VMX-pi onboard orientation sensors require calibration in order to yield optimal results. We highly recommend taking the time to understand this calibration process – successful calibration is vital to ensure optimal performance.

Careful and accurate Magnetometer Calibration is crucial in order to yield valid compass heading, 9-axis heading and magnetic disturbance detection.

Magnetometer Calibration is not typically required for use in many robotics applications, including Field-oriented drive.  Magnetometer Calibration is a manual process and is recommended for advanced users who need to calculate absolute heading.

Calibration Process

The magnetometer calibration encompasses three areas: (a) hard-iron calibration, (b) soft-iron calibration and (c) magnetic disturbance calibration.

Hard and soft-iron calibration allows the following equation to be used, and corrects for hard and soft-iron effects due to nearby ferrous metals and magnetic fields. This calibration is necessary in order to achieve valid compass heading readings:

In addition, using the same calibration data the strength of the Earth’s Magnetic Field is determined. Whenever the data from the magnetometer indicates the current magnetic field differs from the calibrated Earth’s Magnetic Field strength by more than the “Magnetic Disturbance Ratio”, a Magnetic Anomaly is declared.

Therefore, careful and accurate Magnetometer Calibration is crucial in order to yield valid compass heading, 9-axis heading and magnetic disturbance detection.

Magnetometer Calibration can be accomplished with a single, simple calibration process through the use of the Magnetometer Calibration tool. This tool is designed to run on a Windows computer, and communicate to the VMX-pi circuit board via a USB cable.