What is a SCADA system
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Is the PLC or DCS sequential control logic the same as the operation instructions?
No, sequential control generally involves the automatic execution of predefined program steps; at each stage, the next step is carried out once the requirements are met, until the entire sequential process is completed and a new cycle begins.
Sequential control, also known as order control, is automatic control that takes place according to time intervals or event triggers. The operation instructions are a description of the sequence of process operations. The former is a control program, and the latter is a requirement file.
Personal understanding: Sequential control means controlling things in order; the next step is only taken when all conditions for that step are met. If the conditions are not satisfied, human intervention may be required to meet them, and there is no time constraint. The PLC is programmed for control, with each step carried out in sequence.