERATING MANUAL

14

Measurement Operation(1)
A.DC & AC Voltage Measurement (see figure 3)

red black

( 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 must be
3 seconds. To avoid damages to the Meter, please
do not attempt to press 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 and 1000V.
The AC voltage ranges are: 2.000V, 20.00V, 200.0V and

750.0V.
To measure DC & AC voltage, connect the Meter as

follows:

Model UT90B: OPERATING MANUAL

15

Measurement Operation(2)

1. Insert the red test lead into the VΩ terminal and
the black test lead into the COM terminal.

2. Set the rotary switch to an appropriate measurement
position in V or V .

3. Connect the test leads across with the object being
measured.
The measured value shows on the display.

B.AC & DC Current Measurement (see figure 4)

Note

l When DC/AC voltage measurement has been
completed, disconnect the connection between the
testing leads and the circuit under test.
l 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).

black red

( figure 4)

Model UT90B: OPERATING MANUAL

16

Measurement Operation(3)

Warning
Never attempt an in-circuit current measurement
where the open-circuit voltage between the circuit
and ground is greater than 60V.
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 measurement ranges of AC current are: 200.0µA,

2.000mA, 20.00mA, 200.0mA and 10.00A.
The measurement ranges of DC current are: 200.0 µA,

2.000mA, 20.00mA, 200.0mA and 10.00A.
To measure current, do the following:

1. Turn off power to the circuit. Discharge all high­ voltage capacitors.

2. Insert the red test lead into the µAmA or 10A terminal
and the black test lead into the COM terminal.
Use the 10A terminal and 10A or 10A range if
the current value to be tested is an unknown.

3. Set the rotary switch to an appropriate measurement
position in A range or A .

4. AC current is displayed as an effective value of since
wave (mean value response).

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.

Model UT90B: OPERATING MANUAL

17

Measurement Operation(4)

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 and continuity.

To avoid harms to you, never attempt to measure
voltages higher than 60V DC/30V AC.

( figure 5)

Note

l 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.

l When AC/DC current measurement has been
completed, disconnect the connection between the
testing leads and the circuit under test.

C.Test for Diodes & Continuity

Testing Diodes (see figure 5)

red black

Model UT90B: OPERATING MANUAL

20

Measurement Operation(7)

D.Resistance Measurement (see figure7)

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.

To avoid harms to you, never attempt to measure
voltages higher than 60V DC/30V AC.

( figure 7)

red black

The resistance ranges are: 200.0Ω, 2.000kΩ, 20.00kΩ,

200.0kΩ, 2.000MΩand 20.00MΩ.
To measure resistance, connect the Meter as follows:

1. Insert the red test lead into the VΩ terminal and
the black test lead into the COM terminal.

2. Set the rotary switch to Ω .

3. Parallel connect the test leads across with the object
being measured.

4. The measured value shows on the display.

Note

l The LCD displays 1 indicating open-circuit for the
tested resistor or the resistor value is overload.
l The test leads can add 0.1Ωto 0.2Ω of error to

Model UT90B: OPERATING MANUAL

21

Measurement Operation(8)

Model UT90B: OPERATING MANUAL

25

General Specifications(2)

l Safety/Compliances : IEC61010: CAT. II 1000V,
CAT. III 600V overvoltage
and double insulation
standard.
l Certification :

Model UT90B: OPERATING MANUAL

26

Accuracy: (a% reading + b digits),guarantee for 1 year.
Operating temperature:23oC~5oC.
Relative humidity:<75%.
Temperature coefficient: 0.1 x (specified accuracy) / 1oC.

Remark: Input impedance: 10MΩ
B.AC Voltage

Remarks:

l Input impedance: 10MΩ .
l Frequency response: 40Hz~400Hz.
l Display effective value of sine wave (mean value

response).

A.DC Voltage

200mV

2V

20V

200V

1000V

0.1mV
1mV

10mV

100mV

1V

Range Resolution

(0.5%+2)

Overload
Protection

Accuracy

230V AC

(0.8%+3)

1000V DC

or 750V AC

continuous.

2V

20V

200V
750V

1mV

10mV

100mV

1V

Range Resolution

Overload
Protection

Accuracy

1000V DC

or 750V AC

continuous.

40~100Hz:

(0.8%+5)

100~400Hz:

(1.0%+10)

40~100Hz:

(1.0%+5)

100~400Hz:

(1.0%+10)

Accuracy Specification(1)

Model UT90B: OPERATING MANUAL

28

E. Diodes & Continuity Test

1mV

1Ω

Range Resolution Overload Protection

230V rms

Accuracy Specification(3)

F. Resistance

Range Resolution

Overload
Protection

Accuracy

200Ω

2kΩ

20kΩ

200kΩ

2MΩ

20MΩ

0.1Ω

1Ω

10Ω

100Ω

1kΩ

10kΩ

(0.8%+3) +
short-circuit the
input terminals

(0.8%+3)

(1.2%+5)

230V rms

Remarks:

Open circuit voltage approximate 3V.

Model UT90B: OPERATING MANUAL

29

Maintenance(1)

This section provides basic maintenance information
including battery and fuse replacement instruction.

Warning
Do not attempt to repair or service your Meter unless
you are qualified to do so and have the relevant
calibration, performance test, and service information.
To avoid electrical shock or damage to the Meter, do
not get water inside the case.

A. General Service

l Periodically wipe the case with a damp cloth and
mild detergent. Do not use abrasives or solvents.
l To clean the terminals with cotton bar with detergent,
as dirt or moisture in the terminals can affect readings.
l Turn the Meter off when it is not in use and take out
the battery when not using for a long time.
l Do not store the Meter in a place of humidity, high
temperature, explosive, inflammable and strong
magnetic field.

B.Replacing the Fuses (see figure 9)

Screw

Holster

( figure 9)

Model UT90B: OPERATING MANUAL

30

Maintenance(2)

Warning
To avoid electrical shock or arc blast, or personal
injury or damage to the Meter, use specified fuses
ONLY in accordance with the following procedure.

Replacement of the fuses is seldom required. Burning
of a fuse always results from improper operation.

** END **

This operating manual is subject to change without notice.

Model UT90B: OPERATING MANUAL

31

Model UT90B: OPERATING MANUAL

32

Copyright 2001 Uni-Trend International Limited.

All rights reserved.

Manufacturer: UNI-TREND TECHNOLOGY(DONG GUAN)LIMITED
Address: Dong Fang Da Dao, Bei Shan Dong Fang Industrial
Development District, Hu Men Town, Dong Guan City,
Guang Dong Province, China
Headquarters: Uni-Trend International Limited
Address: Rm901, 9/F, Nanyang Plaza 57 Hung To Road
Kwun Tong Kowloon, Hong Kong
Tel: [phone]
Fax: [phone]
Email: [e-mail]
http://www.uni-trend.com

Model UT90B: OPERATING MANUAL