Design And Test Of On - Line Detection Device For Nitrogen Concentration Of Fertilizer

In the automatic irrigation and fertilization, irrigation and fertilization can be accurately monitored, and fertilizer solution concentration is the key to the implementation of fertilizer solution concentration monitoring, thus realize the online detection of fertilizer solution concentration is significant for the online regulation of fertilizer solution concentration.In this paper, in order to realize the real-time detection of liquid fertilizer nitrogen concentration automatic mixing process, a detection device with ion selective electrode method is designed. Ion selective electrode performance is easily affected by temperature, when the temperature changes, the output electrode potential changes, the error caused by the measurement results, so this paper through the establishment of temperature parameters in the model, to reduce the influence of temperature on measuring accuracy. Because of the characteristics of ion selective electrode itself, ion selective electrode in addition to easily affected by temperature, but also by the impact of interfering ions, measurement errors caused by the interference of coexisting ions in the nitrogen concentration measurement in mixed liquid fertilizer is analyzed in this paper.The main contents of this paper are as follows:In this paper, the nitrate ion selective electrode for the detection of liquid fertilizer nitrogen concentration, the liquid fertilizer nitrogen concentration detection device design, detection device is composed of a signal conditioning circuit, temperature sensor, data acquisition and display circuit, and the performance test of the testing device:(1) The standard millivolt meter PHS-3CT as contrast, device of electrode response measurement accuracy potential test, results show that the detecting device can accurately measure the output of the electrode potential.(2) In the range of 5～45℃, the temperature variation of ion selective electrode, step by step fitting method by using the least square method to establish the temperature concentration-response model parameters between the electrode potential of the three, and the validity of the model is verified by experiment.(3) the fixed interference method to analyze Cl-、SO42-、HbPO4- and HPO42-, the effect of four kinds of interfering ions on the measurement results, and analyzes the Cl- concentration and H2PO4- concentration and NO3- concentration ratio at the same time, the measurement error caused by Cl- and H2PO4- in the solution size.In this paper, the property of liquid fertilizer nitrogen concentration detection device is tested in the experiment, the results show that the reliability of the measuring apparatus designed for automatic measurement, fertilizer nitrogen concentration provides a reliable method.