Non-invasive liquid level detection with dielectric capacitive method

• Main Authors: ZHANG,RI-GANG, 張日綱
• Other Authors: 尤芳銘
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/23085376430063824135

碩士 === 聖約翰科技大學 === 電腦與通訊工程系碩士班 === 100 === Have been many studies on the liquid level detection, but most are invasive or contact detection, it must detect the device into the liquid, it is possible electrochemical changes due to the contact surface change the nature of the liquid itself, or pollution phenomena security liquids such as liquid for medical use does not apply to such detection methods, this paper presents a dielectric capacitive non-invasive liquid level detection method and device, without physical sampling process uses a tiny electric field does not destroy the structure and state of the system, immediate and continuous research material within the message, to overcome the measurement limit of optically turbid samples or colored samples in the detection does not affect the nature of the liquid under test can be used for medical liquids or isolation and the risk of liquid, this method to solve the insecurity problem caused by the intrusive contact detection methods. The proposed detection principle, the use of the interdigital type staggered electrode sensing liquid dielectric caused by the equivalent capacitance changes, that the liquid level size of the output voltage level of value, while the liquid quasi-bit level of the formation of medium contact with the sensor board area the size of the change, it may be the output voltage is worth to know related to the liquid level in the level. Its structure device connected to the source of the oscillation circuit interdigital staggered one side of the electrode sensing devices, the other side through the filter and rectifier circuit, the output voltage of the peak. In this thesis, the first experimental measurements of the same concentration of the liquid in the different level when the output voltage value, to know the size of the output value and level height is linearly proportional to the regularity of relationship, followed by the experiments of the same species in different concentrations of the same level liquid, its output voltage value, that are within the range of fixed voltage line changes in the phenomenon, affected by the combination of the molecules of the solute and the size of the polarity, and finally observed the change of the output of different liquids, that the impedance and the phase difference be the difference between the different performance characteristics. Can be learned by the experimental results of the linear equal amount of change in the height of the liquid for each additional unit, and the simple structure of this experiment, the low power of 1.2mW (supply 3V/0.4mA), small size (99.7mm * 19.5mm *2.2mm) and cost low, linear effect in the induction of liquid from the phase difference and attenuation to know the different types of liquid through a variety of different dielectric for industry can provide a non-polluting, no chemical reaction of the liquid level detection method, and this technology for the insulation of low voltage isolation detection, safe and reliable will not have leakage, electric shock or ignite an explosion hazard arose, Looking to the future and network combination for online monitoring to save on labor, water management, agricultural irrigation management sprinkler systems management and all aspects of the application.