A CALIBRATION METHOD OF PRESSURE TRANSDUCER (HYDROPHONE) USING COLLISION BETWEEN TWO ELASTIC BARS

摘要

For the purpose of measuring impulsive pressure generated by spark discharge or explosion in water, pressure transducers with piezo-electric polymer as a sensitive element to pressure are used in general, for example, Uchiyama, Kusakabe & Isuzugawa (1999). These transducers are usually calibrated in water using supersonic waves and at the same time their frequency characteristics are defined. However, in addition to the device being complicated and expensive, it is difficult to generate supersonic waves whose pressure values are close to what we try to measure (several [MPa]). This paper proposes a method to get the relation between the output of a transducer and the value of pressure acting on it making use of the compression pulse that is produced by making a striking steel bar collide with a standing steel bar whose one end contacts with water. The value of the compression pulse transmitted from the standing bar into water is given by the product of the stress value computed using the velocity of the striking bar and the transmissivity from the standing bar into water that was obtained by an experience in advance. The pressure transducer, that we made ourselves, with PVDF piezo-electric film as the sensitive element is calibrated by this method and the result is examined.