(under subclass 861) Subject matter wherein (a) a tracer substance is introduced into the fluid at a fixed rate and a downstream detector means is responsive to the tracer
concentration or (b) a fixed concentration of tracer substance is introduced into the fluid and a downstream detector means is responsive to the rate of introduction of the tracer.
SEE OR SEARCH CLASS
250, Radiant Energy,
302+, and 356.1 for radiation tracer methods and flow metering of invisible radiation.
