[time-nuts] Measuring 1 PPS with an HP 5335A

Bill Dailey docdailey at gmail.com
Sun Feb 16 20:33:18 EST 2014


No idea.  That's what's sad.  They all blend together.

Sent from mobile

> On Feb 16, 2014, at 6:17 PM, "Jimmy D. Burrell" <jimmydburr at gmail.com> wrote:
> 
> Bingo! It's working now!! Thanks to everyone on the thread.
> 
> Paul, I have to give chops to Bob on this one, even though my experience is the same as yours with respect to the preset triggers. Actually, your comments/question about the "trigger lights flashing" in concert with the 1PPS signal got me looking/thinking and no, they weren't. BTW, my 0.000001 number was meant to be Hz but I left off the units.
> 
> Both Bobs (Camp and Albert) were pointing me at the 'input'. So, I drug out the HP5335A manual and re-read about all 4 trigger levels. Auto-adjustable mode allows adjusting the trigger according to the amplitude of the input signal... a sort of percentage trigger mode, i.e. turn the trigger control clockwise to 3/4 scale and you're triggering at 75% of the signal's amplitude.
> 
> The above trigger changes combined with reconfiguring for 50ohms input signal did the trick. I'm now seeing readings like 0.999 999 983 +0.
> 
> Thanks again,
> 
> Jim...
> N5SPE
> 
> 
>> On Feb 16, 2014, at 4:07 PM, Bob Camp <lists at rtty.us> wrote:
>> 
>> Hi
>> 
>> If you have a 50/50 duty cycle 1 pps, it’s going to work with a lot of settings. With a narrow (say 10us wide) pulse, most of the counters have auto trigger issues. If it’s already known to be reading nutty, trigger is a good place to start looking.
>> 
>> Bob
>> 
>>> On Feb 16, 2014, at 4:29 PM, Paul <tic-toc at bodosom.net> wrote:
>>> 
>>>> On Sun, Feb 16, 2014 at 2:33 PM, Bob Camp <lists at rtty.us> wrote:
>>>> 
>>>> On all these counters, you need to switch to DC input for 1 pps signals.
>>>> You also need to manualy set the trigger level to something like +1.5V.
>>> 
>>> 
>>> I can't believe I'm disagreeing with Bob Camp but this is not my
>>> experience.  99.9% of the time preset trigger works fine and I think you
>>> should start with that.  AC coupling almost always works and is sometimes
>>> required (with the Rb I think).
>>> 
>>> I have a 5335A (w/ opt 010+040) and have measured 1PPS on my PRS-10, Fury,
>>> Firefly and random GPS parts.  If the trigger light is not flashing at 1 Hz
>>> the only thing I've ever had to do is toggle AC coupling or enable 1PPS
>>> output on the device (or plug it in).  Sometimes increasing the gate time
>>> tidies up the display.
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