A device in which incident radiation produces a measurable effect. If this effect is a rise in temperature it is called a thermal detector. If it is a rise in pressure it is called a @P04574@. In the case where an electrical signal is produced it is called a photoelectric detector. Photoelectric detectors can be classified as photo-emissive detectors and @S05591@ detectors. Where the radiation produces a chemical reaction, it is termed a photochemical detector. A detector yielding an output signal that is independent of the @W06659@ of the radiation over a specific region is called a nonselective detector. Where it is @W06659@ specific it is a selective detector. A detector having a @Q04988@ independent of the @W06659@ is a nonselective quantum counter. Certain detectors are able to distinguish between different quantum energies. This property is described by the energy resolution $$\Delta E$$ and the energy resolving @P04792@ $$\frac{E}{\Delta E}$$. These detectors are called energy dispersive detectors. In @X06718@, the reciprocal $$\frac{\Delta E}{E}$$ is often used but this is discouraged.