Specific measurement methods for testing ground resistance with a multimeter
Regarding the method of testing the ground resistance with a multimeter, you need to polish the three ground bodies A, B, and C with sandpaper before measurement to reduce the contact resistance between the test leads and the ground body. The measurement process of the multimeter testing the ground resistance, friends in need For reference.
How to test ground resistance with multimeter
In use, a dedicated ground resistance tester is expensive and inconvenient to purchase. Can I use a multimeter to measure the ground resistance?
A multimeter was used to conduct experiments on ground resistance in soils of different soil types, and the data measured by the multimeter and the data measured by a special ground resistance tester were compared. The two were very close.
Measurement methods:
Find two 8mm, 1m long round steels, sharpen one end as an auxiliary test rod, and insert them into the ground 5m away from both sides of the grounding body A to be tested. The depth should be more than 0.6m, and keep the three in a straight line. Here, A is the grounding body to be tested, and B and C are auxiliary test rods.
Then use a multimeter (R*1 gear) to measure the resistance values between A and B; record them as RAB, RAC, and RBC between A and C, and then calculate the grounding resistance value of grounding body A.
Since the ground resistance refers to the contact resistance between the ground body and the soil, let the ground resistances of A, B, and C be RA, RB, and RC respectively. Let the resistance of the soil 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; and because BC=2AB, the soil resistance between B and C is close to
It seems to be 2RX, then:
RAB=RA+RB+RX.
①RAC=RA+RC+RX.
②RBC=RB+RC+2RX.
③Put ①+②-③ to get: RA=(RAB+RAC-RBC)/2. ④
Equation ④ is the calculation formula for ground resistance.
Example: The measured data of a certain grounding body today are as follows: RAB=8.4∩, RAC=9.3∩, RBC=10.5∩. Then: RA=(8.4+9.3-10.5)/2=3.6(∩), so the ground resistance value of the measured ground body A is 3.6∩.
Note: Before measurement, polish the three grounding bodies A, B, and C with sandpaper to make them shiny to minimize the contact resistance between the test leads and the grounding body to reduce errors.
