Popular Electronics Builds a Vacuum-Tube Voltmeter

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Popular Electronics Builds a Vacuum-Tube Voltmeter

by KirtB » Thu Jul 27, 2017 9:07 pm

Popular Electronics Builds a Vacuum-Tube Voltmeter, May 1959 Popular Electronics

Cafe visitor Terry W. recently wrote to me about a topic that ended up mentioning RCA's vacuum tube voltmeter (VTVM) known as the VoltOhmyst. VTVMs were the era's high-input-impedance multimeter, before field effect transistors (FETs) came on the scene. The higher a meter's input impedance, the less it loads the circuit under test. Any meter connected across a circuit appears as a parallel load to the source, so the closer it is to an open circuit, the better. Terry mentioned how the VoltOhmyst was a key component on test benches of many professionals. You can still buy various models of the VoltOhmyst on eBay... http://www.rfcafe.com/references/popular-electronics/build-vacuum-tube-voltmeter-may-1959-popular-electronics.htm

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