Fluidic angular rate sensor null error compensation

Abstract

In a fluidic angular rate sensor in which a pair of temperature sensitive resistive elements are differentially cooled by a jet of fluid, the direction of which lags the position of the resistive elements when the rate sensor is rotated in the plane of sensitivity, undesired, long term errors that result in the lack of a zero null (when the unit is not undergoing any angular rate) are compensated for by introducing a voltage equal to the zero-rate null offset, determined with the velocity of the fluid jet reduced to a point below which it has any appreciable effect on the sensing bridge (simulating static conditions), together with an input to the bridge to offset its output so that the static null offset to be usable to compensate the dynamic null offset (that is, the offset in the null determined with the fluid jet in full operation). In one embodiment, the bridge is offset during the static null error determination, thereby to offset the stored, null error; in another embodiment, the bridge is offset during operation, but not during the static null determination, so the offset and the static null error together compensate for the dynamic null error. The fluid jet may simply be reduced, and not completely stopped, thereby to avoid static laminar conditions and pressure differentials in the static fluid resulting from accelerations; or, the fluid jet may be completely eliminated during the compensating null voltage generation procedure.