Inertial sensors

One focus of the R&D activities at Fraunhofer ENAS is the development of high-precision MEMS angular rate sensors. Angular rate sensors are inertial sensors, which can measure angular velocity without an external reference. They are also known as gyroscopes. The challenge for the development of these micromechanical systems is to achieve the target requirements for extremely low noise and low drift. The system itself consists of a micromechanical structure that transforms the angular velocity into a capacitance change. This is read out by an analog front-end electronics. In the shown example of a high precision gyroscope, the analog mixed signal IC and the MEMS element are integrated in a ceramic package. The ASIC is responsible for the excitation of the MEMS, the demodulation of the angular velocity and the signal conditioning. It also serves as an interface for the next higher system level. Typical parameters of the angular rate sensor are:

• Angular rate range ± 450 °/s
• Resolution 5 °/h = 14 mdps (milli degrees per second)
• In-run bias stability < 1 °/h
• Angle random walk (noise) < 0.03 °/√h (0.00043 °/s/√Hz)
• Operating temperature range from -40 °C to 85 °C
• Sensitive to rotation rates around the z-axis (Yaw)
• Digital SPI interface