Principle employed by a simple form of a piezoresistive accelerometer is shown in the following figure:

Basic features:

• Sensitivity to off-plane accelerations
• Spring-mass system is embodied as a silicon cantilever beam with a silicon proof mass attached to the free end
• Silicon cantilever thick as 15 μm is equipped
  • on one side with a piezoresistor
  • on the other side with a proof mass of a thickness 200 μm
• Rest of a silicon substrate surrounding the seismic mass serves as an accelerometer base
• Upper face of the accelerometer is closed by glass or silicon plate (not shown in the figure) in order to protect the sensible part
• If acceleration is applied on a sensor, the movement of the seismic mass bend the cantilever.
• Value of piezoresistor resistance, which varies due to varying mechanical stress in the cantilever, is then measured.
• This kind of sensor was used for measurements in the scale from 0.01 g to 100 g.