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oxide-coated cathode • ozone monitor 509
oxide-coated cathode See OXIDE-COATED EMIT-
TER.
oxide-coated emitter An electron-tube cathode or
filament coated with a material, such as thorium
oxide, for increased electron emission at low
emitter temperatures.
oxide-coated filament See OXIDE-COATED
EMITTER.
oxide film 1. The thin film of iron oxide that constitutes
the recording surface of a magnetic disk
or tape. 2. The layer of copper oxide formed on
the copper plate of a copper-oxide rectifier.
oxide-film capacitor An electrolytic capacitor, so
called because the dielectric is a thin oxide film.
oxide rectifier A solid-state rectifier using a junction
between copper and copper oxide. Also called
COPPER-OXIDE RECTIFIER.
oximeter A photoelectric instrument for measuring
the oxygen content of the blood. It operates by
passing visible light through the earlobe, and analyzing
the color and intensity of the emerging
beam. Also called ANOXEMIA TOXIMETER.
oxygen Symbol, O. Abbreviation, O 2 . A gaseous element.
Atomic number, 8. Atomic weight, 15.999.
Constitutes 21% of Earth’s atmosphere. It readily
combines with various elements to form compounds
(see OXIDATION).
oxygen analyzer An electronic gas analyzer designed
especially to measure oxygen content. The
operation of this instrument is based on the paramagnetic
properties of oxygen.
oxygen recombination In nickel-cadmium (NICAD)
cells and batteries, a process in which oxygen is
generated in the vicinity of the positive electrode,
and is reduced with water in the vicinity of the
negative electrode. This produces battery heating.
oz 1. Abbreviation of OUNCE. 2. Abbreviation of
OZONE.
oz-in Abbreviation of OUNCE-INCH.
ozocerite An insulating mineral wax. Dielectric
constant, 2.2. Dielectric strength, 4 to 6 kV/mm.
Also spelled OZOKERITE.
ozone Symbol, O 3 . An allotropic form of oxygen. Its
formula indicates that each molecule has three
atoms. Produced by the action of ultraviolet rays
(or electrical discharge) on oxygen, its characteristic
odor (somewhat like weak chlorine) can often
be detected around sparking contacts or in the
air after a thunderstorm.
ozone layer In the earth’s atmosphere, a layer of
ozone gas in the upper troposphere and lower
stratosphere. It is produced by ultraviolet
radiation from space, mainly from the sun. The
ozone layer tends to block ultraviolet radiation,
reducing the amount that reaches the surface of
the earth.
ozone monitor An instrument for measuring the
concentration of ozone in the atmosphere. One
version measures the extent to which ultraviolet
radiation is absorbed by a sample of air; the
greater the absorption, the higher the ozone concentration
in the sample.