What is a passive infrared sensor?

Passive infrared sensor (PIR) is a type of optical device that detects wavelengths of light over human vision. Where human beings can generally see light from 400 to 700 nanometer wavelengths, infrared wavelengths spread across a very wide spectrum from about 740 nanometers to 300,000 nanometers or more in a distant infrared range. Most passive infrared sensor units, especially those built into safety systems, have optical filters that limit their intake to 8,000 to 14,000 nanometers, a range in which human bodies shine in infrared radiation. The PIR sensor technology was used in a wide range of residential and commercial remote survey applications, as sensors are cheap, long -term and very reliable. PIR sensors are often used because they are negotiating an electronic device that does not require any continuous electricity source. Acts as a kind of switch that is measured on the surrounding infra -redé light in their line. When the new heat source exceeds the path, such as the path of a human being or animal, they react as a switch, close the perimeter and turn on the alarm, faucet or other equipment.

Since they are able to detect such a wide range of infrared spectrum, special filters or lenses focusing light can be placed on top of the optical sensor detector to adapt it. They can therefore be optimized to ignore objects such as small animals or pets, and respond to larger objects such as humans. Often, small parabolic mirrors also integrate to expand their sensing range into a wider horizontal area for such use as automatic light switches when someone enters a darkened room. Freobjective Snell incorporated into a passive infrared sensor is a curved plastic foil hundreds of minutes of focusing prisms that can take weak withSigns received from multiple angles and direct them to one focus on the sensor detector for maximum acceptance.

The basic part of each PIR is a pyroelectric unit. This is basically a small metal mounting case for a crystal that responds to temperature changes by creating an electric current. The sensor is calibrated to ignore the radiation in the background from the infrared light in its environment and create a signal only when this level of radiation significantly increases.