A free chlorine measurement system and sensor are provided. According to one aspect of the present invention, a shielded cable is disclosed having two inner shield segments and an outer shield. The method may comprise selecting a time interval in the timeline. Wing twist and wing deflection information can be derived from the corrected measurement solution. The microblog information collection unit collects microblog information corresponding to the written information including the keyword from the microblogs. When providing the preview page to the user, the user is notified that the corresponding preview page has the copy prohibition function.