CN203720339U - Superconductive quantum interference device magnetic sensing system - Google Patents
Superconductive quantum interference device magnetic sensing system Download PDFInfo
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- CN203720339U CN203720339U CN201420091512.9U CN201420091512U CN203720339U CN 203720339 U CN203720339 U CN 203720339U CN 201420091512 U CN201420091512 U CN 201420091512U CN 203720339 U CN203720339 U CN 203720339U
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Abstract
Provided by the utility model is a superconductive quantum interference device magnetic sensing system. The system comprises a first magnetic sensor which comprises a first superconductive quantum interference device and is used for adjusting the lock work point of the first superconductive quantum interference device in real time and sensing and outputting first sensing signals corresponding to the change of external magnetic flux with one magnetic flux measuring range scope after every locking, a second magnetic sensor which is disposed at the same external magnetic flux environment as the first magnetic sensor and is used for sensing and outputting second sensing signals corresponding to continuous change of intermediate and external magnetic flux in a magnetic flux environment, and a signal compensation processing unit which is used for determining magnetic flux of magnetic flux in each magnetic flux measuring range scope relative to a preset magnetic flux measuring range scope according to a difference of magnetic flux respectively reflected by the first sensing signals and the second sensing signals, compensating the change of the first sensing signals during an unlock period according to each obtained relative magnetic flux, and outputting the first sensing signals after compensation. The system provided by the utility model can continuously measure high-precision sensing signals in a long time.
Description
Technical Field
The utility model relates to a magnetic sensing system especially relates to a superconductive quantum interferometer magnetic sensing system.
Background
A sensor using a Superconducting Quantum Interference Device (SQUID) is the most sensitive and high-resolution magnetic sensor known at present. The lowest detectable magnetic field strength is of the order of femtoliter (10-15 tesla). The method is widely applied to weak magnetic signal detection and scientific research of cardiac magnetism, cerebral magnetism, extremely low field nuclear magnetic resonance and the like.
The direct current superconducting quantum interference device (dc SQUID for short) adopts two parallel Josephson junctions to form a superconducting ring in parallel, two ends of the junction are led out to form a two-terminal element, and the SQUID referred to below refers to the direct current superconducting quantum interference device. Certain bias current is loaded to the two ends of the SQUID, and the voltage at the two ends of the SQUID has the magnetic sensitivity characteristic which changes along with the magnitude of external induced magnetic flux. Typical SQUID flux-voltage transfer characteristics are periodically non-linear with a flux quantum Φ0Magnetic flux (2.07 x 10)-15Weber) is the period. Has a large magnetic flux induction range, and the magnetic flux measurement range can reach 8 multiplied by 10 reported in the literature4Phi (a)0The above.
However, the SQUID periodically nonlinear magnetic flux-voltage transfer characteristic curve does not have a single-valued function characteristic. That is, the magnitude of the actual induced magnetic flux cannot be known from the magnitude of the SQUID voltage output. The SQUID device cannot be directly used as a magnetic sensor.
At present, a SQUID magnetic sensor is a linear magnetic sensor constructed by implementing linear conversion of magnetic flux voltage through a readout circuit called a flux-locked loop (FLL for short). Magnetic sensors employing FLLs are limited in their range by the output voltage of the readout circuit (typically + -10V). Meanwhile, due to the fact that unpredictable work zero jump occurs when the loop works, the loop is unlocked, measurement is interrupted, and signal output is discontinuous. Therefore, the SQUID sensor adopting the FLL cannot play the large-range performance of the SQUID device, the unlocking is easy to occur, the measurement interruption is caused, and the magnetic flux change within the time length of 100ms-1s can only be measured when the working zero point is locked once. The reason is that the working time of locking the conventional SQUID sensor once is determined according to the interference condition of the external environment magnetic field, and some SQUID sensors can work for several minutes to several hours, and are interfered by external electromagnetic field generating devices such as power devices, mobile phones and the like to cause unlocking. This interference has some randomness. Therefore, it is mainly explained here that the SQUID magnetic sensor based on FLL is susceptible to interference, and cannot return to the original working zero point after being relocked, and continuity of measurement cannot be achieved. Therefore, the conventional SQUID magnetic sensor is not suitable for a system which continuously operates for a long time. Thus limiting the application of SQUIDs.
Due to the high precision and high response speed of SQUID magnetic sensors, SQUID magnetic sensors are beginning to be used in more and more occasions, such as the field of geomagnetic measurement and the like. However, the SQUID magnetic sensor is not suitable for long-term measurement, so that the application of the SQUID magnetic sensor in these fields is greatly limited. How to play the characteristics of the SQUID device and measure external magnetic flux for a long time (such as 1 day or more than one month), and the problem that the measurement is discontinuous due to the jump of the working zero point of the traditional SQUID magnetic sensor is solved by the technical personnel in the field.
SUMMERY OF THE UTILITY MODEL
In view of the above prior art's shortcoming, the utility model aims to provide a superconductive quantum interferometer magnetic sensing system for solve SQUID magnetic sensor among the prior art can't be for a long time, need not to measure the problem of outside magnetic flux in locking the work zero place range interval.
To achieve the above and other related objects, the present invention provides a superconducting quantum interference device magnetic sensing system, comprising: the first magnetic sensor comprises a first superconducting quantum interference device and is used for adjusting the locking working point of the first superconducting quantum interference device in real time, and inducing and outputting a first induction signal corresponding to the change of the external magnetic flux within a magnetic flux range after each locking; the second magnetic sensor is positioned in the same external magnetic flux environment as the first magnetic sensor and is used for sensing and outputting a second sensing signal corresponding to the continuous change of the external magnetic flux in the magnetic flux environment; and the signal compensation processing unit is connected with the second magnetic sensor and the first magnetic sensor and used for respectively determining the magnetic fluxes reflected by the first induction signal and the second induction signal by utilizing a preset magnetic field magnetic flux conversion coefficient, calculating the difference between the two magnetic fluxes, determining the quantity of magnetic flux quanta of the magnetic flux in each magnetic flux range relative to the preset magnetic flux range according to the obtained difference, compensating the change of the first induction signal in the unlocking period according to the obtained quantity of each relative magnetic flux, and outputting the compensated continuous first induction signal.
Preferably, the second magnetic sensor includes: a second superconducting quantum interference device; an under-feedback circuit connected to the second superconducting quantum interference device and negatively feeding back the induced signal induced by the second superconducting quantum interference device to the second superconducting quantum interference device, wherein the under-feedback circuit is configured to amplify the induced signal induced by the second superconducting quantum interference device according to a preset proportion and then negatively feed back the amplified induced signal to the second superconducting quantum interference device, so that the induced signal fed back by the second superconducting quantum interference device is output in a cycle single-value characteristic, the fed back induced signal is at a working zero point at the beginning of each magnetic flux quantum change period contained in the external magnetic flux, and the output induced signal jumps from a peak value to the working zero point at the end of the magnetic flux quantum change period; and the signal processing unit is connected with the output end of the second superconducting quantum interference device and used for determining the amplitude of the digital waveform signal of each magnetic flux quantum change period according to the direction of each jump in the induction signal induced by the second superconducting quantum interference device and generating the digital waveform signal so as to count the amplitude as an integral multiple of the magnetic flux quantum, and superposing the received induction signal and the generated digital waveform to obtain the induction signal reflecting the external magnetic flux during the integral multiple change of the continuous magnetic flux quantum.
Preferably, the under-feedback circuit includes: the amplifying unit is used for amplifying the induction signal induced by the second superconducting quantum interference device according to a preset proportion; and the feedback resistor and the feedback inductor are sequentially connected with the second superconducting quantum interference device.
Preferably, the amplifying unit is a proportional amplifier connected with the second superconducting quantum interference device; the feedback resistor is connected with the output end of the proportional amplifier, the feedback inductor is connected with the feedback resistor, and the second superconducting quantum interference device is mutually inductive.
Preferably, the second superconducting quantum interference device outputs the under-fed induction signal through an output end of the proportional amplifier.
Preferably, the amplifying unit includes: a flux amplification circuit in mutual inductance connection with the second superconducting quantum interference device, the flux amplification circuit comprising: an inductor L mutually inductive with the second superconducting quantum interference deviceaAnd a feedback inductor L which is mutually inductive with the feedback inductoraThird superconducting quantum interference device connected in series, third superconducting quantum interference device and inductor LaParallel resistor Rb22And a DC flux regulating circuit mutually inducted with the third superconducting quantum interference device; the feedback resistor is connected with the second superconducting quantum interference device, and the feedback inductor is connected with the feedback resistor; and the connection end of the feedback resistor and the second superconducting quantum interference device is also connected with the output end of the second superconducting quantum interference device.
Preferably, the signal processing unit includes: a counting waveform generator connected to an output terminal of the second superconducting quantum interference device, for generating a digital waveform signal according to a period of the received sensing signal and a direction of a transition edge of the sensing signal, wherein an amplitude of the current digital waveform signal is increased by one flux quantum when the received sensing signal is a lower transition edge, and the amplitude of the current digital waveform signal is decreased by one flux quantum when the received sensing signal is an upper transition edge; and the synthesizer is connected with the counting waveform generator and the output end of the second superconducting quantum interference device and is used for superposing the corrected induction signal and the generated digital waveform signal to obtain an induction signal which corresponds to the external magnetic flux and spans a plurality of magnetic flux quantum change periods.
Preferably, the superconducting quantum interference device magnetic sensor further comprises: a first bias circuit providing an adjustable bias current to the second superconducting quantum interference device.
Preferably, the superconducting quantum interference device magnetic sensor further comprises: a first bias circuit to provide an adjustable bias current to the second superconducting quantum interference device, and a second bias circuit to provide an adjustable bias current to the first superconducting quantum interference device.
Preferably, the signal compensation processing unit includes: the subtraction processing module is connected with the second magnetic sensor and the first magnetic sensor and used for converting the received first induction signal and the second induction signal into a first magnetic flux and a second magnetic flux respectively by taking a magnetic field and magnetic flux conversion coefficient of the first superconducting quantum interference device as a reference, and performing subtraction operation on the second magnetic flux and the first magnetic flux to obtain and output magnetic fluxes in each magnetic flux range; the balance flux quantum number calculation module is connected with the subtraction processing module and is used for calculating the flux average value in each flux range output by the subtraction processing module and determining the balance of the flux average value in each remaining flux range relative to the flux average value in the preset flux range by taking the flux average value in the preset flux range as a reference; and the compensation module is connected with the difference flux quantum number calculation module and is used for compensating the part of the first induction signal during the unlocking period according to the difference of the flux average value of each flux range relative to the flux average value of the preset flux range so as to obtain a first induction signal corresponding to the continuous change of the external flux.
As described above, the superconducting quantum interferometer magnetic sensing system of the present invention has the following advantageous effects: the superconducting quantum interference device is used for providing a second sensing signal by utilizing a second magnetic sensor which has lower precision and can sense continuous magnetic flux change for a long time, providing a first sensing signal by utilizing a first magnetic sensor which has high precision and cannot sense continuous magnetic flux change for a long time and comprises a superconducting quantum interference device, compensating and estimating discontinuous parts (namely, during unlocking) in the first sensing signal by utilizing the difference value of the second sensing signal and the first sensing signal, converting the discontinuous signals into continuous signals of the first sensing signal with high precision, further realizing that the superconducting quantum interference device continuously measures the high-precision sensing signal in a plurality of hours or even longer time, and acquiring accurate data information of the magnetic signal for subsequent data analysis.
Drawings
Fig. 1 shows a schematic structural diagram of a superconducting quantum interference device magnetic sensing system according to the present invention.
Fig. 2 is a schematic diagram showing the waveforms of the sensing signals output by the second superconducting quantum interference device before and after the feedback of the under-feedback circuit in a flux quantum variation period of the second magnetic sensor in the superconducting quantum interference device magnetic sensing system of the present invention.
Fig. 3 is a schematic diagram showing the waveform of the sensing signal outputted by the under-feedback circuit when the second magnetic sensor in the superconducting quantum interference device magnetic sensing system of the present invention continuously spans two periods of the change of the flux quantum.
Fig. 4 is a schematic structural diagram of a preferred embodiment of the second magnetic sensor in the superconducting quantum interference device magnetic sensing system of the present invention.
Fig. 5 is a schematic structural diagram of another preferred embodiment of the second magnetic sensor in the superconducting quantum interference device magnetic sensor system according to the present invention.
Fig. 6 is a schematic structural diagram of a preferred embodiment of a signal processing unit in a second magnetic sensor in a superconducting quantum interference device magnetic sensing system according to the present invention.
Fig. 7 is a schematic diagram showing the waveforms of the respective induced signals output by the shaping filter, the counting waveform generator and the synthesizer in the signal processing unit when the second magnetic sensor in the superconducting quantum interference device magnetic sensing system of the present invention continuously spans two periods of the change of the flux quantum.
Fig. 8 is a schematic structural diagram of a preferred embodiment of a signal compensation processing unit in a superconducting quantum interference device magnetic sensing system according to the present invention.
Description of the element reference numerals
1 superconducting quantum interference device magnetic sensing system
11 second magnetic sensor
111 second superconducting quantum interference device
112 under-feedback circuit
1121 proportional amplifier
1121' flux loop amplifier
1122. 1122' feedback resistor
1123. 1123' feedback inductor
1124 DC flux regulating circuit
1125 third superconducting Quantum interference device
113 signal processing unit
1131 count waveform generator
1132 analog-to-digital converter
1133 synthesizer
114 first bias circuit
115 second bias circuit
12 first magnetic sensor
121 first superconducting quantum interference device
13 signal compensation processing unit
131 subtraction processing module
132 difference flux quantum number calculating module
133 compensation module
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The present invention can also be implemented or applied through other different specific embodiments, and various details in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic concept of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the form, amount and ratio of the components in actual implementation may be changed at will, and the layout of the components may be more complicated.
Referring to fig. 1, the present invention provides a superconducting quantum interference device magnetic sensing system. The superconducting quantum interference device magnetic sensing system can accurately sense magnetic field signals of magnetic flux of external environment continuously spanning multiple magnetic flux quantum change periods, and convert the sensed magnetic field signals into sensing signals. The precision of the induction signal that superconductive quantum interference ware magnetic sensing system output be close the precision of superconductive quantum interference device.
The superconducting quantum interference device magnetic sensing system 1 comprises: a first magnetic sensor 12, a second magnetic sensor 11, and a signal compensation processing unit 13.
The first magnetic sensor 12 includes a first superconducting quantum interference device 121, and is configured to adjust a locking operating point of the first superconducting quantum interference device 121 in real time, and induce and output a first induced signal corresponding to a change of the external magnetic flux within a magnetic flux range after each locking.
The superconducting quantum interference device is a nonlinear magnetic flux voltage conversion device, linear conversion of magnetic flux voltage is realized by means of a magnetic flux locking loop (namely a read-out circuit), the read-out circuit consists of a preamplifier, an integrator, a feedback resistor and a feedback coil to form a magnetic flux negative feedback closed loop, and under the condition of closed loop operation, the voltage at a feedback end is in direct proportion to the magnetic flux detected by the SQUID, and a magnetic flux signal detected by the superconducting quantum interference device can be measured by using the voltage.
Due to the transmission characteristics of the superconducting quantum interference device, the readout circuit comprises a plurality of working points. Operating point jumps occur during operation of the read circuit due to various disturbances. Therefore, the sensing circuit needs to be able to lock to a new operating point in time. Over time, the operating point goes through several jumps, causing the output voltage of the sensing circuit to approach a spill-over (over a voltage of + -10V), i.e., beyond a flux range, and fail to operate stably.
In this embodiment, the first magnetic sensor 12 further includes: a readout circuit connected to said first superconducting quantum interference device 121.
The readout circuit includes: a preamplifier connected to the first superconducting quantum interference device 121, an integral feedback sub-circuit connected to the preamplifier and mutually inductive to the first superconducting quantum interference device 121, and a reset sub-circuit (not shown) connected to the integral feedback sub-circuit.
Wherein, the preamplifier is preferably a proportional amplifier.
The integrating feedback sub-circuit comprises: an integrator, a feedback resistor and a feedback coil (all not shown). On one hand, the integral feedback sub-circuit locks each working point of the first superconducting quantum interference device 121 in real time within a magnetic flux range, and performs integral processing on the sensing signal output by the preamplifier, and on the other hand, all the sensing signals output by the preamplifier are negatively fed back to the first superconducting quantum interference device 121, so that the first sensing signal output by the integral feedback sub-circuit has a single-value characteristic.
The reset sub-circuit is configured to reset the integral feedback sub-circuit when the first magnetic sensor 12 is unlocked, and to re-lock the operating point of the integral feedback sub-circuit. The unlocking of the first magnetic sensor 12 means that when the energy storage device in the first magnetic sensor 12 reaches the working range, the energy storage device cannot normally return to the normal working state due to approaching overflow, so that the unlocking is caused.
Specifically, when the reset sub-circuit monitors that the first magnetic sensor 12 where the reset sub-circuit is located at an overflow edge, the reset sub-circuit resets the integral feedback sub-circuit and the energy storage element in the first superconducting quantum interference device 121, so that the integral feedback sub-circuit can lock a new operating point again. However, during the reset period, the first magnetic sensor 12 cannot output or continuously output the sensing signal, and thus the first sensing signal output by the first magnetic sensor 12 is intermittent.
The reset sub-circuit includes: a controlled switch K1 connected in parallel with the capacitor in the integral feedback sub-circuit, a controlled switch K2 connected with the output end of the first magnetic sensor 12, a controlled switch K3 connected with the first superconducting quantum interference device 121, and a control device for controlling the controlled switches K1, K2 and K3 to open and close according to time sequence.
The second magnetic sensor 11 is configured to sense and output a second sensing signal corresponding to a continuous change in external magnetic flux in a magnetic flux environment.
Specifically, the second magnetic sensor 11 may be a magnetic sensor in a normal temperature environment, which is capable of sensing a continuous change of magnetic flux in an external magnetic flux environment for a long time.
The precision of the continuous second sensing signal output by the magnetic sensor in the normal temperature environment is too low, so that the advantages of high precision and quick response of the superconducting quantum interference device cannot be well reflected. As shown in fig. 4 and 5, the second magnetic sensor 11 preferably includes a second superconducting quantum interference device 111, and the second magnetic sensor 11 converts the induced signal having periodic multivalued characteristics output by the second superconducting quantum interference device 111 into a second induced signal corresponding to the external magnetic flux variation based on under-feedback induction.
Wherein the second superconducting quantum interference device 111 is in the same external magnetic flux environment and in the same orientation as the first superconducting quantum interference device 121. The second superconducting quantum interference device 111 outputs an induction signal with periodic multivalued characteristics in a magnetic flux quantum change period. For example, the waveform of the induction signal output by the second superconducting quantum interference device 111 in one period of the change of the magnetic flux quantum is similar to a sine wave.
Wherein a magnetic flux-to-magnetic field conversion ratio of the second superconducting quantum interference device 111 is equal to or less than a magnetic flux-to-magnetic field conversion ratio of the first superconducting quantum interference device 121. Preferably, the flux to field conversion ratio is the same for both.
In particular, the external magnetic flux is present in one flux quantum (2.07 × 10)-15Weber) divides multiple flux quanta intoIn a periodic time, the second magnetic sensor 11 under-feeds the sensing signal output by the second superconducting quantum interference device 111 back to the second superconducting quantum interference device 111 by using an under-feedback sensing technique, so that the sensing signal output after feedback is converted from having a periodic multivalued characteristic with respect to a working zero point to having a periodic single-valued characteristic with respect to the working zero point, and then generates a second sensing signal corresponding to the external magnetic flux change according to a change direction of the sensing signal with respect to the working zero point in each magnetic flux quantum change period. And the work zero point is the voltage value of the induction signal at the beginning and the end of each magnetic flux quantum change period.
In this embodiment, the second magnetic sensor 11 further includes: an under feedback circuit 112 and a signal processing unit 113.
The under-feedback circuit 112 is connected to the second superconducting quantum interference device 111 and negatively feeds back the induced signal output by the second superconducting quantum interference device 111 to the second superconducting quantum interference device 111, and is configured to amplify the induced signal output by the second superconducting quantum interference device 111 according to a preset proportion and then negatively feed back the amplified induced signal to the second superconducting quantum interference device 111, so that the induced signal fed back by the second superconducting quantum interference device 111 is output in a cycle single-value characteristic, and the fed back induced signal is at a working zero point at the beginning of each magnetic flux quantum change period contained in the external magnetic flux and the output induced signal jumps from a peak value to the working zero point at the end of the magnetic flux quantum change period.
Specifically, according to the principle that the superconducting quantum interference device is a periodic signal in a flux quantum variation period, the inductive signal outputted by the second superconducting quantum interference device 111 is amplified and negatively fed back to the second superconducting quantum interference device 111 by the under-feedback circuit 112, so that the magnetic flux fed back to said second superconducting quantum interference device 111 gradually and eventually equally cancels the magnetic flux at the end of the corresponding magnetic flux quantum variation period in each magnetic flux quantum variation period, in this way, the induced signal output by the second superconducting quantum interference device 111 after inducing the external magnetic flux and the magnetic flux of the negative feedback exhibits the periodic characteristic of single-valued voltage rise/fall, and the feedback induction signal is at an operation zero point when each magnetic flux quantum change period included in the external magnetic flux is initial, and the output induction signal jumps from a peak value to the operation zero point when the magnetic flux quantum change period is finished. The operation zero point may be a voltage value that is adjusted to 0v by the adjustment process of the offset voltage circuit.
Preferably, the zero point of operation in FIG. 2 (i.e., the voltage in FIG. 2 is V)ofsCorresponding W-1、W、W1Point) is taken as a starting point, and the magnetic flux corresponding to the external induction magnetic flux which is just the working zero point is taken as a reference. When the external magnetic flux increases rightward from the zero point of operation, the increased external input magnetic flux isThe second superconducting quantum interference device 111 outputsIncreases as the magnetic flux increases while the under-feedback circuit 112 generates negative feedback magnetic fluxDamping the actual induced flux of the second superconducting quantum interference device 111The rate of increase of (c). When the external magnetic flux increases to a magnetic flux quantum phi0Then, the voltage output by the second superconducting quantum interference device 111 reaches a positive maximum value; the external magnetic flux is increased again, the magnetic flux generated by the output voltage of the second superconducting quantum interference device 111 through the feedback loop can no longer maintain the capability of offsetting the external magnetic flux, work zero jump occurs automatically, the external magnetic flux change amount is just one magnetic flux quantum, the external magnetic flux enters the next work zero after jumping, and the output of the second superconducting quantum interference device 111 returns to the work zero.
On the contrary, the external flux is from the working zero pointThe decrease is started. The magnetic flux decreases to the left, and the reduced external input magnetic flux isThe second superconducting quantum interference device 111 outputsAs the magnetic flux decreases, the under-feedback circuit 112 generates negative feedback magnetic fluxDamping the actual induced flux of the second superconducting quantum interference device 111Is reduced. When the external magnetic flux decreases to reach a magnetic flux quantum, the voltage output by the second superconducting quantum interference device 111 reaches a negative maximum value; when the external magnetic flux is reduced again, the negative feedback magnetic flux generated by the output voltage of the second superconducting quantum interference device 111 is not enough to offset the increase of the external magnetic flux, and the negative feedback cannot reach balance, the transmission work zero point jumps. Since the external magnetic flux variation is exactly one magnetic flux quantum, the external magnetic flux variation enters the next working zero point after jumping, and the output of the second superconducting quantum interference device 111 returns to the working zero point.
From the above analysis courseware, starting from the work zero point, when the magnetic flux is increased to a magnetic flux quantum, the work zero point jump will occur, and the critical condition is satisfied:
wherein f isFBV(Vofs) Is the feedback flux at the operating zero.
The above two equations (1) and (2) are subtracted to obtain a critical condition to be satisfied for the implementation of the characteristics of the periodic single-valued second magnetic sensor 11: <math>
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<mi>f</mi>
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by combining the above analysis that the external magnetic flux changes in the positive direction and the negative direction and jumps in magnetic flux when an integral number of cycles are reached, the critical conditions for jumping of the working zero point can be obtained as follows:wherein:the amount of magnetic flux change, phi, induced by the second superconducting quantum interference device 111 during the peak-to-peak voltage output by the under-feedback circuit 1120Is a quantum of magnetic flux.
Therefore, the maximum induced magnetic flux and the peak-to-peak value of the output voltage of the second superconducting quantum interference device 111 are determined by the self magnetic flux-to-voltage conversion characteristic of the second superconducting quantum interference device 111: if the magnetic flux voltage conversion characteristic of the second superconducting quantum interference device 111 is regarded as a function, the following relationship is satisfied:wherein,and outputting the feedback magnetic flux variation generated by the feedback circuit during the peak-to-peak voltage period. The maximum feedback flux is a function of the peak-to-peak value of the output voltage of the feedback circuit
It should be noted that, as those skilled in the art will understand, the positive and negative polarities mentioned in the above description are not specifically referred to as positive and negative voltages, as long as the negative feedback requirement is satisfied.
It should be noted that, in addition to the fact that the measured magnetic field and the response output voltage signal have a single-value relationship, the present solution also has a hysteresis response to the change of the external magnetic field. Namely magnetismThe response curve when the field is increased is not coincident with the response curve when the magnetic field is decreased. According to the waveform shown in fig. 2, the external magnetic flux gradually increases from the zero point of operation, and the magnetic sensing voltage of the induction signal output from the under-feedback circuit 112 gradually increases due to the under-feedback, that is, the voltage output and the magnetic flux change have a single-value relationship. When the magnetic flux change of the external magnetic flux relative to the working zero point just reaches a magnetic flux quantum phi0When the voltage reaches the maximum value of the positive voltage and jumps from the maximum value to zero, the output of the under-feedback circuit 112 is the same as the initial zero-point state, so that the periodic characteristic is presented, and the period is just one magnetic flux quantum. The voltage output of the sensor remains of a periodic single value characteristic as long as the magnetic flux continues to increase. When the external magnetic flux gradually decreases, the magnetic sensor voltage output changes in a negative voltage direction. Until the flux change relative to the operating zero reaches a flux quantum, the sensor voltage reaches a maximum negative voltage and jumps from the maximum negative voltage to zero.
When the external magnetic flux induced by the second superconducting quantum interference device 111 continuously changes in a plurality of magnetic flux quantum change periods, the induced signal output by the under-feedback circuit 112 exhibits a periodic single-value characteristic, that is, the relationship between the external magnetic flux and the voltage is within one magnetic flux period (because the characteristic curves are all in terms of one magnetic flux quantum Φ)0Periodic, hereinafter referred to as a magnetic flux quantum change period) is monotonous; meanwhile, because the magnetic flux voltage characteristic curve presents hysteresis characteristics, when the positive voltage maximum value jumps to zero (namely a lower jumping edge), the magnetic flux of the external magnetic flux in the next period is one magnetic flux quantum more than that in the current period; when the output voltage jumps from the maximum value of the negative voltage to zero (namely an upper jumping edge), the fact that the magnetic flux of the external magnetic flux in the next period is one magnetic flux quantum less than that of the current period is shown.
For example, as shown in FIG. 3, the ambient magnetic flux is gradually increased from 0 to 2 Φ0Then 2 phi0Stepwise decrease to 0 (phi)0Is 2.07 x 10-15Weber), then the second superconducting quantum interference device 111 is in the under-feedback circuit 112, the waveform of the finally output induction signal is periodical and single-valued. Wherein, the waveforms shown from top to bottom in fig. 3 are respectively: external magnetic flux and an electric signal output after the feedback of the under-feedback circuit.
In this embodiment, the under-feedback circuit 112 includes: the circuit comprises an amplifying unit, a feedback inductor and a feedback resistor. Wherein the feedback resistor is connected to the output terminal of the second magnetic sensor 11.
The amplifying unit is connected to the second superconducting quantum interference device 111, and is configured to amplify the sensing signal induced by the second superconducting quantum interference device 111 according to a preset ratio.
The feedback resistor and the feedback inductor are sequentially connected with the second superconducting quantum interference device 111.
Based on this embodiment amplification unit, feedback inductance and feedback resistance, the utility model discloses still more specific give two embodiments:
one embodiment is: as shown in fig. 4, the amplifying unit is a proportional amplifier 1121 connected to the second superconducting quantum interference device 111; the feedback resistor is connected to the output end of the proportional amplifier 1121, the feedback inductor 1123 is connected to the feedback resistor 1122, and the second superconducting quantum interference device 111 is mutually inductive; the output terminal of the under-feedback circuit 112 is the output terminal of the proportional amplifier 1121.
Specifically, in this embodiment, the under-feedback circuit 112 first amplifies the sensing signal sensed by the second superconducting quantum interference device 111 by a preset ratio, and then negatively feeds back the amplified sensing signal to the second superconducting quantum interference device 111 through the feedback inductor. Wherein, the output end of the second superconducting quantum interference device 111 can be separately connected with a proportional amplifier. Preferably, the separately connected proportional amplifier is shared with the proportional amplifier 1121, and the second superconducting quantum interference device 111 outputs an under-fed induction signal through an output end of the proportional amplifier 1121.
In order to avoid that the feedback resistor generates a large shunt to the second superconducting quantum interference device 111 and affects the amplitude of the output voltage of the second superconducting quantum interference device 111, the resistance value of the feedback resistor 1122 is required to be 10 times or more than the dynamic resistance of the second superconducting quantum interference device 111. Wherein the under-feedback circuit 112 amplifies the magnetic flux feedback coefficient K in proportion and performs negative feedbackFIt should satisfy:wherein M isfFor mutual inductance, R, between the under-feedback circuit 112 and the second superconducting quantum interference device 111FIs the resistance value, G, of the feedback resistor 1122 in the under-feedback circuit 1120Is a scale factor. Adjusting the flux feedback coefficient KFIncluding but not limited to: the flux feedback coefficient is adjusted by adjusting the resistance of feedback resistor 1122; or the flux feedback coefficient is adjusted by adjusting the adjustable bias current of the second superconducting quantum interference device 111.
Another embodiment is: as shown in fig. 5, the amplifying unit includes: the flux amplification circuit 1' connected with the second superconducting quantum interference device 111 in mutual inductance comprises: an inductance L mutually inductive with the second superconducting quantum interference device 111aA feedback inductor 1123' and an inductor LaA third superconducting quantum interference device 1125 connected in series with the third superconducting quantum interference device 1125 and an inductor LaParallel resistor Rb22And a dc flux conditioning circuit 1124 which is mutually inductive with said third superconducting quantum interference device 1125; the feedback resistor 1122 ' is connected to the second superconducting quantum interference device 111, and the feedback inductor 1123 ' is connected to the feedback resistor 1122 '; the connection end of the feedback resistor 1122' and the second superconducting quantum interference device 111 is further connected to the output end of the under-feedback circuit 112. Preferably, the magnetic flux amplifying loop 1121 ', the direct current magnetic flux regulating loop 1124, the second superconducting quantum interference device 111 and the feedback inductor 1123' are integratedAn integrated circuit board.
Wherein the DC flux regulating circuit of the third superconducting quantum interference device 1125 (SQD 3) is controlled by an adjustable voltage VdcAnd a resistance RdcSeries inductance LdcForming a loop, adjusting VdcDrive resistor RdcGenerating a current through LdcConverted into magnetic flux and passed through mutual inductance MdcDirect current magnetic flux is coupled into the SQD 3. VdcAnd RdcIs selected such that at least one magnetic flux quantum Φ is generated in the SQD30The adjustable magnetic flux and the direct current magnetic flux adjustment enable the superconducting quantum interference device to be at the working zero point with the maximum magnetic flux voltage transmission rate, and the feedback coil L of the under-feedback circuit 112fThe generated magnetic flux is amplified. In the figure Rb22And Rb21Bias voltage Vb2Carrying out partial pressure Rb22Selected in the range of 0.1 ohm to 5 ohm. Rb21Selection and Vb2Cooperate such that Rb22An adjustable bias voltage in the range of 0-100 uV is generated at the two ends and is loaded into the third superconducting quantum interference device 1125 connected in parallel with the two ends.
The operation of the circuit shown in fig. 5 is: the feedback inductor in the under-feedback circuit 112 firstly feeds back the sensing signal sensed by the second superconducting quantum interference device 111 to the third superconducting quantum interference device 1125, and then the third superconducting quantum interference device 1125 and the inductor L form the feedback inductoraAnd a resistance Rb22The magnetic flux loop amplifier 1121' performs amplification according to a preset proportion and then negatively feeds back the amplified magnetic flux loop amplifier to the second superconducting quantum interference device 111.
As can be seen from the above two embodiments, the under-feedback circuit 112 may be a linear under-feedback circuit 112 as shown in fig. 4, or may be a nonlinear under-feedback circuit 112 as shown in fig. 5, so that the under-feedback circuit 112 in the present invention is not limited to the above two embodiments, as long as the peak value and the operation zero point of the under-fed induction signal in one magnetic flux quantum change period satisfy the critical condition.
Then, the signal processing unit 113 andthe output end of the second superconducting quantum interference device 111 is connected to determine the amplitude of the digital waveform signal of the corresponding period according to the direction of each jump in the induced signal induced by the second superconducting quantum interference device 111, generate the digital waveform signal according to the period of the received induced signal, and superimpose the received induced signal and the generated digital waveform signal to obtain a second induced signal reflecting the continuous change of the external magnetic flux. The signal processing unit 113 may be an intelligent electronic device including a CPU, such as an embedded device, a single chip, a computer device, and the like. Wherein, when the received induction signal is a lower jump edge, the amplitude of the current digital waveform signal is increased by a magnetic flux quantum phi0When the received induction signal is an up-jump edge, the amplitude of the current digital waveform signal is reduced by one magnetic flux quantum phi0. Wherein, the waveform of the digital waveform signal can be a square wave or the like.
Specifically, the signal processing unit 113 counts the magnetic flux periods by applying a characteristic that the magnetic flux increases and decreases the voltage hysteresis of the induction signal output for one magnetic flux quantum change period. That is, the voltage value of the induction signal is judged according to the fact that the external magnetic flux change is less than one period, and when the external magnetic flux change exceeds one period, the magnetic flux period is counted according to the jump of the voltage.
Preferably, as shown in fig. 6, the signal processing unit 113 includes: analog-to-digital converter 1132, count waveform generator 1131, and synthesizer 1133. The parts in the signal processing unit 113 are preferably implemented by digital signal processing, so as to widen the range of the entire magnetic sensor.
The analog-to-digital converter 1132 is configured to perform analog-to-digital conversion processing on the sensing signal induced by the second superconducting quantum interference device 111.
The counting waveform generator 1131 is connected to the output end of the analog-to-digital converter 1132, and configured to generate a digital waveform signal according to the period of the digitized sensing signal sensed by the second superconducting quantum interference device and the direction of the transition edge of the sensing signal, where the amplitude of the current digital waveform signal is increased by one magnetic flux quantum when the received sensing signal is a lower transition edge, and the amplitude of the current digital waveform signal is decreased by one magnetic flux quantum when the received sensing signal is an upper transition edge.
The synthesizer 1133 is connected to the count waveform generator 1131 and the analog-to-digital converter 1132, and is configured to superimpose the digitized induction signal and the generated digital waveform signal to obtain a second induction signal corresponding to a period of continuous change of the external magnetic flux across multiple magnetic flux quanta.
For example, as shown in fig. 7, wherein the signals from top to bottom in fig. 7 respectively represent: external measured magnetic flux phieA waveform, a signal waveform received by the signal processing unit 13, a signal waveform output by the shaping filter 132, a digital waveform signal output by the count waveform generator 131, and a signal waveform synthesized by the synthesizer 133.
The initial voltage of the induced signal received by the signal processing unit 113 and induced by the second superconducting quantum interference device 111 is 0v, and increases to the positive peak value in the first period, the amplitude of the digital waveform signal of the count waveform generator 1131 in the first period is 0, and when the first period ends, the induced signal has a down-transition edge, the amplitude of the digital waveform signal of the second period generated by the count waveform generator 1131 is 1 Φ0If the sensing signal is still the lower transition edge at the end of the second period, the amplitude of the digital waveform signal of the third period generated by the counting waveform generator 1131 is 2 Φ0Continuing, when the sensing signal is an up-transition edge at the end of the third period, the amplitude of the digital waveform signal of the fourth period generated by the counting waveform generator 1131 is 1 Φ0And so on;
the synthesizer 1133 superimposes the digitized induction signal and the generated digital waveform signal, so as to obtain a second induction signal that is consistent with the magnetic flux variation trend of the external magnetic flux, i.e., an oscillogram shown in fig. 7.
As can be seen from fig. 3, 7, the external magnetic flux continuously spans two periods of flux quantum variation, and so on. The utility model discloses a second magnetic sensor 11 can need not to carry out the locking at work zero point and just can respond to the second induced signal of magnetic flux variation range in a plurality of magnetic flux quantum change cycle.
Preferably, the signal processing unit 113 may further include an integer filter (not shown).
The shaping filter is used for linearly correcting the induction signal induced by the second superconducting quantum interference device 111.
Specifically, the shaping filter may be connected to the analog-to-digital converter 1132, and may perform linear rectification on the sensing signal according to a filtering requirement. Or, the shaping filter is connected between the analog-to-digital converter 1132 and the second superconducting quantum interference device 111, that is, performing advanced linear rectification and then performing analog-to-digital conversion. The corrected digitized sensing signal is then input to the synthesizer 1133.
In addition to the above units, circuits, and the like, as shown in fig. 4 and 5, the second magnetic sensor 11 further includes: a first bias circuit 114 for providing an adjustable bias current to the second superconducting quantum interference device 111. Wherein the adjustable bias voltage source V in the first bias circuit 114b1Drive bias resistor Rb1Generating an adjustable bias current I to said second superconducting quantum interference device 111b1，Ib1The adjustable range is 0-100 uA.
With reference to fig. 5, the second magnetic sensor 11 further includes: a second bias circuit 115 for providing an adjustable bias current to the first superconducting quantum interference device 121.
The signal compensation processing unit 13 is connected to the second magnetic sensor 11 and the first magnetic sensor 12, and configured to determine the magnetic fluxes reflected by the first sensing signal and the second sensing signal respectively by using a preset magnetic field-magnetic flux conversion coefficient, calculate a difference between the two magnetic fluxes, determine the number of magnetic flux quanta in each magnetic flux range relative to the preset magnetic flux range according to the obtained difference, compensate the change of the first sensing signal during the lock-out period according to the obtained number of relative magnetic fluxes, and output the compensated continuous first sensing signal.
It should be noted that the signal compensation processing unit 13 may be formed by an analog device. Preferably, the signal compensation processing unit 13 is an electronic device including an analog-to-digital conversion module and a processor. The signal compensation processing unit 13 is an electronic device including a processor, and is not limited by the range of the analog signal, so as to provide a wider span of measurement.
Specifically, if the superconducting quantum interference devices 111 and 121 in the two magnetic sensors 11 and 12 are the same, the signal compensation processing unit 13 first converts the obtained first induced signal and second induced signal into corresponding magnetic fluxes according to the magnetic field-magnetic flux conversion coefficients of the superconducting quantum interference devices 111 and 121 in the two magnetic sensors 11 and 12, respectively, subtracts the converted two magnetic fluxes, to obtain the change of the magnetic flux in each magnetic flux range reflected by the first induction signal, then to count the magnetic flux in each magnetic flux range to obtain the magnetic flux in one magnetic flux range, if the magnetic flux in the first magnetic flux range is taken as the preset reference, the signal compensation processing unit 13 can obtain the relative flux quantity (i.e. Φ) of the flux in the counted remaining flux range with respect to the flux of the preset reference.OFSi-ΦOFS0Wherein phi isOFSiIs the magnetic flux in the ith rest magnetic flux range, phiOFS0The magnetic flux within the magnetic flux range which is a preset reference), then, the signal compensation processing unit 13 determines the difference between the magnetic flux amounts between the adjacent magnetic flux range according to the obtained relative magnetic flux amounts, calculates the induced signal change of the first induced signal during the unlocking period according to the determined difference and a compensation algorithm, and compensates the induced signal changeThe first sensing signal is outputted, thereby obtaining a continuous sensing signal with high precision.
If the superconducting quantum interference devices 111 and 121 in the two magnetic sensors 11 and 12 are different, that is, the magnetic field-to-magnetic flux conversion coefficients of the superconducting quantum interference devices are different, the magnetic flux corresponding to the two sensing signals is obtained by multiplying the second sensing signal output by the second magnetic sensor 11 by K2/K1 with the magnetic field-to-magnetic flux conversion coefficient of the first superconducting quantum interference device 121 in the first magnetic sensor 12 as a reference. Where K1 is a magnetic field-to-magnetic flux conversion coefficient of the first magnetic sensor 12, and K2 is a magnetic field-to-magnetic flux conversion coefficient of the second magnetic sensor 11. Next, the signal compensation processing unit 13 performs subtraction processing and compensation processing on the two magnetic flux quantum quantities.
In this embodiment, as shown in fig. 8, the sensing signals provided by the first magnetic sensor 12 and the second magnetic sensor 11 are both digital signals, and the signal compensation processing unit 13 includes: a subtraction processing module 131, a difference flux quantum number calculation module 132, and a compensation module 133.
The subtraction processing module 131 is connected to the second magnetic sensor 11 and the first magnetic sensor 12, and configured to convert the received first induced signal and the second induced signal into a first magnetic flux and a second magnetic flux respectively, and perform subtraction operation on the second magnetic flux and the first magnetic flux to obtain and output magnetic fluxes in each magnetic flux range, with the magnetic field-to-magnetic flux conversion coefficient of the first superconducting quantum interference device as a reference.
The difference flux quantum number calculating module 132 is connected to the subtraction processing module 131, and is configured to calculate the average value of the flux in each flux range output by the subtraction processing module 131, and determine the difference between the average value of the flux in each remaining flux range and the average value of the flux in the preset flux range based on the average value of the flux in the preset flux range.
Specifically, the difference flux quantum number calculation module 132 calculates the difference flux quantum number according to the magnetism in each flux rangeArithmetic mean operation with varying sampling pointsIf the average value of the magnetic flux in the first magnetic flux range is taken as a preset reference, the difference (i.e. the relative magnetic flux quantity) between the average value of the magnetic flux in each of the remaining magnetic flux ranges and the average value of the magnetic flux in the preset magnetic flux range can be determined.
Preferably, the difference flux quantum number calculation module 132 adopts a principle of rounding nearby when calculating each difference, that is, the calculated difference needs to satisfy the formula:wherein, Δ NiThe difference (positive or negative) between the ith rest flux range and the preset flux range, phi0Is a flux quantum, phiOFSiIs the average value of the magnetic flux in the ith rest magnetic flux range, phiOFS0And the average value of the magnetic flux in the preset reference magnetic flux range.
The compensation module 133 is connected to the difference flux quantum number calculation module 132 and the first magnetic sensor 12, and is configured to compensate a part of the first sensing signal during the out-of-lock period according to a difference between a flux average value of each flux range and a flux average value of the preset flux range, so as to obtain a first sensing signal corresponding to a continuous change of the external flux.
The compensation module 133 can compensate for the part of the first sensing signal during the loss-of-lock period by using the existing signal compensation algorithm and the obtained differences, so as to obtain and output a high-precision first sensing signal corresponding to the continuous change of the external magnetic flux.
The working process of the superconducting quantum interference device magnetic sensing system 1 is as follows:
a second magnetic sensor 11 and a first magnetic sensor 12 in the same magnetic field environment simultaneously sense and respectively output a second sensing signal and a first sensing signal, wherein the sensing signal output by a second superconducting quantum interference device 111 in the second magnetic sensor 11 is negatively fed back by an under-feedback circuit 112 and then outputs a sensing signal with a period single-valued characteristic taking a working zero point as a starting point and an end point, a signal processing unit 113 in the second magnetic sensor 11 determines the amplitude of a digital waveform signal of a corresponding period according to the direction of each jump edge in the received sensing signal, generates a digital waveform signal according to the period of the received sensing signal, and superposes the received sensing signal and the generated digital waveform signal to obtain a second sensing signal reflecting the continuous change of the external magnetic flux;
meanwhile, the first superconducting quantum interference device 121 in the first magnetic sensor 12 outputs a discontinuous first sensing signal varying in a plurality of magnetic flux range ranges under the negative feedback action of the readout circuit;
the second magnetic sensor 11 and the first magnetic sensor 12 output the second sensing signal and the first sensing signal to the signal compensation processing unit 13, the subtraction processing module 131 in the signal compensation processing unit 13 converts the second sensing signal and the first sensing signal into the respective reflected magnetic fluxes, and performs subtraction operation to obtain the magnetic flux variation condition in each magnetic flux range, the difference magnetic flux quantum number calculating module 132 in the signal compensation processing unit 13 calculates the magnetic flux average value in each magnetic flux range output by the subtraction processing module 131, and determines the difference of the magnetic flux average value in each subsequent magnetic flux range with respect to the magnetic flux average value in the preset magnetic flux range with the magnetic flux average value in the first magnetic flux range as a reference, wherein each difference is rounded in a near-rounding manner, then, the compensation module 133 in the signal compensation processing unit 13 compensates the part of the first induced signal during the lock-out period by using the existing signal compensation algorithm and the differences obtained by the difference flux quantum number calculation module 132, and finally obtains the first induced signal which has the accuracy similar to the external magnetic flux of the superconducting quantum interference device and continuously changes. Superconductive quantum interferometer magnetic sensing system 1 can be long-time record inductive signal of high accuracy.
To sum up, the utility model discloses a superconductive quantum interferometer magnetic sensing system utilizes lower precision and can respond to the second magnetic sensor that continuous magnetic flux changes for a long time and provide the second sensing signal, utilize the first magnetic sensor that contains superconductive quantum interference device that the high accuracy is nevertheless unable to respond to continuous magnetic flux changes for a long time to provide first sensing signal, recycle the difference of second sensing signal and first sensing signal and come to the discontinuous part in the first sensing signal (lose the lock period promptly) the compensation estimation, can convert the first sensing signal of high accuracy into continuous signal by discontinuous signal, and then realize that superconductive quantum interference device is in the continuous measurement high-accuracy sensing signal of a plurality of hours time of even more of a specified duration, data material for the accurate magnetic signal of follow-up data analysis collection.
Further, because the precision difference that the precision of magnetic sensor under present normal atmospheric temperature was compared in superconductive quantum interference ware magnetic sensor is great, in order to ensure superconductive quantum interference ware magnetic sensing system's precision can be analogized in superconductive quantum interference device's precision, the utility model also provides a contain superconductive quantum interference device and can respond to the second magnetic sensor that the magnetic flux changes for a long time in succession.
Firstly, utilize the periodic characteristic that under feedback circuit changes the induction signal that second superconducting quantum interference device exported to realize the periodic single value output of induction signal in a magnetic flux quantum change cycle, and in a plurality of magnetic flux quantum change cycles of continuous variation, present if the magnetic flux increases a change cycle, induction signal has a lower jumping edge, if the magnetic flux reduces a change cycle, induction signal has the characteristic of an upper jumping edge, so, superconducting quantum interference ware magnetic sensor can measure and need not to carry out work zero point locking in the span range of a plurality of magnetic flux quantum change cycles, can effectively increase superconducting quantum interference device sensor magnetic measurement time and range.
In addition, the combination of the proportional amplifier and the feedback inductor or the combination of the magnetic flux amplification loop and the feedback inductor can realize the functions of amplifying the induction signal induced by the second superconducting quantum interference device in proportion and performing negative feedback, so that the periodical single-valued property of the induction signal can be effectively realized.
In addition, in order to ensure that the sensor can generate a jump at the end of each flux quantum change period, a technician can realize the formula requirements which are respectively met by the flux feedback coefficient of the under-feedback circuit, the feedback characteristic of the under-feedback circuit and the flux voltage transmission characteristic of the second superconducting quantum interference device by adjusting a feedback resistor, a bias circuit and the like in the sensor, and the realization mode is extremely simple and convenient. Therefore, the utility model effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles and effects of the present invention, and are not to be construed as limiting the invention. Modifications and variations can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A superconducting quantum interference device magnetic sensing system, comprising:
the first magnetic sensor comprises a first superconducting quantum interference device and is used for adjusting the locking working point of the first superconducting quantum interference device in real time, and inducing and outputting a first induction signal corresponding to the change of the external magnetic flux within a magnetic flux range after each locking;
the second magnetic sensor is positioned in the same external magnetic flux environment as the first magnetic sensor and is used for sensing and outputting a second sensing signal corresponding to the continuous change of the external magnetic flux in the magnetic flux environment;
and the signal compensation processing unit is connected with the second magnetic sensor and the first magnetic sensor and used for respectively determining the magnetic fluxes reflected by the first induction signal and the second induction signal by utilizing a preset magnetic field magnetic flux conversion coefficient, calculating the difference between the two magnetic fluxes, determining the quantity of magnetic flux quanta of the magnetic flux in each magnetic flux range relative to the preset magnetic flux range according to the obtained difference, compensating the change of the first induction signal in the unlocking period according to the obtained quantity of each relative magnetic flux, and outputting the compensated continuous first induction signal.
2. The superconducting quantum interference device magnetic sensing system of claim 1, wherein the second magnetic sensor comprises:
a second superconducting quantum interference device;
an under-feedback circuit connected to the second superconducting quantum interference device and negatively feeding back the induced signal induced by the second superconducting quantum interference device to the second superconducting quantum interference device, wherein the under-feedback circuit is configured to amplify the induced signal induced by the second superconducting quantum interference device according to a preset proportion and then negatively feed back the amplified induced signal to the second superconducting quantum interference device, so that the induced signal fed back by the second superconducting quantum interference device is output in a cycle single-value characteristic, the fed back induced signal is at a working zero point at the beginning of each magnetic flux quantum change period contained in the external magnetic flux, and the output induced signal jumps from a peak value to the working zero point at the end of the magnetic flux quantum change period;
and the signal processing unit is connected with the output end of the second superconducting quantum interference device and used for determining the amplitude of the digital waveform signal of each magnetic flux quantum change period according to the direction of each jump in the induction signal induced by the second superconducting quantum interference device and generating the digital waveform signal so as to count the amplitude as an integral multiple of the magnetic flux quantum, and superposing the received induction signal and the generated digital waveform to obtain the induction signal reflecting the external magnetic flux during the integral multiple change of the continuous magnetic flux quantum.
3. The superconducting quantum interference device magnetic sensing system of claim 2, wherein the under-feedback circuit comprises:
the amplifying unit is used for amplifying the induction signal induced by the second superconducting quantum interference device according to a preset proportion;
and the feedback resistor and the feedback inductor are sequentially connected with the second superconducting quantum interference device.
4. The superconducting quantum interference device magnetic sensing system of claim 3, wherein the amplifying unit is a proportional amplifier connected to the second superconducting quantum interference device;
the feedback resistor is connected with the output end of the proportional amplifier, the feedback inductor is connected with the feedback resistor, and the second superconducting quantum interference device is mutually inductive.
5. The superconducting quantum interference device magnetic sensing system of claim 4, wherein the second superconducting quantum interference device outputs an under-fed sensing signal through an output of the proportional amplifier.
6. The superconducting quantum interference device magnetic sensing system of claim 3, wherein the amplification unit comprises: a flux amplification circuit in mutual inductance connection with the second superconducting quantum interference device, the flux amplification circuit comprising: an inductor L mutually inductive with the second superconducting quantum interference deviceaAnd a feedback inductor L which is mutually inductive with the feedback inductoraThird superconducting quantum interference device connected in series, third superconducting quantum interference device and inductor LaParallel resistor Rb22And a DC flux regulating circuit mutually inducted with the third superconducting quantum interference device;
the feedback resistor is connected with the second superconducting quantum interference device, and the feedback inductor is connected with the feedback resistor;
and the connection end of the feedback resistor and the second superconducting quantum interference device is also connected with the output end of the second superconducting quantum interference device.
7. The superconducting quantum interference device magnetic sensing system of claim 2, wherein the signal processing unit comprises:
the analog-to-digital converter is connected with the output end of the second superconducting quantum interference device;
a counting waveform generator connected to the analog-to-digital converter, configured to generate a digital waveform signal according to a period of the digitized sensing signal sensed by the second superconducting quantum interference device and a transition direction of the sensing signal, where an amplitude of a current digital waveform signal is increased by one magnetic flux quantum when the received sensing signal is a lower transition edge, and the amplitude of the current digital waveform signal is decreased by one magnetic flux quantum when the received sensing signal is an upper transition edge;
and the synthesizer is connected with the counting waveform generator and the analog-to-digital converter and is used for superposing the digitized induction signal and the generated digital waveform signal to obtain an induction signal which corresponds to the external magnetic flux and spans a plurality of magnetic flux quantum change periods.
8. The superconducting quantum interference device magnetic sensing system of claim 2, wherein the superconducting quantum interference device magnetic sensor further comprises: a first bias circuit providing an adjustable bias current to the second superconducting quantum interference device.
9. The superconducting quantum interference device magnetic sensing system of claim 6, wherein the superconducting quantum interference device magnetic sensor further comprises: a first bias circuit to provide an adjustable bias current to the second superconducting quantum interference device, and a second bias circuit to provide an adjustable bias current to the first superconducting quantum interference device.
10. The superconducting quantum interference device magnetic sensing system of claim 1, wherein the signal compensation processing unit comprises:
the subtraction processing module is connected with the second magnetic sensor and the first magnetic sensor and used for converting the received first induction signal and the second induction signal into a first magnetic flux and a second magnetic flux respectively by taking a magnetic field and magnetic flux conversion coefficient of the first superconducting quantum interference device as a reference, and performing subtraction operation on the second magnetic flux and the first magnetic flux to obtain and output magnetic fluxes in each magnetic flux range;
the balance flux quantum number calculation module is connected with the subtraction processing module and is used for calculating the flux average value in each flux range output by the subtraction processing module and determining the balance of the flux average value in each remaining flux range relative to the flux average value in the preset flux range by taking the flux average value in the preset flux range as a reference;
and the compensation module is connected with the difference flux quantum number calculation module and is used for compensating the part of the first induction signal during the unlocking period according to the difference of the flux average value of each flux range relative to the flux average value of the preset flux range so as to obtain a first induction signal corresponding to the continuous change of the external flux.
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| CN104198962A (en) * | 2014-08-29 | 2014-12-10 | 中国科学院上海微***与信息技术研究所 | SQID (Superconducting Quantum Interference Device) magnetic sensor and working point jump identification method thereof |
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| CN104880680A (en) * | 2014-02-28 | 2015-09-02 | 中国科学院上海微***与信息技术研究所 | Superconducting quantum interference device magnetic sensing system |
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