FAST RESPONSE CAPACITIVE SENSING SYSTEM FEATURING STEEP SLOPE FILTER DISCRIMINATION CIRCUIT

摘要

The high speed, high accuracy capacitive gauging system employs an oscillator fed through steep slope filter that is discriminates between very small changes in capacitance even in the presence of electrical noise. During intervals when the probe tip is retracted, the oscillator frequency is calibrated to match the sweet spot in the center of the linear operative region of the steep slope filter. This calibrates the system to overcome the effects of varying temperature and humidity in the manufacturing environment.