Amprobe Multitest-1000 Continuity-Tester - Manual (Page 34)

When the environmental conditions preclude the “3P” measurement mode, as for example
in a city center. In TT plants it is possible to measure the earth resistance with the
simplified “2P” method that gives a higher value than the “3P” mode does.
An auxiliary rod is necessary; it must have an insignificant earth resistance and must be
independent of the earth plant under test.
In the picture above, a water tube is used as the auxiliary rod. But, any metallic object
fixed to the ground could replace it.
Example: if the operator takes three consecutive measurements, the instrument displays
1 st measurement:
main display = measured resistance value (Ex: 0.90 Ω)
secondary display on the left-hand side = 001 (no. of measurements = 1
means that 1 earth measurement has been taken)
secondary display = average of the measurements taken (in case just one
measurement has been taken the medium value is equal to the measured
value, in this case 0.90
Ω)
2 nd measurement:
main display = measured resistance value (Ex: 0.96 Ω)
secondary display = average of the measurements taken ((Val1+Val2)/no.
of measurements = (0.90+0.96)/2 = 0.93
Ω)
3 rd measurement:
main display = measured resistance value (Ex: 0.93 Ω)
secondary display = average of the measurements taken ((Val1+Val2)/no.
of measurements = (0.90+0.96+0.93)/3 = 0.93
Ω)
Note: Any test with a result over 1999
Ω is not inserted in the calculation of medium
value.
Example: 1
st measurement:
main display: 1.07 Ω
secondary display: 1.07 Ω
2 nd measurement
main display: 4.15 Ω
secondary display: 2.61 Ω
3 rd measurement (not inserted in the medium value)
main display: >1999 Ω
secondary display: 2.61 Ω