false alarm - glass break sensor

Old 02-04-04, 03:12 PM
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Red face false alarm - glass break sensor

so it's 2:00 in the morning, and my home alarm starts going off. I leap out of bed swinging & find the keypad displaying a glass break alarm. I inspect everything, find no problems, reset the alarm system & go back to bed. Just as soon as I reach a deep sleep again, the alarm goes off. Same thing. I end up turning the system off & try to get a little sleep.

Next day, with the alarm system turned off, I watch this particular sensor, and sure enough, it's going off time & time again. This is a hardwired system. The sensor itself is a Caddx 2000 (acoustical glass break sensor), the controlling key pads are napco gemini. I popped the cover off of the sensor hoping to find something obvious, but did not. There is no battery to go dead (hardwired), there is no sensitivity adjustment (auto adjusting), and the house is absolutely dead quiet, so there is no chance I'm setting this thing off.

I just purchased this home with the system already installed, and don't know when it was installed, but the home itself was only built in 2001.

I suppose it's possible that this is a bad sensor. But does anyone have any other ideas I should try before replacing it?

Any ideas from you guys in the "security" know?


Old 02-04-04, 08:35 PM
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one of the things to have checked is the connections at the power and alarm contact terminals. Over time, the wire gets compressed and is just loose enough to let the unit go into alarm. I've opened motions, glassbreaks, and smokes and gotten a full turn or more out of the terminal screws.

Another thing to check is the system power supply and backup battery. Especially if there are a lot of powered devices in the system (several glass breaks, keypads, smokes detectors, etc), a failing battery can generate false alarms like this (as can a failing power supply, but that's rarer).
Old 02-04-04, 10:02 PM
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Another thing to keep in mind is that glassbreaks not only detect the sound of glass breaking, but also the ultrasonic vibrations given off by a pane of glass breaking. So, anything that gives off these ultrasonic waves (or something similar) could be setting off the glassbreak - things like Heating and Air vents and units, one of the biggest problems. If the unit is mounted too close to a vent, it could be picking up these waves from the vent.

If you are watching the glassbreak and you can see the LED lighting-up, then the glassbreak is tripping - it's not a bad wire or connection. It could, however, be a bad glassbreak or short in the circuitry. But, it wouldn't hurt to check out the wiring and connections, just in case.

If it doesn't seem to be an outside source of falsing or the connections or wiring - there's only one thing left, bad device.

Good luck!

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