A gravity gradiometer is disclosed which has a pair of sensor bars 41, 42 mounted in housings 43 and 45. The device may comprise a catheter having a shaft wherein the distal end of the shaft includes a primary penetrating member and a secondary penetrating member. At sequential second time instants a plurality of second portions, each of said second portions comprising an information fragment of said information entity and computer language instructions for processing said information fragment, is sent. The cable holes are opened at positions separated in the sliding direction at the beginning of sliding and at the end of sliding. The mapped features may be adjusted, for example by a user, either manually or by executing one or more optimization algorithms, to achieve the desired results relative to the Bode plot. The seat is capable of supporting the ignition coil within the centralized orifice of the boot.