Detector

A detector is a device that senses the occurrence of a phenomenon, event, or the presence of a substance and converts it into a measurable signal. Detectors are often distinguished from sensors by focusing on the detection of discrete events or thresholds, though the terms are sometimes used interchangeably. They are used across science, industry, medicine, and safety to provide data, alerts, or diagnostics. Key attributes include sensitivity, selectivity, and response time, and the output is typically an electrical, optical, or mechanical signal that can be recorded or displayed.

Common classes of detectors include radiation detectors (such as Geiger-Müller tubes, scintillation counters, and semiconductor detectors) that respond to ionizing radiation; optical detectors (photodiodes, photomultiplier tubes, CCDs) that respond to light; chemical detectors and sensors (electrochemical gas sensors, mass spectrometry detectors) that respond to chemical species; acoustic detectors (microphones) that respond to sound; and thermal detectors (calorimeters) that respond to heat. In industry, smoke and carbon monoxide detectors monitor air for combustion products; in medicine, detectors are used in imaging (for example, PET detectors) and dosimetry. In physics, particle detectors record tracks and energies of subatomic particles and contribute to experiments in fields ranging from high-energy physics to astrophysics.

Performance depends on factors such as detection limit, dynamic range, linearity, calibration, and environmental conditions. Detectors may be passive or active, requiring varying levels of power and data acquisition. Proper detector selection depends on the target signal, required sensitivity and speed, operating environment, and compliance with relevant standards and safety requirements.