adccommunitymod (AutomationDirect) asked a question.
Created Date: December 16,2011
Created By: IBS Guy
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Hi, I have been having trouble getting a 4848LR control to tune properly. Specifically I am using heating mode and it seems that any time you change the integration time the control will not wind up until the process variable crosses the setpoint for the first time. I couldn't pin it down in the field but back in the office on a simulator it does this every time. Is this a quirk, an incorrect setup or just an incorrect observation and is there a remedy? Once the control is attached to the process it will not be possible to accommodate this without putting the control in manual and driving the PV up every time you change the integration time. Thanks,
Created Date: December 16,2011
Created by: IBS Guy
It gets more challenging...
Once the controller is operating properly, if there is a power cycle it reverts back to its problematic ways. That is it functions as a proportional control only with no reset.
Created Date: December 16,2011
Created by: bcarlton
I have read documentation listing this as a setting. Most PID controls I have seen, from a power off start, move the system to the setpoint then have a slight overshoot before settling. This feature would prevent the windup of the integral factor during this initial phase. But I would think this would be a selectable function.
Created Date: December 17,2011
Created by: IBS Guy
Do you see that in regard to SOLO controllers or just in general? Right now I'm getting by by lowering the proportional band enough to let the proportional component carry the output to 100% after a power cycle but the control is not so good after the process is up to setpoint. (Ya think?)
I think it's a bug. I 've submitted this to tech support but haven't heard back yet. I'll post any information they can give me.
Created Date: December 27,2011
Created by: IBS Guy
Issue Resolved
As promised here is the last word on this from AD tech support.
From an e-mail sent to me:
I have some info for you. I could reproduce what you are seeing, but there is a parameter that if the Solo performs Auto-Tuning, it adjust this parameter to greatly reduce/remove the issue you are seeing. The "Integral Offset " (P1-8) specifically mentions creating an offset on start up to increase the output faster than just Integral will.
I tried levels of 25% up to 80%, and it drives the Output close to 100 % immediately on start-up. And if you change this value, it takes immediate effect, rather than waiting for the PV to cross the SV. Since the vast majority of users use Auto-Tuning, the Solo is most likely driving this value up automatically, and it takes care of the lag that is visible if set to 0 and expecting the Integral to drive the output to 100%.
The manufacturer wouldn't consider what you are seeing a bug, they have already put in a parameter to deal with the condition... I believe this is the parameter you need to adjust to take care of the issue.
Created Date: December 16,2011
Created by: IBS Guy
Hi, I have been having trouble getting a 4848LR control to tune properly. Specifically I am using heating mode and it seems that any time you change the integration time the control will not wind up until the process variable crosses the setpoint for the first time. I couldn't pin it down in the field but back in the office on a simulator it does this every time. Is this a quirk, an incorrect setup or just an incorrect observation and is there a remedy? Once the control is attached to the process it will not be possible to accommodate this without putting the control in manual and driving the PV up every time you change the integration time.
Thanks,