SCADA/MES SYSTEMS

Process plant floor data – who owns it? How do you get to it? How quickly? Your questions answered BY John Bailey

Do you remember your first computer system for real time data? I do; I was involved in the early Kent and Argus systems. Many can remember the time before PCs in SCADA – large computer systems that grew into dinosaurs before spawning the modern VAX, UNIX and DCS systems.

In the early days (ca 1985) PCs were regarded by older generation engineers as toys; low cost but low functionality units only useful for casual applications. By 1990 these `toys’ were serious, mid-range SCADA systems and we saw a pecking order emerging for new suppliers.

Few PC-based SCADA suppliers had developed systems around Microsoft Windows. Ironically, most, and especially the established vendors, regarded them as a nonsense, rubbishing the very concept in serious SCADA. However, Microsoft Windows did catch on, winning the battle against the superior OS/2. Windows suppliers proceeded to turn the SCADA world upside down.

The established PC SCADA vendors reacted and, eventually, developed their own Windows-based offerings. In fact, the introduction of Windows NT even allowed DCS suppliers to down-size from their VMS and UNIX systems.

So, is it all done now? Are all PC-based SCADA systems the same? Has the Microsoft factor levelled the playing field so much that you could choose any supplier? In a recent survey, the key buying criteria from end users so emphasised good support that the answer was `yes’. Support, company size, reference lists and future vision played as large a role as the software itself.

That is until you analysed the undercurrents in what users and integrators are asking for. One of these is easier and quicker access to plant information. People are giving it a new name – Process Information Management Systems (PIMS – MES has too wide a meaning; it’s currently disappearing from our vocabulary).

So, it’s no longer enough to bring data back to one point, such as a SCADA system. Information has to be available to everybody (securely and in different forms), at all points, quickly. The need for flexible manufacturing has reduced tolerance of any delay.

For example, production reports detailing how an order was manufactured, by whom and using what materials – combined with a picture of the process profile during critical stages – are needed at the touch of a button. Then again, some supervisors want Internet/Intranet browser facilities to view status of production at plants world-wide.

PC-based control systems are next – the so-called soft logic. By taking the functionality of SCADA and running it alongside IEC 1131-programmed control engines on the PC, a big step forward has been made.

The implications are clear – but beware. PC-based control is only for those who understand both the advantages and the drawbacks. Windows NT v4.0 has the real time extensions from Venturecom. Hard disks are capable of being replaced by Flash ROM and will utilise VenturCom’s minimal NT version.

The remaining technical problems will be solved; so now is the time to introduce this technology and gain the first few steps of experience. Soft logic for control is a serious issue.

I believe the industrial software market is about to undergo a revolution similar to that when Microsoft launched Windows. Product choice has switched from a feature-by-feature comparison to comparing bundles of functionality – SCADA, PC-control, Internet connectivity, SQL databases, tracking and flexible batch management.

So, who owns plant floor data? The answer depends on the criteria you select for choosing your PIMS.

* The Author is with Pantek.

* See hard copy for survey tables