MEWOI MEWOI4000, User Manual, Page: 13 / 20

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Wire Resistance Verification
In order to improve precision and stability of field measurement of earth
ground resistance, avoid error due to wire resistance change due to prolonged
usage of testing wires; avoid error due to testing wire that is failed to be fully
inserted into tester interface or by poor contact; avoid error due to
users’
replacing or lengthening testing wires and etc., wire resistance verification is
specially designed, as to
"20Ω"grade, which is more accurate on low value
resistance measurement.
After connection of testing wire and the Tester, connect the other end of
all testing wires in short circuit, as the following figure, set FUNCTION rotary
switch to the corresponding earth ground resistance measurement position,
press
button to start verification. During verification, LED indicator flashes,
LCD displays, and after verification, LED displays wire resistance value and
stores it. For this time switch on, it will automatically deduct the verified wire
resistance value from earth ground resistance measurement.
It will not preserve the verified wire resistance value on switching off. It
needs re-verification for next time switching on.
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Precision Measurement
Please make sure testing wire plug has been totally inserted into testers
corresponding interface and it may cause measurement value error for
incomplete insert or poor contact.
As to low value earth ground resistance measurement, it will be more
accurate after wire resistance verification.
On measuring grounding voltage, between E and C interface, it will occur
the maximum voltage about 50V! Please do not impose voltage on
measurement interface. Please pay attention to avoiding electric shock
accident.
On measuring earth ground resistance, testing wires cannot be mixed
around, which shall be measured separately.
Try to choose the spot with more water to deeply bury auxiliary grounding
rods P and C, in order to reduce auxiliary earth ground resistance and
thus reduce indication error.