HT instruments MACROTEST 5035 - Manual (Page 48)

MACROTEST 5035
EN - 47
When the environmental conditions preclude the “3P” measurement mode, as for example
in the city center, In TT plants is possible to measure the earth resistance with the
simplified “2P” method that gives an higher value than the “3P” mode does.
An auxiliary rod is necessary, it must have an unimportant earth resistance and must be
independent by the earth plant under test.
In the picture is shown a water tube as auxiliary rod, but it could be replaced by any
metallic object fixed to the ground.
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 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