David I think the the benefits of a meter such as a 3458A can be utilized even in an environment where temps and humidity are not controlled. barometric pressure can also have a substantial effect but would be extremely difficult to control. The 3458A has ACAL which can (to some degree) compensate for temperature and other factors. As for "it depends" the function and range can be very big variable. Also if traceability is an is important the the meter must be kept within specified parameters. That said I have been amazed at how little a my 3458A monitoring a 732B is affected even over a temperature change of as much as +/-10F. It easily stayed within manufacturers specs. But again "that depends" for although I have not really experimented with measurements more dependent on internal resistors over a similar time and temp range I imagine that would show a much greater uncertainty. Most of this is detailed in product specs. So from my practical experience I would think you would see benefits from a 8.5 digit meter in almost any environment . But obviously everything makes a difference so reducing variables where practical is important. What I find interesting - In this modern era of 8.5 digit meters my guess is more uncertainty is lost during shipping of the instrument then the rest of the year sitting on a bench. I see a future where precision instruments calibration is not only based on TIME but the environmental conditions the instrument was exposed to DURING that TIME utilizing an environmental package built in to the instrument continuously monitoring 1.hours power up, 2.temp, 3.humidity., 4.barometric pressure, and 5.vibration shock using an algorithm to providing the user with a real time estimates of uncertainty and notifying the user if the instrument has been exposed to conditions that exceed the instruments rated specs. I have actually experimented with this idea a bit although it has been on the back burner for the last few year because of other priorities. I believe there needs to be a rethinking of this aspect of calibration. But whatever the reason this has not yet been researched by groups such a NIST - simply is a lack of awareness or because it does not involve any sexy physics- this approach has the potential to improve uncertainties in actual work environment which is the en tire point of calibration. To start studying this is relatively simple, it would basically require a environmental chamber with capabilities to generate all the needed conditions on the device under test DUT and collecting data on both temporary uncertainty that recover, conditions that change uncertainty requiring re-calibration to correct, , and conditions that would permanently damage the instrument. Then studying real world conditions such as during shipping to build a model. I believe Fluke are the only group to have played with this studying the 732B's and building models on uncertainties during there rotation between metrology lab and changes in uncertainties of these standards when they arrive back at Fluke. Fluke has achieved some impressive results, but that is a long way from the real time monitoring I am speaking of. Enjoy;
Tom Knox 303-554-0307 [email protected] "Peace is not the absence of violence, but the presence of Justice" Both MLK and Albert Einstein ________________________________ From: volt-nuts <[email protected]> on behalf of Dr. David Kirkby <[email protected]> Sent: Thursday, October 31, 2019 6:48 PM To: Discussion of precise voltage measurement <[email protected]> Subject: [volt-nuts] Lab temperature stability required for X digit multimeters. I know before I ask this question that “it depends” will be part of any answer. However, I will ask it anyway. How stable does a lab temperature need to be maintained, in order to warrant using an 8.5 digit multimeter such as a 3458A? The same question for 6.5 and 7.5 digit meters. Dave. -- Dr. David Kirkby, Kirkby Microwave Ltd, [email protected] https://www.kirkbymicrowave.co.uk/ Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/volt-nuts_lists.febo.com and follow the instructions there.
