The development and operational aspects of a signal transfer system for use in wind tunnel propeller models

This paper describes a Signal Transfer System (STS) for use in a wind tunnel model propeller. In order to extend the capacity of a conventional mechanical slip ring assembly an electronic multiplexer has been developed, which is located in the rotating part of a propeller-hub. The amplified transducer signals are multiplexed, digitised and transferred over the slip ring assembly located in the propeller shaft. A demultiplexer unit processes the signals in order to make them available, in analogue format, for a wind tunnel data acquisition system. NLR has developed the STS for use in a specific Wind Tunnel model propeller. Due to space limitations in the model a slip ring assembly had to be applied, which had an insufficient number of slip rings to transfer all signals directly. Two STS have been successfully operated with two model propellers, throughout a number of tests in several European wind tunnels. Special attention has been paid to the operational aspects of the system. A brief overview is presented for a future development resulting in a fully contact-less transfer system, replacing mechanical slip ring assemblies