# Wireless Data Acquisition System with Feedback Function
## 2 Materials and Methods  
### Analysis of Existing Concepts for Building a Wireless DAS for Low-Power GEPPs  
In the block diagram in Figure 1, the authors tried to summarize the currently used typical solutions for building wireless data acquisition systems (DASs) for GEPPs with a power of up to 10-20 kW. In Figure 1, the red lines indicate wires connecting remote DAS nodes. The abbreviations in the diagram are deciphered as follows: SVS--supply voltage shaper, AS--analog sensor, VA--voltage amplifier, DS--digital sensor, ADC--analog to digital converter, MCU--microcontroller unit, DSD--data display, recording, and storage unit (most often a laptop, sometimes LCD indicator and microSD card), and TX--data transmitter (an ESRM can be used, but more often a GSM module, a Wi-Fi module, a Bluetooth module, or IoT is used). Figure 1: Block diagram of typical wireless data acquisition system. The disadvantage of the standard circuit is the galvanic connection between all components of the DAS and GEPP via common wire (Gnd). This does not allow us, in particular, to measure the voltage of each of several series-connected batteries in the described system. In low-power GEPPs with a nominal main battery voltage of, for instance, 48 V, it is typical to use sections of four 12 V batteries connected in series. Since over time, the parameters of power batteries vary more and more, a case may occur when the total battery voltage is normal, while individual batteries will be overdischarged, and others will be overcharged. This can cause the electrolyte to \"boil over\" and sulfation of the plates, followed by an avalanche-like increase in the internal resistance and voltage of the battery, its overheating, and a decrease in the ability of the entire main battery to accept and release charge. Therefore, monitoring the voltage of each battery is absolutely necessary. In a typical design, the supply voltages for all of the central and peripheral DAS modules are generated from the main battery voltage using a supply voltage shaper (SVS). The lines marked in red feed sensors farther away from the main DAS module and are longer, as are the lines from the shunt and from the main battery, and the lines from the central DAS module to the DSD module. The lines connecting the common peripheral wires to the central DAS module are also longer. The signal lines of the sensors are also longer, often consisting of two or three conductors, depending on the type of interface. The total number of lines for connecting one digital sensor can reach 5. For complete diagnostics, in addition to voltage, it is also necessary to measure the temperature of each battery. Temperature sensors must have thermal contact with each battery. It turns out that the DAS, being wireless, actually has the form of a device to which a large number of long wires are connected, even if a modern specialized DAQ card is used to connect sensors, such as National Instrument USB-6009 (Austin, TX, USA) with 8 inputs and a 14-bit multisystem I/O. In addition, regarding the reasons given in Section 1, when using IoT, Wi-Fi, and GSM technologies, failures and interruptions in data transmission are possible. Among the disadvantages of all of the DASs considered is the absence in their composition of at least the simplest means of diagnosing the serviceability of their components. It is also unknown how the system will behave and what will be recorded in the DAS monitoring protocol discussed in Section 1 if the cables of one or more sensors fail or break. Many of the data collection systems discussed in this review allow you to collect and process data in real time, as well as exchange data with a central control system that uses artificial intelligence to speed up the response to events. However, small GEPPs with a power of up to 10-20 kW, as a rule, are not connected to the central control system, and the recorded data, due to the lack of full-time employees, are processed with a time delay of several days or even weeks.