[time-nuts] PICTIC II

Magnus Danielson magnus at rubidium.dyndns.org
Sun Jun 27 17:54:34 EDT 2010


On 06/26/2010 09:11 AM, Richard H McCorkle wrote:
> Fellow Time-Nuts,
> When I first uploaded the Simple PICTIC interpolating time interval
> counter to the K04BB site in 12/08 and presented it to the group as
> a Christmas present my goal was to get amateurs building their own
> interpolating time interval counters for GPS monitoring and making
> improvements to my design. The interpolator in the PICTIC was
> “borrowed” from an early HP counter with minor modifications so I
> didn’t design it and had no personal attachment to it.

Which counter? Just curious.

>    Over the last 18 months I have developed a new diode switched
> interpolator based on the comments made on line and have thoroughly
> tested it. Some suggestions made improvements in the performance and
> some resulted in poorer performance. I incorporated those suggestions
> that made improvements, eliminated those that made things worse, and
> once I was satisfied I sent the revised interpolator design directly
> to Bruce off line. Based on comments and suggestions he returned
> during a long series of emails I incorporated additional changes in
> the code, front-end, and interpolator designs and tested those
> changes until I was satisfied with the performance and he had no
> further comments. I am finally satisfied with the new design and
> admit that by incorporating the majority of the suggestions made
> the new interpolator has significantly better linearity than the
> HP interpolator used in the PICTIC and it is now suitable for
> higher resolutions.
>    I was reluctant to post the PICTIC II in this forum, as I don’t
> want to get in another public discussion of its faults without any
> discussion of the merits of a $50 serial output interpolating TIC
> on a 3.8” x 2.5” thru-hole board designed for amateur construction.
> The K04BB WIKI PICTIC page was recently updated to include the
> PICTIC II code and ExpressPCB board layout and schematic files for
> those that might be interested.
>
> http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:pictic
>
> The PICTIC II incorporates the new interpolator, requires a delay
> between the inputs, and uses a low stability XO timebase with
> software peak detection for calibration with provision for an
> external timebase like the PICTIC to minimize size and cost.

Sounds interesting. What is the ball-park figures? Resolution, jitter, 
linearity?

Cheers,
Magnus




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