# Integrating Digital Twins of Engineering Labs into Multi-User Virtual Reality Environments
## 3 Workflow for the Development of a New Crawling Engine Experience
### Development of the Technological Solution
#### 3.2.1 Signal Identification and Sensing  
In the first stage, the signals needed to replicate and improve the laboratory experiment were identified. It was decided to extend the monitoring to four key temperatures: intake, exhaust, oil, and ambient, using more accurate thermocouples. Also, a pressure sensor was added to evaluate the conditions of the compression chambers in the absence of combustion, and a sensor to measure the rotational speed of the engine shaft. These additions enriched the analysis and understanding of engine operation.  
Then, the monitoring system was improved by implementing Siemens LOGO! 7 PLC, matching the student experience to what is traditionally used in the industry. PT-100 RTD thermocouples were selected, capable of operating in a temperature range from \(-200\)\({}^{\circ}\)C to \(500\)\({}^{\circ}\)C, with AM2 RTD extension modules. For safe and efficient integration of the signals, the following configuration was made in the PLC for a correct temperature reading.  
To expand the capabilities of the PLC, additional AM2 modules were integrated, allowing the recording of analog signals from 0 to 20 mA or 4 to 20 mA. This allowed the addition of a pressure sensor in the compression chambers, as well as the connection to the frequency inverter to measure the RPM of the motor, eliminating the need for external instruments. In Figure 3, the setup of the sensing system, motors, and VFD is shown, and in Table 1, the list of equipment is provided.  
Figure 4 presents the configuration of the program implemented in the PLC, designed to guarantee the correct acquisition and processing of the signals coming from the sensors. First, the operating range within which the recorded analog signals can fluctuate is established, ensuring that the data is interpreted accurately. Subsequently, through a conversion based on simple rules of three, the analog values obtained are transformed to their corresponding scale, allowing the correct visualization and interpretation of them within the system. This procedure is essential to normalize the data and facilitate their integration  
\begin{table}
\begin{tabular}{c c} \hline
**Equipment** & **Specifications** \\ \hline \multirow{4}{*}{(1) PLC} & Siemens Logo 7, 2 LOGO power (Nuremberg, Germany), \\  & with 2 extensions AM2 RTD, 2 extensions AM2 and \\  & 1 extension AM2 AQ \\  & 4 thermocouples from \(-50\)\({}^{\circ}\)C to \(300\)\({}^{\circ}\)C, 1 Pressure \\  & translator 0 to 60 bar \\ \multirow{2}{*}{(3) Variable Frequency Drive} & SINUS PENTA 0020 4T BIK2 (Enerntronica Santerno, Poggio Piccolo, Italy) \\  & Model T1 CR 160M2-2 B3 (OMEC Motors, Arnhem, The Netherlands) \\ \multirow{2}{*}{(5) Combustion engine} & DEUTZ F3L912W (Beinei Deutz License Plant, Beijing, China) \\ \hline \end{tabular}
\end{table}
Table 1: List of equipment.  
Figure 3: Sensor mounting.  
into the digital environment, ensuring a consistent representation of the physical variables monitored in real time.