[time-nuts] T.I. experimenting - newbie question

[bownes]

Another interesting measurement would be to use the timebase output and external reference to compare the readings using the same timebase. 

Or are you already using a gpsdo?



On Apr 5, 2011, at 12:08 AM, Joseph Gray <jgray at zianet.com> wrote:

> I'm keeping the "newbie question" in the subject for those who wish to
> ignore this thread. To those who respond, your contribution to the
> diminution of my ignorance is appreciated :-)
> 
> I had borrowed two different 5328A counters. I just compared them,
> using the exact same coax, connectors and settings. Both units were
> warmed up for over one hour.
> 
> In my previous readings, I was averaging for 1 s and rounding to one
> decimal place. The following readings are averaged for 10 s and
> rounded to two decimal places. This seemed like a good place to round,
> as the readings were stable enough to this point.
> 
> Old 5328A (slide power switch):
> + + = 19.43 ns
> - - = 19.49 ns
> 
> Newer 5328A (toggle power switch):
> + + = 18.92 ns
> - - = 19.41 ns
> 
> The A and B inputs on the old unit match much more closely. If I
> average the readings of each unit, there is more than 200 ps
> difference between the old and new unit. How do I know which one is
> correct?
> 
> Joe Gray
> W5JG
> 
> On Mon, Apr 4, 2011 at 8:25 PM, Joseph Gray <jgray at zianet.com> wrote:
>> Hal,
>> 
>> Here are the results I got using your suggestion. The numbers may be a
>> bit different than last night as I'm not sure I'm using the same
>> cable.
>> 
>> A+, B+ = 18.9 ns
>> A-, B- = 19.4 ns
>> 
>> Obviously there is some difference in delay between the A and B
>> channels. Otherwise, the two numbers would have been identical -
>> correct?
>> 
>> If I take the average of the two readings, I get 19.05 ns, which is
>> more precise than the readings I'm taking. I'm rounding to the nearest
>> 0.1 ns on the readings.
>> 
>> A+, B- = 5014.6 ns
>> A-, B+ = 5023.5 ns
>> 
>> If I take the average of these two readings and subtract out the 5 us
>> for 1/2 period of the 100 KHz square wave, if get 19.15 ns. This
>> agrees very closely with the above average.
>> 
>> I haven't looked at the service manual for the 5328A yet, so I don't
>> know if I even have the proper equipment to attempt a calibration. In
>> the mean time, would you say that taking the average of the first two
>> readings is a valid method?
>> 
>> Joe Gray
>> W5JG
>> 
>> On Sun, Apr 3, 2011 at 7:18 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
>>> 
>>> How about a square wave?  Start on one edge, stop on the next cycle.
>>> 
>>> You can play with start on rising edge, stop on falling and the reverse.
>>> They should add up to the total.
>> 
> 
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