Experimental Study of Capacitance Sensors to Test Seed Flow

摘要

The real-time performance detection of a seed metering device is one of key techniques to ensure the effect of precision seeding operation. In order to overcome the shortcoming of photo electric detection method in seed metering device performance measurement, 3 capacitance sensors and a capacitanceto-digital converter were proposed to test seed flow. The detection concept of seed-flow and the structure parameters of a crossed E-shape plate capacitance sensor, a paralleled plate capacitance sensor and a differential tri-plate capacitance sensor were presented. A simple seed tube and a adjust stand were designed to investigate the impact of sensor structure and seed velocity on the outputs of capacitance sensors. The test sensitivity and the feasibility of 3 sensors were studied by detecting the output variation of each sensor at different corn-seed speeds. Experimental results showed that the output variation ranges of the crossed E-shape plate sensor and the differential tri-plate sensor at 0.272-0.982m/s seed speed were 0.054-0.139pF and 0.066-0.151 pF, with the average capacitance variation of 0.1245pF and 0.1115pF respectively, and can meet the requirement to measure the performance of a seed metering device.