This is a bit embarrassing, but me and my multimeter could use a second opinion !
I have Power Control Unit that is plugged into the wall and gets 110 VAC it then outputs between 0-65VAC to control the transparency of an electrochromatic film. The PCU also has three terminals to attach a potentiometer. Depending on the variable resistance provided via the pot the film fluctuates transparency. My ultimate goal is to replace this analog pot with a device I can control computationally. (Maybe an MDAC or a digipot..)
Regardless of how I ultimately replace the analog pot, my first task is to figure out what voltage the three terminal for the pot are outputting and I am confused.
When I hook up a potentiometer to the arduino there is ground, power, and the analog in, so my assumption is that the three terminals on the PCU would follow the same pattern, but it is not so clear...
Evidence it is DC:
- When I test with the multimeter it reads both as AC and DC, which I have read indicates DC.
- The reading become negative when I switch the probes- indicating polarity
- I have attached two LEDs to it in parallel with a resistor (as this post suggests) and one led lights up.
(It reads between 0 and 11 VDC)
Evidence it is AC:
- There is no clear ground. When I test between the middle terminal and the terminal that seems to be ground there is still current flowing through it. Term one is ground for for both other terminals and terminal two can be used as ground for term three.
- The input is AC and the output is AC and when I open it up I can't find a component that is converting between the two and it appears to be wired as a pot and not a rheostat.
Why would there be a charge coming through the middle terminal, shouldn't it just be an analog in? As when it is wired to an arduino.
How do I determine conclusively whether it is AC or DC? If it was DC wouldn't there be a clear ground?
Thanks in advance!