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Name: __________________ ECM 203 Ch 6 Homework
True/False
Indicate whether the statement is true or false.
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1. The NO (normally open) contacts of a relay are open when the relay coil is energized.
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2. A proximity switch can be actuated without any physical contact.
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3. A thermocouple, when heated, increases its resistance value.
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4. A capacitive proximity sensor may be actuated only nonconductive materials.
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5. A latching relay instruction would be considered to be nonretentive.
Multiple Choice
Identify the choice that best completes the statement or answers the question.
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6. Which of the following devices would "not" be classified as an actuator?
a. solenoid
c. relay
b. tachometer
d. motor
7. Essentially, a seal-in circuit is a method of maintaining current flow:
a. during a power failure
b. after a power failure
c. after a momentary switch has been pressed and released
d. for a specific period of time
8. Which of the following applications would "not" normally require the use of a contactor in conjunction with
the PLC output(s)?
a. control of several pilot lights to indicate sequence of a machine's operation
b. control of a high voltage transformer
c. control of a high current lighting load
d. control of a 10 HP motor
9. Which of the following would be classified as a manually operated switch?
a. pressure switch
c. DIP switch
b. temperature switch
d. level switch
10. Which of the following would "not" be a typical application for a proximity sensor?
a. Object being detected is too small to operate a mechanical switch.
b. A counting application requires a rapid response and high switching rate.
c. A high current capacity switch is required.
d. Long life and reliable service are required.
11. With a current-sinking output proximity sensor:
a. an NPN transistor is used and the load is connected between the positive supply and
sensor.
b. an NPN transistor is used and the load is connected between the sensor and ground.
c. a PNP transistor is used and the load is connected between the positive supply and sensor.
d. a PNP transistor is used and the load is connected between the sensor and ground.
12. A through-beam photoelectric sensor is used to measure the change in ____ caused by the target crossing the
optical axis.
a. resistance
c. current
b. voltage
d. light quantity
____ 13. When a magnetic pickup sensor is used to indicate the speed of a shaft, the speed is usually determined by
measuring the:
a. voltage output produced
c. frequency of the pulses produced
b. current output produced
d. change in resistance that occurs
____ 14. Flow through the orifice of a solenoid valve depends on whether the solenoid ____ is energized or
de-energized.
a. coil
c. plunger
b. core
d. disc
____ 15. In order to operate properly, a proximity sensor should be powered:
a. only when the target approaches the proximity sensor face
b. only when the target is aligned with the sensor face
c. only when the target moves
d. continuously
Completion
Complete each statement.
16. Motor overload relay contacts are normally hardwired in ____________________ with the magnetic starter
coil.
17. A transducer is a device that converts energy from one ____________________ to another.
18. Most industrial photoelectric sensors use a ____________________ for the light source, and a
____________________ to sense the presence or absence of light.
19. A ____________________-type photoelectric sensor is used to detect the light beam reflected from the target.
20. A bar code system consists of three basic elements: the bar code ____________________, a
____________________, and a ____________________.