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In order to study acoustic waves in liquid Helium or for cryogenic acoustic microscopy, it is necessary to match the very low impedance of the liquid to the impedance of the transducer. One way to do it, is to deposit on the solid one or several quarter-wave layers at the interface with the liquid. In order to measure this transmission, we have constructed an alignment system for 9-10 GHz longitudinal sound waves in a quartz rod at 1.5 K. It allows us to deduce accurately the effective transmission in liquid Helium from the acoustic impedance, the sound velocity and the damping of the waves in the films.

The purpose of this paper is to give a practical account of how low-cost microprocessor instrumentation can aid the measurement of energy-related physical quantities. As the subject matter is of a technical nature, a specific example is given of a simple windspeed and windpower measuring and logging instrument, based on the Rockwell AIM 65 Advanced Interactive Microcomputer.