Here’s a quick rundown on what car alarm sensors are available and what they actually detect. Click on each link for a more detailed explanation…
Door and Boot Switches
Most vehicles already have these fitted as standard equipment.
Part of my job as an installer is to check that they all work and make sure the alarm is wired up to them.
I make the effort to wire the alarm directly to the doors circuit rather then the interior dome lamp (especially if it is a faded time out type) so the alarm can warn you if you leave one open when arming it.
Detects the opening of the bonnet.
Should come as standard with all alarm systems and fitted if the vehicle has a bonnet.
Stainless or waterproof switches are best as rusty ones can cause a false alarm or simply not work at all.
Some vehicles already have factory switches built into the bonnet latch
Micro Switches can be used where a traditional bonnet switch is not practical to fit.
These are often used on caravan and motorhome doors.
I have them installed on the Obsessive van to protect against door folding!
These things give car alarms a bad name, especially in Wellington where even the wind can cause them to give a false alarm!
Oversensitive impact sensors are the biggest cause of false alarms. The can be set off by large vehicle passing, booming exhaust pipes and the wind.
I do my best to avoid installing them and turn the sensitivity down on systems that have these built in.
Level sensors learn what angle the vehicle is parked at when the alarm is armed. If it then gets jacked up the alarm will trigger.
Great for protecting wheels from theft or even the vehicle being towed.
Not prone to false alarms like shock sensors.
Glass Break Sensor
A Glass Break Sensor is a microphone that is tuned to detect the high pitched sound that a window makes when it gets smashed.
These are not effective if you have a large vehicle such as a van where the sensor is some distance from the sound source or if the vehicle has aftermarket window tint film.
Ultrasonic or volumetric sensors monitor the internal space inside a vehicle.
They consist of a transmitter which sends an ultrasonic sound wave around the cabin which in turn is detected by the receiver.
Passive Infrared Sensors (PIR Sensors) are good for protecting Ute Canopies and internal space in Motorhomes and Caravans.
They detect heat movement such as a human body coming into the detection zone.
A reed switch is a turns on and off when a magnet goes in and out of range.
These are useful when fitting a bonnet or door switch is not is not physically practical.
Great for Ute tray lids and caravan doors.
Microwave sensors are normally installed on soft top vehicles where ultrasonic sensor are not an option.
They detect a mass (such as a human body) entering the zone.
Closed Loop Sensors
Closed Loop Sensors are one of the most effective ways of protecting external items on a vehicle.
Accessories such as LED light bars, spotlights and winches are often easy targets which a closed loop sensor can help secure.
They trigger the alarm when the loop wire is cut so running the loop wire with the main cables is a subtle way to protect expensive equipment.
Wireless External Tilt Sensor
These are an easy add-on to an alarm and can be used to protect external items carried on a vehicle.
Great for roof boxes, cycles carriers or toolboxes carried on the back of a Ute.
The sensor knows what angle it is placed at when the alarm is armed and triggers the alarm if the angle changes.