抄録
In measuring characteristics of a string vibration, an electromagnetic transducer, which takes out changes of reluctance which occur because of the string vibration in the magnetic circuit, is used frequently. Turn number of the coil needs to high in order to get enough electric output, because magnetic coupling between the electromagnetic transducer and the string is very sparse. Therefore floating capacitance of the coil increases and current flows without the presence of a load. In the present paper loading effect is studied with theoretical analysis by making use of δ function for a expression of the magnetic attraction and the coupling between the transducer and the string at a particular point. The characteristic equation and the solution are obtained by making use of Laplace transform. In order to confirm the validity of the analysis results, measurements are made by laser doppler vibrometer to eliminate the influence of the equipment itself. Results show that the damping coefficients are increased by means of energy loss in the coil of the transducer. Also it is verified that the analysis results about the appearance of non-harmonic components, occurrence of beats, and increase of damping coefficients are in good agreement with experimental results.
