DESIGN OF CO2 CONCENTRATION MEASUREMENT SYSTEM IN GAS MIXTURE (N2 AND CO2) BASED ON THERMAL CONDUCTIVITY AND ACOUSTIC

• Main Author: Febrina, Melany
• Format: Dissertations
• Language: Indonesia
• Subjects: Fisika
• Online Access: https://digilib.itb.ac.id/gdl/view/46024
• Institution: Institut Teknologi Bandung

This dissertation reports the development of a system for measuring CO2 concentrations in a mixture of N2 and CO2 gases. Measurement of CO2 gas concentrations was carried out using two methods, namely the thermal conductivity method and the acoustic method. Both of these methods have the advantage to measure the concentration of CO2 in a gas mixture from the 0-2000 ppm, and easily. In this study, an improvisation was carried out by modifying the market IR thermopile which would later serve as a detector of thermal conductivity to measure the concentration of CO2 gas in a gas mixture. Modifications are made by releasing the IR window on the termopile, so that it can be directly exposed to CO2 gas to be detected. Thermopile is heated by giving AC current to the thermopile input pin, so that the thermopile gives heat radiation in the surrounding environment. A mixture of gases (N2 and CO2) with certain concentrations flowed into the system will absorb heat radiation from thermopile. The greater the concentration of CO2 in the gas mixture, the smaller the absorption of heat by the gas mixture, so that the output voltage from the thermopile is greater. The measurement system is compared in two ways, first using a comparison sensor MG811 and using calculations theoretically. In the initial test, CO2 concentrations were detected using a single thermopile. From the test results, termopile can measure the concentration of CO2 in the gas mixture well, it is proven that the test results can be validated with a Mason and Saxena model. These results prove that thermopile can be used as a thermal conductivity detector to measure the concentration of CO2 gas in a gas mixture. In further testing, four thermopile bridges were used with the aim of increasing the accuracy of the measurement system in detecting changes in the concentration of CO2 in the gas mixture (N2 and CO2). By using the bridge configuration of these four thermopiles, it is hoped that this measurement system can measure changes in CO2 concentrations in small orders. The test results show the measurement system can detect CO2 gas concentrations from 0-2000 ppm with relative error of 3.8%. The acoustic method used phase shifts between ultrasonic wave signals that are transmitted and received continuously as a function of the speed of sound. Phase difference is obtained by comparing the ultrasonic wave phase received by the two microphones that measure the reference gas and the gas mixture. The phase difference obtained as a function of the speed of sound is converted to a large concentration of CO2 in the gas mixture (N2 and CO2). From the test results, the measurement system can measure CO2 gas concentrations from the range 0-2000 ppm with relative error of 6.55%. From the overall results obtained, using the thermal conductivity method and the acoustic method, the measurement system that was built can measure CO2 concentrations in the gas mixture well from the range of 0-2000 ppm with easy manufacturing techniques.