= Measurement procedure
A \b[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>.<International vocabulary of metrology by JCGM>[VIM3entry2.6, definition and notes1–2]{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 $V_s$. Insert the test resistor without changing the declared lead configuration, allow the specified settling interval and record $V_x$. Repeating the short reading after the sample reading helps check stability.
Assume the current $I$, lead resistance $R_L$ and additive readout offset $V_0$ remain common to the paired readings. Then
$$
V_s=IR_L+V_0,\qquad
V_x=I(R_x+R_L)+V_0,
$$
so the procedure's calculation is
$$
R_x=\frac{V_x-V_s}{I}.
$$
For stipulated $V_s=3\,\mathrm{mV}$, $V_x=103\,\mathrm{mV}$ and $I=1\,\mathrm{mA}$, this gives $100\,\Omega$. 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 $0.5\,\mathrm{mV}$ between the short and sample readings, the same calculation is shifted by $0.5\,\mathrm{mV}/(1\,\mathrm{mA})=0.5\,\Omega$. 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.
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