Signal Conditioning for Electronic Instrumentation

AC Bridges

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MCT 3332 : Instrumentation and Measurements

Dr. Hazlina Md YusofDepartment of Mechatronics EngineeringInternational Islamic University Malaysia

Analog Signal ConditioningAC Bridges

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• Used to measure inductance and capacitances

• Applied in communication systems and complex electronic circuits

- Used for shifting phase, providing feedback paths for oscillators or amplifiers, filtering out undesired signals and measuring the frequency of audio signals

• Operates on balanced condition - Reactance and resistive components are balanced

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Analog Signal ConditioningAC Bridges

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Analog Signal ConditioningAC Bridges

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Analog Signal ConditioningAC Bridges

Example 7

An AC bridge is in balance with the following constants: arm AB, R = 200 Ω in series with L = 15.9 mH R; arm BC, R = 300 Ω in series with C = 0.265 μF; arm CD, unknown; arm DA, = 450 Ω. The oscillator frequency is 1 kHz. Find the constants of arm CD.

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Analog Signal ConditioningAC Bridges

Capacitance Comparison Bridge

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- -j j

a.k.a. Similar Angle Bridge

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Capacitance Comparison BridgeExample 8 A similar angle bridge is used to measure a

capacitive impedance at a frequency of 2kHz. The bridge constant at balance areC3 =100F R1=10k

R2=50k R3=100k

Find the equivalent series circuit of the unknown impedance

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Analog Signal ConditioningAC Bridges

Inductance Comparison Bridge

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Analog Signal ConditioningAC BridgesMaxwell Bridge

Quality factor, Q = ( Lx ) / Rx = C1 R1

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Analog Signal ConditioningAC Bridges Hay Bridge

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Analog Signal ConditioningAC Bridges Hay Bridge

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Analog Signal ConditioningAC BridgesSchering Bridge

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Analog Signal ConditioningAC BridgesSchering Bridge

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Analog Signal ConditioningAC BridgesWien Bridge

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Analog Signal ConditioningAC Bridges Wagner Ground

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Analog Signal ConditioningAC Bridges

ENDS