电容式液位传感器偏心特性研究

Research on eccentricity characteristics of capacitive liquid level sensor

针对偏心情况下的电容式液位传感器,提出了一种输出电容量的理论计算方法。给出了偏心电容式液位传感器的等效电路,分析了输出电容量的各组成分量;利用保角变换法将一个平面上的2个偏心圆转换为另一平面上的2个同心圆,推导了以空气为电介质的偏心电容量计算公式,进而推导了传感器输出电容量与液位高度、偏心距离的数学关系式。设计了专门的实验装置,验证了理论分析的正确性。结果表明,传感器输出电容量与液位高度呈线性关系;同一液位高度下,偏心距离增大会引起输出电容量增大;偏心距离的影响随着液位高度的增加而逐渐减小,直至满量程状态时,偏心距离对电容量的影响为零。

A theoretical calculation method of output capacitance is proposed for the capacitive liquid level sensor under eccentric condition.The equivalent circuit of the eccentric capacitive liquid level sensor is given,and the components of the output capacitance are analyzed.The conformal transformation method is used to convert two eccentric circles on one plane into two concentric circles on another plane,the calculation formula of the eccentric capacitance with air as the dielectric is deduced,and then the mathematical relationship between the sensor output capacitance and the liquid level height or the eccentric distance is deduced.A special test device was designed to verify the correctness of the theoretical analysis.The results show that the output capacitance of the sensor has a linear relationship with the liquid level height,and the increase of the eccentric distance will cause the output capacitance to increase under the same liquid level height,the influence of the eccentric distance will gradually decrease with the increase of the liquid level height,and the influence of the eccentric distance on the capacitance will be zero until the liquid level reaches the full scale state.