Types of motion sensors | Ultrasonic, dual motion sensor types

This describes different types of motion sensors with working principles. The motion sensor types viz. ultrasonic motion sensor, dual motion sensor, PIR and microwave motion sensor are explained.

Definition: As we know motion is a change in the position of object or person with respect to time and its initial reference location. The motion can be specified in terms of displacement, velocity, direction, acceleration and time. The device which senses motion is known as motion sensor.

Following are the types of motion sensors.
• PIR motion sensor
• Ultrasonic motion sensor
• Microwave motion sensor
• Dual motion sensor

PIR Motion Sensor

The figure-1 depicts PIR motion sensor type. PIR is the short form of Passive infrared motion sensor. As the name suggests it does not emit anything. It receives infrared energy emitted by human beings in order to determine their presence. This is due to the fact that, human beings radiate energy in the form of infrared waves. Hence there will be change in the thermal energy sensed by the PIR sensor. This is the principle behind working of PIR motion sensor.

It works effectively in LOS (Line of Sight) path with certain degree (usually 35 to 40 degrees) of coverage. It does not perform well in the night or dark conditions as well in slow motion conditions.
Refer basics of Infrared sensor and its working>>.

Ultrasonic Motion Sensor

The figure-2 depicts ultrasonic motion sensor type. This sensor generates ultrasonic waves with the help of ultrasonic crystal (usually 40 KHz). It has two parts transmitter and receiver. The transmitter converts electrical energy to ultrasonic sound waves and receiver receives echo back. It analyzes echo determine motion or presence of the object/person.

The ultrasonic motion sensor type is used in automatic car parking system as well as in the design of robotics.
Refer basics of Ultrasonic sensor construction and working>>.

Microwave Motion Sensor

The figure-3 depicts Microwave motion sensor type. This type of motion sensor transmits microwave frequency and receives the reflection of the same. It determines motion after analyzing frequency or amplitude change of the reflected microwave frequency. The coverage region of motion sensor depends on speed and size of the object/person and the location (or height) where sensor is mounted.

The advantages of microwave motion sensor type is life span and its working in harse environments. The disadvantages are its effect on health and are prone to false alarms under certain conditions.
Refer basics of Microwave Motion Sensor>> for more information.

Dual Motion Sensor

The motion sensor type which employs two different motion sensors in its construction is known as dual motion sensor. Refer Dual Motion Sensor Vendors>> for more information.

This guide on motion sensor basics and types of motion sensors will help to select the appropriate motion sensor for the need and applications of usage.

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