A device and method for delivering fracture fluid into an oilfield wellbore while the well has wireline, coiled tubing, jointed tubing or any other apparatus encumbering the flow path of the erosive fluid that is being injected into the device. A first and second time stamp is generated upon the reception and successful transmission of a data packet. The partial state space can then be analyzed using state space techniques to identify physiological information for the biological system. In addition, hysteresis is maintained or increased as supply voltage is increased. A circular surface in the form of a convex portion is provided on a magnetic shield portion of the rotor hub and is arranged to oppose one axial end surface of the rotor magnet and abut against the rotor magnet such that a gap is provided between the axial end surface of the rotor magnet and the circular surface of rotor hub.