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Most factories are controlled by PLCs or DSC systems. The information generated by the sensors, devices, and machines needs to be displayed for the operators on the floor in real-time, and needs to be available later for reports, records, and management. This gives a flow of data from the data generators to the data storage devices.
Most human-machine interface companies therefore recommend a 3-computer configuration when accessing and storing data. This configuration allows a different computer to be used for each of the three different logical tasks - collecting data, displaying data, and archiving data - as displayed in the following figure:
Data generated at the devices, sensors, machines, or PLCs is collected by the application program and sent to a database or historian for archiving. Operators can either pull run-time data from the PLCs or they can display historic data from the database. Each operator station is a full-blown PC, complete with hard drive, operating system, applications, and configuration.
In the Thin Client world, the network configuration is much the same. The main difference is that the many individual operator PCs, each with its own operating system, configuration, and management, are replaced with Thin Clients - "dumb terminals" that don't need special maintenance.
This article takes a brief look at how 3 of the leading packages (Wonderware, Intellution and CiTect) might be installed on a Thin Client system.
Important note: Terminal Server architecture requires that all user software be installed in the "install mode" so that the software will be available to multiple users. Do not allow the CDs to 'auto-run' the install program.
InTouch from Wonderware runs best with a 3-box system. A tagname server gathers data from the PLCs, DSC systems, and proprietary device networks. I/O drivers run on this computer to populate the tagnames with data. ACP Enabled Thin Clients act as the operator stations. These will pull the values for the tags from the tagname server, with data stored on a historian or SQL server. Wonderware will also run on a single box in a small network - in this case, the I/O servers are run on the console and provide the values to the Thin Client sessions.
The data collector gathers the I/O from the PLCs and DCS systems and acts as the tagname server. The I/O servers run here (or run as a service) and any proprietary cards should be installed in this machine or on the Thin Clients themselves. This PC is devoted to collecting the data and populating the tagname database.
The operator applications run on a terminal server and reference the tagname server to get the tag values. Although this is called a "three-box" system, many people will actually use two or more terminal servers to allow for failover.
Each terminal should login as a separate user and should run a separate copy of the application to keep retentive tags and historical data separate. Using Wonderware's NAD (Network Application Deployment) makes the maintenance and updating of multiple copies of a single application easy.
The data storage computer stores historical data for later usage. This is commonly a SQL server.
ACP Enabled Thin Clients require an IP address to connect to the terminal server. Once the terminal logs into the terminal server and starts a session, it doesn't use the IP address but instead uses a dynamic session ID to differentiate among the terminal sessions. This means that SuiteLink can be used to share data between sessions while NetDDE cannot. However this requires a static IP for the Thin Client, which can be reserved in DHCP or assigned as static during the terminal power up. Access names can point directly to a client by having an access name with "ViewIPAddress" for the application name
The WWLogger has a "Client IP Address" connection under Connect on the Wonderware Logger menu bar. This allows the WWLogger to view the sessions separately, either locally or remotely. Selecting the Client IP Address will allow one to choose which session to display.
Wonderware has added three helpful functions for Thin Client computing. These new client scripts include:
Using ACP Enabled Thin Clients to run Wonderware's InTouch improves the availability of the application because of ACP's quick and easy terminal replacement and ACP's terminal server failover.
Intellution iFix can be configured to work as well in a "3-Box" Thin Client environment as it does in a traditional PC environment. The first box is the SCADA node computer that gathers data from the PLCs, DSC systems, and proprietary device networks. I/O drivers run on this computer to populate the application variables with data. ACP Enabled Thin Clients can act as the View nodes to display the data to the operators and run on the second box, the Terminal Server. The data are stored on the third box, a data historian or SQL server. Dual terminal servers can also be setup to provide redundancy and failover to allow the operator screens to keep running with current data if a terminal server fails.
iFix can detect when it is installed on a terminal server, and will allow a single client to connect as a demo, but it will deny access to the other terminals unless it has the proper licensing key. Intellution uses a hardware key that attaches to a parallel port on the terminal server. If the terminals do not recognize the key, rebooting the server and the terminals will often reinitialize it. The key should be left on the machine, and not "hot swapped".
Each terminal will require a user account, and will normally be used in a factory as a view node to display the iFix screens. It is recommended that a naming scheme be established, using a descriptive name, and that this name be assigned to the Thin Client hardware (node name), the user account, and the SCU file. Boiler01, Mixing_Tank_34_East, User1, Station 2, and Terminal 3 are examples of descriptive names for the terminal, node, and user profile. Additionally, it is recommended that these terminals be configured to automatically logon and launch the iFix program.
All of the Thin Clients will need an IP address to allow them to connect to the network. One cannot use this IP address to differentiate between Thin Clients, though, because the sessions that are shown on the terminal are actually running on the server and will return the server's IP address.
Intellution handles this issue by using the LAN redundancy feature. Each terminal will need two IP addresses. One is assigned to the hardware to allow it to attach to the network. The second IP address is bound to the user profile in the SCU file. It is easiest to have the IP addresses in parallel series, like 101 & 201 and 102 & 202, or 30 & 31 and 32 & 33.
Each user also needs a directory in the "Dynamics" directory. Open C:\Dynamics and create a new folder in it for each new user (Boiler01, Tank_34_East, or Station 1, Station 2, and Station 3). Copy the C:\Dynamics\Local folder into each new folder to become the new user's Local folder. Additionally you will find that a System Configuration Utility or SCU file needs to be configured for each user to pass the system configuration to the session.
The SCADA Configuration allows the view node to point to the SCADA server and to attach to I/O drivers.
The iFix program is not started with the Start > Programs > iFix > Startup on terminal servers. This would launch all the instances with a single SCU. Instead, Intellution uses the Launch program that can be configured individually to launch unique SCU files.
ThinManager can launch iFix as an initial program so that iFix will launch automatically each time the terminal is booted. To do this, type the command line from the Target field of the Launch shortcut into the Initial Program field on the ICA session tab of ThinManager.
CiTect industrial automation software from Ci Technologies works effectively with Thin Clients running ACP ThinManager software. CiTect uses an I/O Server to gather the data and populate data tags with values. The Thin Clients act as the Display Nodes, and the data can be stored in a historian or SQL server.
If using Windows 2000 Server as the Terminal Server, be aware that Windows 2000 Security prevents unauthorized users from writing to the registry or the windows directory. Since CiTect uses these features, selecting Windows 2000 permissions will prevent a CiTect user from connecting to an I/O server, so if Windows 2000 permissions are selected each user must be made an administrator or a power user to allow connection. A simpler method is to select and use the legacy Windows 4.0 Terminal Server permissions.
CiTect should recognize hardware keys (dongles) if the keys are placed on any server. If the Thin Clients do not see a key, the server may be using Windows 2000 Permissions and the user is not a power user or an administrator.
CiTect runs best in a "three-box" configuration using Terminal Server. This layout has one computer configured as the I/O server, with a Terminal Server computer configured to provide the display clients. The third box is for data storage.
To configure the ACP Enabled Thin Clients with the least amount of work, do this:
At this point the terminals can be turned back on and the sessions started by logging in the user.
Much more information on these and other installations can be found scattered throughout the ACP Technical support pages.
For more information on ACP Industrial Thin Client computers, please visit our web site at http://www.thinmanager.com
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