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G6Tanuki · 28th Nov 2019, 6:34 pm

Yes, it's a version of the Wheatstone Bridge - where you use a locally-generated current of opposite-polarity to 'balance' the current flowing in the circuit-under-test so there is zero-volts showing across the test resistor.

Then you decouple the instrument from the circuit-under-test, and measure the current now flowing in your instrument - which will be equal to [but of opposite sign to] the current that had been flowing in the circuit-under-test.

Something vaguely-similar is used in the world of explosives-and-detonators to measure the continuity of the 'firing loop', where you can't just go at it with a conventional ohmmeter for reasons which should be self-evident.

28th Nov 2019, 6:34 pm	#37
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,010	Re: What is it? Yes, it's a version of the Wheatstone Bridge - where you use a locally-generated current of opposite-polarity to 'balance' the current flowing in the circuit-under-test so there is zero-volts showing across the test resistor. Then you decouple the instrument from the circuit-under-test, and measure the current now flowing in your instrument - which will be equal to [but of opposite sign to] the current that had been flowing in the circuit-under-test. Something vaguely-similar is used in the world of explosives-and-detonators to measure the continuity of the 'firing loop', where you can't just go at it with a conventional ohmmeter for reasons which should be self-evident.