[time-nuts] PicTic Data

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Aug 15 05:42:21 UTC 2010


An ACAM GP2 evaluation board is available here:
http://shop.omegacs.net/

However an ACAM GP1 would probably be a better fit in a DMTD with a beat 
frequency of 10Hz or more as the GP1 has a measurement range of 200ms.

Bruce

Stanley Reynolds wrote:
> Thanks for looking at my data that was what I was fishing for all along :-)
>
> I was looking at the article:
>
> "A Small Dual Mixer Time Difference (DMTD) Clock Measuring System W.J. Riley "
> Richard posted
>   
> And thinking it would be nice to do the DSS and Mixer boards to go with the
> pictic II.
>   
> Or changing the Pictic II to use the Acam TDC GP2 Time to Digital Converter; 2
> channel w/65 ps resolution now under $30. as Bruce suggested a while back.
>   
> My wants sure exceed my cans ;-)
>   
> Stanley
>   
>
>
> ----- Original Message ----
> From: John Miles<jmiles at pop.net>
> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
> Sent: Sat, August 14, 2010 11:25:44 PM
> Subject: Re: [time-nuts] PicTic Data
>
>
>    
>> John glad you are getting good results and have something to
>> compare to. Back to
>> me who doesn't have any knowns but lots of guessing. Attached is
>> a run with a
>> box cover over the pictic, run is shorter ~ 800 seconds but the
>> box does look
>> like it helps.
>> I need to do a lot more testing but sometimes I just get excited :-)
>>      
> I imported your .txt file alongside the traces I captured.  Assuming it was
> taken with 1 Hz on both START and STOP, it looks like the attached.
>
> You're getting the exact sort of results that I see if I feed both the START
> and STOP inputs at 1 Hz.  My guess is that the onboard oscillator limits the
> performance in that case, since it has a lot of time to drift during the
> measurement if the two pulses occur close to 1 second apart.  Even the 5370B
> looks much worse if driven with 1 Hz on both inputs than it does with 1 Hz
> at START and 10 MHz at STOP.
>
> So I think you're basically up and running OK.  When I get around to trying
> a better clock, I'll also go back and see if the 1-pps x2 performance
> improves.
>
> It would be great if the next spin of the board could include sine-to-CMOS
> shapers for the input channels as well as an external clock input, for
> people who are working directly with RF signals as opposed to 1-pps.
>
> -- john, KE5FX
>
>
>    
>> ----- Original Message ----
>> From: John Miles<jmiles at pop.net>
>> To: Discussion of precise time and frequency measurement
>> <time-nuts at febo.com>
>> Sent: Sat, August 14, 2010 10:19:46 PM
>> Subject: Re: [time-nuts] PicTic Data
>>
>> A few preliminary measurements here (I'm working on getting some software
>> support together):
>> http://www.ke5fx.com/pictic.htm
>>
>> -- john, KE5FX
>>
>>      
>>> -----Original Message-----
>>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>>> Behalf Of Stanley Reynolds
>>> Sent: Saturday, August 14, 2010 7:12 PM
>>> To: Discussion of precise time and frequency measurement
>>> Subject: Re: [time-nuts] PicTic Data
>>>
>>>
>>>
>>>
>>> My guess as to what the data may indicate is performance of the
>>> 10 Mhz 20PPM
>>> PICTIC internal oscillator, need to repeat test with precision
>>> 10Mhz and auto
>>> calibrate off. Fatness of the line/width maybe PICTIC error. Note
>>> graph seems to
>>> show me leaving the room and returning via the outside door. Not
>>> sure what the
>>> ~100 sec oscillations are, need to check a/c cycle time.
>>>
>>> Stanley
>>>
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>>
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