非接触電磁型ねじり振動駆動-検出器
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概要
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Usually, we can easily design a torsional resonator whose vibration mode and velocity of torsional wave are already known, but it is very difficult to know the resonant frequency of the torsional resonator, for example, a bar with rectangular cross section, or of complex resonance with the other vibration mode such as coupled mode of longitudinal and torsional vibrations. In these cases, we must often determine its resonant frequency by actual experiments, but few devices for these purposes have been developed. The authors divised electro-magnetic type torsional vibration driver-detector for measurement of a resonant frequency and Q-factor, without any mechanical contact, and also these converters are intended not to have any acoustical influences upon a resonator under test. In this paper, we describe the mechanism and the construction of transducer(Fig. 1〜Fig. 3), method of measurement(Fig. 4)and some characteristics which was got by experiments, of the trially-made convertor. Besides, we investigated the torque factor AT(N-m/Amp)or(Volt-sec)of this reversible transducer. Inclination of AT vs. air gap between the converter and sample:0. 1mm〜2. 0mm, dimensions:10mm〜40mmφ and materials;Steel;Al and brass of sample, and the frequency;20kHz〜50kHz are shown in corresponding figures. The value of AT under the conditions prescribed, was about 10^<-5>〜10^<-4>(N-m/Amp). From these results and experiments, we got some data for reformation of the transducer and whole apparatus, and also refer to some notices for the way of measurement. Finally, according to the way described in this paper, we can easily measure a torsional resonant frequency of sample, and with very care, the electro-magnetic disturbance was comparable with input noise level;0. 2μV(rms)of the pre-amplifier.
- 1972-11-01