Abstract: Provided is an ultrasonic detector, including a detection area and a cover body. The cover body comprises at least two cavities, multiple fluid inlets and multiple fluid outlets which are in communication in sequence from inside to outside. The multiple fluid inlets, the multiple fluid outlets and the cavities are in fluid communication to form a fluid channel. The fluid channel is configured to guide fluid to flow along at least one bent path, and the detection area is located in an innermost one of the cavities.

Abstract: Provided is a liquid level detection method and a liquid level sensor, which relate to the field of liquid level measurement technologies. The liquid level detection method includes that a position of a magnetic field formed by two magnets with same poles disposed facing to each other changes accordingly when a position of a float changes; a plurality of magnetoresistive elements for collecting magnetoresistive signals is disposed equidistantly at a movement range of the float; and two adjacent magnetoresistive elements located between the two magnets detect change of magnetic field intensity and output a linear detection result when the float moves, and a liquid level height value is calculated according to the detection result.

Abstract: Provided is an optical concentration sensor protective casing, including an outer cover and a bubble isolation shield. The bubble isolation shield is embedded on the inner side of the outer cover. The outer cover is provided with a convection hole. The bubble isolation shield is provided with a liquid intake hole. Further provided is an optical concentration testing device including the protective casing.

Abstract: An ultrasonic concentration detector and liquid feature detector, the detector includes a body, a concentration detection tube, and an ultrasonic transducer sheet; the body includes a sealed chamber and an end cap part; an opening at a first end of the concentration detection tube is encapsulated by a reflection plate, and an opening at a second end of the concentration detection tube is encapsulated by the end cap part; the reflection plate faces to an outer surface of the end cap part; and a upper side and a lower side of the concentration detection tube are provided with an upper through hole and a lower through hole respectively. The ultrasonic transducer sheet is disposed in the sealed chamber at a second end of the concentration detection tube, facing to a reflection plate.