Feeler device for measuring surface roughness

A feeler device for measuring the degree of roughness of an uneven surface 8 being examined, characterized by comprising:

• a transmitting transducer 11 arranged to convert an electric signal of a predetermined frequency into an ultrasonic wave propagated through a liquid coupling medium and having a wavelength of the same order of magnitude as said unevenness;
• a generator 13 arranged to generate said electric signal and feeding said transmitting transducer 11;
• a receiving transducer 12 arranged to receive the ultrasonic wave reflected by said examined surface 8;
• a support head 15 for said transmitting transducer 11 and receiving transducer 12, said head 15 comprising a base surface 16 to be rested on said examined surface 8, and said transducers 11, 12 being housed in such a manner that the respective transmitting and receiving directions define two coplanar lines which converge at said base surface and which form the same angle with this latter;
• and
• processing means 14 connected to said transmitting transducer 11 and to said receiving transducer 12, and providing an indication of the phase difference between the ultrasonic signals respectively transmitted and received by said transducers when said base surface 16 of said head 15 rests on said examined surface 8.