Tiny cube packs three gyros, three accelerometers, and more
By Margery Conner, Technical Editor -- EDN, June 11, 2007
IMUs (inertial-measurement units) rely on a combination of accelerometers and gyros to measure acceleration and rotational change and to calculate position and motion. Typically finding use in aircraft and missiles, IMUs usually measure several inches along a side and have prices starting in the thousands of dollars—and that’s before you add in the complex calibration procedure of their internal sensors. In contrast, the ADIS16355 IMU, a new member of Analog Devices’ iSensor family, measures less than 0.75 in.3 and costs $359 (1000). It incorporates three MEMS (microelectromechanical-system)-based gyros and three MEMS-based accelerometers to provide three axes of angular-rate sensing and three axes of acceleration sensing and thus 6DOF (6°-of-freedom) motion measurement.
An important system-integration cost for IMUs is their calibration for temperature and motion, often requiring expensive and complicated testing on 3-D, rotating calibration platforms. The ADIS16355 undergoes calibration at the factory, in which operators program the calibration coefficients into each unit through its SPI (serial-peripheral interface). This step allows designers to integrate the IMUs into their system with no additional temperature or motion calibration. The ADIS16355 includes full-temperature-range calibration, with a bias-temperature stability of 0.005°/sec/°C; the ADIS16350 version provides a room-temperature calibration with a bias-temperature stability of 0.03°/sec/°C and costs $275 (1000).
