Which instrument is specifically designed to directly measure the frequency of a periodic waveform with high accuracy and display it as a numerical value?

Introduction:
While many instruments can imply frequency, only certain devices are optimized to measure and display it numerically with precision. This question distinguishes between general-purpose tools and dedicated frequency-measurement instruments.

Given Data / Assumptions:

• Periodic input signal of unknown frequency.
• Desire for direct numerical readout.
• Standard lab instruments available.

Concept / Approach:
A frequency meter/counter counts cycles or zero-crossings over a gate time, computes frequency f = counts / gate_time, and displays the result. Oscilloscopes can estimate frequency by measuring period from the trace, but that method is less precise and more user-dependent. Signal generators produce signals; they are not measurement devices for unknown signals.

Step-by-Step Solution:
1) Feed the unknown periodic signal into the counter's input with proper conditioning.2) The counter uses a stable timebase (crystal oscillator) to define gate intervals.3) It tallies cycles within the gate and computes the frequency in Hz.4) The display shows a direct numeric frequency readout.

Verification / Alternative check:
Comparing the counter's readout with an oscilloscope timebase measurement typically shows the counter's higher precision and stability, especially for high or very low frequencies.

Why Other Options Are Wrong:
Oscilloscope: visual tool; frequency is inferred, not directly measured numerically (unless the scope has a built-in counter function).Audio/RF generators: sources, not measurement devices.

Common Pitfalls:
Relying solely on scope graticule for precision measurements where a counter would be more accurate.

Final Answer:
frequency meter or counter