OB7 Flashcards
(14 cards)
What is the main function of a control system?
adjust a load to meet demand
limit actuator movement
maintain a variable at a setpoint
measure an error accurately
C
Basic components of a control system?
design conditions,
controller, actuator
sensor, controller, controlled device
setpoint, controller, wiring
thermostat, controller, transducer
B
Air conditioning and refrigeration systems are commonly controlled by ___ control
anticipatory
inverted
proportional
three position
C
Which of these control loops adjusts the setpoint automatically?
closed loop
open loop
reset system
self powered
C
The power to operate a control system may come from
changes in temp
feedback
fluid under pressure
the refrigerant
C
RTD responds to a change in temp by undergoing a change in its
electrical resistance
external shape
internal pressure
temperature resistance coefficient
A
Relative humidity is defined as the amount of moisture in the air
divided by the amount it can hold
minus the temp in C
multiplied by the air flow rate
plus the temp in F
A
In a pressure sensor that uses a Bourdon tube, changes in pressure is sensed by changes in the ___ of the tube
cross sectional shape
diameter
length
position of sealed end
D
Outside air damper should be ___ and the return air damper should be ___
closed, closed
closed, open
open, closed
open, open
B
Which of the following is an advantage of variable speed drives over older methods?
cost of electric service can be controlled
equipment can start up more smoothly
proportional control can be used
system can run during off hours
C
Unlike floating control, the proportional control is
continuous
discontinuous
instantaneous
slow
A
The air supply for a pneumatic control system requires which of the following?
algorithm
drier
evaporator
humidifier
B
A PE relay is used to control a device operated by
air pressure
electricity
positive electrostatic pressure
temp
B
Setting the gain of a controller determines how much change in the ___ effects the ___
controlled variable, controlled device
deadband
error
setpoint, proportional band
A
