Specific measurement method for ground resistance testing with a multimeter
Regarding the method of testing ground resistance with a multimeter, before measuring, it is necessary to polish the three grounding bodies A, B, and C with sandpaper to reduce the contact resistance between the probe and the grounding body. For the measurement process of ground resistance with a multimeter, please refer to it for friends in need.
Method for testing grounding resistance with a multimeter
In use, specialized grounding resistance testers are expensive and inconvenient to purchase. Can a multimeter be used to measure grounding resistance?
Experiments were conducted on the grounding resistance of different soil types using a multimeter, and the data measured by the multimeter was compared with the data measured by a dedicated grounding resistance tester. The two were very close.
Measurement method:
Find two 8mm and 1m long round steels, sharpen one end of them as auxiliary test rods, and insert them into the ground at a distance of 5m on both sides of the grounding body A to be tested, with a depth of more than 0.6m, and keep the three in a straight line. Here, A is the grounding electrode to be tested, and B and C are auxiliary test rods.
Then use a multimeter (R * 1 gear) to measure A and B; The resistance values between A and C are recorded as RAB, RAC, and RBC, respectively. After calculation, the grounding resistance value of grounding body A can be calculated.
Due to the fact that grounding resistance refers to the contact resistance between the grounding body and the soil, the grounding resistances of A, B, and C are assumed to 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 can also be RX; Because BC=2AB, the soil resistance between B and C is close
If it appears to be 2RX, then:
RAB=RA+RB+RX.
① RAC=RA+RC+RX.
② RBC=RB+RC+2RX.
③ Take ①+② - ③ to obtain: RA=(RAB+RAC RBC)/2. ④
④ The formula is the calculation formula for the grounding resistance.
Example: The data of a certain grounding electrode measured today is as follows: RAB=8.4 Å, RAC=9.3 Å, RBC=10.5 Å. So: RA=(8.4+9.3-10.5)/2=3.6 (Å), so the grounding resistance value of the tested grounding body A is 3.6 Å.
Attention: Before measuring, polish the grounding bodies A, B, and C with sandpaper to minimize the contact resistance between the probe and the grounding body, in order to reduce errors.
