Novel Signal Conditioning Circuit for Push-pull Type Capacitive Transducers

A novel signal conditioning circuit suitable for push-pull type capacitive transducers is proposed. The circuit developed is capable of providing a linear output over a wide range of values of the physical quantity being measured even when the transducer output has an inverse relationship with the measurand. The push-pull type capacitive transducer becomes an integral part of a relaxation oscillator, the duty cycle ratio of the output of which becomes proportional to the measurand. The various sources of error in the circuit are analysed and quantitative expressions to estimate such errors are derived. Results obtained from conducting tests on a prototype indicate that the circuit possesses very low systematic errors.