Overview
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.
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UM7-LT orientation sensor, bottom view. |
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Cable included with the UM7-LT orientation sensor. |
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Product Comparison
We carry several inertial measurement and orientation sensors. The table below compares their capabilities:
Features
Sensors and processing
- Excellent gyro bias stability over temperature
- Adjustable low-pass filter and EKF settings provide customizable performance for various applications
- States and sensor data synchronized to GPS position and velocity using optional external GPS module
- Allows for alignment calibration and third-order bias and scale factor temperature compensation for accelerometers, gyros, and magnetometer
- Magnetometer soft and hard-iron calibration can be performed through the CHR serial interface software
Communication
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CHR Serial Interface. |
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Graph of quaternions displayed by the CHR Serial Interface connected to a UM7-LT orientation sensor. |
- Output data:
- Attitude and heading (Euler angles)
- Attitude quaternion
- magnetometer, accelerometer, gyro data
- GPS altitude, position, velocity (with optional external GPS)
- 3.3 V TTL serial interface (UART) with baud rates up to 921,600 bps can stream data or provide updates on request
- Note: the main UART pins, TX, and RX, are 5V-tolerant and can be directly connected to 5 V systems that are guaranteed to read 3.3 V as high
- Transmits data using human-readable NMEA strings (up to 100 Hz broadcast), binary packets for higher efficiency (up to 255 Hz broadcast), or a combination of both
- Flexible communication architecture allows UM7 to transmit any combination of data at individually adjustable rates
- Connects to the CHR Serial Interface software to allow for real-time plotting of sensor data, logging, device configuration, and magnetometer calibration
- SPI interface available through expansion connector
Specifications
- Dimensions: 1.06 × 1.02 × 0.26 (27 mm × 26 mm × 6.5 mm)
- Weight: 0.12 oz (3.5 g) without cable
- Operating voltage: 4 V to 5.5 V
- I/O logic level: 3.3 V (with 5V-tolerant main UART pins, TX and RX)
Attitude and heading
- EKF estimation rate: 500 Hz
- 1° typical static pitch/roll accuracy
- 3° typical dynamic pitch/roll accuracy
- 3° typical static yaw accuracy
- 5° typical dynamic yaw accuracy
- 0.5° angle repeatability
- 0.01° angular resolution