A Comparison of Methods for Calibration and Use of Multi-component Strain Gauge Wind Tunnel Balances (Comparaison de Methodes d'Etalonnage et d'Utilisation des Balances Extensometriques de Soufflerie a Plusieurs Composantes)

摘要

A method is presented for calibration of strain-gauge balances which does not require that the components can be loaded independently. Applicable to both 'internal' and 'external' types of balance, the procedure uses a single varying calibration load to determine all linear and non-linear calibration coefficients. Constant 'secondary' loads on one or more components are unnecessary, although they may be used if desired. The usual iterative solution of the second order balance equations is outlined, and an approximate non-iterative scheme is included for completeness, though not recommended. Two methods of accounting for dependency of the calibration coefficients on the signs of the component loads are presented. A concept of 'buoyancy' is introduced to simplify the application of force balance tares, and a procedure for determining the component outputs for absolute zero load (the 'buoyant' offsets) is given. Balance data at a series of model attitudes are used to define these offsets, and also the coefficients in the equations defining the component load distribution of the tare weight at any attitude. The topics covered are ideally suited to formulation and solution by matrix methods, which have been used throughout. (Author)