Detector
From Exampleproblems
In general, something that reacts to stimuli in a set manner, and is either part of a living being, or made by a living being, for the purpose of doing such reacting. Such reactions include sending a signal on for further processing, or activating a reaction that has either evolved, or been designed, to aid a living being.
In telecommunications, the term detector has the following meanings:
- A device that is responsive to the presence or absence of a stimulus.
- In an AM radio receiver, a circuit or device that recovers the signal of interest from the modulated wave.
- In FM reception, a circuit called a discriminator is used to convert frequency variations to amplitude variations.
- In an optical communications receiver, a device that converts the received optical signal to another form. Note: Currently, this conversion is from optical to electrical power; however, optical-to-optical techniques are under development.
- Source: from Federal Standard 1037C
Most optical detectors are quantum devices in which an individual photon of light produces a discrete effect.
- In a photographic plate, a silver halide molecule is split into an atom of metallic silver and a halogen atom
- In electronic detectors, the photon excites an electron
- into the conduction band (in semiconductor detectors)
- or into free space (in photomultiplier tubes)
There are optical detectors that are effectively thermometers, responding purely to the heating effect of the incoming radiation, such as pyroelectric detectors, Golay cells. thermocouples and termistors, but they are much less sensitive.
In astronomy, the detecting devices generally used to record images are charge-coupled devices (CCD), although, before the 1990s, photographic plates were the most common.
In experimental particle physics, a particle detector is a device used to track and identify elementary particles.
