This work presents a low-cost device for evaluating Variable Orifice Flow Meters (VOFM) used in medical mechanical ventilation applications. Specifically, the equipment was used to assess the impact of length and thickness on pressure drop for different flows in a rectangular geometry VOFM. A total of six VOFMs, with three different lengths and two different thicknesses, were evaluated. All VOFMs were stimulated with an airflow ranging from 0 $\mathrm{L}.{\mathrm{m}\mathrm{i}\mathrm{n}}^{-1}$ to 90 $\mathrm{L}.{\mathrm{m}\mathrm{i}\mathrm{n}}^{-1}$, with increments of approximately 2 $\mathrm{L}.{\mathrm{m}\mathrm{i}\mathrm{n}}^{-1}$. The experiments conducted with the device showed a strong relationship between pressure drop $∆P$ and flow rate $Q$ in the evaluated VOFMs, with two different zones: one exhibiting non-linear behavior and another showing linear behavior. The results suggest that increased length and decreased thickness lead to higher sensitivity. However, it is essential to reduce the cross-sectional area to mitigate nonlinear effects of the sensor.