The Berthhold Penetrameter

This field indicator contains two artificial discontinuities at 90° to one another. There is a sensitivity adjustment consisting of a cover plate which can be turned to one of four setting which vary the distance of the cover plate and detecting media from the artificial discontinuities; the greater the gap, the higher the field strength necessary to render the lines visible.

They are used in a manner similar to the ASME indicator, the instrument should be rotated to find the field direction. An alternative collective term for penetrameters, e.g. ASME, Berthold, Castrol Type 3 is a ‘pie gauge’.

Fig. 8.4 - Berthold Penetrameter initially developed in 1938 at Reich Roentgenstelle in Berlin – Dahlem (Germany)