Subelement G: Inspections, Installations and Instruments— Topic :
Question 49G1
Element 9 (GMDSS Maintainer)A 4 digit multi-meter with an accuracy of 0.15% and 2 counts is set on the 6 volt scale. What range of readings may be expected when measuring a 5 volt DC source?
Explanation
To determine the range of expected readings, we need to calculate the total measurement error based on the multimeter's specifications.
1. **Calculate the percentage error:** The meter has an accuracy of 0.15% of the reading.
0.15% of 5 V = 0.0015 * 5 V = 0.0075 V.
2. **Calculate the "counts" error:** A 4-digit multimeter on a 6-volt scale means its resolution for that scale is typically 0.001 V (e.g., it displays 5.000 V). "2 counts" means an additional error of two units of this least significant digit.
2 counts = 2 * 0.001 V = 0.002 V.
3. **Calculate the total absolute error:** Add the percentage error and the counts error.
Total error = 0.0075 V + 0.002 V = 0.0095 V.
4. **Determine the range:** Subtract and add the total error to the nominal 5 V reading.
Lower bound: 5 V - 0.0095 V = 4.9905 V
Upper bound: 5 V + 0.0095 V = 5.0095 V
Rounding these values to two decimal places (as typical for such a reading or options), the expected range is approximately 4.99 V to 5.01 V. This corresponds to option A.
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