GB671812A - Piezo-electric magnetometer - Google Patents

Abstract

671,812. Magnetic tests. WALLAUSCHEK, R. Aug. 3, 1950 [Sept. 27, 1949], No. 19379/50. Class 37. A piezo-electric crystal 9, Fig. 5, is energized from a generator 10 so as to vibrate; deposited on the crystal is a metallic loop which thus vibrates in the ambient field to generate oscillations whose magnitude is proportional to the ambient field; these oscillations are applied to a meter 11. In a modified circuit, two identical crystals 81, 89 are fed in pushpull so that the currents induced in the loops 91, 92 are additive for the ambient field, and equal and opposite for any field due to the exciting current from the supply leads. The crystal 1, Fig. 2, has energizing electrodes 2, 3, and a metal ribbon 6 embracing the crystal. In a modification, the crystal has electrodes 2, 3, Fig. 6, the electrode 2 being extended at its centre at 6, Fig. 5, over the edge of the crystal to form a loop; the circuit is such that pick-up from the generator 10 in the loop 6, 2, 6, produces no output from transformer 22, while pick-up due to the ambient magnetic field is indicated on meter 11.