Lecture Sensors and analytical devices: Sensor technologies - Nguyễn Công Phương

The main contents of this chapter include all of the following: Capacitive sensors, resistive sensors, magnetic sensors, hall – effect sensors, piezoelectric transducers, strain gauges, piezoresistive sensors, optical sensors, ultrasonic transducers, nuclear sensors, microsensors.
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Lecture Sensors and analytical devices: Sensor technologies - Nguyễn Công Phương Nguyễn Công PhươngSensors and Analytical Devices Some Basic Measurement Methods, Sensors Technologies ContentsA. IntroductionB. Sensors CharacteristicsC. Some Basic Measurement MethodsD. Measurement Systems sites.google.com/site/ncpdhbkhn 2 Some Basic Measurement MethodsI. Sensor TechnologiesII. Temperature MeasurementIII. Pressure MeasurementIV.Flow MeasurementV. Level MeasurementVI.Mass, Force, and Torque MeasurementVII.Translational Motion, Vibration, and Shock MeasurementVIII.Rotational Motion Transducers sites.google.com/site/ncpdhbkhn 3 Sensor Technologies1. Capacitive Sensors2. Resistive Sensors3. Magnetic Sensors4. Hall – Effect Sensors5. Piezoelectric Transducers6. Strain Gauges7. Piezoresistive Sensors8. Optical Sensors9. Ultrasonic Transducers10. Nuclear Sensors11. Microsensors sites.google.com/site/ncpdhbkhn 4 Capacitive Sensors SC   r 0 d S d • d is variable, or • εr is variable, or • S is variable. sites.google.com/site/ncpdhbkhn 5 Resistive Sensors• They rely on variation of the resistance of a material when the measured variable is applied to it.• This principle is applied most commonly in temperature measurement using resistance thermometers or thermistors.• It is also used in displacement measurement using strain gauges or piezoresistive sensors.• Some moisture meters work on the resistance – variation principle. sites.google.com/site/ncpdhbkhn 6 Sensor Technologies1. Capacitive Sensors2. Resistive Sensors3. Magnetic Sensors a) Inductive Sensors b) Variable Reluctance Sensors c) Eddy Current Sensors4. Hall – Effect Sensors5. Piezoelectric Transducers6. Strain Gauges7. Piezoresistive Sensors8. Optical Sensors9. Ultrasonic Transducers10. Nuclear Sensors11. Microsensors sites.google.com/site/ncpdhbkhn 7 Inductive Sensors i V I 2 fL( d ) + – v V  L( d )  2 fI  d  f (V , I , f ) Displacement d• To measure translational & rotational displacement. sites.google.com/site/ncpdhbkhn 8 Variable Reluctance Sensors  d ( ) v dt    f (V ) N• To measure rotational V velocities. S sites.google.com/site/ncpdhbkhn 9 Eddy Current Sensors Thin metal sheet Sensor• To measure the displacement sites.google.com/site/ncpdhbkhn 10 Sensor Technologies1. Capacitive Sensors2. Resistive Sensors3. Magnetic Sensors4. Hall – Effect Sensors5. Piezoelectric Transducers6. Strain Gauges7. Piezoresistive Sensors8. Optical Sensors9. Ultrasonic Transducers10. Nuclear Sensors11. Microsensors sites.google.com/site/ncpdhbkhn 11 Hall – Effect Sensors Current I V  KIB Output voltage V + – V B KI Applied magnetic field B• Basically to measure the magnitude of a magnetic field.• Can be a proximity sensor• Used in computer keyboard push buttons sites.google.com/site/ncpdhbkhn 12 Piezoelectric Transducers (1) kFd V A http://www.ask.com/wiki/Piezoelectricity• V: the induced voltage (its polarity depends on whether the material is compressed or stretched)• k: the piezoelectric constant• F: the applied force• d: the thickness of the material• A: the area of the material• They produce an output voltage when a forcce is applied to them,• Or being applied a voltage, they produce an output force. sites.google.com/site/ncpdhbkhn 13 Piezoelectric Transducers (2)• Used frequently as ultrasonic transmitters & receivers. – Transmitters: application of a sinusoidal voltage at a frequency in the ultrasound range causes sinusoidal variations in the thickness of the material & results in a sound wave being emitted at the chosen frequency. – Receivers: sinusoidal amplitude variations in the ultrasound wave received are translated into sinusoidal changes in the amplitude of the force applied to the piezoelectric transducer.• Also used as displacement transducers (particularly as part of devices measuring acceleration, force, & pressure). sites.google.com/site/ncpdhbkhn 14 Sensor Technologies1. Capacitive Sensors2. Resistive Sensors3. Magnetic Sensors4. Hall – Effect Sensors5. Piezoelect ...