That’s an interesting table, with some non-intuitive lessons. Platinum has an emissivity of 0.07, while water is 0.96! Hmm, ice has 0.97. Wait a minute, the table says all values of emissivity are taken at 300K. Are we talking about ice-9 here?
In the past, I have found IR temperature measurements were confounded by the small targets and wide spot sizes I was using. For instance, trying to measure the thermal rise of a 1 mil diameter platinum wire across a background of alumina, with a spot size of about 20 mils diameter. The detector would integrate the temp of the low emissivity wire and the much higher emissivity background, making the detection system fairly insensitive to the wire’s temperature excursions. Resolution was key to a good measurement, and I would love to see that experiment done again, but this time with a resolution so fine that one entire spot could be placed on just the wire. A thermal imaging camera ought to have quite sufficient resolution. In your example, a small difference in surface emissivity could easily make a 10C difference. I think you should put a dab of (I imagine they have a special) paint on your target locations. Ed Price ed.pr...@cubic.com <blocked::mailto:ed.pr...@cubic.com> WB6WSN NARTE Certified EMC Engineer Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 Military & Avionics EMC Is Our Specialty From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of jral...@productsafetyinc.com Sent: Wednesday, June 23, 2010 7:29 AM To: m.j.may...@ieee.org; EMC-PSTC@LISTSERV.IEEE.ORG Cc: 'John Yelencich'; mn...@productsafetyinc.com; 'Walter T Jurek' Subject: RE: [PSES] Utilizing IR Cameras for Temperature Testing What if thermal imaging was used vs a pin point IR gun? And, wouldn’t thermal imaging be better than a pin point thermal couple? We’ve measured a temp difference of 10C between two thermal couples on the same surface that were only 1/2 “ apart. So how do we handle emissivity today? Hopefully this link goes through the listserve – there are emissivity coefficients. Plastics is 0.91. Other materials are identified in on the link website. http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html Thoughts??? John Allen Product Safety Consulting, Inc. 605 Country Club Dr. | Stes. I & J | Bensenville, IL 60106 630-238-0188 | 877-804-3066 | 630-238-0269 (f) jral...@productsafetyinc.com www.productsafetyinc.com <http://www.productsafetyinc.com/> - 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.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 <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com>
