JP2501508B

The edge of a flexible hose 8 is opened and the other edge thereof is closed, a pressure sensor 9 is fixed to the closed edge of the hose. Suppose, a water level of the opened edge of the hose is defined as a datum level 11, when the pressure sensor 9 positions at the equal level to the datum level 11, the pressure thereof reads zero, when the pressure sensor 9 positions lower than the datum level 11, the pressure sensor 9 reads positive pressure in proportion to the height between the datum level 11 and the pressure sensor's level, and when the pressure sensor 9 positions higher than the datum level 11, the pressure sensor reads positive pressure proportionately. Utilizing such natural phenomenon, the pressure sensor 9 of the present invention automatically defines a level equal to the datum level 11 easily, quickly and accurately.