The CAL01 reference magnet provides a stable and convenient method to verify the accuracy and calibration of the USB 2510x series magnetometers. The CAL01 reference magnet is composed of two axially magnetized permanent magnet rings that allow a probe to access the working region of the fixture from both axial and transverse orientations, making the calibration fixture useful for both axial and transverse probe calibration. Unlike conventional reference magnets that rely on placing a probe in a fixed position, which produce an error if the magnet hole is improperly sized orthe probe is not shimmed correctly, the CAL01 is designed so that magnet can be moved with respect to the probe in order to allow the user to find the positive and negative peak magnetic field values, which are used to compute the calibration factors. When used in combination with MultiDimension’s graphical data logging user interface, this technique minimizes errors from probe misalignment and permits rapid accurate calibration of the USB2510x magnetometer probes. The plots below show the peak field values when moving an axial probe through the axial hole and when rotating the magnet around a transverse probe in the transverse hole.