|Comparison of traditional earth resistance tester and Clamp on earth resistance tester|
Ground resistance tester measurement becomes more extensive and important, the current measuring methods of grounding resistance mainly has two kinds: 1,the traditional grounding resistance meter; 2,new clamp earth resistance tester. Below the comparison of the two methods of grounding resistance measurement.
1 operation method
The grounding resistance of the grounding wire must be tripping and working with auxiliary grounding pin. The measured grounding electrode is separated from the grounding system, and should be the voltage and current electrode according to the provisions of the distance in o the soil so that the auxiliary electrode can be measured. The operation is more complicated and laborious.
The clamp on earth resistance tester is a non-contact measurement meter, vise the jaw on the grounding wires, the LCD screen will show the grounding resistance. Operation is very simple.
2 measurement accuracy
The accuracy of traditional grounding resistance tester depends on the position of the auxiliary electrodes and the relative position between them and grounding. If the position of the auxiliary electrode is limited, it is not consistent with the calculated value. For the same grounding, the auxiliary electrode in different positions, may make the measurements have a certain degree of dispersion. And this dispersion will reduce the credibility of the measurement results.
MEWOI Clamp on earth resistance tester without auxiliary electrode, there is no pole error, for repeated tests, the results are great.
3 test environment
Traditional grounding resistance meter adopts voltage - current method, must score two grounding auxiliary electrodes in a relative position, so the test point must near the soil.
MEWOI Clamp on resistance tester test the loop resistance value, so the measured grounding must form a loop, for single point grounding, it cannot be measured directly.
4 other clamp application of grounding resistance instrument
In many environments (such as the basement or the engine-room, the lightning rod, elevator, gas station, Ground covered by concrete, and the grounding body which can not be separated from the grounding system and so on), using traditional resistance meter to measure the grounding resistance is very difficult. MEWOI clamp on earth resistance tester can measure the grounding fault which the traditional resistance tester cannot.For example, in a grounding system, the grounding resistance value is qualified, but the contact resistance of grounding lightning protection belt, or the Connection lines between the ground overhead lines may become too large or even break, although the grounding resistance of grounding system is qualified, but not qualified.
5 of the same grounding, two kinds of measuring results when differences, please pay attention to the following issues:
1) With traditional resistance tester, grounding wires are tripped or not (that is, the measured grounding is separated from the grounding system). Without tripping, the test result is the whole parallel grounding resistance value of grounding system, this parallel value is much less than the grounding resistance , and it is of no sense.
2) The national standard GL/T621-1997 "AC electric device grounding" stipulates: "the sum of grounding or natural grounding resistance of grounding resistance and the resistance of grounding conductor is called the grounding resistance." Under normal circumstances the traditional grounding resistance meter can measure the grounding resistance to the ground, can not measure grounding conductor resistance.But MEWOI clamp on earth resistance tester measure the sum of the grounding resistance and grounding conductor resistance, fully meet the requirements of the national standard.
3) if there is only several grounding electrode in the grounding system, the use of clamp on earth resistance will have some error, usually a little larger. If we want to get accurate grounding resistance value, we can use the finite point grounding system to calculate the program.
In summary, the two methods of measurement of grounding resistance are conditional restrictions, both of which have advantages and disadvantages which can not be replaced by each other. In order to get a credible measurement result, the user should choose a correct measurement method according to the structure and environment of grounding system.