Alcohol Sensor Based on Gas-Sensitive Resistive Materials - Revision history

Jiaxin: /* Effect of Distance in a Closed Environment */

2026-04-22T03:44:36Z

Effect of Distance in a Closed Environment

← Older revision		Revision as of 11:44, 22 April 2026
Line 195:		Line 195:
	The influence of distance was investigated by placing the alcohol wipe at 0 cm, 5 cm, 10 cm, and 15 cm from the sensing device inside the closed chamber. Representative response curves are compared in Figure 5. The screenshots show that the sensor produced clear responses at all four tested distances. This means that, within the enclosed experimental volume, ethanol vapor could still diffuse to the MQ-3 sensor and be detected effectively even when the source was not placed immediately adjacent to it. From a practical viewpoint, this is an encouraging result because it demonstrates that the alarm system remained functional across the whole tested range.		The influence of distance was investigated by placing the alcohol wipe at 0 cm, 5 cm, 10 cm, and 15 cm from the sensing device inside the closed chamber. Representative response curves are compared in Figure 5. The screenshots show that the sensor produced clear responses at all four tested distances. This means that, within the enclosed experimental volume, ethanol vapor could still diffuse to the MQ-3 sensor and be detected effectively even when the source was not placed immediately adjacent to it. From a practical viewpoint, this is an encouraging result because it demonstrates that the alarm system remained functional across the whole tested range.

	[[File:Figure5.png\|thumb\|center\|500px\|Figure 1. ~~Experimental setup~~: (a) ~~closed chamber;~~ (b) ~~assembled prototype~~.]]		[[File:Figure5.png\|thumb\|center\|500px\|Figure 5. Representative sensor output curves obtained at different alcohol-source distances in the closed chamber: (a) 0 cm, (b) 5 cm, (c) 10 cm, and (d) 15 cm.]]

	However, the effect of distance did not appear as a strictly monotonic decrease in peak value. In some trials, the 10 cm or 15 cm curves still reached relatively high displayed values. Therefore, the most reliable conclusion is not that the peak output simply decreased linearly with distance, but rather that distance influenced the response profile, including the onset of the signal, the steepness of the rise, and the stability of the curve. In general, the 0 cm and 5 cm measurements showed faster and more direct responses, while the 10 cm and 15 cm measurements more often showed delayed rises, broader peaks, or stronger fluctuations.		However, the effect of distance did not appear as a strictly monotonic decrease in peak value. In some trials, the 10 cm or 15 cm curves still reached relatively high displayed values. Therefore, the most reliable conclusion is not that the peak output simply decreased linearly with distance, but rather that distance influenced the response profile, including the onset of the signal, the steepness of the rise, and the stability of the curve. In general, the 0 cm and 5 cm measurements showed faster and more direct responses, while the 10 cm and 15 cm measurements more often showed delayed rises, broader peaks, or stronger fluctuations.

Jiaxin: /* Dynamic Response Analysis */

2026-04-22T03:44:17Z

Dynamic Response Analysis

← Older revision		Revision as of 11:44, 22 April 2026
Line 186:		Line 186:
	The Serial Plotter screenshots show that the system responded quickly after alcohol exposure. In the representative curves, the signal typically remained near the baseline for a period of time and then rose sharply once ethanol vapor reached the sensor. Figure 4(a) shows a typical rapid response at short distance, whereas Figure 4(b) shows the subsequent gradual decay. In several cases, the displayed value increased from around 15–20 to above 45 within only a short sequence of plotted points, indicating a fast practical response.		The Serial Plotter screenshots show that the system responded quickly after alcohol exposure. In the representative curves, the signal typically remained near the baseline for a period of time and then rose sharply once ethanol vapor reached the sensor. Figure 4(a) shows a typical rapid response at short distance, whereas Figure 4(b) shows the subsequent gradual decay. In several cases, the displayed value increased from around 15–20 to above 45 within only a short sequence of plotted points, indicating a fast practical response.

	[[File:Figure4.png\|thumb\|center\|500px\|Figure 4. ~~Experimental setup~~: (a) ~~closed chamber~~; (b) ~~assembled prototype~~.]]		[[File:Figure4.png\|thumb\|center\|500px\|Figure 4. Representative dynamic behavior at 0 cm: (a) rapid signal rise after alcohol exposure; (b) gradual recovery after the response peak.]]

	The recovery process was generally slower than the rising process. After the peak value was reached, the signal tended to decay more gradually, often with an extended tail instead of an immediate return to baseline. This is physically reasonable for a metal-oxide gas sensor because recovery depends on ethanol removal, desorption, and re-establishment of the surface equilibrium on the sensing layer.		The recovery process was generally slower than the rising process. After the peak value was reached, the signal tended to decay more gradually, often with an extended tail instead of an immediate return to baseline. This is physically reasonable for a metal-oxide gas sensor because recovery depends on ethanol removal, desorption, and re-establishment of the surface equilibrium on the sensing layer.

Jiaxin: /* Sensitivity and Concentration–Response */

2026-04-22T03:43:56Z

Sensitivity and Concentration–Response

← Older revision		Revision as of 11:43, 22 April 2026
Line 177:		Line 177:
	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.		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. ~~Experimental setup: (~~a~~) closed chamber; (b) assembled prototype.~~]]		[[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.		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.

Jiaxin: /* Dynamic Response Analysis */

2026-04-22T03:43:06Z

Dynamic Response Analysis

← Older revision		Revision as of 11:43, 22 April 2026
Line 186:		Line 186:
	The Serial Plotter screenshots show that the system responded quickly after alcohol exposure. In the representative curves, the signal typically remained near the baseline for a period of time and then rose sharply once ethanol vapor reached the sensor. Figure 4(a) shows a typical rapid response at short distance, whereas Figure 4(b) shows the subsequent gradual decay. In several cases, the displayed value increased from around 15–20 to above 45 within only a short sequence of plotted points, indicating a fast practical response.		The Serial Plotter screenshots show that the system responded quickly after alcohol exposure. In the representative curves, the signal typically remained near the baseline for a period of time and then rose sharply once ethanol vapor reached the sensor. Figure 4(a) shows a typical rapid response at short distance, whereas Figure 4(b) shows the subsequent gradual decay. In several cases, the displayed value increased from around 15–20 to above 45 within only a short sequence of plotted points, indicating a fast practical response.

	[[File:Figure4.png\|thumb\|center\|500px\|Figure 1. Experimental setup: (a) closed chamber; (b) assembled prototype.]]		[[File:Figure4.png\|thumb\|center\|500px\|Figure 4. Experimental setup: (a) closed chamber; (b) assembled prototype.]]

	The recovery process was generally slower than the rising process. After the peak value was reached, the signal tended to decay more gradually, often with an extended tail instead of an immediate return to baseline. This is physically reasonable for a metal-oxide gas sensor because recovery depends on ethanol removal, desorption, and re-establishment of the surface equilibrium on the sensing layer.		The recovery process was generally slower than the rising process. After the peak value was reached, the signal tended to decay more gradually, often with an extended tail instead of an immediate return to baseline. This is physically reasonable for a metal-oxide gas sensor because recovery depends on ethanol removal, desorption, and re-establishment of the surface equilibrium on the sensing layer.

Jiaxin: /* Sensitivity and Concentration–Response */

2026-04-22T03:42:57Z

Sensitivity and Concentration–Response

← Older revision		Revision as of 11:42, 22 April 2026
Line 177:		Line 177:
	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.		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 1. Experimental setup: (a) closed chamber; (b) assembled prototype.]]		[[File:Figure3.png\|thumb\|center\|500px\|Figure 3. Experimental setup: (a) closed chamber; (b) assembled prototype.]]

	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.		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.

Jiaxin: /* Team Members and Contributions */

2026-04-17T05:20:31Z

Team Members and Contributions

← Older revision		Revision as of 13:20, 17 April 2026
Line 1:		Line 1:
	== Team Members and Contributions ==		== Team Members and Contributions ==

	This project was completed collaboratively by four team members, with responsibilities ~~divided~~ as follows:		This project was completed collaboratively by four team members, with responsibilities assigned as follows.

			Lyu Jiaxin was responsible for the analysis of sensor characteristics and the web content development.

			Yue Yucheng was responsible for the design and implementation of the alcohol detection and alarm system using Arduino.

			Zhang Ningxin was responsible for the introduction and the theoretical working principle of the sensor.

			Zhong Yihui was responsible for the experimental system setup and data analysis, including the analysis of sensitivity, dynamic response, and distance effects.

			All team members jointly participated in the experimental design, experimental procedures, and data acquisition.

	== Introduction ==		== Introduction ==

Jiaxin: /* Appendix */

2026-04-17T05:09:45Z

Appendix

← Older revision		Revision as of 13:09, 17 April 2026
Line 222:		Line 222:
	[6] Dey, A. (2018). Semiconductor metal oxide gas sensors: A review. Materials Science and Engineering: B, 229, 206–217. https://doi.org/10.1016/j.mseb.2017.12.036		[6] Dey, A. (2018). Semiconductor metal oxide gas sensors: A review. Materials Science and Engineering: B, 229, 206–217. https://doi.org/10.1016/j.mseb.2017.12.036

	== Appendix ==		== Appendix A. MQ-3 Sensor Datasheet ==

			The complete technical datasheet of the MQ-3 gas sensor is provided below for reference.

			* [[File:MQ-3.pdf\|Download MQ-3 Datasheet]]

			Source: Hanwei Electronics Co., Ltd., "MQ-3 Gas Sensor Technical Data", available at: http://www.hwsensor.com

Jiaxin: /* Limitations and Future Improvements */

2026-04-17T05:07:55Z

Limitations and Future Improvements

← Older revision		Revision as of 13:07, 17 April 2026
Line 207:		Line 207:
	== Limitations and Future Improvements ==		== Limitations and Future Improvements ==

	The current system ~~is able to demonstrate~~ alcohol detection and basic response behavior, but its performance is ~~constrained~~ by ~~several factors related to~~ measurement ~~design~~ and data ~~interpretation~~.		The current system demonstrates alcohol detection and basic response behavior, but its performance is limited by the lack of calibration, uncontrolled measurement conditions, and restricted data resolution. The sensor output is expressed as a scaled ADC value rather than a calibrated ethanol concentration, which prevents quantitative interpretation of the results. In addition, the use of a simple closed chamber leads to diffusion-dominated and non-uniform vapor distribution, reducing repeatability across measurements. The data acquisition system, including limited ADC resolution and simplified processing, further constrains the precision of dynamic analysis. Future improvements should focus on introducing calibration, improving environmental control, and enhancing data acquisition and analysis methods to achieve more reliable and interpretable measurements.

	~~First, the system lacks calibration, and the~~ sensor output is expressed as a scaled ADC value rather than a ~~physically defined~~ ethanol ~~concentration. Without a defined relationship between signal and~~ concentration, the results ~~cannot be interpreted quantitatively and are only valid for relative comparison within the same experimental conditions~~. ~~Future work should establish calibration using known ethanol concentrations~~, ~~so that~~ the ~~sensor response can be related to a physical unit and compared across different measurements.~~

	~~Second, the measurement environment is not well controlled. The experiments were conducted in~~ a simple closed chamber~~, where ethanol transport is governed by diffusion and mixing rather than a stable concentration field. This~~ leads to ~~spatial~~ and ~~temporal variations in~~ vapor distribution, ~~which reduces~~ repeatability ~~and introduces uncertainty when comparing different distances~~. ~~A more controlled chamber with fixed geometry and more stable conditions would improve consistency and allow clearer interpretation of the results.~~

	~~Third, the dynamic response and~~ data acquisition ~~are~~ limited ~~in precision. Rise and recovery behavior are observed from the plots but not extracted using a defined criterion,~~ and ~~the use of a 10-bit ADC with~~ simplified ~~scaling reduces effective resolution. In addition~~, ~~environmental factors such as temperature and humidity are not monitored. These factors together limit~~ the ~~accuracy~~ of ~~the~~ dynamic analysis. Future ~~work~~ should ~~define response metrics explicitly~~, ~~improve~~ data acquisition, and ~~include basic environmental monitoring~~ to ~~enhance the reliability of the~~ measurements.

	== References ==		== References ==

Jiaxin: /* Limitations and Future Improvements */

2026-04-17T05:06:51Z

Limitations and Future Improvements

← Older revision		Revision as of 13:06, 17 April 2026
Line 214:		Line 214:

	Third, the dynamic response and data acquisition are limited in precision. Rise and recovery behavior are observed from the plots but not extracted using a defined criterion, and the use of a 10-bit ADC with simplified scaling reduces effective resolution. In addition, environmental factors such as temperature and humidity are not monitored. These factors together limit the accuracy of the dynamic analysis. Future work should define response metrics explicitly, improve data acquisition, and include basic environmental monitoring to enhance the reliability of the measurements.		Third, the dynamic response and data acquisition are limited in precision. Rise and recovery behavior are observed from the plots but not extracted using a defined criterion, and the use of a 10-bit ADC with simplified scaling reduces effective resolution. In addition, environmental factors such as temperature and humidity are not monitored. These factors together limit the accuracy of the dynamic analysis. Future work should define response metrics explicitly, improve data acquisition, and include basic environmental monitoring to enhance the reliability of the measurements.

	~~== Limitations and Future Improvements ==~~

	== References ==		== References ==

Jiaxin: /* Error Analysis */

2026-04-17T05:06:14Z

Error Analysis

← Older revision		Revision as of 13:06, 17 April 2026
Line 199:		Line 199:
	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 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 limitation arises from the absence of calibration. The recorded signal is a scaled ADC value rather than a physically defined concentration. Without establishing a mapping between sensor output and ethanol concentration, the measurement lacks an absolute reference. Therefore, the results can only support relative comparison within the same experimental condition and cannot be extended to quantitative analysis.		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.

	~~The third~~ 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.

	The fourth issue concerns the definition of distance. The alcohol wipe does not behave as a stable point source, and its evaporation rate changes with time and exposure. The resulting concentration field depends on both evaporation dynamics and spatial mixing, rather than purely on geometric distance. Therefore, distance cannot be treated as an independent variable, which limits the rigor of distance-based comparisons.

	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.		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.