A new type of magnetostrictive transducer was devised, which can generate voltage proportional to the velocity of mechanical vibration without attaching any pick-up element outside the transducer. Measurements on the characteristics of this trasducer were carried out in comparison with those of other well-known feedback transducer and proved that the ability of automatic frequency tracking of this transducer is very exellent up to large amplitudes. The present method is also applied with satisfactory to fatigue tests of metals at ultrasonic frequencies.
Using simple models of granular or powdered materials in motion, the possibility of utilizing the Doppler Effect in air-borne ultrasonic waves scattered by the materials, for the purpose of measurement of their average motion, was investigated. Main peak of the frequency spectrum of beat, due to the superposition of waves with modulated frequency scattered by the moving materials and those with unmodulated frequency reflected by the fixed wall of the apparatus, is found to correspond to that produced by a single body under average motion of the granular or powdered matrials. A simple explanation to this effiect is also given.
A trial for an automatic measurement of the piezoelectric performance was carried out with success for the purpose of treating many specimens and measuring temperature dependence. Various methods of piezoellectric measurements were examined if they are suitable for being automatized or not, and after all the following procedure was adopted here. The damped capacity of the piezoelectric vibrator is compensated with a condenser at low frequency by using a differential transformer, and then the frequency of the oscillator is varied. When the phase of the current through a terminating resistor equals to π/4 or -π/4, the frequency and conductance, corresponding to each quadrantal point, are measured. The results are digitally printed by a typewriter in 70 seconds, in order of temperature, capacity, frequency and conductance at first quadrantal point, those at second one and temperature. The electromechanical coupling coefficient, the quality factor and other physical parameters of the piezoelectric material are calculated from these data. Some errors and matters of question occurring in this automatic measurement were discussed, especially the subject of a deviation of phase from π/4.