Non-contact linear displacement sensors using amorphous-core multivibrators for mechanocardiography

New non-contact type linear-displacement sensors are constructed using a magnetometer combined with a small magnet. The magnetometer contains an amorphous-wire-core multivibrator bridge. High linearity of the sensor output versus the magnet displacement is realized by cancelling the nonlinearity of the field versus displacement of the magnet using the saturation curve of the magnetometer. These sensors detect magnet displacements of 1 μm - 6 mm at frequencies 0 - 4 kHz. Mechano-cardiograph, that is, Phonocardiograph and Sphygmograph use a new non-contact sensors by attaching a small magnet to the chest wall without disturbances that have been a problem when using conventional microphone type sensors. These non-contact type sensors are expected to add easy manipulation to the mechanocardiograph, similar to the electrocardiograph, and become an effective tool for diagnosis of cardial functions.