Three-axis geomagnetic sensor

Abstract

The invention, which relates to the technical field of the sensor, discloses a three-axis geomagnetic sensor comprising a three-axis magnetic induction unit, an ADC unit, a control unit and a power supply unit. Wherein the three-axis magnetic induction unit is directly connected with the ADC unit, an amplifier in the ADC unit is used for amplifying collected signals, an amplifier does not need to be additionally arranged, noise sources are reduced, and furthermore, positive and negative alternating voltage is generated through the power supply unit to supply power to the three-axis magnetic induction unit and an analog signal processing module in the ADC unit. And furthermore, the offset error of bridge measurement in the three-axis magnetic induction unit is eliminated by utilizing alternating current excitation, and the noise of an output signal of the three-axis magnetic induction unit is reduced.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a three-axis low-noise geomagnetic sensor. Background Art

[0002] The existing digital three-axis geomagnetic sensor will generate large noise during application, among which the amplifier used to amplify the magnetic induction signal collected by the magnetic probe is an important source of noise. Summary of the invention

[0003] The purpose of the present invention is to provide a three-axis geomagnetic sensor capable of reducing noise generated during application.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A three-axis geomagnetic sensor, comprising: a three-axis magnetic induction unit, an ADC unit with a built-in amplifier, a control unit and a power supply unit;

[0006] The ADC unit is connected to the three-axis magnetic induction unit and the power supply unit respectively, and the ADC unit is used to: generate a positive and negative alternating level signal, and amplify the magnetic induction signal output by the three-axis magnetic induction unit;

[0007] The power supply unit is connected to the three-axis magnetic induction unit, the ADC unit and the control unit respectively, and the power supply unit is at least used to: generate positive and negative alternating voltages according to the positive and negative alternating level signals to supply power to the three-axis magnetic induction unit and the analog signal processing module in the ADC unit.

[0008] Optionally, the first output end of the power supply unit and the positive input end of the reference voltage VREF of the three-axis magnetic induction unit are connected through a first zero-ohm resistor; the second output end of the power supply unit and the negative input end of VREF of the three-axis magnetic induction unit are connected through a second zero-ohm resistor.

[0009] Optionally, the power supply unit is connected to the ADC unit via a low-pass filter circuit;

[0010] The low-pass filter circuit comprises: a first resistor, a second resistor, a first capacitor, a second capacitor and a third capacitor;

[0011] Two ends of the second capacitor are connected to one end of the first capacitor and the third capacitor respectively; the other ends of the first capacitor and the third capacitor are grounded;

[0012] One end of the first resistor is connected to the line between the first capacitor and the second capacitor; the other end of the first resistor is connected to the first output end of the power supply unit as the VREF positive input end of the ADC unit;

[0013] One end of the second resistor is connected to the line between the second capacitor and the third capacitor; the other end of the second resistor, as the negative input end of VREF of the ADC unit, is connected to the second output end of the power supply unit.

[0014] Optionally, the first resistor and the second resistor have the same resistance value;

[0015] The first capacitor and the third capacitor have the same capacity;

[0016] The second capacitance is greater than or equal to 10 times the first capacitance.

[0017] Optionally, the common mode filtering frequency Fcm of the low-pass filtering circuit is Fcm=1 / (2πrc1);

[0018] The differential mode filter frequency Fdif of the low-pass filter circuit is 1 / (2πr(c2+0.5c1));

[0019] Wherein, r is the resistance value of the first resistor; c1 represents the first capacitor, and c2 represents the second capacitor.

[0020] Optionally, the three-axis magnetic induction unit includes: an X-axis magnetic induction module, a Y-axis magnetic induction module, a Z-axis magnetic induction module, a first circuit board, and a second circuit board;

[0021] The X-axis magnetic induction module and the Y-axis magnetic induction module are respectively arranged on the front and back surfaces of the first circuit board, and the center positions of the X-axis magnetic induction module and the Y-axis magnetic induction module correspond to each other;

[0022] The Z-axis magnetic induction module is arranged on the second circuit board; the first circuit board is vertically arranged on the second circuit board and straddles the Z-axis magnetic induction module;

[0023] The magnetic induction directions of the X-axis magnetic induction module, the Y-axis magnetic induction module and the Z-axis magnetic induction module are orthogonal to each other.

[0024] Optionally, the positive and negative alternating voltages are 5V and 0V.

[0025] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0026] In the three-axis geomagnetic sensor provided in the embodiment of the present invention, the three-axis magnetic induction unit is directly connected to the ADC unit, and the collected signal is amplified by the amplifier inside the ADC unit, without the need to set up an additional amplifier, thereby reducing the source of noise. At the same time, the power supply unit of the embodiment of the present invention can generate positive and negative alternating voltages, which are used to power the three-axis magnetic induction unit and the analog signal processing module in the ADC unit (provide AC excitation). The above AC excitation can eliminate the offset error of the bridge measurement in the three-axis magnetic induction unit, further reducing the noise of the output signal of the three-axis magnetic induction unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the module structure of a three-axis geomagnetic sensor provided in an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the structure of a three-axis magnetic induction unit;

[0029] Figure 3 for Figure 2 The left side view of the structure of the central three-axis magnetic induction unit;

[0030] Figure 4 for Figure 2 A top view of the structure of the central three-axis magnetic induction unit;

[0031] Figure 5 It is a connection diagram of the power supply unit and the three-axis magnetic induction unit;

[0032] Figure 6 Schematic diagram for powering the ADC unit.

[0033] Explanation of symbols:

[0034] Three-axis magnetic induction unit-1, ADC unit-2, control unit-3, power supply unit-4, X-axis magnetic induction module-01, Y-axis magnetic induction module-02, Z-axis magnetic induction module-03, first circuit board-04, second circuit board-05. DETAILED DESCRIPTION

[0035] The purpose of the present invention is to provide a three-axis geomagnetic sensor capable of reducing noise generated during application.

[0036] like Figure 1 As shown, the above-mentioned three-axis geomagnetic sensor includes: a three-axis magnetic induction unit 1, an ADC unit 2 with a built-in amplifier, a control unit 3 and a power supply unit 4.

[0037] Specifically, the ADC unit 2 is connected to the three-axis magnetic induction unit 1 and the power supply unit 4 respectively, and the ADC unit 2 is used to: generate a positive and negative alternating level signal, and amplify the magnetic induction signal output by the three-axis magnetic induction unit 1;

[0038] The power supply unit 4 is connected to the three-axis magnetic induction unit 1, the ADC unit 2 and the control unit 3 respectively; the power supply unit 4 is at least used to: generate positive and negative alternating voltages according to the positive and negative alternating level signals to supply power to the three-axis magnetic induction unit 1 and the analog signal processing module in the ADC unit 2.

[0039] Exemplarily, the positive and negative alternating voltages provided by the power supply unit 4 may be 5V and 0V.

[0040] It can be seen that the signal collected by the three-axis magnetic induction unit 1 is amplified by the amplifier inside the ADC unit 2, without the need for an additional amplification circuit, so that the noise is reduced. The positive and negative alternating voltages provided by the power supply unit 4 can not only eliminate the offset error of the bridge measurement in the three-axis magnetic induction unit 1, but also reduce the noise of the output signal of the three-axis magnetic induction unit 1.

[0041] See also Figures 2 to 4 The three-axis magnetic induction unit 1 includes: an X-axis magnetic induction module 01, a Y-axis magnetic induction module 02, a Z-axis magnetic induction module 03, a first circuit board 04 and a second circuit board 05.

[0042] Specifically, the X-axis magnetic induction module 01 and the Y-axis magnetic induction module 02 are respectively arranged on the front and back surfaces of the first circuit board 04, and the center positions of the X-axis magnetic induction module 01 and the Y-axis magnetic induction module 02 correspond to each other.

[0043] The Z-axis magnetic induction module 03 is disposed on the second circuit board 05 ; the first circuit board 04 is vertically disposed on the second circuit board 05 and straddles the Z-axis magnetic induction module 03 .

[0044] The magnetic induction directions of the X-axis magnetic induction module 01 , the Y-axis magnetic induction module 02 , and the Z-axis magnetic induction module 03 are orthogonal to each other.

[0045] Among them, the X-axis and Y-axis magnetic induction modules 01 and 02 and the Z-axis magnetic induction module 03 are orthogonally welded through slots on two circuit boards to form a three-axis orthogonal magnetic probe (three-axis magnetic induction unit); and each magnetic induction module is independent of each other, and can be electrically connected to the circuit board using a single-row pin, which is convenient for debugging and maintenance; in addition, the three-axis magnetic induction unit 1 can be connected to the ADC unit 2, the control unit 3 and the power supply unit 4 through 1.27mm 5-pin single-row pin welding to achieve structural connection and circuit connection.

[0046] Further, such as Figure 5As shown, the first output terminal OUTA of the power supply unit 4 is connected to the positive input terminal of the reference voltage VREF of the three-axis magnetic induction unit 1 through a first zero-ohm resistor R10; the second output terminal OUTB of the power supply unit 4 is connected to the negative input terminal of VREF of the three-axis magnetic induction unit 1 through a second zero-ohm resistor R21.

[0047] Furthermore, when the power supply unit 4 supplies power to the control unit 3 and the digital signal processing module in the ADC unit 2 , the power supply may be 3.3V, for example.

[0048] By supplying power separately to the analog signal processing module and the digital signal processing module in the ADC unit 2 , the digital signal processing module can be prevented from being disturbed by the power supply of the analog part.

[0049] For further information, see Figure 6 The power supply unit 4 and the ADC unit 2 are connected via a low-pass filter circuit.

[0050] The low-pass filter circuit includes: a first resistor R26, a second resistor R25, a first capacitor C15, a second capacitor C14 and a third capacitor C12.

[0051] Two ends of the second capacitor C14 are connected to one end of the first capacitor C15 and one end of the third capacitor C12 respectively; the other ends of the first capacitor C15 and the third capacitor C12 are both grounded.

[0052] One end of the first resistor R26 is connected to the line between the first capacitor C15 and the second capacitor C14 ; the other end of the first resistor R26 , as the VREF positive input end of the ADC unit 2 , is connected to the first output end of the power supply unit 4 .

[0053] One end of the second resistor R25 is connected to the line between the second capacitor C14 and the third capacitor C12 ; the other end of the second resistor R25 , as the negative input end of VREF of the ADC unit 2 , is connected to the second output end of the power supply unit 4 .

[0054] In one example, the first resistor R26 and the second resistor R25 have the same resistance value; the first capacitor C15 and the third capacitor C12 have the same capacity; and the second capacitor C14 is greater than or equal to 10 times the first capacitor C15.

[0055] Furthermore, the common mode filter frequency of the low-pass filter circuit is expressed as: Fcm=1 / (2πrc1);

[0056] The expression of the differential mode filter frequency of the low-pass filter circuit is: Fdif = 1 / (2πr(c2+0.5c1));

[0057] Wherein, r is the resistance value of the first resistor R26; c1 represents the first capacitor C15, and c2 represents the second capacitor C14.

[0058] By setting the above low-pass filter circuit and using common-mode filtering and differential-mode filtering at the same time, the signal noise can be further reduced. Similarly, the three-axis magnetic sensing unit 1 and the ADC unit 2 can also be connected through a low-pass filter circuit to reduce the signal noise. For details, see Figure 6 , the X-axis magnetic induction module 01 (positive output terminal X + and the negative output terminal X - )、Y-axis magnetic induction module 02 (positive output terminal Y + and the negative output terminal Y - ) and Z-axis magnetic induction module 03 (positive output terminal Z + and the negative output terminal Z - ), all pass through a low-pass filter circuit (such as Figure 6 001, 002 and 003) are connected to ADC unit 2.

[0059] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0060] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A three-axis geomagnetic sensor, characterized in that: include: A three-axis magnetic sensing unit, an ADC unit with a built-in amplifier, a control unit, and a power supply unit; The ADC unit is connected to the three-axis magnetic induction unit and the power supply unit respectively, and the ADC unit is used to: generate a positive and negative alternating level signal, and amplify the magnetic induction signal output by the three-axis magnetic induction unit; The power supply unit is connected to the three-axis magnetic induction unit, the ADC unit and the control unit respectively, and the power supply unit is at least used to: generate positive and negative alternating voltages according to the positive and negative alternating level signals to supply power to the three-axis magnetic induction unit and the analog signal processing module in the ADC unit.

2. The three-axis geomagnetic sensor according to claim 1, characterized in that: The first output end of the power supply unit is connected to the positive input end of the reference voltage VREF of the three-axis magnetic induction unit through a first zero-ohm resistor; the second output end of the power supply unit is connected to the negative input end of VREF of the three-axis magnetic induction unit through a second zero-ohm resistor.

3. The three-axis geomagnetic sensor according to claim 1, characterized in that: The power supply unit is connected to the ADC unit via a low-pass filter circuit; The low-pass filter circuit comprises: a first resistor, a second resistor, a first capacitor, a second capacitor and a third capacitor; Two ends of the second capacitor are connected to one end of the first capacitor and the third capacitor respectively; the other ends of the first capacitor and the third capacitor are both grounded; One end of the first resistor is connected to the line between the first capacitor and the second capacitor; the other end of the first resistor is connected to the first output end of the power supply unit as the VREF positive input end of the ADC unit; One end of the second resistor is connected to the line between the second capacitor and the third capacitor; the other end of the second resistor, as the negative input end of VREF of the ADC unit, is connected to the second output end of the power supply unit.

4. The three-axis geomagnetic sensor according to claim 3, characterized in that: The first resistor and the second resistor have the same resistance value; The first capacitor and the third capacitor have the same capacity; The second capacitance is greater than or equal to 10 times the first capacitance.

5. The three-axis geomagnetic sensor according to claim 3, characterized in that: The common mode filtering frequency Fcm of the low-pass filtering circuit is 1 / (2πrc1); The differential mode filter frequency Fdif of the low-pass filter circuit is 1 / (2πr(c2+0.5c1)); Wherein, r is the resistance value of the first resistor; c1 represents the first capacitor, and c2 represents the second capacitor.

6. The three-axis geomagnetic sensor according to claim 1, characterized in that: The three-axis magnetic induction unit includes: an X-axis magnetic induction module, a Y-axis magnetic induction module, a Z-axis magnetic induction module, a first circuit board and a second circuit board; The X-axis magnetic induction module and the Y-axis magnetic induction module are respectively arranged on the front and back surfaces of the first circuit board, and the center positions of the X-axis magnetic induction module and the Y-axis magnetic induction module correspond to each other; The Z-axis magnetic induction module is arranged on the second circuit board; the first circuit board is arranged vertically on the second circuit board and straddles the Z-axis magnetic induction module; The magnetic induction directions of the X-axis magnetic induction module, the Y-axis magnetic induction module and the Z-axis magnetic induction module are orthogonal to each other.

7. The three-axis geomagnetic sensor according to claim 1, characterized in that: The positive and negative alternating voltages are 5V and 0V.

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