Abstract: A transducer for detecting pressure changes in pipes by detecting deformation of the pipes and for converting the pressure changes in the pipes into electric signals includes a piezoelectric element having a bimorph structure as a sensor element. The piezoelectric element is constructed in such a way that an intermediate layer is interposed between two piezoelectic pieces. The element is pressed against the pipe surface by a holder which is sufficiently elastic to allow opposite ends of the piezoelectric element in the circumferential direction of the pipe to elastically abut against the pipe periphery. Thereby the ends of the piezoelectric element can be pressed in tight contact against the outer surfaces of pipes having various diameters, and the internal pressure of the pipes can be detected reliably.

Abstract: A transducer for detecting pressure changes in pipes by detecting deformation of the pipes and for converting the pressure changes in the pipes into electric signals uses a bimorph as a sensor element. This bimorph is pressed to the pipe surface by means of a holder. The transducer is free from complicated adjustment of the pressing force against the sensor element, very simple in structure, easy to adjust when mounting, light in weight so as to hardly influence an injection system, and less susceptible to effects of noise due to vibration.