= Pressure gauge temperature error
\b[Pressure gauge temperature error] is the change in a gauge's indication error associated with a change from its specified temperature conditions, while the pressure comparison is otherwise controlled. It belongs to the complete <Bourdon tube pressure gauge> response, not merely the number of scale divisions. Distinguish an instrument-temperature effect from a real change in the pressure being measured.
A concrete manufacturer specification is WIKA's June2025 US data sheet, which gives an additional error bound of $\pm0.4\%$ of span per $10\,\mathrm K$ departure from the $20\,{}^{\circ}\mathrm C$ reference.<Bourdon Tube Pressure Gauges, Stainless Steel Series by WIKA>[23X.50,06/2025, p1, Temperature error]{ref} This is a version-specific bound; it is not a measured signed correction for an individual gauge.
For an original gauge with span $P_{\rm span}=1\,\mathrm{MPa}$ at $40\,{}^{\circ}\mathrm C$, the specified form gives
$$
B_T=0.004P_{\rm span}\frac{|40-20|}{10}
=0.008P_{\rm span}=8\,\mathrm{kPa}.
$$
At a pressure reading of $100\,\mathrm{kPa}$, that bound is $8\%$ of the reading. The percentage is referenced to span, so the same absolute bound represents a larger relative contribution near the bottom of the range. Without the sign and an appropriate <measurement calibration>, subtracting $8\,\mathrm{kPa}$ would not be justified.
For an original controlled comparison, hold reference pressure at $400\,\mathrm{kPa}$ and allow the gauge assembly to equilibrate first at $20$ and then at $40\,{}^{\circ}\mathrm C$. Suppose indications are $401$ and $407\,\mathrm{kPa}$. Their errors relative to the reference are $1$ and $7\,\mathrm{kPa}$, so the observed temperature-associated change is $6\,\mathrm{kPa}$, or a local average $0.3\,\mathrm{kPa\,K^{-1}}$. These are illustrative readings, not manufacturer test results. Repeat at other pressures and on return to the reference temperature to check reversibility and <hysteresis>.
Record gauge and reference conditions, equilibration and uncertainty in the pressure comparison. Heating a sealed gas can change its actual pressure through the <ideal gas law>; an uncontrolled change of that kind cannot be assigned entirely to instrument error. The bound or fitted correction remains one contribution to the final <measurement uncertainty>.
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