Electronics > Metrology

What is the next best ratio measurement device after the 3458A?

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e61_phil:
Hi,

I would like to measure ratios. The voltage ratios between two decade resistors connected in series for example (like Fluke 5450A calibration). To avoid trouble with my wife, I have to postpone the purchase of a 3458A ;)

According to https://www.eevblog.com/forum/testgear/8-5-digit-dmm/msg270530/#msg270530 and some manuals there is no DMM which specifiy a transfer accuracy better than 0.1ppm (0.05ppm+0.05ppm HP 3458A). Even the Datron 1281 is specified with 0.2+0.05ppm in the manual. (The Fluke 8508A seems to be linear to 0.035ppm FS, but a 8508A isn't an option)

I own a (noisy) Solartron 7071 (7081) and a Datron 1071 (7.5 digit but no transfer specifications found) as the highest resolution meters. These meters should be also far away from 0.1ppm linearity.


In https://www.eevblog.com/forum/testgear/hp34401-measurement-of-linearity/msg356304/#msg356304 Dr. Frank showed a very good linearity of his Fluke 5442A (below 0.1ppm of input).

Therefore, my question: If I could verify the linearity of my Fluke 5440B also to below 0.1ppm (I have access to some 3458A, but I have to carry the 5440B to the 3458A :( ) isn't it a good ratio measurement machine in combination with my beloved HP 3456A acting as nullmeter? (I also own a Fluke 845 AR Nullmeter, but the setup with the 3456A could be fully automated).

Or is there any cheaper  multimeter out there with very good linearity?

What do you think?

Dr. Frank:
Hello,
The referenced link was a one pass linearity test only, and one quadrant.
Somewhere else, I have published a multiple pass test on both quadrants.
The median linearity of my 5442 was about < 0.3 ppm, additionally both quadrants behaved differently in gain and offset.
As you see, this 0.1 ppm linearity is not achievable each time, that's a general phenomenom of A/D and D/A characterizations.
The 3458A linearity test vs JJA in hpj 4/98 also shows fluctuations during different passes. The 0.02ppm linearity is therefore a typical, median value only.
If you characterize your 5440, you may also achieve a median linearity of 0.2 ... 0.3ppm for one quadrant, but that's no guarantee.

So, the Fluke 720A with its 0.1ppm guaranteed linearity of input is the next best solution.
Frank

Edit: Added complete 8 pass linearity measurement

e61_phil:
I would like to have an automated setup to make an offset compensated ratio measurement with short time between the measurements. With such a setup it should also possible to make all the ratio transfers in the 5450A automatically. My Knick JS 3010 can act als voltage and current calibrator. I would use this to supply voltage/current to the series resistors.

Rewiring is only needed to transfer the 10k reference to the 5450A 10k.

Therefore,  I don't want a KVD :)

Another option/upgrade could be a computer controlled switchable 1:10/1:1 hamon divider which divides the output of my 5440B. Very similar to the described technique in the 5440A handbook, but automated.


@Dr. Frank: How do you calibrate the 1R resistor in the 5450A? The manual says one should use a 1R reference resistor (same as stated in the 5700A calibration process). Do you transfer the 10R to 1R?

I would like to know the 1R also as precise as possible (within my capabilities) to transfer this further to my 0,1R shunts.

Thanks.
Philipp

Dr. Frank:
I use my 3458A only, and live with the mediocre calculated uncertainty for the 10 Ohm range at 1 Ohm
Frank

acbern:
I am using SR1010s for transfer of 10k to other resistance values. But these are not cheap either, depending on where you get them.

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