[time-nuts] Frequency Counter Errors

Michael Blazer mblazer at satx.rr.com
Thu Mar 22 01:14:02 UTC 2012


The 5328A is manually switched.  30kHz to 10 MHz 1V RMS min, 5VP-P max 
into 1kohm.

Mike

On 3/21/2012 7:39 PM, Tom Knox wrote:
>   It must be that one counter has not switched to ext ref. It has been a while with both these counters, does the 5328A  auto switch to ext ref?
> The 5372A does have an auto ref switch and will acept 1,2,5,and 10MHz+/-1% at 1-5VPP . A quick way to check that ext ref is seen by the 5372A is during a measurement remove the ext ref. Measurements will stop. You will need to press the restart key to resume and "alternate time base selected press restart" will appear. Then perhaps if the 5372A is ok then use the 10MHz output from the 5372A (Which is phase locked to the ext ref in) to the ext ref in on the 5328A. That should narrow things down.
> Best Wishes;
> Thomas Knox
>
>
>
>> Date: Wed, 21 Mar 2012 17:05:44 -0700
>> To: time-nuts at febo.com
>> From: jmulchin at cox.net
>> Subject: [time-nuts] Frequency Counter Errors
>>
>> I have a question for the collective group.
>>
>> I have a HP 5372A and a HP 5328A frequency counters. Both counters use the same
>> PRS-10 Rubidium frequency standard driving a 6 channel reference distribution amplifier
>> to each counters reference input port. The problem is this;
>>
>> When I measure the same frequency on both counters, (done one at a time) the frequency
>> is generally off by about 300 Hz or so between the counters. Now I would expect an error
>> of +/- 1 digit, but 300Hz seems a bit strange to me. I can not find the problem and the
>> difference exists even if I use the internal timebases of each counter, give or take the timebase errors.
>> The frequency is always at least>200 to 300Hz off between the two counters and I don't know
>> which one to believe. You know the "man with 2 clocks" problem.
>>
>> Anyone have any idea what may be causing this?
>>
>> Thanks
>> Jerry
>>
>>
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