The strain gauge accelerometer uses the same principle of the load cells as the detection principle, i.e., the resistance variation of a strain gauge due to the variation of its length. In these devices, a mass is suspended on a cantilever beam (fixed to the housing of the instrument), on which strain gauges connected as Wheatstone bridge are fixed.
In the presence of acceleration the mass moves, flexing the cantilever beam and consequently, the strain gauges undergo an elongation. Damping is provided by a viscous fluid-filled inside the housing. With a voltmeter, it is possible to read an unbalancing voltage of the Wheatstone bridge proportional to the acceleration.
Strain gauge accelerometer operative process: the accelerometer is fitted on to the structure whose acceleration is to be measured.
- Due to the vibration, vibrational displacement of the mass occurs, causing the cantilever beam to be strained.
- Hence the strain gauges mounted on the cantilever beam are also strained and due to this their resistance change.
- Hence a measure of this change in resistance of the strain gauge becomes a measure of the extent to which the cantilever beam is strained.
- But the resulting strain of the cantilever beam is proportional to the vibration/acceleration and hence a measure of the change in resistance of the strain gauges becomes a measure of vibration/acceleration.
- The leads of the strain gauges are connected to a wheat stone bridge whose output is calibrated in terms of vibration/acceleration.