Epstein / Single-sheet Magnetic Tester

Selection criteria

Frequency range, induction range, measurement uncertainty.

Supply chain

Epstein and single-sheet testers are a small, specialised field led by German makers such as Brockhaus, used by steel mills, stamping houses and motor labs. A motor maker's own tester is useful for incoming-coil checks and for comparing grades from different mills.

Buyer FAQ

What does an electrical-steel tester measure?

Core loss (W/kg) and magnetic polarisation or permeability at set flux densities and frequencies, using an Epstein frame or a single-sheet tester. These numbers decide whether a coil meets its grade.

Epstein frame or single-sheet tester?

The Epstein frame (IEC 60404-2) is the reference method used on mill certificates. Single-sheet testers (IEC 60404-3) are faster and need smaller samples, so they are common for incoming inspection; results are close but not identical.

Should motor makers test incoming steel?

Large users do, at least on new suppliers and periodically. Others rely on the mill certificate plus a periodic third-party test, and check that stamping and annealing have not degraded the cores.

Where it is used