Introduction
In cold climates, people wear heavy clothing that insulates body heat. This can reduce the infrared signal reaching the PIR sensor, making detection difficult.
Why Heavy Clothing Affects Detection
PIR sensors detect the infrared radiation emitted by a person’s skin and clothing. Heavy, insulated clothing:
- Blocks body heat from reaching the surface.
- The outer surface of the clothing may be near ambient temperature.
- Reduces the temperature difference between person and background.
Symptoms
- Sensor detects people in summer but not in winter.
- People wearing heavy coats are not detected until very close.
- Detection range decreases in cold weather.
Solutions
1. Increase Sensitivity
Turn sensitivity to maximum. This may help detect the smaller signal.
2. Use a More Sensitive Sensor
High-quality sensors with lower NEP (like Panasonic EKMB) can detect smaller temperature differences.
3. Use a Sensor with Better Low-Temperature Performance
Some sensors maintain sensitivity better at low ambient temperatures.
4. Focus on Uncovered Areas
If possible, aim the sensor at areas where people might have exposed skin (face, hands) – but this is difficult.
5. Use a Different Technology
Microwave or mmWave radar sensors detect motion regardless of clothing insulation, as they don’t rely on body heat.
6. Combine with Other Sensors
Use PIR in conjunction with a microwave sensor. The PIR can detect unclothed areas, microwave confirms presence.
Case Study: Arctic Research Station
At a research station in Greenland, standard PIR sensors failed to detect personnel in heavy Arctic gear. Switching to microwave sensors solved the problem completely.
Conclusion
Heavy clothing reduces PIR effectiveness. In cold climates, consider alternative technologies or combine with other sensor types.