MPI-525
– USER MANUAL
22
Remarks:
Measurement of resistance-to-earth may be carried out if voltage of interfer-
ences does not exceed 24 V. Voltage of interferences is measured up to the
level of 100 V but above 50 V it is signalled as dangerous. The meter must not
be connected to voltages exceeding 100 V.
- Particular attention should be paid to quality of connection between the object being tested and the
test lead
– the contact area must be free from paint, rust, etc.
- If resistance of test probes is too high, R
E
earth electrode measurement will be burdened with additional
uncertainty. Particularly high uncertainty of measurement occurs when a small value of resistance-to-
earth is measured with probes that have a weak contact with earth (such a situation occurs frequently
when the earth electrode is well made and the upper soil layer is dry and slightly conductive). In such a
case, the ratio between resistance of the probes and resistance of the earth electrode tested is very
high and consequently, uncertainty of measurement that depends on this ratio is also very high. The
uncertainty is displayed on the screen in the column of additional results. In order
to reduce the uncertainty, it is recommended to improve the contact between the probe and soil, for
example, by dampening with water the place where the probe is driven into earth, driving the probe into
earth in a different place or using a 80 cm-long probe. Test leads should also be checked as follows:
check whether their insulation is not defective and whether the lead
– banana plug – probe contact areas
are not corroded or loosened. In majority of cases the measurement accuracy achieved
is satisfactory. However, one should always be aware of uncertainty value the measurement is burdened
with.
Additional information displayed by the meter
R
E
>1,99 k
Ω
Measuring range is exceeded.
U
N
!
Voltage at test terminals is higher than 24 V but lower than
50 V, measurement is blocked.
U
N
>50 V!
and contin-
uous audio signal
Voltage at test terminals is higher than 50 V.
NOISE!
Too low value of signal/noise ratio.
LIMIT!
Error caused by resistance of electrodes > 30%. (Measured
values are used in calculation of uncertainty.)
Interruption in measuring circuit or resistance of test probes
is higher than 60 k
Ω.
Electrode resistance
>50
kΩ
Resistance of electrodes within the range of 50...60 k
Ω.
Aborted!
Measurement has been interrupted with
ESC
key button.
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