At first: there is absolutely no reason why internal calibration is not acceptable as long as carried out decently.
That said; without GUM, no decent traceable internal calibration is possible. So I suggest that you take a look at GUM first: http://en.wikipedia.org/wiki/Measurement_uncertainty Download tools: http://www.agilent.com/metrology/download.shtml > have a larger uncertainty and if this uncertainty is less than is acceptable the bottom line is that YOU decide what is acceptable. A common approach is to calibrate against the manufacturers specs, but if you can live with less accuracy (but traceable = known inaccuracy to int. standards) there is nothing wrong with that. If your measurement receiver is less than 0.5 dB accurate (say 1 dB), you will find out that this has a neglectable impact on the total inaccuracy on the total measurement setup for radiated emissions. Regards, Ing. Gert Gremmen [email protected] www.cetest.nl Kiotoweg 363 3047 BG Rotterdam T 31(0)104152426 F 31(0)104154953 Before printing, think about the environment. Van: [email protected] [mailto:[email protected]] Namens Andy Clifford Verzonden: Friday, November 13, 2009 10:15 AM Aan: 'Brian O'Connell'; [email protected] Onderwerp: RE: [PSES] equipment calibration process I don't know what GUM is, but the bottom line is that you should know the uncertainty associated with any test measurements you make, or at least be able to calculate it on demand. If the test equipment used has not be directly calibrated but 'cross calibrated' against a calibrated item it will have a larger uncertainty and if this uncertainty is less than is acceptable the only way around it is to have it directly calibrated. Procedures that address the above should satisfy 17025. Best regards Andy Clifford Conformance Ltd - Product safety, approvals and CE-marking consultants The Old Methodist Chapel, Great Hucklow, Buxton, SK17 8RG England Tel. +44 1298 873800, Fax. +44 1298 873801, www.conformance.co.uk Registered in England, Company No. 3478646 From: Brian O'Connell [mailto:[email protected]] Sent: 12 November 2009 18:31 To: [email protected] Subject: [PSES] equipment calibration process Good People, I am attempting to reduce instrument calibration cost/time for non-EMC related equipment. THe proposed process has the calibration contractor perform calibration of a set of 'master instruments' (so are directly traceable to NIST), and other instruments are internally verified using the 'masters'. The proposed process lists a hierarchy of instrument accuracy and precision, and specifies the ranges and scales for each verification of each instrument. Uncertainty is addressed, but GUM is not used. A verification is performed on a subset of the instrument's parameter set. IEC17025 mentions 'vaildated methods' and does not disallow this process; and neither is there anything that specifically recognizes this type of calibration system. My two basic premises are that the measurement uncertainty from a verification is logged at regular intervals, and the process will comply with the requirements list in 5.4.4. I am audited by three agencies and two agree, in principle, with the proposed process. The third does not concur. FWIW, my certificates have a narrow scope - most define of list of Type Tests for several product safety standards. Calibration is distant from my education and experience - so I would appreciate critical thoughts on the use of this as a process internal to a company lab. thanks much, Brian - 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - 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 <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
