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Troubleshooting Communications to PLCs and Other Controllers

Communication Examples

Communication Examples

When configuring communications between the InduSoft Web Studio SCADA software and hardware, it’s important to be able to troubleshoot the common problems that occur. This will save time in implementation, and help reduce downtime in the process. Generally, there are three main categories in which communication occurs : Serial (includes RS-232 and RS-485), Ethernet and TCP/IP based connections (includes radio modems, dialup, cell and satellite), and Proprietary, which often require a 3rd party interface (includes Modbus Plus, DeviceNet, PROFIBUS, CAN, CANopen and many others).

Troubleshooting Serial Connections

  • Is the cable wired correctly? This is one of the most common problems.
  • Is the cable too long? Is it bundled with high voltage cables? The RS-232 recommended maximum length is 50 feet under most conditions. You may need to shorten the cable or physically separate the communication cables from the power cables
  • Long RS-485 cables should be terminated; check the manufacturer’s documentation.
  • Use the WriteStatus and ReadStatus fields in the scada software driver worksheets to help isolate the issue. Most drivers will have a value of 0 for good communications, and a non-zero represents some error. The driver manual will show you what the error code means.
  • Try using the InduSoft pre-built communication example projects.

Troubleshooting Ethernet Connections

  • Most HMI or SCADA software applications will have hardware that uses a static IP address, and will not get IP addresses via DHCP.
  • Confirm that your Subnet mask will allow connection between the devices that will be communicating.
  • Can you “ping” one device from the other?
  • Use the WriteStatus and ReadStatus fields in the driver worksheets to help isolate the issue. Most drivers will have a value of 0 for good communications, and a non-zero represents some error. The driver manual will show you what the error code means.
  • Try using the InduSoft pre-built communication example projects.

Troubleshooting Proprietary Connections

  • How is the hardware connected to the computer? Is it plugged in?
  • Are the drivers installed?
  • Are drivers available for the operating system you are using?
  • Is the hardware supported by one of the 240 InduSoft drivers? If not is there an OPC Server available?
  • Does the PLC or controller need to be configured to communicate using that port?
  • Are the cables created correctly? Are they terminated correctly? Check the manufacturer’s documentation.
  • Use the WriteStatus and ReadStatus fields in the driver worksheets to help isolate the issue. Most drivers will have a value of 0 for good communications, and a non-zero represents some error. The driver manual will show you what the error code means.

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