A probe, connectable to a machine tool, having an electric generator (16), supplying an electric or electronic circuit (22) with electric power, and a driving element (28), capable of relative rotation with respect to the stator of the electric generator. The rotation axis of the driving element is preferably a symmetry axis of the probe itself. The driving element is not connected to any external energy source, and can be set in rotation simply by activating the rotary axis of the machine tool.Advantageously, the driving element of the present invention is not directly connected with any mobile element of the machine tool, but is either rotatably mounted on the probe itself, or fixed on the reference table of the machine tool. Importantly, the inventive probe requires no additional connections to the machine tool on which it is mounted, besides the connection to the rotary spindle, which can be realized with a conventional tool-holder with a standardised tapered shank. In this way the inventive probe is fully compatible with standard probes, and can be mounted and used with standard tool-holders, without any adaptation. The self-powering function of the probe can be activated simply by sending appropriate rotation instructions to the machine tools.