| 摘要 |
The field of application is the measurement of the change in transmission loss of delay lines with surface acoustic waves, which can be influenced by non-electric quantities such as moisture, gas concentration and others. It is the aim of the invention to create a measuring device which achieves high resolution and decisively reduces the complexity of the electronic section. According to the invention, the object is achieved by the fact that a three-transducer arrangement is applied to a piezo-electric substrate, the outer transducers of which are connected electrically in parallel as input transducers and the centre transducer of which is used as output transducer, the transit distances of the delay lines thus produced differing by at least one quarter of the wavelength of the SAW, the arrangement being located in the feedback branch of an amplifier and being connected together with it to form an oscillator. In one of the delay lines, means for damping the SAW in dependence on non-electric quantities are arranged. The device converts changes in the transmission loss of one of the delay lines into a change in the oscillator frequency. |
