medical

Piezoelectric transducer/crystal

Ability of particular materials to generate a potential difference by transferring mechanical energy to electrical energy

Applications of piezoelectric crystals

Microphone

Ultrasound

Ultrasound

A sound wave above the frequency of 20kHz

Generation of ultrasound waves

Alternate pd applied and changes pze crystal shape

Pze crystal vibrates and produces ultrasound

Frequency of crystal vibration matches frequency of alt pd so thats why it cut into different size for resonance

Detection of ultrasound waves

When ultrasound waves returns the crystal vibrates which produces alt pd across crystal

the received signal can be processed and used for medical diagnosis

Working of an ultrasound

Pulse of ultrasound is emitted from pze crystal

This is reflected from boundaries between media

The reflected pulse is detected by ultrasound transmitter

Signal is then processed and displayed on screen for further medical diagnosis

Ultrasound info 1

Intensity of reflection gives info about nature of the boundary

Ultrasound info 2

Time between transmission and receipt of the pulse (time delay) gives info on depth of boundary

Specific acoustic impedance

Product of density of medium and speed of ultrasound in medium

Greater the difference in acoustic impedance

Greater the reflection smaller transmission

Two materials with aame acoustic impedance

No reflection

Large difference

Ultrasound would b significantly reflected so coupling gel is necessary

Internal reflection coefficient