Hi Guys,I'm looking for the best ideas for implementing an AC powerinstrumentation front end for a microcontroller or FPGA.What I need to accomplish is to measure 50-60HZ AC in the range of120V upwards of 600VAC with about 1% accuracy, TRUE RMS. I need toextract:1. Voltage2. Current (via current transformers)3. Frequency4. Power Factor5. Phase differenceThis needs to work with reasonably distorted waveforms, like whatmight be found in small generators driven by engines. I also needsomething that will work for single phase or for 3phase and bescalable to instrument up to two 3-Phase sources.There are a variety of ways to go about this but I'm looking forsomething that is very flexible and can adapt to a variety of voltageconfigurations (line to line, or line to neutral) and is very lowcost.I would guess that it might be similar to the best practices thatwould be used in the front end of True RMS DMMs or DAQ cards with ACinputs? I know there are also energy metering chips out there, butthey are rather expensive.Thanks for any ideas!PW

Don't waste your time trying second- and third-best solutions. Go to Analog Devices' web site and acquaint yourself with their wide selection. We're featuring the ADE7753 in H&H AoE III, you could start there. 20-pin ssop, $4.61 at DigiKey. It's single phase, but they have more complex 3-phase versions with the same architecture, so what you learn on one is extendable.-- Thanks, - Win

Ideas for inexpensive True-RMS Metering?

Jul 03, 2010 41 Replies

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JosephKK 16 years ago

messagenews: snipped-for-privacy@4ax.com...

the pulse are proportional to the fault current. =A0Only the voltseconds= are limited.

Basically it becomes a Rogowski coil, and the transformation ratio changes drastically.

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Tim Williams 16 years ago

Or even less, if you wind over only a segment. This makes leakage worse = under operating conditions, but could be convienient under such fault = conditions.

Tim

--=20 Deep Friar: a very philosophical monk. Website:

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