On the calibration of magnetometers having electromagnets with the help of cylindrical nickel reference samples

In order to avoid the great effort required in tracing back the indication of a magnetometer directly to SI units, reference samples are usually applied. In the case of magnetometers with iron cores, this procedure is accompanied by several problems influencing the accuracy. The problems connected with the measurement of the properties of the reference sample in the standards laboratory are basically the same but are more difficult due to the higher accuracy required. These error-producing factors and how to avoid their influence were studied. The calibration of nickel reference samples was carried out with a relative uncertainty of 0.15% (σ₁). Certain precautions being observed, the subsequent calibration procedure in laboratories using these samples should be possible with a relative uncertainty of 0.5%