| 摘要 |
PURPOSE:To form a pressure sensing device of high reliability which is not affected by changes of the atmospheric pressure and temperature. CONSTITUTION:A pressure sensing device is installed in a window frame of a door of an automobile and also it is equipped with an elastic tube 11 of which one end is closed and with a pressure sensor 12 which is provided at the other end of the elastic tube 11 and converts the difference between internal and external pressures into an electric signal. In the vicinity of one end of the elastic tube 11, a pinhole, i.e., an orifice 13, which communicates with the outside and has an opening diameter not responding to a sudden change of the internal pressure is formed. In another way, a slender hole 13 fulfilling the role of a restrictor is formed, in place of the orifice, in a cover for one end of the elastic tube 11. A dustproof filter or a sponge being removable may also be put on the part of an opening of the orifice 13. The pressure sensor 12 is equipped with a diaphragm or bellows of a differential pressure sensing type and a piezoelectric element converting a mechanical change in the shape of these members into an electric signal. This electric signal is amplified by an amplifier 14 and then supplied to a comparator 15. A reference power source 16 setting a threshold for detecting the hold of a foreign substance is connected to the other input end of the comparator 15. |
