What is the procedure for measuring the earth resistance?
Measurement of Earth Resistance by using I.T.L. Earth Resistance Tester – (Model ET-1/10 )
Steps for measuring the earth resistances
The procedure for measuring the earth resistance is given in the following.
- Drive four spikes into ground in a straight line at an equal distance of 15 meters in-between spikes.
- Connect the spikes to the terminals.- the first to C1, the second to P1, the third to P2 and the fourth to C2.
- Select the resistance range using selector switch.
- Keep the potentiometer knob at 5 on the dial scale calibrated 0 to 10.
- Rotate the handle of the generator slowly and watch the deflection of the null detector. If the needle deflects to right the earth resistance is less and if the needle deflects to left then the earth resistance is more than 5 set on the dial.
- Increase or decrease the potentiometer knob to obtain null deflection.
- If null can not be obtained, change the position of the selector switch to higher or lower range and repeat steps 4 to 6.
- Rotate the handle of the generator at about 160 to 180 R.P.M. and adjust the potentiometer until “NULL” is obtained.
To know the value of the earth resistance’s multiply the dial reading by the value of the range. To know the resistance of the earthing device ,connect the terminals C1 and P1 to earthing device and P2 and C2 for spikes at a distance of 15 meters and meters in a straight line and repeat steps 3 to 9. If the meter pointer is not steady, then increase or decrease the cranking speed to obtain “NULL” point.