[time-nuts] Is it Hz or MHz ?

wb6bnq wb6bnq at cox.net
Mon Jun 2 06:23:35 EDT 2014

Hi Tom,

My experience is the manufacturer's, of hp or fluke quality, reported 
error band (their spec sheet) is the worst case (or at least 3 sigma) 
provided that the device is operated according to the recommended 
environment, etc.

Nonetheless, my statement you quoted is still accurate as to the purpose 
of the specification.  Although I probably should have qualified a bit 
more.  It goes without saying that one should be careful when it comes 
to specmanship no matter who it is.


Tom Van Baak wrote:

>>The value of 5E^-11 refers to the resolution that the precision can be 
>>relied upon after taking into account all the factors that influence 
>>it.  It means that there is an error that can be as much as +/-5 parts 
>>per e^-11.
>No, it can be way more. A 5e-11 spec value is likely just RMS, or 1-sigma. Actual measurements will show significantly larger 2-sigma, 3-sigma, etc. value.
>Your "as much as" wording sounds more like a 6-sigma, or peak-to-peak spec.
>One must be very careful to match the measurement used to make the spec with how the device is intended to be used. For example, Magnus will likely tell us about MTIE, which is a perfect-storm, worst-case time error spec. It's very different from rough 1-sigma specs we usually talk about.
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