## 1 Introduction
### Contributions and Organization of the Article  
From Table 1, it can be seen that existing wireless gas level sensors display gas level data only to tank owners. However, for several reasons, LPG distribution companies are interested in knowing the LPG level data of users' tanks. In this way, in addition to having captive customers, they can avoid unfair competition, as in the case of illegal distribution of stolen gas [4; 5; 6]. Furthermore, if the exact location of each tank is known, the company can schedule optimized LPG refill routes, among other benefits. Therefore, this work has focused on the development of a wireless LPG level sensor for domestic stationary tanks with the ability to share gas level data with a remote server over the Internet. In summary, the main contributions of this development are as follows. * IoT-based sensor with the ability to display data of percentage of LPG level in a stationary tank to the user and to the refilling plant of a gas company;
* The investigated solution estimates the percentage of the LPG level in the tank in relation to the position of the magnetic field of the magnet located under the dial;
* The sensor is more precise than the existing ones in the market;
* The device is much cheaper than the ones currently on the market;
* A mobile application (app) is implemented for the developed electronic device;
* The data are shared securely, unlike the devices in Table 1, where no security strategy is specified;
* A heuristic strategy is used to sufficiently optimize the distribution routes that the distribution tanker trucks should follow;
* Using this hardware solution, the company can perform business intelligence (BI). The rest of the article is organized as follows. Section 2 shows the business concept required by a gas company and the requirements considered for the development of the IoT-based LPG level sensor. Section 3 describes the researched strategy to determine the \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline
**Designation** & **Ref.** & **Comm. Protocol** & **Coverage** & **Cyber-Security** & **Battery** & **Measur.** & **Data to** & **Precision** & **Price** \\  & & & & **Key-Liefespan** & **Daily** & **User** & **1/Plant 2** & & **(USD)** \\ \hline Levelgas & [8] & SigFox & Only in big cities & N/S & \begin{tabular}{c} 1 year \\ Zn-MnO\({}_{2}\) \\ \end{tabular} & 1 & \(\checkmark\)/x & \(\pm\)2\% & 77.50 \\ \hline El gaaas & [9] & SigFox & Only in big cities & N/S & \begin{tabular}{c} 1 year \\ Zn-MnO\({}_{2}\) \\ \end{tabular} & 1 & \(\checkmark\)/x & \(\pm\)2\% & 78.00 \\ \hline iSentinel & [10] & Wi-Fi & \begin{tabular}{c} Requires \\ internet \\ \end{tabular} & N/S & \begin{tabular}{c} 2 years \\ Li-FeS\({}_{2}\) \\ \end{tabular} & 1 & \(\checkmark\)/x & \(\pm\)2\% & 80.30 \\ \hline Redgas & [11] & Wi-Fi & \begin{tabular}{c} Limited \\ coverage \\ \end{tabular} & N/S & \begin{tabular}{c} N/S \\ PV and \\ Rechg- \\ Li-ion \\ \end{tabular} & 1 & \(\checkmark\)/x & N/S & 85.00 \\ \hline SensiGas & [12] & 4G & \begin{tabular}{c} Limited \\ coverage \\ \end{tabular} & N/S & \begin{tabular}{c} 5 years \\ Rechg- \\ Li-ion \\ \end{tabular} & 1 & \(\checkmark\)/x & N/S & 98.50 \\ \hline Gaszen & [13] & Wi-Fi & \begin{tabular}{c} Requires \\ internet \\ \end{tabular} & N/S & N/S & 1 & \(\checkmark\)/x & \(\pm\)1\% & 100.35 \\ \hline Developed & – & Wi-Fi & \
\begin{tabular}{c} Requires \\ internet \\ \end{tabular} & SSL/TLS &
\begin{tabular}{c} 1.5 years \\ Li-FeS\({}_{2}\) \\ \end{tabular} & 2 & \(\checkmark\)/\(\checkmark\) & \(\pm\)0.5\% & 40.00 \\ \hline \hline \end{tabular}  
* Data shared with user: yes (\(\checkmark\)), no (x). 2 Data shared with LPC filling plant: yes (\(\checkmark\)), no (x).  
\end{table} 
Table 1: Qualitative comparison of existing wireless sensors vs. the developed wireless sensor. percentage of liquid LPG in the tank based on the magnetic field position angle of the magnetic float meter system, considering the non-linearity of the tank volume at different levels.