The beauty of using a USB port mouse is that the original
mouse of the computer can be operational in tandem.
The original mouse can thus be used to help set the starting
position for measurement. Nevertheless, care must be exercised
to prevent touching the original mouse once measurement
is commencing as any such movement will result in
error in the measurements made. One assured way to prevent
this from happening is by disconnecting the original
mouse during measurement. Another precaution worth mentioning
is the possibility of the polyethylene film failing altogether.
Students should hence be cautioned from the outset
to wear proper footwear and to be watchful over this possibility
during the experiment.