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

[Said Jackson]

Jim,

Really annoying feature of HP counters.

If you slowly drift from a positive period to a negative one, it will indicate negative numbers for a while.

Then almost sudden it will do the jump to 0.99999xxxx seconds.

I found that adding a phase delay (long cable) helps keep the numbers positive.

Or trigger one on the rising, and one on the falling edge to add 50ns delay ( for signals with good 50% duty cycle).

Bye,
Said

On Jun 11, 2013, at 21:13, Jim Palfreyman <jim77742 at gmail.com> wrote:

> Folks,
> 
> I'm struggling to understand this button and how it reports intervals. It's
> supposed to show negative when the Stop is before the Start.
> 
> When I connect up two clocks sending out 1PPS and say the one connected to
> Stop is ahead then sometimes I'd get -123.45 ns (say) and sometimes it
> flips to 999.999... ms. It can't seem to make up its mind which to use.
> 
> Why is this inconsistent?
> 
> If I flip it to + TI and make sure the leading clock is on Start - all
> works well.
> 
> Thoughts?
> 
> Jim Palfreyman
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