VICTOR 4105A Digital Grounding Resistance Meter

I. Overview

The VICTOR 4105A is a professional instrument designed for measuring grounding resistance of electrical equipment. It represents an advancement over traditional ground resistance meters, featuring improved circuitry, structure, and technology. This meter offers a comprehensive set of functions, higher accuracy, and a more convenient user experience, all within a durable, dust-and-moisture-proof design suitable for field operations.

It is used to measure the grounding resistance of various systems, including power systems, electrical equipment, and lightning protection equipment. Additionally, it can measure AC voltage.

II. Open-case Inspection

Upon opening the package, verify that all the following items are present:

• Grounding resistance meter: 1 set
• Canvas bag: 1 Pcs
• Ground drill rod: 2 Pcs
• Auxiliary testing wire: 1 set (includes a 15-meter red wire, a 10-meter yellow wire, and a 5-meter green wire)
• Simple testing wire: 1 set (includes a 1.6-meter red wire and a 1.6-meter green wire)
• 5# alkaline battery (LR 6 AA) (1.5V): 8 Pcs
• Instruction manual: 1 copy
• Strap: 1 piece

III. Safety Precautions

Warning: The warnings and safety requirements stated in this manual must be strictly observed to ensure safety. Please read the operating instructions carefully before using this meter.

• Do not use the meter or measuring wire with damaged surfaces.
• To prevent electric shock, do not touch conductors with a voltage higher than DC 60V or AC36V RMS, as these voltages meet the standard for electric shock.
• Before measuring resistance, ensure the tester is completely isolated from the power circuit to guarantee accurate readings and personal safety.
• Do not store the meter at high temperatures or expose it to direct sunlight, as this can affect the LCD's service life.
• When the low battery symbol ? appears on the display, the battery needs to be replaced. For long-term storage, remove batteries to prevent damage from leakage.
• Exercise special care when measuring bare wires.
• The battery will be disconnected when an external adapter is used. The battery cannot be recharged in this mode. Ensure the correct power supply mode is selected.
• Grounding Resistance Testing Requirements:
  • AC grounding resistance: Not greater than 4 Ω.
  • Safety grounding resistance: Not greater than 4 Ω.
  • DC grounding resistance: Determined according to specific requirements of the computer system.
  • Lightning protection grounding resistance: Not greater than 10 Ω.
  • Joint grounding of shielding system: Not greater than 1 Ω.

The following table summarizes symbols and their meanings:

IV. Work Principle

The measuring principle of grounding resistance is based on Ohm's Law. The process involves inserting four electrodes (E1, P1, P2, E2) into the ground at a depth of approximately 20 meters apart. AC signals are applied to electrodes E1 and E2. The current flowing through the earth is measured by an ammeter connected to electrodes P1 and P2. If the current remains constant, the measured voltage is proportional to the earth resistance. The displayed value is influenced by swamping resistance, necessitating the selection of an appropriate measurement range for optimal readings. The AC signal is generated by a built-in converter.

Diagram Description: A schematic shows four electrodes (E1, P1, P2, E2) inserted into the ground. E1 and E2 are connected via a wavy line, representing the AC signal path. P1 and P2 are connected in series with a measuring device (ammeter), indicating current measurement. The ground is depicted as a horizontal line with hatching, and the electrodes penetrate this line.

V. Appearance Description

The instrument features a clear display and intuitive controls:

• 1, 2, 3, and 4: Range selector switch for 20 Ω, 200 Ω, 2000 Ω, and EARTH VOLTAGE measurements.
• 5: Digital holding switch (HOLD) to retain the displayed measurement.
• 6: Power Switch (POWER) for turning the device on/off.
• 7: Testing indicator light, which illuminates during testing if the connection is correct.
• 8: Test button to initiate a measurement.
• 9: LCD display showing measurement data and unit symbols.
• 10: Instrument model identifier.
• 11: P port: Potential pole connection.
• 12: C port: Current pole connection.
• 13: E port: Grounding pole connection.
• 14: ACV port: AC Voltage measurement connection.
• 15: Power adapter jack for external power input.

VI. Technical Characteristics

1. General Features

• Display: 84.8 × 59.8mm window-type LCD display with a maximum displayed value of "1999".
• Over-range indication: The first digit displays "1" when the upper limit is exceeded.
• Power supply: 5# alkaline batteries LR6 (1.5V) x 8. An optional adapter can also be connected. An under-voltage indication function is provided.
• Power consumption: Power consumption during no-load testing is ≤ 800mW.
• Operating environment: 0℃ to 40℃. Relative humidity: 30% to 85%RH.
• Overall dimensions: 175(L) × 110(W) × 70(D) mm.
• Weight: Approximately 680g (including batteries).

2. Technical Data: Grounding Resistance

Grounding Voltage (50Hz - 200Hz)

VII. Resistance Measurement Method

7-1. Battery Voltage Inspection

After startup, if the battery symbol ? is not indicated on the display, the current power is sufficient. If the display flashes or shows the battery symbol, replace the battery according to the instructions in Chapter VIII.

7-2. Testing Wire Connection

Ensure the plug of the testing lead is completely inserted into the test side. Loose connections can lead to errors in measurement results.

7-3 Test Method

Danger: An AC voltage of up to 50V may occur between E-C or E-P terminals during grounding resistance measurement. Do not touch test leads to avoid electric shock.

7-3-1 Conventional Measurement Method

1) Test Lead Connection

Insert the auxiliary grounding rods P and C vertically into the ground at a point 5-10 meters from the grounded object. Connect the green wire to the instrument's E terminal, the yellow wire to the P terminal, and the red wire to the C terminal.

Note: Please insert the auxiliary grounding rod into the ground with high water content. If the rod is to be inserted into dry ground, silica-containing ground, or ground with gravels, the ground should be wetted with water to ensure the grounding rod can be inserted into wet ground. In case of cement ground, apply water to the horizontally placed grounding rod and cover it with a wet towel before insertion.

Diagram Description: A schematic shows four electrodes (E1, P1, P2, E2) inserted into the ground. E1 and E2 are connected via a wavy line, representing the AC signal path. P1 and P2 are connected in series with a measuring device (ammeter), indicating current measurement. The ground is depicted as a horizontal line with hatching, and the electrodes penetrate this line.

2) Grounding Voltage Measurement

Set the range selector switch to the Earth Voltage position. If a voltage value is displayed, it indicates grounding voltage in the system. Check if the voltage value is lower than 10V. If the value is above 10V, an error in the measured grounding resistance value may occur. In this case, turn off the power supply of the tested grounding device and carry out the measurement after the grounding voltage drops.

3) Grounding Resistance Measurement

Start from the 2000 Ω range. Press the "TEST" key. The backlight will illuminate, indicating that a test is in progress. If the displayed value is too small, change the range to 200 Ω or 20 Ω. The displayed value under these circumstances is the measured value of grounding resistance. Turn off the power switch after the test is completed to save power.

Note: The symbol ? indicates that the grounding impedance of auxiliary grounding rod C is too high. Check if the connection is loose, or increase the humidity of the ground around the auxiliary grounding rod to reduce ground impedance.

Note: Ensure that the wires are not entwined. If testing wires are entwined, mutual induction may occur during testing, leading to a "false connection" condition and affecting readings. If the auxiliary grounding impedance is too strong, a display error may occur. Ensure auxiliary grounding rods P and C are inserted into wet ground, and all connection parts are in full contact.

7-3-2. Simple Grounding Resistance Measurement Method

This method is suitable for places where insertion of an auxiliary grounding rod is not feasible. It utilizes a grounding electrode such as a metal water pipe, a commercial electric power system common grounding terminal, or a structure grounding terminal that has extremely weak grounding impedance, instead of auxiliary grounding rods C and P. Use simple test leads for this method.

1) Test Lead Connection

Connect the leads according to the figure. Note: If the simple test leads supplied with the instrument are not used, make a short circuit for terminals C and P.

Diagram Description: Similar to the conventional method diagram, showing the meter and electrodes E, P, C in the ground. Colored wires (Green to E, Yellow to P, Red to C) connect them. Distances of 5-10m are indicated.

2) Grounding Voltage Measurement

Set the range selector switch to the Earth Voltage position. If a voltage value is displayed, it indicates grounding voltage in the system. Check if the voltage value is lower than 10V. If the value is above 10V, an error in the measured grounding resistance value may occur. In this case, turn off the power supply of the tested grounding device and carry out the measurement after the grounding voltage drops.

3) Grounding Resistance Measurement

Start from the 2000 Ω level. Press the "TEST" button. The backlight illuminates to indicate a test is in progress. If the displayed value is too small, switch to the 200 Ω or 20 Ω level. The value displayed in this case is the grounding resistance value. Turn off the power switch after the test is completed to save power.

Note: The measured current is approximately 2mA. The circuit breaker will not be actuated, even if a leakage circuit breaker is connected.

The real grounding resistance value RX is subject to the following formula:

RX = RE - re

Where:

• re: grounding resistance of common ground terminal of commercial power system, etc.
• Re: instrument grounding resistance reading.

VIII. Battery Installation

When the battery power is low, a ? symbol will appear on the screen, indicating the battery needs replacement. To replace the batteries:

1. Turn off the instrument and take out the old batteries.
2. Unscrew the screws on the battery door using a screwdriver.
3. Open the battery door.
4. Load new batteries, paying attention to the polarity (+/-).
5. Close the battery cover and tighten the screws.

Diagram Description: Two steps are illustrated. Step I shows a hand using a screwdriver to remove screws from the battery cover. Step II shows the battery compartment with batteries being inserted.

IX. Troubleshooting

If your meter is not operating properly, the following methods can help resolve general problems. If faults persist, please contact the service center or distributor.