So what qualifies an Inertial Measurement Unit (IMU) as "Tactical Grade?" The qualifying metric for IMU grading is the In Run Bias Stability (IRBS) in their gyroscopes, which represents its stability during benign conditions, which include the following: ideal integration (averaging) time, stable temperature, no inertial motion. Yole Development classifies IMUs as "Tactical Grade" when their gyroscope's IRBS is in between 0.5 deg/hour and 5 deg/hour.
IEEE-STD-952-1997 (Appendix B) provides an industry-standard definition of IRBS, which defines it as the minima on the Allan Variance curve. The following graphic identifies the Allan Variance representation of a population of ADIS16490 IMUs. In this case, the parameter is defined as the sum of the mean and one standard deviation, which means that 67% of ADIS16490 units will perform at this level, or better.
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