JPH0335179A - Multi-axial magnetic detector - Google Patents

Abstract

PURPOSE:To take a measurement with high sensitivity while mutual interference among respective axes is removed by putting magnetic sensors and circuit parts for the respective axes in time-division operation. CONSTITUTION:The magnetic sensors 1X, 1Y, and 1Z are arranged orthogonally to one another and the circuit parts 2X, 2Y, and 2Z and provided with an exciting circuit part 23 and a signal lead-out part 27. Then when an axis measurement selection indicating circuit 4 outputs axis select signals SX, SY, and SZ in time order, the circuit parts 2X, 2Y, and 2Z are put in a sequential operation state on a time-division basis. Further, the circuit 4 outputs a synchronizing signal S to a multiplexer 3 and switch parts 3X, 2Y, and 2Z turn on in order to connect the sensors 1X, 1Y, and 1Z to the circuit parts 2X, 2Y, and 2Z in order. Then when the sensor for one axis and its circuit part are connected, the sensors and circuit parts for other axes are not connected and an exciting signal is inputted to only the exciting coil 12 of only one sensor at all times, so there is no mutual interference caused among the axes. Further, an exciting signal at the time of connection switching is reduced in amplitude gradually and turned off, thereby minimizing the residual magnetism of a sensor core 11.

Description

[Detailed Description of the Invention] (a) Industrial Application Fields This invention is used for measurement of geomagnetism, general magnetic measurement, detection of magnetic abnormal objects, detection of ships and vehicles, demagnetization system for ship mines, etc. This paper relates to a multi-axis magnetic detector.

(b) Conventional technology In order to measure the earth's magnetic field, etc., conventionally, a magnetic sensor is equipped with an excitation coil, a signal coil, and a compensation coil, an excitation circuit section that drives the excitation coil, and a signal derivation section that derives a magnetic signal from the signal coil. A magnetic detector is used, which consists of a circuit section including Typically, a multi-axis magnetic detector is used.

(c) Problems to be solved by the invention Multi-axis magnetic detectors suffer from problems such as mutual interference between the axes, noise noise, etc. when the respective axes are arranged closely and densely, and when high-sensitivity detection is attempted. becomes impossible to ignore. Therefore, in order to solve these problems, methods such as applying electrostatic shielding or magnetic shielding, or shifting the phase and frequency of the excitation signal of each axis are used. However, these methods have limitations in completely eliminating mutual interference and noise contamination.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a multi-axis magnetic detector that can further reduce mutual interference between the respective axes than in the past.

(D) Means and Effects for Solving the Problems The multi-axis magnetic detector of the present invention includes a plurality of magnetic sensors each having an excitation coil, a signal coil, and a compensation coil and arranged orthogonally to each other, and each of these magnetic sensors having an excitation coil, a signal coil, and a compensation coil. A connection for switching the connection between the magnetic sensor and the circuit section in a time-sharing manner in a device comprising a plurality of circuit sections including an excitation circuit section that drives an excitation coil of a sensor and a signal derivation section from which a signal coil derives a magnetic signal. A switching circuit is provided, and the amplitude of the excitation signal from each of the excitation circuit sections is gradually reduced to be turned off.

In this multi-axis magnetic detector, when the connection switching circuit operates,
The magnetic sensor and circuit section of each axis are sequentially connected in a time-sharing manner. Therefore, when the magnetic sensor and circuit section of one axis are connected, the magnetic sensor and circuit section of the other axes are not connected, and therefore the excitation signal is always input to only the excitation coil of one magnetic sensor. , mutual interference between each axis will no longer occur. Further, since the excitation signal at the time of connection switching is gradually reduced in amplitude and turned off, residual magnetism in the sensor core can be minimized.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 1 is a block diagram of a three-axis fluxgate type magnetic detector showing one embodiment of the present invention. This example magnetic sensor is a three-axis magnetic sensor lx -l'v S
1z, a three-axis circuit section 2X%27.2□, a multiplexer 3, and an axis measurement selection instruction circuit 4. The magnetic sensor 1 is a ring-type magnetic sensor, and is composed of a ring core 11, an excitation coil 12, a signal coil 13, and a feedback coil (compensation coil) 14, and the magnetic sensors Iy and 1□ are also of the same type as the magnetic sensor 1x. are used. The circuit section 2X includes an excitation circuit section 23 consisting of a controller 21 and an amplifier 22, a signal deriving section 27 consisting of an amplifier 24, a synchronous rectifier 25, and an integrating circuit 26.
It includes an amplifier 28 and a circuit 29 that feeds back to the output feedback coil 14 of the integrating circuit 26. The other circuit sections 2Y and 2□ also have the same configuration as the circuit section 2X.

The multiplexer 3 applies an excitation signal from the excitation circuit section 23 of the circuit section 2X to the excitation coil 12, adds a detection signal of the signal coil 13 to the signal derivation section 27 of the circuit section 28, and adds a feedback signal to the feedback coil 14. , a similar switch section 37 for the Y-axis, and a similar switch section 3□ for the Z-axis. Repeat in time division, sequentially O
It is designed to be N.

Circuit section 2. 1, 27.2□, the excitation signal output from the excitation circuit unit 23 is configured to gradually reduce the amplitude when switching from ON to OFF, as shown in FIG. Also, under the control of the controller 21, the integrating circuit 26
The output of circuit section 2X, 2 is held when it is OFF.
v, 2□ is designed to improve responsiveness when switching from OFF to ON.

Next, the operation of the magnetic detector of the above embodiment will be explained.

When the operation starts, axis selection signals SX, Sv, Sz are sent from the axis measurement selection instruction circuit 4 to each circuit section 2X, 27.2□
The axis selection signals Sll, SV, S, and the synchronizing signal S are outputted to the multiplexer 3 in time sequential order. The axis selection signal SX is sent to the circuit section 2. , the circuit section 2 becomes operational, and at the same time the switch section 3. of the multiplexer 3 becomes active. l is turned on. Similarly, when the axis selection signal S7 is applied to the circuit section 2v, the circuit section 2Y becomes operational, and at the same time, the switch section 37 of the multiplexer 3 is turned on.When the axis selection signal S2 is applied to the circuit section 2□ The circuit section 2z becomes operational, and at the same time, the switch section 3□' is turned on. Thereafter, the above operation is repeated every time the axis selection signals SX, Sv, and Sz are repeatedly output in time sequence.

The frequencies of the axis selection signals S, SY, and S2 are set higher than the frequency component to be measured.

When the circuit section 2x enters the operating state, an excitation signal shown in FIG. 3 is outputted from the excitation circuit section 23 and applied to the excitation coil 12. Now, when a magnetic field H is applied to the magnetic sensor 1x from the outside, a detection signal is obtained from the signal coil 13 in response to this, and is output via the switch section 3x% amplifier 24, synchronous rectifier circuit 25, and integration circuit 26. H, is derived.

Note that an offset signal is applied to the feedback circuit 29, and a background magnetic field, such as the base component of earth's magnetism, is applied to cancel and compensate for this.

Since the amplitude of the excitation signal is gradually reduced when switching from ON to OFF, the residual magnetism of the core 11 of the magnetic sensor IX is minimized and the OFF state is reached.

Further, the circuit section 2X is used for magnetic measurement at a very low frequency of several cycles or less, and includes an integrating circuit 26 having a large time constant to form a cloved loop. Therefore, when the magnetic sensor Ix side becomes OFF, it is out of the operating range due to this integrating circuit 26, and cannot respond immediately even if it is requested to change from OFF to ON. Therefore, in this embodiment, the controller 21 A circuit is provided inside to hold the integral, and when it is turned from OFF to ON, it becomes possible to respond immediately, that is, to enable high-speed response.

Further, the other circuit sections 2V and 2□ operate in exactly the same manner as the circuit section 2X.

In the above embodiment, the magnetic sensors lx, lv, and lz are ring-type magnetic sensors, but the magnetic sensors may be, for example, two shaft-type flux gate sensors on each axis as shown in FIG. XAsX1s YaSYs, Za,
An axial magnetic sensor made of Zs may also be used.

(F) Effects of the Invention According to this invention, the magnetic sensors and circuit sections for each magnetic field are operated in a time-sharing manner, and when one axis is measuring magnetism, other axes are not in an operating state, so that they can be mutually connected. 1. Highly sensitive measurement is possible without interference from other axes. Furthermore, since the amplitude is gradually reduced when switching the excitation signal from ON to OFF, there is an advantage that the amount of residual magnetism in the core of each magnetic sensor can be minimized.

[Brief explanation of drawings]

Figure 1 is a block diagram of a multi-axis magnetic detector showing one embodiment of the present invention, Figure 2 is a diagram showing another example of a magnetic sensor used in the same multi-axis magnetic detector, and Figure 3 is a block diagram of a multi-axis magnetic detector showing an embodiment of the present invention. , is a waveform diagram showing an excitation signal of the same multi-axis magnetic detector. lx 'IY '1K? Magnetic sensor, 2X ・
27 ・2. : circuit section, 3: multiplexer, 4: axis measurement selection instruction circuit, 11: core, 12: excitation coil, 13: signal coil, 14: feedback coil, 23: excitation circuit section, 27: signal derivation section.

Claims (1)

[Claims] (1) A plurality of magnetic sensors each having an excitation coil, a signal coil, and a compensation coil arranged orthogonally to each other, an excitation circuit section that drives the excitation coils of these magnetic sensors, and a signal coil that derives a magnetic signal. A multi-axis magnetic sensor comprising a plurality of circuit sections including a signal deriving section, further comprising a connection switching circuit for time-divisionally switching connections between the magnetic sensor and the circuit sections, and an excitation signal from each excitation circuit section. A multi-axis magnetic detector characterized by gradually reducing the amplitude of the magnetic field and turning it off.