© 2022 Wiley-VCH GmbH.Direct methanol fuel cells are devices that convert the chemical energy of methanol fuel having high energy density directly into electrical energy by electrochemical reactions. Methanol must be supplied to the fuel cell system as an aqueous solution to complete the reaction. Therefore, controlling and adjusting of methanol ratio in the methanol-water mixture is critical for the continuity of direct methanol fuel cell performance. In this study, two fuel cell-based electrochemical sensors are developed to adjust the amount of methanol in an aqueous solution in a direct methanol fuel cell. The experimental setup is prepared for the developed sensors and the effects of parameters, such as temperature, methanol flow rate, oxidizing effect, and methanol concentration, affecting the sensor performance are observed experimentally. It is observed that the experimental results obtained in the design without air input are more stable than that of the sensor working with air. However, in air-independent design, the measurement value lost its stability after 2M concentration. The change in methanol flow rate did not cause any change in either sensor. High temperature and low methanol concentrations are found to be the main criteria for the best sensor performance.