1. Process Monitoring and Control Systems
Lecture Number 8
Process Monitoring and Control Systems

2. In this session…
In this session, you will learn about process monitoring and control systems

3. Learning outcomes At the end of this session you should be able to:
Understand the role of SCADA and HMI systems
Understand the basic application of SCADA and HMI systems

4. Introduction Process Monitoring and Control Systems
By C Mayhew

5. What are They? SCADA - Supervisory Control and Data Acquisition
DCS - Distributed Control System
HMI - Human Machine Interface

6. What are They? SCADA: Supervisory Control and Data Acquisition
A system for monitoring and controlling real time data, generally in a graphical form.
The SCADA system is configured using software specifically for the graphical design.

7. What are They? SCADA: Supervisory Control and Data Acquisition
Example software includes:
InTouch
WinCC

8. What are They? DCS: Distributed Control System
Rather than using a single controller at a central location, a Distributed Control System has multiple control devices distributed around the system.
It is common to see DCS and SCADA Systems compared. SCADA can run on a DCS or Centralized Control System.

9. What are They? HMI: Human Machine Interface
A HMI is used to build a graphical application of the process and give an operator visual control and monitoring of a process at a local level on a single integrated device.
The HMI below is a Siemens device. The HMI is programmed using dedicated software.

10. HMI Introduction Tags Siemens define a HMI Tag as:
A tag is a defined memory area that is used to read and write values. Those tags can be accessed from the PLC or using the HMI device. We distinguish between external tags (process tags) and internal tags, depending on whether or not the tag is interconnected with the PLC

11. HMI Introduction
Tags
The figure below show a simple Tag Table in an Siemens S7 1214C PLC

12. HMI Example KTP600 with S7 1214C PLC

13. The overall look of the screen can be configured
HMI Introduction
Screens
The overall look of the screen can be configured

14. Sub screens from the main (Root) screen are added
HMI Introduction
Screens
Sub screens from the main (Root) screen are added

15. HMI Introduction
Screens
Buttons can be added

16. The screen is then produced
HMI Introduction
Screens
The screen is then produced

17. Application Components
HMI Introduction
Application Components
We can place various objects on the screen. For example, an I/O Field.

18. Application Components
HMI Introduction
Application Components
We can place various objects on the screen. For example, an I/O Field.
This allows us to show data on the screen read from a data word in the PLC

19. Application Components
HMI Introduction
Application Components
The Tags for the PLC and the HMI are used to link the display item to the data required.
HMI Tag
I/O Field Setup
PLC Tag
Symbolic Address
(PLC Tag)
Absolute Address

20. HMI Introduction Application Components
We can perform Linear Scaling on the Tag
HMI Tag

21. HMI Introduction Full Application
We can connect external devices to the PLC and see them working graphically in the HMI. In the previous example, the temperature of the PT100 probe in the figure below could be displayed on the HMI.

22. HMI Introduction Full Application
We can connect external devices to the PLC and see them working graphically in the HMI. In the previous example, the temperature of the PT100 probe in the figure below could be displayed on the HMI.
We can just as easily add controls to the screen to control the process. For example, start, stop and set temperatures, levels etc.

23. Application Components
HMI Introduction
Application Components
There are lots of other features we could add to the system. These include:
Photographs
Graphs
Alarms
Animations
Buttons
Switches
Recipes

24. Summary
You should now have a basic understanding of the application of SCADA and HMI systems.