Research On Photoelectric Runoff Correlation Rate Measurement System Based On Virtual Instrument

In the research of the soil erosion, the rate of slope runoff is an indispensable hydrodynamic parameter in the runoff computation and the soil erosion forecast. The development of the research of slope runoff rate is very important to the further disclosure of the mechanism of the slope runoff and the soil erosion.At present there's still no special instrument which is widely used to measure runoff rate. Most of the domestic and foreign research facilities still use the dye tracer method to study runoff rate. This method requires manual operation, and it also has minor errors caused by human vision. Therefore, it is scientifically and practically important to develop an automation measurement system which can survey runoff rate real-time and on-line.The slope runoff formed by soil erosion is two-phase flow constituted by water and sand. This research embarks from the theories of two-phase flow, developing a runoff rate on-line measurement system based on Lab VIEW virtual instrument platform. The main conclusion includes:1. Carried on the theoretical analysis and the research to the correlation method which surveys flow rate, and established the mathematical model of it.2. Developed a runoff rate on-line measurement system based on correlation flow rate measurement theory by using Lab VIEW virtual instrument platform. The virtual instrument consists of the infrared photoelectric sensor, the signal processing circuit, the PCI-6040E data acquisition card as well as the correlation survey software programmed by LabVIEW.3. Direct peak-to-peak value correlation has high precision, but its computation is complex relatively and takes more time. FFT fast correlation algorithm reduces the computationcomplexity from O(N~2 ) to O((3/2)Nlog2N + N) and doesn't affect the precision. Thecomputation speed enhanced 37 times theoretically. System speed of response enhancedgreatly.The test result indicates this measurement system is suitable for the silt content scope of0~250kg/m3, not needing to adjust the correction coefficient in this scope, themeasurement system thus has the good compatibility. The duplicated parameter ofmeasurement system in entire measuring range- the maximum value of mean valuestandard deviation of correlation flow rate, σ_V|- max is 0.097m/s, so the repeatability isgood. Takes the flow rate surveyed by the dye tracer technique as standard value to carry on demarcating experiment, it is found that the most great relative error of the system is 4.14%, which makes the high-degree accuracy.5. The system uses optics method to survey flow rate, which makes it easy to resist electronmagetic interference and a good reliability. The non-contact type measuring technique makes the sensor not to be involved in the fluid, and it also avoids the measurement system to influence the runoff rate. The result after many times indicates that this runoff correlation rate measurement system can survey the slope runoff rate fast, real-time, and on-line. It is easy-operating, stable, reliable, and easy to resist the disturbance outside.