--0__=FRW1dgemTYYxa21tDnZv0jl934oObWVaok8pGRjHMNH5zrqBI7fXsOQ1 Content-type: text/plain; charset=us-ascii Content-Disposition: inline Just some more observations on color: I have several PIR sensors controlling lights in my basement. I have 2 winter coats that I store in the basement: one black and one grey. When I wear the grey coat, the PIR sensors all work fine. When I wear the black coat, I have to jump up and down and wave my arms to get the PIR sensors to activate. The black coat is not nearly as heavy and warm as the grey coat.... I guess its time to get a far-IR viewer to see whats going on! |--------+---------------------------> | | Olin Lathrop | | | | | | | | | 02/28/01 08:09 AM| | | Please respond to| | | pic | | | microcontroller | | | discussion list | | | | |--------+---------------------------> >----------------------------------------------------------------------------| | | | To: PICLIST@MITVMA.MIT.EDU | | cc: (bcc: Scott Touchton/US/UNIPHASE) | | Subject: Re: [EE]: Infrared Detector vs Pet | >----------------------------------------------------------------------------| > > As an aside, black objects are better thermal radiation (black > > body) emitters than white objects. This is a common miscon > > ception because black objects are also better thermal radiation > > absorbers. > > In the case of fur, colour is not the determining factor - it's how > much heat gets to the surface from the body. Although a black > fur next to a white fur on a sunny day would look hotter because > the sun heat it was absorbing at its surface I agree. The only reason I brought this up is because the original poster made a special point of the fur color. As an additional aside, some animals seem to have evolved fur that have special properties with respect to IR and visible radiation. Polar bears are being studied for this. You may need a different IR sensor if you live in an igloo ;-) ***************************************************************** Olin Lathrop, embedded systems consultant in Devens Massachusetts (978) 772-3129, olin@embedinc.com, http://www.embedinc.com -- http://www.piclist.com hint: The PICList is archived three different ways. 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