I was mulling over in my mind, about finding some old 200 micro-amp meters, the size used on the TV-7 tube testers. Measure the resistance and add till they read a total 2940 ohms. Then Remark the faces to read 0-120. Or find some 12 volt scales and see if the lines would line up by comparison.
Those stupid meters are going for around $150 each. I am also thinking about using 0-100 micro-amp meters and adding a shunt to bring meter sensitivity down to 200 micro-amps and going from there.
Just an Idea at this stage.
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