Abstract
Soft materials can be deformed electromagnetically with a certain driving device through which the anode current flows. The deformation is transformed to electric signal voltage by a transducer and detector circuit, that is, Inoue's circuit. This signal voltage, after being amplified, controls the grid voltage of the triode degeneratively. The anode current varies in connection with stress relaxation so as to keep variation of deformation very low in amount by the degenerative action of the feedback loop including the triode, the driving device, the detector and the amplifier. The strain is held almost constant during stress relaxation. As the device produces a force proportional to the anode current, the variation of stress can be observed by measuring the anode current variation.
