Preliminary test results in a mock FSR sensing setup are promising in some ways. The first test setup was the FSR blanketed by a 1/8″ rubber sheet compressed under a disc that is pin-guided on top of the bottom disc. Fairly static loads were applied at different points over a wide area on the load-bearing disc and corresponding sensor resistances measured.
The primary purpose of this test is to determine a baseline correlation between applied force to the test mechanism and output/sensor resistance.
The secondary purpose of this test is to determine whether or not our mechanism will provide sufficient clarity to discern between completely downward forces (eg, someone pressing straight down on a bottle), or partially ‘torqued’ forces that create uneven pressure distribution at the sensor (eg, someone pressing down and slightly pushing back on a bottle).
In this particular setup, the primary purpose is explored by this plot of applied force vs. resistance. A 3rd order curve has been fitted to the data, giving R2 on the order of 0.80. Under illustrated confidence/probability intervals, it may be inferred that we could, for example, tell fairly reliably the difference between 2kg and 5kg load. (In rough testing, I found that the average hand pump will fall somewhere between 3.5-4.5kg — but further consideration is due).
The secondary purpose seems to have been satisfied: after taking approximately 80 measurements over different forces and displacements, and fitting these as predictors of resistance, applied force is much more correlated to resistance than position. (((f-test values?))
To be taken into consideration: we need a better construction of our intended model. Although, by indication from position testing (if I am interpreting the data analysis correctly), the pin mechanism to relieve torques may not be as important as previously perceived. Worth exploring differences between rubber materials and/or FSR sizing/geometry.