Tuning Tips; Output Response; Derivative - Emerson Fisher FIELDVUE DPC2K Instruction Manual

DPC2K Digital Process Controller
April 2024

Tuning Tips

Note
When performing tuning procedures, keep in mind that the initial settings are guidelines. They will vary depending on the actual
process being controlled.

Output Response

The response of the controlled parameter to a set point or load disturbance change may be classified in the following
manner:
D Over-damped response – Controlled parameter is gradually restored without overshooting the set point value. In
most cases, an over-damped response provides best response for varying operating conditions that impact process
gain and response time.
D Critically damped response – Controlled parameter is restored in minimum time without overshooting the set point
value. While minimizing response time, unstable control may be observed with changing operating conditions that
impact process gain or response time.
D Under damped response – Controlled parameter overshoots the set point but eventually settles at the set point
value. May minimize time to get back to set point but at the expense of stability and overshoot to set point and load
disturbances.

Derivative

Note
The Derivative should be tuned only when necessary.
Most industrial control loops can be handled with P-I control alone. Derivative action should only be applied to loops
when all of these conditions are true:
D There is little or no noise
D Fast-responding control is critical
D P-I alone is not good enough
D There is some (small) filtering of the PV (process value or process parameter)
10
Instruction Manual
D104786X012