[volt-nuts] DMM calibration

[Didier Juges]

I had my eBay special $90 HP3478A calibrated by our internal cal lab (traceable to NIST). Based on the sticker, the last cal was 5 years old. The instrument was well within all specs by a wide margin (most readings were within 20% of the stated tolerance, which after 5 years is pretty good.

Didier KO4BB

Roy Phillips <phill.r1 at btinternet.com> wrote:
>
>
>-----Original Message----- 
>From: Electronics and Books
>Sent: Thursday, August 08, 2013 12:54 PM
>To: Discussion of precise voltage measurement
>Subject: Re: [volt-nuts] DMM calibration
>
>Specs for a 3478A
>
>
>Brand HP Model 3478A Counts 303.099 TrueRMS X Display LCD  Year 1983
>Range 
>Stability [ppm] Low   High   Resolution      1y
>DC Volt 30m  300  100n 60 AC Volt 300m 300  1u  2000 Max Frequency 300k
>
>Resistance 30  30M  100u 160 DC Current 300m 3  1u  1500 AC Current
>300m 3 
>1u  7200 Interface GPIB Battery backup X
>If you do the adjustments with some hobby equipment wich an accuracy of
>say 
>20 to 30 ppm. Thats all within limits of this multimeter. You never see
>the 
>difference.
>In my opion, expensive adjustments and calibration for not so accurate 
>equipment is a waste of money. Especialy when the calibration price
>exceeds 
>the equipment price.
>
>
>
>
>
>Regards
>
>
>ElectronicsAndBooks at Yahoo.com
>http://ElectronicsAndBooks.com
>
>I would like to say - "you are absolutely correct" - I have recently
>been 
>quoted for a 3458A which requires a new set of ROM's and re-cal. - the
>cost 
>was greater than I paid for the S/H instrument just 4 years ago. These 
>prices are OK for large Companies who can recover the VAT for a start !
>
>......... but cannot be justified for hobbyists. Most of us have items
>of 
>equipment that have been calibrated in recent times, and other
>precision 
>items like resistors and higher spec. zeners that when you make
>comparisons 
>can verify your DVM's . I recently purchased a Keithley 2015 for less
>than 
>some cal. charges, this was calibrated in 2008 and I would say that it
>is 
>still in very good calibration now.
>Roy P
>
>
>________________________________
>From: "Marv @ Home" <marvin.gozum at comcast.net>
>To: Discussion of precise voltage measurement <volt-nuts at febo.com>; 
>Discussion of precise voltage measurement <volt-nuts at febo.com>
>Sent: Wednesday, August 7, 2013 6:53 PM
>Subject: Re: [volt-nuts] DMM calibration
>
>
>I don't know what logo cal is, but between Z540 and 17025 is a
>question of procedures and how they are done.
>In metrology the procedures, and how strict they are, reduce the risk
>of uncertainty in the final measurement.  For example, some
>procedures in Z540 can be 'interpreted' where in 17025 is explicit,
>thus there is more room in Z540 for one lab to be worse than another,
>or vice versa, which defeats the purpose of standardization.  This
>'intepretation' is fairly reduced when the device is cal'd by an
>autocalibrator such for close case calibration DMMs, but becomes a
>big issue with any manual cal.
>
>If these do not mean anything to you and you do not need the data for
>long term drift calculations, ISO 9001 is good to go.
>
>IMHO the difference between all 3 is insignificant for 5.5 digit
>DMMs, except for one's need for data.
>
>
>http://us.flukecal.com/literature/articles-and-education/temperature-calibration/papers-articles/comparison-ansincsl-z540-1?geoip=1
>
>At 12:30 PM 8/7/2013, Joseph Gray wrote:
>>I just got the following quote for getting my HP 3478A calibrated.
>>
>>35.00 for ISO 9001 no data
>>87.50 for Z540 with data and uncertainties
>>275.00 for 17025 with data, uncertainties and logo calibration.
>>
>>I still didn't get any explaination as to exactly what the lab does
>for
>>each of these price points. When I asked about the "Level 4" listed
>next to
>>the meter, I was told that it is the difficulty level. Still not
>telling me
>>much. I have read the procedure in the HP service manual and it is
>very
>>easy. You set some volt, amp, ohm values on the standard, then push
>some
>>buttons on the meter.
>>
>>I understand about getting data or not, it is the other aspects that I
>>don't understand. What is Z540, 17025 and "logo calibration"?
>>
>>
>>Joe Gray
>>W5JG
>
>
>
>Sincerely,
>
>
>
>Marv
>Philadelphia, PA
>
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