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What are the Different Types of Motion Sensor Systems?

Amanda R. Bell
Amanda R. Bell

Home security systems generally feature three types of motion sensor systems. Such systems most commonly use infrared technology, though microwave and dual technology systems are also available. Each type has its pros and cons, though each also is an effective way to protect a home.

Infrared motion sensors are one of the cheapest and most reliable systems available. The sensors use the infrared light spectrum to measure the heat of objects that pass in front of them and then compares it to the surrounding objects, such as a wall. If the heat of the passing object is significantly higher than the objects behind it, the sensor will go off. Instead of covering a full room, infrared systems cover only scanned areas, although each sensor can be fitted with different lenses to cover greater distances.

A motion sensor alarm may be used to deter burglars from entering a person's home.
A motion sensor alarm may be used to deter burglars from entering a person's home.

Microwave motion sensor systems send out electromagnetic waves that bounce off an object and back to the sensor. The sensor then reads the frequency of the returning waves. If an object is moving, the sensor receives different microwaves than the ones it sent out, signifying movement and setting off the alarm. These types of systems cover a larger area than infrared sensors, they are capable of penetrating walls, and they are more reliable over longer distances. Despite this, they are the least popular option on the market because of their vulnerability to electrical interference and their cost.

Dual technology systems use a combination of infrared and microwaves to provide the most complete coverage available. Using both forms of technology allows dual motion sensor systems to reduce the occurrence of false alarms by combining the microwave technology’s coverage range and the infrared technology’s use of heat sensing. While not as common as infrared motion sensors, the dual technology system is rapidly gaining popularity among homeowners and businesses alike.

Infrared, microwave and dual technology systems all provide the same function, but each offers unique advantages and disadvantages. Each type of technology also provides several settings to allow the user to alter sensitivity in cases where a home or building has pets or a large amount of outside animals that may inadvertently set off the alarm. Proper installation of any of these systems will help a homeowner improve the security around his home.

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Discussion Comments


Does anybody know if an infared heater such as Eden pur can trigger a dual technology motion sensor? Thanks for any input.


From my recent experience, MrMoody's concern is valid. I just recently got to pay a $50 fine for a false alarm triggered by my infrared detector. My best guess as to the cause is that the detector is mounted on a wall near a corner with four windows and a nearby heat/cooling vent.

We had our hottest day in three years, so the sun warmed part of the room, the a/c was cooling the house and vaulted ceilings provided plenty of room for air to circulate. I can't have any more false alarms this year (earlier one due to faulty batteries) so now I hesitate to use the "away" feature at all.


I lived in a house that I rented that had a security system once and I must say I liked having the comfort of the knowledge that anything entering our home while I was there or away was going to be detected until...

...the alarm actually went off while I was home! Talk about scary. And yes it was still better than not knowing if something was in the house, but I would suggest making a plan in your head of what you or your roommates will do if someone enters your house and is not scared off by the alarm.

Luckily the reason for my alarm going off was kind of funny, I had a balloon in my house from a party I had, which had moved at some point to set the alarm off!

Also something to think about when you do choose which motion sensor system you want - be wary of balloons once installed!


@hamje32 - I agree. I think the motion sensor we have in our home is infrared, and I definitely see the infrared detector as a better alternative to the microwave sensor.

Nowadays you can get interference from all sorts of household devices which would compromise the integrity of the microwave sensor. Infrared, however, is a totally different story. How many of us have infrared devices lying around?


@MrMoody - I’m not a scientist, but I would venture to say that the situation you describe would not create a problem.

A general wave of heat wouldn’t have the precise signature that an object would have; these are, after all, motion sensors, not heat sensors. I would think that the infrared motion sensor would focus on a differentiating between a passing object with concrete size, dimension and velocity and a heat wave, which tends to be more undefined.

That’s as deep as I can get with the details, but I accept the article’s claim that this is actually a more accurate and reliable sensor than the other kind.


That’s the first that I’ve heard of infrared motion sensors, but I see what I think is an obvious design flaw (or vulnerability).

Since it’s based off of differences in heat, what about if there are heat changes in the atmosphere that are not triggered by motion?

What if there is a sudden blast of heat coming from somewhere for example? Won’t that trigger the alarm? Perhaps I don’t understand the technology well enough, but just at first glance, anything based simply off of heat variances seems subject to false positives, in my humble opinion.

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    • A motion sensor alarm may be used to deter burglars from entering a person's home.
      By: Robert Hoetink
      A motion sensor alarm may be used to deter burglars from entering a person's home.