Five Questions to Ask Your SCADA Provider 

Do you have the right hammer to drive that screw? Anyone who has ever worked on a project knows the adage about using the right tool for the job. With so many human machine interface (HMI)/supervisory control and data acquisition (SCADA) application development packages in the marketplace, it is vital that you choose the right package to not only meet your current specifications but also implement additional features that might come up once the project is under way. Another important and challenging factor during any project is the pressure to decrease development time and cost associated with developing and deploying a system.

You should ask your SCADA provider the following five questions before settling on a specific package.

1. Does my SCADA package integrate with both existing and new hardware?

More often than not you have an existing infrastructure such as programmable logic controllers (PLCs) and remote terminal units (RTUs) to which you need to add new devices to optimize your automation system. The SCADA package that you choose must be able to communicate with legacy hardware as well as the latest hardware, such as programmable automation controllers (PACs). While OLE for process control (OPC) has become the de-facto industry standard to communicate to automation devices, there are still many sensors and instruments that require their own drivers. The ability to write your own drivers within your SCADA environment becomes a key factor in your ability to use existing hardware with new hardware.

In addition to OPC client functionality, Modbus is another popular industrial protocol that is often used to access registers on RTUs and sensors. TCP/IP and UDP are some of the other low-level protocols that you can use to communicate with different hardware. With a truly open SCADA system, you can communicate with any existing hardware while adding the newest hardware as your system progresses.

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Figure 1. This block diagram shows a typical open architecture HMI/SCADA system connecting to both legacy and the latest hardware.

2. What is the total cost incurred after I finish deploying my system?

Most SCADA vendors charge based on the number of tags you use while developing your SCADA system. A decent-sized application easily ends up using a few thousand tags. With the SCADA vendors charging a premium for each tag used, you typically develop your application with an eye toward the number of tags you have used up so far. If you do reach the limit, you have to go through the painful process of getting another purchasing order approved and devoting time toward all the overhead associated with it instead of concentrating on developing your application.

Once the development is complete, even during the deployment phase, vendors charge by the number of tags for their run-time systems, which can lead you to exceed your budget if you do not plan properly in the beginning. To reduce costs, investigate packages that do not charge by the number of tags but still deliver the performance requirements.

3. How flexible is my SCADA package when I want to add advanced analysis features?

While automation systems are designed to optimize by improving uptime and yield, SCADA systems are often required to perform advanced analysis and be flexible to implement features not typical of traditional SCADA systems. For instance, if you are acquiring vibration data and want to perform fast Fourier transform to discern if your system vibration is above the specified limits, you typically turn to separate analysis packages or, at best, invoke a programming language such as Visual Basic or even C from within your SCADA package.

If your SCADA package is flexible enough to double as a programming language to implement custom features and perform advanced analysis functions, you greatly reduce the development time and training costs associated with having to learn different packages to meet your final system specifications.

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Figure 2. Specialized development environments such as National Instruments LabVIEW provide the flexibility and integrated HMI and logic required by modern HMI/SCADA systems.

4. Can I program both the controller logic and its HMI/SCADA functionality in the same environment?

Many times you prefer to buy most of your hardware and software from a single vendor. Except for the convenience of a single purchase order, you could buy equipment from different vendors as long as the specifications meet your requirements. However, if you can program both your control hardware logic and the SCADA in the same environment, you can minimize your development time considerably. You can also save on training costs because you do not have to be proficient in two different environments.

5. Which operating systems can I use to run my application?

All HMI/SCADA systems typically run on Windows XP and now Windows Vista operating systems. However, with Windows CE and Windows XP Embedded gaining popularity because of their relatively lower costs and smaller software footprints, touch panel manufacturers have developed many touch panels to support these operating systems. A great option to keep the cost of the total system down is to use this low-cost software where possible. To do this, you need to make sure that the SCADA system can run on different operating systems. Linux and Macintosh OSs are not as popular in this field but should be considered nevertheless.