同心圆柱环型电容式肥液浓度传感器设计与试验

设计了一种同心圆柱环型电容式肥液浓度传感器,主要由稳压器、10MHz有源晶振、施密特触发器、电容传感器和真有效值检测器组成,检测结果以直流电压形式输出.在8×10 -1~1×10 -3mol/L浓度范围内,配置一系列待测肥液对传感器进行了试验:1)标定试验结果表明传感器输出电压与浓度对数呈线性负相关,决定系数R2>0.987;2)温度变异性试验结果表明传感器输出电压与肥液温度呈线性正相关,其决定系数R2=0.98417;3)稳定性试验结果表明同一浓度下连续测量10 h内测量最大差值为0.0003 mol/L,传感器稳定性良好;4)验证试验结果表明最大检测误差为9.8%.满足在线检测的实际应用要求.

Design and experiment of concentric cylindrical capacitive sensor for liquid fertilizer concentration

Design a concentric cylindrical capacitive sensor to detect fertilizer solution concentration,which consists of voltage regulator,10 MHz oscillator,Schmitt trigger,capacitance sensor,and true root-mean-square (RMS)detector. Test results is output in the form of DC voltage. In concentration range of 8 ×10 -1~1 × 10 -3mol/L,take a series of experiments by using a series of fertilizer solution to test sensor:1)calibration experiments show that output voltage of sensor have linear negative relationship with fertilizer solution concentration,the decision coefficient is R2>0.987;2)results of temperature variabilily test show that output voltage of sensor has linear positive relationship with temperature of fertilizer solution,the decision coefficient is R2=0.984 17;3)results of stability test show that the biggest difference value in 10 h that under the same concentration of liquid fertilizer is 0.000 3 mol/L,stability is good;4)validation test show that the maximum detection error value is 9.8%. therefore,this sensor can meet application requirement of detection of fertilizer solution concentration in practical engineering.