On Wednesday, 23 November 2016 15:07:10 UTC, Dave Plowman (News) wrote:
In article ,
whisky-dave wrote:
Most obviously currently with pet insensitive PIRs.

what are pet insensative PIRs do ou really think a pets infra red foot
print is that difernt from a humans well it not. All these so called
PIRs do is lower the sensativity, if you set it to ignore 40KG animals
it wontl detect 40KG of a child either. You're just fooled by
adversising.

It's not unusual to leave a pet at home alone. A small child, not. Or
rather not in the sort of families I'm used to. You may have a different
experience.

Those that have animals of suchas a cat or dog make sure teh PIRs don;t cover the areas where the cat or dog will cross, or you can turn down the sensitivity
whiuch is where teh 40 or 80kg comes from the PIR still can;t tell if it's a cat dog or sprog, it'll just ignore something small.

https://en.wikipedia.org/wiki/Passive_infrared_sensor

The term passive in this instance refers to the fact that PIR devices do not generate or radiate any energy for detection purposes. They work entirely by detecting the energy given off by other objects.[1] PIR sensors don't detect or measure "heat"; instead they detect the infrared radiation emitted or reflected from an object.



Product design

The PIR sensor is typically mounted on a printed circuit board containing the necessary electronics required to interpret the signals from the sensor itself. The complete assembly is usually contained within a housing, mounted in a location where the sensor can cover area to be monitored.
PIR motion sensor design

The housing will usually have a plastic "window" through which the infrared energy can enter. Despite often being only translucent to visible light, infrared energy is able to reach the sensor through the window because the plastic used is transparent to infrared radiation. The plastic window reduces the chance of foreign objects (dust, insects, etc.) from obscuring the sensor's field of view, damaging the mechanism, and/or causing false alarms. The window may be used as a filter, to limit the wavelengths to 8-14 micrometres, which is closest to the infrared radiation emitted by humans. It may also serve as a focusing mechanism.

SEE NOT the PIR which is a fixed sensor you use other me methods the PIR can't tell ahuman from a dog.