[time-nuts] [Fwd: Re: What is the best counter for a Time Nuts?]
hasweb at has.org.nz
hasweb at has.org.nz
Tue Oct 14 03:58:45 UTC 2008
Quoting Mike Monett <XDE-L2G3 at myamail.com>:
> hasweb at has.org.nz wrote:
>>
>> Mike Monett wrote:
>>> > So, assuming my known timebase is "bang on", I know the frequency
>>> > of the unknown 10 MHz source to an accuracy of roughly 3e-10 or 3
>>> > parts in 10 billion.
>>>
>>> > To get a more precise measurement of the frequency difference
>>> > between the two 10 MHz clocks, I supply the known 10 MHz clock to
>>> > the Channel A input of an HP 3575A Gain-Phase meter and the
>>> > unknown 10 MHz clock to the channel B input of the Gain-Phase
>>> > meter.
>>>
>>> Another very difficult instrument to find any data on. The best I
>>> could find shows it has an accuracy of ± 0.5 degree and resolution
>>> of 0.1 degree.
>>>
>> Try the agilent website for the manuals not yet readily available
>> For directions visit:
>> www.hparchive.com <http://www.hparchive.com>
>>
>> There is a 3575A manual for downloading at the Agilent ftp link.
>> If you read it you will find that the specified error with 10MHz
>> inputs is much larger: 10-20 degrees or so.
>>
>> Bruce
>
> There is nothing in the hparchive site, and I don't have the Agilent ftp
> site url.
>
> Could you give a direct link to the 3575A manual?
>
> The basic principle is sound. It should be very easy to make a simple PWM
> circuit to measure phase accurately at 10MHz. You mentioned the same thing
> earlier. Why not post the schematic so we can take a look?
>
> Mike Monett
>
> _______________________________________________
>
Mike
I did some time ago, for some examples (other implementations are also
possible ) see:
http://www.ko4bb.com/~bruce/LinearPhaseComparators.html
HP used to make the K345991A phase comparator for this purpose.
They also produced other variants for use with their caesium beam standards.
The quickest and easiest is to use the AD9901 phase detector as it
only has a few ns of non linearity at the end of the range. For higher
resolution just add a sigma delta ADC.
The Agilent link link:
ftp://ftp.agilent.com/pub/manuals/
is actually at the bottom of the text at the top of the equipment page
on the hparchive site
Sorry I cant post the site as a link as I am temporarily using a
backup email server as the regular one can't yet find the new time
nuts server.
Bruce
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