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Revolution AV Electronic Compass Gets Upgrades

Bias correction and GPS ground speed added to firmware for increased accuracy

(Maynard, MA), April 15, 2016 – True North has added an innovative bias correction algorithm to their Revolution AV compass. The software improves accuracy by combining data from two different inclination sensors: a liquid-filled 2-axis electrolytic sensor (eTilt) and a 3-axis MEMS accelerometer. The eTilt sensor has very stable offsets compared to the MEMS accelerometer, while the accelerometer has greater range and better accuracy at high inclination. Better overall accuracy is achieved by using the difference between eTilt and MEMS measurements near level to calculate corrected MEMS offsets. Corrections are then applied over the full range of MEMS measurements.

In other accuracy news, the Revolution AV will now accept and parse the NMEA GPS $GPRMC sentence. It will utilize the data from both ground speed and magnetic variation fields.  If present, variation is used to calculate true heading. Ground speed is used to correct the Y-axis inclination measurement to remove the effect of centripetal acceleration when circling.  This results in a significant improvement for roll angle estimation, especially when circling for longer than 10 to 15 seconds. Ground speed updates can be accepted as fast as the baud rate allows. A timer can be configured to reset the correction if updates stop.

The Revolution AV is an electronic compass that features a sensor suite which includes precision 3-axis MEMS rotation, rate, acceleration, and magnetic sensors and a dual-axis electrolytic tilt sensor (for the ultimate in near-level accuracy). All 11 sensor measurements are calibrated over a -50°C to 110°C temperature range and are aligned in three dimensions.  In addition to azimuth output, all raw and calibrated measurements are available at up to 28 readings per second. Rate gyro measurements rotated to the inertial frame of reference are also available.  The recommended applications for the Revolution AV are manned and unmanned aerial and underwater vehicles, robotics, weather buoys, antenna positioning, platform stabilization, excavation machinery, and irrigation equipment.

True North Technologies develops and manufactures sensing products for marine, air, and land-based applications with concentrations in electronic navigation and downhole instrumentation. The 20-year-old company is located in historic Clock Tower Place in Maynard, MA.