GB117825A - A Magnetometer for Measuring Weak Magnetic Fields. - Google Patents

Abstract

117,825. Cruz, J. L. V. da. April 23, 1917. Non-contact-making relays; variable-resistance transmitters. - Apparatus for detecting and measuring weak magnetic forces, especially from distant sources, is applicable for use in detecting submarines, exploding mines and directing torpedoes, and comprises a suspended or pivoted magnetic system acting upon microphones or special contact resistances. The magnetic system may be a single magnet or an astatic system, a coil or an electromagnet, and may be mounted in gimbals or supported by a float. In the arrangement shown in Fig. 1, a system comsisting of a long magnet A and a pair of shorter magnets B is pivoted at E and is rendered astatic by the influence of bars C and F of soft iron; the system is held between a pair of microphones M, and is controlled by a pair of adjustable magnets or coils D. The magnetic system may be replaced by reducing the parts to one side of the pivot by a counterweight. In the modification shown in Fig. 3, two magnets A<1>, A<2> are mounted coaxially on a non- magnetic bar B' pivoted at E, with two similar sets of soft-iron bars C, F, magnets D and microphones M arranged in perpendicular planes, horizontal and vertical for instance, to indicate separately the corresponding components of the magnetic force. In the arrangement shown in Fig. 4 a magnet or system A in a casing A<11> is connected to an insulator I with four projecting carbon or other rods Q. R, S, T held under pressure by spring plates H, H', and each in contact with two carbon or other blocks G connected to two separate differential galvanometers indicating the horizontal and vertical components respectively. The magnet A may be supported by a float or by a pivot between the carbons. In the modification shown in Fig. 6, a non-magnetic rod A carrying a small magnet or coil m and a counterweight Y is supported by carbon rods Q<1>, R<1> held between blocks G, U. In other modifications, the carbon rods are mounted axially on the rod and held between blocks or supported diagonally as indicated in Fig. 8 by blocks U<6>, U<7>.