Body's capacitance? something of the sort. ----- Original Message ----- From: "Thomas McGahee" To: Sent: Tuesday, February 27, 2001 9:16 PM Subject: Re: [EE]: Infrared Detector vs Pet > About 4 years ago one of my students managed to get a sensor > donated (cosmetic defect) that I believe was a very large area > brown colored chip. Chip was about 1/2 inch square mounted in a > round package about 3/4 inch round with a top that was optically > clear. This thing had just two wires. I designed a simple > op-amp circuit that would respond only to changes in output. > I used a current to voltage coverter at the front end to get > maximum sensitivity. This thing was quite amazing. It was > extremely sensitive to the radiation emitted by humans. What > I found interesting was that it had no trouble at all detecting > a human through several layers of clothing, including heavy > winter coats. It did not seem to be "infra-red" detecting in the > sense that we normally use that word. It was sort of > tuned to the specific heat signature of the human body. It > could even detect this heat signature when the detector was > covered with a sheet of aluminum foil. In fact, one of our > major problems was preventing it from picking up signals > that were coming in from the sides (and even the BACK!). > > But it ignored squirrels. (Never tried it on a cat). > I don't think it was the fur that prevented detection, > because we had one person acting as our target who > had TWO very thick coats on, gloves, and two hats facing > with their back to the sensor, and they were easily > detected. > > Unfortunately I can't seem to find the project report in any > of my filing cabinets at the moment, but I vividly > remember how it could detect humans with great ease. > > It could be that the detector being touted by this company > actually responds to the specific human body signature, > just like the sensor in our project. > > Fr. Tom McGahee > > > ----- Original Message ----- > From: Sean H. Breheny > To: > Sent: Tuesday, February 27, 2001 3:40 PM > Subject: Re: [EE]: Infrared Detector vs Pet > > > > Hi Scott, > > > > Perhaps you are right, maybe the outer layer of fur is cool and obscures > > the inner layer. Also, I realized that my idea is a little messed up (you > > don't want a dead zone), and I don't have time at the moment to figure out > > if there is an optically feasible means to reject small objects :-) > > > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics