A High Precision Stray-immune Weak Capacitance Measurement System for Gas-solid Two-phase Flows Detection

Abstract

A novel weak capacitance measurement system is proposed to measure the gas-solid two-phase flows. The system is mainly consist of capacitance sensor, Microprogrammed Control Unit (MCU), Direct Digital Synthesizer (DDS), operational amplifier, analogue multiplier and low-pass filter. Since the stray capacitance is much larger than the variation of measured capacitance, the stray capacitance should be eliminate by the measurement system. The experimental results show that the system meets the application requirement, and has good linearity, high measurement accuracy and stray-immune. The result of the percentage error is about 0.6% and the non-linear error is less than 1.5%. The sampling rate which is related to the frequency of the signal generator and the MCU clock can reach 500 kps.