Clamp-on ground tester
Updated 2026-10-27
Data records
- Instruments of this class store readings and carry separate user-set alarm limits for resistance, voltage and current, so that a reading outside the expected band is flagged during a survey of many electrodes.
- A clamp-on ground tester also reads the alternating current flowing in the grounding conductor, so leakage current is observed without disconnecting the electrode; a selectable band-pass filter restricts the reading to power-frequency current.
- The value displayed is the resistance of the loop enclosed by the clamp, not an isolated electrode resistance; where equipment bonding creates a metallic loop in the ground system, the instrument reads that loop and the stakeless technique cannot be used at that point.
- Because the electrode stays connected and no stakes are driven, the clamp method is used where stakes cannot be placed, such as inside buildings, on paved sites and on transmission structures, and it avoids the hazard of breaking a ground connection on an operating system.
- A clamp-on tester cannot measure an isolated electrode, because a single path to ground gives the induced current no closed circuit; the fall-of-potential method is used instead.
- A clamp-on ground tester induces a known voltage into the grounding conductor through one clamp winding and measures the current that results through a second winding, or the second half of a dual clamp, and computes the resistance of the loop that the conductor forms with the ground system.
- The method requires the electrode under test to be one of several parallel grounds, because the induced current must return through the other ground paths; the reading treats the combined resistance of those parallel paths as negligible against the single path under test.
- The instrument class is written Clamp-on ground tester. Value: Clamp-on ground tester.
- Because the clamp method gives no independent check of its own result, maker guidance treats it as a trending tool for an existing ground system rather than as a verification of a new installation that has no earlier results for comparison.
Elsewhere in the family
- Ground Electrode Resistance related entry on Grounding Reference
Sources
- AEMC product page, Ground Resistance Tester Model 6417, web page edition, AEMC Instruments. Held as: Public page. Publisher page
- Electrical Testing Reference editorial taxonomy, Electrical Testing Reference editorial taxonomy of test methods, 2026-10 edition, Electrical Testing Reference. Held as: Own observation.
- Fluke application article, Stakeless method of earth grounding, web page edition, Fluke. Held as: Public page. Publisher page
- Fluke product page, Fluke 1630-2 FC Earth Ground Clamp, web page edition, Fluke. Held as: Public page. Publisher page
- Megger Electrical Tester article, A guide to earth testing, 2007-11-01 edition, Megger. Held as: Public page. Publisher page
- Megger product page, DET4 series four-terminal earth/ground resistance testers, web page edition, Megger. Held as: Public page. Publisher page
Changelog (18 entries)
| Date | Revision | Change |
|---|---|---|
| 2026-10-27 | created (instr.clamp-on-ground-tester.alarms-and-logging) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.alarms-and-logging) | |
| 2026-10-27 | created (instr.clamp-on-ground-tester.leakage-current) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.leakage-current) | |
| 2026-10-27 | created (instr.clamp-on-ground-tester.loop-not-individual) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.loop-not-individual) | |
| 2026-10-27 | created (instr.clamp-on-ground-tester.no-disconnection) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.no-disconnection) | |
| 2026-10-27 | created (instr.clamp-on-ground-tester.not-applicable) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.not-applicable) | |
| 2026-10-27 | created (instr.clamp-on-ground-tester.principle) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.principle) | |
| 2026-10-27 | created (instr.clamp-on-ground-tester.return-path) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.return-path) | |
| 2026-10-27 | created (instr.clamp-on-ground-tester.title) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.title) | |
| 2026-10-27 | created (instr.clamp-on-ground-tester.trending) | |
| 2026-10-27 | review_status unreviewed -> software_reviewed (instr.clamp-on-ground-tester.trending) |
Cite this page
Cite the governing standard for the fact itself; cite this page as the finding aid.
"Clamp-on ground tester." Test Instrument Reference. 2026-10-27. https://www.testinstrumentreference.com/instruments/clamp-on-ground-tester/.
Test Instrument Reference, Clamp-on ground tester (Oct. 27, 2026), https://www.testinstrumentreference.com/instruments/clamp-on-ground-tester/.
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title = {Clamp-on ground tester},
howpublished = {\url{https://www.testinstrumentreference.com/instruments/clamp-on-ground-tester/}},
organization = {Test Instrument Reference},
publisher = {Test Instrument Reference},
year = {2026},
note = {last substantive change 2026-10-27}
}{{cite web |title=Clamp-on ground tester |website=Test Instrument Reference |publisher=Test Instrument Reference |url=https://www.testinstrumentreference.com/instruments/clamp-on-ground-tester/ |date=2026-10-27 |access-date=}}