[time-nuts] TEC party: hardware suggestion

[Tom Holmes]

In thinking about how to implement a scheme to make the phase and frequency
comparison using what I have on hand, I considered the following as a
possibility:

An ARB with a GPS derived 10 MHz reference set to 60 Hz. The one I have has
a very low jitter spec. It actually is a dual ARB so I could use the 2nd
independent channel to calibrate the phase detector

A phase comparator, which I would have to construct or buy. The phase
difference output would be a DC voltage that could be calibrated. This is
the only piece that I know little about so suggestions on how to create this
would be appreciated. A 2-channel digital scope? A simple IC comparator?
Hey, it's only 60 Hz, how tough could it be?

A 6-1/2 digit DMM that could either be polled at intervals of a few mSec, or
could be set to capture a number of readings for transfer to the PC. In
either case the data could be time-stamped.

Sounds like fun!

Tom Holmes, N8ZM
Tipp City, OH
EM79


> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Chris Albertson
> Sent: Thursday, June 30, 2011 12:28 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] TEC party: hardware suggestion
> 
> On Thu, Jun 30, 2011 at 1:38 AM, Achim Vollhardt <avollhar at physik.uzh.ch>
> wrote:
> > Time-Nutties,
> >
> > how about using a small uC (PIC/AVR) clocked with 100ns instruction
speed.
> > Start = 1PPS from GPS, Stop = 60 Hz Edge? Use internal capture hardware
to
> > count processor cycles in between.
> 
> Recently posted plots show that all you need is an AC wall wart
> transformer and two resistors.   a uC is total overkill
> 
> The xformer and resistor voltage divider works because by dumb luck
> the pin in the rs232 port was designed to accept a signal that looks a
> lot like low voltage AC and even better, already has edge detection
> built in.  Also by dumb luck someone already wrote the software to
> monitor the pin's status and time stamp transitions.     This really
> is a case of pure luck.
> 
> 
> --
> 
> Chris Albertson
> Redondo Beach, California
> 
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