[time-nuts] Basic question regarding comparing two frequencies

[Robert LaJeunesse]

EDN magazine published a simple USB to GPIB design back in 2005, and someday I 
might build one up for myself. Hence this email is meant to be informational and 
not an endorsement. The original author has updated his design since then, check 
out the info and links at http://lpvo.fe.uni-lj.si/gpib/ where the original 
design is well documented for DIY and the updated version available as a "kit" 
if that interests you. 


Bob LaJeunesse



________________________________
From: Mark Spencer <mspencer12345 at yahoo.ca>
To: time-nuts at febo.com; jfor at quik.com
Sent: Sat, July 24, 2010 9:15:20 PM
Subject: Re: [time-nuts] Basic question regarding comparing two frequencies

Thanks for the insight re the GPIB interface.  I'm curious if any has any 
insight as to a suitable usb or pci to GPIB interface module or card ?  It 
sounds as though other surplus test gear is likely to have a GPIB interface.  
Regards

Mark Spencer

On Sat Jul 24th, 2010 6:40 PM EDT J. L. Trantham wrote:

>I would agree. GPIB (aka HPIB) is ubiquitous and is a great place to start.
>Unfortunately, I haven't gotten that up to the top of my 'to-do' list yet.
>I have a computer, HP and National interface cards, cables, but no time to
>find the software to make everything communicate yet.  I think it has a lot
>to do with the fact that I have relatively old HP equipment that is
>relatively 'tongue-tied' but I think I will be able to figure it out once I
>get the time.
>
>Certainly the right place to start though, IMO.
>
>Joe
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of J. Forster
>Sent: Saturday, July 24, 2010 5:24 PM
>To: Discussion of precise time and frequency measurement
>Subject: Re: [time-nuts] Basic question regarding comparing two frequencies
>
>"..  more generic interface." ??
>
>The vast majority of professional test equipment has GPIB. Virtually
>anything else is an "also ran".
>
>FWIW,
>
>-John
>
>============
>
>
>> Thanks, I'm glad to hear I am on the right track.   At some point it would
>> be
>> nice to obtain a counter that can measure the drift of the time base in
>> the
>> 5328A.  The 5328A has a GPIB interface but as the display only varies by a
>> few
>> counts I'm not inclined to track down a GPIB adapter just to plot this.)  
>> Hopefully a newer counter would have a more generic interface.
>>
>> Best regards
>> Mark Spencer
>>
>>
>> ----- Original Message ----
>> From: J. L. Trantham <jltran at att.net>
>> To: Discussion of precise time and frequency measurement
>> <time-nuts at febo.com>
>> Sent: Sat, July 24, 2010 1:49:51 PM
>> Subject: Re: [time-nuts] Basic question regarding comparing two
>> frequencies
>>
>> Sounds about right.  One cycle per 5 seconds or about 0.2 Hz difference.
>> Therefore, 9,999,999.8 Hz.
>>
>> I would feed the GPSDO to trigger your scope and look at the output of the
>> time base on one channel of the scope.  You could also look at the GPSDO
>> on
>> the other channel.  Then you could adjust your counter time base to
>> 'freeze'
>> the display.  Probably good to 'align' the counter time base but for long
>> term comparison, probably better to use a counter and plot the difference.
>>
>> Joe
>>
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>> Behalf Of Mark Spencer
>> Sent: Saturday, July 24, 2010 12:29 PM
>> To: time-nuts at febo.com
>> Subject: [time-nuts] Basic question regarding comparing two frequencies
>>
>> Hello:
>>
>> Just for grins I decided to compare the frquency from my GPSDO to the time
>> base
>> in my 5328A counter.   
>>
>>
>> I connected the 10 mhz time base from the counter to channel A of my 100
>> Mhz
>>
>> scope, fed the 10 mhz signal from my GPSDO into Channel B and with a T
>> adaptor
>> also fed this signal into the input of the counter.    I scope to trigger
>> from
>> Channel B.  
>>
>>
>> The drift betwen the two signals on the scope seems to match the error in
>> the
>> displayed frquency on the counter.  (ie. if the counter shows 9999.9998 it
>> takes
>> approx 5 seconds for the the wave form on channel A to slip a full cycle
>> realitve to channel B.)  
>>
>>
>> Is this a reasonable approach or is there a better way to compare two
>> frequencies using a scope ?
>>
>> Best regards
>> Mark Spencer
>>
>>
>>
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>
>
>
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