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05 Handout 1

Eljin Aguilar Fundamentals of Mixed Signals and Sensors hard English 71 cards

Cards in this deck (71)

  1. 1sensorit senses the quantity that needs to be observed or measured,
  2. 2transducerit converts into a form that can be observed or used in a subsequent operation.
  3. 3measurandThe variable that is measured is termed __
    Examples are acceleration and velocity of a vehicle, torque into a robotic joint, strain in a structural member, temperature and pressure of a process plant, and current through an electric circuit
  4. 4measurementThe output of the sensor unit is the __
    For example, while the measurand of an accelerometer is the acceleration, the accelerometer output may be a charge or a voltage.
  5. 5Range/Span Error Accuracy Precision Hysteresis Linearity Reliability Resolution SensitivitySensor/Actuator Specifications
  6. 6Range/SpanThis defines the maximum and minimum values of the quantity that the sensor or instrument is designed to measure.
  7. 7ErrorThis is the difference between a measured value and its true value.
  8. 8Random errorsit produce scatter within repeated readings. The effects of it also be reduced by taking the average of these repeated readings.
  9. 9Systematic errorsit affect all readings in a similar manner and are caused by factors such as miscalibration.
  10. 10Accuracydescribes the maximum expected error associated with a measurement (or a sensor) and may be expressed as an absolute value or as a percentage of the range of the system.
  11. 11Precisiona measure of the lack of random errors (scatter) produced by a sensor or instrument. Devices with this high will produce repeated readings with very little spread.
  12. 12Hysteresisit is the deviation of the sensor’s output at any given point when approached from two different directions caused by electrical or mechanical systems.
  13. 13LinearityIn most situations, it is convenient to have a sensor where the output is linearly proportional to the quantity being measured.
  14. 14Reliabilitya statistical measure of the quality of a device, that indicates the ability of the device to perform its stated function.
  15. 15Resolutionthe smallest discernible change in the measured quantity that the sensor can detect. This is usually expressed as a percentage of the range of the device.
  16. 16Sensitivitya measure of the change produced at the output for a given change in the quantity being measured. A sensor that has high sensitivity will produce a large change in its output for a given input change.
  17. 17Deadbandthe lack of response or insensitivity of a device over a specific range of the input.
  18. 18Biomedical Chemical Electrical/electronic Mechanical ThermofluidSensor Classification based on Measurand
  19. 19BiomedicalMotion, force, blood composition, blood pressure, temperature, flow rate, urine composition, excretion composition, ECG, breathing sound, pulse, x-ray image, ultrasonic image.
  20. 20ChemicalOrganic compounds, inorganic compounds, concentration, heat transfer rate, temperature, pressure, flow rate, humidity.
  21. 21Electrical/electronicVoltage, current, charge, passive circuit parameters, electric field, magnetic field, magnetic flux, electrical conductivity, permittivity, permeability, reluctance.
  22. 22Mechanical Force(effort including torque), motion (including position and deflection), optical image, other images (x-ray, acoustic, etc.), stress, strain, material properties (density, Young’s modulus, shear modulus, hardness, Poisson’s ratio).
  23. 23ThermofluidFlow rate, heat transfer rate, infrared waves, pressure, temperature, humidity, liquid level, density, viscosity, Reynolds number, thermal conductivity, heat transfer coefficient, Biot number, image.
  24. 24Temperature sensors Light sensors Force sensors Displacement sensors Motion sensors Sound sensorsSensor Classification based on Technology
  25. 25Temperature sensorsIt is a fundamental part of many controls and monitoring systems, ranging from simple temperature-regulating systems for buildings to complex industrial process-control plants.
  26. 26Resistive thermometersThe electrical resistance of all conducting materials changes with temperature. The resistance of a piece of metal varies linearly with its absolute temperature.
  27. 27ThermistorsIt also change their resistance with temperature. However, they use materials with high thermal coefficients of resistance to give much improved sensitivity.
  28. 28pn junctionsIt is a semiconductor device that has the properties of a diode. That is, it conducts electricity in one direction but opposes the flow of electricity in the other direction.
  29. 29Light sensorsSensors for measuring light intensity fall into two main categories those that generate electricity when illuminated and those whose properties change under the influence of light.
  30. 30PhotovoltaicLight falling on a pn junction produces a voltage and can therefore be used to generate power from light energy. This principle is used in solar cells.
  31. 31PhotoconductiveThis sensors do not generate electricity, but their conduction of electricity changes with illumination. It described above as a photovoltaic device may also be used as a photoconductive device.
  32. 32Fiber optic communication sensorsAs its name implies,it involves the transmission of information by sending pulses of light through an optical fiber.
  33. 33Image sensorsThese are used within smartphones, digital cameras, video cameras, webcams, and a wide range of other devices that can capture images and convert them into electrical signals
  34. 34Force sensorsThese are sensors that help in measuring the amount of force applied to an object. By observing the amount of change in the resistance values of force sensing resistors, the applied force can be calculated.
  35. 35Strain gaugeThe shape of such an object may be changed by applying an external force to it. The term stress is used to define the force per unit area applied to the object, and the term strain refers to the deformation produced.
  36. 36PiezoelectricThese materials have the characteristic that they generate an electrical output when subjected to mechanical stress. These transducers are more commonly used for measuring variations in forces rather than their steady value.
  37. 37Displacement sensorsposition may be sensed using a very wide range of methods, including resistive, inductive, mechanical, and optical techniques. As with many classes of sensors, both analog and digital types are used.
  38. 38PotentiometersThey are among the most common position transducers, and most people will have encountered them as the controls used in radios and other electronic equipment.
  39. 39Inductive sensorsThe inductance of a coil is affected by the proximity of ferromagnetic materials. The proximity of a ferromagnetic plate is determined by measuring the inductance of a coil.
  40. 40SwitchesThese are the simplest digital displacement sensors . These are used in many forms and may be manually operated or connected to a mechanism of some kind.
  41. 41Opto switchesIt consists of a light sensor, usually a phototransistor, and a light source, usually a light emitting diode, housed within a single package.
  42. 42Absolute position encodersA pattern of light and dark areas is printed onto a strip and is detected by a sensor that moves along it. The pattern takes the form of a series of lines that alternate between light and dark.
  43. 43Incremental position encodersIt has only a single detector, which scans a pattern consisting of a regular series of stripes perpendicular to the direction of travel. As the sensor moves over the pattern, the sensor will detect a series of light and dark regions in which the distance moved can be determined by counting the number of transitions.
  44. 44Optical gratingsThis can take many forms. A simple version being formed by printing a pattern of opaque stripes on a transparent film. The stripes are parallel and have lines and spaces of equal widths.
  45. 45RangefindersMeasurement of large distances usually requires a non contact method. Both passive systems and active systems are available. Passive techniques include optical triangulation methods, in which two slightly displaced sights are aligned on a common target. Active systems transmit either sound or electromagnetic energy and detect the energy reflected from a distant object. By measuring the time taken for the energy to travel to the object and back to the transmitter, the distance between them may be determined.
  46. 46Motion sensorsIn addition to the measurement of displacement, it is often necessary to determine information concerning the motion of an object, such as its velocity or acceleration. A range of other velocity sensors exists for different applications.
  47. 47Tacho generatorIt can be used to measure rotational speed. This is a small DC generator that produces a voltage proportional to its speed of rotation.
  48. 48Doppler radarIt is used in ‘radar’ speed detectors. Here a beam of sound or electromagnetic radiation is directed at the moving object, and the reflected radiation is detected and compared with the original transmission.
  49. 49AccelerometerMost of these make use of the relationship between force, mass, and acceleration. A mass is enclosed within the sensor. When the device is subjected to acceleration, the mass experiences a force.
  50. 50Sound sensorsSince sound represents variations in air pressure, the objective of the microphone is to measure these variations and to represent them by some form of electrical signal (often in the form of a varying voltage).
  51. 51Carbon microphonesSound waves are detected by a diaphragm, which forms one side of an enclosure containing carbon particles. Sound waves striking the diaphragm cause it to move, compressing the carbon particles to a greater or lesser degree and thus affecting their resistance. Electrodes apply a voltage across the particles, and the resulting current thus relates to the sound striking the device.
  52. 52Capacitive microphonesThese are similar in operation to the carbon microphone described above except that movement of the diaphragm causes a variation in capacitance rather than resistance. This is achieved by arranging that motion of the diaphragm changes the separation of two plates of a capacitor, thereby varying its capacitance.
  53. 53Moving coil microphonesIt consists of a permanent magnet and a coil connected to a diaphragm. Sound waves move the diaphragm, which causes the coil to move with respect to the magnet, thus generating an electrical signal.
  54. 54Piezoelectric microphonesIt can also be used as a microphone. The diaphragm is made of piezoelectric material, which is distorted by sound waves producing a corresponding electrical signal. This technique is often used for ultrasonic sensors, which are used over a wide range of frequencies.
  55. 55ActuatorsIn addition to being able to sense physical quantities in their environment, systems must also be able to affect the outside world in some way so that their various functions can be performed. This might require the system to move something, change its temperature, or simply provide information via some form of display.
    They are transducers since they convert one physical quantity into another.
  56. 56Heat actuators Light actuators Force, displacement, and motion actuators Sound actuatorsActuator Classification based on Technology
  57. 57Heat actuatorsMost heating elements may be considered as simple resistive heaters, which output the power that they absorb as heat. Special heating cables and elements are available for larger applications, which may dissipate many kilowatts.
  58. 58Light actuatorsMost lighting for general illumination is generated using conventional incandescent or fluorescent lamps. The power requirements of such devices can range from a fraction of a watt to hundreds or perhaps thousands of watts.
  59. 59Light emitting diodesOne of the most common light sources used in electronic circuits. This is a semiconductor diode constructed in such a way that it produces light when a current passes through it.
  60. 60Liquid crystal displays Liquid crystal displays (LCDs)it consist of two sheets of polarized glass with a thin layer of oily liquid sandwiched between them. An electric field is used to rotate the plane of polarization of the liquid in certain regions, making some parts of the display opaque while others are transparent.
  61. 61Fiber optic communicationFibers are usually made of either an optical polymer or glass. Glass fibers have a much lower attenuation and can be used over several hundred kilometers, but they are more expensive than polymer fibers. Short range fiber optic communication systems normally make use of LEDs as the light source, since they combine very high speed with a relatively low cost.
  62. 62Force, displacement, and motion actuatorsIn practice, actuators for producing force, displacement, and motion are often closely related.
  63. 63SolenoidsIt consists of an electric coil and a ferromagnetic slug that can move into or out of the coil. When a current is passed through it, the slug is attracted towards the center of the coil with force determined by the current in the coil.
  64. 64MetersPanel meters are important output devices in many electronic systems providing a visual indication of physical quantities.
  65. 65MotorsIt have various forms can be used as force, displacement, or motion actuators. The motors fall into three broad types AC motors, DC motors, and stepper motors.
  66. 66AC motorsare primarily used in high power applications and situations where great precision is not required. Control of these motors is often by simple ON/OFF techniques.
  67. 67DC motorsare extensively used in precision position control systems and other electronic systems, particularly in low power applications.
  68. 68Stepper motorsmove in discrete steps, and their speed of rotation is directly controlled by the input waveform used. This combination of speed and controllability, together with small size and relatively low cost, makes stepper motors an attractive option in many applications.
  69. 69Sound actuatorsThe sound that we hear is basically made up of mechanical vibrations produced by an Audio Sound Transducer used to generate the acoustic waves, and for sound to be heard, it requires a medium for transmission either through the air, a liquid, or a solid.
  70. 70SpeakersMost speakers (or loudspeakers) have a fixed permanent magnet and a movable coil connected to a diaphragm. Input to the speaker generates a current in the coil, which causes it to move with respect to the magnet, thereby moving the diaphragm and generating sound.
  71. 71Ultrasonic transducersAt very high frequencies, the permanent magnet speakers are often replaced by
    piezoelectric actuators. Such transducers are usually designed to operate over a narrow range of frequencies.

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hard Fundamentals of Mixed Signals and Sensors Flashcards on 05 Handout 1, created by Eljin Aguilar on 30/10/2024.
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Eljin Aguilar
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