On 11/13/2010 08:12 PM, Bob Camp wrote:
Hi
Ok, so right now you are looking at about 10 degrees out of 360 where one cycle
is 100 ns. More or less you are in the 3 ns range.
Some cheap stuff that will do better:
HP 5334
HP 5335
HP 5345
HP 5370
HP 5371
All are in the "sub $300" range on the normal sites. Some are sub $100. All are
available with GPIB for logging.
For a bit more money
HP 53131
SR 620
You may find one for sub $1000. Often you see them listed for nutty prices. I
certainly would not pay anywhere near $1,000 for either one.
The one I'd go for is the 5334. It's smaller than the rest. They likely are the
cheapest of the group. The ones I have *seem* to be more reliable than some of
the rest of the stuff listed.
All of them can run in any one of three modes:
1) PPS to PPS timing
2) PPS to 10 MHz edge timing
3) 10 MHz to 10 MHz timing
Technicality - you want to have a stable rate of measurements. One way
to achieve this is to use a PPS or similar trigger. The TADD-2
divide-down kit can be handy to proivde triggers from a 5 MHz or 10 MHz
source.
In particular you would enjoy triggering the measurement from a PPS (or
divided down 10 MHz to say 10 Hz or 100 Hz) and then do Time Interval
measurements with one 10 MHz rising edge (say reference) to the other 10
MHz rising edge. I have had great success with this method myself.
Number 2 on the list seems to have the fewest issues.
Actually, depending on the GPSDO style the PPS may be the "raw" GPS PPS
or the smoothed variant being a divide down from the 10 MHz. Method 2
would not be as clean as you would wish for some GPSDOs. Using the
trigger variant described above is preferred since it would would have
less issues with the noise of the PPS relative to the 10 MHz.
A completely different approach:
Pump both signals into a phase detector (RPD-1 or X-OR or what ever)
and use a DVM to log the voltage. You can get some super overkill
DVM's for less than you can get any of the counters. They will
easily get you into the sub ns range on resolution. Weather the
setup will be accurate at this or that level is in the "that depends"
category.
Hmm. Gotta try that one.
Cheers,
Magnus
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
