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VARIABLE CAPACITIVE TRANSDUCER. MR. VISHAL VASISTHA ASSISTANT PROFESSOR (ME) DCE, GURGAON. VARIABLE CAPACITIVE TRANSDUCER. A variable capacitor is a capacitor whose capacitance may be changed Capacitance of two plate capacitor is given by C=KA / t
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VARIABLE CAPACITIVE TRANSDUCER MR. VISHAL VASISTHA ASSISTANT PROFESSOR (ME) DCE, GURGAON
VARIABLE CAPACITIVE TRANSDUCER • A variable capacitor is a capacitor whose capacitance may be changed • Capacitance of two plate capacitor is given by C=KA / t A change in anyone of K, A, t may be used in sensing process • Variable capacitance is used to convert physical phenomena into electrical signals
TYPES OF VCT • CAPACITIVE ROTATION TYPE • CAPACITIVE DISPLACEMENT/PRESSURE TYPE • CAPACITIVE LIQUID LEVEL TYPE
CAPACITIVE ROTATION TYPE • Angular displacement of one of the plates causes change in effective AREA
CAPACITIVE DISPLACEMENT/ PRESSURE TYPE • Displacement of one of the plates changes x (distance between plates)
CAPACITIVE LIQUID LEVEL TYPE • A change in K (depends on dielectric properties of medium between two plates) is produced as the fluid level between the capacitor plate changes
TYPES OF VCT Rotary plate capacitor Thin diaphragm Linear Capacitance Transducer
APPLICATIONS • To tune a radio as tuning capacitors, or antenna tuners
APPLICATIONS • Capacitance microphone • Capacitive Liquid level sensor • Pressure transducer
CAPACITANCE BRIDGE CIRCUIT Compensator Z1 Sensor Z2 AC Excitation Bridge Output vo v vref + Z3 Z4 Bridge Completion