8.9.2 PID equation structures
Configure the STRUCTURE parameter to select the PID equation structure. You
can select one of the following choices:
• PI Action on Error, D Action on PV
• PID Action on Error
• I Action on Error, PD Action on PV
Set RESET to zero to configure the PID block to perform integral only control
regardless of the STRUCTURE parameter selection. When RESET equals zero, the
equation reduces to an integrator equation with a gain value applied to the error.
Figure 8-16: PID Equation Structure
Where:
GAIN Proportional gain value
e Error
s A place operator
8.9.3 Reverse and direct action
To configure the block output action, enable the Direct Acting control option. This
option defines the relationship between a change in PV and a corresponding
change in output. With Direct Acting enabled (True), an increase in PV results in an
increase in the output.
You can set control options in Manual or Out of Service mode only.
Note
Track Enable, Track in Manual, SP-PV Track in Man, SP-PV Track in LO or IMAN,
Use PV for BKCAL_OUT, and Direct Acting are the only control options supported
by the PID function block. Unsupported options are not grayed out; they appear
on the screen in the same manner as supported options.
8.9.4
Reset limiting
The PID function block provides a modified version of feedback reset limiting that
prevents windup when output or input limits are encountered and provides the
proper behavior in selector applications.
8.9.5
Block errors
Table 8-26 lists conditions reported in the BLOCK_ERR parameter.
F
OUNDATION
™
Fieldbus Manual
December 2022 00809-0500-4880
180 Emerson.com/Rosemount
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