Do (burglar alarm) glass break sensors work well?
I was thinking of buying some of that tape that sticks on the window that I recall from days gone by but now everyone seems to be selling what appear to be acoustic types.
Anyone any experience of these? What's their range? ie. Do you need one per pane?
Ta.
You appear to need one per pane from my exhaustive investigations. Ie waiting by window for sighted help for shopping in supermarket, and feeling said window and finding little things glued in corners.
I remember the foil stuff. I think it all depends how the glass breaks. Also of course very thick glass will need one hell of a thump to make it break one assumes. I have not researched this aspect.. grin. Brian
Their range is the pane of glass they are attached to. There used to be a problem that, despite film and TV FX, most glass does not actually make much noise when broken. I believe that has been improved in recent models and that they now also look for the noise made when glass flexes. Combining the two also overcomes another problem; that of false alarms from external noises.
However, a couple of strips of foil around a window is much more obvious and I think is more likely to deter a break attempt, which IMO is preferable to detecting one. These people still list it:
Colin Bignell
The glass break sensors RDS is referring to are not contact devices at all, they work off a microphone and microprocessor detects the signature of glass breaking in an appropriate way (apparently they only detect framed glass being hit)
e.g.
it says a range of 4.6 metres.
I think I would trust those even less to work properly, unless it were to cover something like plate glass, which is quite noisy when it breaks.
Colin Bignell
glassbreaks/468125.html
Belt and braces I think, i'll get one AND the tape variety.
Glass break sensors pick up the strong ultrasonic sound emitted when glass is broken, they seem to work quite well whether covering small or large windows.
Well easy enough to test out after installation.
Used to have one of the microphone types on the kitchen window, installed by the last owner with the rest of the alarm, i didn't even know the alarm was working, as we had no code so basically ignored it,
Then one day my GF dropped my favorite mug from the dishwasher, the second it smashed on the floor the alarm went off, making her doubly guilty of what she'd done :) And of course having no code to the alarm, we couldn't stop it until i located the central unit and removed the fuse and battery, and it was deffo the glass break detector that had triggered it, as the led on it was flashing like mad... it had always been off before.
She was convinced i'd rigged some sort of 'favorite mug being smashed' sensor to keep an eye on her, especially as she'd dropped a pint glass before and the alarm never went off, it took a lot of explaining for her to believe me it was just a fluke and that the glass break detector must be on the 24 hour circuit, hence will go off even without the alarm being set (she's one of these who dosent believe in coincidences, but does believe in ghosts, aliens and anything else her brain can't comprehend)
i guess the particular shape/angle of drop/material the mug was made of sounded just like a window pane being broken, but all the windows are double glazed units, which don't sound anything like normal glass smashing, so i'd figured the glass break detector was just an extra the salesman had added.... only one in the whole house, and located in the kitchen of all places.... window facing the road, why not in the living room with the french doors, panes of glass either side and another big window, all hidden round the back of the house.
Apparently not as easy to test as you might think, you can't just smash a bottle within range of it, or even a "loose" pane of glass, it has to be a pane of glass supported around the edges for it to trigger hence they make a window smashing synthesiser for test purposes ..
Mine triggered when something large fell onto the concrete floor whilst the carpet was being replaced (a flatpack steel shelf unit in its box), and also when a pigeon hit the window (I was out, but you could see the white dust ghost image on the glass).
You can make mine trigger by snapping your fingers in front of them a few times, but I suspect it's sensing that specially, rather than that it happens to have any characteristics of glass smashing. It's for testing the connection back to the alarm.
One of the makes I looked at (a long time ago) had a device to test the range from the window which looked like it used a tiny sping-loaded ball to hit the glass, which it listened for, but it warned not to try on toughened glass which lots of windows are nowadays.
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