Electrochemical machining tool assembly

An electrochemical machining tool assembly comprising:

• at least one electrode adapted to machine a workpiece across a gap upon application of a potential difference ΔV across said electrode and the workpiece;
• means for flowing an electrolyte through the gap and for flushing the electrolyte from the gap;
• means for feeding said at least one electrode toward the workpiece;
• at least one ultrasonic sensor adapted to direct an ultrasonic wave toward a surface of said electrode and to receive a reflected ultrasonic wave from the surface of said electrode, the reflected ultrasonic wave comprising a plurality of reflected waves from the surface of said electrode and from a surface of the workpiece;
• and
• a delay generator adapted to delay the excitation of said ultrasonic sensor a dwell time Td after a reduction of the potential difference ΔV across said electrode and the workpiece occurs.