Which detector technology is most effective for intruders moving across a field?

Which detector technology is most effective for intruders moving across a field?

• A. Microwave
• B. Infrared
• C. Ultrasonic
• D. Photoelectric

Answer: (B)

Detecting someone across an open field relies on sensing heat differences, not just motion or light. Infrared detectors pick up the radiant heat emitted by the human body, which creates a clear contrast against the cooler ground, grass, and sky of an outdoor setting. This heat signature is relatively distinct, so a person moving through the field tends to stand out, making detection reliable day or night. Other technologies either rely on waves or beams that can be disrupted by wind, rain, or vegetation, or require precise line-of-sight alignment across a wide area. By focusing on the warm body’s infrared radiation, infrared systems provide stronger, more consistent indication of an intruder moving across an outdoor field.

Detecting someone across an open field relies on sensing heat differences, not just motion or light. Infrared detectors pick up the radiant heat emitted by the human body, which creates a clear contrast against the cooler ground, grass, and sky of an outdoor setting. This heat signature is relatively distinct, so a person moving through the field tends to stand out, making detection reliable day or night. Other technologies either rely on waves or beams that can be disrupted by wind, rain, or vegetation, or require precise line-of-sight alignment across a wide area. By focusing on the warm body’s infrared radiation, infrared systems provide stronger, more consistent indication of an intruder moving across an outdoor field.