Editing Alcohol Sensor Based on Gas-Sensitive Resistive Materials (section)

== Error Analysis ==

The uncertainty in this experiment originates from both the intrinsic properties of the MQ-3 sensor and the measurement setup, and it directly affects data consistency and interpretation.

The first source of error is baseline drift of the sensor. The MQ-3 is a metal-oxide semiconductor device whose resistance depends on temperature and surface adsorption equilibrium. During operation, incomplete thermal stabilization and the gradual evolution of adsorbed oxygen species lead to a slow change in Rs. This was reflected in the experiment as a gradual decrease in the displayed value over time. As a result, the baseline cannot be treated as a fixed reference, which introduces systematic deviation in repeated measurements.

The second source of uncertainty is the gas distribution inside the chamber. The experiment was carried out in a closed but uncontrolled environment, where ethanol transport is governed by diffusion and natural convection. This leads to a non-uniform and time-dependent concentration field. The observed signal fluctuations and secondary peaks are consistent with this transport mechanism. Consequently, even under nominally identical conditions, the sensor response may vary due to local concentration differences.

Finally, the data acquisition method introduces additional constraints. The Arduino Uno provides a 10-bit ADC, and the signal is further reduced by scaling. This limits the effective resolution and reduces sensitivity to small signal variations. In addition, the sampling interval of approximately 1 s restricts the ability to resolve rapid transient processes, particularly during the initial response stage.

Taken together, the measurements capture reproducible trends in sensor behavior, but they do not provide high-precision quantitative results. The conclusions should therefore be interpreted within a qualitative or semi-quantitative framework.