Running SN18 test for few weeks will show how stable is A3 ADC, and then it can be estimated if meter needs long running time. Waiting for weeks is typical when it comes to 8.5d DC measurements. There is no way around it , despite marketing efforts of various vendors. External reference is not required for SN18 test.
Also ignore test "limits" outlined in SN18 document, they are very wrong to judge stability of the ADC. Good meters must have drift less than 0.01 ppm/day, otherwise you just wasting money at expensive calibration which will be invalid before the next cycle arrives (assuming typical annual period). Good idea to keep ambient temperature stable (doesn't matter cold or hot, only deviation is important for SN18). Running meter continuously reduce thermal cycling induced stress , at expense of wee bit larger drift per year. Lower temperature reference also take care of that. On July 30, 2019 6:37:28 PM GMT+08:00, "Dr. David Kirkby" <[email protected]> wrote: >On Tue, 30 Jul 2019 at 07:03, Frank Stellmach ><[email protected]> >wrote: > >> // My serial number is: MY45044988 >> >> Hi Miguel, >> >> So it's now nearly 10 years old, and you should definitely save the >> content of the CALRAM, and maybe already change the DALLAS chips. >These >> might last another 5 years, but nobody can make sure. If it has been >> used for 7-8 years, maybe w/o calibration, its LTZ1000A reference has >> already drifted a lot, so a calibration is required.. >> >> Also the LTZ1000A reference might need some time to recover, because >it >> might show some hysteresis or rush-in effect after 2 years storage. > > >How long should he run it continuously to recover? Before sending it >for >calibration? > >If you want to get a proper calibration anyhow, you may also set the >> oven temperature lower, to 65°C as explained, and then send it out >for >> calibration. Or if you already have a stable external reference, you >can >> preliminarily copy the calibration after changing the oven. > > >How long should he run it continuously after changing the oven >temperature? > >I am guessing, (perhaps incorrectly), that there’s no point running it >continuously before changing the oven temperature if he intends >changing >the oven temperature. > >I’ve known Miguel for quite a few years - only by the Internet. I have >never met him in person. He doesn’t have access to any any stable >references, and I don’t think he would want to run air conditioning >24/7. >He can tell you how much the temperature varies throughout the year, if >he >has logged it, which I doubt. > >Being in Mexico, I don’t think there will be any local time nuts. > >I personally think that he would be better getting the meter calibrated >in >the USA rather than Mexico. He had been told it can be calibrated in >Mexico, but it would have to go to the USA to have the firmware >upgraded! >From a number of things he has told me about Mexico over the years, I >personally would not want to get anything done there. > >> >> Frank > > >Dave >-- >Dr. David Kirkby, >_______________________________________________ >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. BR, Illya Tsemenko _______________________________________________ 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.
