876307 2 u201c medical implant having closed loop transcutaneous energy transfer tet power transfer regulation circuitry u201d to william l hassler jr ed bloom ser no 10 876038 3 u201c spatially decoupled twin secondary coils for optimizing transcutaneous energy transfer tet power transfer characteristics u201d to resha h desai william l hassler jr ser no 10 876057 4 u201c low frequency transcutaneous telemetry to implanted medical device u201d to william l hassler jr ser no 10 876058 and 5 u201c low frequency transcutaneous energy transfer to implanted medical device u201d to william l hassler jr daniel f dlugos jr ser no 10 876307 with reference to fig2 4 an implantable infuser device 30 incorporates inductive volume sensing infuser device 30 includes a fluid discharge head 32 and a cylindrical outer casing 34 sealed hermetically thereto such as by welding discharge head 32 has a discharge conduit 36 sealably attached thereto and in fluid communication with a cylindrical bellows fluid accumulator u201c bellows u201d 38 bellows 38 has an open fixed end 40 welded to an inner surface of discharge head 32 bellows 38 also has a closed moving end 42 fixedly attached to a lead screw 44 centered at the longitudinal axis of bellows 38 and extending away from bellows 38 lead screw 44 has fine male threads such as u00bc u2033 32 thereon connected to and extending from discharge head 32 surrounding the circumference of bellows 38 is a cylindrical member 46 having a rigid bottom surface 48 and a clearance hole 50 centered.