Vorrichtung zum zerstoerungsfreien Messen der Dicke einer Haerteschicht

In order to provide a device for the non-destructive testing of the thickness (7) of a hardness layer (6) for polycrystalline materials by means of ultrasound using a coupling piece (3) serving as a mount for a transmit and receive converter (1) held at about a constant distance to the surface (9) of the workpiece to be tested in order to ensure reliable and unambiguous display of the current hardness depth even if the device is used in constant operation under operating conditions involving heat and dirt, the coupling piece (3) is designed with an aperture (10) extending from the transmit and/or receive surface (12) of the converter (1) in the direction of the sound (11) onto the surface (9) of the workpiece (4) and a further aperture (14) which extends in mirror image to the first aperature (10) in relation to a standard (13) erected onto the central impinging point of the surface (9) comprising a flat bottom (16) arranged perpendicular to the direction of extension (15).