Test 2

Question 1

Reset Response =

Answer 1

TimeRepeats/minutePB Response

Question 2

Total change =

Answer 2

P.B. response + Reset response

Question 3

PB Definition

Answer 3

The amount by which the input signal value must change to move the output between 0 and 100%

Question 4

PID

Answer 4

• Also known as 3 mode control
• Like reset action, rate action is a time adjustment
• Derivative or rate action spikes the output of the controller in response to the rate of change of the error and stops when the rate of change of error is 0

Question 5

Rate Action

Answer 5

• Also known as derivative action
• Is used in large-capacity processes where there may be large lags or sudden changes/upsets in the process
• Used in temperature control applications and closed-loop composition control systems
• Provides a large, fast output response immediately upon a change in the process variable
• On fast processes, this would result in cycling therefore not necessary

Question 6

Derivative Mode Notes

Answer 6

• As the size of processing equipment increases, the mass and thermal inertia increases
• For very large processes, it is not enough to respond to an error that has already evolved because the inertia or momentum of these processes makes it difficult to stop or reverse a trend once it has evolved
• The purpose of derivative control is to predict process errors before they have evolved and take corrective action before the error occurs
  When the rate of error change is zero, the contribution of derivative action to the output is zero
• When the rate of error is rising, the contribution of derivative action is positive and correlates to the slope of the error curve
• The unit of derivative action is derivative time
• This is the length of time by which the derivative mode looks into the future
• If the derivative time is set for 10 seconds, it will generate corrective action equal to what the PB would have generated 10 seconds down the road
• The longer the derivative time setting, the further into the future the derivative mode predicts and the greater its contribution to controller outpu

Question 7

What do the three modes do differently?

Answer 7

• The proportional mode considers only the present state of the process error (responds to input change)
• The integral mode looks at past history (checking if the proportional response fixed the problem)
• The derivative mode anticipates the future state of the process and acts on that prediction

Question 8

How to write dual input alarms?

Answer 8

• (L)AH/H
• (L)AL/L

Question 9

Look at photo from missed class

Question 10

All controller tuning methods

Answer 10

• Trial and error
• Ultimate sensitivity method
• Step response method
• Micro-processor based tuning methods
• Auto/Semi-Auto Tune

Question 11

When is a controller properly tuned?

Answer 11

When the process returns to setpoint as fast as possible without overshoot