[time-nuts] ? phase comparison or other device

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Jul 1 18:02:44 EDT 2007

Bob Paddock wrote:
>> These devices are a little noisy below 100Hz.
> Rather than constantly battle the "there is to much noise", what are
> your thoughts on deliberately injecting out-of-band noise?
> As an example:
> http://www.analog.com/UploadedFiles/Application_Notes/319765654AN-410.pdf
> "Overcoming Converter Nonlinearities with Dither"
>> The distortion produced by a diode clamp is immaterial when one is only 
>> interested in the zero crossing time.
> It depends on where the harmonics fall.

What is the application for which you want to use injected out of band 
Since the performance of a well designed zero-crossing detector is 
equivalent to a 25 bit ADC when locating the zero-crossing, it will be 
difficult to replicate this performance using a lower resolution ADC 
even combined with out of band dithering.

In practice, diode clamp circuit distortion in a zero-crossing detector 
isn't an issue.


More information about the time-nuts mailing list