An Introduction To SCADA Programming
While SCADA technology was developed somewhat later, similar monitoring systems have been in use since the 1960s. Such systems are collectively called DCS (Distributed Control System). DCS have conventionally been used for facilities like factories.
However, such systems are not effective in covering large geographical areas like those involved in gas transport systems.
SCADA has been specifically developed to meet requirements covering large territories. Therefore, such a system can be used in various industries and for industrial processes, including: manufacturing, water and sewage, electric power generation and mass transit. This is why SCADA programming plays such a crucial role in the system's development.
It can also be used for facility processes in private or public facilities, including: buildings, airports, ships, or space stations in order to monitor and control: HVAC, access control, and energy consumption management. The possibilities are endless.
Even with all this being said, SCADA systems are being implemented with a greater regularity in today's ultra-competitive manufacturing environments. While SCADA systems are used to perform data collection and control at the supervisory level, HMI's are typically seen as local user interfaces that allow operators to manipulate the machine or process locally, and perform SCADA programming work to customize the system.
Data collection begins at the PLC level and includes readings and equipment statuses that are communicated to a master as required. Data is then compiled and formatted in such a way that a control room operator using an interface terminal can make appropriate supervisory decisions that may be required to adjust or override normal PLC controls. The tags (data) are collected locally in the SCADA software database or into a Historian (distributed database) to allow trending and other analytical work. SCADA programming by a technician adjusts the system as needed.
These distributed measurement and control systems provide manufacturers with a flexible software solution that can be tailored to meet their specific manufacturing needs.
A SCADA system at the machine level consists of a central station for gathering data and managing the overall operation. It also has sensors (these could be Remote Terminal Units or RTUs, or Programmable Logic Controller) placed in proximity to where the action is. The RTU or the PLC collects the information locally and then passes it on to the central station, which can be located several miles away.
RTUs and PLCs today are capable of controlling the operations within their range of vision through closed loop feedback systems. The central station oversees the overall performance of the one or more RTUs/ PLCs under its control. SCADA systems also allow operators or supervisors to change the settings as appropriate at the level of the RTU or the central station. Alarming conditions like high temperature can then be recorded and displayed.
Some of the significant features of a modern SCADA system are as follows:
- User-friendly (windows/graphics) interface.
- Automatic control.
- Off-line processing.
- Integrated environments.
- Extensive Historical data manipulation.
- Extensive processing power.
- Extremely high data throughput.
- Extremely quick response.
- On-line complex electrical network analysis.
- Real time supply/demand-side economic calculations.
- Automatic voltage and power factor correction.
- Distributed processing power.
- Custom SCADA programming capability./li>
All of this requires that physical conditions be translated into machine language and then into signals that humans can read, record and analyze. Thus, a full-fledged SCADA system has to comprise of both hardware and software elements. We have already seen how today's sophisticated SCADA systems include input/output signal devices, control equipment, HMI (Human Machine Interface), networking, communication systems, databases and software.
Therefore, SCADA system development involves programming at various levels. In SCADA programming, data is collected at the RTU and has to be converted into signals, which is followed by interpreting this data that requires HMI. Often this data also has to be compiled and stored (history databases) for recognizing trends and analysis work. As a result, customized database systems have to be developed. Networks and communication systems bring in more varied requirements for SCADA programming
Add to this the fact that SCADA programming systems are still in the process of evolving. Industries are awakening to challenges like the possibility of terrorist strikes.
It is therefore necessary for research and development to be instrumental in creating a better, more foolproof system for both hardware and software levels to be integrated with SCADA programming.
Most commercial SCADA systems are now programmed using standard software languages whenever possible. Most programs are written in C, or a derived programming language. As a SCADA professional you are required to maintain the software programs on your SCADA systems, including updating software and applying bug fixes and enhancements.
It is therefore easy to see that SCADA programming has a lot of possibilities.
The current SCADA industry trend is the movement to completely open systems. The next generation of SCADA systems (and many current products) will have completely open architectures, allowing RTUs to be interchanged between systems from different vendors. The costs of SCADA systems are still dropping, while capabilities are increasing.
It is vital to understand that good SCADA programming can make a difference in your operations. However, this cannot be fulfilled unless you know the basics of SCADA systems. In order to be much better prepared for SCADA programming, you need information that has been gathered from hundreds of successful monitoring system deployments. Information that is geared towards real-world professionals, and not IT theorists.
The DPS Telecom SCADA Guide is a tutorial that teaches the fundamentals of SCADA with a practical focus. This guide also recommends product features that you can ask vendors about when you are expanding your monitoring.
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