The Different Types of Motion Sensors

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We have all encountered different types of motion sensors, some of which we don’t really take notice of. For example, remember those automatic doors inside the mall? Well, it turns out it isn’t magic that makes them open and close when you go through it; instead it’s through the use of motion detectors. There are primarily 5 kinds and you’ll want to know about them before you decide to install one either for the security of your home or for other purposes.

1) Continuous Wave Radar Motion Detector (CW)

If you thought that that the only use of microwaves is to heat up your pre-cooked meal, then you’re not getting the most out of modern technology and need to get updated right away, especially if you’re looking into installing any type of motion sensor.

Continuous Wave or CW motion detectors use microwave signals to send out frequencies that bounce on and off an area. For this reason, there are commonly referred to as microwave motion detectors. What a CW motion detector primarily does is to detect any subtle changes within the frequencies that it sends out, this would create a disruption thus possibly triggering off an alarm.

Say for example that an intruder walks through the playing field of a CW motion detector, he will cause a disturbance within the microwaves which in turn will set off the sensor’s alarms. CW motion detectors are more expensive than PIRs, and for good reason as they are much more sensitive and are reliable over longer distances.


2) Passive Infrared Motion Detector (PIR)

As a popular choice for many people who install motion sensors,the  Passive Infrared Motion Detector or PIR is the most widely used of this kind of technology to date. Reason number 1 being it is the most affordable, or to be blunt about it, the cheapest motion sensor you can buy when compared to other detectors that utilize different technologies.

A PIR works through the use of an optical collection system in tandem with a couple of other sensing elements. Basically, it measures changes in the energy within it’s surrounding area. The sensor of PIRs recognize thermal infrared images created in combination with a heat sensor which sends off an alarm signal to it’s reciever. The security or control panel handling the unit can then interpret this signal and decide on which the appropriate alarm to trigger is.

The downside of using PIRs is it’s susceptibility to false alarms due to its sensitivity to environmental changes such as sunlight and hot to cold temperature changes. They are also defenseless against any item that blocks body heat emission meaning if someone is wearing a heat insulating full body suit and passes directly within the motion sensor’s vision it will detect nothing and no alarm will be triggered.

3) Ultrasonic Motion Detector

With the technology present in today’s motion detectors, it wouldn’t be surprising to have one type that uses sound energy to do its job. The Ultrasonic Motion Detector or UM does exactly this. By using ultrasonic sound energy which is emitted in waves, it detect movement in a designated area. This energy comes from quartz-crystal transducers. When movement is detected the sound waves are disturbed at the same time, triggering the sensor to ring off the alarm.

UM detectors are most widely used for automated doors. They are very reliable and don’t cause headaches when needed to be installed. There is however, a downside to this type of motion sensor: it is easily blocked and disrupted. It probably would be best not to use this kind for high intensity security measures.

4) Vibration Motion Detector

Also known as Piezoelectric, a Vibration Motion Detector is actually something you can put together at home with common materials. You can do a quick online search and feel like an engineer in a few minutes. Basically, most vibration motion sensors use the piezoelectric effect or in layman terms the ability of objects to create an electric field to detect motion. There are tons of how-to instructional write ups and even videos you can find to create a DIY version vibration motion detector.

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