While both infrared sensors and microwave sensors function well as motion sensors, there are fundamental differences between them that allow each to excel in different conditions.
Infrared sensors operate by detecting heat. The sensor continuously fires off detection beams. It first measures the ambient temperature of the room to form a baseline. When a difference in temperature is detected by one or more of the infrared beams, the sensor activates the lights. When all the beams detect the same temperature again, the lights will switch off.
Microwave sensors operate by emitting microwaves, which bounce off surfaces and return to a detector within the microwave sensor. When these returning microwaves are disrupted by movement, the microwave sensor activates the lights.
The case for infrared sensors
In situations where there is a lot of small ambient movement that should not trigger the lights, infrared sensors may be the solution. An example is when lighting is installed in a factory; since machinery may be moving constantly, an infrared sensor would not detect the machine’s movements. Another example is if infrared sensors are installed in a lab containing reptiles, the cold-blooded animals will not trigger any lights, as they do not emit heat. For a more day-to-day example, a low sensitivity infrared sensor may be the solution for pet-owners in their homes, as pets with lower heat signatures would not trigger the motion sensor.
The case for microwave sensors
Microwave sensors are ideal for most other applications, as they are more cost effective, can detect through non-metal surfaces, and has up to a 360° detection angle, as opposed to only a 90° detection angle with an infrared sensor. Microwave sensors are commonly used in warehousing applications, as lighting fixtures in warehouses tend to be installed at high heights, and microwave sensors have a very long range of detection. Microwave sensors are also frequently used in hallways, gymnasiums, stadiums, and other commercial applications.
Here is a quick summary of the advantages and disadvantages of infrared sensors and microwave sensors.
|Infrared Sensor||Microwave Sensor|
|Positive||Can be used in areas with ambient motion Can be adjusted to be less sensitive Has a large detection range||360° range of detection
Can detect through non-metal surfaces, such as plastic and glass
Is more cost effective
Detection occurs in less than a microsecond
Very sensitive to movement Has a large detection range
|Negative||90° range of detection
May not detect motion when moving directly towards or away from the sensor
Is less cost-effective Does not detect through surfaces
|Very sensitive to movement
Detection occurs through non-metal surfaces even when not desired
Source: Arani Education Centre