Reference Block No.2 (DIN EN ISO 9934-2) – is a self-contained unit requiring no external magnetic field induction. It is used to determine the quality of the magnetic particle suspensions. The block consists of 2 soft iron bars, separated by a thin (15 μm) Al-foil, representing an artificial defect. Permanent magnets are placed at the sample ends.
Because of the permanent magnetic field the bars get magnetized and magnetic particles accumulate over the artificial defect forming indication lines. The quality of the suspension or dry powder is determined by the summarized length of the lines.