[time-nuts] Why would Keysight UK uncertainty measuring 1 MHz be as high as 7.6 Hz?

[Scott McGrath]

Look at the service manual,  the calibration setup listed is usually pretty close to what Keysight is using in their local calibration facility.   For an LCR meter I doubt they would be using a time nuts grade counter

Content by Scott
Typos by Siri

> On Aug 29, 2015, at 10:02 PM, Bob Camp <kb8tq at n1k.org> wrote:
> 
> Hi
> 
> Well, since we all have made our totally uninformed guesses, the only 
> thing to do now is to give Keysight a call and see what the real answer 
> is. 
> 
> Bob
> 
> 
>> On Aug 29, 2015, at 1:46 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
>> 
>> On 29 August 2015 at 12:59, Javier Herrero <jherrero at hvsistemas.es> wrote:
>> 
>>> Hello,
>>> 
>>> The calibration certificate does not indicate that the measurements were
>>> done with the frequency counters referenced to the 5071A at the time of
>>> calbiration (if so, it would be listed under the Calibration Equipment Used
>>> table). It says that the 53132A were calibrated against the 5071A.
>>> 
>>> If for your calibration they have used 53132A witout the oven oscillator
>>> option it is very probable that its uncertainity is 7.6ppm as indicated in
>>> the certificate. Since the maximum error tolerable for the LCR meter is
>>> 100ppm (+/-100Hz @ 1MHz), it makes sense to perform the measurement with an
>>> instrument with an uncertainity of 7.6ppm, and not to use the better
>>> counter in the lab for that purpose.
>>> 
>>> Regards,
>>> 
>>> Javier
>> 
>> 
>> I would find it a bit hard to believe they would use a counter without an
>> oven in their lab, as it would seriously restrict what they can do with it,
>> making it more difficult to replace one counter with another. I would have
>> thought that within reason it best to have the lab have reasonably high
>> spec kit, so more than one instrument could be done on the same line. They
>> did for example use a pair of 3458As, despite I'm sure the voltage accuracy
>> requirements could be met with a multimeter with far greater uncertainty
>> than an expensive 3458A. It makes more sense (within reason) to have 3458As
>> in the cal lab, as it allows a wider range of instruments to be calibrated.
>> 
>> Also, if you consider the spec on the 53132A without an oven, it is 3 x
>> 10^-7 per month. So after 12 months that could be 12 * 3 10^-7 or 3.6
>> 10^-6, so if it did drift the maximum amount each month for a year, the
>> uncertainty would higher than it actually is.
>> 
>> I intended to contact Keysight about the calibration for a couple of other
>> reasons
>> 
>> 1) I would like to know if it was adjusted or not. That is not clear from
>> the cal certificate, since the
>> 
>> * As received condition  - Not applicable, as this calibration certificate
>> applies to the initial calibration of a new, refurbished or upgraded
>> equipment.
>> * Action taken  - The equipment was upgraded.
>> 
>> I doubt it has seen a cal lab in ages.
>> 
>> The upgrade was just a software one, to enable cable lengths of 2 m and 4 m
>> (option 006) to be used to connect the DUT, which they kindly provided free
>> of charge, on the condition I paid for the calibration.
>> 
>> 2) They never put any stickers over the screws that prevent the covers
>> being removed, which struck me as a bit odd.
>> 
>> Since I was going to ask about those two issues, I will ask about the
>> uncertainty on frequency too. It will be interesting what response I get.
>> I'm just interested -  I realize that this instrument does not demand much
>> of the counter used to calibrate it. The demanding calibration devices
>> would be the resistance and capacitance standards.
>> 
>> Dave
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