A Capacitance Measurement System with milliwatt power and attofarad Resolution
Keywords:
Capacitive sensors, interface, resolution
Abstract:
A capacitive measurement system with attofaradresolution is presented. The electronics setup consists of acapacitive sensor interface with period-modulated output and amicrocontroller board with 70 MHz clock to read out the outputperiod. The electronic interface which is based on acapacitance-to-voltage converter and a relaxation oscillatorhas been designed and implemented in 0. 7 یm standard CMOStechnology. The measured data is transferred to a computer viaRS232 port and analyzed in a Labview program. The resolutionof about 1. 5 aF is achieved for a range of 1 pF and ameasurement time of 1 s. The highest resolution which can beachieved is about 0. 5 aF for a measurement time of about 10 s.