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Tech Talk




ADI's MEMS Magic


Tactical grade MEMS gyroscope rivals fiber optic gyroscopes on performance with significantly smaller size, lighter weight and less power consumption

I had the pleasure to talk with Bob Scannell, Business Development Manager, MEMS/Sensors Technology Group for Analog Devices. He told me about the company's new tactical grade sensors for high performance inertial measurement. In Europe, Analog Devices accounts for about one fifth of the company's worldwide revenues and worldwide work force. The company has a manufacturing facility in Limerick, Ireland, and design and development centres in Denmark, England, Finland, Scotland, Slovakia, Spain and Ireland. European client references include main telecom equipment manufacturers Alcatel, Ericsson and Nokia-Siemens Networks, automotive systems manufacturers such as Autoliv, Bosch and Continental, consumer references such as Harman and Philips, and a variety of industrial clients including ABB, Agilent Technologies, Siemens and Rohde & Schwarz.

Analog Devices, Inc. (ADI) released for general availability the ADIS16136 tactical grade iSensor® digital MEMS gyroscope, which provides 3.5o/hr typical bias stability in a matchbox-sized module consuming less than 1 watt and weighing only 25 grams. The new tactical grade (below 10o/hr bias stability) iSensor MEMS gyroscope operates autonomously and requires no user configuration before producing precise and accurate rate sensing data, quickly enabling precision dependent applications such as platform stabilization and control, navigation, robotics, and medical instrumentation. Bob explained, "The ADIS16136 MEMS gyro is competitive on the stability and angular random walk specifications compared to more costly fiber optic gyros, while demonstrating 2X better linearity, 30X faster start-up, and 5X lower power. Even more significant is the ADIS16136 gyro's small size (~1 cubic inch) and low weight of only 25 grams. This is minute by comparison to fiber optic gyros, which can be 10 cubic-inches or larger and will enable many new applications for precision angular rate sensing."

This ADIS16136 is optimized for dynamic performance by combining industry leading iMEMS® technology with ADI's proven signal conditioning expertise. The ADIS16136 provides data at rates of up to 2048 SPS (samples per second) and offers an averaging/decimation filter structure for optimizing noise/bandwidth trade-offs. The serial peripheral interface (SPI) and user register structure provide easy access to configuration controls and calibrated sensor data for embedded processor platforms. Full device-specific calibration over temperature drives the internal compensation resulting in highly stable sensor output with no additional test or characterization required. The available wide bandwidth of 380 Hz provides significant advantage to complex stabilization applications. The new gyro ships in a 36 mm × 44 mm × 14 mm package. Four holes are provided for simple mechanical attachment with a standard 24-pin, dual row, 1-mm-pitch connector that supports electrical attachment to a printed circuit board or cable system. Operating temperature range is ?40°C to +85°C.

Analog Devices, Inc. (ADI) also released the third generation iSensor® MEMS IMU (inertial measurement unit). The ADIS16488 is a tactical grade 10-degree-of-freedom (DoF) sensor and integrates a tri-axis gyroscope, tri-axis accelerometer, tri-axis magnetometer and a pressure sensor into a single package. This new MEMS IMU provides the most stable and complete integrated sensor suite available, supporting mission critical requirements in high-performance navigation and stabilization applications. Beyond the important tactical grade (below 10o/hr) bias stability, the ADIS16488 outperforms all other contemporary gyro/IMU offerings on the often more critical specifications of g-effect, temperature coefficient, and bandwidth by up to 100X. Further, the new iSensor MEMS IMU even outperforms legacy military grade IMUs on vibration rectification and linearity. Every device undergoes unique and extensive factory calibration, resulting in unparalleled precision in the toughest environments and greatly reduced complexity, time, cost, and design risk relative to typical motion sensor development. Bob continued, "For industrial, military, and medical equipment designers who require the most accurate detection and control of motion in order to stabilize or navigate their applications, the ADIS16488 tactical grade IMU offers performance levels previously only available to those with unlimited budgets. With equal or better performance to legacy high-end IMUs on key measures such as bias stability and angular random walk, the ADIS16488 provides better performance on the often more critical parameters of vibration-rectification, linearity, and bandwidth while consuming one-quarter the power, and at one-tenth the cost."

The ADIS16488 iSensor 10-DoF MEMS IMU is a complete inertial measurement system that combines ADI's high performance iMEMS technology and sensor-signal processing expertise to optimize the IMU's 10-DoF dynamic performance. Operation is fully autonomous, including all embedded compensations, with valid data available from the SPI interface 500 ms after applying power. With all calibration done at the factory, and with an ADI Blackfin® processor-powered configurable interface for tuning embedded filtering and other diagnostics, a major source of design integration time and risk is virtually eliminated. ADIS16488 iSensor 10-DoF MEMS IMU Key Specifications

  • Gyro bias in-run dtability: 6o/hr
  • Gyro dynamic range: 450°/s
  • Gyro angular random walk: 0.3 deg/rt-hr
  • Gyro noise : 0.005 o/sec/?Hz rms
  • Non-linearity: 0.01 %
  • Bias temperature coefficient: 0.0025o/s/oC
  • Sensitivity temperature coefficient: 35 ppm/oC
  • Accelerometer in-run stability:100 micro-g
  • Accelerometer dynamic range: 18g
  • X/Y/Z alignment accuracy: 0.05o
  • Bandwidth: 330Hz
  • Magnetometer dynamic range +/- 3.5 gauss
  • Barometer dynamic range 10 to 1200 mbar
The ADIS16488 uses the same footprint and connector system as ADI's ADIS16375, which greatly simplifies the upgrade process. www.analog.com


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