Abstract: The invention relates to an apparatus for the calibration of a thermometer in situ, wherein the apparatus has a temperature sensor (S) for determining a temperature (T); wherein a reference element (K) is provided for calibrating the temperature sensor (S); wherein the reference element (K) at least partially comprises a ferroelectric material (D), which experiences a phase transformation at least one predetermined temperature (TPh) in a temperature range relevant for calibrating the temperature sensor (S).

Abstract: A resistance temperature sensor with a first temperature sensor element and a second temperature sensor element, wherein the first temperature sensor element comprises a first measuring path and the second temperature sensor element a second measuring path, wherein the first and the second measuring paths extend on a substrate, wherein the substrate has an anisotropic thermal expansion with at least two mutually differing expansion directions (a, c), and wherein a projection of the first measuring path on the expansion directions (a) differs from a projection of the second measuring path on the expansion directions (c).

Abstract: A gas analyzer for continuously determining the concentration of a gas in a gas mixture, having a measuring cell, a radiation source, a detector and signal processing facilities, characterized in that the radiation source is slidingly arranged in the measuring cell.