When working with the devices that support the Modbus RTU protocol, users need software and special hardware. This concerns three stages: development, setup and testing. The RS-485/USB converter is one of the most important tools that you should have. This is one of the simplest solutions. The Ethernet/RS-485 is a more complex option.
When developing electrical devices that support this protocol, the Slave function is usually implemented. This is because these devices are most often slaves. They include I/O modules, sensors, relays, etc. In automatic control systems, the Master function is assigned to the controller. It is usually implemented as the Modbus OPC Server.
Modbus Terminal is especially useful when testing devices. Using this tool, you can perform three actions at once:
• create a request,
• send it,
• evaluate the answer.
During the test, users may experience difficulties. For example, there is often a situation when the device under test receives a request and responds to it, but this is not indicated in the program. A serial port sniffer will help solve this problem.
Testing is aimed not only at obtaining an assessment of the correct functioning of devices. Long-term testing also allows you to determine the operating time to failure. This requires logging and automatic polling.
For testing to be effective, a log analysis and visualization system is needed. It allows you to determine the exact number of requests that were not answered. In addition, failure detection is among its functions. This system will help you conduct effective testing and receive a detailed report.
I use the OPC Server as part of a dispatch system for an individual heat point in a business center. The program works with controllers via RS-232 ports. This solution has a lot of advantages. Remote parameter monitoring is available. The created system provides convenient...
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