When printing in multi-color with the Prusa i3 MMU printer, the filament often moves inside the PTFE tubes. I created a Spool buffer (https://www.thingiverse.com/thing:3836504) that saves space on the desktop. In experiments, it is good to know the forces required to move the filament along the entire path.
Measuring force is relatively simple. Use a measuring spoon that contains a digital scale. Just replace the spoon with the extension that you print on the 3D printer. Use a thin string to transfer the measured force to the attachment.
Be careful not to change the slope of the balance against the vertical direction of gravity during the measurement. The force also includes the weight of the attachment.
If we want to know the force in N, then it is sufficient to consider that 1N = 100g.