detector

A detector is an instrument that senses a physical quantity and typically transmits a signal in response. These devices are crucial in various fields, including electronics, where they are used to rectify radio waves and recover superimposed information, essentially reversing the modulation process.123

In spectroscopy, optical detectors play a vital role. Historically, photographic plates were used, but they have largely been replaced by more advanced technologies like photoemissive detectors (e.g., photomultiplier tubes) and photoconductive semiconductor detectors. Photoemissive detectors work by ejecting electrons when struck by photons, which are then collected to generate a signal. Photomultiplier tubes amplify this effect significantly, allowing for the detection of individual photons. Solid-state detectors, such as semiconductor photodiodes and charge-coupled devices (CCDs), detect light by exciting electrons within the semiconductor material, creating a measurable current.4

Detectors can be classified as general, sensing all solutes, or specific, targeting particular types of substances. They can also be nondestructive, preserving the sample, or destructive, altering it during the sensing process. Key characteristics of detectors include their lower limit of detection, sensitivity, and linear range, which define their performance and accuracy.5