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

=== Sensitivity and Concentration–Response ===
The experimental results show that the MQ-3-based system had a clear and repeatable response to alcohol vapor. After warm-up, the baseline output usually remained around 15–20 in clean air. A representative stabilized baseline is shown in Figure 3. Once the alcohol wipe was introduced, the displayed value in many trials increased rapidly to the range of approximately 40–60, indicating a strong response to the presence of ethanol vapor. This behavior is consistent with the working mechanism of the MQ-3 sensor, in which alcohol exposure increases the conductivity of the sensing layer and produces a larger output signal.

[[File:Figure3.png|thumb|center|500px|Figure 3. Representative baseline signal after sensor warm-up, showing a relatively stable initial reading in the range of about 15–20 before alcohol exposure]]

Although the displayed value was written in a percentage-like format, it should not be interpreted as the exact alcohol concentration. In this system, the signal shown on the LCD was a scaled ADC reading used to visualize relative changes and to trigger an alarm when the threshold was exceeded. This design is appropriate for a warning-oriented device, whose main purpose is to determine whether alcohol exposure has risen above a practical limit rather than to perform rigorous quantitative concentration measurement.

From the perspective of concentration–response behavior, the screenshots support a clear qualitative conclusion: higher local alcohol exposure produced higher sensor output. Even without converting the readings into calibrated ppm values, the experiments clearly demonstrate that the system was sufficiently sensitive to distinguish between background air and alcohol-rich conditions. Therefore, for the intended application of alcohol over-threshold warning, the sensor showed adequate practical sensitivity.