CONCENTRATION DETECTOR FOR PARTICLE IN LIQUID

PROBLEM TO BE SOLVED: To attain stabilized performance through a simple structure. SOLUTION: The concentration detector for particle in liquid comprises a liquid housing 41, a light source radiating an inspection light, a photoconductor 16 for introducing the inspection light to a liquid contact face, an optical sensor for detecting the inspection light totally reflected on the liquid contact face, and a decision section wherein a choked channel part 412 having decreased channel area is disposed at a delivery port for the liquid chamber 410 of flow-in path 411 of fluid housing. A solid cleaning member 49 floating in the engine oil is encapsulated in the liquid chamber 410 and the shape of liquid chamber 410 is defined, along with the arrangement of flow-in path 411, flow-out path part 413 and liquid contact face, such that the engine oil produces a circulation flow in the liquid chamber 410 passing through the vicinity of liquid contact face.