Frequently Asked Questions - Greenlee CMGRT-100A Manual De Instrucciones

Frequently Asked Questions

Q: Does the ground electrode have to be disconnected and isolated as is required when using the "Fall-
Of-Potential" test with auxiliary electrodes?
A: No. Actually the electrode must be connected to the system to provide the path for test signal
injection as well as to provide the background impedance necessary as the reference. Additionally, if
the tested rod is poorly bonded to the ground connector, a high reading will be present.
Q: Does this mean I am not able to test an independent electrode?
A: No. However, as soon as the connection is made to a multiple electrode system, usually provided by
the connection to the system neutral, you can clamp on and make a measurement.
Q: Must the unit be clamped directly on the electrode?
A: No. The unit provides valid measurement results when clamped onto the electrode or the conductor
leading to the ground electrode. The reading through the conductor verifies not only the ground
electrode resistance, but also the connections of the ground wire to the rest of the system.
Q: Does the system under test have to be energized or de-energized to perform the test?
A: We are measuring the grounding network. The only requirements are that ground connections be
made to the system under test and that the voltage-to-ground at the tested point not exceed the
instrument rating.
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 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 35 mm (1.38") and can accommodate cables up to 1000 MCM.
Accuracy
Accuracy is specified as ± (a percentage of the reading + a fixed amount) within the following parameters:
• Temperature: 23 °C ± 3 °C (73.4 °F ± 9 °F)
• Relative humidity: 50% RH ± 10%
• Conductor location: Centered in jaw
• Battery charge: 6 V ± 0.2 V
• External magnetic field: < 40 A/m
• External electrical field: < 1 V/m
• Loop resistance: Non-inductive
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