[time-nuts] another Ebay mixup, 5370

John Miles jmiles at pop.net
Sun Jun 10 15:45:19 EDT 2007

> Since, at various times the HP5370 used a discrete ECL gate crystal
> oscillator, an HP10544A, and an HP10811A as the internal reference, it
> would also be useful to indicate which of these a 5370 uses as its
> internal reference.

2300-series 10811A in this case.

> Taking the external 1MHz sinewave (EXT reference for HP5370) and
> assuming input attenuator set to 1x, and the 2 inputs are connected in
> parallel to the START BNC then the corresponding trigger circuit noise
> for 0.05V pk input (input signal is attenuated by 2 at the trigger
> circuit inputs for 50 ohm Zin ) is about 123uV rms for both the START
> and STOP channels which seems plausible.This gives about 50ps noise
> induced jitter at 1V peak amplitude. However since the time interval
> mode isnt specified

See other post (+/- TI).

> nor are the number of samples taken,
> these
> calculations are somewhat uncertain.

You end up having to specify a pretty broad range of readings no matter how
many samples are taken.  Lots of jitter in the jitter readings.  :)

I was using 10K samples and watching the display for 4-5 updates when I
recorded the numbers.  That's why they're all given as a fairly-vague range
of values.  (I don't get anywhere near the kind of repeatability that Ulrich
hinted at in the table he posted.)

> Also the intrinsic jitter of the source is not known (to me at least).
> At 2V peak the noise induced trigger jitter could be 25ps with other
> noise say 10-12ps.

True, the 3325 seems poorly-characterized in this respect.  I have never
seen jitter specs for it.

-- john, KE5FX

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