Difference between Radar motion sensor and PIR motion sensor

This page compares Radar motion sensor vs PIR motion sensor and mentions difference between Radar motion sensor and PIR motion sensor including their advantages and disadvantages.

Introduction: The sensing device which senses motion is known as motion sensor. Motion can be defined as change in position of the object or person in time and with respect to its initial location. Motion can be specified in various aspects such as displacement, direction, velocity, acceleration and time.

The motion sensors are designed using various sensing devices such as PIR (Passive Infrared) sensor, Ultrasonic sensor, Microwave sensor, tomographic sensor and combination of these sensors. All these sensors are used for various use cases such as indoor lighting, smart street lighting, automatic door, intruder alarm etc.

Radar motion sensor

This motion sensor type uses microwave frequencies and work as per radar principle. It emits the electromagnetic (EM) frequencies in microwave band and collects the reflected EM frequency waves to analyze various parameters. It is also known as radar motion sensor due to its similarity with radar. It works with wider angle compare to PIR sensor.

The radar motion sensor derives speed or velocity from doppler shift in frequency. It derives angle or direction of the target from phase difference between EM received at the antennas. The range of the target and its position can also be determined from electromagnetic waves.

Advantages:
➨It can be used in harse environments.
➨It has more life span.
➨It offers higher detection range (~ 10-50 meters) than PIR sensor (~10 meters) .
➨It detects direction of travel so door opens when necessary.
➨Precision object identification.
➨It reduces false alarms.
➨It is more sensitive than PIR sensor.
Disadvantages:
➨It is expensive.
➨It works at intervals instead of continuously.
➨It consumes more energy than PIR sensor.

PIR motion sensor

This motion sensor type uses infrared waves radiated by objects or persons to determine their presence. PIR sensor uses pyro-electric sensor. It detects increased thermal energy when humans or animals come in LOS path compare to ideal condition (i.e. no presence). It works in Line of Sight (LOS) with certain range (~ 35-40 degrees).

Advantages:
➨It is very cost effective.
➨It detects motion indoors usually in day or dark.
➨It consumes less energy than radar sensor.
Disadvantages:
➨It does not work in night and dark conditions outdoors. It is unreliable in harsh weather conditions.
➨It does not detect slow motion.
➨It does not operate greater than 35 degreeC.
➨It operates effectively in LOS path and has problems in corner regions.
➨It detects movement only, irrespective of person coming into building. It can not distinguish between people and animals.

Tabular difference between Radar motion sensor and PIR motion sensor

Following table mentions difference between Radar motion sensor and PIR motion sensor.

Comparison Parameter	Radar Motion Sensor	PIR Motion Sensor
• Sensor type	Active	Passive
• Waveform	It uses EM (Electromagnetic) waves.	It uses infrared waves.
• Detection range	More than PIR	Less than radar sensor
• Resolution	Best	Good
• Identification	Very precise	Not very precise
• Penetration of materials	Microwave signals used in radar sensor penetrates better than infrared rays.	Penetration in the material is poor.
• Resistance to moisture, dirt and temperature	Better	Not so good
• Speed detection	Best	Weak
• Accuracy sensitivity	Best	Weak
• Cost	Expensive	Cheaper

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