Micro-capacitance sensor based on a four-phase detection technique

A charge transfer microcapacitance sensor,which is based on a fourphase detection technique, has a good strayimmune function and is suitable for the case where the capacitance value to be measured is less than 1?pF. It has a high resolution of 1?fF and a sensitivity higher than 1?V/pF. It can also output an industrial standard current of 4～20?mA.The microcapacitance sensor is possible to be wide spread for its good performance and low cost. 