[time-nuts] R&S XSRM Rubidium Standard

Magnus Danielson magnus at rubidium.dyndns.org
Sun Sep 17 12:32:54 EDT 2017


Hi,

The word "calibration" is overloaded with multiple meanings, and 
incompatible too.

"calibration" is often used to describe adjustments to make a device 
operate correctly, such as passing the performance checks.

"calibration" in legal traceability is about measure the performance 
against references to form a traceable record of deviations from the 
norml. This may include adjustment to ease compensation, but this is not 
necessary. Regardless of wither adjustments where done or not, the 
calibration record will indicate the errors that then needs to be 
applied to the measurement for the measurement to be traceable, and this 
in itself requires documented knowledge about how to do the measurement.
Otherwise it's just a fancy indication.

Adjustment to a reference thus do not imply legal traceability, or even 
full functionality.

For full functionality, you have to go through the performance check and 
see that all values is within limits.

"calibration" can thus imply different things.

I regularly see people use these terms inconsistently. That people get 
disappointed when they get the wrong thing is to be expected.

Cheers,
Magnus

On 09/17/2017 05:23 PM, Scott McGrath wrote:
> As to the point most modern instruments have self calibration,   Most of the time 'calibration' is simply the performance check adjustments are not performed unless necessary
> 
> The difference being the instruments used in performance test are traceable to a national standards body.
> 
> So whats referred to as calibration is in reality performance validation.
> 
> How do I know this by becoming friendly with the local lab and years ago when i worked for govt i used to moonlight at one of the local cal labs.
> 
>> On Sep 17, 2017, at 8:57 AM, KA2WEU--- via time-nuts <time-nuts at febo.com> wrote:
>>
>> Modern test and radio equipment have self calibration capabilities, older
>> analog do not. Calibration is not always need for  just simple test, but
>> for specification conformation it is useful. A bit  of luck also  helps.
>>
>>
>>
>>
>> In a message dated 9/17/2017 8:08:00 A.M. Eastern Daylight Time,
>> drkirkby at kirkbymicrowave.co.uk writes:
>>
>>> On 15  Sep 2017 10:45, "Scott McGrath" <scmcgrath at gmail.com>  wrote:
>>>
>>> Precisely my point,   But when purchasing i  expect to pay for a
>> calibration at a minimum.
>>
>> I have on occasions  requested sellers to send an item to the manufacturer
>> (Agilent or Keysight)  for calibration *before* shipping it to me, offering
>> to pay the calibration  cost, but stating that I expect a full refund if the
>> item fails the  calibration.
>>
>> If a test equipment dealer is confident that something is  working well,
>> they should not object to sending it to the manufacturer for  calibration,
>> as long as the buyer is willing to pay.
>>
>> Of course if a  seller knows little about something,  they are not going to
>> do  this,  but the item should be appropriately priced.
>>
>> One UK seller  (grace1403) declined to send an Agilent N9912A FieldFox to
>> Agilent, because  "Agilent were too fussy"., failing items for trivual
>> issues.    But he did agree to send it to one of the cal labs he uses. I
>> thought it  was a waste of time going to one of the less fussy outfits,
>> but
>> bought it anyway. It was then clear on receipt that it was faulty.  (The
>> spectrum analyser functionality was ok, but it didn't work as a  network
>> analyzer).  He took it back,  but then advertised it on  eBay 6 months
>> later. When asked, he said nothing had been done to  it.
>>
>> eBay rules about who pays the return shipping charge for an item  that is
>> "not as described' keep changing, and may be different on different  sites.
>> But on a heavy item shipped internationally,  the postage cost  can be
>> comparable or exceed the calibration  cost.
>>
>> Dave.
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