Low-power magnetometer circuit with constant current drive
First Claim
1. In a magnetometer of the type having a toroidal core, a drive winding wound around the core so as to create a circumferential field within the core, drive means for driving the drive winding with an A.C. signal so that the field from the drive winding causes the core to saturate during at least a part of each cycle of the A.C. signal, and at least one sense winding and an associated signal processing channel responsive to signals from the sense winding for detecting a component of a surrounding magnetic field, the improvement comprising:
- means for sensing the current flowing in the drive winding and for producing an intermediate signal representative thereof; and
wherein the drive means includes means, responsive to the intermediate signal, for varying the frequency of the A.C. signal so as to tend to maintain a substantially constant average current flowing in the drive winding.
2 Assignments
0 Petitions
Accused Products
Abstract
The drive signal applied to the drive winding of a magnetometer is provided by a voltage controlled oscillator. The average current flowing through the drive winding is monitored, and a signal representative of the average current is applied to the input of the voltage control oscillator. The sense windings of the magnetometer are connected to a servo-loop which causes a current to flow in the sense windings which produces a magnetic field cancelling the sensed components of the earth'"'"'s magnetic field. The magnetometer uses a drive signal which saturates the core for only a short duration of time thereby reducing the power required by the magnetometer while ensuring complete saturation of the core.
-
Citations
19 Claims
-
1. In a magnetometer of the type having a toroidal core, a drive winding wound around the core so as to create a circumferential field within the core, drive means for driving the drive winding with an A.C. signal so that the field from the drive winding causes the core to saturate during at least a part of each cycle of the A.C. signal, and at least one sense winding and an associated signal processing channel responsive to signals from the sense winding for detecting a component of a surrounding magnetic field, the improvement comprising:
-
means for sensing the current flowing in the drive winding and for producing an intermediate signal representative thereof; and wherein the drive means includes means, responsive to the intermediate signal, for varying the frequency of the A.C. signal so as to tend to maintain a substantially constant average current flowing in the drive winding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
-
14. A magnetometer circuit including:
-
a saturable core having a permeability higher than the surrounding environment and having two sections within which flux lines of a surrounding magnetic field are concentrated; a drive winding wound around at least the two specified sections of the core with a polarity such that a flow of current through the drive winding produces a magnetic field in the first section having flux lines which go in the same general direction through the first section as the concentrated flux lines of a surrounding magnetic field and further produces a magnetic field in the second section having flux lines which flow in the opposite general direction through the second section as the concentrated flux lines of the surrounding magnetic field; means for driving the drive winding with an A.C. signal so that the two core sections tend to saturate during each half cycle of the A.C. signal in the absence of a surrounding magnetic field; at least one sense winding wound around the two sections of the core so as to produce an output signal when the two-core sections saturate at different times in response to a surrounding magnetic field and the magnetic field produced by the drive winding in response to the A.C. signal applied thereto; and means for monitoring the average current flowing in the drive winding and for maintaining the average current at a substantially constant level. - View Dependent Claims (15, 16, 17, 18, 19)
-
Specification