8/19/2019 2:25 AM | |
Joined: 9/9/2015 Last visit: 10/8/2024 Posts: 727 Rating: (278) |
Dear mesnowball, In my viewpoint, SP_LiOp should always be set to zero. When SP_LiOp set to zero, the faceplate will have an option for setting to internal setpoint (Operator) or external setpoint (Program). Then, by default, there is an operator authorization on this button, which is level 2. Those operators/user with higher process controlling authorization can use this button to override from external setpoint to internal setpoint. This is extremely useful during commissioning. Let me illustrate the situation. There is a Pump control logic. During pump start-up, you give a pulse "1" to SP_LiOp and SP_ExtLi to set the pump to the external setpoint, 50%. After running for 30seconds, the program continues to set the external setpoint to higher setpoint. However, the setpoint is incorrect, the operator would like to override to a better setpoint. Then, the supervisor can log in their account, open the pump faceplate, change from external setpoint to internal setpoint. Bumpless tracking will transfer the external setpoint, let's say 80% to Internal setpoint. So now internal setpoint is 80%, the supervisor can set the setpoint to 75% or 70%. This kinds of situation happened quite frequently during commissioning. If you do not need the function, just set the SP_LiOp to 1 to disable the function will do. Hope this is clear for you now. |
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