Table A1.

Key parameters to characterize a pressure sensor [45,54].

Parameter	Description
Sensitivity	A measure of the capability of a sensor to transduce a pressure stimulus. It corresponds to the slope of a linear regression to the data plotted as relative output change versus pressure. Sensitivity can be calculated according to: $$S=\frac{d\left(\frac{\Delta X}{X_0}\right)}{dP}$$ where S is the sensitivity of the sensor, X is the quantitative output signal of the sensor, P is the applied pressure, and X0 is the output of the device in the absence of P. X typically corresponds to resistance (R), current (I), or capacitance (C) measurements.
Linearity	The degree to which the performance of a sensor is close to a linear behavior, in a specific pressure range. Given than a sensor is more accurate and reliable in its linear range, the greater the linear range of a sensor the better.
Limit of Detection	The smallest pressure that the sensor can distinguish from background noise.
Hysteresis	This phenomenon is the incapability of a sensor to return to its original state when the pressure is removed, and it is commonly associated to the viscoelasticity of the materials that compose the sensor. For a pressure sensor it is desirable to have a hysteresis as low as possible so that the performance is reproducible.
Response Time	The time spent by the sensor from the instant when it is subjected to a pressure until reaching 90% of a stable output for that pressure, being also negatively affected by the viscoelasticity of the materials.
Relaxation Time	The time spent by the sensor to recover its initial state once the stimulus is removed.
Endurance/Stability	Evaluated by the number of loading and unloading cycles a sensor may be subjected without significant differences in its output regarding the first solicitations.