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S7 1200 Pid Tuning in Auto mode

Created by: Vineeth V at: 4/3/2013 1:37 PM (4 Replies)

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4/3/2013 1:37 PM	Rate (0)
Vineeth V Posts: 4 Rating: (0)	Dear all, sorry if im repeating the same query.Here I need to have a PID Controller for temperature management. Here the application is like this PID should have two modes i.e, auto & manual. If we select the Manual mode we have to manually stroke the valve by putting the desired value to open. If we put in auto mode the PID should tune (with the aid of P, I & D parmeter entry through HMI) to the set point. PID Configuration: Here I have taken PID Compact and my setpoint happens to be from HMI where the operator enters the desired temperature & my process variable is the scaled value from a 4 wire RTD. My output is obviously a control valve with 4-20mA signal acceptance. Now the manual part is working very well. If I put in auto mode after transition from manual mode, I’m receiving sampling time error & pid goes to inactive state.Also I want to have the same output if I change the mode A to M or vice versa. In this regard can some one suggest me how to configure & commission.
Vineeth V Posts: 4 Rating: (0)
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4/3/2013 4:23 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 1/8/2025 Posts: 6858 Rating: (1366)	Vineeth V Dear all, sorry if im repeating the same query.Here I need to have a PID Controller for temperature management. Here the application is like this PID should have two modes i.e, auto & manual. If we select the Manual mode we have to manually stroke the valve by putting the desired value to open. If we put in auto mode the PID should tune (with the aid of P, I & D parmeter entry through HMI) to the set point. PID Configuration: Here I have taken PID Compact and my setpoint happens to be from HMI where the operator enters the desired temperature & my process variable is the scaled value from a 4 wire RTD. My output is obviously a control valve with 4-20mA signal acceptance. Now the manual part is working very well. If I put in auto mode after transition from manual mode, I’m receiving sampling time error & pid goes to inactive state.Also I want to have the same output if I change the mode A to M or vice versa. In this regard can some one suggest me how to configure & commission. Hello, 1-About the question on sampling time, where did you called the PID controller, in cyclic interrupts? 2-For bumpless switchover from automatic to manual, in each cycle of PID execution, you should write output of PID controller in autot mode to manual value of PID.I have not tested this for S71200,but I am sure it give you the result. Best regards Hamid Hosseini
	Demo Channel on Youtube
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4/3/2013 4:48 PM	Rate (0)
Vineeth V Posts: 4 Rating: (0)	PID Compact loop has been called in OB200 (Cyclic Interrupt) Also i have put a condition to enable the pid loop, because my application demands
Vineeth V Posts: 4 Rating: (0)
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4/3/2013 5:01 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 1/8/2025 Posts: 6858 Rating: (1366)	Vineeth V PID Compact loop has been called in OB200 (Cyclic Interrupt) Also i have put a condition to enable the pid loop, because my application demands Hello, As a test, just always call the function and only use condition output transfer. I mean, when your process change from one sequence to another,PID is called always but the substitute value is transferred to output. This can be done by binary switches and move blocks. Just be careful of bumpless switchover in mode change. Try and update. PID Compact checks the sampling time by measuring time between 2 successive calls and that may cause problem in your case.Consult online help of STEP7 Basic for more information and criteria for error generation. Best regards Hamid Hosseini
	Last edited by: hdhosseini at: 4/3/2013 7:01 PM Demo Channel on Youtube
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4/4/2013 11:29 AM	Rate (0)
Vineeth V Posts: 4 Rating: (0)	Dear Sir, Im enclosing the screenshots of my pid tuning. Here i observe new error in the PID block, i.e Error while starting pretuning (Error No. 0008) & Pretuning may not be carried out in automatic mode or during fine tuning (Error No. 0020). Also in the screenshot, the part where the commissioning window is selected from the PID block is indicating a warning symbol. I do remember, sometime back when i did something, the pretuning part was done & this symbol which is appearing in the commissioning window selection part on the PID block got cleared & the status bar was showing fine tuning is not completed. Can someone please explain what is the difference between pretuning & finetuning, also how to clear the warning signal in the commissioning window selection point in the PID Block. Attachment Print Screens of my PID loop.pdf (1644 Downloads)
Vineeth V Posts: 4 Rating: (0)
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