INST 1211 Controllers Flashcards
Where would you put a resistor on a controller?
Analog Input side of the controller
Describe a reverse acting controller
Input 4 mA = 100 kPa OutputInput 20 mA = 20 kPa Output
On/Off controller responds to _________
Error
Differential Gap Controller responds to ___________
Error, direction of error
What are the pros of a diff. gap controller
Relatively simple, reduces wear of FCE compared to on/off controller, stable
What are the cons of a diff. gap controller
Not good for continuous control around SP, valve strokes full range causing wear
Proportional controller responds to ________
Existence of error, direction of error, and amount of error
What are the pros of using a proportional controller?
Relatively simple and easy to use, good stability, rapid response, and relatively stable
What are the cons of using a proportional controller?
Proportional only therefore has offset, low gain doesn’t reach SP, high gain overshoots it, takes a while to reach steady state.
Proportional integral controller responds to ____________
Existence of error, direction of error, amount of error and duration of error
What are the pros to using a PI controller?
Eliminates offset that exists in the P-only controller
What are the cons to using a PI controller?
Overshoot, Ki value set too high will look for error too frequently causing instability, slower settling time
What does a PD controller respond to?
Existence, direction, amount, and the rate of change of error
What are the pros of a PD controller?
Stable, minimal overshoot from the integral function, rapid response, predicts the change in PV
What are the cons of a PD controller?
Slow settling time, derivative kick
