[time-nuts] Question re 1pps output on the Z3805A

[David]

TTL transition times are not all that fast, about 6ns for LS TTL, and
with a 26uS pulse width, you would only need a fast oscilloscope to
characterize the pulse edges.  Delay, phase, and pulse height
measurements in this case could be made even with a 20 MHz,
0.35/20Mhz=17.5ns rise and fall time, oscilloscope.

Any storage oscilloscope, digital or analog, will work great for such
a low repetition rate signal but a sampling oscilloscope in the
traditional sense would be exactly the wrong instrument.  It is
unfortunately and confusing that DSO could stand for either digital
storage oscilloscope or digital sampling oscilloscope and marketing
departments sure have not helped distinguish the two very different
instruments.

A good analog oscilloscope using normal as oppose to automatic
triggering in a dark room will work if you are desperate.  I have done
it but it is tedious and headache prone work.

On Sun, 25 Nov 2012 00:03:37 +0100, Azelio Boriani
<azelio.boriani at screen.it> wrote:

>Usually the PPS output from the Z-series GPSDO is a 26uS wide (from the
>HP58503A datasheet) TTL pulse. To measure it you must use a fast
>oscilloscope (because of the fast pulse rise time) and an analog or digital
>memory (because of the very low repetition rate). The best is to use a
>digital sampling 'scope and set the trigger to NORMAL.
>
>On Sat, Nov 24, 2012 at 11:42 PM, Mark Spencer <mspencer12345 at yahoo.ca>wrote:
>
>> Greetings.   I recently acquired two Z3805A gpsdo's from the usual auction
>> site.  (These units look like a Z3801.)
>>
>> Does any one know the specified output level for the 1pps signals or have
>> a high confidence measurement of the output voltage that they could share
>> with me ?  (Measuring fast rise time signals is not really my forte and I
>> don't trust my measurements of an apparent .15 volt pulse.)
>>
>> The status message sent from the units via RS 232 contains a TFOM ( time
>> figure of merit ?) variable and I've seen that phrase used in conjunction
>> with equipment that outputs a 10 volt 1 pps pulse.
>>
>> On a side note so far I'm pleased with the performance of the units (the
>> 10 Mhz output of better of the two has a typical adev in the low 10e-12 -
>> high 10e-13 range, and appears to be improving.)
>>
>> Thanks in advance for any comments.
>>
>> Regards Mark Spencer.