INFICON Composer Gas Concentration Controller - Manual (Page 184)

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Composer Operating Manual
8.5 Multiple Composers
Monitor software and Setup Tool both will support multiple Composers on one
computer. With either application, up to twelve units can be simultaneously
monitored provided that there is adequate number of communication ports
available on the computer. When the application is started, it will ask for a
unique .ini file name. It is advisable to make this name distinct and meaningful
for quick identification during future use. When one instance of the software is
running, another instance of it can be started with a new ini. file name.
Ordinarily, a PC has two serial communication ports. Add-on communication
cards may provide another extra pair. The drawback of this method is that each
communication port requires a unique IRQ. Finding more than four spare IRQs
in a PC is rare. If an IRQ is assigned to more than one COM port, Monitor
software or Setup Tool will not function properly. There are two distinct ways to
solve this problem.
One of these solutions is to use a 7 port USB Hub with USB to Serial 9 pin
converters. The USB to Serial 9 pin converters are connected to the RS-232C
port for each Composer. These converters are then fed to the 7 port USB Hub
which connects to the USB port on the PC. We have had success with this
solution. We purchased components from Entrega Technologies Inc.
(www.entrega.com). The USB to Serial 9 pin Converter is model number
Con-USB-S9. The 7 Port USB Hub for PCs is Hub-7U. There are no problems
with interrupt conflicts when using this solution. The Composer Monitor
Software is designed to work with up to 12 Composers.
One drawback to this method is that Windows NT does not support a USB and
therefore this solution is not viable if you are using Windows NT. Entrega states
in their web site that this will work for Windows 98 and Windows 95b. Windows
2000 versions supported USB and worked flawlessly. Entrega provides the
needed software with the components mentioned above.
The second solution we found is to use a multi-port serial card with Windows
drivers that uses only one IRQ (interrupt) and multiplexes it among all its ports.
We used an 8 port serial card from Circuit Specialists (www.web-tronics.com)
Model C-588 (pci card + octopus cable). This solution was tested on Windows
NT, Windows 98B, and Windows 95B systems and worked flawlessly. We also
find the connectors to be more rugged than the USB connectors. We believe
this is a very effective, inexpensive, and universal solution for connecting many
Composers to a single computer.