A-rival Teasi Core Guide De Démarrage Rapide page 24

Fix speed/cadence sensor on corresponding position of bike as shown
in the figure, and then tighten it with 2 nylon straps.
Then, fix it again with a rubber band.
Please note: the centers of pedals magnet and wheel magnet shall be
aligned with corresponding induction part of sensor and shall not be
deviated from it too far; the magnets shall not be more than 2 cm from
the induction part, since distance larger than 2 cm will mak e it fail to
receive the wheel spinning signal. Screws can be loosened with
screwdriver to adjust the distance between the extendible arm of
inductor and spoke magnet.