Typically grounding resistance test, need embedded grounding, the ground level lead to the grounded equipment. In order to ensure that the grounding resistance meets the requirements, a special grounding resistance tester such as the Japan Kyoritsu 4105A Grounding Resistance Tester / Kyoritsu 4102A is usually required for measurement. Or use a relatively high clamp type grounding resistance tester. However, in use, the dedicated grounding resistance tester is expensive, inconvenient to purchase, can you use a multimeter to measure the grounding resistance? The author used a multimeter to test the grounding resistance in different soils, and measured the data and dedicated grounding of the multimeter. The measured data from the resistance tester were compared and the two were very close. The specific measurement methods are as follows: Find two round steels of 8mm and 1m length, and use one end of the sharpening point as an auxiliary test rod, respectively inserted into the underground 5m away from the grounding body A to be tested, the depth should be above 0.6m, and keep the three lines in a straight line. Here, A is the grounding body to be tested, and B and C are auxiliary test bars. Then use a multimeter (R * 1 block) to measure A and B; the resistance between A and C, respectively, recorded as RAB, RAC, RBC, and then calculate the grounding resistance of the grounding body A. Since the grounding resistance refers to the contact resistance between the grounding body and the soil. Let the grounding resistances of A, B, and C be RA, RB, and RC, respectively. Let the soil resistance between A and B be RX. Because the distance between AC and AB is equal, the soil resistance between A and C is also RX. Because BC=2AB, the soil resistance between B and C is approximately 2RX, then: RAB = RA + RB + RX. . . . . . 1RAC=RA+RC+RX. . . . . . 2RBC=RB+RC+2RX. . . . . . 3 will be 1 + 2 - 3 to get: RA = (RAB + RAC - RBC) / 2. . . . . . 4 Type 4 is the calculation formula for the grounding resistance. Measured example: The data of a grounding body measured here is as follows: RAB=8.4∩, RAC=9.3∩, RBC=10.5∩. then: RA=(8.4+9.3—10.5)/2=3.6(∩) Therefore, the grounding resistance of the grounding body A to be tested is 3.6 ∩. It is worth noting that before the measurement, the three grounding bodies A, B and C should be sanded and polished with sandpaper to minimize the contact resistance between the test leads and the grounding body to reduce the error.
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Method of testing grounding resistance using a multimeter
Method of testing grounding resistance using a multimeter