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DC Metrology
11 questions By Tony R. Kuphaldt
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Question 10 of 11
What technology is currently regarded as state-of-the-art for reproducing the standard ohm?
Reveal answerThe voltage standard used to be based on a specified length of special wire, but not anymore!
Notes:Questions like this will never become obsolete, even though the answer may. At the time of this writing (August 2003), the internationally recognized technology for the standard volt is based on a quantum phenomenon known as the Quantum Hall Effect.
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Question 11 of 11
Calibration laboratories often make reference to Test Uncertainty Ratios (TUR’s), normally holding to a ratio of 4:1 or more when performing calibration work on instruments. What does this figure mean?
Reveal answerThe “Test Uncertainty Ratio” refers to how much more precise the calibrating instrument is compared to the instrument being calibrated.
Notes:While your students may never have to calculate TUR’s, it is still important for them to know what the general principle is. If any of them experience difficulty understanding the concept, ask them if it makes any sense to use a ruler to check the calibration of a micrometer, or to use a wristwatch to check the long-term stability of a laboratory-grade chronograph.
