Resonance Based Force Measurement: Prelude to High-Resolution Anemometry for Liquid Metal Flows

This paper describes the first phase of a two-part project designed to develop a new anemometry method for use in high temperature liquid metal flows. The device will incorporate a dual-cantilever, PZT-driven touch sensor housed within a sealed, temperature resistant ceramic Pitot tube. Due to differing cantilever lengths, the device’s unloaded spectral response exhibits two distinct peaks, each corresponding to the cantilevers’ resonant frequencies. The principal of operation is based on the fact that pressure-induced forces on each cantilever produce resonant frequency shifts which can then be correlated with applied pressures. The first project phase has focused on development and testing of the dual cantilever touch-sensor and its supporting electronics. Two new concepts have been introduced in designing the touch sensor — use of a dual cantilever for simultaneous force measurement, and simultaneous detection of associated pressure-induced resonant frequency shifts. Here, we describe design of the Pitot tube, design and fabrication of the dual-cantilever sensor and electronics, and system modeling of the sensor. We also outline two pressure measurement schemes; in the first, pressure is correlated with resonant frequency shifts at constant phase while in the second, pressure is related to phase shifts (between forcing and response signals) at constant frequency. Device driving and sensing electronics have been fabricated as has the dual-cantilever touch sensor; preliminary experimental measurements of single and dual forces are presented.