| 摘要 |
910,898. Ultrasonic measuring devices. GENERAL DYNAMICS CORPORATION. July 20, 1960 [July 31, 1959], No. 25364/60. Class 40 (7). [Also in Group XXXVIII] A pressure gauge for measuring pressure pulses of short duration comprises, Fig. 1, a piezoelectric crystal wafer 10 sandwiched between metal electrodes 12 and 14. In order to isolate the crystal wafer from temperature changes associated with the pressure pulses being measured an acoustic transmission line 26 is attached to the electrode 12. A further transmission line 28 may be attached as shown to electrode 14 in order to prevent reflection of the pressure pulse at the electrode 14. The lines are preferably made of the same material as the crystal wafer in order to inhibit reflections at the junctions. In the preferred embodiment the wafer may be of tourmaline, barium titanate or quartz 0.7 cm. diameter and 0.02 cm. thick and the transmission lines 7 cm. long, 0.7 cm. dia. Connection to the -indicator, oscilloscope 16, is made via coaxial stub 18, and the wafer is screened by metal tube 30. Calibration method.-The gauge is calibrated by attaching a conductive disc 35 to the gauge and applying a pressure pulse to this disc by means of a pulsed magnetic field generated by placing the upper surface of the single turn coil 37 (Fig. 2) in abutting relation with disc 35 and then discharging capacitor 44, previously charged to a high-voltage from source 46, through the coil. The discharge circuit is critically damped by adding resistance to the circuit in the form of the strips 50 and 52 of resistance material, e.g. stainless steel. The amplitude of the pressure pulse applied to disc 35 is assessed by detaching disc 35 from the pressure gauge and placing the disc on top of the coil 37. The capacitor is then discharged through the coil and the height to which the disc is lifted by the pressure pulse, against gravity and air friction, is measured on scale 54. From this height the magnitude of the pressure pulse may be calculated as described in the Specification.
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