Connection issues between instrument modules and CDS

This may be the wrong forum as it's a Chromeleon connection issue but involves a Agilent 1100/1200 mixed module system.

When trying to connect one of our Agilent system to Chromeleon only the 1100 VWD will be detected if there is no instant pilot connected to the stack. As soon as an instant pilot is connected all modules get detected by Chromeleon. I am confident in our processes when getting systems connected as we have around 40 other Agilent systems set up without having the same issue and have had this system configured without issue before but I cannot locate any cause for our recent problem. I am also not aware of any significant changes being made to the Chromeleon instrument configuration or the physical stack that may have caused this issue to begin either.

I was wondering whether anyone else has experienced a similar issue.

  • Our CAN sockets automatically connect a terminating resistor to the bus when not in use, so that the two bus ends are electrically terminated. If the corresponding mechanics in the socket fail, this connection does not take place and the bus is not terminated properly, which can lead to issues. If the devices are very old (you mentioned "1100 VWD") and the sockets are worn out or dirty, this effect can occur. In worst case a new main board with a new CAN socket would be required.

    Furthermore, hot-plugging or hot-unplugging anything on the CAN bus is not recommended or supported. It may often work, but there's no guarantee it will. I even released an official service note on that subject.

  • Thanks for this.

    To make sure I'm understanding this correctly does this mean that the instant pilot is acting as the terminating end of the bus and that the socket that the instant pilot is connected to is the one that is failing when no instant pilot is connected? The connection sequence for the stack is as follows: network connection to VWD > CAN to column compartment > sampler > pump > instant pilot.

    In addition, would both CAN sockets on the module be affected if there is a fault? Could switching which socket is used to link to the next module in the stack overcome the issue.



  • It usually doesn't matter where the Instant Pilot gets connected. Any spare CAN socket would do. A damaged CAN socket can lead to all kinds of unexpected module behavior. Inspect your CAN sockets and try various connection scenarios. You might be able to work out which socket is not working correctly. Also try new CAN cables. However, with old 1100 series modules, which might be over 25 years old, it has been observed that the mechanics of the CAN socket can fail over time, especially when mechanical stress was put on the cables/sockets.

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