Non-magnetic-ring TMR current sensor and method for eliminating influence of geomagnetic field

Abstract

The invention discloses a magnetic-ring-free TMR current sensor and method for eliminating the influence of a geomagnetic field. The magnetic-ring-free TMR current sensor comprises a TMR sensor chip, a preliminary signal processing circuit, an addition and subtraction operation circuit, a geomagnetic field feedback circuit, an offset compensation circuit and a final signal processing circuit. The preliminary signal processing circuit is used for preliminarily processing the output voltage of the TMR sensor chip; the addition and subtraction operation circuit is used for performing addition and subtraction operation on the voltage signal output by the preliminary signal processing circuit; the geomagnetic field feedback circuit is used for offsetting a geomagnetic field signal according to the addition operation output of the addition and subtraction operation circuit; the offset compensation circuit is used for performing zero drift compensation according to the output of the preliminary signal processing circuit; and the final signal processing circuit is used for performing signal processing on the final signal output by the subtraction operation of the addition and subtraction operation circuit and finally outputting the final signal. The non-magnetic-ring design enables the sensor to be smaller in size and lighter in weight, and the problems of magnetic core saturation and limited measurement range do not exist.

Description

Technical Field

[0001] The present invention belongs to the technical field of current sensors, and in particular relates to a non-magnetic ring TMR current sensor and a method for eliminating the influence of the geomagnetic field. Background Art

[0002] Current sensors play an important role in power systems, energy management, and electronic devices, and are widely used in many fields such as smart grids and Internet of Things technologies. At present, the market has a huge demand for low-cost and miniaturized current sensors, especially in applications with strict requirements on size, weight, and measurement accuracy. Current sensors based on magnetic sensors show broad application prospects due to their versatility in measuring both AC and DC and the convenience of non-contact detection.

[0003] There are currently a variety of current sensors based on magnetic field effects, such as Hall effect current sensors, fluxgate current sensors, and tunnel magnetoresistance (TMR) current sensors. Among them, TMR sensors have attracted widespread attention due to their high precision and miniaturization. These sensors indirectly determine the magnitude of the current by measuring the magnetic field generated by the current. At present, the main structures of TMR current sensors are divided into two types: with magnetic rings and without magnetic rings. TMR current sensors with magnetic rings have problems such as core saturation, limited measurement range, and large size. Most of the current TMR current sensors without magnetic ring structures extract current signals through a ring array of distributed sensor chips, and then perform algorithmic processing on the output signal of each chip to obtain the measured current value. This array-type TMR current sensor without magnetic rings is generally suitable for measuring large currents and needs to be used with corresponding signal processing algorithms. For small current measurements of mA and below, its measurement accuracy is relatively low.

[0004] When measuring small currents, most existing TMR current sensors are susceptible to external magnetic field interference, especially the interference of the geomagnetic field, due to their inherent sensitivity and magnetic field resolution. Therefore, eliminating the interference of the geomagnetic field is crucial to achieve high-precision small current measurement using TMR current sensors. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a non-magnetic ring TMR current sensor and method for eliminating the influence of the geomagnetic field, including a TMR sensor chip, a preliminary signal processing circuit, an addition and subtraction circuit, a geomagnetic field feedback circuit, an offset compensation circuit and a final signal processing circuit; the preliminary signal processing circuit is used to perform preliminary processing on the output voltage of the TMR sensor chip; the addition and subtraction circuit is used to perform addition and subtraction operations on the voltage signal output by the preliminary signal processing circuit; the geomagnetic field feedback circuit is used to cancel the geomagnetic field signal according to the addition output of the addition and subtraction circuit; the offset compensation circuit is used to perform zero drift compensation according to the output of the preliminary signal processing circuit; the final signal processing circuit is used to perform signal processing on the final signal output by the subtraction of the addition and subtraction circuit, and finally output it. The non-magnetic ring design of the present invention makes the sensor smaller in size and lighter in weight, and there is no problem of core saturation and limited measurement range.

[0006] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0007] A non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field, comprising a TMR sensor chip, a preliminary signal processing circuit, an addition and subtraction operation circuit, a geomagnetic field feedback circuit, an offset compensation circuit and a final signal processing circuit;

[0008] The TMR sensor chip includes two TMR sensor chips of the same model, TMR1 and TMR2;

[0009] The preliminary signal processing circuit is used to perform preliminary processing on the output voltage of the TMR sensor chip;

[0010] The addition and subtraction operation circuit is used to perform addition and subtraction operations on the voltage signal output by the preliminary signal processing circuit;

[0011] The geomagnetic field feedback circuit is used to cancel the geomagnetic field signal according to the addition operation output of the addition and subtraction operation circuit;

[0012] The offset compensation circuit is used to perform zero drift compensation according to the output of the preliminary signal processing circuit;

[0013] The final signal processing circuit is used to perform signal processing on the final signal output by the subtraction operation of the addition and subtraction operation circuit, and finally output it.

[0014] Furthermore, the preliminary signal processing circuit includes a signal processing circuit 1 and a signal processing circuit 2, and the signal processing circuit 1 and the signal processing circuit 2 adopt the same structure, including a filter circuit and an instrument amplifier circuit.

[0015] Furthermore, the addition and subtraction operation circuit includes an addition operation circuit and a subtraction operation circuit.

[0016] Furthermore, the geomagnetic field feedback circuit includes an integrator circuit and a feedback coil; the feedback coil includes a first feedback coil and a second feedback coil with the same number of turns and the same winding direction; the output end of the integrator circuit is connected to the starting end of the first feedback coil; the end of the first feedback coil is connected to the starting end of the second feedback coil; the end of the second feedback coil is connected to the feedback resistor and then to the ground.

[0017] Furthermore, the TMR1 is placed at the axis center position inside the first feedback coil, and the TMR2 is placed at the axis center position inside the second feedback coil. The first feedback coil and the second feedback coil are placed symmetrically with the current to be measured as the center.

[0018] Furthermore, the offset compensation circuit includes a potentiometer and a voltage follower circuit.

[0019] Furthermore, the final signal processing circuit includes a signal processing circuit 3, and the signal processing circuit 3 includes a filter circuit and a proportional operation circuit.

[0020] A method for detecting a non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field comprises the following steps:

[0021] Step 1: Collect the magnetic field of the current to be measured based on the TMR sensor chip and convert it into output voltage;

[0022] Step 2: Complete zero drift compensation and chip output error calibration through offset compensation circuit and preliminary signal processing circuit;

[0023] Step 3: Use addition and subtraction circuit to separate the geomagnetic field signal and the useful signal;

[0024] Step 4: Use the feedback magnetic field generated by the feedback coil in the geomagnetic field feedback circuit to offset the geomagnetic field at the TMR sensor chip;

[0025] Step 5: Use the final signal processing circuit to process the final signal output by the subtraction operation of the addition and subtraction operation circuit, and finally output it.

[0026] Furthermore, the zero drift compensation and chip output error calibration of the non-magnetic ring TMR current sensor that eliminates the influence of the geomagnetic field need to be performed regularly;

[0027] Furthermore, in the non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field, before the current to be measured is passed through the current line to be measured, the reference voltage of the instrument amplifier circuit in the signal processing circuit 1 is adjusted by the offset compensation circuit to achieve zero drift compensation for TMR1, and the reference voltage of the instrument amplifier circuit in the signal processing circuit 2 is adjusted by the offset compensation circuit to achieve zero drift compensation for TMR2;

[0028] After the current to be measured is passed, the outputs of the signal processing circuit 1 and the signal processing circuit 2 are made equal by adjusting the resistance values ​​of the amplifier resistors of the instrument amplifier circuits in the signal processing circuit 1 and the signal processing circuit 2, thereby realizing chip output error calibration.

[0029] The beneficial effects of the present invention are as follows:

[0030] The present invention realizes the acquisition of magnetic field signals by symmetrically distributing two TMR chips on both sides of the current to be measured, and then uses an addition and subtraction operation circuit to realize the separation of geomagnetic field signals and useful signals, and then offsets the geomagnetic field signals at the TMR sensor chip through an integrator and a feedback coil, thereby realizing zero magnetic flux of the geomagnetic field and only accurate measurement of the magnetic field of the current to be measured. Compared with the TMR current sensor with a magnetic ring, the magnetic ring-free design of the present invention makes the sensor smaller in size and lighter in weight, and there is no problem of magnetic core saturation and limited measurement range; compared with the array-type TMR current sensor without a magnetic ring, the present invention has higher accuracy for mA-level small current measurement, and only uses two TMR chips, with lower manufacturing cost, simple structure, and easy mass production and application promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of a non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field according to the present invention;

[0032] Figure 2 is a schematic diagram of a process of using a feedback coil to offset the geomagnetic field at a TMR chip provided by an embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of the position of the current to be measured and the TMR sensor chip provided by an embodiment of the present invention.

[0034] Figure markings: 1-TMR sensor chip, 2-feedback coil, 3-feedback magnetic field, 4-current magnetic field to be measured, 5-geomagnetic field, 6-current to be measured, 7-annular magnetic field, 8-TMR1 sensor chip, 9-TMR2 sensor chip, 10-sensitive axis of TMR1 sensor chip, 11-sensitive axis of TMR2 sensor chip, 12-current magnetic field generated at TMR1 sensor chip, 13-geomagnetic field at TMR1 sensor chip, 14-current magnetic field generated at TMR2 sensor chip, 15-geomagnetic field at TMR2 sensor chip. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0036] The purpose of the present invention is to provide a non-magnetic ring TMR current sensor and a detection method thereof that eliminates the influence of the geomagnetic field, so as to solve the problem that the existing TMR current sensor is interfered by the geomagnetic field when measuring small currents, as well as the problems of core saturation, limited measurement range, low accuracy and large size, thereby meeting the market demand for low-cost, miniaturized and geomagnetic interference-resistant current sensors.

[0037] The present invention is achieved through the following technical solutions:

[0038] The present invention provides a non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field, comprising the following contents:

[0039] TMR sensor chip, preliminary signal processing circuit, addition and subtraction operation circuit, geomagnetic field feedback circuit, offset compensation circuit and final signal processing circuit;

[0040] The TMR sensor chip includes two TMR sensor chips of the same model, TMR1 and TMR2; the preliminary signal processing circuit is used to perform preliminary processing on the output voltage of the TMR sensor chip; the addition and subtraction circuit is used to perform addition and subtraction operations on the voltage signal output by the preliminary signal processing circuit; the geomagnetic field feedback circuit is used to offset the geomagnetic field signal according to the addition output of the addition and subtraction circuit; the offset compensation circuit is used to perform zero drift compensation according to the output of the preliminary signal processing circuit; and the final signal processing circuit is used to perform signal processing on the final signal output by the subtraction of the addition and subtraction circuit, and finally output it.

[0041] The preliminary signal processing circuit includes a signal processing circuit 1 and a signal processing circuit 2. The signal processing circuit 1 and the signal processing circuit 2 have the same structure, including a filter circuit and an instrument amplifier circuit.

[0042] The addition and subtraction operation circuit includes an addition operation circuit and a subtraction operation circuit.

[0043] The geomagnetic field feedback circuit includes an integrator circuit and a feedback coil. The feedback coil includes a first feedback coil and a second feedback coil with the same number of turns and the same winding direction. The output end of the integrator circuit is connected to the starting end of the first feedback coil, the end of the first feedback coil is connected to the starting end of the second feedback coil, and the end of the second feedback coil is connected to a feedback resistor and then to the ground.

[0044] The TMR1 is placed at the axis center position inside the first feedback coil, and the TMR2 is placed at the axis center position inside the second feedback coil. The first feedback coil and the second feedback coil are placed symmetrically with the current to be measured as the center.

[0045] The offset compensation circuit includes a potentiometer and a voltage follower circuit.

[0046] The final signal processing circuit includes a signal processing circuit 3, and the signal processing circuit 3 includes a filter circuit and a proportional operation circuit.

[0047] The present invention provides a detection method for a non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field, which is applied to a non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field, and comprises the following steps:

[0048] The magnetic field of the current to be measured is collected based on the TMR sensor chip and converted into output voltage;

[0049] The zero drift compensation and chip output error calibration are completed through the offset compensation circuit and the preliminary signal processing circuit;

[0050] Use addition and subtraction circuits to separate geomagnetic field signals from useful signals;

[0051] The feedback magnetic field generated by the feedback coil in the geomagnetic field feedback circuit is used to offset the geomagnetic field at the TMR sensor chip;

[0052] The final signal processing circuit is used to process the final signal output by the subtraction operation of the addition and subtraction operation circuit, and finally output it.

[0053] The following steps are also included:

[0054] Zero drift compensation and chip output error calibration of the non-magnetic ring TMR current sensor to eliminate the influence of the geomagnetic field need to be performed regularly;

[0055] Before the current to be measured is passed through the current line to be measured, the reference voltage of the instrument amplifier circuit in the signal processing circuit 1 is adjusted by the offset compensation circuit to realize the zero drift compensation of TMR1, and the reference voltage of the instrument amplifier circuit in the signal processing circuit 2 is adjusted by the offset compensation circuit to realize the zero drift compensation of TMR2;

[0056] After the current to be measured is passed, the outputs of the signal processing circuit 1 and the signal processing circuit 2 are made equal by adjusting the resistance values ​​of the amplifier resistors of the instrument amplifier circuits in the signal processing circuit 1 and the signal processing circuit 2, thereby realizing chip output error calibration.

[0057] Example:

[0058] Figure 1 Schematic diagram of a non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field provided by an embodiment of the present invention. Figure 1 The non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field provided by the embodiment of the present invention includes a TMR sensor chip, a preliminary signal processing circuit, an addition and subtraction circuit, a geomagnetic field feedback circuit, an offset compensation circuit and a final signal processing circuit. The TMR sensor chip includes two TMR sensor chips of the same model, TMR1 and TMR2. The preliminary signal processing circuit includes a signal processing circuit 1 and a signal processing circuit 2. The signal processing circuit 1 and the signal processing circuit 2 adopt the same structure, including a filter circuit and an instrument amplifier circuit. The addition and subtraction circuit includes an addition circuit and a subtraction circuit. The geomagnetic field feedback circuit includes an integrator circuit and a feedback coil. The feedback coil includes a first feedback coil and a second feedback coil with the same number of turns and the same winding direction. The output end of the integrator circuit is connected to the beginning of the first feedback coil, the end of the first feedback coil is connected to the beginning of the second feedback coil, and the end of the second feedback coil is connected to a feedback resistor and then connected to the ground. The offset compensation circuit includes a potentiometer and a voltage follower circuit. The final signal processing circuit includes a signal processing circuit 3, and the signal processing circuit 3 includes a filter circuit and a proportional operation circuit.

[0059] The TMR sensor chip is used to collect magnetic field information, TMR1 is placed at the axis center position inside the first feedback coil, and TMR2 is placed at the axis center position inside the second feedback coil. The first feedback coil and the second feedback coil are placed symmetrically with the current to be measured as the center; the preliminary signal processing circuit is used to perform preliminary processing on the output voltage of the TMR sensor chip; the addition and subtraction circuit is used to perform addition and subtraction operations on the voltage signal output by the preliminary signal processing circuit; the geomagnetic field feedback circuit is used to offset the geomagnetic field signal according to the addition output of the addition and subtraction circuit, and by using an integrator circuit to input feedback current into the feedback coil, the feedback coil generates a feedback magnetic field with the same magnitude and opposite direction as the geomagnetic field, thereby achieving the purpose of offsetting the geomagnetic field; the offset compensation circuit is used to perform zero drift compensation according to the output of the preliminary signal processing circuit; the final signal processing circuit is used to perform signal processing on the final signal output by the subtraction of the addition and subtraction circuit, and finally output it.

[0060] Figure 2The figure is a schematic diagram of the process of using a feedback coil to offset the geomagnetic field at the TMR chip provided by an embodiment of the present invention. When measuring small currents, current sensors are mainly affected by external interference from the geomagnetic field. Compared with other stray magnetic fields, the geomagnetic field strength is relatively high. In a general experimental environment with low electromagnetic interference, the influence of other stray magnetic fields can be almost ignored. Therefore, the geomagnetic field has become the main source of interference that needs to be eliminated in current small current measurements. To solve this problem, based on the above embodiment, see Figure 2 The feedback coil offsetting geomagnetic field structure proposed in the present invention places the TMR sensor chip 1 at the internal axis position of the feedback coil 2. In the actual measurement process, the magnetic field initially felt by the TMR sensor chip 1 includes the magnetic field 4 of the current to be measured and the geomagnetic field 5. After the feedback current is passed through the integrator to the feedback coil 2, the feedback coil 2 generates a feedback magnetic field 3 inside thereof that is equal in magnitude to the geomagnetic field 5 and opposite in direction. The geomagnetic field 4 and the feedback magnetic field 3 offset each other, and finally realize zero magnetic flux of the geomagnetic field. Only the magnetic field of the current to be measured remains to make the TMR sensor chip 1 respond and output, thereby realizing accurate measurement of the current.

[0061] An embodiment of the present invention provides a non-magnetic ring TMR current sensor detection method for eliminating the influence of the geomagnetic field, based on the above embodiments, comprising the following steps:

[0062] The magnetic field of the current to be measured is collected based on the TMR sensor chip and converted into output voltage;

[0063] The zero drift compensation and chip output error calibration are completed through the offset compensation circuit and the preliminary signal processing circuit;

[0064] Use addition and subtraction circuits to separate geomagnetic field signals from useful signals;

[0065] The feedback magnetic field generated by the feedback coil in the geomagnetic field feedback circuit is used to offset the geomagnetic field at the TMR sensor chip;

[0066] The final signal processing circuit is used to process the final signal output by the subtraction operation of the addition and subtraction operation circuit, and finally output it.

[0067] The zero drift compensation and chip output error calibration of the non-magnetic ring TMR current sensor to eliminate the influence of the geomagnetic field need to be performed regularly, including the following steps:

[0068] Before the current to be measured is passed through the current line to be measured, the reference voltage of the instrument amplifier circuit in the signal processing circuit 1 is adjusted by the offset compensation circuit to realize the zero drift compensation of TMR1, and the reference voltage of the instrument amplifier circuit in the signal processing circuit 2 is adjusted by the offset compensation circuit to realize the zero drift compensation of TMR2;

[0069] After the current to be measured is passed, the outputs of the signal processing circuit 1 and the signal processing circuit 2 are made equal by adjusting the resistance values ​​of the amplifier resistors of the instrument amplifier circuits in the signal processing circuit 1 and the signal processing circuit 2, thereby realizing chip output error calibration.

[0070] For zero drift compensation, the main problem is caused by the zero point offset inside the TMR chip.

[0071] The zero-point drift inside the chip will cause the overall output characteristic curve to shift. After passing through the instrumentation operational amplifier, this shift is more obvious, showing as a significant level shift. In addition, because the two sets of feedback coils are not wound exactly the same, the feedback magnetic field strength is also different. When the magnetic field at one end is fully compensated, there will still be an output signal at the other end. After being processed by the integrator, it may lead to incomplete magnetic field compensation, continuous slight deviation, and difficulty in achieving balance. This problem is similar to the zero-point offset problem of the chip, which will cause the output of the instrumentation operational amplifier to shift in level. After the two level shifts are superimposed, a significant zero-point drift will be generated at the output of the instrumentation amplifier.

[0072] In order to solve the above two level drift problems, the present invention uses an offset compensation circuit to generate the required voltage signal through a potentiometer voltage divider, and uses a voltage follower to input the voltage to the reference voltage terminal of the instrumentation operational amplifier to ensure low input impedance, and then a corresponding compensation bias voltage can be applied to the reference voltage terminal of the instrumentation amplifier to achieve output signal zero drift compensation.

[0073] The chip output error calibration is caused by the difference in the output characteristics of the TMR chip. In the present invention, the output of the TMR sensor is a differential signal, which is converted into a single-ended signal by an instrument amplifier with a three-op-amp structure. It is assumed that the conversion relationship between the external magnetic field and the output voltage of the TMR sensor chip is as follows:

[0074] V1=BK 1， V2=BK2

[0075] Then: V1'=A1V 1， V2'=A2V2

[0076] Where V1 and V2 are the output voltages of the two TMR sensor chips, and K1 and K2 are conversion coefficients. B represents the magnetic induction intensity of the external magnetic field, and the output voltages of the instrumentation amplifier are represented as V1 and V2 respectively, and A1 and A2 are the amplification factors of the instrumentation amplifier. Since the input and output characteristic slopes of the two sensors are different, K1≠K2, and thus V1≠V2. To solve this problem, the output error calibration can be achieved by adjusting the amplification factor of the instrumentation operational amplifier so that V1=V2.

[0077] Figure 3 This is a schematic diagram of the position of the current to be measured and the TMR sensor chip provided by the embodiment of the present invention. Figure 3 The present invention uses two TMR sensor chips of the same model, including a TMR1 sensor chip 8 and a TMR2 sensor chip 9, which are symmetrically placed on both sides of the current to be measured. If the sensitive axis 10 of the TMR1 sensor chip 8 and the sensitive axis 11 of the TMR2 sensor chip 9 are arranged along the Y-axis direction, and the current to be measured 6 is along the Z-axis direction, a circular magnetic field 7 is generated around it. Then the current magnetic field 12 generated by the current to be measured 6 at the TMR1 sensor chip 8 will be opposite to the direction of its sensitive axis 10, and the current magnetic field 14 generated by the current to be measured 6 at the TMR2 sensor chip 9 will be the same as the direction of its sensitive axis 11. The geomagnetic fields 13 and 15 at the two sensor chips maintain a constant direction along the Y-axis, which is the same as the direction of the sensitive axes 10 and 11 of the two sensor chips. The magnetic fields detected by TMR1 and TMR2 are represented by H1 and H2 respectively, which can be expressed as:

[0078] H1=He+Hi

[0079] H2=He-Hi

[0080] Among them, He is the value of the geomagnetic field component on the sensitive axis of the TMR chip, and Hi is the value of the magnetic field generated by the current to be measured at the sensitive axis. Figure 1 After preliminary signal processing of the outputs of TMR1 and TMR2, the addition and subtraction circuit is used to separate the geomagnetic field signal and the useful signal, which can be expressed as:

[0081] H1+H2=2He

[0082] H1-H2=2Hi

[0083] Then the separated geomagnetic field signal is input into the integrator circuit, referring to Figure 2 , to achieve the offset of the geomagnetic field, and the useful signal of the separated current to be measured is output after the final signal processing. In this way, the sensor only responds to the magnetic field generated by the current to be measured, realizes zero magnetic flux in the geomagnetic field, and only accurately measures the magnetic field of the current to be measured. The method of directly measuring the current by subtraction operation is not feasible. Since the geomagnetic field is very large compared with the magnetic field of the small current to be measured, it is equivalent to the situation where the background interference magnetic field is larger than the useful signal magnetic field. The sensor that directly performs subtraction calculation measurement has very small resolution and low accuracy. In contrast, the use of feedback coils to compensate for the geomagnetic field proposed in the present invention is a simple and efficient method.

Claims

1. A non-magnetic ring TMR current sensor that eliminates the influence of the geomagnetic field, characterized in that: It includes a TMR sensor chip, a preliminary signal processing circuit, an addition and subtraction operation circuit, a geomagnetic field feedback circuit, an offset compensation circuit and a final signal processing circuit; The TMR sensor chip includes two TMR sensor chips of the same model, TMR1 and TMR2; The preliminary signal processing circuit is used to perform preliminary processing on the output voltage of the TMR sensor chip; The addition and subtraction operation circuit is used to perform addition and subtraction operations on the voltage signal output by the preliminary signal processing circuit; The geomagnetic field feedback circuit is used to cancel the geomagnetic field signal according to the addition operation output of the addition and subtraction operation circuit; The offset compensation circuit is used to perform zero drift compensation according to the output of the preliminary signal processing circuit; The final signal processing circuit is used to perform signal processing on the final signal output by the subtraction operation of the addition and subtraction operation circuit, and finally output it.

2. A non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field according to claim 1, characterized in that: The preliminary signal processing circuit includes a signal processing circuit 1 and a signal processing circuit 2. The signal processing circuit 1 and the signal processing circuit 2 have the same structure, including a filter circuit and an instrument amplifier circuit.

3. The non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field according to claim 1, characterized in that: The addition and subtraction operation circuit includes an addition operation circuit and a subtraction operation circuit.

4. The non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field according to claim 1, characterized in that: The geomagnetic field feedback circuit includes an integrator circuit and a feedback coil; the feedback coil includes a first feedback coil and a second feedback coil with the same number of turns and the same winding direction; the output end of the integrator circuit is connected to the starting end of the first feedback coil; the end of the first feedback coil is connected to the starting end of the second feedback coil; the end of the second feedback coil is connected to a feedback resistor and then to ground.

5. The non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field according to claim 1, characterized in that: The TMR1 is placed at the axis center position inside the first feedback coil, and the TMR2 is placed at the axis center position inside the second feedback coil. The first feedback coil and the second feedback coil are placed symmetrically with the current to be measured as the center.

6. The non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field according to claim 1, characterized in that: The offset compensation circuit includes a potentiometer and a voltage follower circuit.

7. The non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field according to claim 1, characterized in that: The final signal processing circuit includes a signal processing circuit 3, and the signal processing circuit 3 includes a filter circuit and a proportional operation circuit.

8. A detection method using the non-magnetic ring TMR current sensor as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Collect the magnetic field of the current to be measured based on the TMR sensor chip and convert it into output voltage; Step 2: Complete zero drift compensation and chip output error calibration through offset compensation circuit and preliminary signal processing circuit; Step 3: Use addition and subtraction circuit to separate the geomagnetic field signal and the useful signal; Step 4: Use the feedback magnetic field generated by the feedback coil in the geomagnetic field feedback circuit to offset the geomagnetic field at the TMR sensor chip; Step 5: Use the final signal processing circuit to process the final signal output by the subtraction operation of the addition and subtraction operation circuit, and finally output it.

9. A detection method according to claim 8, characterized in that: The zero drift compensation and chip output error calibration of the non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field need to be performed regularly.

10. A detection method according to claim 8, characterized in that: In the non-magnetic ring TMR current sensor for eliminating the influence of the geomagnetic field, before the current to be measured is passed through the current line to be measured, the reference voltage of the instrument amplifier circuit in the signal processing circuit 1 is adjusted by the offset compensation circuit to achieve zero drift compensation for TMR1, and the reference voltage of the instrument amplifier circuit in the signal processing circuit 2 is adjusted by the offset compensation circuit to achieve zero drift compensation for TMR2; After the current to be measured is passed, the outputs of the signal processing circuit 1 and the signal processing circuit 2 are made equal by adjusting the resistance values ​​of the amplifier resistors of the instrument amplifier circuits in the signal processing circuit 1 and the signal processing circuit 2, thereby realizing chip output error calibration.

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