The NG-1000 – Micro Vickers and Knoop Hardness tester can convert your Vickers value to HRA, HRC, HR15N, HR30N, HR45N, and HB. An alternative to the Vickers approach is the Knoop method. The two approaches are different from one another in the following ways:

The Vickers diamond indenter penetrates the specimen twice as deep as the Knoop diamond indenter with the same test load. The Knoop method is particularly useful for testing very thin layers because of its tiny indentation depth (e.g. aluminum foil).
The Knoop method is best used with small, longish test specimens because of the long and thin (elongated) test indent, whereas the Vickers method is preferable for small, spherical specimens (square indentation).
The Vickers indentation might result in cracking when evaluating exceptionally hard and brittle materials (glass, ceramics), hence the Knoop method is best for these materials (measurement accuracy).

Given that the Knoop diagonal (the longitudinal diagonal) is around three times longer for any given indentation depth than the arithmetic mean of the Vickers diagonals, the Knoop method offers superior measurement precision, particularly when used in conjunction with extremely light test loads.

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