[time-nuts] 1PPS measurement

Bob kb8tq kb8tq at n1k.org
Sat Aug 12 14:46:35 EDT 2017


> On Aug 12, 2017, at 9:16 AM, Laurens de Bruijn <laurens at snowflake.as> wrote:
> Long time listener, first time caller.
> I’ve been doing some background reading, but unable to find a definitive answer to this, grateful for links or direct input:
> I have 
> a. 53132A (no options, internal XO, about 1ppm or worse )
> b. Jackson Labs Fury (about +/-20ns 1PPS accuracy)
> c. EUT with 1PPS that I want to characterise.
> The EUT is a test box that can produce 100-1500ns of jitter on its 1pps. I would like to measure this and find out if it's RMS or pp jitter, preferably to about 10ns accuracy.
> There is no further documentation on the EUT added jitter mode.
> 1. Should I connect the 53132A Ch1 to Fury 1pps, Ch2 to EUT 1pps, measure time interval and log? That should give me better than 20ns accuracy (Fury 1pps)? *or* do I need to take the ‘132A standard timebase error into account (3ppm according to the recent calibration 2017)?
> 2. If the latter, I assume I should connect the Fury 10MHz out to the ‘132A  REF in?
> 3. Else connect the 53132A Ch1 to EUT 1pps, Fury 10MHz to Ch2 and start/stop with Ch1, measuring the count on Ch2 - would that give me 2 counts of 1/10e6 = 200ns uncertainty?

Furry 10 MHz goes to the ref in on the counter.
One pps goes to channel A
The other pps goes to channel B
Start on A, stop on B, measure the delta and log it.

Play with your test device to get a reasonable offset and start logging data. If the test device is also GPS locked, 
offset the Furry using cable delay to keep things from running into each other (pps at virtually the same time).


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