= Measurement indication
A \b[measurement indication] is the value supplied by a <measurement instrument> or <measuring system>. It may appear as a pointer position, displayed number, printed output or transmitted code. The indication and the corresponding <measurand> value need not be values of the same kind of quantity.<International vocabulary of metrology by JCGM>[VIM3entry4.1, definition and notes1–2]{ref}
For an original mechanical readout, suppose the indicated pointer position is a <length> $z$, related to input <pressure> $p$ by
$$
z=Sp+z_0,\qquad S=0.20\,\mathrm{mm\,kPa^{-1}},\quad z_0=1.00\,\mathrm{mm}.
$$
The <measurement indication> $z=21.00\,\mathrm{mm}$ then corresponds to $p=(z-z_0)/S=100.0\,\mathrm{kPa}$ under this <measurement model>. The position is observable; the pressure value is inferred using the response relation. A printed pressure scale could carry out part of that conversion physically without changing the underlying distinction.
If the pointer position is uncertain by $0.10\,\mathrm{mm}$, that contribution corresponds to $0.50\,\mathrm{kPa}$ in this stipulated linear model. Uncertainty in the zero $z_0$, <transducer sensitivity> $S$, temperature response and <instrumental drift> can add further contributions. Closely spaced scale markings therefore do not establish the total <measurement uncertainty>.
Record the original indication and instrument settings when applying corrections. A corrected <measured quantity value> can change after improved <measurement calibration> even though the recorded indication remains the same. For example, revising the assumed zero from $1.00$ to $1.20\,\mathrm{mm}$ changes the inferred pressure from $100.0$ to $99.0\,\mathrm{kPa}$. The complete <measurement result> accompanies the inferred value with its uncertainty and relevant conditions; the raw <measurement indication> alone cannot supply that information.
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