About passive infrared sensor

There are two types of passive infrared sensors:

· Thermal infrared sensor

· Quantum infrared sensor

Thermal infrared sensors are wavelength independent. They use heat as energy. Thermal detectors have slow detection times and response times.

Quantum infrared sensors are wavelength dependent. They have high detection time and response time. These types of IR sensors require frequent cooling to make accurate measurements.

Applications of infrared sensors

IR sensors are found in most devices today. Below is a list of sensors named for their purpose.

Proximity sensor

These are used in smartphones to find the distance of objects. They use a principle called reflected indirect incidence. The radiation emitted by the transmitter is reflected by the object and received by the receiver. The distance is calculated based on the intensity of the radiation received.

Item counter

This uses the direct correlation method to count items. Maintain constant radiation between transmitter and receiver. Once the object cuts off the radiation, the item is detected and the count is incremented. The same count is shown on the display system.

Burglar alarm

This is one of the widespread and commonly used sensor applications. This is another example of the direct incidence method.

It works like an item counter, where the transmitter and receiver are located on either side of the door frame. When an object crosses the path, constant radiation is maintained between the transmitter and receiver, and the alarm is activated.

Radiation thermometer

It is one of the key applications of infrared sensors. The working of a radiation thermometer depends on the temperature and the type of object.

These have faster response and simple pattern measurement. They can make measurements without direct contact with objects.

Human detection

This method is used in intrusion detection, automatic light switches, etc. Intrusion alarm systems sense human body temperature, also known as infrared thermometry.

Set an alarm if the temperature exceeds a threshold. It uses an electromagnetic system adapted to the human body to protect it from harmful radiation.

Gas analyzer

Gas analyzers are used to measure gas density using the absorption properties of gases in the infrared region. Dispersive and non-dispersive gas analyzers are available.

Other applications

Infrared sensors are also used in infrared imaging equipment, optical power meters, sorting equipment, guidance, remote sensing, flame monitors, moisture analyzers, night vision equipment, infrared astronomy, railway safety, etc.

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