As shown in the video on the applications page, a cantilever is fixed at both ends, in which one end is on a linear stage that can be displaced in the vertical direction. The video was taken before the electronics were moved into the more aesthetically pleasing circuit board and 3D printed enclosure. By displacing the beam in the vertical direction, strain being placed into the cantilever and the deflection curve changes. An optical emitter / detector pair is configured to detect the position of the cantilever at one location. Amplification and filtering electronics amplify this signal and send it to a microcontroller (dsPIC), which carries out a control loop and is configured to send a pulse of current in phase with the oscillation of the beam, allowing it to sustain its oscillation. If there is more deflection (stress) for the magnetic field induced by current to act on, there is more ‘kick’ creating a greater oscillatory magnitude.
It’s this setup that really shows the potential. The magnitude of the oscillation is proportional to the deflection (or strain) of the beam, such that what is being demonstrated is an ‘active’ strain element measuring deflections of less than 1mm on a beam that was 55mm long, in which the magnitude is changing close to 100mV for 0.1mm of deflection in the regions the slope is the greatest, all with minimal resources applied to optimize the signal. In regards to the plot of AC RMS Versus Deflection, this is a figure indicating the amplitude of oscillation versus deflection, in which the RMS is 0 where the oscillation ceased. The measurement of ‘0’ being the neutral axis wasn’t exact as the measurements taken were relative. It seems that with a pre-load applied and environment controlled, the effect could be harnessed to produce a very good measurement of strain or force.
