UNI-T UT528, UT528AU Operating Manual

P/N:110401105431X

REV.3
DATE:2015/07/15

Overview - UT528/528AU

UT528/528AU from.

UT528/528AU Main Unit

UT528/528AU

2

＊ Earth Nulling Block 1 x

＊ Neck strap 1 x

＊ IEC Lead 1 x

＊ Batteries C Type R14 1.5V UM2 6 x

Safety Information

Warnings - Please be aware of the following warnings.

● Before using the unit and test leads inspect both items. Do not use the unit

and test leads if they are damaged or the case is broken or damaged as this

could result in electrical shock.

● Replace the battery as soon as the battery indicator “

”appears. Low

battery levels may produce inaccurate readings.

● Do not use or store the unit in high temperature, humid, flammable or

electromagnetic environments as damage and incorrect readings may result.

● If the tester requires repair or replacement please contact your local service

center.

Declaration of Conformity

Uni-T manufactures this product and declares that this product conforms to the

UT528/528AU

4

8.Warning Symbol

9.Unit Error

10.Readings and Cable Results

11.Leakage Current

12.Double Insulated / Class II Test

13.Class I Test

5

Class I Test Button + Zero/Null Selection

Class II Test Button + 250V Insulation Selection

IEC / Cable Test Button +30m Long Lead Selection

Earth Probe Mains / IEC testing

6

Front Panel Operation

1: Press

+ button to Power on / Power Off.

2: Press button when testing a CLASS I Appliance.

3: Press

button when testing a CLASS II Appliance.

4: Press button when performing Cord / Extension Lead testing.

Advance Features

5: Press and hold the

button this will set the tester into Long Lead Mode.

6. Press and hold the

button to activate 250v insulation test.

You can exit the above advanced features by turning the unit off and back on.

7

Before Testing - Zero the Earth Bond Test Lead!

Plug the earth probe into the rear of the unit and connect it to the earth nulling

adapter. Plug the earth nulling adapter into the front panel earth socket to

complete the circuit.

Press and hold the

button for 5 seconds to zero the earth bond reading

using the earth bond lead and the nulling adapter together in the front test socket.

This will null the earth reading of the test lead and “GOOD” will be displayed once

complete. It is good practice to do this once prior to carrying out testing.

Auto Switch Off

The unit will automatically switch off after approximately 2 minutes if no buttons

are pressed.

Testing a Class 1 Appliance
Plug the appliance into the UT528/528AU panel main socket. Plug the earth test lead into

the socket on the UT528/528AU end panel. Connect the earth crocodile clip to an

8

exposed metal part on the appliance as shown in Diagram 3.

1. Earth / Protective Conductor Test

Press the Class 1 test button

to start the test. The earth resistance test will

begin.

9

If the earth resistance measured is greater than 0.2Ω, the meter will display “×

Rpe”, which is a FAIL. If this occurs, re- check the connections between the pin of

the plug to the bodywork of the appliance and that the crocodile clip is attached to

clean earthed metalwork on the appliance (try attaching the clip to an alternative

piece of metalwork). If all connections are ok the appliance earth connection may

be faulty.

The PASS mark for the earth bond test is 0.2 Ω for a Class 1 appliance.

If the reading is less than 0.2 Ω, the meter will display “√ Rpe”, which is a PASS.

The unit will then automatically attempt to proceed to the insulation test. If it

detects that the appliance’s power switch is in the ON position it will carry out the

insulation test automatically.

If this is not detected the unit will display a flashing

symbol and also “LO

LOAD”. Press the button to proceed to the insulation test.

10

2. Insulation Resistance Test

Before the unit carries out the insulation test it will attempt to check that the

connected appliance’s power switch is in the on position.

If it detects that the appliance switch is in the on position it will automatically

carry out the insulation test.

Please note: most electronic appliances will have electronic ‘on/off’ switches

and even though they are switched on the “Check Connections” message will

still appear.

If the measured resistance is greater than 1MΩ, the meter will display “√

Riso” as a PASS rating.

If the insulation of the appliance is less than 1MΩ, it will display “× Riso” as a

FAIL rating.

Leakage Test

3. After the unit has completed the insulation test it will automatically proceed to

the leakage test.

UT528/528AU

UT528/528AU

12

Class 2 Pre-Check

If the unit detects that the appliance appears to be Class 1 as it detects an

earth connection (possibly as a result of a connected earth clip) it will display

a flashing

symbol and you will be prevented from carrying out the Class

2 test. Test the appliance instead using the Class 1 test.

Insulation Resistance Test – Class 2 Appliance

Before the unit carries out the insulation test the unit will attempt to check to

13

see if the appliance is in the on position.

If it detects that the appliance switch is in the “OFF” position it will wait and

display a flashing

symbol.

If you are sure that the appliance is switched on press the

button again

to start the test.

Please note: most electronic appliances will have electronic ‘on/off’ switches

and even though they are switched on the flashing

will still appear.

If the measured resistance is greater than 2MΩ, the meter will display “√

Riso” as a PASS rating.

If the insulation of the appliance is less than 2MΩ, it will display “× Riso” as a

FAIL rating.

14

Leakage Test

5. After the unit has completed the insulation test it will automatically proceed to

the leakage test.

If the measured leakage is less than 0.25mA, the meter will display “√ ILeak”

as a PASS rating.

If the measured leakage is greater than 0.25mA, it will display “× ILeak” as a

FAIL.

Final Result - Class 2

After the above tests are completed, the meter will indicate whether the

appliance has Passed or Failed the Class 2 test.

Testing an IEC Lead / Extension Lead / Cord Test

Plug the mains lead under test into the socket and the front panel mains socket

on the unit as shown in Diagram 5.

15

To Start the Cord Test Press

1. Earth Bond Test

The unit will carry out an earth bond test in the same manner as a Class 1
appliance. The Pass mark for this test is 0.2 Ω

2. Insulation Test

The unit will then carry out an insulation test as previously discussed in the
manual. The PASS Mark for this test is 2 MΩ.

16

Please note: when testing Surge Protected Extension Leads this test may fail.

This is normal and a result of circuitry within the surge protection device.

3. Polarity Test

The polarity test is the final test to be carried out and will check that the cord

or extension is wired correctly. It will check for open circuit, short circuit or

Line / Neutral reversal.
If the Polarity is correct then the meter will display “√ Good”

If the Polarity test detects a fault, the meter will display “× Cross” or “× Open”

4. Overall Result

After the above measurements are completed, the meter will indicate

whether the measured appliance is compliant with the requirements of

cord testing with “PASS” or “FAIL”

Testing a Surge Protected Extension Lead or Appliance

When you press and hold the Class II appliance button for 5 seconds the tester

17

will go into 250v insulation test mode and the screen will display ‘250 test’.

The insulation test voltage reduces from 500V to 250V to allow for the testing of

surge protected appliances and leads.

Please note: each insulation test carried out in this mode will be at 250V.

To exit this mode turn the tester off and back on.

Testing a Long Cable up to 30 metres

To test a long extension lead or cable ensure the tester is in long lead mode by

pressing and holding the

button for 5 seconds. To exit this mode turn off the

tester.

Checking a Mains Power Supply

The unit comes complete with a built in socket tester which will check to ensure

18

that the socket is wired correctly.

Connect an IEC lead to the mains socket and plug this into the back of the meter

as shown in Diagram 6.

1）If the Live and Neutral in the socket wiring are reversed or there is a fault with
the protective earth connection this is indicated as “LN√, LE×, NE×”.
2）If there is a fault with the neutral connection this is indicated as “LN×, LE√,

NE×”
3）If the mains socket wiring is correct the display will show “LN√, LE √, NE√ ”

0.2ohms

N/A N/A

N/A

Earth Continuity

Pass Limit& Accuracy
Test Current
Test Voltage

200mA minimum
5V nominal

±(5%+2)

±(5%+2)

±(5%+2)

Insulation Resistance

Pass Limit & Accuracy
Test Voltage
Test Current
Test Current

500V

40Vrms,50Hz AC

>1mA 500k
<2mA 1k

<5mA 2k

Leakage Current

Accuracy
Test Voltage
Test Current

Factory Default PASS/Fail Limits

Earth Continuity

Insulation Resistance

Leakage

Class I Class II Cord

UT528 UT528AU UT528 UT528AU UT528 UT528AU

1.0Mohms

0.75mA

1.0 Mohms 1.0 Mohms

2.0 Mohms 2.0 Mohms

0.25mA

1 ohm0.2 ohm

19

Remarks (UT528AU Only):

Earth Continuity:class I ≤0.2Ω, Cord≤1 Ωis PASS.
Insulation Resistance ≥1.0MΩis PASS.
Leakage:class II ≤0.25mA is PASS.