Motor Control 3: Lesson 3 - Analog Pilot Devices Flashcards
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
a. analog
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
b. position
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
c. transducer
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
b. 190.4°F
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
b. resistance
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
b. series
Thermocouples are temperature-sensing devices that produce a ______ when the temperature increases.
a. milliamp level amperage
b. megohm level resistance
c. millivolt level voltage
c. millivolt level voltage
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
b. –190°C to +800°C
Thermocouple transmitters generally produce 0-15 mA output signals.
True or False
False
Iron and constantan thermocouple wire are required for ______-type thermocouples.
a. E
b. J
c. K
d. T
b. J
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
True
______ 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
b. Rotary
______ 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
a. Linear
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
b. series
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
True
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
b. Differential pressure
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
a. bourdon tube
A common type of pressure sensor used to measure weight is the _______ sensor.
a. bourdon tube
b. differential pressure
c. load cell
c. load cell
Turbines and paddlewheels are often immersed directly in a process liquid and are used to measure _______.
a. flow
b. position
c. pressure
d. temperature
a. flow
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
c. vortex
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
b. Ultrasonic
Constant temperature and calorimetric sensors are types of ______ flow sensors.
a. mass
b. ultrasonic
c. vortex
a. mass
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
a. Coriolis
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
True
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
True
Proportional control valves are always controlled with an electronic voltage or current signal.
True or False
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.
Motor driven proportional control valves are generally ______ to operate than pneumatic control valves.
a. faster
b. slower
b. slower
______ are analog output devices that document industrial and commercial process data .
a. Control valves
b. Recorders
c. Ultrasonic flow meter
b. Recorders
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.
