[time-nuts] Influence of Cycle Wraps on TInt-Measurements with53132A
hans.holzach at gmail.com
Thu May 1 12:08:29 EDT 2014
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
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:
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.
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.
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:
> steps and drift removed (detail):
> autocorrelated. the average distance between two peaks is 94.6 s:
> as expected, the pattern is also visible in the ADEV plot
> (overlapping, all tau):
> and even better a few hours later (shorter period of cycle wraps):
> but almost invisible in the "standard" ADEV plot:
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