Improvement of Detection Accuracy of Soil Nitrate-nitrogen Based on Ion Selective Electrode

Abstract:

Ion selective electrode (ISE) is a quick and lowcost method of soil nitratenitrogen detection. Aiming at improving the accuracy of ISE based soil nitratenitrogen detection, influences of ISE signal characteristics (small signal of millivolt level and high internal resistance) and environmental factors (noise and temperature influence) on detection precision were discussed at first. Second, how to improve the accuracy was researched. For antiinterference and collection of accurate ISE potential, signal conditioning module including impedance transformation, filtering and amplification was added to detection circuit. Besides, measurement model was amended by software temperature correction for decreasing the influence of temperature. And then, two groups of contrast experiments were designed and conducted. One was the collection of ISE potential signals measured by detection circuit with impedance transformation and filtering module and by detection circuit without this module. The other one was the detection of soil nitratenitrogen content measured by linear regression model and temperature correction model. The results show that in the condition of high frequency noise, measuring error of detection circuit with impedance transformation and filtering module comparing with ion meter is less than 1mV. It has high accuracy and antiinterference ability. And when the environment temperature changes, relative error of soil nitratenitrogen content between temperature correction model and ion chromatography method is less than 8.20% and correlation coefficient R attains to 0.9986. The result of reducing error and improving accuracy is effective.