To inexpensively and easily measure a substance with a small space, by applying a beam to a mixture to be measured at a plurality of wavelength regions that are prescribed in various ways, measuring the intensity of the beam being affected by the mixture, and detecting only one wavelength region.
Observation windows 16 and 16' are provided at the cover of a conduit 14 where a mixture 12 of stock/undiluted solution 12 flows in a direction marked by an arrow F, and at least one light beam source (light- emitting diode) 18 and a sensor (photo receiver) 20 are arranged opposite to them. Then, a beam is applied to the mixture 12 at a plurality of wavelength regions being prescribed in various ways by a beam source 18, and the intensity of the beam being affected by the mixture 12 is detected by the sensor 20. At this time, the sensor 20 detects only one of beams in a wavelength region that is prescribed in various ways at each specific point. A measurement/ evaluation electronic circuit 24 outputs a measurement signal for indicating the degree of beating, amount of air and/or the degree of condensation in the mixture 12 according to the detection signals.
MUENCH RUDOLF
WINTER FRANZ
