Clamp on "Ohm" Meter?

I think it puts a relatively small current into the wire and measures the resulting current, both from the primary of the clamp-on transformer.

Reasonable, monitoring the primary to see what is reflected from the secondary. I wonder if it runs at 60 hz?

Mikek

You can read the manual for the tester he's using at

The basic principle seems to that of a test-signal generator, and a current transformer. The tester generates a test signal and feeds it into one side of a current transformer (part of the clamp-on assembly). When this is clamped around a conductor that's part of a grounding system, the grounding system acts as the secondary in the current-transformer.

The impedance of the grounding system will be reflected back through the transformer and will appear as a load to the (signal generator) circuitry which is driving the primary winding. By measuring the current and voltage on the primary winding, the tester can determine the "reflected" impedance at the primary, and knowing the ratio of turns in the current transformer (with a one-turn clamp-on secondary) can calculate the effective impedance of the secondary.

For this to work, the grounding conductor or rod being tested must be part of a complete circuit - it can't just be sitting there hammered into the ground on its own.

I infer that what they would do, to measure a ground rod like this, is to clamp on a connection to the building electrical system... either a hot wire (as they did originally) or a ground-wire connection. This would create a loop whose impedance would be that of the ground rod and its earth connection, plus that of the wired connection back to the building grounding point - the latter should be only a few ohms and could be neglected.

The clamp-on tester generates its own test signal (1.2 kHz or so) and the voltage/current analysis circuit filters out the 60 hz (and harmonics) due to normal ground current flowing in the circuit being analyzed.

thanks for the URL.

bet you could use your soundcard todo the same thing for almost free

I love how they're wearing hardhats in that video.

"Earth" ;-) ...Jim Thompson

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Page 24 has a ok description.

Cheers

That meter was introduced and explained at 3:30

On a sunny day (Wed, 30 Apr 2014 22:11:49 +0000 (UTC)) it happened Cydrome Leader wrote in :

That drill hits pretty heavy if it drop on the guy below.