How Do Motion Sensors Work- Part 2 Multi-Tech
Multi-Tech motion sensors use a combination of infrared sensing with technology that detects the motion of physical objects. The most common method is to use microwaves. The motion sensor transmits microwaves and then "listens" for a change in the echo by using the doppler effect. Only when a motion sensor detects the movement of heat between zones AND senses the physical movement of an object in the protected area will an alarm occur.
Honeywell's Duel-Tec Motions sensors and Bosch's Tri-Tech are very common. Bosch uses a similar IR/Microwave detection method as Honeywell, but they use Tri-Tech to highlight "First Step Processing", which reduces false alarms.
Unlike a "Passive Infrared Sensor" which only responds to the energy received, a duel tech device sends out energy. The amount of energy transmitted must be adjusted to the size of the protection area. Too much energy will result in room saturation and can either reduce the detection effectiveness or make it too sensitive. An installer should calibrate the microwave to the lowest level that still provides the detection protection desired. Refer to the motion sensor installation manual for each model you are installing.
Either motion detector will work very well in the right application. There are many brands and most are also very capable of providing years of service. Regardless of which brand you select, proper detection methods and installation location are the most critical variables in a false alarm-free installation.