AC Measurement

**bcd** · - 14th November 2006, 12:20

It depens on the linearity of the transformer. Small transformers tend to have quite bad regulation and this can greatly affect the linearity. This is why the Elektor article had two in series so the 230v primaries were only run at 115v to move the transformers response into a more linear region.

Best suggestion I can make it to get a voltmeter of the appropriate type and measure the mains voltage at the same time you measure the output of the transformer to see if it is linear. If you can find a variac it makes it very easy as you just ramp up/down the voltage and plot the i/p to transformer o/p ratio.

I'll have a look for the CC info - I have found the folder with it in - Its ISSUE 164 - March 2004
FROM THE BENCH Intelligent Current Sensing: Harness the Power of the ACS750 Hall Effect Current Sensor, by Jeff Bachiochi, p.68

Code is at ftp://ftp.circuitcellar.com/pub/Circ...-Bachiochi.zip

Bill.

**Acetronics2** · - 14th November 2006, 14:51

See Here:

http://ww1.microchip.com/downloads/e...tes/00220a.pdf

That's the smart way ...

Alain

**Atom058** · - 15th November 2006, 00:40

Alain! Thanks for the link to the ap note! That looks like what I am trying to achieve. I have ordered the parts for the input side of the circuit as well as a variable transformer (for testing).

Bill - I found the index listing for the article that you told me about but it is not available for viewing. Is there a way to get a copy of the article from them?

I will try to put together the circuit from the ap note and let everyone know how it goes and post my results. Keep your fingers crossed!

Thanks everyone!

**Atom058** · - 14th December 2006, 20:20

Hello All - As promised, when I came up with a suitable solution, I would post it. Here it is... It works well for my application - I just need a good response between 110 and 125VAC. I used a split-bobbin transformer, bridge-rectified it and put it through a voltage divider (that has a trimmer on it so that you can adjust the output a little). Simple and cheap solution. Get nice values over the range I am interested in (about 1VDC over 15VAC range).

Enjoy! And thanks!

Atom058