Faculty of Modern Agricultural Engineering, Kunming University of Science and Technology, Kunming 650500, China.
Guangdong Provincial Key Laboratory of Conservation and Precision Utilization of Characteristic Agricultural Resources in Mountainous Areas, College of Computer Science, Jiaying University, Meizhou 514015, China.
Sensors (Basel). 2023 Jan 18;23(3):1116. doi: 10.3390/s23031116.
Online rapid detection of a fertilizer solution's type and concentration is crucial for intelligent water and fertilizer machines to realize intellectual precision variable fertilization. In this paper, a cylindrical capacitance sensor was designed based on the dielectric properties of the fertilizer solution, and an online rapid detection method of fertilizer type and concentration was proposed based on the characteristic frequency response mode. Three fertilizer solutions, potassium chloride, calcium superphosphate, and urea, were used as test objects. Ten concentrations of each fertilizer solution in the 10~100 g/L range were taken as the test fertilizer solution. Then, under the action of a series of sine wave excitation signals from 1 kHz to 10 MHz, the sensor's amplitude-frequency/phase-frequency response data were obtained. The detection strategy of 'first type, then concentration' was adopted to realize rapid online detection of fertilizer type and concentration. Experimental results indicated that the maximum relative error of the sensor stability test was 0.72%, and the maximum error of concentration detection was 7.26%. Thus, the intelligent water and fertilizer machine can give feedback on the information of a fertilizer solution in real-time during the process of precise variable fertilization, thus improving the intelligence of water and fertilizer machines.
在线快速检测肥料溶液的类型和浓度对于智能水肥机实现智能化精准变量施肥至关重要。本文基于肥料溶液的介电特性设计了一种圆柱形电容传感器，并提出了一种基于特征频率响应模式的肥料类型和浓度在线快速检测方法。以氯化钾、过磷酸钙和尿素三种肥料溶液作为测试对象，每种肥料溶液的浓度在 10~100g/L 范围内取 10 个浓度作为测试肥料溶液。然后，在 1kHz 到 10MHz 的一系列正弦波激励信号的作用下，获得传感器的幅频/相频响应数据。采用“先类型，后浓度”的检测策略，实现了肥料类型和浓度的快速在线检测。实验结果表明，传感器稳定性测试的最大相对误差为 0.72%，浓度检测的最大误差为 7.26%。因此，智能水肥机在精准变量施肥过程中可以实时反馈肥料溶液的信息，从而提高水肥机的智能化水平。
