Control Fundamentals ppt

Question 1

________ decides whether to make an adjustment

Answer 1

controller

Question 2

An OPEN loop control loop has ___ feedback

Answer 2

NO

Question 3

On open loop control loops, no feedback information is returned to the ________, changes must be made manually

Answer 3

controller

Question 4

A CLOSED loop control loop has _______

Answer 4

feedback

Question 5

On closed loop control loops, a ______ provides feedback to a controller which processes information and compares control point with set point

Answer 5

sensor

Question 6

High voltage:

Low voltage:

Extra low voltage:

Answer 6

High voltage: 751+

Low voltage: 31v to 751v

Extra low voltage: 0 to 30v

Question 7

Pneumatic controllers use ___ instead of ________, typically ___psig

Answer 7

air, electricity, 20psig

Question 8

Variable refers to _____ temp

Answer 8

space

Question 9

Medium refers to ___ you are trying to control

Answer 9

air

Question 10

Overshoot and undershoot conditions are caused by ____ in the system

Answer 10

lag

Question 11

Control agent is the mid in which the manipulated variable exists. In a steam heating system the control agent is the ______

Answer 11

steam

Question 12

A device used to position dampers and control valves are

Answer 12

actuators

Question 13

Series 90 electric actuators are being replaced by ____ _____ actuators

Answer 13

direct drive

Question 14

Typical two position controls undershoot and overshoot to prevent system from short cycling causing damage to equipment. What is the downside?

Answer 14

lack of temperature control for comfort

Question 15

Difference between the set point and and control point is known as? Also known as?

Answer 15

offset, deviation

Question 16

The separation between heating and cooling is known as?

Answer 16

dead band

Question 17

The series 90 low-voltage control circuit provides _________ control and can be applied to motorized valves and dampers

Answer 17

modulating

Question 18

In modulating control, an actuator moves damper proportional to the sensed change in the controlled variable.

A 10 degree throttling range moves the actuator _____ of the total travel for each degree change in temp

Answer 18

1/10

Question 19

Proportional control helps keep the room temperature _____ to set point

Answer 19

closer

Question 20

Proportional ____ is the change in controlled variable required to change the controller output from gully open to fully closed

Answer 20

band

Question 21

In _______ _______ control, reset of the control point is automatic

Answer 21

proportional integral

Question 22

Proportional _______ control changes the final control element position to accommodate load changes while keeping the control point at or very near the set point

Answer 22

integral

Question 23

1. Proportional integral derivative control (PID) adds a derivative function that ______ any change and is ________ to the rate of change
2. The more quickly the control point changes, the more corrective action the ____ system provides
3. PID control, eliminates _____, faster

Answer 23

1. opposes, proportional
2. PID
3. offset

Question 24

What provides powers to the temperature sensor (RTD’s)

Answer 24

the controller

Question 25

RtD exhibits large _______ changes, linear changes, or both over wide temperature ranges

Answer 25

resistance

Question 26

A ________ is a solid state discrete sensor with a _______ temperature coefficient. As temp increases the resistance of the sensor decreases

Answer 26

thermistor, negative

Question 27

Temp sensors: 1. temperature sensors are created by welding together two ________ metals 2. When this junction is heated, a ______ is generated 3. amount of _______ is directly proportional to the ____

Answer 27

1. dissimilar metals 2. voltage 3. voltage, temp

Question 28

Thermocouples generate enough voltage to hold the _______ valve open

Answer 28

pilot

Question 29

Only the ___ of the thermocouple should be heated

Answer 29

end

Question 30

Thermopiles are different from thermocouples in that they generate a ______ voltage that is enough to run the actual gas valve

Answer 30

larger

Question 31

As the temperature goes up on a thermocouple the _______ goes up

Answer 31

voltage

Question 32

Humidity Sensors 1. Humidity sensors use a __________ material that will expand or contract in response to changes in humidity 2. Types of Humidity sensors; name 3

Answer 32

1. hygroscopic | 2. wood, hair, gold leaf, membrane

Question 33

Define deadband

Answer 33

range between heating and cooling in which neither will turn on

Question 34

describe proportional band?

Answer 34

change in controlled variable required to change controller output from fully open to fully closed

Question 35

List different control loops and describe each one?

Answer 35

open - no feedback closed- feedback

Question 36

List three different mechanical control components?

Answer 36

actuator, valves, dampers

Question 37

Name two different drive types of actuators?

Answer 37

electric, pneumatic