Shock Sensors are beyond doubt the main culprit when it comes to false alarms.
How many times have you got annoyed at a car alarm going off for no obvious reason?
More to the point, have you ever gone out to check and see if your neighbour’s car is actually getting broken into? If you did you’d probably not find a man in a balaclava hitting your car like an imbecile as shown in a recent video by AVS?
How do shock sensors work?
The most common impact sensor is the magnetic shock sensor. It is simply a magnet held by an elastic band which is suspended next to a coil. When the Magnet vibrates it induces electricity in the coil. This, in turn, triggers your car alarm to go off.
Sensitivity Adjustment
These sensors have a sensitivity screw which can be dialled up and down. This is used to adjust how much vibration is required before your alarm sounds. Some have a dual zone setting. The 1st zone being more sensitive will tell the alarm to chirp a couple of times as a warning should a small vibration be detected. The 2nd less sensitive zone will trigger a full alarm.
Why have a shock sensor?
The reason many people think they are a good idea is that they don’t want their car’s bodywork to get scratched or dented. The reality is that constant false alarms piss everyone off will probably be the motivation to actually take a key to your paintwork!
Here is a quote from a Mongoose installation manual:
Avoid over sensitivity as people nearby may not respond due to too many false alarms. (This type of sensor may not prevent wheel theft, we therefore advise the fitment of locking wheel nuts)
What will cause a shock sensor to trigger?
There are many things that can cause the sensor to vibrate. The environment the car is located is often a big factor. For example, a car parked in a multi-storey car park is very susceptible to the resonating frequency of motorcycle exhausts, or even loud car exhausts for that matter.
Why do so many alarms come with Shock Sensors?
First off is that they are cheap to manufacture. Secondly is a false notion that they will protect your car from getting damaged. The reality is there is not much that can be done to protect the outside of your vehicle without false alarms. If you want to protect your wheels then a tilt sensor will be far more effective.
What about Intelligent Shock Sensors?
I have read all sorts of marketing bullshit about “Intelligent” shock sensors yet they all have the same issues.
The reality is that a car thief is not going to bang on your windscreen to set it off. But I do know if a case where an installer has cracked a windscreen doing this very test.
Intelligent hey!
