Kevin, Most certifying agencies will provide information on their expectations for measurement uncertainty. The EMC people of this world can go on for ages about the topic, you will almost always see a workshop on this at the annual EMC symposium. For safety testing this usually does not come into questions unless you have measurements that are rather close to the limit. My personal experience is with setting up an ISO 17025 accredited testing lab and following the guidance from both ISO 17025 and ANSI/NCSL Z540.1. There is some math involved as well as decisions about the probability distributions.
The first thing you should check however, is if there is any interference. The J and K type thermonuclear probes do have iron (Fe) content and are susceptible to magnetic or RF fields. If you have such fields present they can result in a much wider range of readings than you might otherwise expect. Look for a sudden shift in temperatures when you switch power on and off. Using shielded probes or RTDs may be helpful. Also type T thermocouples have no iron content. In every case I know of, optical temperature guns are not acceptable for final readings in product certifications. From thermocouples you may expect an initial tolerance variance of about +/- 2 degrees (C). Any more than this and you should check your welding process and the quality of the attachment to the device being measured. If you are attempting to measure ambient air, you can expect more variation and sometimes placing the TC in a small vial with couple milliliters of oil will help to stabilize the readings, this of course will slow down response times. All the best, Doug On Tue, Sep 20, 2016 at 7:59 AM, Kevin Robinson <kevinrobinso...@gmail.com> wrote: > I was wondering if anyone was aware of any guidance documents that > provided acceptable levels of uncertainty when conducting various tests. > The specific measurement that I am interested in this case is temperature > measurements, but I would be interested in seeing other guidance for other > measurements as well (voltage, current, force etc.) > > I know the IECEE has published a CTL decision sheet on equipment accuracy, > but I was wondering if there was other industry guidance available. > > I have a situation where a product was subjected to a temperature test > three times by three different individuals using the same test equipment, > and the delta in some instances was nearly 12 degrees C (53.3 - 64.8) for > the same component. Just looking for some additional guidance documents or > standards that would help me convince the powers that be that such errors > are unacceptable. > > Kevin Robinson > - > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to < > emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > > Attachments are not permitted but the IEEE PSES Online Communities site at > http://product-compliance.oc.ieee.org/ can be used for graphics (in > well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > > For help, send mail to the list administrators: > Scott Douglas <sdoug...@ieee.org> > Mike Cantwell <mcantw...@ieee.org> > > For policy questions, send mail to: > Jim Bacher <j.bac...@ieee.org> > David Heald <dhe...@gmail.com> > -- Douglas E Powell doug...@gmail.com http://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
