UM7 Orientation Sensor

Overview

The UM7 orientation sensor from is a third-generation Attitude and Heading Reference System (AHRS) from Redshift Labs that 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 features an onboard microcontroller that combines sensor data using a sophisticated Extended Kalman Filter (EKF) to generate orientation estimates 500 times a second
Two versions of the UM7 are available: the UM7 orientation sensor, which includes an enclosure, and the UM7-LT, which does not. The two versions are functionally equivalent, and both include a cable.

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 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. Additional cable assemblies for the expansion headers are not included.

Features

Sensors and processing

• Manufactured in the USA, in a facility that complies with the AS9100 Aerospace Management System
• 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 serial interface software

Communication

• 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 Redshift 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

• UM7-LT (no enclosure):
  • Dimensions: 1.06″ × 1.02″ × 0.26″ (27 mm × 26 mm × 6.5 mm)
  • Weight: 0.12 oz (3.5 g) without cable

• UM7 (with enclosure):
  • Dimensions: 1.09″ × 1.12″ × 0.37″ (28 mm × 28 × 9 mm) without mounting tabs
  • Weight: 0.26 oz (7.5 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)

Specs:

• Voltage Input Range: 5 to 15V
• Operating Temperature Rating: -40° to +60°C
• Storage Temperature Rating: -45 to +85°C
• Weight: 15g
• Power Min/Max (5 ports): 0.5 to 1.75 W
• Size: 1.75″x1.75″

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

Note: The main UART pins, TX and RX, are 5V-tolerant and can be used directly with 5 V systems that are guaranteed to read 3.3 V as high. The secondary UART and some of the SPI pins are NOT 5V-tolerant.

Downloads

• UM7 Datasheet (1MB pdf)
  Datasheet for the UM7 orientation sensor, revision 1.8 (released July 30, 2018).
• Redshift Serial Interface Software (77MB zip)
  
• Version 3.1.5. The Serial Interface makes it easy to plot data in real-time, log data, and set configuration registers on the UM7 product line. Any Redshift Labs / CH Robotics device that communicates using the CHR binary serial protocol can be controlled using the Serial Interface.
• AN1005 – Understanding Euler Angles (255k pdf)
• AN1006 – Understanding Quaternions (57k pdf)
• AN1007 – Estimating Velocity and Position Using Accelerometers (43k pdf)
• AN1008 – Sensors for Orientation Estimation (127k pdf) 
• Example Matlab communication code (4k zip)
• Mounting hole locations for the new UM7 enclosure released September 2021 (15k zip)
  This DWG drawing shows the locations of the mounting holes on the bottom side of the UM7 enclosure. The holes are threaded for M1.4 screws, and we recommend screwing no more than 3 mm (0.12″) into the mounting holes.
  Note: this drawing is only applicable to UM7 units (product #2764) with the updated enclosure design that began shipping in September 2021.

What’s Included?

• UM7 Orientation Sensor
• (Optional USB Expansion Board)
• (Optional Cables)
  • 5-Pin cables (1-sided)
  • 5-Pin cables (2-sided)
  • 6-Pin cables (1-sided)
  • 6-Pin cables (2-sided)
• (Optional Enclosures)
  • Top Enclosures
  • Bottom Enclosures