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Precision zero crossing for mains metering 2

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Costin Ruja

Costin Ruja

Electrical
Joined
Oct 19, 2011
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93
Good afternoon,

I've done a few searches on the forum but nothing relevant came back.

I need some advice regarding a zero crossing circuit that will be used to measure phase shift for mains supply. I'm trying to have a precision of at least 1 degree electrical. For 50Hz that is aprox 50us pulses, so i think comparators can be used. Anybody used them before for this purpose? Can you please post some circuits that you think will work ?

Best regards,

Costin Ruja
 
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Comparator circuits should be easy for a practicing engineer to design, so I won't bother with that part. The big issue is how clean the incoming waveform is. Even a small amount of noise means you'll detect multiple zero crossings, so I have to ask... why do you feel you need better than 1 degree of phase resolution?

Dan - Owner
Footwell%20Animation%20Tiny.gif
 
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Take a look at this thread. It may not solve your problem but it may give an insight into the issue of noise and zero crossings.
Your fixed frequency will be an advantage.
thread240-477976
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
 
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A comparator is pretty crude; if you are measuring a line voltage, a phase-locked loop (PLL) might be a better choice, since you synchronous a clean signal to a noisy one, and use the clean signal to determine the zero crossing

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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