A portable fluid collection apparatus comprising a fluid reservoir for receiving fluid produced by a person, and detection means (40) for detecting a property of fluid within the fluid reservoir. Said detection means comprises means for measuring a property of fluid between a first position and a second position spaced from said first position and means for measuring a property of fluid between said first position and a third position, where the distance between said first position and said third position is less than the distance between said first position and said second position. The portable fluid collection apparatus further comprises processor means configured to receive data from the detection means and determine the level of fluid within the fluid reservoir, said processor means being further configured to calibrate measured data corresponding to a property of fluid between said first position and said second position using measured data corresponding to a property of fluid between said first position and said third position in order to determine the level of fluid within the fluid reservoir.
