Signal Conditioning Circuit

AC Sensor Signal Conditioning Circuit

This project demonstrates the design and implementation of a signal conditioning circuit using 741 operational amplifiers. The system processes a low-level AC signal from a sensor by amplifying, filtering, and rectifying it to produce a stable DC output. Through careful design, the circuit ensures noise elimination and signal standardization while maintaining fidelity, making it suitable for automation and instrumentation applications.

Aims and Objectives

Amplify low-level signals: Process a sensor signal of 8112 Hz at 1 μA.
Noise filtration: Remove unwanted 50 Hz noise at 2 μA.
Signal rectification: Convert AC to DC while preserving the signal’s fidelity.
Output standardization: Generate a stable 5 V DC output.

Amplification Stages

Two-stage inverting amplifier using 741 op-amps.
First stage amplifies with a gain of 100, followed by a second stage with a gain of 20, adhering to good engineering practice by limiting gain per stage to reduce distortion.

Active Bandpass Filter

Designed using Analog Filter Wizard, configured for a stopband frequency of 30 kHz and a passband frequency of 5 kHz.
Removes the amplified 50 Hz noise effectively.

Signal Rectification

Utilizes Texas Instruments' recommended op-amp configuration to convert the original AC signal into a unipolar positive AC signal.

Low-Pass Filtering

A passive low-pass filter smooths the positive AC signal into a stable DC level.

Output Level Adjustment

A two-stage inverting amplifier ensures the final signal is conditioned to a 5 V DC output.

Conclusion

This project effectively employs 741 op-amps to design a multi-stage signal conditioning circuit. The output signal, processed through amplification, filtering, and rectification, achieves a stable DC level with minimal ripple. The small ripple, caused by real-world component imperfections, remains within an acceptable range for practical applications. This highlights the robustness of the design and its suitability for instrumentation and automation tasks requiring reliable signal processing.

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