[time-nuts] Newbie with questions, SR620 ADEV

lymex at vip.sina.com lymex at vip.sina.com
Fri Jul 29 11:23:18 EDT 2005

Daer Tom,

Thanks very much for your reply. I not only see very good answer, 

by reading your mails(and other replies from )I also got some 

idea of how you reasoning the answer. Thats most valuable for me.

Another thing, I remembered you said once that all stabilities are

relative. When I saw your chart of ADEV for some of your best

frequency source at: http://www.leapsecond.com/museum/manyadev.gif

what is your reference? especially when you measure the two 

H-Masers in long time interval?


Lymex, BG2VO

----- Original Message -----

From:"Tom Van Baak" <tvb at leapsecond.com>

To:"Discussion of precise time and frequency measurement" <time-nuts at febo.com>

Subject:Re: [time-nuts] Newbie with questions, SR620 ADEV

Date:Fri, 29 Jul 2005 07:37:38 +0800

> > Hi everyone,

> > 

> > I'm very glad to be here for the first time.

> > Thank you John for manually registered me in.

> > Thank you Tom Van Baak for putting my e-mails here and also

> > for your great answer which clear up most of my confusions.

> > Sorry for my poor English because its not my mother tongue.

> > 

> > I come from a place where there are few people who are 

> > interested in time and frequency so I learn most of the

> > subject by myself mainly. Until one day I came across an

> > article by Tom and then his leapsecond.com which I read

> > with great interest, then I found this mailing list. After

> > read most of the archives I understand I belongs to here.

> > 

> > I have a lot of questions now (and probably more in the future).

> > Here is my first set of questions. 

> > 

> > We all know that Allan Variance/Deviation (ADEV) is one of the 

> > common ways to measure time domain noise of frequency sources. 

> > It seems to me that the noise of many time-interval equipment 

> > can also be described in this way.  

> > 

> > Q1A: Is ADEV could be used for all time-interval measuring 

> > equipments?

> > An example is at: http://www.timing.com/products/testsets.php

> > it says ADEV <5x10-14 at 1 second for TSC 5110A


> Yes, that is the noise floor specification for the

> TSC 5110A - the minimum resolution that it can

> measure. Every oscillator has a certain specified,

> or measured, ADEV plot; the same is true for any

> test equipment that does timing measurements.


> The resolution specification is not always listed

> as ADEV. Some counters advertise the "number

> of digits per second", or the single-shot resolution,

> or the LSD (least significant digit). But it's all

> essentially the same thing.




> /tvb





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