The UM7-LT orientation sensor from CH Robotics is an Attitude and Heading Reference System (AHRS) that contains a three-axis accelerometer, rate gyro, and magnetometer. It combines this data using an Extended Kalman Filter to produce attitude and heading estimates.
As of July 18, 2014, we are shipping UM7-LT modules with the latest firmware version, U71C. Boards that shipped before this date have older firmware versions (U71A or U71B) with issues that might prevent correct operation of the SPI bus and/or cause a steady angular drift in the outputs of the UM7 in certain circumstances (due to improper EKF initialization). The firmware version can be checked with the CHR Serial Interface software. If you purchased a UM7-LT with older firmware from us and these issues are affecting you, please contact us for firmware upgrade instructions.
The UM7-LT orientation sensor from CH Robotics produces attitude and heading estimates from triaxial accelerometer, rate gyro, and magnetometer data. Unlike a typical inertial measurement unit (IMU), which only provides raw sensor readings, the UM7 is a complete Attitude and Heading Reference System, or AHRS: its onboard microcontroller combines sensor data using an Extended Kalman Filter (EKF) to generate orientation estimates 500 times a second.
The UM7 features a number of improvements over its predecessor, the UM6, including higher gyro bias stability and lower noise, a new communication architecture for improved flexibility, optional NMEA packet transmission, UTC time-synchronization with external GPS, and support for third-order temperature compensation on all sensors. It takes advantage of newer MEMS (micro-electro-mechanical systems) technology that allows it to offer better performance at a lower price.
Connections for power and TTL serial communication can be made to the UM7-LT through a polarized five-pin male connector on one side, which mates with an included cable assembly. A pair of six-pin expansion headers on the other side of the board provide additional connectivity options, including an alternative SPI interface and a secondary serial interface that can be connected to an external GPS module (like our LS20031 GPS receiver). Additional cable assemblies for the expansion headers are not included.
We carry several inertial measurement and orientation sensors. The table below compares their capabilities:
Sensors and processing
Attitude and heading
In this video playlist, Caleb Chamberlain from CH Robotics shows how to get started with the UM7, configure its communication settings, and calibrate its magnetometer.