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In the real-time mixing pesticide of the Variable Rate Spay (VRS), In order to detect and control micro-flow of pesticide, a micro-flow control system and fuzzy control arithmetic were designed with Differential Pressure (DP) flow meter, Electrical Control Injector (ECI)and microprocessor. Using water as work fluid, at 20℃, the control system was tested. The testing results show that static errors is ±5% at the range of 0 ~ 0.9 mL/s, the response time is 0.25s, the steady errors is ±2% at dynamic response test when initial value is 0.1mL/s and final value is 0.5 mL/s.

To detect water and pesticide flow rate for variable-rate spray, a new type liquid Differential Pressure (DP) flow sensor was introduced in this paper. The main problem that we attempt to solve was on-line flow measurement, to know the flow each moment and adjust pesticide to a desirable flow in the spray system. This new DP flow sensor is composed of a straight pipe with two branch pipes (an upstream branch pipe and a downstream branch pipe) in two ends and a DP sensor. A pressure difference between the upstream branch pipe and the downstream pipe is detected and converted into a voltage signal by the DP sensor.This voltage signal is transmitted to a microprocessor to determine liquid flow rate. Using water as working fluid, the liquid DP flow sensor at a certain dimension has been tested at the temperature of 22.0"C. The experimental results have shown that the presented device is satisfactory to variable sprayer with the measurement errors less than 1 %. This liquid DP flow sensor's advantage is simple in structure.

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