Synthesis of simple interface circuit based on time-period detection technique for capacitance measurement

This paper presents a synthesis simple method using time-period detection technique for use in capacitance measurement. The proposed scheme consists of a square wave generator, an integrator, a sample-and-hold circuit, and a designed logic circuit. Output signals of logic circuit are used to control the integrator followed by sample-and-hold circuit in sequential operation. The proposed circuit provides measuring capacitance in 4 ranges; 0.1-1 nF, 1-10 nF, 10-100 nF, and 100-1000 nF. Each range has output voltage signal proportional to the sensing capacitor from 0.5 V to 5 V. Performances of the proposed circuit were experimentally verified. Results are in good agreement with expected values.