## 2 System Architecture
### SCADA System  
This machine integrates a SIEMENS WinCC SCADA system (Supervisory Control and Data Acquisition) [21] running on a Windows PC server. This system manages three main functions: (i) interfaces the UPV test equipment and the PLC; (ii) exports the data to a CSV file via custom VBS (Visual Basic Scripts); (iii) serves as a higher-order Human-Machine Interface (HMI).  
The developed SCADA main control panel is illustrated on Figure 10. Its layout reproduces the machine local HMI panel. A list of possible machine error messages is presented in Table 4.  
Figure 10: HMI and SCADA main control panels. 1-Input parameters—stone block; 2-Input parameters—power source; 3-Input parameters—csv file for data storing; 4-Measurement Data output from ultrasonic tomography; 5-Measurement Data output from electric tomography; 6-Output information about the number of readings; 7-Output field allocated for machine failures/messages.  
Figure 9: Prototype implementation (wiring diagram).  
The laboratorial setup was implemented wih two Programable Logic Controllers (PLCs) working in tandem to simulate an industrial network. The main PLC is responsible for running the main tasks, and the other PLC runs the electric tomography.  
Each actuator was simulated by using two digital bits, one for each movement direction, the electric tomography used two-input and two-output electrodes, as the objective of this prototype is testing its operational capacity (proof-of-concept setup).  
The main PLC controller is the SIEMENS S7-1200 [22] with the following components:  
-  CPU 1214C AC/DC/Rly (6 ES7 214-1 BG31-0 XB0) [23]  
- 14 digital inputs 0-24 V  
- 10 digital outputs 0-24 V  
- 2 analog inputs 0-10 V (10 bits)  
-  AQ1 signal board (6 ES7 232-4 HA30-0 XB0) [24]  
- 2 analog outputs 0-10 V (12 bits)  
The secondary PLC controller is the SIEMENS S7-300 [25] with the following components:  
-  PS 307 2A (6 ES7 307-1 BA01-0 AA0) [26]  
-  CPU 315-2 DP (6 ES7 315-2 AH14-0 AB0) [27]  
-  CP 343-1 Lean (6 GK7 343-1 CX10-0 XE0) [28]  
-  Industrial Ethernet Communication  
-  CP 342-5 (6 GK7 342-5 DA03-0 XE0) [29]  
-  PROFIBUS Communication  
-  DI 8/DO 8 \(\times\) 24 VDC/0.5 A (6 ES7 323-1 BH01-0 AA0) [30]  
- 8 digital inputs 0-24 V  
-  AI 4/AO 2 \(\times\) 8 BIT (6 ES7 334-0 CE01-0 AA0) [31]  
- 4 analog input 0-10 V (8 bits)  
- 2 analog outputs 0-10 V (8 bits)  
The SIEMENS KTP600 Basic Color PN (6 AV6647-0 AD11-3 AX0) [32] is used in the prototype as the Human-Machine Interface (HMI)-the (3) in Figure 12.  
Figure 12: Laboratorial setup—PLCs controllers. 1-Siemens S7-1200; 2-Siemens S7-300; 3-SIEMENS KTP600 Basic Color PN; 4-FESTO Input/Output Simulator.  
A SIEMENS WinCC Advanced SCADA system [21] is integrated in the prototype-the (1) in Figure 11-to fulfill three objectives: (i) online supervision and control of the entire machine; (ii) management of the communication between both PLCs--via VBS (Visual Basic Scripts); (iii) bridge the communication between the UPV test equipment and the main controller.  
Ultrasonic tomography uses the Proceq Pundit Lab+ test equipment [20]-the (2) in Figure 11-and two ultrasonic 54 kHz transducers-the (3) in Figure 11.  
Finally, electric resistivity tomography uses the EUTRON ATR700 SA [19]-the (4) in Figure 11--(4)) and test brass-electrodes with spring-contact tips to ensure effective electrical contact between testing surfaces-the (5) in Figure 11.