I have a SecureLink system with a couple Visonic motion detectors which are supposed to ignore dogs up to 85 pounds. The other day one of the motion detectors triggered (while the system was alarmed) although no one entered the house through any doors or windows. There is evidence that someone broke through our locked yard gate. Could the motion detector (which has a clear view of the window to the outside) have triggered when someone walked by the window?
I have tried to trigger the motion detector from outside the window without success.
So, the question is if the detector can see through the window?
PS: There is a cat in the house but I can't imagine it set of the detector. Especially when someone definitely broke through the locked gate near the window.
IR cannot see through closed glass. However, it can pick up changes in the temperature of the glass due to changing atmospheric conditions outside, and it can see 'through' an opened window. You don't want to aim an IR unit at a window or a heating duct because of the risk of unintended operation.
Thanks for the info. I figured the IR detector couldn't see through glass. My two motion detectors are not aimed directly at windows but houses have lots of windows so there are some in the view of the detectors. We've never had one trigger unexpectedly before (the system has been in place for more than 5 years). I guess we'll have to believe the cat somehow did it. The cat is just visiting for a couple weeks so we'll keep it corralled in another room when we're out.
And, maybe it's time to change the batteries in the detectors. They haven't said they are low but it has been a bit over 2 years since they were replaced.
You normally also have a Stay option on security systems that turns off interior motion detection and alarms only if the perimeter sensors are violated. That's the traditional fix for temporary changes like that.