[volt-nuts] High precision calibration for the poor man

Samuel DEMEULEMEESTER sam at canardpc.com
Wed Oct 20 21:54:18 UTC 2010


Hi guys,

I love your level of knowledge and I would like to get your thought about a
way to achieve a calibration of a high precision meter without a high
precision calibrator. Let me explain myself. I have many 6.5 & 7.5 digits
meter and only two calibrated and certified tools: a Fluke 5500A calibrator
and an HP 3458A meter. The 5500A is very stable but can only achieve 5.5
digits precision. The idea is to source a known stable voltage with the
calibrator, then use the 3458A to correct (lower) the offset in order to
feed a 6.5 or 7.5 digits meter in calibration mode.

Example : I need 10.00000V +/-  25µV. I set the 5500A (or any other very
stable voltage source) to 10.0000V. I get 10.000073V, according to the
known-good 3458A. I’m now looking for a very precise way to step-down the
voltage (-70 µV) in order to achieve the rated accuracy needed to calibrate
the meter. That accuracy doesn’t need to be maintained for more than one or
two minutes.

Is it a stupid idea? What can I use to add a very small and very stable,
variable negative offset to a known voltage? A variable resistor should not
be able to meet the required accuracy without a drift. So, perhaps a high
precision aop ?

Any idea greatly appreciated :-)

---------------------
Samuel DEMEULEMEESTER
Presse Non Stop - Canard PC
http://www.canardpc.com
Tel : +33.6.13.73.4003
MSN : sam at x86.fr 





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