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Is it possible to modify this watt dial to work with less current? Answered

I've got a few of these watt dials that I would love to use in a project, however, they will not be reading wattages and will rather be controlled with Arduino. Right now they are set up to read up to 3750 w at 125v, which is much more power than I can source with an Arduino or would be achievable with this project. 

The way it is set up is that current goes through the magnetic coil and creates a magnetic field perpendicular, attracting a small magnetic block (slightly visible in the photo). Would simply rewrapping the coil with thinner magnet wire in more coils work?

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-max-

Best Answer 4 years ago

That appears to be a device that measures only current, and the needle will shift with current flowing though that single turn of red enameled wire. Because it ONLY measures current, the reading will only be accurate if the load has the 125V across it.

As long as 30A of current flows through it, regardless of the voltage at the load, it will read 3750W of power. You can replace the scale with an amp scale so you can measure current up to 30A, or if you have a specific use for it with a specific regulated voltage for the load, you can change out the wire and the scale. I would add several more turns of thinner wire to make this thing more sensitive to current. I'd imagine by changing the # of turns to 30, you can read current up to 1A full scale. then, if you still want this device to measure watts, assuming the voltage will always be 5V, it will read 5W full scale.

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astroboy907-max-

Answer 4 years ago

Thanks, I tried rewinding it with some scrap transformer wire, worked perfectly.

I'm not measuring anything with it (using it as a display), so accuracy isn't as important.

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-max-astroboy907

Answer 4 years ago

Great! glad you got it to work well!

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steveastrouk-max-

Answer 4 years ago

PS and the current is in phase with the voltage.

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-max-steveastrouk

Answer 4 years ago

Good point, the meter measures average current, and I am sure the power factor of the AC load will mean something, although I do not have a good understanding of the calculus needed to fully understand all of the in's and out's.

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rickharris

4 years ago

That's pretty much how all analogue meters work.

Yes rewinding with more turns at a smaller gauge will mean the dial will read with less current through it.