Improved circuit design for electrostatic self-resonating vibroscopes

In this paper a new circuit design for automatic electrostatic vibroscopes is presented. Previously, the component which stabilized the self-oscillatory motion of the filament in the feedback loop of electrostatic vibroscopes was a negative temperature coefficient thermistor. In the present system this device is replaced with a programmable analog compander. This modification represents an improvement because response time is faster, the steady-state conditions are more stable, and the overall performance of the vibroscope is less susceptible to errors caused by changes in environmental conditions.