How Do I Choose the Best Infrared Sensor?

The pyroelectric infrared sensor introduces a field effect tube in the structure, and its purpose is to complete the impedance transformation. Since the thermoelectric element outputs a charge signal and cannot be used directly, it needs to be converted into a voltage form by a resistor. Therefore, the introduced N-channel junction field effect transistor should be connected to a common drain to complete the impedance conversion. The pyroelectric infrared sensor is composed of a sensing element, an interference filter and a field effect tube matcher. When designing, the high pyroelectric material should be made into a thin sheet with a certain thickness, and metal electrodes should be plated on both sides, and then electrified to polarize it.

Pyroelectric infrared sensor

The pyroelectric infrared sensor introduces a field effect tube in the structure, and its purpose is to complete the impedance transformation. Since the thermoelectric element outputs a charge signal and cannot be used directly, it needs to be converted into a voltage form by a resistor. Therefore, the introduced N-channel junction field effect transistor should be connected to a common drain to complete the impedance conversion. The pyroelectric infrared sensor is composed of a sensing element, an interference filter and a field effect tube matcher. When designing, the high pyroelectric material should be made into a thin sheet with a certain thickness, and metal electrodes should be plated on both sides, and then electrified to polarize it.

Chinese name

Pyroelectric infrared sensor

Foreign name

PassiveInfrared Ray, PIR for short

Advantages

Does not emit any type of radiation itself

Missing point

Easy to be interfered by various heat sources and light sources

Nature

A material with high thermoelectric coefficient

It is mainly composed of a material with high thermoelectric coefficient, such as lead zirconate titanate series ceramics,

Because the polarized voltage is polarized, the polarized detector element also has positive and negative polarity. The sensor connects two detector elements with opposite polarities and consistent characteristics to eliminate interference caused by changes in the environment and itself. It uses the principle that two interference signals of opposite polarity and equal magnitude cancel each other internally to make the sensor compensate. For infrared radiation radiated to the sensor, the pyroelectric sensor focuses the Fresnel lens on the front of the sensor and adds it to the two detection elements, so that the sensor outputs a voltage signal. The high pyroelectric material used to make the pyroelectric infrared detector is a broad spectrum material, and its detection wavelength range is 0.2-20um. In order to have a higher sensitivity to infrared radiation in a certain wavelength range, the sensor is equipped with an interference filter on the window. In addition to allowing infrared radiation in certain wavelength ranges to pass through, this filter also blocks lights, sunlight, and other infrared radiation. ^[1]

Advantages: It does not emit any type of radiation itself, the power consumption of the device is small, and the concealment is good. Low price.

Prevention of small animal interference: The detector is installed at the recommended use height, and generally does not generate an alarm for small animals on the ground within the detection range.

Anti-electromagnetic interference: The anti-electromagnetic interference performance of the detector meets the requirements of 4.6.1 in GB10408. Generally, the electromagnetic interference of mobile phones will not cause false alarms.

Anti-light interference: the detector is within the range of normal sensitivity, and it is illuminated by H4 halogen lamp 3 meters away from the glass, and no alarm is generated.

The detector should avoid direct sunlight, car headlights, and incandescent lamps, and should not face heat sources (such as radiators, heaters) or air conditioners to avoid false alarms caused by large changes in ambient temperature; the detector must be installed firmly To avoid false alarms caused by wind and shaking; the surface of the sensor is not allowed to touch by hand; the outer surface of the optical lens should be cleaned regularly with a damp soft cloth or cotton to prevent dust from affecting the sensitivity; installation height 2m.

Special mention is that the detector circuit board has been debugged at the factory to ensure that the detection distance is greater than 6m. If there is a problem with the entire alarm system, please do not adjust or modify this part of the circuit, otherwise the detection distance cannot be guaranteed. ^[1]