Jinx wrote: >> Can you rent ? You might find it more economic in the long term At a first search, I haven't found a valid renter but I'm still on getting informations.. > You'd need a pretty good (Fresnel) lens for detection at 600ft... Jinx, I intended the use of PIR only as "handheld" sensor (better, fixed on the helmet) while walking on the terrain, and so the distance from ground is 6 feet max or even less. Usually these surveys are done walking as much as possible along the mountain flank at the same altitude, then climbing up for a while and walking again but in reverse, and so on... In this mode one can accurately survey a large area (yes, tedious!) and is easier to "cross" a cold flux of air exaled by an eventual fissure sited few meters over. When outdoor is warm, I have noticed that is easy to sense these cold air movements even at a distance of tens of meters because the cold air silently slip low along the slope. So orientation the sensor in the right sense, probably it woud have to detect a warm -cold transition that maybe enough for triggering if temperature difference is sufficient... well, some practical tests will be necessary. thanks!! Marco ----- Original Message ----- From: "Jinx" To: "Microcontroller discussion list - Public." Sent: Wednesday, April 01, 2009 11:06 PM Subject: Re:[EE] Temperature detection with a PIR sensor >> In case (1) I was considering a Thermal IR Camera but price is still >> excessive for me even for low-end models > > Can you rent ? You might find it more economic in the long term > >> Case (2) approach is the reason for which I have asked for the PIR >> sensor: walking with the PIR looking in ahead, and wait it triggers (a >> led or a sound) when sensing a temperature difference > > You'd need a pretty good (Fresnel) lens for detection at 600ft, plus > all the intervening air currents and sensor movements would be quite > disruptive > > Another issue is the orientation of the sensor. PIR sensors have two > piezo bars. In horizontal orientation it's like an =. The sensor's > built-in > amplifier outputs a difference signal, as first one bar detects PIR, then > the other, as a body moves across the field of view. The maximum > output is when movement is perpendicular to the bar's orientation. ie > a = orientation will best detect vertical movement. That suggests you'd > need more than one sensor, in various orientations, to get maximum > response if you expect these air movements to be at unknown angles > -- > 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