What determines a frequency counter’s accuracy? The overall accuracy of a digital frequency counter is primarily determined by which factor?

Introduction / Context:
Frequency counters measure cycles against a reference timebase. Two quality aspects matter: accuracy (how close to the true value) and resolution/precision (how finely it can read). This question asks specifically about accuracy.

Given Data / Assumptions:

• Counters use a crystal-controlled or disciplined oscillator as the system clock/timebase.
• Gate time (sampling interval) can be adjusted for resolution.
• Display formatting does not change the underlying measurement truth.

Concept / Approach:
Accuracy depends on the timebase frequency and its stability (tolerance, aging, temperature coefficient). If the oscillator runs 10 ppm high, every measurement will read about 10 ppm high, regardless of how long you count. Longer sampling intervals improve resolution but do not fix timebase error.

Step-by-Step Solution:

Verification / Alternative check:
High-accuracy counters use OCXO/TCXO or GPS-disciplined references; switching to a better reference tightens absolute accuracy without changing sampling rate.

Why Other Options Are Wrong:

• Number of digits: Cosmetic; shows resolution, not accuracy.
• Sampling rate: Affects resolution/precision, not absolute accuracy.
• Display update rate: User interface choice with no impact on correctness.

Common Pitfalls:
Confusing precise (many digits, stable reading) with accurate (correct). A long, stable reading with a poor timebase is precisely wrong.

Final Answer:
system clock frequency.