Total Cost of Ownership

A Thin Client computer runs what looks like a full Windows NT 4.0 operating system on each Client installed in a factory. This is accomplished by having a powerful server running a version of Microsoft’s NT 4.0 designed for Thin Clients, NT Terminal Server 4.0. This version of Windows allows multiple users to log in and establish a full Windows session running on the server. Each user gets a dedicated share of memory, some slices of CPU time, and access to the server’s disks and applications.

What this means to the operator is that, for all practical purposes, he now has a computer running NT. But, here is where the Thin Client really starts to show its advantages over an Industrial PC. Not only does the hardware cost less, but the application is not actually running on the plant floor. Even though it appears to any user that he is running his control screens locally, they are actually running on the server back in the climate controlled IT department. This means:

Lower Total Cost of Ownership (TCO)

A Thin Client computer can lower TCO in the following key areas:

Keeping HMI and SCADA screens current

Most plants have multiple identical lines, and each line needs the same control screens. If they are using a dedicated PC at each line, then the screens are usually stored locally – loading large HMI screens from a common server takes too long. This means that design changes and updates must be distributed to each PC in the plant. For the Thin Client system, it is possible to run all Clients from the same screens. Changing them once can then change the entire plant. In fact, for most HMI systems, you can now update an entire plant WITHOUT SHUTTING THE SYSTEMS DOWN. Simply change and test the new screens on the Server console. Once they are finalized, put them on the directory where the Thin Clients are reading their production screens.

Keeping OS and application software current

Using a Thin Client system, any software upgrades applied to the server are also realized by all of the Clients. Think of the problems caused when Microsoft upgrades a tool, or a part of its operating system. You can still find plants today running Windows 3.1 – not because it is better, but because they don’t want to be burdened with the tremendous cost (and risk) of changing the operating system on all their PCs. The same is true of the actual HMI software. Although the user should purchase an HMI license for each Client that he will actually be running, every Client runs the same copy of the HMI or SCADA code. Simply upgrade to the latest version of software on the Server, make any changes needed to the screens (one time, on the server) and every Client in the factory is running the latest code with the updated screens.

Keeping hardware current

PC technology changes so fast that machines purchased just a few years ago are no longer able to run the latest software. With a Thin Client system, the Client hardware is very simple – it only needs to display the graphics screens and get the user input. The actual user processes all run on the NT Server. This means that by upgrading the Server, all of the Clients attached to it will seem to get a performance boost.

Keeping current (and timely) backups

You never know how important a backup is until you don’t have one. Most plant operators, however, don’t have the time or discipline to backup all (or even some) of their PC’s. If there is different software or data being used on each PC, it becomes even more difficult. Happily, backup problems are eliminated when using a Thin Client computer. The only machine with any software (the Server) is usually housed within the IT department, in a secure climate controlled environment. These people are used to doing backups, and will follow a schedule to assure the system is always current.

Being able to add a new PC (or replace one that is damaged)

Without an identical machine sitting around in a constantly updated state, it is a real chore to add a new PC for another line, or to replace a PC that has failed or been damaged. A new PC must be purchased (the same model as those running on the floor if it can be found), the correct version of the OS loaded (hopefully it is still available), the HMI software and drivers installed, etc. Adding a new Client to a Thin Client system (or replacing a damaged one) is simply a matter of plugging in the new Client and enabling it from the Server. There is no software to load, no screens to update.

Keeping foreign software off your systems (and keeping your data on)

PCs scattered throughout a manufacturing facility are a temptation to many operators to try to break in, or to load their own software (games, personal files) or, worse, virus software. In the modern manufacturing facility, most floor PCs are connected via a network to many other systems in the building. A person who can break into a system can create real problems for the entire factory. The Thin Client computer has no disk drives of any kind, so no new software can be loaded, and no sensitive data can be removed.

Removing the temptation to steal computers

A Thin Client computer is not a device that can be used without the Server. You cannot load any software on it. ACP’s Thin Clients require ACP’s software running on Microsoft’s NT Terminal Server. Outside of this network, the boxes are useless. Remove the temptation to pick up a good PC, and more of them will stay around. By the way, it is not just ‘criminals’ who walk off with PCs – most of the time it is another department who feels that they should get some use out of the PCs that you are keeping for spares.

These are just a few of the ways that a Thin Client system can reduce operating expenses over time. When added to the fact that Thin Client systems generally cost less than an equivalent number of industrial PCs (especially if installing more than about five), the case for a Thin Client system really looks very strong.