A device (10) for detecting deformations in solids includes an insertable casing (11) with inner dividing wall (20) and lower (26) and upper enclosed sections (24) filled with fluid (36 and 34). A first strain-sensing system (38), and a second strain-sensing system (42) are disposed in the lower and an upper enclosed systems respectively. A valve (18) couples the second strain-sensing system to the lower enclosed section (26) and is normally closed. The valve is constructed to open in response to a signal sent from the first strain-sensing system. The second strain-sensing system is constructed and arranged to measure the excessive strain.