[time-nuts] J06 HP-59992A time interval calibrator for HP-531xxcounters

Bob kb8tq kb8tq at n1k.org
Sat Jul 8 19:18:49 EDT 2017


Good means whatever the 5313x needs for calibration. If that is four signals that are 
crossing zero within < 10 ps of the “correct time” then that is the definition of good in this case. 

Rise time delay, fall time delay are rarely the same in logic gates. Propagation inside a chip to
point A may well be different by nanoseconds relative to the propagation to a very similar 
point B. All of that would mess up a signal that *might* need to be 50/50 to within 10 ps  or 
a second signal that must cross zero half way in-between (also to within 10 ps). 

If you want to have a lot of fun with this, pull out the timing analysis tool for your favorite
FPGA and start fiddling around.


> On Jul 8, 2017, at 5:53 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
> tvb at LeapSecond.com said:
>> The PIC dividers are good to a couple ps. I suspect the larger issue is the
>> PCB and wiring design. 
> What does "good" mean?
> I'd expect the variations due to power or temperature would be easy to 
> measure.
> Delay through classic CMOS is linear with absolute temperature and inverse 
> linear with supply voltage.
> The classic way to get time-nuts level noise on FPGA outputs is to wiggle a 
> nearby pin.   That shouldn't be a problem with a dedicated PIC but would 
> probably show up if you are generating multiple frequencies.
> -- 
> These are my opinions.  I hate spam.
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