[time-nuts] Name of integral of timing residual

Bob kb8tq kb8tq at n1k.org
Thu Apr 20 11:27:52 EDT 2017


On a normal GPSDO holdover spec, you are concerned with the maximum
time error over a specified period. Generally it’s going to be a 24 hour holdover,
but it can be longer or shorter depending on the application. The good old CDMA
spec got out into the 10 to 11 us range at 24 hours. Various OEM’s padded the number 
to give a bit of wiggle room. The spec typically referred to it as “maximum 
allowed error”. While a straight(ish) line from zero to max is a typical example, they
really didn’t care if it was a second, third, or fourth order wiggle bouncing go either side
of zero over the period. Figure 8  in the application note is a pretty good example of this. 
I *think* what is being asked for is the integral of figure 8 ….which is indeed not
something I’ve ever seen named. 


> On Apr 20, 2017, at 8:26 AM, Tim Shoppa <tshoppa at gmail.com> wrote:
> I looked at AN1279 and other HP Smartclock documents that were written for
> the telco holdover specs, and they always put a zero axis on the frequency
> offset, but I was surprised that for example fig A4 of AN1279 seems to be
> suppressing the zero axis for the time error. So they seemed to be
> unconcerned with the integral you speak of.
> Tim N3QE
> On Thu, Apr 20, 2017 at 1:17 AM, Jim Palfreyman <jim77742 at gmail.com> wrote:
>> Folks,
>> I'm after the formal name of something (if it exists), and this group, if
>> any, should know.
>> Consider a plot of a timing residual vs time. Say a watch against a maser,
>> residual=watch-maser.
>> Now if I now plot the cumulative sum (think integral) of the residual,
>> that's going to give me an overall view of how the clock is performing over
>> time. (If it helps, think of PID controllers and how they work in the "I"
>> part.)
>> Now if you look at *motion* of an object over time, and you integrate its
>> acceleration you get velocity, integrate again you get displacement.
>> Integrate again and you get "absement" and again you get "abcity" (I only
>> recently discovered these terms).
>> Does the integral of a timing residual have a name, and does the integral
>> of *that* have a name as well?
>> Any thoughts?
>> Jim Palfreyman
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