A Capacitance Measurement System with milliwatt power and attofarad Resolution

A capacitive measurement system with attofarad resolution is presented. The electronics setup consists of a capacitive sensor interface with period-modulated output and amicrocontroller board with 70 MHz clock to read out the output period. The electronic interface which is based on a capacitance-to-voltage converter and a relaxation oscillatorhas been designed and implemented in 0.7 μm standard CMOS technology. The measured data is transferred to a computer viaRS232 port and analyzed in a Labview program. The resolution of about 1.5 aF is achieved for a range of 1 pF and ameasurement time of 1 s. The highest resolution which can be achieved is about 0.5 aF for a measurement time of about 10 s.

Keywords:

Capacitive sensors , interface , resolution