Surely this has been asked here before but my search of google groups turned up nothing.
I need a panel meter that can measure DC watts. Searched the websites of the major panel meter manufacturers that I know of and couldn't find a single one. Doesn't anyone make a DC wattmeter?
-- Google, not Google groups, is your friend.
Yep, tried that too. You end up with 98,000 hits of stuff I'm not interested in. After you look through about 100 of those you're eyes start glazing over and you loose interest. :)
I'm just looking for a simple panel meter that measures DC watts. I thought sure Simpson would have something but they don't. Isn't it as simple as a simple meter movement that uses two coils that work against each other. One connected across the volts and one carrying the amps?
Tom
Search with -com (minus com) helps with the glazing
Search engines
Simple panel meter? Good luck.
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Panel mounted wattmeters aren't a run-of-the-mill item, whether AC or DC. With the exception of the KWH meter on the side of your house, wattmeters usually require a bit of circuitry to perform the multiplication math that is necessary to produce an indication of watts. You didn't say what power level you want to meter. Are you talking watts, tens of watts, hundreds, etc.? What voltage and current levels are you dealing with?
There are a number of wattmeter circuits on the net, some low-power DC, but most are AC wattmeters. If the current sensing is done by a resistor in series with the load, then the circuit should be able to measure DC as well as AC. Of course, that is also dependent on the signal path being DC coupled throughout... any capacitors in the signal path would present an obvious problem.
OK... all that said, here are a few links to some circuits for you to ponder.
Cheers!!!
-- Dave M MasonDG44 at comcast dot net (Just substitute the appropriate characters in the address) Never take a laxative and a sleeping pill at the same time!!
I like those first two links. They are similar to another circuit I found in a Bob Pease article. I like reading his "Stuff".
What's All This Multiplication Stuff, Anyhow?
I don't fully understand all that feedback he has in there yet. It's all part of scaling and offsets. I need to study that some more. Wish some of that handwriting was a little clearer.
I may have to go in that direction. I'm running about 20 watts. Voltage varies around 2 to 5 volts. Current varies around 4 to 10 amps. All DC.
Tom
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