GB599428A - Improvements relating to apparatus and systems responsive to the intensity and direction of a magnetic field - Google Patents

Abstract

599,428. Flux gate compasses. PURVES CORPORATION. July 30, 1941, No. 9715. Convention date, July 30, 1940. [Class 40 (i)] [Also in Groups XXXV and XXXVI] Apparatus responsive to the direction and intensity of a magnetic field, for example an inductor compass, comprises a highly-permeable magnetic core 1 having poles 2, 3 for fluxcollecting and extensions 2<1>, 3<1> forming an auxiliary magnetic circuit at each end. Windings 4, 4<1> are energized from an A.C. source 7<1> in such a way as to magnetize the core equally and oppositely so that, with no external field, a slidable secondary 5 is unenergized. When, however, the core is subjected to an external magnetic field, as shown by the arrows, the periodic flux set up by coils 4, 4<1> opposes and assists the external flux in the respective ends of the core, according to the half-cycle of the A.C. source 7<1>. The theory is given in Figs. 4, 5 (not shown), but the effect is to produce in the secondary 5 a double-frequency current which, in Fig. 2, is compared in a phase detector 14, which may be as described in Specification 473,753, with the standard supply from source 7<1> passed through a frequency-doubler 15, which may be similar to that shown at 15<1> in Fig. 3. According to which side of the null position the inductor axis lies, so the phase of the output of coil 5 causes one or other winding 17 to move armature 18 to contact 19 or 19<1> so driving a motor 12 and hence the disc 11 carrying the inductor until the latter is again in the null position, whereupon no more signal is applied to relay 17 and the motor comes to rest. In Fig. 3, the device 15<1> is in the form of a full-wave rectifier circuit with condensers 16, 161 to block the D.C. component of the output, leaving the double-frequency currents free to energize the rotor 37 of a "selsyn" receiver. Three equi-angularly-arranged bars 20 ... 22, each having a set of coils as in Fig 1 have their secondary windings 27 ... 29, which generate potentials proportional to a component of the field, connected over lines 30 ... 32 to coils 34 ... 36 of the receiver 33, whereby the rotor 37 aligns itself with the resultant of the three components. The rotor is shown connected to a compass card 38, but may alternatively be connected rigidly to a power-driven object which is to be aligned with the field and the receiver 33 then utilized as a " selsyn " generator to generate a voltage proportional to the misalignment of the object with the field for controlling the driving means. The output of the coil 5 may be connected directly to a central-zero indicator, Fig. 6 (not shown), or to the movable coil of a dynamometer instrument having its fixed coil fed from an A.C. source, Fig. 7 (not shown).