I’ve worked in the electronic test and measurement business for over a quarter of a century, so I have a keen interest in test equipment. My friend Steve K0SRW came across an interesting “classic” voltmeter and decided that I needed it in my collection of electronic treasures. Thanks, Steve!
This measuring device is a clever design with a neon bulb used as the voltage detector. A potentiometer varies the voltage to the neon detector, with the potentiometer knob calibrated to read out in volts. You adjust the dial until the light just turns on. This meter works for both AC and DC voltages, from a range of 65 to 660 volts. Click on the pictures to take a closer look.
The original box came with the voltmeter and it says that it was manufactured by Industrial Devices, Inc. of Edgewater, NJ. The device is marked with US Patent Number 2,644,134, which I looked up one of the free online patent databases. The patent was applied for by Nathan Schnoll on July 20, 1949 and was issued on June 30, 1953. As expected, the circuit diagram uses the potentiometer as a simple voltage divider, varying the voltage to the neon bulb.
I’ve done some searching on the web but have not found anything beyond the patent document. Does anyone have any additional information on this voltmeter?
Hi Bob:
I have a Mini-volt, box, & two sheets of original instructions. If you'd like photos you can email me.
Bryan G. Hawley
Ottawa, Canada
bghawley99@gmail.com
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I have one of these… And I cant find anything about them either.
Hello Bob, my neighbor Larry, 89 years old, just gave me one of these mini 400 voltmeters. He said it was from about 1950, when he got out of the war and started Radio TV and Ham radio use and repair business. He did not have the box, but the meter works, we plugged it into the wall plug, still lights up right on 120v.
Very cool tool,, and it looks just like the one in your picture, take care, Mike