Improved uncertainty evaluation for a long distance measurement by means of a temperature sensor network

Abstract

The aim of the research described in this paper was to more accurately determine the measurement uncertainty of an interferometric long distance measurement. The chosen method was to install a temperature sensor network in the laboratory to measure in more detail the ambient temperature profile to more accurately determine the local values of the refractive index on the path travelled by the laser light. The experimental measurements were supplemented by a theoretical analysis of the mathematical model being used. The outcome of the performed work was that the claimed measurement uncertainty of the distance measurement, which is based on using only 5 temperature sensors, was justified. However, if in the future a lower uncertainty would be needed, a sensor network like the one that was temporarily installed would be needed. During the measurement campaign an offset in the mean temperature of 0.2 °C was found, which was equal to the maximum allowed bias in view of the claimed uncertainty for the long distance measurement. At a more general level, it was concluded that such sensor networks provide a useful new tool to increase the understanding of other measurements, to validate assumptions and optimize existing measurements.