= Thermometer calibration
<Thermometer> calibration compares an instrument's response with assigned reference <temperatures> under specified conditions. In a proposed two-reference procedure, thermalize the sensing part at $T_0$ and $T_1$, record responses $X_0$ and $X_1$, and, only if a linear response is justified over that interval, use
$$
T(X)=T_0+(T_1-T_0)\frac{X-X_0}{X_1-X_0}.
$$
Additional reference <temperatures> test curvature; returning to the first reference tests drift. A <gas thermometer> instead obtains its response from an <equation of state>, with a reference and corrections for its apparatus. In either case, uncertainty in the reference propagates to the inferred <temperature>. Calibration determines the response relation; it cannot by itself remove the finite-sample disturbance or incomplete <thermal equilibrium> described in <thermometer>. A reference established on a practical scale can also differ slightly from true <thermodynamic temperature>; the BIPM distinguishes the International Temperature Scale of 1990 readings from their thermodynamic counterparts.<The International System of Units (SI), ninth edition, SI Brochure>[section 2.3.1: practical and thermodynamic temperature]{ref}
Back to article page
