SENSOR WITH ELASTIC SURFACE WAVE ELEMENT

PURPOSE: To simplify measurement means for sensor output. CONSTITUTION: On the surface of piezoelectric substrate 21, an input IDT electrode 22 and output IDT electrodes 23 and 24 are provided, and between output IDT electrodes 23 and 24, a functional film 25 with which propagation time of elastic surface wave is changed according to sticking and penetration of a sensing target is provided, and, the input IDT electrode 22 excites pulses of constant cycle with a pulse signal generator 26, and, depending on whether the elastic surface waves propagating on the substrate at that time reach the output IDT electrodes 23 and 24 at the same time or not, amplitude change is generated an the signal combined with the output, then, the change of the amplitude is detected with a signal level detector 27. Thus the degree in sticking and penetration of the sensing target is detected through amplitude changes in signal.