on-off controllers

Question 1

on-off controllers are also known as?

Answer 1

“two position” controller.

Question 2

true or false: the controller signal to the final control element is inbetween 100% or 0%,
that is a control valve is never fully open and fully closed

Answer 2

false

Question 3

The five requirements for a sucessful on/off control are?

Answer 3

-Economics of the process do not require sophisticated control.

-Precise set-point control is not necessary.

-Processes, such as heat and level, which are generally slow in response time work best.

-Manipulated variable energy or volume inflow to the process is relatively small compared to the capacity of the process.

-The fully-open/closed operation of the final control element introduces incrementally small changes to the process and is incapable of oscillating the process into instability.

Question 4

is Compressed air supply to a storage tank an example of an on-off control?

Answer 4

yeah

Question 5

why is dead-band necessary for off-on control?

Answer 5

Air compressors would use on-off control. pure off-control without dead band can burn out the motor because it is constantly turning off and on to match the setpoint. Dead band would create a delay in when the motor would switch on and off. This eases the stress that would be put on the motor

Question 6

Does this on/off control have dead band?

Answer 6

yes

Question 7

what is the Output controller forumla?

Answer 7

mc = Kc ∙ e
mc = Controller Output (% or EU)
Kc = Controller Gain (unitless and infinite)
e = error (% or EU)

Question 8

can on/off control be used in fast processes?

Answer 8

no

Question 9

true or false? on/off control is Not very accurate, nor repeatable control

Answer 9

true

Question 10

true or false? in on/off control Energy or material flow must be small in relationship to the energy/material already in the system. heat supplied by furnace in house is small compared to
heat already in the house.

Answer 10

true