What Is a Pyroelectric Infrared Sensor?
Pyroelectric infrared sensors apply a physical phenomenon called the pyroelectric effect to infrared detection.
It is a sensor that detects heat generated from the human body or an object as infrared rays and captures the heat source.
The pyroelectric effect is a phenomenon in which polarization occurs inside a solid when heat is applied to ferroelectric material. Silicate minerals and tartaric acid are used as materials.
Pyroelectric infrared sensors have been adopted in many countries and are used as sensors in security alarms and motion detectors.
Applications of Pyroelectric Infrared Sensor
Pyroelectric infrared sensors are devices that detect infrared radiation emitted by heated objects, allowing them to identify the heat source, such as a person or object.
Compact, high-performance pyroelectric infrared sensors are widely used in a variety of situations where sensors are required.
There are many examples of the use of these sensors, mainly as intruder alarms for crime prevention and as motion-sensitive illuminators.
In recent years, pyroelectric infrared sensors have also been used in general households to detect people in air conditioning and heating equipment, televisions, and IoT devices.
Principle of Pyroelectric Infrared Sensor
The pyroelectric effect is a phenomenon in which an electric charge is generated by the polarization of molecules on the surface of a dielectric crystal when it is heated.
As the temperature rises, the polarization inside the dielectric responds immediately, and the constituent molecules respond as the polarization relaxes.
However, surface charges cannot respond as immediately as molecular polarization. Charges appear on the surface of the dielectric only as the polarization relaxes.
When a high-impedance load is connected to the electrodes on both sides of the dielectric, a current flows between the electrodes (called pyroelectric current). This pyroelectric current is used to detect the charge generated on the surface.
Since the pyroelectric current is generated when a temperature change occurs, it functions as a sensor when external thermal energy is applied.
Infrared light emitted from an external heat source is focused onto the sensor by an optical lens called a Fresnel lens. Optical filters are also used to avoid the effects of sunlight and illumination.
The output from the sensor is transmitted through an amplifier to increase the signal strength, which is then detected as a waveform.