A method of measuring the thickness of a biological tissue by ultrasounds and a device carrying out such method. The apparatus comprises a sensor system and an icing condition detector. A plurality of delay sensing circuits having slightly overlapping operating ranges and different centers of operation are connected in parallel with respect to a an input clock signal, which is passed through the delay sensing circuits. Each foot tread member second end is operatively associated with a glide member for moveable coupling of the second end of each foot tread member to a support surface. Thus, the terminal main body, the overcurrent breaking element, and the wire are integrally provided.