A flow meter includes a cylindrical flow chamber having an axis and an internal cylindrical wall. The EL panel comprising such phosphor thin films eliminates a need for RGB phosphor filters, has a satisfactory color purity and is best suited for driving RGB in full-color EL display. This control pressure is dependent on the pressure on the meter-in side or on the meter-out side of the hydraulic motor. In exemplary process flows chemical or physical vapor deposition of a sealing layer blocks the pores due to imperfect conformality. A drive unit also adapted for implantation inside the patient’s body may be arranged for advancing and retracting the tip end of the infusion needle such that it penetrates the housing at least in two different penetration areas either simultaneously or in immediate time succession, thereby injecting drugs along with the infusion liquid into the patient’s body for stimulating penis erection.