• Progress and developing velocity of the crack are electrically obtained.
• Applicable to both ﬂat and curved surfaces.
• Resistance change vs crack length is virtually linear.
• Dedicated adapter enables use of a conventional strain ampliﬁer.
• Extremely simple and convenient compared with the conventional optical method.
• Allows 2 trigger wires each in front of and behind the grid (KV-5C) to be used for automation of measurement.