The MA40S4R from Murata is an open structure ultrasonic sensor. This sensor features a composite oscillating body combining the oscillator which joins a metal plate and piezoelectric ceramics with a resonator. The body is elastically fixed to the base and housed in a case. The resonator is shaped like a funnel to efficiently radiate ultrasonic waves generated by the oscillating body into the air and to effectively concentrate ultrasonic waves from the air on centre of the oscillator. Sound pressure is the most important parameter of open structure ultrasonic sensors. In distance measurement applications, the higher the sound pressure of the ultrasonic sensor, the longer the sensor range.
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