ES334537A1 - Method and Device for Measuring a Displacement - Google Patents

Abstract

Changes in the length of a sample 2 Fig. 1 are measured by coupling one end to a piston 4 forming a wall of a resonant cavity 6 supplied with microwave signals from a reflex klystron generator 8 via an isolator 10 and attenuator 12. Changes in the length of the cavity alter its resonant frequency. The output from the cavity 6 is fed via directional coupler 16 to a second similar resonant cavity 20 and to a detector 22 whose output is fed to the Y axis of an oscilloscope 24, whose X axis scanning voltage is used to modulate the klystron frequency, so that the signal observed on the oscilloscope comprises a pulse a Fig.3 with inverted peaks b, c at the resonant frequencies of the two cavities. The piston 28 of cavity 20 is displaced by micrometer adjustment until the two peaks coincide, the displacement being equal to the change in length of sample 2. In a modification, the cavities 6, 20 are separately connected to the klystron 8 and the oscilloscope 24. In another embodiment Fig. 4, the frequency of the klystron 32 is automatically adjusted to the frequency of the cavity 6. Initially, with switch 38 open and 40 closed, the frequency of the klystron 32, reference cavity 20 and measuring cavity 6 are made equal, as described above. Switch 38 is then closed and 40 opened, and the output of detector 22 cover bonding to the difference in frequency of the klystron and cavity 6 is fed to device 36 which varies the porous supply 34 to the klystron whereby its frequency follows that of the cavity 6, and is measured by a microwave converter 42. The Specification describes the assembly of a sample 2 and measuring cavity 6 in a temperaturecontrolled flask located in e.g. the water of a swimming-pool reactor.