肥液氮素浓度在线检测装置设计与试验

发布时间：2018-03-24 06:36

  本文选题：肥液　切入点：氮素浓度　出处：《昆明理工大学》2015年硕士论文

【摘要】：在自动灌溉施肥中,灌水和施肥可以得到精确地监控,而获得肥液浓度是实施肥液浓度监控的关键,因此实现肥液浓度的在线检测对于实现肥液浓度的在线调控有重要意义。现有的自动灌溉系统中肥液浓度主要是通过肥液EC值来衡量,肥液EC值反映的是中盐的总含量,没有反映出肥液中各组分的含量。为实现肥液自动混合过程中氮素浓度的实时检测,本文采用离子选择电极检测法设计了一个检测装置,分析了电极的温度变异性,在此基础上建立温度参数模型；并针对混合肥液中常出现的,对氮素浓度测量造成干扰的共存离子引起的测量误差进行了分析。本文的主要研究工作如下：采用硝酸根离子选择电极检测肥液氮素浓度方法,设计了肥液氮素浓度检测装置,检测装置由信号调理电路、温度传感器、数据采集以及显示电路组成,并对该检测装置进行了性能测试试验：(1)以标准毫伏计PHS-3CT作为对比,测试了装置对电极响应电势的测量准确性,检测装置测量最大相对误差为5.2%,最小相对误差为1.2%,表明检测装置能够准确测量电极输出电势。(2)在5-45℃范围内,分析了离子选择电极的温度变异性,以25℃为基准,电势值的最大温度变异率为8.8%；采用最小二乘法的逐步拟合方法建立了温度-浓度-电极响应电势三者之间的参数模型,并通过试验得到参数模型测量误差最大为9.2%,验证了该模型的有效性。(3)采用固定干扰法分析了C1-、SO42-、H2PO4-和HPO42-等4种干扰离子对装置测量结果的影响,并分别分析了C1-浓度以及H2PO4浓度与N03-浓度比值不同时,溶液中Cl-、H2PO4-引起的测量误差的大小。本文通过试验验证了肥液氮素浓度检测装置的性能,结果表明所设计的检测装置测量的可靠性,为自动混肥时氮素浓度的测量提供了一种可靠的方法。
[Abstract]:In automatic irrigation and fertilization, irrigation and fertilization can be monitored accurately, and the key to implement the monitoring of fertilizer concentration is to obtain the concentration of fertilizer solution. Therefore, it is important to realize the on-line measurement of the concentration of fertilizer solution, which is mainly measured by EC value of fertilizer solution in the existing automatic irrigation system, and the EC value of fertilizer liquid reflects the total content of medium salt. In order to realize the real-time detection of nitrogen concentration in the process of automatic mixing of fertilizer solution, a detection device was designed by ion selective electrode method, and the temperature variability of the electrode was analyzed. On the basis of this, the temperature parameter model is established, and in view of the common occurrence in the liquid of compound fertilizer, The measurement error caused by the interference ion of nitrogen concentration measurement is analyzed. The main research work in this paper is as follows: the method of nitrate ion selective electrode is used to detect the concentration of liquid nitrogen in fertilizer, and the measuring device of fertilizer liquid nitrogen concentration is designed. The detection device is composed of signal conditioning circuit, temperature sensor, data acquisition and display circuit, and the performance test test of the device is carried out. (1) the standard millivolt meter PHS-3CT is used as a contrast. The measuring accuracy of the device to the electrode response potential is tested. The maximum relative error and the minimum relative error of the measuring device are 5.2and 1.2respectively. The results show that the measuring device can accurately measure the electrode output potential in the range of 5-45 鈩，

本文编号：1657174