Abstract: Apparatus for the measurement of quasi-static gravity gradients comprising: a flexible ribbon held under tension at both ends; sensing means arranged to detect the transverse displacement of the ribbon from an undisturbed position due to the gravitational field acting on said ribbon and to generate a signal representing the displacement; and output means coupled to said sensing means and responsive to said displacement signal to generate an output signal which is a function of the gravitational gradient tensor of the gravitational field; wherein the ribbon has a non-uniform rigidity profile and/or mass profile along its length such that, in use, the displacement response of the ribbon due to the gravitational gradient of the gravitational field is enhanced and/or the displacement response of the ribbon due to the absolute gravitational acceleration of the gravitational field is suppressed.

Abstract: Apparatus for the measurement of quasi-static gravity gradients comprising: a flexible ribbon held under tension at both ends; sensing means arranged to detect the transverse displacement of the ribbon from an undisturbed position due to the gravitational field acting on said ribbon and to generate a signal representing the displacement; and output means coupled to said sensing means and responsive to said displacement signal to generate an output signal which is a function of the gravitational gradient tensor of the gravitational field; wherein the ribbon has a non-uniform rigidity profile and/or mass profile along its length such that, in use, the displacement response of the ribbon due to the gravitational gradient of the gravitational field is enhanced and/or the displacement response of the ribbon due to the absolute gravitational acceleration of the gravitational field is suppressed.

Abstract: A method and apparatus for detecting magnetic fields in which a string (1) carries an alternating current. The displacement of the string from its unperturbated position due to a magnetic gradient across the string is detected by pick-up coils (L1, L2). The signals from the pick-up coils are demodulated using a signal derived from the alternating current to produce an output.

Abstract: An apparatus for the measurement of quasi-static gravity gradients comprising a flexible string and output means for producing an output which is a function of the gravity gradients, wherein the string is fixed at both ends, and wherein the apparatus comprises sensing means for detecting the transverse displacements of the string from its undisturbed reference position due to a gravity gradient around the string. The output means is responsive to the detected displacement to produce an output which is a function of the gravity gradient. The apparatus further comprises a means mounted at a position corresponding to the mid-point between the fixed ends of the string and constructed to prevent movements of the string which correspond to its odd modes (starting from C-mode) whilst not affecting at least the movement of the string which corresponds to its second fundamental mode (S-mode).

Abstract: Apparatus for measuring gravitational fields comprising a superconducting string (1) fixed at both ends and forming part of a closed superconducting loop inductively coupled to two driving solenoids (L.sub.d1, L.sub.d2). Displacement of the string in response to a gravitational field is sensed by two magnetic flux transformers each comprising a signal coil and two pick-up coils ((L.sub.p1, L.sub.p2). Pairs of pick-up coils lie in two perpendicular planes providing two independent channels of measurements. The two arms of each flux transformer are balanced to convert only the amplitudes of the string's antisymmetric natural modes into an output voltage. The output voltage of each channel is used to produce a feed-back current distribution (L.sub.y1, L.sub.y2) proximate and parallel to the string.