Design of particle velocity measurement system based on spatial filtering effect of capacitive sensor

When a particle moves through a spatial filter, the output signal contains not only the periodic frequency component related to particle velocity, but also the low frequency component called the pedestal frequency which decreases the signal-to-noise ratio and affects the accuracy of particle velocity measurement. In this paper, a novel spatial filtering method based on capacitive measurement using a differential measurement technology is proposed to remove the pedestal frequency component, in the meanwhile to improve the accuracy and signal-to-noise ratio of the measurement system. Particle velocity measurement system test rig based on spatial filtering effect of capacitive sensor contains AC-based capacitance-voltage transforming circuit, NI DAQ-card, capacitive sensor and computer with LabVIEW2012 programming environment. Experimental data results indicate that the novel spatial filtering method is capable of removing the pedestal frequency component from the output signal with relative error lower than ±2.6% and standard deviation within 0.092 over a velocity range of 2-5 m/s.