Subject: Uncertainty Question RE1 Date: Thu, 11 Mar 1999 09:28:27 -0500 (EST) From: Greg Gogates To: iso25@quality.org Date: Wed, 10 Mar 1999 16:51:49 -0500 From: Murray Penney To: Greg Gogates Subject: Re: Uncertainty Question In response I would mention that the temperature varients that my men work in are far wider than that. As our test equipment is transported in the trunk of a car (winter & summer) and my men are requireed to service a LOT of instruments on one particular day, sometimes beside a shipping dock with doors opening & closing all the time (winter & summer) or beside a heat treating oven with the door opening & closing, ( or several heatreating furnaces doors opening & closing or water dripping on your head while performing the calibration), I can sympathize with your problem Greg Gogates wrote: > Date: Mon, 08 Mar 1999 03:26:59 -0600 > From: Mike Linn > To: Greg Gogates > Subject: Uncertainty Question > > I run a small calibration lab that is persuing A2LA accreditation. My question > revolves around reporting and calculating uncertainties for onsite calibrations. > In the lab with a stable environment and opportunities to perform long term > analysis, this is not much of a problem. > > I'll give an example of our delimma. We perform calibrations on temperature > controllers in various industrial environments, in this case the controllers > (130 of them) are located all over the plant in various environmental > conditions. A set of 3 controllers might be located under an air condition duct > where the temp might be 73 deg F, the next 3 or 4 might be in a panel right next > to an oven where the temp is 85 deg F. What is the best way to calculate and > report the associated uncertainties for these calibrations. Is it alright to > guestimate uncertainties over a range of ambient temperatures, ie +/- .5 deg F > for ambient temps from 68 to 72 F, and +/- .85 deg F for temps of 72 to 75F, > and so on? > > Also, what uncertainty should be reported, the uncertainty of the standards or > the combined uncertainty of the standards and the unit under test? > > Thanks > > Michael Linn > Johnson Controls, Inc.