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High-accuracy motion sensor

STMicroelectronics’ AIS226DS motion sensor is a two-axis in-plane accelerometer and senses acceleration up to ±6g, where one ‘g’ is the acceleration due to gravity. Motion is sensed using a tiny MEMS motion detector built on a silicon chip. An integrated interface chip, available with an SPI or I2C output, enables direct connection to the vehicle’s ECU (electronic control unit). Samples of the new sensor are available from distributor Rutronik. Functions like accurate measurements of vehicle movement for systems such as adaptive front lights, auto-levelling HID (high-intensity discharge) lamps, inertial brake lights, e-parking brake, advanced anti-theft systems and control of vehicle dynamics benefit from the new device. The ability to recognise tiny angles of incline, smaller than 0.02 degrees is important in auto-levelling lamp, e-parking brake, and (hill start aid) applications.

Other vehicle systems that can use the sensor include event recorders for monitoring accidents or abusive driving, and GPS navigation systems using movement data for improved dead reckoning when the satellite signal is lost. There are also many non-automotive applications, such as vibration sensing in industrial equipment, black-box security monitors for shipping containers, inclinometers, and robotic systems. The low intrinsic noise of the electronic interface chip allows usable converter resolution of 14bits over a significant bandwidth, corresponding to a resolution of 0.25mg (on 2g full-scale). The sensor is also highly stable and maintains high accuracy (±70mg) throughout the automotive temperature range –40 to +105°C, offering offset drift in the range of 0.2mg/°C. The AIS226DS, assembled in a sturdy SO16W full-molded package, is qualified to the AEC-Q100 automotive quality standard.