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

Tony> [NLS's products] Tony> How did they work? I rmember seeing (and alas failing to Tony> obtain) an partically mechanical digital voltmeter. The Tony> circuitry was a servo system, similar to the ones used in chart Tony> recorders. The motor drove a mechanicla turns counter, coupled Tony> to an accurate multi-turn helical potentiometer, which provided Tony> the feedback to the servo amplifier (it replaced the slidewire Tony> in th chart recorder implementation). THe operation is obvious, Tony> apply an input voltage, the motor turns until the feedback from Tony> the pot balances the input votlage, the turns counter then Tony> effectively shows where the pot is Interesting approach. The only mechanical one I've seen was based on a successive approximation A/D converter with relays. It would take a sample in a few hundred milliseconds, with a clear "prrrt" sound as the relays flipped back and forth through the approximation sequence. I'm fairly sure it was made by HP. paul