Process Control

Question 1

Give two examples of process variables

Answer 1

Speed
Position
Fluid pressure
Liquid level
Liquid flow
Temperature

Question 2

What is open loop?

Answer 2

Not automatic
No feedback
Requires operator

Question 3

What is closed loop?

Answer 3

Automatic
Feedback
No operator required

Question 4

What is a transducer?

Answer 4

Converts energy from one form to another

Question 5

What are three common uses of sensors? (What do they detect?)

Answer 5

Motion
Force
Temperature
Light
Position
Fluid pressure/flow

Question 6

List four types of linear motion sensors

Answer 6

Potentiometer
Variable inductor
Variable capacitor
Variable differential transformer

Question 7

What is a bonded wire strain gauge used to sense?

Answer 7

Force

Question 8

What device is used to send an electrical signal from a motor in order to interpret its speed?

Answer 8

Tach generator (most common)
Incremental encoder

Question 9

List three type of fluid pressure sensors

Answer 9

Bourdon tube
Bellows
Diaphram

Question 10

Which device consists of two dissimilar metals that when heated produce a small voltage?

Answer 10

Thermocouple

Question 11

Which feedback sensor would produce a small voltage when subjected to vibration?

Answer 11

Piezo electric crystal

Question 12

Which two signals does a comparator use to determine an error signal?

Answer 12

Set point
Feedback

Question 13

What is the function of an actuator?

Answer 13

Converts electrical energy to;
Motion
Heat
Light

Question 14

What does a solenoid do?

Answer 14

Provides linear motion

Question 15

What are three types of stepper motors?

Answer 15

Permanent magnet
Variable reluctance
Hybrid

Question 16

How can a stepper motor be reversed?

Answer 16

Reverse order of switching

Question 17

In regards to a stepper motor, what is a full step?

Answer 17

90°

Question 18

In regards to a stepper motor, what is a half step?

Answer 18

45°

Question 19

What are the three necessary parts of an optical encoder?

Answer 19

Light
Rotating disc
Light sensor

Question 20

What device could be used to minimize overshoot in regards to a baseboard heater?

Answer 20

Heat anticipator

Question 21

What is a sensor?

Answer 21

Measures and senses the process variable and provides feedback to the controller

Question 22

What type of sensor is this?

Answer 22

Linear motion potentiometer. Works with both AC and DC

Question 23

What type of sensor is this?

Answer 23

Linear motion variable inductor. Works with AC only

Question 24

How many degrees of travel can an angular motion potentiometer measure?

Answer 24

Up to 300°

Question 25

How many degrees of travel can an angular motion variable inductor measure?

Answer 25

More than 300°

Question 26

What is an actuator?

Answer 26

A device that converts an input signal into mechanical motion

Question 27

What is a stepper motor?

Answer 27

• Incremental, brushless DC motor
• Moves in discrete steps
• Each time its pulsed it will rotate by a certain angle

Question 28

What is a variable reluctance stepper motor?

Answer 28

• The rotor will align itself with the energized salient pole
• Will not hold position when de-energized

Question 29

What is the process variable?

Answer 29

A variable that needs to be controlled

Question 30

What is the set point?

Answer 30

The desired value of the process variable