Multimeter grounding resistance measurement method
Find two 8mm, 1m long round steel, one end of which will be sharpened as an auxiliary test rod, were inserted into the grounding body to be tested on both sides of the A 5m away from the ground, the depth should be in the 0.6m or more, and make the three to maintain a straight line.
Here, A for the grounding body to be tested, B, C for the auxiliary test rod
Then use a multimeter (R * 1 stop) to measure the resistance between A and B; A and C, respectively, recorded as RAB, RAC, RBC, and then calculated to find the grounding resistance value of grounding body A.
As the grounding resistance refers to the contact resistance between the grounding body and the soil. Let the grounding resistance of A, B, C are RA, RB, RC. and then set the resistance of the soil between A and B is RX, because AC, AB distance is equal, it can be A and C between the soil resistance is also RX; and because BC = 2AB, so B and C between the soil resistance approximated as 2RX, then:
RAB=RA+RB+RX。。。。。。
①RAC=RA+RC+RX。。。。。。
②RBC=RB+RC+2RX。。。。。。
(iii) ① + ② - ③ that is: RA = (RAB + RAC - RBC)/2。。。。。。 ④
④ type is the formula for grounding resistance.
Example of measurement: today measured the following data of a grounding body: RAB = 8.4 ∩, RAC = 9.3 ∩, RBC = 10.5 ∩. Then:
RA=(8.4+9.3-10.5)/2=3.6(∩)
Therefore, the value of ground resistance of the measured grounding body A is 3.6∩.
It is worth noting that: before the measurement, you need to polish the three grounding bodies A, B and C with sandpaper shiny to minimize the contact resistance between the meter pen and the grounding body, in order to reduce the error.
