ShapeAccelArray (SAA) are manufactured by Measurand Inc. of New Brunswick, Canada and are used for measuring ground and structural deformations.
An SAA is an array of rigid segments separated by joints that move in any direction but do not twist. MEMS gravity sensors measure tilt in two directions. Processors transform the position (e.g. X, Y & Z) of each joint to produce shape and change of shape.
Each SAA comes on a drum and is installed inside a small (27mm) diameter access tube that is grouted into a borehole or void former. SAA casings can also be installed inside inclinometer casings using spacers.
Installation and removal of SAA is extremely simple because there is no joining of individual sensors to be done in the field and the single wire output from an SAA means there is very little wiring to be done to complete the installation process.
SAA is a London Underground Registered Product (ID 2721: Asset monitoring of tunnels, track beds, walls, bridges, other structures and earthworks) and has ATEX certification for use in potentially explosive environments (e.g. sewers).
SAAs can be used in vertical, horizontal and circular orientations. For inclined and near vertical orientations (< 60o to the vertical) SAAs record X, Y and Z coordinates of each joint and for horizontal arrays, settlement (e.g. X-Z, where Z represents distance along the array) can be recorded. Convergence can be measured in tunnels and sewers.
Displacements can be stored on dataloggers or read directly on computers and mobile phones. SAAs come in lengths of up to 150m. Long-term tests have shown that 32m long SAAs are accurate to ±1.5mm and precise to ±0.5mm.