Measuring Earth Resistance

1. Normal Earth Resistance Measurement

• Connection of test leads
  Stick the auxiliary earth spikes, P and C, into the ground as shown in Figure 1 of the instruction manual. They should be aligned at an interval of 5 to 10 meters from the earthed equipment under test. Connect the green lead wire to the terminal E (T1) of the instrument, the black wire to the terminal P (T2) and the red wire to terminal C (T3).
  Note: Make sure to stick the auxiliary earth spikes in the moist part of the the earth. Give enough water when the auxiliary earth spikes have to be stuck into the dry, stony or sandy part of the earth so that it may become moist.
• Earth Resistance Measurement
  Set the function switch to 2000Ω or 20Ω position and make another measurement.
  Note: If the earth resistance of auxiliary earth spike C is too high to make measurement, the main digit reads “—-“. When this occurs reduce the earth resistance, for example by adding moisture to the part of the earth where the spike is stuck, and check the test lead for loose connection.

2. Simplified Earth Resistance Measurement

Use this method when there is no space to stick auxiliary earth spikes. In this method, an existing earth electrode with a low earth resistance, such as a metal water pipe – a common ground point of of a commercial power supply and an earth terminal of a building – can be used in place of C and P earth spikes.

• Connection of test leads
  Make connection as shown in Figure 2 of the instruction manual.
  Note: short P and C terminals with a shorting wire.
• Earth Resistance Measurement
  Set the function switch to the 2000Ω position and press test button to perform measurement. Then, if necessary, turn the function switch to the 200Ω or 20Ω position and perform another measurement.
  Notes:
  * The instrument does not trip any residual current circuit breaker in a power distribution circuit since its measuring current is less than 2mA
  * True earth resistance value Rx is calculated as follows:
  RX=RE – re
  re: Earth resistance of a common earth of commercial power supplly etc.
  RE: Reading of the instrument

Coming soon!