OpenTag is an Arduino-compatible open-source inertial measurement unit (IMU) for recording high speed motion sensor data to a removable microSD memory card.  OpenTag uses a rechargeable lithium polymer battery so you can reuse it unlike other data storage tags.



  • 3D Accelerometer
  • 3D Magnetometer
  • 3D Gyroscope
  • Pressure (depth)
  • Temperature


  • Dive behavior
  • Pitch, roll, yaw
  • Bioenergetics: ODBA and VDBA
  • Fluke rate
  • Feeding behavior


The rechargeable lithium battery will run OpenTag continuously for 7 days with all sensors.  Longer run times are possible.  Run 1 month with the accelerometer and magnetometer sampling at 10 Hz and the gyroscope turned off.

Sampling rates are set from the OpenTag Windows software and loaded from a script file on the memory card. IMU sensors can run at 100 Hz simultaneously. Higher sample rates are possible on individual sensors.

OpenTag integrates a small aluminum housing with an o-ring to allow access to the memory card, recharge the battery, and the power switch.


Depth rating: 300 m

Dimensions: 10.5 x 4.7 x 2.2 cm

Weight: 110 g in air

Power: Rechargeable lithium polymer battery


3D Gyroscope: Measures rotational velocity. Use with accelerometer and magnetometer for accurate measurement of 3D motion.
3D Accelerometer: Digital accelerometer for motion and tilt sensing
3D Magnetometer: Measures magnetic field strength for compass orientation

Pressure: 0.5 cm depth resolution to 300 m
Temperature: -40 to 85 C +/- 0.5C. Resolution 0.015 C



OpenTag Setup (Windows) Script file generator

otAHRS OpenTag MATLAB software to calculate pitch, roll, and yaw