微分法实现与介质无关的电容式液位测量

Utilizing differential method to implement a medium-independent capacitive liquid level measurement

电容式液位传感器因价格低廉、结构简单,广泛应用于工农业生产和医疗卫生等不同领域。由于需要预知被测液体的介电常数,且必须定期标定,因而其应用范围受到极大限制。分析了现有电容式液位测量方法存在的问题,在此基础上采用等高、对称布置,且结构参数完全相同的一对直角三角形平行平板电容器同时进行液位的测量,并利用微分方法消除了被测液体介电常数对液位高度的影响,实现了与介质无关的电容式液位测量。汽油与水的对比实验表明了本方法的有效性。

Capacitive liquid level sensor is used widely in industry,agriculture,health care and other fields due to its low price and simple structure.However,because the dielectric constant of the media should be gained before measurement and this constant must be calibrated periodically,its application is restricted greatly.Based on the analysis of the problems existing in the present capacitive liquid level measurement,two parallel plate capacitors with right-angled triangle shape and same structural parameters,which symmetrically aligned in the same height,are utilized as liquid level sensor at the same time.The differential method is adopted to eliminate the influence of the dielectric constant to the measurement and the medium-independent capacitive liquid level measurement is implemented.The experiments of pure water and gasoline show the validity of this method.