Design and implementation of a submerged capacitive sensor in PID controller to regulate the concentration of non-denatured ethyl alcohol

Abstract

Ethyl alcohol (ethanol) is one of the most common organic compounds used in medical and industrial applications. Because of its human amiability, ethanol has become a perfect solvent for organic matter with varying concentration levels for different purposes. Nevertheless, ethanol has a unique character that makes it evaporates at a level of temperature, which is called flash point. Storing ethanol above its flash point would reduce its concentration as well as its functionality. In this research, a device has been developed to control ethanol concentration in water. The concentration of ethanol is measured based on the signal of a square wave oscillator connected to a cylindrical aluminum capacitive sensor. Thus, the output frequency is imputed to a microcontroller programmed as a PID controller to produce the control signals that are used to operate two peristaltic pumps connected to two reservoirs containing non-denatured ethanol and distilled water, respectively. Magnetic stirrer is added to improve the dilution process. Overall, the designed sensor is able to identify various levels of ethanol concentration from 0.0-0.9 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Furthermore, the implemented controller is capable to maintain the volumetric concentration of ethanol with set point ranging from 0.0-0.5 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> within 90% of success rate.