Author Topic: Perhaps an episode suggestion? The curious case of the potentiometer  (Read 1578 times)

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Offline STMartin

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I design and build apparatus for safety testing, and a few years ago came across a safety standard that required using a potentiometer to measure voltage.

Voltage dividers aside, as an amateur electronics enthusiast this made as much sense to me as measuring a mountain with happiness (although I'm sure some would disagree).

Being new to the field, and somewhat reluctant to try and call out an engineer who was almost certainly smarter than me, I looked it up first before I raised any alarm. It turns out there actually is a potentiometer (the instrument) that measures voltage, from which the potentiometer (the component) seems to derive it's name from. It's essentially a bridge circuit that can effect a very accurate voltage measurement without placing a load on the source. Apparently, it is still used in metrology to this day.

In our case, we were measuring galvanic voltage in an electrolyte of antifreeze. Something I'd expect to produce very saggy voltage. A precise, no-load voltage measurement would make perfect sense. In the end, this isn't what the original author of the standard intended, and the standard was changed instead, but I digress.

I think it would be cool to see Dave compare a potentiometer (the instrument) with his fancy equipment against a saggy voltage source. Something that could be severely impacted by even the smallest load. See which one is more accurate. I'd like to see if there is any mileage to be had from such an archaic instrument.

I'm sure there are plenty of people here who can tell me straight away why this is a useless experiment, but it'd be educational for us newbies, no?


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