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Electronics Engineering QUESTION #11739
Question 1
A frequency counter displays $1.000\,003\,\text{MHz}$ for a $1\,\text{MHz}$ reference signal. The measurement error in ppm is:
  • $3\,\text{ppm}$✔️
  • $0.3\,\text{ppm}$
  • $30\,\text{ppm}$
  • $0.003\,\text{ppm}$
Correct Answer Explanation
Error $= \dfrac{|f_{measured} - f_{actual}|}{f_{actual}} \times 10^6 = \dfrac{1.000003 - 1.000000}{1.000000} \times 10^6 = 3 \times 10^{-6} \times 10^6 = \mathbf{3\,\text{ppm}}$. This ppm (parts per million) figure characterises oscillator and counter accuracy. TCXO stability is typically 0.5–2.5 ppm; OCXO provides < 0.01 ppm.