Interface Circuit for Capacitive Measurement
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Abstract
This paper presents an interface circuit for Capacitive measurement differential of capacitive sensor by using a Sigma Delta capacitance to digital converter (CDC). This interface circuit operates on the principal of capacitance changes in a capacitive sensor to digital value logic level high “1” and low “0”. The proposed circuit consists of a capacitance to voltage converter (CVC), an integrator, a comparator, a flipflop and digital to analog converter (DAC) with feedback current. The simulation results showed that the circuit can operate according to the designed principle with errors approximately equal to 0.6% for the nominal value of the sensor capacitances (C0) of 100 pF, Full scale (FS) of 10 %, the input frequency (Fin) of 100 Hz, the clock frequency (Fclk) of 10 kHz.
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