## 3 Multi-Sensor Architecture
### Components and Equipment
#### 3.1.2 Sensors  
Used sensors for different air component targets are shown on Table 3. The MQ-137 is a gas sensor that is specifically designed for the detection of ammonia (NH\({}_{3}\)) gas in the air. It belongs to the MQ series of gas sensors, which are widely used for various applications in detecting different gases. The MQ-137 sensor is particularly sensitive to ammonia and can be used for air quality monitoring, industrial safety, and environmental monitoring. \begin{table}
\begin{tabular}{c c c} \hline \hline
**General** & **Description** & **Features** \\ \hline \multirow{7}{*}{\begin{tabular}{c} Open-Source IoT \\ Automation \\ System: \\ OpenHAB \\ (open Home \\ Automation Bus) \\ \end{tabular} } & \multirow{7}{*}{\begin{tabular}{c} An open-source home automation \\ platform designed to provide a \\ framework for integrating and \\ controlling various smart home devices \\ and technologies. It allows users to connect and manage devices from \\ different manufacturers, protocols, and \\ technologies under a single, unified \\ platform. OpenHAB supports a wide \\ range of devices and can be extended \\ through add-ons and bindings. \\ \end{tabular} } & \multirow{7}{*}{\begin{tabular}{c} Vendor-Neutral: OpenHAB is designed to be \\ vendor-neutral, allowing users to integrate devices \\ from different manufacturers and protocols. \\ \end{tabular} } \\  & & \\ \multirow{7}{*}{\begin{tabular}{c} Extensible: The platform is highly extensible through \\ add-ons and bindings that support a variety of devices \\ and technologies. \\ \end{tabular} } & \multirow{7}{*}{\begin{tabular}{c} Rule Engine: OpenHAB includes a rule engine that \\ allows users to define automation rules and logic for \\ smart home scenarios. \\ \end{tabular} } \\  & & \\ \multirow{7}{*}{\begin{tabular}{c} User Interfaces: Multiple user interfaces are available, \\ including a web-based UI, a mobile app, and support \\ for voice control through integration with voice \\ assistants like Amazon Alexa and Google Assistant. \\ \end{tabular} } \\  & & \\ \multirow{7}{*}{\
\begin{tabular}{c} Multi-Protocol Support: OpenHAB supports various \\ smart home protocols, including MQTT, Z-Wave, \\ Zigbee, KNX, and more. \\ \end{tabular} } & \multirow{7}{*}{
\begin{tabular}{c} Community and Documentation: An active \\ community provides support, and comprehensive \\ documentation is available to help users set up and \\ configure their smart home systems. \\ \end{tabular} } \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._ \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Air Component** & **Sensor** & **Operating** & **Sensitivity** & **Analog Output** & **Calibration** \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} Ammonia (NH\({}_{3}\)) \\ \end{tabular} } & \multirow{3}{*}{MQ-137} & \multirow{3}{*}{5 V} & \multirow{3}{*}{High} & \multicolumn{2}{c}{can be read by a} \\  & & & & microcontroller or & \\ \cline{1-1} \cline{4-5}  & & & & analog-to-digital & \\ \cline{1-1} \cline{4-5}  & & & & converter & \\ \hline \multirow{3}{*}{
\begin{tabular}{c} Hydrogen \\ Sulfide (H\({}_{2}\)S). \\ \end{tabular} } & \multirow{3}{*}{MQ-136} & \multirow{3}{*}{5 V} & \multirow{3}{*}{High} & \multicolumn{2}{c}{proportional to the} \\  & & & & concentration of H\({}_{2}\)S gas & \\ \cline{1-1} \cline{4-5}  & & & & & calibration \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Used sensors for different air component targets. The MQ-136 sensor is a gas sensor specifically designed for the detection of hydrogen sulfide (H\({}_{2}\)S) gas in the air. Like other sensors in the MQ series, the MQ-136 is sensitive to a specific gas and provides an analog voltage output that can be measured by a microcontroller or analog-to-digital converter. This sensor is commonly used in applications where monitoring hydrogen sulfide levels is crucial for safety and environmental reasons. The MQ-136 sensor uses a tin dioxide (SnO\({}_{2}\)) semiconductor material that changes its resistance in the presence of hydrogen sulfide gas.