Transducers part 1 Flashcards
Transducer
Device that converts one energy into another form of energy
Piezoelectric effect
Crystals to emit electric energy when pressure is applied
Reverse piezoelectric effect
Crystals to expand or contract when positive or negative electrical current is applied
Curie point
Temp of crystals heated while in the presence of a strong electrical field 30-400c
Natural elements
Quartz, tourmaline
Man made material
Zicronate titanate, barium titanite
Resonant frequency
Natural frequency, operating frequency
Bandwidth
Range of frequencies emitted
Narrow bandwidth
Emits few frequencies
Wide bandwidth
Short pulses create many frequencies
Q factor
Equal to operating frequency
High Q factor
Crystals ring for a long time
Lows factor
Rings for short time, pulse
Multi hertz transducer
Two more frequency ranges for transmission and reception
Harmonic
Frequencies are twice the fundamental frequency
Backing/damping
Less ringing
By limiting ringing
Bandwidth is increased
Backing is composed of
Epoxy resin impregnated w tungsten
Using damping causes
Number of cycles to decrease improving axial resolution
Axial resolution
2 structures on top of each other, parallel to the path of sound travel
Axial resolution determined by
SPL
2 ways to improve axial resolution
Use transducer w backing material,
Use high frequency transducer
Matching layer
Located in front of crystals to decrease the impedence difference between skin and crystals
Matching layer made of
Aluminum powder I’m epoxy resin
