Measurement of grounding resistance can be divided into: voltage and current meter method, ratio meter method and bridge method. According to the specific measuring instrument and cloth pole number can be divided into: hand-operated ground resistance meter method, clamp-type ground resistance meter method, voltage ammeter method, three-pole method and four-pole method.
In the measurement of grounding resistance, some factors cause grounding resistance is not accurate: many factors affecting grounding resistance: the size of the grounding pole (length, thickness), shape, number, depth of burial, the surrounding geography (such as flat, ditches, slopes are different), soil moisture, texture and so on. In order to ensure good grounding of the equipment, the use of meters to measure the grounding resistance is essential.
Expanded
Earth resistance is used to measure the state of grounding is an important parameter of good, is the current from the grounding device into the earth and then through the earth to another grounding body or to the distant spread of the resistance encountered, which includes the ground wire and the grounding body of its own resistance, the grounding body and the earth's resistance of the resistance of the contact resistance between the two and the earth's resistance between the earth's resistance, and the two grounding body between the earth's resistance, and the grounding body of the earth's resistance. As well as the resistance of the earth between the two grounding body or grounding body to an infinite distance from the earth resistance.
The size of the grounding resistance is a direct reflection of the good degree of contact between the electrical device and the "ground", but also reflects the size of the grounding network. The concept of grounding resistance only applies to small grounding network; with the increase in the footprint of the grounding network and the reduction of soil resistivity, grounding impedance in the inductive component of the role of more and more large-scale network should be used in the design of grounding impedance.
Baidu Encyclopedia - Grounding Resistance