Pro'skit 8PK-ST1520 Digital Earth Resistance Tester User Manual

Overview

The 8PK-ST1520 Digital Earth Resistance Tester is a compact battery-powered meter for checking the resistance of grounding systems and measuring earth voltage. It is suited to electrical inspections at homes, offices, laboratories, hospitals, server rooms, communication sites, towers, and other installations where a reliable earth connection is required.

Earth grounding helps reduce the risk of electric shock, equipment damage, fire, and explosion. It also provides a controlled path for lightning-related surges, static electricity, and other electrical interference.

Specifications

• Model: 8PK-ST1520
• Earth resistance ranges: 0–20 Ω, 0–200 Ω, and 0–2000 Ω
• Earth voltage range: 0–200 V AC at 40–500 Hz
• Resistance accuracy: ±(2% of reading + 2 digits) or ±0.1 Ω, whichever is greater
• Voltage accuracy: ±(1% of reading + 2 digits)
• Resistance resolution: 0.01 Ω on the 20 Ω range, 0.1 Ω on the 200 Ω range, and 1 Ω on the 2000 Ω range
• Measurement method: Constant-current inverter system, approximately 820 Hz and 2 mA
• Display: 3½-digit LCD with 2000-count capacity
• Power: Six 1.5 V AA batteries
• Dimensions: 163 × 100 × 50 mm
• Weight: Approximately 480 g with batteries
• Safety classification: EN61010-1, CAT III 200 V
• Included items: Red 15 m, yellow 10 m, and green 5 m test leads; auxiliary earth bars; heavy-duty case; instruction manual; and batteries

Detailed Description

The tester applies a low measuring current to evaluate the resistance of an earth electrode and its surrounding grounding path. Its approximately 2 mA test current is designed to perform an earth resistance check without unnecessarily tripping earth-leakage breakers in the circuit being tested.

The front panel includes the E, P, and C terminals, an operation indicator, data-hold switch, timer-off button, LCD display, function switch, resistance range switch, push-button control, and timer-on button. The E terminal connects to the earth electrode under test, while P and C connect to auxiliary earth bars during the three-point measurement.

The LCD can show the measured value, a low-battery indicator, a data-hold indicator, and an over-range indication. An unlit operation LED can indicate an open or incorrectly connected test circuit.

Safety

• Read the operating and safety instructions before measuring or servicing the meter.
• Use the instrument only for the procedures and conditions described in this guide. Incorrect use can reduce its built-in protection.
• The tester is intended for indoor use at installation Category III and Pollution Degree 2.
• Use it within an ambient temperature range of 0–40°C, at relative humidity up to 80%, and at altitudes up to 2000 m.
• Inspect the meter, terminals, and test leads before use. Do not proceed if insulation or connections appear damaged.
• The double-insulation symbol indicates protection by double or reinforced insulation. The warning symbol indicates a possible electric-shock hazard, and the caution symbol directs the operator to consult the instructions.
• Before an earth resistance test, measure earth voltage first. The voltage should be below 10 V AC for an accurate resistance result.
• Disconnect the test leads and switch off the instrument before opening the battery compartment.

Setup and Operation

Prepare the Tester

1. Inspect the meter and leads, then confirm that the battery symbol is not displayed.
2. If the display shows B, replace the batteries before measuring.
3. Place the auxiliary earth bars in firm ground and arrange the earth electrode and bars in a straight line.

Measure Earth Voltage

1. Connect the green and yellow test leads to the E and P terminals.
2. Connect the leads to the earth electrode and the auxiliary earth bar used for the voltage check.
3. Set the function switch to the ACV position.
4. Press the push-button and timer-on button at the same time.
5. Read the voltage on the LCD. Confirm that it is below 10 V AC before continuing with the earth resistance test.

Measure Earth Resistance

1. Connect the green lead from the earth electrode under test to the E terminal.
2. Connect the yellow lead from the potential auxiliary earth bar to the P terminal.
3. Connect the red lead from the current auxiliary earth bar to the C terminal.
4. Drive the auxiliary bars into the earth in a straight line with the electrode being tested.
5. Select an appropriate resistance range. Use the lower range when the expected resistance is known to be within that range for better resolution.
6. Set the function switch to the Ω position.
7. Press the push-button and timer-on button simultaneously.
8. Read the resistance value on the LCD.

Indicators and Special Functions

• Data hold: Press the data-hold switch to retain the displayed measurement. The DH symbol confirms that the reading is being held.
• Low battery: The B symbol indicates that the batteries need replacement.
• Over range: A 1 indication means the selected range has been exceeded or the measured value cannot be displayed within that range.
• Operation LED: During a properly connected earth resistance test, the red LED lights to confirm current circulation through the test circuit.
• Auto power-off: When the push-button and timer-on button are pressed together, the tester remains active for approximately 3–6 minutes before switching off automatically.

Troubleshooting

• The display shows 1 during an Ω test: Check that the E, P, and C terminals are connected to their corresponding leads. An open connection or an exceeded range can produce this indication.
• The operation LED remains off: Check the three test leads, auxiliary earth bars, terminal connections, and ground contact. A correctly wired test circuit should illuminate the LED.
• The resistance result appears inaccurate: Measure earth voltage first and confirm that it is below 10 V AC. Also verify that the electrode and auxiliary bars are installed in a straight line and that all connections are secure.
• The B symbol appears: Stop testing and install six new SUM-3/AA batteries.
• The tester switches off: The automatic timer may have elapsed. Return the controls to the off position and select the required function again.

Cleaning and Maintenance

Battery Replacement

1. Disconnect every test lead from the instrument and switch off the power.
2. Use a screwdriver to remove the screw securing the rear cover.
3. Slide off the cover and remove the depleted batteries.
4. Install six new SUM-3/AA batteries, observing the polarity markings.
5. Replace the cover and tighten the screw securely.

Cleaning and Storage

• Wipe the case periodically with a damp cloth and mild detergent.
• Do not use abrasive cleaners or solvents.
• Prevent water from entering the case to avoid electric shock and meter damage.
• If the tester will remain unused for more than 60 days, remove the batteries and store them separately.

Pros & Cons

Pros

• Three resistance ranges cover low-resistance grounding checks through 2000 Ω.
• Dedicated earth voltage measurement helps identify conditions that could affect resistance accuracy.
• Low 2 mA test current reduces the likelihood of tripping earth-leakage protection.
• Data hold, automatic power-off, low-battery indication, and an operation LED support field testing.
• Compact dimensions and a supplied carrying case make the tester practical for service work.

Cons

• The instrument requires a three-point setup with auxiliary earth bars and relatively long test leads.
• The manual specifies indoor use and a maximum CAT III 200 V rating.
• Automatic power-off timing is limited to approximately 3–6 minutes when the timer function is activated.

For routine grounding inspections, the 8PK-ST1520 Digital Earth Resistance Tester combines basic earth voltage testing with three-range earth resistance measurement in a portable format. Accurate results depend on correct E, P, and C wiring, proper auxiliary-bar placement, and confirmation that earth voltage remains below 10 V AC.