Knowledge Base 3 Flashcards by Richard van Horne

T F

Pilot duty devices are normally used to switch horsepower rated loads

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Which of the following is a primary control device

Flow Switch
Thermostat
Motor Start
Pressure Switch

motor starter

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T F

A push button would normally be considered to be a pilot control devvice

TRUE

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A manually operated switch is one that is controlled by ___

HAND

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What do the SPDT and DPDT switches look like

look at the pictures

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T F

The DC current rating of a switch would have a value of lower magnitude than the AC rating

TRUE

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Identity your symbols from page 1

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The NC push button ___ the circuit when it is pressed and returns to the ____ position when the button is released

OPENS

CLOSED

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Electrical ____ are designed to protect their contents from operating environmental conditions

Enclosures

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A push button may consist of one or more ____ blocks, a(n) ____ device, and a(n) _____plate

Contact Blocks

operator

legend

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_____head push button operators are used for emergency stop push buttons

Mushroom

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T F

A pushbutton assembly can only have one contact block

FASLE

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Once actuated, ______type pushbutton operators are required to be actuated a second time to return the contacts to their normal off state.

Maintained

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Emergency stop push buttons must be of the maintained contact type.

(True/False) _________

TRUE

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Draw the NEMA and IEC symbols used to represent a red pilot light:

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Push-to-test pilot lights can be energized from two separate signals of different voltage values. (True/False

TRUE

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All selector switches operate with spring return to provide momentary contact operation. (True/False)

FASLE

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Drum switches are only used for starting and reversing three-phase squirrel-cage motors. (True/False

FASLE

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A mechanically operated switch is one that is specifically controlled by hand. (True/False

False

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Limit switches are designed to be operated:

a. By the machine operator
b. When a predetermined pressure is reached
c. When a predetermined temperature is reached
d. By contact with an object

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Identify each of the switch symbols shown in Figure 4-3:

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The type of limit switch shown in Figure 4-4 would be classified as a

LEVER TYPE A

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Micro limit switches require a large amount of pressure to be applied to the operating lever in order to actuate the contacts.(True/False)

FALSE

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The type of temperature switch shown in Figure 4-5 is

Capillary tube temperature switch

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All temperature switches use only N.O. (normally open) contacts. (True/False)

FALSE

The three categories of pressure switches are _____________________ pressure, _________________ pressure, and _____________________ pressure.

Positive pressure Vacuum (negative pressure) Differential pressure

Pressure switches open or close when a preset pressure is reached. (True/False)

TRUE

The type of switch shown in Figure 4-6 would be classified as a

Float Switch

Sensors are devices that are used to ____________________ and ______________the presence of something

detect measure

A proximity sensor can detect the presence an object without physical contact. (True/False)

TRue

An inductive proximity sensor can be actuated by both conductive and nonconductive materials. (True/False)

TRUE

Identify each component block of the inductive proximity sensor shown in Figure 4-7.

1. Coil 2. Oscillator 3. Detector 4. Output

Draw acceptable NEMA and IEC symbols used to represent an N.O. proximity switch.

The proximity sensor shown in Figure 4-8 would be classified as a:

3 wire connection

A proximity sensor should never normally be used to directly operate a motor. (True/False)

TRUE

The electronic switching circuit of a sensor: a. Has infinite resistance in the off state b. Will allow a small amount of current to flow through it in the off state c. Will have a small voltage drop across it in the on state d. Both band c

When a metal object enters the high-frequency field of an inductive proximity, it causes:

In order to operate properly, a two-wire proximity sensor should be powered continuously. (True/False

True

The area between the operating and release points of a proximity sensor is known as the______________ zone.

hysteresis

The position identified on the field of the proximity sensor shown in Figure 4-9 is known as the:

Operating point

A capacitive proximity sensor produces an a. Electromagnetic sensing field b. Electrostatic sensing field c. Constant current sensing field d. Constant voltage sensing field

Electro-Static field

When the target enters the field of a capacitive proximity sensor, the oscillator circuit begins oscillating. (True/False)

True

Capacitive proximity sensors will sense only nonmetallic materials. (True/False)

False

Identify the two basic components of the photoelectric sensor shown in Figure 4-10.

A. Transmitter | B. Receiver

Identify the type of scan technique used for each of the photoelectric sensors shown in Figure 4-11.

a. Retroflective Scan b. Through Beam scan c. diffuse scan sensor

Which of the following scan techniques is best suited for long-range scanning? a. Through-beam b. Retroreflective c. Polarized retroreflective d. Diffuse

Through Beam

A_________________ retro reflective scan sensor is designed to be able to detect shiny objects.

TRUE

Fiber optics can be used with through-beam, retroreflective, or diffuse scan sensors. (True/False

TRUE

Fiber optic sensor systems are completely immune to all forms of electrical interference. (True/False

TRUE

Hall-effect sensors are used detect both the proximity and the_________________ of a magnetic field

strength

Identify the measurement application for the Hall-effect sensing circuits shown in Figure 4-12.

a. Hall efect sensor for monitering current | b. Hall effect sensor used for measuring speed

An ultrasonic sensor operates by sending high-frequency ________________ waves toward the target and measuring the ________________ it takes for the pulses to bounce back.

sounds time

For the ultrasonic sensor shown in Figure 4-13, the sensor will generate a signal of approximately___________ mA when the tank is full and ______________ mA when the tank is empty

20 ma when full 4 ma when empty

Identify each type of temperature sensor shown in figure 4-14

1. Thermo couple | 2.

Which of the following temperature sensors operates on the principle that electrical resistance of metals is directly proportional to temperature? a. IC b. RTD c. Thermocouple d. Thermistor

RTDs

The output voltage of a thermocouple is proportional to the difference in voltage between the _________________ junction and the _________________ junction.

hot junction cold junction

Different thermocouple types basically have the same voltage output curves. (True/False)

False

Which of the following temperature sensors provides the most accurate measurement of temperature? a. IC b. RTD c. Thermocouple d. Thermistor

RTD

The material most often used for resistance temperature detectors is a. Platinum b. Gold c. Copper d. Aluminum

Platinum

As the temperature of a thermistor with a negative temperature coefficient increases, its resistance decreases. (True/False)

TRUE

The operating temperature range of the IC temperature sensor is much lower than that of a thermocouple. (True/False)

TRUE

A tachometer generates a voltage that is proportional to

rotational speed

Identify the parts of the magnetic pickup sensor shown in Figure 4-15

a. magnet b. coil c. pole piece d. connector

A magnetic pickup sensor generates pulses that are counted to determine shaft speed. (True/False)

TRUE

An encoder sensor is used to convert linear or rotary motion into a binary _________________ signal

digital

Encoder sensors are used in applications such as robotic control where __________________ have to be accurately determined.

positions

Identify each type of flowmeter shown in Figure 4-16.

Left: Turbine flowmeter Right: Target Type flow meter

The usual approach taken to measure fluid flow is to convert the __________ energy that the fluid has into some other measurable form.

kenetic

Which of the flowmeters operates by measuring the changes of induced voltage of a conductive fluid? a. Magnetic b. Target c. Turbine d. Differential pressure

Magnetic

An actuator is any device that converts an electrical signal into ___________________________________________ .

mechanical movement

The contacts of an electromechanical relay are switched by energizing and de-energizing a(n) ________________________

coil

The normally closed contact of a relay is closed any time the coil is energized. (True/False) _________

False

A solenoid is made up of coil with a movable ______________________

plunger

Which type of solenoid is shown in Figure 4-17

Rotary

An AC solenoid rated for 120-V alternating current, if connected to a 120- V direct current source, would draw a much lower than normal current. (True/False)

FALSE

If a DC solenoid sticks in the open position, a burnout of the coil is likely. (True/False)

FALSE

In AC solenoids, coil current decreases as the plunger moves toward the seated position. (True/False)

A solenoid valve is a combination of a solenoid coil operator and: a. Contacts b. Sensor c. Transmitter d. Valve

When a solenoid valve is electrically energized it can be designed to a. Open the flow of media b. Shut off the flow of media c. Direct the flow of media d. All of these

Stepper motors rotate continuously when voltage is applied to their terminals. (True/False)

TRUE

For a DC stepper motor, the amount of rotation is directly proportional to the __________________ of pulses and the speed to the _______________________ of the pulses.

number frequencey

Generally, stepper motors are rated for more than 1 hp and are used to operate very heavy loads. (True/False

False

Stepper motor systems can provide precise position control of movement without the use of a feedback signal. (True/False)

TRUE

Stepper motor systems can provide precise position control of movement without the use of a feedback signal. (True/False)

TRUE

An open-loop motor control system is one that is operated: a. Without a feedback signal b. With a feedback signal c. Without a reference signal d. With a reference signal

All servo motors operate using a closed-loop control system. (True/Fa1se)

TRUE

Identify all blocks for the servo motor control system shown in Figure 4-18

A. Servo Motor B. Controller C. Servo Amplifier D. Feedback device

Brushless DC motors are mechanically commutated.

False