[time-nuts] How can I measure time-delay of a cable with HP 5370B time-interval counter?

[Orin Eman]

On Sun, Oct 28, 2018 at 8:31 PM Hal Murray <hmurray at megapathdsl.net> wrote:

>
> drkirkby at kirkbymicrowave.co.uk said:
> > I'm feeding a sine wave from a Stanford Research DS345 30 MHz function
>
> Are the levels set so it triggers at the same point?  It doesn't look like
> it
> in your photo.
>
> Looks like you are running at 1 MHz.  If the stop trigger is a little
> lower/earlier than the start trigger, you will have to wait a whole cycle,
> so
> 950 ns is a reasonable result.
>


Looked like the levels were on Preset.  So, a little difference in what
"Preset" means and as Hal says, you wait a whole cycle.

One could fiddle with the stop trigger level, but the rise time of the sine
at these frequencies is so long, that a small change in the trigger level
is going to make a large change in the measurement.

I'd try the same experiment with a square wave instead to minimize this
effect.

Once you get a stable measurement with a square wave, then experiment with
the trigger level controls.  Going clockwise from Preset, I usually see no
trigger, followed by a narrow band where it triggers, followed by no
trigger.  In the band where it triggers, assuming adjusting a stop trigger
that is set to the rising edge, as the trigger level is increased, so does
the time interval.