Measurement of Temperature by Mach-Zehnder Interferometry

Abstract

This paper is intended to bridge the present gap in publications on the subject between the very simple illustrative paper and the detailed account that can be understood only by an expert. An outline of the types of problem that can be tackled with a Mach-Zehnder interferometer is followed by a discussion of the principle of formation of interference fringes in two-beam interferometry and an account of the principle of operation of the Mach-Zehnder interferometer. The relations between fringe shift and temperature change are derived for liquids and for gases at constant pressure and the factors that control the sensitivity are indicated. A description is given of the operations to be performed to produce fringes and some attention is given to practical details of the instrument and associated apparatus. The methods of analysing interferograms, including the use made of white-light fringes when measuring absolute temperatures are described, and some attention is given to sources of error. After an account of the application of the interferometer to temperature measurement in convective heat transfer systems, illustrated by examples from steady state and transient processes, the advantages of the instrument over other methods of temperature measurement for some problems are discussed briefly.