[time-nuts] Logging the grid frequency....

David davidwhess at gmail.com
Sat Feb 23 17:05:16 EST 2013

That was on my mind when I suggested a sampling phase comparator with
the sampling time adjusted for noise rejection.  Of course since I
have been doing a lot of research recently on sampler design, every
problem looks like a nail. :)

Thyristor commutation into a reactive load can be nasty but I have
heard horror stories about inverters as well.

On Sat, 23 Feb 2013 14:05:36 -0500, Peter Gottlieb <nerd at verizon.net>

>Some grid connected inverters have a LOT of noise around the zero crossings, so 
>much so that certain digital power meters won't function as they can't get 
>frequency lock.  I've seen this on the large Parker units as well as the low bid 
>units out of China.  So if you have solar or wind farm alternative energy 
>projects nearby you may indeed see excessive noise.
>Excess noise and high order harmonics from such inverters has on occasion caused 
>capacitive line filters on nearby equipment to overheat and catch fire.
>On 2/23/2013 7:53 AM, Didier Juges wrote:
>> "I am curious how this compares with the zero crossing method."
>> I suppose it should work much better because this method will not be so sensitive to noise around the zero crossings. It will use the entire waveform.
>> Didier
>> Sent from my Droid Razr 4G LTE wireless tracker.
>> -----Original Message-----
>> From: Gabs Ricalde <gsricalde at gmail.com>
>> To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
>> Sent: Fri, 22 Feb 2013 9:01 PM
>> Subject: Re: [time-nuts] Logging the grid frequency....
>> Hello,
>> I also don't have a Picotest or similar equipment but I've done similar
>> things by using the line input of a soundcard. Multiply the recorded
>> signal with a 60 Hz quadrature oscillator, apply a low pass filter then
>> do some analysis on the resulting phasor. The stability of the sound
>> card oscillator should be enough for this purpose.
>> You can measure the frequency difference w.r.t. the 60 Hz oscillator by
>> taking the slope of the phasor angle (be careful with phase wraparounds)
>> and you can do this as often as you like. I'm curious how this compares
>> with the zero crossing method.

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