UNI-T UT522 Digital Earth Tester

1. Safety Information

This operation manual includes safety information related to the operation of the tester. Please read them carefully before using the tester.

• Please read and understand the operating manual before using the Tester.
• Please keep the Operating Manual properly for future use.
• Use the Tester as specified in the Operating Manual.
• Please understand in detail the Safety Information section of the manual.
• Strictly follow the Safety Information, otherwise it may cause personal injury or damage to the Tester.

The safety sign "▲" has 3 meanings in this manual; the user has to pay attention to this sign "▲" during operation.

▲ Danger: Identifies conditions and actions that most likely pose severe or fatal hazard(s) to the users.

▲ Warning: Identifies conditions and actions that may pose severe or fatal hazard(s) to the users.

▲ Caution: Identifies conditions and actions that will pose hazard(s) or damage the Tester.

▲ Danger

• Do not use the Tester around explosive environments, which may cause fire and explosion.
• Do not make any connections when the Tester is wet or the operator's hands are wet.
• Do not apply any voltage beyond the rating or specified range of the Tester.
• Do not open battery compartment while testing.

▲ Warning

• Do not use the Tester if it is damaged or a metal part is exposed.
• Do not disassemble the tester randomly. If it needs repair, please contact after-sales services or authorized agents.
• Do not change the battery or open the battery compartment when the Tester is wet. Clean it with a dry soft cloth first.
• Make sure the Tester is turned off when changing the battery or opening the battery compartment.

▲ Caution

• Ensure the test lead is inserted into the corresponding port before measurement.
• Take the battery out from the Tester if it is not used for a long time.
• Do not expose the Tester to extreme temperatures and wet environments.
• A soft cloth and mild detergent should be used to clean the surface of the Tester. No abrasive and solvent should be used.
• Dry the tester before storing if it is wet.

Electrical Symbols used on the Tester or in the manual:

• ▲: Danger, Warning, Caution
• ~: AC
• ■■: Double or reinforced insulation
• ⌂: Grounding
• CE: Conforms to Standards of European Union

2. Features

The Tester is designed with an intelligent micro-controller chip to maintain high accuracy and reliability. It can measure earth resistance of earth ground devices for electric power installations, electrical appliances, lightning protection systems, etc., and also measure earth voltage. (It is highly recommended not to use the Tester under severe outdoor environments such as raining or thunder).

• Backlight LCD
• Battery Check
• Data Hold & Data Storage (up to 20 sets)
• Auto Power Off
• Offers Precision Three-Wire & Simple Two-Wire Measurements
• "- - - - Ω" Indication for Bad Connection to C or E Terminal When Measuring Earth Ground Resistance
• "OL" Overloaded Indication
• Double-or Reinforced-Insulated Structural Design

3. Technical Specifications

Measuring range and accuracy (under 20°C ±5°C & ≤75%RH):

Compliances:

• IEC 61010-1 CATIII 600V; Pollution Degree 2
• IEC 61557-1, 5
• IEC 61010-2-31

Measure modes:

• Earth Voltage measurement: average respond
• Earth Resistance measurement: test signal frequency: around 820Hz, current: around 3.2mA at 400Ω range.

Measuring scope (Max. deviation: ±30%):

• 40Ω Range: 5.00Ω ~40.00Ω
• 400Ω Range: 40.0Ω ~400.0Ω
• 4000Ω Range: 400Ω ~4000Ω

Working condition:

• Temperature: 5°C ~ 40°C
• Relative humidity: ≤80%RH (no fog)
• Altitude: ≤2000 m

Storage condition:

• Temperature: -20°C ~ 60°C
• Relative humidity: ≤75%RH (no fog)

Power: [1.5V Alkaline Battery (AA)*6]

Overload protection:

• Earth resistance ranges: 200 Vac (10 seconds)
• Earth voltage ranges: 600 Vac (30 seconds)

Insulation impedance: >20MΩ between measure circuits and the casing.

Product size: 160mm x 70.5mm x 100mm.

Product Weight: around 560g.

Accessories:

• Green test lead (5m): 1 pc
• Yellow test lead (10m): 1 pc
• Red test lead (20m): 1 pc
• Auxiliary earth stakes: 2 pcs
• Simple test leads with alligator clips: 1 set
• 1.5V Alkaline Battery (AA): 6 pcs
• Carrying bag: 1 set
• English manual: 1 pc

4. Tester Structure & Accessories (Figure 1)

Figure 1:

A diagram shows the UNI-T UT522 Digital Earth Tester with labeled parts:

• LCD Display
• LIGHT/LOAD button
• HOLD/SAVE button
• TEST button
• Rotary switch
• Input terminals
• Standard 3-Wires test leads
• Simple 2-Wires test leads
• Auxiliary earth stakes

5. Preparation before measurement

5.1 Battery Check:

Set the rotary switch to earth voltage or earth ground resistance ranges. If "▲" shows, it indicates the battery is very low and needs to be replaced timely, otherwise the Tester may be unable to work normally.

Battery sign status:

• ▲: Battery Voltage ≥8.2V
• ▲: 7.8V~8.2V
• ▲: 7.4V~7.8V
• ▲: 7.0V~7.4V
• ▲: < 7V

5.2 Test Leads Connection

Make sure all the test leads are firmly connected to the Tester input terminals; poor connection will affect measurement accuracy.

6. Making Measurements

▲ Warning

The voltage up to 50Vac will be present between E and C input terminals during earth ground resistance measurement. To avoid any electric shock, do not touch exposed metal parts of test leads and auxiliary earth stakes.

6.1 Precision Measurement (with use of standard test leads):

1. Insert P and C earth stakes deep into the soil, make sure the earth stakes and tested object are in a straight line and at a distance of 5m~10m from each other. See Figure 2 for the wire connections.

Figure 2: A diagram illustrates the connection of the tester with auxiliary earth stakes and the earth electrode under test, showing red, yellow, and green test leads connecting to the tester and stakes. The diagram indicates a distance of 5m~10m between the stakes and the tested electrode.

Note: Ensure the earth stakes are inserted into damp soil. If the soil is dry, fill in enough water. Stony or sandy soils also need to be dampened before testing. If the test sites are covered with concrete in the city area, making it impossible to insert the ground stakes, you can place two 25cm x 25cm steel plates (or the auxiliary stakes) horizontally on the concrete, cover them with towels damped sufficiently with enough water. Then, measuring electrodes are produced, and under general circumstances, the measurement can begin.

E: earth electrode
C: auxiliary electrode
P: potential electrode

6.2 Simple Measurement (with use of simple test leads):

This method is applied when auxiliary stakes are impossible to use. It uses an exposed object with low earth resistance as one electrode, such as a metal water slot, pipe, common earth of power wiring, earth ground terminal of buildings, etc. (using E and P&C terminals).

See Figure 3 for wire connection:

Figure 3: A diagram shows the simple measurement setup. The tester is connected to the object under test and a reference earthed electrode (e.g., metal water slot, pipe). The red lead connects to E, and the green lead connects to P&C. The diagram indicates that P and C have already been connected together.

▲ Danger

Please take extreme caution about electric shock when using the earth ground terminal of a commercial power system as a reference test point.

b. Measuring Earth Voltage:

1. Set the rotary switch to EARTH VOLTAGE. The LCD shows the Tester enters into earth voltage test status.
2. Insert test leads into V and E terminals and then connect them to tested points. (Do not make any connection to other terminals).
3. The measured earth voltage shows on LCD (No need to press TEST button). If the measured voltage is > 10V, please switch off all related electrical equipment and wait until this voltage decreases before you make any earth resistance measurement, otherwise it may affect the accuracy of earth resistance measurement.

▲ Warning:

Only V and E input terminals are used for earth voltage measurement. Do not make any connection to C and P terminals. Otherwise, it will cause danger and damage the Tester.

c. Measuring Earth Ground Resistance:

1. Set the rotary switch to earth ground resistance 4000Ω range.
2. Press the "TEST" button. The button will be illuminated, indicating the instrument is under measurement status. The LCD shows the measured earth resistance value.
3. If the measured earth resistance is < 400Ω, turn the rotary switch to 400Ω range. If it is < 40Ω, turn the rotary switch to 40Ω range. Alternatively, you can select earth resistance ranges in any order you like. However, to obtain an accurate value, make sure you have selected the best range for your measurement.

Caution:

• If the C or E input terminal is not well contacted, or the auxiliary earth resistance or measured earth ground resistance is too large, or input terminals are opened (> 14kΩ at 400Ω range), the LCD will show "- - - - Ω". Please check if the test leads are firmly connected, if the soil is too dry, or if the auxiliary earth stake has been properly inserted into the earth.
• When the measured earth resistance is out of range, and it is < 14kΩ at 400Ω range, < 26kΩ at 4000Ω range, or < 78kΩ at 40000Ω range, the LCD will show the "OL" icon (Overloaded).
• The reading may be affected if auxiliary stakes are bent or in contact with other objects. So please clean the earth stakes before connecting the test leads, otherwise it may cause deviations to the readings if the auxiliary stake has a large resistance.

d. Auto Power Off:

The Tester will automatically switch off to conserve energy after the buttons and rotary switch remain inactive for 10 minutes (except under earth resistance test status).

e. Backlight:

When making measurements in dimly lit sites, press the "Light/Load" button to turn on the backlight, and its icon indicates on LCD accordingly. Press again to turn off the backlight.

f. Data Hold:

During the measurement, gently press "Hold/Save" to freeze the measured value, indicated by the HOLD icon on LCD. Press again to disable the function.

g. Data Storage:

1. Save Data: Long press the "Hold/Save" button for 2 seconds to enable Data Save function and meanwhile save the data accordingly. Then, gently press the button again to save the second set of data, circulating so on and so forth. To cancel the function, long press "Hold/Save" for 2s to exit.
2. View Data: Long press "Light/Load" for 2s to recall NO.01 data, then gently press the button to recall NO.02 data, up to 20 sets of data. To return to the previous set, gently press the "Hold/Save" button. (Under this status, "Hold/Save" and "Light/Load" (gently press) buttons are used as Up and Down buttons). To exit the function, long press "Light/Load" button for 2s.

3. Clear Data

Press "Hold/Save" button and "Light/Load" button simultaneously, then switch on the Tester. The LCD display will show "C L.". Meanwhile, all the data in the memory will be deleted (no matter whether the memory is full or not).

7. Maintenance & Repair

7.1 Maintenance

7.1.1 Replacing the Battery (See Figure 4)

Please replace the battery timely when the low battery indicator shows. Follow the steps as below:

Figure 4: A diagram shows the battery compartment of the tester. It indicates the location of the battery compartment and the need to release a screw.

1. Switch off the Tester and remove all the test leads.
2. Release the screw in the bottom part and open the battery compartment.
3. Replace all old batteries (6) with new batteries.
4. After replacing the battery, rejoin the battery compartment and screw it firmly. Remove all the batteries if not used for a long time to avoid leakage and corrosion in the battery compartment.

7.1.2 Cleaning the Tester

A soft cloth and mild detergent should be used to clean the surface of the Tester. No solvent or alcohol is allowed, as it may damage the display.

7.1.3 Protection from Moisture

Ensure the tester is dry before storing if it is wet.

7.2 Repair

7.2.1 Contact after-sales service department or agents when the following incidents occur:

• The Tester is damaged.
• LCD display is abnormal.
• Unreasonable deviation during normal use.
• Buttons do not function properly.

7.2.2 When the Tester needs repair, please have it serviced by qualified professional personnel or an authorized service center.