| 摘要 |
An ultrasonic pulse/echo measurement arrangement includes an ultrasonic transducer ( 12 ), which is mounted spatially fixed on an air spring cover plate ( 4 ). The arrangement further includes a fixedly mounted reference reflector ( 14 ), a target reflector ( 16 ) mounted on a roll-off piston ( 8 ) or on the bumper ( 18 ) as well as a transmitter/receiver evaluation electronic circuit ( 30 ). The running time as well as the amplitude of the reference signal is evaluated to precisely determine the pressure present in the interior space of the air spring. The ultrasonic transducer ( 12 ) has a lambda/4-adaptation layer ( 22 ), whose impedance does not correspond to the geometric mean of the impedances of the ultrasonic transducer ( 12 ) and the ambient air of the interior space ( 20 ) of the air spring, but rather, is a mismatch. The evaluation electronic circuit ( 30 ) can be calibrated at ambient pressure for the determination of the inner pressure of the air spring. Preferably, the pressure measuring method according to the invention is also used to determine the running-time dependent spring height in an air spring ( 2 ) of a motor vehicle.
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