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A reading taken near the bottom of a digital voltmeter's range is less accurate in percentage terms because

  • A.the integrating period is shortened automatically at small inputs
  • B.the fixed count term becomes a large fraction of the reading
  • C.the input impedance falls as the range is made more sensitive
  • D.the resolution of the display worsens at small readings

Answer: B

Three counts on a reading of 1900 is a sixth of one per cent; the same three counts on a reading of 100 is three per cent. The remedy is to select a lower range so that the reading sits high in it, which is exactly what auto-ranging achieves.

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