Physically, all the sensors’ axes are oriented in the same direction. The Accelerometer and Magnetometer axes are:
And the gyro’s rotational frame of reference is:
The IMU produces data in the following units:
| Accelerometer | Magnetometer | Gyroscope |
| mg (Milli G) | μT (Microtesla) | mdps (Milli Degrees Per Second) |
Note that by default (if resting on a flat surface), the Accelerometer’s Z access is negative and around -1000 mg, this is because the gravity of the planet is constantly accelerating the sensor towards its centre (downwards). If you flip the block over, this value should become positive. The 1K measurement (1000mg = 1G Earth Gravity) indicates there sensor is constantly falling at around 1G (9.8 m/s²). In ideal conditions, the Z access should display -1000mg, the difference in values you may observe are due to noise in the data, the location on the planet’s surface and calibration of the sensor.
Sampling Rates
The available sampling rates or, how often data is collected from the sensors, are 1Hz, 10Hz, 25Hz, 50Hz, 100Hz and 200Hz. Please note that values at data rates above 25Hz are automatically averaged and sent at a maximum data rate of 30Hz (30 updates per second). This means that even if you select a 200Hz data rate, the readings will be calculated and presented to you at a much lower rate.
To change the sampling rate of an IMU just open the Properties Panel by clicking on the ‘gear’ icon:
In the ‘Custom Settings’ sections choose the desire Sampling Rate from the drop-down menu and press ‘Save’ to apply the changes.
