Rockwell Automation 1772-L8_LW_LWP_LX_LXP,D17726.5.8 User Manual User Manual

Page 238

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EAF

Process Control Instructions

Chapter 16

16-27

Derivative Gain Constant (Word 06)
When using the Independent Gain Equation, this is the derivative gain
K

D

(sec). When using the Dependent Gains equation, this is the derivative

time constant T

D

(min).

Derivative Uses Error (Word 01, Bit 06)
You can select whether the derivative term in either PID equation acts on
changes in error or process variable. Consider selecting this feature if you
want to accelerate the response to online changes to the setpoint.

Reset (0)

For normal response to set point changes, derivative
acts on the change in PV

Set (1)

For a faster response to set point changes, set this bit to
act on the change in Error

Done Bit (Word 01, Bit 15)
This bit is set/reset by the EAF instruction when new values have
been calculated.

Reset (0)

New values not calculated

Set (1)

New values calculated

Enable Bit (Word 01, Bit 17)
This bit is set/reset by the EAF instruction to change the status of the
PID rung.

Reset (0)

Rung is not enabled

Set (1)

Rung is enabled

Error (E) (Word 16)
The algebraic difference between PV and SP.

Error Sign (Word 02, Bit 07)
This bit is set/reset by the EAF instruction to indicate the polarity of
the error.

Reset (0)

error is negative

Set (1)

error is positive

Equation (Word 01, Bit 00)
This bit is set/reset this bit to choose your PID equation.

Reset (0)

Independent Gain Equation

Set (1)

Dependent Gain Equation

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