A concentrator is used for concentrating a fluid, particularly a plasma component out of blood, for treatment of a patient. The instrument includes a handle and a probe coupled to the handle. A channel extends between the first and second chambers. Once a codevector is identified, the codebook at the next segment is searched and a concatenation of codevectors is provided by selecting up to but not including the current segment. The wave antenna, because of its bent structure, is capable of stretching and compressing more easily than other structures, reducing the wireless communication device’s susceptibility to damage or breaks that might render the wireless communication device coupled to the wave antenna unable to properly communicate information wirelessly. An integrally mounted sensor and control unit determine the pressure error resulting at the pneumatic piston.