For measuring the frequency of an unknown A.C. source. Which of the following device is necessary to obtain a standard waveform?

Explanation:

Measuring the Frequency of an Unknown A.C. Source

Definition: To measure the frequency of an unknown A.C. (Alternating Current) source, it is crucial to obtain a standard waveform for accurate analysis. The device that plays a key role in this process must have the ability to process the signal and provide a clean, consistent waveform representation. Among the options provided, the correct choice is the operational amplifier, which is essential for waveform shaping and processing in frequency measurement applications.

Working Principle:

An operational amplifier (op-amp) is an electronic device that amplifies the difference between two input voltages. It has a high input impedance, low output impedance, and high gain, making it ideal for signal conditioning, filtering, and waveform generation. In the context of frequency measurement, the op-amp can be used to clean up the input signal, remove noise, and produce a standard waveform (e.g., a sine wave or square wave) that can be analyzed to determine its frequency.

The op-amp is often used in conjunction with other components (resistors, capacitors, etc.) to create circuits like oscillators, filters, and waveform generators, which are critical for frequency measurement. By shaping the input signal into a standard waveform, the op-amp ensures accurate and reliable frequency analysis.

Advantages of Using an Operational Amplifier for Frequency Measurement:

• Signal Conditioning: The op-amp can amplify weak signals and remove unwanted noise, ensuring a clean waveform for analysis.
• Waveform Shaping: It can transform irregular input signals into standard waveforms (e.g., sine or square waves), which are easier to analyze for frequency.
• High Accuracy: The precision of an op-amp ensures accurate frequency measurement, even for signals with low amplitude or high noise levels.
• Versatility: Op-amps can be used in a wide range of applications, from simple filters to complex oscillators, making them a versatile tool for frequency measurement.

Applications of Op-Amps in Frequency Measurement:

• Used in frequency counters to condition and process the input signal.
• Implemented in waveform generators to produce standard waveforms for calibration and testing.
• Employed in phase-locked loops (PLLs) to synchronize and measure frequencies accurately.

Correct Option Analysis:

The correct option is:

Option 1: Operational amplifier

The operational amplifier is essential for obtaining a standard waveform from an unknown A.C. source. It amplifies, conditions, and shapes the input signal, ensuring accurate frequency measurement. Without an op-amp or a similar signal-conditioning device, it would be challenging to analyze noisy or irregular signals effectively.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 2: Astable Multivibrator

An astable multivibrator is a circuit that generates a continuous oscillating signal, typically in the form of a square wave. While it is useful for generating waveforms, it is not suitable for directly measuring the frequency of an unknown A.C. source. The astable multivibrator does not process or condition the input signal; instead, it produces its own oscillating output, which is unrelated to the input frequency.

Option 3: Schmitt Trigger

A Schmitt trigger is a comparator circuit with hysteresis, often used to convert a noisy or irregular signal into a clean square wave. While it can be helpful for waveform shaping, it is not ideal for obtaining a standard waveform for frequency measurement. The Schmitt trigger is better suited for digital signal processing applications, where binary signals are required.

Option 4: Monostable Multivibrator

A monostable multivibrator generates a single output pulse in response to an input trigger signal. While it can be used in timing and pulse generation applications, it is not suitable for continuous frequency measurement. The monostable multivibrator does not provide a standard waveform for analyzing an unknown A.C. source’s frequency.

Conclusion:

In conclusion, the operational amplifier is the most appropriate choice for measuring the frequency of an unknown A.C. source. Its ability to amplify, condition, and shape the input signal makes it indispensable for obtaining a standard waveform, which is crucial for accurate frequency analysis. The other options, while useful in specific applications, do not provide the necessary functionality for this purpose. Understanding the roles of different devices in signal processing and frequency measurement is essential for selecting the right tool for the task.