Chapter 13 - Controls & Sensors

Question 1

AC motor starters connect an AC motor to and disconnect it from an electrical power source.

Answer 1

True

Question 2

AC starters employ two basic components, a contactor and an overload

Answer 2

True

Question 3

Contactors are non-magnetically operated.

Answer 3

False

Question 4

Manual starters are the most widely used in the USA for motors over 2 HP

Answer 4

False

Question 5

Starters designed to meet NEMA and IEC standards differ in three important characteristics-ratings, life, and overload types.

Answer 5

True

Question 6

Three-phase motors are reversed by interchanging any two of three power leads to the motor.

Answer 6

True

Question 7

Solid-state starters use an intelligent regulator module similar to those used in adjustable-speed DC drives.

Answer 7

True

Question 8

Solid-state starters can use current-limit ramping or tachometer feedback to produce different acceleration and deceleration characteristics.

Answer 8

True

Question 9

Solid-state starters have an “energy-saver” function.

Answer 9

True

Question 10

Class H fuses are not renewable.

Answer 10

False

Question 11

Motor controllers often contain relays, push buttons, and manually operated switches.

Answer 11

True

Question 12

The size of a PLC memory is defined in so many “K”

Answer 12

True

Question 13

PLCs are unable to work with any form of local are network (LAN) communication

Answer 13

False

Question 14

All personal computers come with an I/O structure.

Answer 14

False

Question 15

Sensors are devices that respond to a physical stimulus such as heat, light, pressure and flow.

Answer 15

True

Question 16

Tachometer-generators are used to measure speed of light.

Answer 16

False

Question 17

Encoders are used for both position and speed feedback.

Answer 17

True

Question 18

Message displays provide information in response to various control events.

Answer 18

True

Question 19

Limit switches translate motion into switch actuation.

Answer 19

True

Question 20

Bubble sensors are popular for water and waste treatment applications.

Answer 20

True

Question 21

Piezoresistive sensors are based on the principle that resistance of the same element changes with humidity.

Answer 21

False

Question 22

LVDT is the abbreviation for low voltage digital transformer.

Answer 22

False

Question 23

Photoelectric sensors produce a voltage when exposed to light.

Answer 23

True

Question 24

Vision systems integrate integrate industrial computers with video cameras that provide data about the light it receives.

Answer 24

True

Question 25

PLCs and computers have

Answer 25

user programmability, Internal bus systems, Inputs and outputs, recallable memory (all of the above)

Question 26

Optical encoders include

Answer 26

Incremental and Absolute (A and C above)

Question 27

Control devices that can leak a small amount of current when turned off include

Answer 27

Solid-state switches

Question 28

Relay contacts typically are rated for

Answer 28

10A

Question 29

PLC’s are classified by the ability to

Answer 29

Add and subtract, multiply and divide, compare values and Diagnose (all of the above)

Question 30

Character displays can use

Answer 30

Light-emitting diodes (LEDs), Light-counting diodes (LCDs) Electrolyte diodes (ELDs) (all of the above)

Question 31

Incremental encoders have one limitation

Answer 31

A power interruption causes a loss of position information

Question 32

The following considerations are important when selecting a proximity sensor

Answer 32

Sensing speed required, level of contamination potential, the type of enclosure required, target materials (all of the above)

Question 33

Strain gauges and LVDTs are used to measure

Answer 33

Force, weight, tension

Question 34

Sensors are devices that respond to physical stimulus such as

Answer 34

Heat, light, pressure, flow (all of the above)

Question 35

These devices are used for both position and feedback.

Answer 35

Encoders

Question 36

These switches translate motion into switch actuation

Answer 36

Limit

Question 37

These sensors produce a voltage when exposed to light

Answer 37

photoelectric

Question 38

_______ systems integrate industrial computers with video cameras that provide data about the light it receives.

Answer 38

Vision