False alarms on shock sensors in series

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  #1  
Old 07-11-06, 08:05 AM
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False alarms on shock sensors in series

Hi i wish i could get some help on this situation where i have about 20 shock sensors aligned in series on one zone. The problem is that i am getting a random false alarm about four or five times a week and i know that it is one of the shocks but i cant tell which one exactly. Is there any way to test because i dont want to change all of them. Thanks alot for any help
 
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Old 07-11-06, 07:27 PM
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That's because you have too many shock sensors on a single loop.

Unlike most alarm devices, piezo shock sensors have a resistance (12-20Ω on average) The instructions on the Sentrol 5150, one of the most common ones, specify no more than 10 per loop. I try to stay at 6-8 because of the wire resistance of the zone wiring.
 
  #3  
Old 07-12-06, 09:08 AM
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False alarms

Thanks for the reply but these are not the piezo type of shock sensors, they have a metal ball inside which moves when shaken, and they seem to have been there for over ten years. Maybe i should switch to the piezo type. Thanks again
 
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Old 07-12-06, 03:15 PM
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Ah! the old kinetic shock sensors.....

Hmmmm...That's definitely considered an obsolete technology. They have many of the same problems as the piezo sensors, I'm actually amazed that you were able to go so long without problems with that many of them on the same loop.

In my area (a college town) a kid with a heavy bass car stereo would have long ago tripped a ton of false alarms with those.

If your loops were wired as home runs, and you have a zone or two open, with the ability to configure it, you might be able to split them up and gradually switch them over to the newer shock sensors. Upgrading/replacing this kind of older hardware can be kinda tricky.

If you have the "bouncing BB" style of shocks, what eventually happens is that the mating surface for the mechanical contact starts getting pitted, and the spring the maintains the closed loop starts getting weak. It's really tough to figure out which single one or two is causing your problems.
 
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Old 07-12-06, 04:05 PM
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False alarms on shocks

Thanks for the reply and i know that these shocks obsolete but there are so many of them on one loop that it will be tough but i cant find another solution. I would like to know if there is some type of accessory that can minimize the sensing on the shocks. Thanks a mil again
 
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Old 07-12-06, 05:14 PM
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No there is none. The sensors are really just a simple mechanical switch, and the second law of Thermodynamics can't be repealed. Sooner or later, entropy gets to win.

The alarm input looks for a specific resistance value in the loop, and if the resistance goes above a certain amount, it's considered open and the alarm is triggered.

If you have ready access to the wiring at the sensors, you could try bridging each one with a set of alligator clips, one at a time until the false trips stop (the chime feature on most alarm panels is useful for doing this without actually arming the system).
 
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Old 07-12-06, 07:42 PM
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false alarm shock sensors

Again thanks for all the help and thats actually what i am doing, using the chime feature and bridging them one at a time. Thanks again
 
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