2. TRANSDUCERS
A TRANSDUCER MAY BE DEFINED AS A DEVICE THAT
CONVERTS ENERGY FROM ONE FORM TO ANOTHER
FORM.
ENERGY TRANSMISION CAN BE ELECTRICAL
, MECHANICAL , CHEMICAL B, OPTICAL , THERMAL
, NUCLEAR , ACOUSTICAL OR A COMBINATION OF ANY
TWO OR MORE .
IT IS OFTEN VERY CONVENIENT TO MAKE
MEASUREMENTS IN TERMS OF ELECTRICAL QUANTITIES
SUCH AS VOLTAGE OR CURRENT AND EASE IN
3. PIEZOELECTRIC PRESSURE
TRANSDUCERS
• THESE DEVICE UTILIZE THE PIEZOELECTRIC
CHARACTERISTICS OF CERTAIN CRYSTALLINE
AND CERAMIC MATERIALS (SUCH AS QUARTZ) TO
GENERATE AN ELECTRICAL SIGNAL.
4. PRINCIPLE
WHEN PRESSURE IS APPLIED ON CRYSTAL , AN ELECTRICAL
CHARGE IS GENERATED.
SOME OF THE PIEZOELECTRIC MATERIALS ARE BARRIUM
TITANATE SINTERED POWDER , CRYSTAL OF QUARTZ ,
TOURMALINE, AND ROCHELLE SALTS.
5. CONSTRUCTION AND WORKING
oCONSTRUCTION
IT CONSISTS OF A DIAPHRAGM BY WHICH PRESSURE IS
TRANSMITTED TO THE PIEZOELECTRIC CRYSTAL Y1. THIS
CRYSTAL GENERATES AN ELECTRICAL SIGNAL WHICH IS
AMPLIFIED BY A CHARGE AMPLIFIER.
A 2ND PIEZOELECTRIC CRYSTAL Y2 IS INCLUDED TO COMPENSATE
6. APPLICATIONS
PRESSURE SENSOR IN THE TOUCH PADS OF MOBILE
PHONES.
TO MEASURE PRESSURE INSIDE THE CYLINDER OF
GASOLINE ENGINE.
IN VARIOUS APPLICATION SUCH AS MEDICAL
,AEROSPACE , NUCLEAR INSTRUMENTATION.
7. ADVANTAGES
I. THE TRANSDUCER NEEDS NO EXTERNAL POWER AND IS
THEREFORE SELF GENERATING.
II. IT HAS A VERY GOOD HIGH FREQUENCY RESPONSE.
III. THOUGH PIEZOELECTRIC SENSORS ARE
ELECTROMECHANICAL SYSTEMS THAT REACT
TO COMPRESSION , THE SENSING ELEMENTS SHOW
ALMOST ZERO DEFLECTION.
8. DISADVANTAGES
I. THIS TYPE OF TRANSDUCER CANNOT MEASURE STATIC
PRESSURE.
II. THE OUTPUT OF THE TRANSDUCER IS AFFECTED BY
CHANGES IN TEMPERATURE. THEREFORE
TEMPERATURE COMPENSATING DEVICES HAS TO BE
USED.
