When magnetic sheet material is bent, shaped, or otherwise processed into a closed magnetic path, the measured result may no longer represent the undeformed material alone. That is why single-sheet testing is so valuable: it allows engineers to evaluate the magnetic material in its original flat state before further processing introduces shape-dependent effects.

Traditional magnetic characterization often required a closed magnetic loop, such as a ring specimen or Epstein frame arrangement. IWATSU’s patented Single Sheet Tester addresses that limitation by allowing direct measurement of a small flat sample without first converting it into a closed-loop core.

Why This Matters

The IWATSU Single Sheet Tester helps reveal magnetic property changes that can arise purely from sample shape and processing, even when the base material is the same. This makes it especially useful for material development, incoming inspection, and process optimization, where engineers want to evaluate the material itself before machining or forming affects the result.

For sheet-shaped samples whose magnetic properties depend on shape, it is important to evaluate the undeformed sheet.

Example: Same Material, Different Shape, Different Result

A useful example is the comparative measurement of a 0.1 t × 5.0 W × 107 L Permalloy band using the IWATSU B-H Analyzer SY-8218. The same material was measured after being formed into circular and oval shapes at 100 Hz and a fixed magnetic field of 200 A/m.

Figure 1. Example of flat magnetic material formed into an oval shape before measurement.

The results show that sample shape can influence magnetic performance even when the material itself is unchanged:

• Coercive force (Hc): Round = Oval
• Residual magnetic flux density (Br): Round < Oval
• Saturation magnetic flux density (Bm): Round < Oval
• Core loss: Round < Oval

Figure 2. Comparative B-H plots for the same flat material formed into circular and oval shapes.

In other words, Hc remained essentially the same, while Br, Bm, and core loss changed with specimen shape. This shows that geometry and processing can influence the final magnetic behavior, even when the base material is identical.

The example demonstrates why single-sheet testing before machining or forming is important: it provides a clearer view of the material in its original state and helps avoid overlooking shape-dependent performance differences.

How Single-Sheet Measurement Is Performed with the B-H Analyzer

The IWATSU Single Sheet Tester works together with the B-H Analyzer to measure small flat specimens directly, without first reshaping them into a closed-loop core. This allows engineers to evaluate magnetic properties on undeformed sheet material in a practical and repeatable way.

The system includes two essential B coils, which support different sample widths while keeping the measurement approach consistent:

• B Coil 01: for samples up to 1 mm thickness and up to 10 mm width
• B Coil 02: for samples up to 1 mm thickness and up to 30 mm width

By selecting the appropriate coil for the sample size, users can insert a flat specimen into the Single Sheet Tester and perform magnetic characterization with the IWATSU B-H Analyzer without the additional preparation steps required by conventional closed-loop methods.

Figure 3. Overview of the IWATSU Single Sheet Tester and the included B coils.

B Coil 01

B Coil 01 is intended for narrow samples up to 10 mm wide and up to 1 mm thick. It is well suited for comparative evaluation of smaller strip specimens, helping users maintain controlled and repeatable sample geometry during testing.

Figure 4. B Coil 01 for samples up to 1 mm thickness and up to 10 mm width.

B Coil 02

B Coil 02 supports wider flat specimens up to 30 mm wide and up to 1 mm thick. This expands the practical measurement range for sheet materials while preserving the same direct single-sheet testing principle.

Figure 5. B Coil 02 for samples up to 1 mm thickness and up to 30 mm width.

Together, these included coils make the Single Sheet Tester practical for a broader range of flat magnetic samples and help users compare like-for-like specimens before shaping, punching, winding, or other downstream processing steps take place.

Directional Evaluation

The Single Sheet Tester is also useful for evaluating directional specimens. If directionality is to be examined, prepare a sample of 30 mm × 30 mm. By changing the installation direction of the sample relative to the yoke to 0° and 90°, it becomes possible to compare differences in the magnetic properties of the same sample caused by directionality.

This is valuable for materials in which rolling direction or internal structure affects magnetic performance.

Best Practices for Comparative Single-Sheet Testing

To obtain meaningful and repeatable comparisons between different samples, the measurement setup should be kept as consistent as possible:

• Use samples with the same width, length, and thickness.
• Keep the contact position between the yoke and sample the same.
• Check whether there is any difference between measuring the front and back of the sample, and if so, always measure the same side.
• Keep the slider pressure that presses the sample against the yoke measurement surface constant.

Conclusion

The IWATSU Single Sheet Tester gives engineers a practical way to evaluate magnetic sheet materials before they are altered by forming or machining. The Permalloy example makes this clear: even when the base material is the same, changing the specimen shape can affect Br, Bm, and core loss.

With the included B Coil 01 and B Coil 02, the system supports direct single-sheet measurement across a useful range of flat sample sizes. For material development, incoming inspection, and process optimization, this provides insight that can otherwise be hidden once the specimen has been reshaped.

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IWATSU Single Sheet Test System