| 摘要 |
An ultrasound detector of thin films comprises an ultrasound transmitter (1) and an ultrasound receiver (2) and is formed as a resonator, the distance between the transmitter and the receiver corresponding substantially to an integral multiple of one half of a wave length. The attenuation caused by even a thin plastic film between the transmitter (1) and the receiver (2) is then easily detectable. Furthermore the ultrasound frequency is varied for taking tolerances, changes in temperature and humidity of air etc. into account, Fig. 10 (not shown).
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