There are many factors that must be corrected or eliminated in order to obtain correct weighing results. Air buoyancy is an example of an influence that may be corrected. Magnetic influences cannot easily be corrected and so must be minimized. We have developed a novel device for determining both the magnetic susceptibility of materials and the presence of residual magnetization.

Device for measuring magnetic susceptibility: here a diamagnetic sample (Cu) is being tested

An advantage of this device is that it can operate effectively while subjecting stainless steel 1 kg mass standards to a magnetic induction of less than 1 mT. If increased uncertainty can be tolerated, then it is possible to measure the susceptibility of mass standards as small as 1 g, as shown in the following graph.

These are the results of a comparison carried out among four European laboratories and the BIPM. The bars represent the expanded uncertainty (95 % confidence limit) claimed by each participant.