Magnetometers are used to measure or monitor mechanical stress in ferromagnetic materials. Mechanical stress will improve alignment of magnetic domains in microscopic scale that will raise the magnetic field measured close to the material by magnetometers. There are different hypothesis about stress-magnetisation relationship. However the effect of mechanical stress on measured magnetic field near the specimen is claimed to be proven in many scientific publications. There have been efforts to solve the inverse problem of magnetisation-stress resolution in order to quantify the stress based on measured magnetic field.