Datasheet-Based Calibration Study of the MQ-135 Sensors for Carbon Dioxide (CO2) and MQ-8 Sensors for Hydrogen (H2)

This research conducted a datasheet-based calibration study using the MQ-135 sensor and MQ-8 sensor to measure carbon dioxide and hydrogen using datasheet information. The process of digitizing datasheet graphs into numbers that have a relationship between electrical quantities and physical quantities (R vs ppm) is carried out using webPlotDigitizer software. Based on the calculation results, a trendline of the power equation model has been obtained for the MQ-135 gas sensor and MQ-8 gas sensor respectively from the comparison of the x-axis (ADC) and y-axis (PPM), namely y_(MQ-135)=2×10^7 x^(-3.108) with a value of R_(MQ-135)^2=0.9968, and y_(MQ-8)=2533x^(-0.746) with a value of R_(MQ-8)^2=0.9875. Based on the R^2 value or coefficient of determination for each sensor, it shows that the value is close to 1, so this shows that the trendline of the power equation model used matches the sensor datasheet. The equations y_(MQ-135) and y_(MQ-8) will then be entered into the Arduino IDE program as calibration values for the MQ-135 sensor and MQ-8 sensor to obtain measurement values that are in accordance with the standardized datasheet. To improve accuracy, calibration was also performed using a reference instrument, a Carbon Dioxide Detector for CO_2 and a C-200 Pen-Type Water Quality Meter for H_2, with average errors of 1.29488% and 29.81805%, respectively. The low error value for CO_2 indicates good compliance, while the high error for H_2 is due to limitations of the reference instrument. This method can be an alternative when resources are limited, provided that the limitations of the instrument are still considered.