Magnetism—an Influencing Factor on Weighing

Weighing magnetic materials or magnetizable tare vessels or samples may destabilize the weight result or compromise repeatability. For example, when weighing a sample or vessel containing iron, steel, cobalt, or nickel, users may see the following effects: Weight values are stable, but non-repeatable. Different values are displayed, depending on the position of the sample on the weighing pan.

These effects may be from one of two causes:
1. If the material to be weighed is magnetized, such as a stirring rod of a magnetic stirrer, the weight force of the sample is superseded by the attractive force its magnetic field exerts on the magnetizable parts of the weighing chamber or weighing cell.
2. If the weighing cell is designed on the electromagnetic force compensation principle, a strong magnet is used in this system. Despite careful shielding measures of the magnet, the balance is surrounded by a low residual magnetic field, and this residual field can influence the weighing result if interaction occurs with the sample or vessel.

The white paper describes:

• Types of influences and the possibilities to recognize them in daily use of the balance
• Practical instructions on how the influence of magnetism can be avoided or reduced
• Measures provided by the manufacturer in high-resolution balances
• Innovative and effective solutions use weighing pans, sample holders, and parts inside the draft shield, made from the non-magnetic and non-corrosive titanium