Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[acbern]

understand, it is maybe different here in Germany then, there are a number of 
labs with pretty low uncertainties who also support old gear adjustments.
on the other hand, you have to know who you are working with for what gear. 
Otherwise you can have unpleasant surprises.
in your case, if you have no nobody calibrating your meter with a specified 
uncertainty, maybe an option is to build your own decade of resistances and use 
a precisiion high voltage source (calibrator) and a 3458A as current meter. 
that brings you to say 10nA/100Gohms. if thats sufficient.



> Gesendet: Donnerstag, 19. April 2018 um 18:41 Uhr
> Von: "Dr. David Kirkby" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Would you be concerned if the manufacturer does not 
> have an uncertainty budget, so can't provide uncertainties in a calibration?
>
> On 19 April 2018 at 16:42,  wrote:
> 
> > -a calibration certificate without uncertainsties is totally useless. in
> > is not even a calibration.
> >
> 
> Having bought the meter, it is not so useless if it tells me it is working
> or not, but I do have some concerns I must admit.
> 
> 
> > -I have never understood why people are so keen on getting things
> > calibrated at Keysight.
> >
> 
> Well, quite simply there's nobody else I would trust to calibrate much of
> the Agilent equipment. I did contact one UKAS acredited lab, who quoted to
> calibrate loads of bits of my equipment, but declined this meter. But when
> I checked the companies uncertainties, I was totally unimpressed. For
> example, their uncertainty on capacitance at 1 MHz was well in excess of
> 0.05%, yet they quoted to calibrate the meter, which has a basic
> uncertainty of 0.05%. I also found their prices were much higher than
> Keysight.
> 
> Most companies are not going to be able to adjust Agilent stuff if it is
> out of spec anyway, as often the software to make the adjustments is not
> available. So I'm not convinced there is any half-sensible alternative.
> 
> Dave
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Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[Dr. David Kirkby]

On 19 April 2018 at 16:42,  wrote:

> -a calibration certificate without uncertainsties is totally useless. in
> is not even a calibration.
>

Having bought the meter, it is not so useless if it tells me it is working
or not, but I do have some concerns I must admit.


> -I have never understood why people are so keen on getting things
> calibrated at Keysight.
>

Well, quite simply there's nobody else I would trust to calibrate much of
the Agilent equipment. I did contact one UKAS acredited lab, who quoted to
calibrate loads of bits of my equipment, but declined this meter. But when
I checked the companies uncertainties, I was totally unimpressed. For
example, their uncertainty on capacitance at 1 MHz was well in excess of
0.05%, yet they quoted to calibrate the meter, which has a basic
uncertainty of 0.05%. I also found their prices were much higher than
Keysight.

Most companies are not going to be able to adjust Agilent stuff if it is
out of spec anyway, as often the software to make the adjustments is not
available. So I'm not convinced there is any half-sensible alternative.

Dave
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Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[acbern]

-a calibration certificate without uncertainsties is totally useless. in is not 
even a calibration.
-I have never understood why people are so keen on getting things calibrated at 
Keysight.






> Gesendet: Donnerstag, 19. April 2018 um 14:08 Uhr
> Von: "Dr. David Kirkby" 
> An: "Discussion of precise voltage measurement" 
> Betreff: [volt-nuts] Would you be concerned if the manufacturer does not have 
> an uncertainty budget, so can't provide uncertainties in a calibration?
>
> I have an HP 4339B high resistance meter. It can read up to 1.6 x 10^16
> ohms, with a basic uncertainty of 0.6%. It has a built in voltage source of
> up to 1 kV.
> 
> I've contacted Keysight (UK) and asked for calibration cost, with
> uncertainties, for this 4339B. However, they have said they can't provide a
> calibration with uncertainties, and when I asked why, they have said they
> do not have an uncertainty budget available that suites that model. Looking
> at the Keysight website, a calibration with uncertainties is available in
> the USA, but I guess for whatever reason Keysight UK don't have this
> ability on this specific instrument. On other instruments I have sent them,
> I have never had this issue.
> 
> I expect if I really wanted to, I could get it shipped to the USA and
> calibrated there, but I can't justify the costs that would be incurred if
> it was shipped to the USA and back.
> 
> From a practical perspective, I don't really need the uncertainties - it
> was more for interest sake. I also have a reasonable degree of confidence
> that as a reputable company, Keysight would not calibrate an instrument
> unless they were confident they could determine if it is in or out of
> specification.
> 
> The 4339B is a pretty obscure unit, requiring resistors up to 10^11 ohms to
> calibrate it.
> 
> I'm sending this to Keysight with a blank EEPROM, so there will be no
> calibration data whatsoever in the instrument. Hopefully that means
> everything will be set right, and so likely to stay in specification longer
> than it might otherwise do so. There are no trimmers in the 4339B - all
> calibration is via the EEPROM. A 3458A is used for calibration of the
> voltage source. I'm confidence the voltages will be measured accurately
> enough, but a bit less confident about the values of the resistors used for
> calibration.
> 
> Dave
> 
> Dr David Kirkby Ph.D C.Eng MIET
> Kirkby Microwave Ltd
> Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
> Essex, CM3 6DT, United Kingdom.
> Registered in England and Wales as company number 08914892
> http://www.kirkbymicrowave.co.uk/
> Tel 01621-680100 / +44 1621-680100
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[volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[Dr. David Kirkby]

I have an HP 4339B high resistance meter. It can read up to 1.6 x 10^16
ohms, with a basic uncertainty of 0.6%. It has a built in voltage source of
up to 1 kV.

I've contacted Keysight (UK) and asked for calibration cost, with
uncertainties, for this 4339B. However, they have said they can't provide a
calibration with uncertainties, and when I asked why, they have said they
do not have an uncertainty budget available that suites that model. Looking
at the Keysight website, a calibration with uncertainties is available in
the USA, but I guess for whatever reason Keysight UK don't have this
ability on this specific instrument. On other instruments I have sent them,
I have never had this issue.

I expect if I really wanted to, I could get it shipped to the USA and
calibrated there, but I can't justify the costs that would be incurred if
it was shipped to the USA and back.

>From a practical perspective, I don't really need the uncertainties - it
was more for interest sake. I also have a reasonable degree of confidence
that as a reputable company, Keysight would not calibrate an instrument
unless they were confident they could determine if it is in or out of
specification.

The 4339B is a pretty obscure unit, requiring resistors up to 10^11 ohms to
calibrate it.

I'm sending this to Keysight with a blank EEPROM, so there will be no
calibration data whatsoever in the instrument. Hopefully that means
everything will be set right, and so likely to stay in specification longer
than it might otherwise do so. There are no trimmers in the 4339B - all
calibration is via the EEPROM. A 3458A is used for calibration of the
voltage source. I'm confidence the voltages will be measured accurately
enough, but a bit less confident about the values of the resistors used for
calibration.

Dave

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100
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