Control loop does not activate when it should

[Jim Manley]

I’m using a PIDE to implement a simple temperature control on a fermenter.  There is a temperature probe in the fermenter that senses the current temperature (process variable).  The set point is entered via an HMI. The output of the PIDE is used to control the position of a valve (control variable).

The problem I’ve encountered is that when the system is in program mode, the SP is set to 75° the PIDE will not start controlling the valve when the temperature gets above the set point.  If I switch the system to manual mode then back to auto, it starts working properly.

This only seems to occur when the set point is 75°.

Any ideas on what’s going on?

Thanks,

Jim

[Jim Manley]

So I guess this one was too hard for the group. 🙂

I’ll keep poking at it.  If I sort it out, I’ll post the answer here.

[Fred Graham]

Hi Jim, yes it’s been awfully quiet in here…hmmm…unusually quiet for that matter! I will look into any possible delivery issues on my end. In the meantime, yes please keep us posted on your progress and any potential solutions or problems you encounter.

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