MRU-200-GPS OPERATING MANUAL Version 1.06
20
Note:
Earth ground resistance measurement may be performed successfully if the in-
terference voltage does not exceed 24V. The interference voltage is measured
up to 100V, but over 50V is it signalled as hazardous. Do not connect the meter
to a voltage exceeding 100V.
- Pay particular attention to the quality of the connection of the tested object with the test leads
–
the contact area must be cleaned of paint, rust, etc.
- If the resistance of the measurement probes is too high, then the measurement of earth ground re-
sistance R
E
will be affected by additional uncertainty. A particularly high measurement uncertainty
occurs a low value of earth resistance is measured with probes with weak contact with the ground.
(This situation can occur if the earth electrode is adequately driven into the ground but the upper layer
of the ground is dry and characterized by a low conductivity. The relation between the probe re-
sistance and the resistance of the measured earth ground will be high, leading to measurement un-
certainty. In this situation, perform the testing in accordance with the formulae specified in point 10.2
which will permit evaluation of the influence of the measurement conditions. It is also possible to im-
prove the contact of probes by moistening where the probe is driven, or driving probes into other loca-
tions, or using a longer 80 cm / 2.5 ft. probe. Check that the test leads are securely connected, the
insulation is not damaged, and the probe contacts are not corroded or loose. In most cases meas-
urements will be successful; however, be conscious of the sources of uncertainty the measurement
can be affected by.
- If the resistance of both
H
and
S
probes or one of them exceeds 19,9k
Ω, the meter displays the
message: "
R
H
and R
S
electrodes resistance are higher than 19.9 kΩ! Measurement impossi-
ble!
".
-
Manufacturer’s calibration doesn’t include the resistance of test leads. Displayed result is sum of
measured object and test leads resistance.
Additional information displayed by the meter
R
E
>19,99k
Ω
Measurement range exceeded.
V
N
>40V!
and a con-
tinuous audio tone
The voltage on the measurement points exceeds 40V,
the measurement is cancelled.
V
N
>24V!
The voltage on the measurement points exceeds 24V
but lower than 40V, the measurement is cancelled.
LIMIT!
The uncertainty of the electrode resistance > 30%. (Un-
certainties calculated on the basis of the measured val-
ues)
NOISE
!
The value of the interfering signal is too high,
the result may be distorted by additional uncertainty.
