Aiming at problem of amplitude modulation（ AM） capacitive displacement sensor multiplier low detecting speed

large power consumption and big thermal noise

a full-wave detecting circuit based on analog switch is designed. Firstly

analyze principle of switch full-wave detection and switch half-wave detecting

according to analysis result

full-wave detecting method is chosen. On this basis

design of switch full-wave detecting circuit and other parts of measuring system are completed. Finally

by using eight and a half bit digital multimeter 3458 A

performance index of detecting circuit and measurement system are tested. Test results show that detecting circuit can realize resolution of 0. 1m V

resolution of system in t

he range of 150

650 μm is 30 nm

the maximum deviation of measurement system is 20 nm

stability of showing value is 0. 1 m V /30 min. The measuring system meets requirements of good stability and high accuracy for capacitance measurement microsystem.