UNI-T UT501A Operating Manual

I. Overview

UT501A Insulation Resistance Tester is designed with brand-new design and
combination of massive integrated and digital circuits; it can measure insulation
resistance, AC voltage, etc, and enjoys high degree of accuracy, stable performance,
easy operation and reliability. It is used for insulation resistance measurement for
insulation materials and various kinds of electric equipments such as transformer,
electric machines, cables, switches, electrical appliances, a ideal tool for electric
equipment maintenance, testing and inspection.

II. Safety Information

UT501A is designed and manufactured in compliance with: IEC61010-1 CATIII 600V,
Double Insulation and Pollution Degree 2 standards. Operate as specified in the manual,
otherwise the protection offered by the tester would be impaired.

Safety Symbols 1

Danger

Identifies conditions and actions that may pose hazard to the
users.

Warning

Alerts users to avoid electric shock.

Caution

Identifies conditions and actions that may cause damage to
the instrument or affect accurate measurement.

Do not measure any AC circuit with voltages above 750V.

Do not measure in flammable places. Spark may cause explosion.

In case that the surface of the instrument is wet or the operator's hands are wet,

please do not operate this instrument.

Do not touch the electric conduction parts of test leads when testing.

Do not open the battery cover when testing.

When insulation resistance is measured, do not touch the electric wire under test.

Danger

Warning

Stop using the instrument if it works abnormally. For example: the

equipment is damaged or metal parts are exposed.

Operator must be careful when voltage exceeds 33Vrms, 46.7Vacrms or 70Vdc.

Such kinds of voltage may cause electric shock.

Do not replace the battery in wet conditions.

Ensure that all test wires are connected to the test ports of tester securely.

When opening the battery cover, make sure that the instrument is turned off.

Please read carefully and understand the manual before using the instrument.

Use the instrument as specified in the manual at any time and store the manual for
further reference.

When the instrument is testing, misoperation may lead to an accident and damage

of equipment.

Caution

Before testing insulation resistance, the circuit under test must be completely

discharged and completely isolated with other power circuits.

In case the test pen is damaged and needs to be replaced, use only the test leads
with the same model or identical electrical specifications.

When the battery indicator indicates that the power runs out, do not use the
instrument. Remove the battery and store the instrument if it is not in use for a long
time.

Do not store or use this instrument in heat, humid, flammable, explosive and strong
electromagnetic field environments.

Safety Symbols 2

The instrument has double insulation or reinforced insulation.

ACV

AC Voltage

Ground

Rated Voltage

III. Technical Specification

Accuracy

(a% reading + digits); calibration per year.

Ambient temperature:

(23 5)

Environmental humidity:

45% to 75%

1. Insulation Resistance Measurement

100V

250V

500V

1000V

Test Range

0.00M ~5.5 G When it is about less than 4.0M buzzer
outputs alarming sounds .

Notes: (100V) 0.00M ~100M

Opened Voltage

DC100V 10%

DC250V 10%

DC500V 10%

DC1000V 10%

Rated Test
Current

When load is
100K , the
rated testing
current is 0.9mA
~1.1mA.

When load is
250K , the
rated testing
current is 0.9mA
~1.1mA.

When load is
500K , the
rated testing
current is 0.9mA
~1.1mA.

When load is 1
M , the rated
testing current is

0.9mA ~1.1mA.

Shorted Current

About less than 1.8mA.

Accuracy

0.00M ~99M 3%+5digits ; 100M ~5.5 G
5%+5digits

2. Voltage Measurement

AC Voltage

Test Range

30V~750V(50Hz/60 Hz)

Resolution

1V

Accuracy

2%+3digits

Display: LCD, 1999 count.

Low Battery Indication: .
Overload Indication: "＞5.5GΩ" for insulation resistance measurement; "OL V" for

voltage measurement.

Autoranging.

Discharge voltage automatically.

Working conditions: 0 ~35 ; relative humidity is 75% or less; altitude: 2000m.

Storage conditions: -20 ~ 60 / relative humidity is 80% or less.

Dimensions: 150mm (L) 100mm (W) 71mm (D).

Power supply: alkaline batteries, 1.5V (5#) 6.

Weight: 0.5kg (with battery).

Accessories: test leads, instruction manual, carrying case, gallus.

Backlight, suitable in dark site.

Red warning light (warning light is on when high voltage outputs).

IV. Tester's Structure (See Diagram 1)

1. EARTH : Insulation resistance input jack.

2. G: Negative voltage input jack.

3. V: positive voltage input jack.

4. LINE: Insulation resistance input jack(high voltage output)

5. LCD screen

P/N:110401104394X

6. Backlight button

7. Data-hold button

8. Insulation resistance test button

9. Functional knob

Diagram 1

V. Functions of Keys and Knobs

1. HOLD: data hold;

2. LIGHT: turn on or off the backlight source;

3. TEST: turn on or off high voltage test;

4. Test AC voltage when function knob points to ACV;

5. Test DC voltage when function knob points to DCV;

6. Test insulation resistance when the function knob points to 100V/250V/500V/1000V
(select the desired output voltage).

VI. Voltage Measurement (See Diagram 2)

To measure AC voltage, do the following:

(1) Insert the red test lead into the V input port and the black test lead into the
G input port.
(2) Place the function knob in the ACV function position to test AC voltage.

Caution

Do not input AC voltage over 750Vrms. It is possible to display a higher voltage but

it may cause damage to the instrument or electric shock.

After all the testing operations, disconnect the test leads and the circuit under test,

and remove the test leads from the instrument input jack.

In case the battery cover is opened, do not conduct any test.

VII. Insulation Resistance Measurement (See Diagram 3)

Diagram 3

Caution

a. When measuring insulation resistance, please
strictly place the two test probes separately.
Do not mix them up.
b. Neither short circuit the two test probes
under high voltage output state nor measure
insulation resistance after high voltage
outputs.
c. In case the battery cover is opened, do
not conduct any test.

2. Continuous Measurement

After function knob is set to one of test voltages 100V/250V/500V/1000V,
press the TEST key, the instrument will be self-locked to measure continuously. The
test voltage will be output and TEST button will light up. With the measurement finished,
press TEST button to unlock and stop the measurement.

Make sure the tested circuit is de-energized before measurement. Do not measure
the insulation of any energized equipment or wire.

Caution

1. Turn the function knob to select one of test voltages 100V/250V/
500V/1000V.

(1) Before testing insulation resistance, the circuit under test must be completely
discharged and completely isolated from power supply circuit.

After the measurement is completed, do not touch the circuit by your hand. The

in the circuit can cause electric shock.

Do not touch test wires when they are disconnected from tested circuit, wait until the
test voltage is completely discharged.
In case the battery cover is opened, do not conduct any test.

VIII. Battery Replacement (See Diagram 4)

Low Voltage Symbol

Battery Voltage

7V or less

Please follow these steps to replace batteries:

(1) In order to avoid the risk of electric shock, firstly turn off the power source before
replacing the battery (i.e. the function knob points at OFF) and remove the test
wires.
(2) Unscrew the screws on the cover of battery compartment and remove the battery
compartment. Replace six batteries.
(3) After the batteries are replaced, ensure to fasten the screws.

Caution

Please do not mix old and new batteries up.
Please note b

When there is need to calibrate or repair the instrument, please have it serviced by
professional personnel or designated service center.

attery's polarity when installing batteries.

Danger

In case the battery cover is opened, do

casing:

To avoid any damage to the instrument, do not submerge it into water.

not conduct any test.

Diagram 4

(2) Insert the red test wire into the LINE input port and the black test wire into
the EARTH input port.
(3) Connect the red and black alligator clip to the circuit under test. The positive voltage
is output from the LINE port.

Diagram 2

capacitance stored

IX.

*END*