How can you verify PLC program correctness and completeness?

1 Review the specification

The first step to verify your PLC program is to review the specification or the requirements document that defines the expected functionality, performance, and safety of the system. You should check if your PLC program matches the specification in terms of inputs, outputs, logic, timing, alarms, interlocks, and other features. You should also identify any gaps, ambiguities, or inconsistencies in the specification and clarify them with the stakeholders or the end users.

2 Use simulation and testing software

The second step to verify your PLC program is to use simulation and testing software that can emulate the PLC hardware and the system environment. Simulation and testing software can help you debug your PLC program, detect errors, and optimize your code. You can run various scenarios, inputs, and outputs, and observe the behavior and response of your PLC program. You can also use simulation and testing software to perform functional testing, stress testing, regression testing, and integration testing of your PLC program.

3 Apply formal methods and techniques

The third step to verify your PLC program is to apply formal methods and techniques that can mathematically prove the correctness and completeness of your PLC program. Formal methods and techniques can help you verify the properties, specifications, and assumptions of your PLC program, and identify any logical flaws, contradictions, or violations. Some examples of formal methods and techniques are model checking, static analysis, formal verification, and formal specification.

4 Perform code reviews and inspections

The fourth step to verify your PLC program is to perform code reviews and inspections with other programmers, engineers, or experts. Code reviews and inspections can help you improve the quality, readability, and maintainability of your PLC program. You can also get feedback, suggestions, and best practices from your peers and mentors. You can use code review and inspection tools, checklists, standards, and guidelines to facilitate the process.

5 Conduct field testing and commissioning

The fifth step to verify your PLC program is to conduct field testing and commissioning of the system with the actual PLC hardware and the physical environment. Field testing and commissioning can help you validate the functionality, performance, and safety of the system in real-world conditions. You can also check the compatibility, reliability, and robustness of the system with other components, devices, and networks. You can use field testing and commissioning tools, instruments, procedures, and protocols to ensure the proper operation of the system.

6 Document and update the results

The sixth step to verify your PLC program is to document and update the results of your verification process. You should record the methods, tools, tests, and outcomes of your verification process, and report any issues, errors, or improvements that you have found or made. You should also update your PLC program, specification, and documentation accordingly, and keep track of the changes and revisions. Documentation and updating can help you maintain the accuracy, consistency, and traceability of your PLC program and system.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?