-----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
[email protected]
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" <[email protected]>
To: Discussion of precise voltage measurement <[email protected]>;
Discussion of precise voltage measurement <[email protected]>
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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