Definition of a frequency counter: A frequency counter is a digital circuit that measures and displays the frequency of an input signal by counting cycles over a known time base. Evaluate this definition for correctness.
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ACorrect
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BIncorrect
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COnly correct for sine waves
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DOnly correct when duty cycle is 50%
Answer
Correct Answer: Correct
Explanation
Introduction / Context:Frequency counters are ubiquitous test instruments in labs and embedded systems. They rely on precise time bases to translate counts of periodic events into a frequency value that can be displayed numerically.
Given Data / Assumptions:
- The input signal is periodic with a frequency in the counter’s operating range.
- A stable reference oscillator defines the measurement gate time.
- Input conditioning circuitry shapes the signal to logic levels so edges can be counted reliably.
Concept / Approach:By counting the number of input cycles N within a gate interval T_gate, the instrument computes f ≈ N / T_gate. Alternatively, some counters measure the period and invert it, which improves resolution at low frequencies (reciprocal counting). Both approaches fulfill the stated definition.
Step-by-Step Solution:
Shape the input signal to clean digital transitions.Open the measurement gate for a precise interval T_gate.Count the input edges during this interval to obtain N.Compute frequency as f_meas = N / T_gate and display the result.Verification / Alternative check:Datasheets for bench frequency counters and MCU-based counters outline exactly this method, sometimes adding averaging, prescalers, or reciprocal techniques for improved resolution.
Why Other Options Are Wrong:
Incorrect: Denies standard instrument operation.Only correct for sine waves / duty-cycle-dependent: Frequency counting works for any periodic waveform with clean edges.Common Pitfalls:Measuring noisy or non-periodic signals; inadequate input conditioning causing false counts; relying on short gate times that magnify quantization error.
Final Answer:Correct