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为实现对大量元素水溶肥种类的快速准确辨识,根据水溶肥的介电特性设计了一个传感器,并在此基础上采用特征频率法,研制了一种大量元素水溶肥快速辨识装置,主要由±5V稳压电路、单片机控制电路、激励信号发生电路、传感器、真有效值转换电路和LCD显示模块组成。以市面上常见的尿素、普钙、硫酸钾、磷酸氢二铵、磷酸二氢钾和硝酸钾6种大量元素水溶肥作为试验对象,在1 kHz~10 MHz激励信号频率范围内研究了其频率响应特性,得出了9个用于辨识6种大量元素水溶肥的激励信号特征频率,即30、40、50、600、700、800 kHz和3、4、5 MHz。根据各种水溶肥分别在9个特征频率处的响应模式,设计了对6种大量元素水溶肥的辨识策略。该装置的辨识性能采用234组不同类型和浓度的待测水溶肥进行验证试验,结果表明:该装置的辨识准确率为98.3%,完成1次辨识的平均时间为14.3s,最长不超过19.5 s,表明该装置具有良好的快速性和准确性,满足实际应用要求。
In order to realize rapid and accurate identification of a large number of water-soluble fertilizer species, a sensor was designed according to the dielectric properties of water-soluble fertilizer, and based on this method, a fast identification device for water soluble fertilizer with large amount of elements was developed by using the characteristic frequency method. 5V regulator circuit, microcontroller control circuit, excitation signal generating circuit, sensors, true RMS conversion circuit and LCD display module. Six common water-soluble fertilizers including urea, calcium, potassium sulfate, diammonium phosphate, potassium dihydrogen phosphate and potassium nitrate were tested in the frequency range of 1 kHz ~ 10 MHz excitation signal. Response characteristics, nine excitation signal characteristic frequencies for identifying six water soluble fertilizers were obtained, namely 30, 40, 50, 600, 700, 800 kHz and 3, 4, 5 MHz. According to the responses of various water soluble fertilizers at nine characteristic frequencies, the identification strategies of six kinds of water soluble fertilizers were designed. The identification of the device using 234 different types and concentrations of water-soluble test fertilizer to be tested, the results show that: the identification accuracy of the device was 98.3%, the average time to complete a recognition of 14.3s, the longest no more than 19.5 s, indicating that the device has good fastness and accuracy, to meet the practical application requirements.