Anyone heard of a 'mass sensor' which detects movement like a PIR sensor but only over a certain mass, meaning cats don't set them off?

Been offered some but never knew they existed so had always considered door and window sensors instead.

we used to have a system with a pressure pad under the carpet on the stairs. It was a good idea until the cat once got locked upstairs while we were out; the neighbours were not impressed.

Yep, have had some since 1999ish. Can't remember specifics but think they could be adjusted for cats or dogs. Something to do with size rather than weight I think as infra red can't do the latter surely. Whatever they did and do work so the cats don't set them off. Always worried about being burgled by a dwarf tho…… 😉

Some of the guys I work with have fitted them and they seem to be ok. It reduces alarm grading from 3 to 2 though, so I don't think you can have police response if you use them. IIRC the PIR has zones in the lens blanked out that normal ones use, including the creep zone underneath I think.

cheers guys

As already said we used to fit PIR's with a different lens pattern which cut off a few feet above the floor. We also used to occasionally fit ultrasonic sensors which could be used in this application but i think they were a lot more expensive.

However in my opinion a burglar alarm should be designed to stop scrotes getting into the house in the first place, this means shock or break glass detectors on all the windows and magnetic contacts on all the doors. Its not a cheap option however. PIR's etc will only go off once someone is already in the house.