# A Sensor Data-Driven Decision Support System for Liquefied Petroleum Gas Suppliers
## 3 LPG Consumption Monitoring and Sensory Data Collection  
The background for the created system was the measuring infrastructure collecting sensory data processed by the DSS. LPG is stored in tanks, which are equipped with a measuring system that allows knowing the gas level in the tank. Based on the lowering of the gas level, consumption is calculated. The mechanism of consumption calculation should be insensitive to naturally occurring phenomena, like the instability of the LPG surface or the inaccuracies of the measurement system. Consumers use gas in a volatile phase in most cases. Therefore, the installation can be equipped with a gas meter, which allows more precise measurement of consumption. Furthermore, complementing tank monitoring with a gas meter enables comparative analysis for the values obtained from both measuring instruments. It allows identifying potential irregularities such as: LPG leakage, gas theft, gauge blockage, and gas meter malfunction.  
Measurements of the LPG level in the tank can be carried out manually by reading the dial or automatically. There are several methods for monitoring the LPG level in the tank, including: a mechanical system with a float [29; 30], a pressure probe, measuring the difference between air pressure and pressure on the bottom of the tank [31], a magnetostrictive level gauge [32], radar technology [33], and IR imaging [34].  
The most popular method uses a mechanical system placed inside the tank, which transforms the movement of the float placed on the movable arm into the rotation of the magnetic element in the head located on the top of the tank. Outside the tank, in the head, there is a dial with a pointer indicating the measurement level. The dial and the internal mechanical system are connected magnetically, without physical contact, due to the need to keep the tank leakproof. During the deployment of the automatic meter reading (AMR) system, the dial is replaced by an electronic device containing a Hall effect sensor (reading the direction of the magnetic field lines) and a communication module used for sending measurements wirelessly to the acquisition system. These electronic devices are battery powered and should have a long life time (a min. five years); therefore, the communication model must be energy saving. Particular types of devices use various transmission techniques: Internet of Things protocols (e.g., LoRa [35], Sigfox [36]), local radio transmission using the ISM band (e.g., WM-BUS), or satellite communication (e.g., Hiberband [37]). In the case of local radio transmission, radio frames transmitted by these devices are received by concentrators and then retransmitted to the acquisition system using the cellular network.  
The acquisition system platform supports devices operating in many protocols, as well as many types of devices, using a system of plug-ins. Processed data are stored in a database, from which they are read by end user applications. Processed data are also sent to supporting systems such as the system presented in this work. The described monitoring environment and the possibilities of the measurement acquisition system configuration are illustrated in Figure 1.