PAALS: precision accelerometer alignment and leveling system

A description is given of the precision accelerometer alignment and leveling system (PAALS), a high-performance microcontroller-corrected accelerometer triad that outputs acceleration (ft/s²) via MIL-STD-1553BN communications. Combined tight-packaging, high-reliability, and high-performance requirements were the main design drivers. The key system elements are QA-700 Accelerometers, an Intel 80C 196 microcontroller, custom digital ASIC (application-specific integrated circuit), custom hybrid, and dual redundant MIL-STD-1533B communication components. For high performance, the QA-700 accelerometers are thermally modeled (third-order) for bias, scale factor, and alignment. The hybrid (three digitizers) is thermally modeled (third-order) for scale factor and offset, as well as input linearity. Extensive FDIRR (fault detection, indication, reporting, and recording) has been incorporated for supportability and maintainability