Proportional Control Flashcards
how to calculate gain?
Proportional Band (PB)
is Proportional Band (PB) stated in units or %?
%
A Proportional (“P-only”) Controller has an output that is proportional to the __________________.
the sign and magnitude of the error.
controller output formula for p-only?
mc = Kc e + mo
Where: mc = Controller Output
Kc = Controller Gain
e = Error = b – r (for direct acting controller)
e = Error = r – b (for reverse acting controller)
mo = Bias
Disadvantages of P-only control are:
- P-only requires an error to operate; minimum error remains as “Offset”
- Due to offset, tight control is not possible
- Increasing Gain reduces offset, but may lead to instability
what is offset/droop
A constant and steady state of deviation of the measured variable from the setpoint
A P-only controller is said to be “aligned” when?
Measured variable (b) = 50%,
Set point (r) = 50%, Bias (mo) = 50%, and Output (m) = 50%.
what are the four following adjustments for P-only controllers?
- Set point
- Gain
- Direct/Reverse action switch
- Auto/Manual Switch
The controller behaves a a P-only controller when the controller is in _______.
Auto
In Manual, the set point knob merely moves the control valve from?
0 to 100%
P-only is acceptable when the process is dynamically slow or fast?
Slow (low process gain)
true or false? P-only control may be acceptable if small load changes are not anticipated?
false
P-only control may be acceptable if load freuqents are fruquent or infrequent?
infrequent
true or false, P-only control may be acceptable if offset error is not acceptable?
false
