Motor Control 3: Lesson 3 - Analog Pilot Devices

Question 1

Transducers convert a variable such as temperature, position, flow, or pressure into a(an) ______ signal that is used by the control system.

a. analog
b. discrete
c. output

Answer 1

a. analog

Question 2

Resistance temperature detectors (RTDs) and thermocouples are typical of analog sensing devices that measure ______ in a process.

a. flow
b. position
c. pressure
d. temperature

Answer 2

b. position

Question 3

A ______ is a device that receives one type of energy and converts it to another type of energy and generally includes a sensor and a transmitter.
Select one:

a. potentiometer
b. thermistor
c. transducer

Answer 3

c. transducer

Question 4

A thermistor is used to measure temperature in a process. The circuit includes an indicator that shows the temperature to be 88°C. Convert the Celsius temperature to its equivalent Fahrenheit value.

a. 120°F
b. 190.4°F
c. 216°F

Answer 4

b. 190.4°F

Question 5

RTDs and thermistors are temperature sensing devices that exhibit a change in _______, which is dependent upon the temperature of the device.

a. current
b. resistance
c. voltage

Answer 5

b. resistance

Question 6

When two or more thermocouples are connected in ______ to increase the output voltage from the sensor, the connection is referred to as a thermopile.

a. parallel
b. series

Answer 6

b. series

Question 7

Thermocouples are temperature-sensing devices that produce a ______ when the temperature increases.

a. milliamp level amperage
b. megohm level resistance
c. millivolt level voltage

Answer 7

c. millivolt level voltage

Question 8

What is the temperature range that a Type J thermocouple can sense in a process?

a. –190°C to +400°C
b. –190°C to +800°C
c. –190°C to +1000°C

Answer 8

b. –190°C to +800°C

Question 9

Thermocouple transmitters generally produce 0-15 mA output signals.

True or False

Answer 9

False

Question 10

Iron and constantan thermocouple wire are required for ______-type thermocouples.

a. E
b. J
c. K
d. T

Answer 10

b. J

Question 11

When considering response time to a change in stator temperature in a motor, thermocouples are faster than RTDs and would provide a quicker response than an RTD.

True or False

Answer 11

True

Question 12

______ potentiometers position sensors detect the angular or rotational position of a shaft. As the shaft rotates, the position of the potentiometer shaft rotates as well, and the resistance output of the sensor changes to indicate that shaft’s position.

a. Linear
b. Rotary

Answer 12

b. Rotary

Question 13

______ potentiometer position sensors sense the linear motion or position of some object or process that moves in a straight line. As the object moves, the shaft of the potentiometer attached to the object moves, changing the position of the potentiometer.
Select one:

a. Linear
b. Rotary

Answer 13

a. Linear

Question 14

A linear variable differential transformer has three windings. The primary winding is connected to an AC voltage. The secondary windings are connected in ______, and the output from these windings represents the position of the process being monitored.

a. parallel
b. series

Answer 14

b. series

Question 15

When the core of a linear variable differential transformer (LVDT) is in the center or null position, the voltages in the two secondary transformers are equal. Since these transformers are connected to oppose each other, the resulting output voltage is zero since the voltages cancel each other out.

True or False

Answer 15

True

Question 16

Which type of pressure sensor replaces atmospheric pressure as a reference pressure with a second process pressure?

a. Bourdon tube
b. Differential pressure
c. Solid-state pressure

Answer 16

b. Differential pressure

Question 17

A ______ pressure sensor often uses an LVDT to sense position relative to the pressure applied to the sensor.

a. bourdon tube
b. differential
c. solid-state

Answer 17

a. bourdon tube

Question 18

A common type of pressure sensor used to measure weight is the _______ sensor.

a. bourdon tube
b. differential pressure
c. load cell

Answer 18

c. load cell

Question 19

Turbines and paddlewheels are often immersed directly in a process liquid and are used to measure _______.

a. flow
b. position
c. pressure
d. temperature

Answer 19

a. flow

Question 20

A(n) ______ flow sensor uses an object called a bluff body, which is placed in the fluid flow to produce whirlpools or eddies in the fluid flow stream.

a. mass
b. ultrasonic
c. vortex

Answer 20

c. vortex

Question 21

What type of flow meter requires that particles must be present in the fluid being monitored to reflect signals back to the flow sensor?

a. Mass
b. Ultrasonic
c. Vortex

Answer 21

b. Ultrasonic

Question 22

Constant temperature and calorimetric sensors are types of ______ flow sensors.

a. mass
b. ultrasonic
c. vortex

Answer 22

a. mass

Question 23

What type of flow meter depends upon the twist of the tube containing the flowing fluid to sense flow rate?

a. Coriolis
b. Mass
c. Ultrasonic
d. Vortex

Answer 23

a. Coriolis

Question 24

Discrete control valves are either open or closed. Since these valves have only two states, they do not require analog input signals and operate simply by applying the appropriate voltage to the coil of the valve.

True or False

Answer 24

True

Question 25

Proportional control valves respond to an analog signal and adjust flow over a range of 0% to 100% of the capacity of the valve. The rate of flow in these valves is proportional to the analog signal applied to the valve.

True or False

Answer 25

True

Question 26

Proportional control valves are always controlled with an electronic voltage or current signal.

True or False

Answer 26

False

Note: Some proportional control valves are controlled with an analog pressure signal, generally 3-15 pounds per square inch (psi). This pressure is sometimes created, however, with a current-to-pressure converter which converts a 4-20 mA electronic signal into a 3-15 psi pressure signal.

Question 27

Motor driven proportional control valves are generally ______ to operate than pneumatic control valves.

a. faster
b. slower

Answer 27

b. slower

Question 28

______ are analog output devices that document industrial and commercial process data .

a. Control valves
b. Recorders
c. Ultrasonic flow meter

Answer 28

b. Recorders

Question 29

Drag the green check mark to indicate the proper test equipment to use in troubleshooting analog pilot devices, selecting the most appropriate equipment for each device. (Note: Some devices may require two or more types of equipment.) Drag the red “x” to show items that are not appropriate for troubleshooting the device. Each box must contain a selection to receive full credit.

Answer 29