Accuracy and 1 Year Uncertainty, What are they? When do I use that spec? - Page 1
Forum section: electronics / general

author: ttttrigg3r
author_rank: Contributor
timestamp: September 02, 2021, 12:58:23 am
content: Greetings all. I've come across many mfg datasheets and certificates. This example shows an Accuracy spec and 1 Year uncertainty. When I ask for a calibration certificate for this UUT from the mfg, I see that they tested using the tolerances derived from the 1 Year Uncertainty. It would make more sense to me to use the Accuracy spec. My question is what is the difference between these two, and when do I use them in performance testing?

author: bdunham7
author_rank: Super Contributor
timestamp: September 02, 2021, 01:01:38 am
content: There are footnotes that we can't see. Could you just post the whole page and let us know what the device is?

author: RYcal
author_rank: Contributor
timestamp: September 02, 2021, 04:42:38 am
content: Without knowing those footnotes I'm just guessingBut I'd say that the Accuracy reflects the instrument without any accounting for traceability and the 1y unc includes uncertainty if it was calibrated by the manufacture. Kind of looks like what Keysight/HP do with the 3458A specs.BUT I'm just guessing here so if I'm wrong or I didn't account for quantum physics please forgive me. Or if my reply seems kindergarten in nature its because of the limited information provided.

author: mzzj
author_rank: Super Contributor
timestamp: September 02, 2021, 05:28:21 am
content: Looks like Beamex specificationsFootnote probably says: Uncertainty includes reference standard uncertainty, hysteresis, nonlinearity, repeatability and typical long term stability for mentioned perioid.IIRC this should also include temperature stability between 18...28 Cel.You could find arguments for one way or other to which one the tolerances should be compared in calibration certificate.Maybe for a new product(1st calibration) it should be accuracy specification and for old product without re-adjustment the 1-year uncertainty.Beamex seem to always compare to 1-year specification but new products on 1.st cal are usually way more better than that.

author: e61_phil
author_rank: Frequent Contributor
timestamp: September 02, 2021, 07:34:39 am
content: Quote from: RYcal on September 02, 2021, 04:42:38 amThe 3458A datasheet provides only relative specs. You have to correct that against your cal sheet and/or add the cal uncertainty to the datasheet uncertainty of the 3458A. Some manufactureres (Fluke for example) are providing relative AND absolute specs. Only the absolute specs include the calibration (when properly done according to the calibration manual).

author: ttttrigg3r
author_rank: Contributor
timestamp: September 02, 2021, 07:22:22 pm
content: @ mzzj, YES! It's a Beamex MC6.It's a handheld calibrator with super accurate specs and great range.Here's the frequency. I'm struggling with coming up a standard for the freq measurement and generation tests. What standards go down that low?

author: RYcal
author_rank: Contributor
timestamp: September 02, 2021, 08:24:13 pm
content: I just had quick look at the specs at 10 Hz against my 5522A and 8588A. They seem both to be able to calibrate it well enough at 10 Hz. Perhaps the current might not be good enough from the 5522A but then I could use the 8588A as my reference in this case.I have calibrated tons of these in the past. Last lab I worked in we used an Aim-tti TF930 as a frequency reference.On the topic of Beamex's if anyone can work out how to remotely obtain readings via MET/CAL I would be willing to part with some money for the know how. There is a program you can download from Beamex that allows you to control them via a PC using a USB cable so it must be possible.