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Chapter 7

Chapter 7. Transducers. 7-1 Introduction. Input Transducer A device which converts a non-electrical signal into an electrical signal A microphone converts a sound signal into an electrical signal. Output Transducer A device which converts an electrical signal into a non-electrical signal

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Chapter 7

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  1. Chapter 7 Transducers

  2. 7-1 Introduction • Input Transducer • A device which converts a non-electrical signal into an electrical signal • A microphone converts a sound signal into an electrical signal. • Output Transducer • A device which converts an electrical signal into a non-electrical signal • A speaker converts an electrical signal into a sound signal.

  3. 7-2 Temperature • Thermistor • a device constructed of a metal-oxide or semiconductor material with a resistance that changes dramatically with temperature

  4. Platinum Resistance Temperature Detector (PRTD) • a resistor that has a resistance that increases linearly with temperature • Thermocouple • Whenever a temperature gradient is established across a metal, a potential develops. • This is called the thermoelectric effect. • A thermocouple uses the junction of two dissimilar metals to measure temperature. • See also Peltier Coolers.

  5. 7-3 Light Intensity • Photoresistor (a.k.a. photocell) • a device made of cadmium sulfide, a compound which exhibits a change in resistance when exposed to different intensities of light

  6. Photovoltaic Cell (a.k.a. solar cell) • a solid-state device composed of a p-n junction that produces a voltage across its terminals when light shines on the device • Photodiode • a device that is similar to a solar cell except that it is manufactured to detect light, not to power devices

  7. Phototransistor • a two-terminal device which allows current to flow proportionally to the intensity of light striking the surface of the unit • Photomultiplier (a.k.a. photometer) • a device use to detect very low light levels (e.g. astronomy) • light strikes the cathode of this device causing electrons to cascade through an array of anodes

  8. 7-5 Force • Strain Gauge • a device whose change in resistance is related to changes in length • Piezoelectric Transducer • a crystalline material that generates a voltage when deformed • this device call also be deformed if a voltage is applied

  9. 7-6 Position • Potentiometer • the simplest form of a position transducer • angular measurement is accomplished quite simply • Variable Capacitor • displacements may be measured capacitively by attaching a plate to the object which is moving and another plate to a fixed point

  10. 7-9 Magnetic Field • Hall Effect Probe • When a current-carrying conductor is placed in a magnetic field, charge is displaced from its path and collects on opposites sides of the conductor

  11. 7-10 Particle Detectors • Geiger-Muller Tube • a device used to detect ionizing radiation • ionizing radiation is very high energy radiation associated with nuclear disintegrations • current "spikes" are counted

  12. 7-7 Sound • What do you need to make a speaker? • Permanent Magnet • Coil of Wire • Flexible Cone on a Frame • Can speakers also be used as microphones?

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