Function

• An electronic motion sensor or detector contains a motion sensor that turns motion into an electric signal, when it is detected. This is made possible when the acoustical or optical changes in the sensor's field of view changes.
  Electronic motion sensors can be connected to burglar alarms. They are used to alert the homeowner of motion in or outside the home, when it is detected. In some cases, a security service may be alerted, if the homeowner has the sensor set up to automatically alert the security company that installed it.
  
  

Types

• There are three types of sensors used in the motion detector category. They are: Microwave, passive infrared sensors (PIR) or ultrasonic.
  The microwave sensor measures the reflection moving objects after it sends out microwave pulses. The best example of a microwave pulse is that used in police radar guns.
  The PIR sensor does not emit any energy from the sensor, but instead looks for body heat.
  The ultrasonic sensor works much like the microwave; it measure a moving object's reflection and sends out pulses. However, the are not microwave pulses.
  
  

Benefits

• Because of the advancement of technology, a variety of modern motion sensors use different technological combinations that reduce false alarms, when connected to security devices.
  Most companies are offered the option of using Microwave/PIR motion detectors that feature functions that are "pet immune." This means that wireless sensors will ignore pets that weigh up to 40 lbs., while hard-wired models will ignore pets that weigh up to 80 lbs.
  
  

Considerations

• When we think about motion sensors, we typically think about alarm systems and motion detecting lights, however, automatic doors in the library and grocery store also work off of motion sensors.
  Depending on who manufactures the sensor, they can work off of any of the three types of sensors mentioned in Step 2. The sensor is typically connected to the door mechanism that opens and closes it. When motion is detected near the doors, the sensor sends a signal to the mechanism and the doors open. Once the motion is no longer detected, the doors close.
  
  

Warning

• If you choose to put motion sensor lights outside of your home for security purposes, make sure that they are the variety that features the pet ignore option. If not, pets who stay outside will constantly set the lights off throughout the night as they walk around your yard.
  In addition, some motion sensor lights are so sensitive that cars passing by on the road can set them off if you live near a road or highway. That is something to keep in mind, as well.