My return to Classic Cmp - San Diego, software archive, etc.

[NLS's products] How did they work? I rmember seeing (and alas failing to obtain) an partically mechanical digital voltmeter. The circuitry was a servo system, similar to the ones used in chart recorders. The motor drove a mechanicla turns counter, coupled to an accurate multi-turn helical potentiometer, which provided the feedback to the servo amplifier (it replaced the slidewire in th chart recorder implementation). THe operation is obvious, apply an input voltage, the motor turns until the feedback from the pot balances the input votlage, the turns counter then effectively shows where the pot is Somewhere I have most of a valved DVM. 'Most of' because alas some idiot stripped a number of passive components off it before I got it. It's stuffed with valves (I would guess about 50 of them), including 4 trochotron counter tubes. The display is a row of nixie tubes. I've not figured out how it worked, alas. -tony