photoelectric cell


Also found in: Dictionary, Thesaurus, Medical, Acronyms, Wikipedia.
Related to photoelectric cell: photoelectric effect, photocell

photoelectric cell

or

photocell,

device whose electrical characteristics (e.g., current, voltage, or resistance) vary when light is incident upon it. The most common type consists of two electrodes separated by a light-sensitive semiconductorsemiconductor,
solid material whose electrical conductivity at room temperature is between that of a conductor and that of an insulator (see conduction; insulation). At high temperatures its conductivity approaches that of a metal, and at low temperatures it acts as an insulator.
..... Click the link for more information.
 material. A battery or other voltage source connected to the electrodes sets up a current even in the absence of light; when light strikes the semiconductor section of the photocell, the current in the circuit increases by an amount proportional to the intensity of the light. In the phototube, an older type of photocell, two electrodes are enclosed in a glass tube—an anode and a light-sensitive cathode, i.e., a metal that emits electrons in accordance with the photoelectric effectphotoelectric effect,
emission of electrons by substances, especially metals, when light falls on their surfaces. The effect was discovered by H. R. Hertz in 1887. The failure of the classical theory of electromagnetic radiation to explain it helped lead to the development of
..... Click the link for more information.
. Although the phototube itself is now obsolete, the principle survives in the photomultiplier tube, which can be used to detect and amplify faint amounts of light. In this tube, electrons ejected from a photosensitive cathode by light are attracted toward and strike a positive electrode, liberating showers of secondary electrons; these are drawn to a more positive electrode, producing yet more secondary electrons—and so on, through several stages, until a large pulse of current is produced. Besides its use in measuring light intensity, a photomultiplier can be built into a television camera tube, making it sensitive enough to pick up the visual image of a star too faint to be seen by the human eye. The photovoltaic type of photoelectric cell, when exposed to light, can generate and support an electric current without being attached to any external voltage source. Such a cell usually consists of a semiconductor with two zones composed of dissimilar materials. When light shines on the semiconductor, a voltage is set up across the junction between the two zones. A phototransistor, which is a type of photovoltaic cell, can generate a small current that acts like the input current in a conventional transistortransistor,
three-terminal, solid-state electronic device used for amplification and switching. It is the solid-state analog to the triode electron tube; the transistor has replaced the electron tube for virtually all common applications.
..... Click the link for more information.
 and controls a larger current in the output circuit. Photovoltaic cells are also used to make solar batteries (see solar cellsolar cell,
semiconductor devised to convert light to electric current. It is a specially constructed diode, usually made of forms of crystalline silicon or of thin films (as of copper indium gallium selenide or amorphous silicon).
..... Click the link for more information.
). Since the current from a photocell can easily be used to operate switches or relays, it is often used in light-actuated counters, automatic door openers, and intrusion alarms. Photocells in such devices are popularly known as electric eyes.

photoelectric cell

[¦fōd·ō·i′lek·trik ′sel]
(electronics)

photoelectric cell

A device incorporated in an electric circuit; in response to light that falls on the cell, the electrical output or the resistance varies; used in measuring devices and in control devices that depend on illumination level or the interruption of a light beam.
References in periodicals archive ?
Logan Plus v.4.0 software was used to synchronize the GPS files with the video, establishing the beginning of action when the participant crossed the initial photocell; this was then added to the duration obtained through the photoelectric cells.
"I agree with him, because we have some of the greatest minds in science and engineering in the country, and in fact we have some companies doing great work right now with photoelectric cells and renewable energy."
"Complex photoelectric cells take advantage of the fact that the electrons released by the light will themselves release electrons when they strike another suitable metallic surface....
One of the many salacious historical kernels Clausen has unearthed concerns a never-built sound installation that would have paired a work by John Cage with the Lippold sculpture on the building's west entrance: "Cage devised a system whereby the movement of people going in and out of the lobby would activate photoelectric cells; these in turn would release Muzak ...
There were photos and items from beaded Indian moccasins to photoelectric cells to locomotive parts.
The converters will regulate the electricity generated by its photoelectric cells to a steady 125 volts for use by the station.
Photoelectric cells scan the material edges and give setting pulses to the guide rolls.
In 1902, Arthur Korn, German physicist, patented a method that used photoelectric cells for synchronization.