This section provides overview, applications, and principles of earth resistivity meters. Also, please take a look at the list of 10 earth resistivity meter manufacturers and their company rankings.
An earth resistivity meter is an instrument that measures the electrical resistance between electrical equipment and the earth. It is one of the most familiar devices for electricians and electrical practitioners. Grounding refers to the connection between the earth and electrical equipment.
When an abnormality occurs in electrical equipment, a person touching the equipment may receive an electric shock. By grounding electrical equipment, it is possible to release the electric current to the earth in the event of an abnormality. The safety of electrical equipment needs to be securely grounded.
The measurement principle of the earth resistivity meter is Ohm's law. An alternating voltage is applied between the pole to be measured and the pole to be compared by the earth resistivity meter. After the voltage is applied, the current flowing between the two poles is measured, and the ground resistance is calculated by dividing the current by the applied voltage.
Although the above method can be used to calculate the ground resistance, this method measures the ground resistance of the target pole plus the pole to be compared. Therefore, a separate grounding pole dedicated to voltage measurement is provided to measure the grounding resistance of the target pole only.
If a DC voltage is used in the earth resistivity meter, electrolysis occurs, and the current value cannot be determined. Therefore, AC power is often used in earth resistivity meters. Since AC power supplies are affected by lead capacitance at higher frequencies, power supplies with a frequency of 1 kHz or lower are used.
There are three types of earth resistivity meters: analog display type, digital display type, and type that reads the scale value when the scale needle displays "0". As an example, the procedure for using an analog display type is shown below.
The earth resistivity meter comes with a metal rod called an auxiliary grounding pole, which is embedded in the ground when measuring grounding resistance.
The procedure is basically the same for other types of installation resistance testers as for the analog display method, but the "read the scale value when the scale needle shows "0" method reads the scale value when the scale needle shows "0". The green, red, and yellow wires attached to the earth resistivity meter are used to connect each grounding pole to the terminals on the body of the earth resistivity meter.
In addition to these, there are also clamp-type earth resistivity meters that measure grounding resistance by clamping the ground wire. It is easy to measure because there is no need to bury the auxiliary pole in the ground, but it can be used only in the case of multiple grounding.
Insulation testers and earth resistivity meters differ in measurement items and measurement objects. Insulation testers measure an electric circuit to check insulation, whereas earth resistivity meters measure a grounding pole to check ground resistance.
Insulation testers apply DC voltage, while earth resistivity meters apply AC voltage. Although the appearance and names of the devices are similar, it is essential to understand their differences in advance.
*Including some distributors, etc.
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