CN115327449B - AMR vector magnetic gradiometer - Google Patents
AMR vector magnetic gradiometerInfo
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- CN115327449B CN115327449B CN202210866816.7A CN202210866816A CN115327449B CN 115327449 B CN115327449 B CN 115327449B CN 202210866816 A CN202210866816 A CN 202210866816A CN 115327449 B CN115327449 B CN 115327449B
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Abstract
An AMR vector magnetic gradiometer comprises a front-end magnetic field gradient measurement probe and a PCB with a rear end for signal conditioning; the front end magnetic field gradient measurement probe consists of two AMR chip sensors, and converts the magnetic field at the measurement position into a voltage signal to be output; the back-end signal conditioning circuit comprises a pre-amplifier module, a differential amplifier module, a synchronous detection module, a synchronous clock, an integration module, a V/I conversion circuit and a low-pass filter LPF, and directly outputs a voltage signal in direct proportion to the magnetic field gradient. The AMR vector magnetic gradiometer has the advantages of high sensitivity and small volume; weak magnetic field measurement can be carried out under the non-shielding condition, and the gradient sensitivity of the AMR gradiometer can be adjusted according to different measurement objects.
Description
Technical Field
The invention relates to the technical field of magnetic field measurement, in particular to an AMR vector magnetic gradiometer which is used for magnetic field gradient measurement.
Background
Magnetic field gradient measurement is generally divided into two types, one is total field gradient, and the total field gradient is generally obtained by subtracting the total field gradient measured by using two total field magnetometers with a certain distance. The other is a magnetic field gradient tensor measurement, which measures the spatial rate of change of three magnetic field components. The magnetic field gradient measurement can effectively eliminate environmental noise and background magnetic fields, and is widely applied to a plurality of fields such as geophysical resource survey, aviation navigation magnetic measurement, non-explosive positioning, biological magnetic field measurement and the like in recent years.
The total field gradiometer generally comprises two proton or optical pump probes, and two sets of signal processing units are combined to realize total field gradient measurement. Magnetic field gradient tensor measurement gradient measurement is usually performed on each magnetic field component using a vector gradiometer, and various vector gradiometers have been proposed in recent years because the vector magnetic field gradient measurement can reflect weak magnetic anomalies. The fluxgate type vector gradiometer uses a two-way structure to carry out gradient measurement, and has the problem of measurement consistency. The SQUID type vector gradiometer uses a dual-channel structure for gradient measurement, and also has the problem of measurement consistency. The SQUID vector gradiometer has strict requirements on the working temperature, so that the whole gradient measurement system has larger volume. The plate-level fluxgate gradiometer integrates two fluxgate sensors, solves the problem of consistency, but the integrated fluxgate sensor probe has special manufacturing process and difficult batch manufacturing. The prior magnetic gradiometer has the advantages that the total field magnetic gradiometer firstly performs magnetic field measurement through two magnetometer probes, then performs signal processing and data acquisition through two conditioning circuits respectively, performs external differential after output, and the two independent conditioning circuits and the data acquisition system inevitably lead to the complex integral structure and large volume of the formed gradiometer, the noise of a measuring circuit can be increased in the transmission process of a cable, and finally, when the external differential is performed, the problem of inaccurate magnetic field gradient measurement can be caused due to inconsistent output signals. The conventional vector gradiometer has the problems of measurement consistency, large volume, high cost, complex manufacturing process and the like.
Disclosure of Invention
In view of a series of problems existing in the current vector magnetic gradiometer, the invention provides an AMR vector magnetic gradiometer, and a gradient probe of the magnetic gradiometer uses two AMR chip sensors to form an integrated small-volume gradiometer. The plate-type gradiometer can not only eliminate background magnetic field and environmental magnetic noise, but also effectively reduce the volume of the gradiometer, and greatly increase the usable range of the gradiometer. In addition, the voltage output by the gradiometer and the measured magnetic field gradient directly form a linear relationship.
The technical scheme adopted by the invention is as follows:
An AMR vector magnetic gradiometer comprising:
the front end magnetic field gradient measuring probe comprises a first AMR chip sensor and a second AMR chip sensor,
The front end magnetic field gradient measuring probe is used for converting the magnetic field into a voltage signal and outputting the voltage signal;
the front-end magnetic field gradient measuring probe is connected with the rear-end signal conditioning circuit module, and the rear-end signal conditioning circuit module is used for outputting a voltage signal in direct proportion to the magnetic field gradient.
The first AMR chip sensor and the second AMR chip sensor are welded at two ends of the PCB of the probe, the base line distance d is 10cm, and the welding direction of the first AMR chip sensor and the welding direction of the second AMR chip sensor are consistent with the direction of the measured magnetic field, namely the gradient direction of the measured magnetic field is consistent with the base line direction.
The first AMR chip sensor and the second AMR chip sensor are uniaxial magnetic resistance sensors of the HMC1001, and a Wheatstone bridge formed by four resistors is arranged inside the first AMR chip sensor and the second AMR chip sensor to convert and output the measured magnetic field value into differential voltage.
The back-end signal conditioning circuit module comprises a pre-amplifier module, a differential amplifier module, a synchronous detection module, an integration module, a V/I conversion circuit and a low-pass filter; the pre-amplifier module is connected with the differential amplifier module, the differential amplifier module is connected with the synchronous detection module, the synchronous detection module is connected with the integration module, the integration module is respectively connected with the V/I conversion circuit and the low-pass filter, and the V/I conversion circuit is connected with the second AMR chip sensor.
The preamplifier module comprises a first preamplifier and a second preamplifier, wherein the first preamplifier is connected with the first AMR chip sensor and amplifies an output voltage signal of the first AMR chip sensor; the second preamplifier is connected with the second AMR chip sensor and amplifies the output voltage signal of the second AMR chip sensor.
The first preamplifier and the second preamplifier are both connected with a differential amplifier module, and the differential amplifier module carries out differential amplification on the voltage signals output by the first preamplifier and the second preamplifier and outputs the differential alternating voltage signals.
The output end of the differential amplifier module is connected to the input end of the synchronous detection module, and the synchronous detection module carries out synchronous detection on the differential voltage signal output by the differential amplifier module and outputs a detected direct-current voltage signal.
The synchronous clock module ensures that the synchronous detection module and the setting/resetting circuit are completely synchronous, and the first AMR chip sensor and the second AMR chip sensor output alternating voltage signals under the action of the setting/resetting circuit.
The output end of the synchronous detection module is connected to the input end of the integration module, and the integration module integrates the voltage signal output by synchronous detection and outputs integrated voltage.
The output end of the integrating module is connected to the input end of the V/I conversion circuit, the integrated voltage output by the integrating module is input to the V/I conversion circuit, and the V/I conversion circuit outputs feedback current to a bias current band in the second AMR chip sensor; the bias current strip can generate a feedback magnetic field which is opposite to the measuring magnetic field at the second AMR chip sensor, under the action of the combined magnetic field of the measuring magnetic field and the feedback magnetic field, the second AMR chip sensor outputs a new alternating voltage signal, the output of the first AMR chip sensor is kept unchanged, the output of the second AMR chip sensor is gradually reduced, the output of the differential amplifier module is gradually reduced, and then the output current of the V/I conversion circuit is gradually reduced until the combined magnetic field of the feedback magnetic field generated by the bias current strip in the second AMR chip sensor and the measuring magnetic field at the second AMR chip sensor is equal to the measuring magnetic field at the first AMR chip sensor, the circuit reaches a stable state, the output of the differential amplifier module is 0, the output of the integration module is not increased any more, the output of the integration module is kept unchanged, and the output integration voltage is in a proportional relation with the gradient of the measuring magnetic field.
The output end of the integration module is connected to the input end of the low-pass filter, the low-pass filter filters the voltage signal output by the integration module, and the voltage signal output by the low-pass filter is the output voltage of the gradiometer.
A magnetic field gradient measuring method of AMR vector magnetic gradiometer,
Placing the AMR vector magnetic gradiometer into a measuring magnetic field, and if the magnetic field size at the first AMR chip sensor is B 1 and the magnetic field size at the second AMR chip sensor is B 2, expressing the magnetic field gradient T at the measuring position as follows:
Wherein: d is the baseline distance of the gradiometer; Δb is the difference between the magnetic field magnitude B 1 at the first AMR chip sensor and the magnetic field magnitude B 2 at the second AMR chip sensor.
The sensitivity of the AMR chip sensor HMC1001 is 3.2mV/V/Gs, and when the bridge voltage is 5V, the sensitivity coefficient of output is S n =16 mV/Gs; the output V c of the differential amplifier is:
Vc＝k3(k1SnB1-k2SnB2)；
Wherein: k 1 and k 2 are the amplification factors of the first and second preamplifiers, respectively, and k 3 is the amplification factor of the differential amplifier. The feedback current formula output by the V/I conversion circuit is i=v d/R, where: r is a feedback resistor in the V/I conversion circuit.
The relation between the feedback magnetic field and the feedback current of the bias current band of the AMR chip sensor is B I = I/k, and k = 51mA/GS, which is the coil constant of the bias current band.
When the circuit reaches equilibrium, the output of the differential amplifier is 0, at which time,
Wherein: v c is the output voltage of the differential amplifier.
If the amplification factors k 1 and k 2 of the first preamplifier and the second preamplifier are equal, the relation between the integrated voltage V d and Δb can be obtained by the above formula: Will be Substitution can yield t=v d/kRd.
The invention relates to an AMR vector magnetic gradiometer, which has the following technical effects:
1) The magnetic gradiometer has the advantages of high sensitivity and small volume, and the AMR gradiometer is easy to integrate and can be manufactured in batches.
2) The magnetic gradiometer uses a plate-level structure, the AMR gradiometer carries out internal difference on the AMR chip sensor, directly outputs voltage signals in direct proportion to the magnetic field gradient, and has no consistency problem.
3) The magnetic gradiometer of the invention is used for magnetic field gradient measurement, can effectively inhibit the interference of environmental magnetic noise, can be used for weak magnetic field measurement under the non-shielding condition, and has lower manufacturing cost.
4) The gradient sensitivity of the AMR gradiometer is adjustable, and the gradient sensitivity of the AMR gradiometer can be adjusted according to different measuring objects.
5) The AMR vector magnetic gradiometer of the invention has the advantages that the front-end gradient measurement probe and the rear-end signal conditioning PCB can be flexibly connected and separated.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the AMR vector magnetic gradiometer of the present invention.
FIG. 2 is a circuit diagram of an AMR vector magnetic gradiometer according to the invention.
Fig. 3 is a schematic diagram of a synchronous clock module providing clock signals to a set/reset circuit and a synchronous detection circuit.
Detailed Description
As shown in fig. 1, an AMR vector magnetic gradiometer comprises:
the front end magnetic field gradient measuring probe a comprises a first AMR chip sensor 1 and a second AMR chip sensor 2,
The front end magnetic field gradient measuring probe a is used for converting the magnetic field into a voltage signal and outputting the voltage signal;
The front-end magnetic field gradient measuring probe a is connected with the rear-end signal conditioning circuit module b, and the rear-end signal conditioning circuit module b is used for outputting a voltage signal in direct proportion to the magnetic field gradient.
As shown in fig. 2, the back-end signal conditioning circuit module b includes a pre-amplifier module, a differential amplifier module 5, a synchronous detection module 6, a synchronous clock module 12, an integration module 7, a V/I conversion circuit 9, and a low-pass filter 8;
the first AMR chip sensor 1 and the second AMR chip sensor 2 are welded at two ends of the PCB of the probe, the base line distance d is 10cm, and the welding direction of the first AMR chip sensor and the welding direction of the second AMR chip sensor are consistent with the direction of the measured magnetic field, namely the gradient direction of the measured magnetic field is consistent with the base line direction.
The model of the first AMR chip sensor and the model of the second AMR chip sensor are single-axis magnetic resistance sensors of HMC1001, and a Wheatstone bridge formed by four resistors is arranged inside the single-axis magnetic resistance sensors to convert and output the measured magnetic field values into differential voltages. The chip type sensor has the characteristics of small volume, high sensitivity and low cost.
The preamplifier module comprises a first preamplifier 3 and a second preamplifier 4, wherein the first preamplifier 3 is connected with the first AMR chip sensor 1 and amplifies an output voltage signal of the first AMR chip sensor 1; the second preamplifier 4 is connected to the second AMR chip sensor 2, and amplifies an output voltage signal of the second AMR chip sensor 2.
The first preamplifier 3 and the second preamplifier 4 are differential amplifier chips with the model number AD 620.
The output ends of the first preamplifier 3 and the second preamplifier 4 are connected to the input end of the differential amplifier module 5, and the differential amplifier module 5 carries out differential amplification on the voltage signals output by the first preamplifier 3 and the second preamplifier 4 and outputs the differential alternating voltage signals.
The differential amplifier module 5 is a differential amplifier chip of model AD 620.
The output end of the differential amplifier module 5 is connected to the input end of the synchronous detection module 6, and the synchronous detection module 6 carries out synchronous detection on the differential voltage signal output by the differential amplifier module 5 and outputs a detected direct current voltage signal.
The synchronous detection module 6 is composed of a chip ADG436, and two independent selectable double-channel single-pole double-throw switches are arranged in the synchronous detection module.
The first AMR chip sensor and the second AMR chip sensor both comprise an S/R coil 10, and the synchronous clock module 12 ensures that the synchronous detection module 6 and the set/reset circuit 11 are completely synchronous, and under the action of the set/reset circuit 11, the first AMR chip sensor 1 and the second AMR chip sensor 2 output ac voltage signals. As shown in fig. 3, the synchronous clock module 12 provides synchronous clock signals to the set/reset circuit 11 and the switch synchronous detection circuit. The synchronous clock module 12 is composed of a DS1302 clock chip and a crystal oscillator, and the set/reset circuit 11 is composed of a chip TC 1428.
The output end of the synchronous detection module 6 is connected to the input end of the integration module 7, and the integration module 7 integrates the voltage signal output by synchronous detection and outputs the integrated voltage.
The integrating module 7 employs a chip OP4177.
The output end of the integrating module 7 is connected to the input end of the V/I converting circuit 9, the integrated voltage output by the integrating module 7 is input to the V/I converting circuit 9,V/I converting circuit 9 to output feedback current to the bias current band in the second AMR chip sensor 2; the bias current strip can generate a feedback magnetic field which is opposite to the measuring magnetic field at the second AMR chip sensor 2, under the action of the combined magnetic field of the measuring magnetic field and the feedback magnetic field, the second AMR chip sensor 2 outputs a new alternating voltage signal, the output of the first AMR chip sensor 1 is kept unchanged, the output of the second AMR chip sensor 2 is gradually reduced, the output of the differential amplifier module 5 is gradually reduced, the output current of the V/I conversion circuit 9 is gradually reduced until the combined magnetic field of the feedback magnetic field generated by the bias current strip in the second AMR chip sensor 2 and the measuring magnetic field at the second AMR chip sensor 2 is equal to the magnitude of the measuring magnetic field at the first AMR chip sensor 1, the circuit reaches a stable state, the output of the differential amplifier module 5 is 0, the output of the integral module 7 is not increased any more, the output of the differential amplifier module is kept unchanged, and the magnitude of the output integral voltage is in a proportional relation with the gradient of the measuring magnetic field.
The V/I conversion circuit 9 includes two OP4177 chips.
The output end of the integration module 7 is connected to the input end of the low-pass filter 8, the low-pass filter 8 filters the voltage signal output by the integration module 7, and the voltage signal output by the low-pass filter 8 is the output voltage of the gradiometer.
The low-pass filter 8 is a second-order low-pass filter circuit formed by the chip OP27 GS.
A magnetic field gradient measuring method based on the AMR vector magnetic gradiometer,
Placing the AMR vector magnetic gradiometer into a measuring magnetic field, if the magnetic field size of the first AMR chip sensor 1 is B 1, the magnetic field size of the second AMR chip sensor 2 is B 2, and the magnetic field gradient T of the measuring place is expressed as:
Wherein: d is the baseline distance of the gradiometer; Δb is the difference between the magnetic field magnitude B 1 at the first AMR chip sensor 1 and the magnetic field magnitude B 2 at the second AMR chip sensor 2.
The sensitivity of the AMR chip sensor HMC1001 is 3.2mV/V/Gs, and when the bridge voltage is 5V, the sensitivity coefficient of output is S n =16 mV/Gs; the output V c of the differential amplifier is:
Vc＝k3(k1SnB1-k2SnB2)，
Wherein: k 1 and k 2 are the amplification factors of the first preamplifier 3 and the second preamplifier 4, respectively, and k 3 is the amplification factor of the differential amplifier.
The feedback current formula output by the V/I conversion circuit 9 is i=v d/R, where: r is a feedback resistor in the V/I conversion circuit;
The relation between the feedback magnetic field and the feedback current of the bias current band of the AMR chip sensor is B I = I/k, and k = 51mA/GS, which is the coil constant of the bias current band.
When the circuit reaches equilibrium, the output of the differential amplifier is 0, at which time,
V c is the output voltage of the differential amplifier.
If the amplification factors k 1 and k 2 of the first preamplifier 3 and the second preamplifier 4 are equal, the relation between the integrated voltage V d and Δb can be obtained by the above formula: Will be Substitution can yield t=v d/kRd.
Claims (5)
1. An AMR vector magnetic gradiometer, comprising: the front end magnetic field gradient measuring probe (a) comprises a first AMR chip sensor (1) and a second AMR chip sensor (2),
The front end magnetic field gradient measuring probe (a) is used for converting the magnetic field into a voltage signal and outputting the voltage signal;
The front-end magnetic field gradient measuring probe (a) is connected with the rear-end signal conditioning circuit module (b), and the rear-end signal conditioning circuit module (b) is used for outputting a voltage signal proportional to a magnetic field gradient;
the rear-end signal conditioning circuit module (b) comprises a pre-amplifier module, a differential amplifier module (5), a synchronous detection module (6), an integration module (7), a V/I conversion circuit (9) and a low-pass filter (8); the pre-amplifier module is connected with the differential amplifier module (5), the differential amplifier module (5) is connected with the synchronous detection module (6), the synchronous detection module (6) is connected with the integration module (7), the integration module (7) is respectively connected with the V/I conversion circuit (9) and the low-pass filter (8), and the V/I conversion circuit (9) is connected with the second AMR chip sensor (2);
The pre-amplifier module comprises a first pre-amplifier (3) and a second pre-amplifier (4), wherein the first pre-amplifier (3) is connected with the first AMR chip sensor (1) and amplifies an output voltage signal of the first AMR chip sensor (1); the second preamplifier (4) is connected with the second AMR chip sensor (2) and amplifies an output voltage signal of the second AMR chip sensor (2); the first preamplifier (3) and the second preamplifier (4) are both connected with a differential amplifier module (5), and the differential amplifier module (5) carries out differential amplification on voltage signals output by the first preamplifier (3) and the second preamplifier (4) and outputs differential alternating-current voltage signals;
The output end of the synchronous detection module (6) is connected to the input end of the integration module (7), and the integration module (7) integrates the voltage signal output by synchronous detection and outputs integrated voltage;
the output end of the integrating module (7) is connected to the input end of the V/I converting circuit (9), the integrated voltage output by the integrating module (7) is input to the V/I converting circuit (9), and the V/I converting circuit (9) outputs feedback current to a bias current band in the second AMR chip sensor (2); the bias current strip can generate a feedback magnetic field opposite to a measuring magnetic field at the second AMR chip sensor (2), the second AMR chip sensor (2) outputs a new alternating voltage signal under the action of a combined magnetic field of the measuring magnetic field and the feedback magnetic field, the output of the first AMR chip sensor (1) is kept unchanged, the output of the second AMR chip sensor (2) is gradually reduced, the output of the differential amplifier module (5) is gradually reduced, the output current of the V/I conversion circuit (9) is gradually reduced until the combined magnetic field of the feedback magnetic field generated by the bias current strip in the second AMR chip sensor (2) and the measuring magnetic field at the second AMR chip sensor (2) is equal to the measuring magnetic field at the first AMR chip sensor (1), the circuit reaches a stable state, the output of the differential amplifier module (5) is 0, the output of the integral module (7) is not increased any more, and the output integral voltage is kept unchanged, and the output integral voltage is in a proportional relation with the gradient of the measuring magnetic field.
2. An AMR vector magnetic gradiometer as claimed in claim 1, wherein: the first AMR chip sensor (1) and the second AMR chip sensor (2) are welded at two ends of the PCB of the probe, the base line distance is d, and the welding direction of the first AMR chip sensor and the welding direction of the second AMR chip sensor are consistent with the direction of the detected magnetic field, namely the gradient direction of the detected magnetic field is consistent with the base line direction.
3. An AMR vector magnetic gradiometer as claimed in claim 1, wherein: the output end of the differential amplifier module (5) is connected to the input end of the synchronous detection module (6), and the synchronous detection module (6) carries out synchronous detection on the differential voltage signal output by the differential amplifier module (5) and outputs a detected direct-current voltage signal.
4. An AMR vector magnetic gradiometer as claimed in claim 1, wherein: the synchronous detection circuit further comprises a synchronous clock module (12), the synchronous clock module (12) ensures that the synchronous detection module (6) and the setting/resetting circuit (11) are completely synchronous, and under the action of the setting/resetting circuit (11), the first AMR chip sensor (1) and the second AMR chip sensor (2) output alternating voltage signals.
5. An AMR vector magnetic gradiometer as claimed in claim 1, wherein: the output end of the integration module (7) is connected to the input end of the low-pass filter (8), the low-pass filter (8) filters the voltage signal output by the integration module (7), and the voltage signal output by the low-pass filter (8) is the output voltage of the gradiometer.
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| CN202210866816.7A CN115327449B (en) | 2022-07-22 | AMR vector magnetic gradiometer |
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| WO2014033904A1 (en) * | 2012-08-31 | 2014-03-06 | 株式会社日立製作所 | Magnetoresistive sensor and gradiometer |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2014033904A1 (en) * | 2012-08-31 | 2014-03-06 | 株式会社日立製作所 | Magnetoresistive sensor and gradiometer |
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