Problem to be solved: to provide a drip monitoring sensor capable of detecting a droplet over a wide range within the drip tube while reducing the number of parts of the light emitting portion and the light receiving portion.A drip monitoring sensorIt can be attached to the drip tube.A drip monitoring sensor for monitoring a liquid falling within the drip tubeA light emitting portion capable of irradiating light inside the drip tubeThe light irradiated by the light emitting portionThe retroreflective portion which is reflected and reflected in the plane crossing the drop direction of the droplet in the drip tube, andA light receiving portion capable of receiving light reflected and rereflected by the retroreflective portion and.Diagram【課題】発光部及び受光部の部品点数を減らしつつ、点滴筒の内部の広い範囲にわたって液滴を検出可能な点滴監視センサを提供する。【解決手段】点滴監視センサは、点滴筒に装着可能であり、前記点滴筒の内部を落下する液体を監視する点滴監視センサであって、前記点滴筒の内部に光を照射可能な発光部と、前記発光部により照射された前記光を、前記点滴筒における液滴の滴下方向に交差する面内で再帰反射させる再帰反射部と、前記再帰反射部により再帰反射した光を受光可能な受光部と、を備える。【選択図】図３
