[time-nuts] +/- TI button on 5370B

Magnus Danielson magnus at rubidium.dyndns.org
Sat Jul 6 11:40:49 EDT 2013


Hi Azelio,

On 07/06/2013 05:05 PM, Azelio Boriani wrote:
> Not only: consider that most time interval counters have a minimum
> measurable interval (Racal 2351 is 2ns) and slowly crossing PPSes can
> be a problem to measure when they are about to cross. In my opinion it
> is always better to displace the PPSes, easily done when using GPSDOs
> and by using stable delay lines in other cases. The Racal 2351 has
> +/-TI measurement function.

Any such offsets can be troublesome with free-wheeling oscillators where 
you measure the PPS signal over a long time.

If you can, it is better to use a higher rate, trigger on PPS (either as 
START or STOP) or ARM on PPS and then have start and stop operate on the 
higher frequencies.

Naturally, the PPS can be replaced with an equalent signal at a 
different rate. The problems discusses is really with rate, so what 
happens at 1 Hz occuurs at 10 Hz or 100 mHz just as well.

There is counters able to handle these problems much neater. The 
HP5371A/HP5372A/HP5373A actually time-stamps the events. What few 
realize is that you can use the fast port for long or even continuous 
measurements. Some of the Pendulum counters, CNT-80/81 and 
CNT-90/90XL/91, I believe can do continuous measurements properly, but I 
haven't tried it properly.

Cheers,
Magnus


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