chapter 7
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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 A speaker converts an electrical signal into a
sound signal.
7-2 Temperature
Thermistor a device constructed of a
metal-oxide or semiconductor material with a resistance that changes dramatically with temperature
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.
7-3 Light IntensityPhotoresistor (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
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
Photodiodea device that is similar to a solar cell
except that it is manufactured to detect light, not to power devices
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
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
7-6 PositionPotentiometer
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
7-9 Magnetic FieldHall 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
7-10 Particle DetectorsGeiger-Muller Tube
a device used to detect ionizing radiationionizing radiation is very high energy
radiation associated with nuclear disintegrations
current "spikes" are counted
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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