(under subclass 88) Systems in which the condition maintained or sensed is an optical or chemical property.
SEE OR SEARCH THIS CLASS, SUBCLASS:
5, for processes of controlling flow according to the conductivity of the mixture.
392, for control of a single fluid flow by sensing electrical characteristics.
SEE OR SEARCH CLASS
250, Radiant Energy, 200+, for photocell circuits.
356, Optics: Measuring and Testing, for examination of material by light for optical properties particularly
128+, for refraction tests, subclasses 410+ for shade or color tests involving flowing liquids, and subclasses 432+ for light transmission tests involving gases or liquids.
422, Chemical Apparatus and Process Disinfecting, Deodorizing, Preserving, or Sterilizing,
50+, for chemical analyzers; and subclasses 105+ for apparatus operating in response to a sensed condition.
