High-Speed Capacitance Measuring System for Process Tomography

Javad Frounchi, Ali-Reza Bazzazi, Khabat Ebnabbasi, and Kaveh Hosseini

Microelectronic and Microsensor Research Laboratory, Electrical Engineering Department, Faculty of Engineering, Tabriz University, Tabriz, Iran

Tel: +98 (0)411 3393722, Fax: +98 (0)411 3300829, Email: jfrounchi@tabrizu.ac.ir

ABSTRACT

A high-speed small capacitance measuring system has been designed and implemented on a PCB with discrete electronic components. The implemented system was calibrated and tested using one hundred 1pF capacitors with tolerance of 1%. The system sensitivity is 2 mV/fF for capacitance values in range of 0-2 pF. The sensitivity can be increased to 4 mV/fF for the same capacitance range if the power supply voltage is increased from 5 to 10 volts. For small capacitance measurement, the sensitivity is adjusted dynamically using a programmable gain amplifier which is controlled by a host PC. The capacitance measuring time is 1µS and the noise voltage at the output of the system is well below 1 mV (rms).

Keywords Capacitance measurement, Switched-capacitor amplifier, Electrical Capacitance Tomography