Ground Resistance Tester Models 3711 and 3731
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Q. Can the clamp-on method be used for substation grid resistance
testing?
A. It depends. It can be used as long as the instrument can be clamped
onto a point on the grounding system at a common point where it ties to
the system neutral. Testing a grid must be treated as if it were a single
electrode. Often, clamping on to points within the grid system will yield a
closed loop reading.
Q. How does clamp-on ground testing compare with the standard
“Fall-Of-Potential” test?
A. Empirical testing has validated that when performed correctly, both
methods will provide accurate and repeatable readings for ground
electrode resistance.
Q. How large a conductor can the jaw accommodate?
A. The inner diameter of the jaw is 1.25" and can accommodate cables
up to 1000 kcmil.
Maintenance
Warning
• To ensure optimum performance, it is important to keep the probe jaw
mating surfaces clean at all times. Failure to do so may result in error
in readings. To clean the probe jaws, use a lint free clean cloth, or if
the jaws are pitted use a very fine sand paper (fine 600 grit) to avoid
scratching the jaw, then gently clean with a soft cloth. Do not leave
any residue.
• For maintenance use only specified factory replacement parts.
• Avoid electrical shock: do not attempt to perform any servicing unless
you are qualified to do so.
• Avoid electrical shock and/or damage to the instrument: do not allow
water or other foreign substances into the case. Disconnect the unit
from all circuits and test cables before opening the case. Use caution
with metallic tools that may short battery packs, power supplies, etc.
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