[time-nuts] Influence of Cycle Wraps on TInt-Measurements with53132A

Ed Palmer ed_palmer at sasktel.net
Thu May 1 16:05:35 EDT 2014


I've seen similar results with my Racal-Dana 1992 counter.  It has 
trouble measuring time intervals when the inputs are almost in phase.  I 
think there has been discussion in the past about how various counters 
handle that, but I can't find it right now.

Ed

On 5/1/2014 10:08 AM, Hans Holzach wrote:
> with a teenage girl in the house it is easy to prefer macs over pcs... 
> unfortunately, Timelab does not work on my mac, but Plotter does (via 
> CrossOver).
>
> however, if there is just a small number of data points per cycle, 
> Plotter will not remove the steps automatically, you have to do it 
> manually (that means Plotter removes only the step you mark). in my 
> example i had to remove 38 steps. i don't know the unwrapping 
> algorithm. it could indeed be a reason for the repeating pattern, but 
> certainly not the only one:
>
> https://farm3.staticflickr.com/2937/13895219797_efd4ff07cd_o.png
>
> when you look at the slope at the end of the cycle you see that the 
> slope is flat, it is even slightly positive, whereas at the beginning 
> of the new cycle it drops a bit sharper than for the rest of the 
> cycle. it looks like that at every step. in my opinion this is the 
> main reason for the repeating pattern, caused by the counter. removing 
> the step does not alter the last/first few data points of a cycle.
>
> hans
>
>
> What happens if you use Timelab to analyze the same data instead of 
> Plotter?
>
> I find that, depending on the dataset, one program or the other will
> sometimes have trouble removing the steps completely.  They leave small
> steps behind.  It isn't related to the counter used, but seems to be
> related to the number of data points per cycle and the unwrapping
> algorithm used by the program.
>
> Ed
>
> On 5/1/2014 4:05 AM, Hans Holzach wrote:
> > hi tom,
> >
> > thank you very much! that is quite interesting. i am happy to learn
> > that there is nothing wrong with *my* counter! converting the
> > non-linearity effect into a correction table is beyond my abilities,
> > but simply knowing that this effect is inherent to the 53132a counter
> > helps a lot.
> >
> > indeed, my plots look similar to yours. after only three hours of
> > warming up i measured the TI of an HP 10811 against the 1 pps output
> > of my fury. the 10 mhz output of the fury was used as the external
> > timebase of the counter.
> >
> > the raw data of one hour measuring. average period of cycle wraps is
> > 93.3 s:
> > https://farm8.staticflickr.com/7314/14076566541_79094d6850_o.png
> >
> > steps and drift removed (detail):
> > https://farm8.staticflickr.com/7348/14079753105_f8ac97766d_o.png
> >
> > autocorrelated. the average distance between two peaks is 94.6 s:
> > https://farm6.staticflickr.com/5518/14056659576_703b446cc2_o.png
> >
> > as expected, the pattern is also visible in the ADEV plot
> > (overlapping, all tau):
> > https://farm8.staticflickr.com/7382/14079754735_62d70d1480_o.png
> >
> > and even better a few hours later (shorter period of cycle wraps):
> > https://farm8.staticflickr.com/7042/14079754345_b4b6f9afb8_o.png
> >
> > but almost invisible in the "standard" ADEV plot:
> > https://farm6.staticflickr.com/5474/13893141107_5aa39eb199_o.png
> >
> > hans




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