Yes. Emissivity is not the same as reflectivity. An ideal black object ("black body") would absorb all radiation shining upon it. In order to not violate the laws of thermodynamics, it must also EMIT the same amount of thermal radiation (otherwise, if in a vacuum, it would just get hotter and hotter and absorb all the energy in the surrounding area). So, black is actually the color which EMITS the most IR radiation due to its own temperature. Sean On 5/23/07, Richard wrote: > Emissivity of 100%? Black? > > ----- Original Message ----- > From: "Brooke Clarke" > To: > Sent: Wednesday, May 23, 2007 12:46 PM > Subject: [EE]: Cheap thermal imaging > > > > Hi Vitaliy: > > > > I measured part temperatures some decades ago by using a Barnes > Engineering IR > > thermometer. It came with a microscope and read the temperature at a > point > > source. But you only get correct readings if the emissivity of the object > is > > 100%, i.e, if it's black. So shiny things like metal transistor packages > need > > to be painted flat black or you need to know what emissivity number to > dial > > into the Barnes instrument. > > > > I think you can now buy a reasonably low cost thermopile type IR > thermometer > > that has a narrow (maybe 10 deg) look angle (most of them are 1:1 angle > types) > > that could be rigged up to do a similar thing. Remember that the single > pixel > > will report the integral temperature of what it's seeing so you want it > seeing > > only the hot part and not any background that's cooler. > > > > There are also some line and small number of pixel (maybe 64) imaging > chips > > commonly used for robots and it may be that the view angle for one of > these > > pixels would be small enough to be useful. > > > > -- > > Have Fun, > > > > Brooke Clarke > > http://www.PRC68.com > > http://www.precisionclock.com > > > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist