A measurement procedure describes in sufficient detail how a measurement is performed, including its measurement method, measurement model and the calculations that produce a measurement result. The VIM notes that the description usually enables an operator to carry out the measurement and can include a target measurement uncertainty.[ref] Naming an instrument or writing a final equation alone leaves much of this operational description unspecified.
Consider an original procedure for the resistance measuring system described above. Specify the test resistor and temperature, the two-terminal lead arrangement, source current, readout settings and settling time. Record the measured or assigned current with its measurement uncertainty. First replace the test resistor by a short whose resistance is negligible in the chosen model, and record indication . Insert the test resistor without changing the declared lead configuration, allow the specified settling interval and record . Repeating the short reading after the sample reading helps check stability.
Assume the current , lead resistance and additive readout offset remain common to the paired readings. Thenso the procedure's calculation isFor stipulated , and , this gives . The paired measurement removes the common lead and zero contributions under the stated model.
The sequence matters because those contributions can change. If the readout offset rises by between the short and sample readings, the same calculation is shifted by . This is an original instrumental drift example, not observed equipment performance.
Document which operations are repeated, how corrections are obtained, how deviations are handled and which uncertainty contributions remain. The procedure turns the apparatus and model into a repeatable set of operations; it does not make the supplied references, stability assumptions or recorded values exact.
Articles by others on the same topic
There are currently no matching articles.