MEMS rate sensor from Murata features stable thermal performance and high reliability for accurate dead-reckoning

22nd November 2010
ES Admin
Murata has launched a MEMS rate sensor (gyro) which features excellent performance characteristics for the automotive market. The device, part number MEV-50C-R, supports accurate dead-reckoning performance for car navigation devices, but is also aimed at GPS modules, satellite antennas and other applications such as toys, including for example a high performance radio control helicopter. This sensor features the second-generation of Murata's technology - the first generation was used in Murata's famous bicycle-riding robot, MURATA BOY, and Murata's unicycle-riding robot, MURATA GIRL.
Excellent temperature drift performance makes signal processing easy - there is no need to adjust for temperature drift in software. Temperature drift across the entire operating range, -40 to 85degC, is just 0.6 deg/s. Materials used in the construction of the rate sensor help to ensure the stable temperature performance of the device. Single-crystal silicon is used for the core MEMS vibrator, while the MEMS element is composed of silicon and pyrex glass, which have very similar temperature expansion coefficients, increasing stability.

Another key factor for rate sensors used in car navigation systems is the start-up drift. It typically takes several minutes after the system is switched on for a GPS signal to be acquired, so dead-reckoning is commonly used during this time. The MEV-50C-R exhibits particularly impressive start-up drift; just 0.1 deg/s between 0.5s and 5 minutes after start-up.

High linearity (0.5% across the operating range of angular velocity) and low cross-axis sensitivity (+/-5%) make it possible to follow even the most winding roads as the sensor output follows the change of angular rate precisely.

The MEMS element uses anodic bonding creating a seal which achieves much better performance than the current industry standard of 10-9 Pa m3/s. The seal did not change its efficiency during air tank/heat shock tests with 2000 cycles of -55 to +125°C (30 min/30 min). This high level of seal allows Murata's MEMS technology to be applied under harsh conditions such as automotive.

The MEV-50C-R measures 10.0 x 6.2 x 2.9mm and weighs just 0.3g (maximum). Maximum angular velocity is ±70deg/s. The sensor's unique 'ladder' structure means the part is not influenced by external physical noise (shock or vibration), and thus exhibits more accurate angular-rate information than competing parts.

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