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Sensors & Actuators > Final Exam > Flashcards

Final Exam Flashcards

1
Q

Describe what sensors are and give several examples of sensors

A
  • Devices that respond to physical stimulus and transmits a resulting impulse. (Ex: thermometer, motion sensor, pressure sensor)
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2
Q

Describe what actuators are and give several examples of actuators

A
  • Mechanical response to stimulus, mechanism for moving or controlling something.
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3
Q

What is the difference between continuous and discrete sensors and actuators? Give examples.

A

Continuous devices can generate or respond to signals having an infinite number of levels or values (ex: 0-3.3 V), discrete devices can only respond to binary values (ex: high or low)

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4
Q

What is a pressure transducer?

A

Measures the pressure and then returns a scaled voltage.

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5
Q

What is the ratio of power and field related values in decibels?

A

P=10log(P/Po) for power

V=20log(V/Vo) for fields

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6
Q

What does monotonic mean?

A

Function is either increasing or decreasing.

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7
Q

input impedance.

A

Ratio of the rated voltage and the resulting current through the input port of the device with the output port open (no load)

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8
Q

output impedance.

A

Ratio of the rated output Voltage and short circuit current of the port (i.e. current when the output is shorted)

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9
Q

What is the difference between range and dynamic range?

A

Range is the lowest and highest values of the stimulus and dynamic range is the ratio between the upper and lower limits (absolute quantities) or span (relative quantities)

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10
Q

Error

A

Deviation from “ideal” aka uncertainty

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11
Q

Hysteresis

A

The deviation of the sensor’s output at any given point when approached from opposite directions

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12
Q

Saturation

A

A property of sensors or actuators when they no longer respond to the input changes

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13
Q

Deadband

A

lack of response or insensitivity of a device over a specific range of the input.

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14
Q

Excitation

A

electrical supply required for operation of an active sensor or actuator

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15
Q

Accuracy vs Precision

A

Accuracy - closeness of measured value to standard or known value.
Precision - closeness of 2 or more measurements to each other.

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16
Q

What are the 3 broad categories of electrical temperature sensors?

A

RTD, thermistor, and thermocouple

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17
Q

Thermocouples

A

uses 2 metal wires to produce a voltage relative to the temperature present in the junction between them.

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18
Q

Resistance Temperature Detectors (RTDs)

A

measures temperature based on the resistance changes in a metal resistor inside.

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19
Q

Thermistors

A

is like an RTD but contains a ceramic or polymer resistor instead of metal.

20
Q

Self Heating in RTDs

A

subject to error due to rise in their temperature produced by the heat generated by the current used to measure their resistance.

21
Q

What are the 3 broad types of transistors?

A

JFET, MOSFET and BJT

22
Q

JFET

A

Junction Field Effect Transistor - voltage controlled, 3 terminal uni polar semiconductor device.

23
Q

MOSFET

A

Metal Oxide Semiconductor Field Effect Transistor - voltage controlled field effect transistor that is electrically insulated from the main semiconductor channel. No current flows into the gate.

24
Q

BJT

A

Bipolar Junction Transistor - Current regulating devices that control amount of current flowing through them from emitter to collector.

25
Q

Name a transistor application

A

switching, digital logic, amplification

26
Q

What is a Darlington Pair and why would you use it?

A

2 BJTs connected together. The Emitter of one is connected to the Base of the other to produce a more sensitive transistor with a larger current gain. Useful in applications where current amplification or switching is required

27
Q

Load Regulation

A

indication of how much the load voltage will change when the load current changes

28
Q

Line Regulation

A

indication of how much load voltage will change when the line (input, supply) voltage changes.

29
Q

Shunt Regulator

A

a form of regulator where the regulating element shunts the current to ground. ex: Zener Diode

30
Q

Series Regulator

A

provides an effective form of voltage regulation within a linear power supply. Improved efficiency and low noise.

31
Q

Buck Regulator

A

DC to DC step down converter

32
Q

Boost Regulator

A

DC to DC step up converter

33
Q

Freewheeling (Flyback) Diode

A

used to eliminate sudden voltage spikes across an inductive load when supply current is suddenly reduced or interrupted.

34
Q

What quantity is most likely associated with generation of electric fields and closely associated with generation of magnetic fields?

A

Current

35
Q

Diamagnetic, Paramagnetic, Ferromagnetic

A

Diamagnetic (weak repulsion from strong fields)
Paramagnetic (weak attraction to strong fields)
Ferromagnetic (strong attraction, can form permanent magnets)

36
Q

Inductive Proximity Sensors

A

as the sensor gets closer to the sensed surface the inductance of the coil increases if the sense surface is ferromagnetic.

37
Q

Eddy Current Proximity Sensors

A

ability of AC magnetic fields to induce currents in conducting media. Currents produced in material create a field which opposes originals field reduces the net flux through sensor coil.

38
Q

LVDTs

A

Linear Variable Differential Transformer, the distance between 2 coils of a transformer is varied.

39
Q

Hall Effect Sensors

A

consists of a current carrying metal strip that is placed inside any transverse magnetic field. An EMF is developed across the edges of this current carrying metal strip. The magnitude of this developed EMF is depending upon the density of the flux and mobility of electron.

40
Q

Brushed DC Motor

A

A brushed motor has a rotating set of wound wire coils which acts as an electromagnet with 2 poles. Poles push and pull against permanent magnets on outside of the motor. Inertia keeps motor going in proper direction.

41
Q

Brushless DC Motor

A

uses a permanent magnet external rotor, 3 phases of driving coils, position sensor. Coils are activated by electronic speed controller as cued by signals from the rotor position sensors.

42
Q

3 Parameters used to quantify motor behavior

A

Excitation Type, Voltage or current rating, Speed, Power, Efficiency

43
Q

Servo Motors, Stepper Motors, and solenoids

A

Servo motors - continuous rotation motors
Stepper motors - incremental rotation
Solenoids - designed for short distance linear motion

44
Q

Permanent Magnetic (PM) vs Variable Reluctance (VR) stepper motors

A

PM can only operate on DC Power

VR can operate on AC or DC

45
Q

H-Bridge

A

configuration of relays, transistors or other devices to reverse the polarity of the energizing voltage.

Sensors & Actuators (1 decks)

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