MS2302 Digital Earth Resistance Tester

Manufacturer Information

PRECISION MASTECH ENTERPRISES CO.
Unit 8, 21/FL, Yen Sheng Center, 64 Hoi Yuen Road, Kwun Tong, Kowloon, Hong Kong.
Tel: 852 - 23430007 | Fax: 852 - 23436217 | E-mail: info@p-mastech.com

SHENZHEN HUAYI MASTECH CO., LTD.
East Wing, 8/F., Block 4, Saige Science and Technology Industrial Garden, Hua Qiang Bei Rd. Shenzhen, China
Tel: 0755 - 83769588 | Fax: 0755 - 83768150 | E-mail: info@mastech.cn

DONGGUAN HUAYI MASTECH CO., LTD.
Yuliangwei Industrial Area, Qingxi Town, Dongguan, China
Tel: 0769 -87318225 | Fax: 0769 - 87318228

1. Safety

The earth resistance tester (hereinafter referred to as meter) is designed and manufactured in accordance with GB4793.1, EN 61010-1, and EN61010-2-030 Safety Standards. It is regarded as Grade 2 pollution, and the maximum voltage for the meter to probe cannot exceed CAT III 300V.

This manual includes cautions and safety regulations to help avoid personal injury and maintain the meter in good condition. Please read the manual before using the meter and adhere to the operation instructions. Inobservance of the manual may cause personal injury or damage to the meter. Protection impairment may occur if used in a manner not specified by the manufacturer.

Safety Symbols

⚠️ Danger: improper operation will cause severe or fatal injuries.

❗ Warning: improper operation may cause severe or fatal injuries.

❕ Caution: improper operation may cause personal injuries or damage to the meter.

[double-insulation]: Equipment protected throughout by double insulation or reinforced insulation.

CAT III (measurement category III): Applicable to test and measuring circuits connected to the distribution part of the building's low-voltage MAINS installation.

Danger Precautions

• Check if the rotating switch is set to a proper position before measurement.
• Never use the meter in the vicinity of explosive gases, steam, or dust.
• Never connect wires or probes with wet hands or when the surface of the meter is humid.
• Do not touch the testing wires or probes during a measurement.
• Do not open the battery cover when the meter is working.

Warning Precautions

• Never proceed with a measurement under abnormalities, for example, if the housing of the meter has been damaged such that the metal of the meter or wires are exposed.
• Never replace parts of the meter by yourself or modify it. If the meter is damaged, return it to the local dealers for examination or repair.
• Do not replace the batteries when the surface of the meter is humid.
• Be sure to set the switch to “OFF” and disconnect the testing wires before replacing the batteries.

Caution Precautions

• Check if the total length of testing wires is inserted into the port before a measurement.
• Take out the batteries from the cartridge if the meter will not be used or will be stored for a long period.
• Do not expose the meter to sunlight, high temperature, humidity, or dew.
• Clean the meter with neutral solvents or a wet cloth instead of abrasives or organic solvents.
• Store the meter only when it is dry.

Caution: Using this appliance in an environment with a strong radiated radio-frequency electromagnetic field (approximately 3V/m) may influence its measuring accuracy. The measuring result can be strongly deviating from the actual value.

2. Description

The meter is applicable to the testing of the earth resistance of power supply wires, distribution wires inside a room, electrical equipment, or appliances. It can be used in two measurement modes: Bi-poles or Tri-poles, and it can also measure earth voltage.

A large digital LCD and backlights facilitate users in reading information. The meter is capable of storing up to 100 groups of measurement data, which will not be lost even in case of power cuts, allowing users to easily consult historical data. Additionally, the meter can measure maximum, minimum, or average values and perform relative measurements. An auto power-off function is provided.

2.1 Meter Description

(1) Rotating Switch: Used for selection between measurement of earth voltage, measurement of resistance in Bi-pole method, or measurement of resistance in Tri-pole method.

(2) Key of ASP: Used to start or cease the auto power-off function.

(3) Key of LIGHT: Used to turn on or turn off the backlight.

(4) Key of CLEAR: Used to clear away data.

Diagram Description (Tester Front Panel): The front panel of the EARTH RESISTANCE TESTER features an LCD screen displaying measurements and symbols, an analog scale above the LCD, and several control buttons. To the right of the LCD are buttons labeled CLEAR, LIGHT, and APS. Below these are MEMO, MEASURE, MAX/MIN/AVG, ENTER, and REL buttons. A prominent rotary switch is located on the right side, allowing selection between OFF, ~VE (Earth Voltage), 2POLE (Bi-pole method), and 3POLE (Tri-pole method). Input sockets labeled E, P/S, and C/H are located on the lower front panel.

(5) LCD: Used to display the data obtained and different symbols.

LCD Symbols Descriptions:

• TEST: A test is being progressed.
• >LIMIT: Limit has been exceeded.
• MAX: Maximum value.
• MIN: Minimum value.
• AVG: Average value.
• REL: Relative measurement.
• READ: Data reading mode.
• MEMO: Data is being put into a memory.
• USED: There are data in memories.
• 2POLE: Bi-pole method is being used for resistance measurement.
• 3POLE: Tri-pole method is being used for resistance measurement.
• V: Volt (voltage).
• kΩ: Ohm (resistance).
• [auto-off symbol]: Auto power-off has been started (symbol ?).
• [low battery symbol]: Battery is low (symbol ?).
• H, S, E: For socket identification.
• 〰️: Alternating current.
• ⚠️: For warnings and cautions.

Meter Components and Sockets:

(6) Key of READ: Used to read the data obtained.

(7) Key of MEMO: Used to store the data obtained.

(8) Key of Measure: Used to start or cease a measurement of resistance.

(9) Key of ▲: Used to select a memory for storage of data obtained.

(10) Key of MAX/MIN/AVG: Used to switch between the measurement of maximum, minimum, and average.

(11) Key of ENTER: Used to confirm a storage or reading of data.

(12) REL: Used to select relative measurement.

(13) Key of ▼: Used to select a memory for storage of data obtained.

(14) E socket: Used to connect with the grounding pole.

(15) P/S socket: Used to connect with the auxiliary grounding pole.

(16) C/H socket: Used to connect with the auxiliary grounding pole.

3. Specifications

Operating Environment:

• Air temperature: 23 ± 5°C
• Relative humidity: <75%

3.1 Range Specifications

3.2 Measurement Method

Constant Current Conversion is used for the measurement of earth resistance, with a testing current frequency of about 800Hz and a magnitude of about 3mA. Average rectification is used for the measurement of earth voltage.

3.3 Temperature and Humidity for Measurement

0~40℃, relative humidity under 85%

3.4 Temperature and Humidity for Keeping the Meter

-10~50°C, relative humidity under 85%

3.5 Battery

Six 1.5V AA batteries

3.6 Volume

330 X 125 X 265 (mm)

3.7 Weight

3.45kg

3.8 Supplied Accessories

3 test leads (one 15-meter-long red lead, one 10-meter-long green lead, and one 5-meter-long black lead), 2 auxiliary earth bars.

4. Operation Instructions

Danger during Operation

• In measurement of earth voltage, do not apply voltage above AC220V on the measurement port.
• In measurement of earth resistance, there will be a potential of about 50 V between port E and S or between ports E and C. Therefore, protect yourself from electrical shock.

Before using the meter, check the battery level by turning on the meter. If the [low battery symbol] ? appears on the display, replace the batteries by following the steps in Chapter "Replacement of the batteries".

4.1 Measurement of Earth Voltage

Rotate the switch to ~VE position, insert the end of the meter cable into sockets E and S. Connect the other end of the meter cable to either end of the voltage source or resistance load in parallel. If voltage exists, it will be displayed on the LCD.

4.2 How to Measure Earth Resistance by Bi-pole Method

In this method, existing earth poles, such as buried metals (metal water pipes, etc.), common earth of the commercial power supply, or lightning rods of high buildings, are used as the auxiliary pole instead of auxiliary earth bars.

Diagram Description (Bi-pole Test Connection): The diagram shows the EARTH RESISTANCE TESTER connected via leads. One lead connects to the 'E' socket on the tester and to an earth electrode driven into the ground. Another lead connects to the 'P' socket (or 'S' socket) on the tester and to the grounding point of the object under test (e.g., a building's grounding system). The diagram illustrates the tester, an earth electrode labeled 'E', and a house with grounding points labeled 'P' and 're' (representing the object being measured).

(2) Measurement of Earth Voltage: Earth voltage measurement should be done before earth resistance measurement to check the amount of earth voltage. A voltage greater than 10V may cause larger errors in the earth resistance measurement. In such cases, disconnect the measured object from the power supply and wait until the earth voltage drops before performing another measurement.

(3) Measurement of Earth Resistance: Rotate the switch to the 2 POLE position. Press the MEASURE key to start the measurement; the key LED will turn on and glitter. When the measurement ends automatically, a buzzer will sound, the key LED will go off, and the data will be held automatically.

Attention: A display of >LIMIT4000Ω on the LCD warns that the auxiliary earth resistance of the auxiliary earth rods is too high for current to flow across the meter. Check if the test leads have become loose. The amount of earth resistance of the auxiliary earth rods can affect the reading.

(4) Value Measured: In the Bi-pole method, the measured value (Re) equals the sum of the earth resistance of the earth rods (re) and the real earth resistance of the object measured (RX). Therefore, RX = Re - re, meaning the real resistance of the object measured equals Re minus re.

4.3 Measurement of the Resistance by Tri-pole Method

The Potential Drop Method is used by the meter for earth resistance measurement. Specifically, RX (the earth resistance) is determined by first allowing the rated current (I) to flow between E (the object measured, i.e., the earth rods) and C (the current pole), then measuring V (the potential difference between E and P, the voltage pole).

(1) Connect the test leads to the meter as follows:

Diagram Description (Tri-pole Test Connection): The diagram illustrates the EARTH RESISTANCE TESTER connected to three points in the ground. The 'E' socket on the tester is connected to the first earth rod (labeled 'E'). The 'P' socket is connected to a second auxiliary earth rod (labeled 'P'), and the 'C' socket is connected to a third auxiliary earth rod (labeled 'C'). These rods are driven into the ground at distances of 5 to 10 meters apart in a straight line.

Drive the Auxiliary Earth Bars P and C deep into the ground in a straight line, ensuring they are between 5 and 10 meters apart. Connect the ends of the test leads (black, red, and green) from ports E, P, and C, respectively, to the object measured, auxiliary earth rod P, and auxiliary earth C.

Attention: Drive the auxiliary rods where the earth is damp. If only dry earth (clay, sand, or gravel) is available, spray some water onto them to keep them damp. If the measurement is performed on a concrete floor, place the auxiliary earth rods horizontally and spray some water onto them or cover them with a damp cloth.

(2) Measurement of Earth Voltage: Earth voltage measurement should be done before earth resistance measurement to check the amount of earth voltage. A voltage greater than 10V may cause larger errors in the earth resistance measurement. In such cases, disconnect the measured object from the power supply and wait until the earth voltage drops before performing another measurement.

(3) Measurement of Earth Resistance: Rotate the switch to the 3 POL position. Press the MEASURE key to start the measurement; the key LED will turn on and glitter. When the measurement ends automatically, a buzzer will sound, the key LED will go off, and the data will be held automatically.

Attention: A display of >LIMIT4000Ω on the LCD warns that the auxiliary earth resistance of the auxiliary earth rods is too high for current to flow across the meter. Check if the test leads have become loose. In a measurement, test leads twisted together or contacting each other will cause errors. Ensure that the test leads are separate during measurement. Excessive auxiliary earth resistance will also bring unacceptable error; therefore, bury auxiliary earth rods P and C deeply in wet sites and ensure good connection at each joint.

4.4 Data Storage

The meter is capable of storing up to 100 groups of measurement data, which will not be lost even in case of power cuts.

(1) When the meter is standing by, press MEMO to call the display for data storage. The word “MEMO” will glitter at the lower right corner of the LCD. If the existing memory has been used for storage of other data, “USED” will be shown on the LCD when pressing MEMO to exit data storage.

(2) Press “ENTER” briefly to switch between memory positions (1-bit and 10-bit). The memory position can be scanned by pressing ▼ or ▲.

(3) Press “ENTER” for 2 seconds to store a group of data in a memory. If data was previously stored in that memory location, the current data will overwrite the previous data.

4.5 Data Reading

The data reading function allows you to check historical measurements stored in the meter.

(1) When the meter is standing by, press MEMO to call the display for data storage, with “MEMO” glittering at the lower right corner of the LCD. If the existing memory has been used for storage of other data, “USED” will be shown on the LCD when pressing MEMO to exit data storage.

(2) Press “ENTER” briefly to switch between memory positions (1-bit and 10-bit). The memory position can be scanned by pressing ▼ or ▲.

(3) Press “ENTER” for 2 seconds to read a group of data from a memory if data was previously stored there.

4.6 REL - Relative Measurement

Relative measurement is accessible only when the tester is used for measurement of earth resistance. Press REL to switch between relative measurement mode and normal mode.

(1) In relative measurement mode, the symbol “REL” is shown on the LCD, and the existing reading is stored in memory for future reference. In subsequent relative measurements, the LCD displays the difference between the input value and the reference value (i.e., displayed value = input value - reference value).

(2) Under normal earth resistance measurement, it is not allowed to enter REL mode while the measurement is progressing.

(3) It is not allowed to enter REL mode when data is being read or stored.

(4) It is not allowed to enter REL mode when the existing reading exceeds the limit.

4.7 MAX/MIN/AVG Measurement

Press the MAX/MIN/AVG key to switch between modes for maximum, minimum, average, and normal measurements. A corresponding symbol is shown on the LCD for each mode.

(1) When MAX is selected, the LCD shows the maximum of all the data.

(2) When MIN is selected, the LCD shows the minimum of all the data.

(3) When AVG is selected, the LCD shows the average of all the data.

4.8 Data Deletion

Data can be deleted when READ or MEMO is pressed. Press CLEAR briefly to delete the data stored in the current position. Press and hold CLEAR to delete all stored data.

4.9 Backlight

Press LIGHT to turn on or turn off the backlight. It will automatically turn off 15 seconds after being turned on.

4.10 Auto Off

Press ASP to start or cease Auto-off. The symbol ? on the LCD indicates that the Auto-off function has started. The disappearance of the symbol means the function has been ceased. If no operation is performed within 15 minutes after Auto-off is on, the meter enters sleeping status, and the buzzer will sound to remind you. Press any key to wake the meter up. Be sure to set the switch to “OFF” if the meter will not be used for a long time.

5. Battery Replacement

Danger during Battery Replacement

• Never replace the batteries while the meter is damp.
• Never replace the batteries while the meter is being used. Switch off the meter and disconnect the test leads and earth rods before replacement to avoid electrical shock.

Attention during Battery Replacement

• Never mingle new batteries with old ones.
• Pay attention to the polarity of the batteries during replacement.

Diagram Description (Battery Compartment): The diagram shows the opened battery compartment of the tester. The cover is detached, revealing the interior housing for six 1.5V AA batteries arranged in two rows of three.

Replacement Steps:

1. Unscrew the battery cover and remove it.
2. Replace the old batteries with new ones, paying attention to their polarities.
3. Put back the battery cover and screw it securely.