Development of a measurement system of ethanol gas based on TGS-2600, TGS-2603, and MQ-138 sensors

Ethanol is a volatile organic compound of carbon, hydrogen, and oxygen that forms a hydroxyl group with the C2H5OH formula. Ethanol is a carcinogen substance having an impact on human health. Ethanol measurement in the laboratory takes a long time. Regarding this, instrumentation can measure ethanol with high precision, and a fast response time is needed. This study focuses on developing the ethanol measurement system based on multi-sensitivity alcohol sensors, such as the Figaro TGS-2600 sensor, Figaro TGS-2603 sensor, and MQ-138 analog sensor. The system is accomplished with an Arduino Mega2560 microcontroller as a data transfer system. The data was collected using a sonication method that utilizes ultrasonic waves with a frequency range of 20 kHz - 20 MHz to perform the evaporation process from the ethanol solution. This method converted the solution into a gaseous substance. Then, the measurement was carried out for different ethanol concentrations. The measured concentration is shown by the resistance ratio between ethanol and air—the ratio decreases for a high ethanol concentration. Then the obtained ratio was converted into the calculated concentration. The evaporated ethanol concentration was measured by balancing the ethanol before and after the sonication process. The measured and calculated concentrations are then plotted into a calibration graph. The relationship between both concentrations is found linearly. The system works well for measuring ethanol, depending on the used sensor. Among the sensor, MQ138 is the best to measure ethanol in the range of 0-78 ppm. Meanwhile, the sensor of Figaro TGS-2600 and TGS-2603 can measure ethanol with concentrations of 0-3 ppm and 0-42 ppm, respectively.