A micro-superconducting non-contact current sensor based on superconducting quantum interference device
By using a miniature superconducting non-contact current sensor based on a superconducting quantum interference device, the problems of high internal resistance and alternating signal interference in the measurement of small currents have been solved, and high-precision, low-impedance and high-sensitivity current measurement has been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-02-14
- Publication Date
- 2026-03-17
AI Technical Summary
Existing technologies struggle to achieve high-precision measurement of minute current signals, especially current measurement in superconducting loops. Furthermore, traditional non-contact ammeters suffer from problems such as large size, high internal resistance, the introduction of parasitic impedance, and the generation of alternating signal interference to the circuit under test.
A miniature superconducting non-contact current sensor based on a superconducting quantum interference device is adopted, including a superconducting quantum interference device, a galvanometer probe, a room temperature amplifier circuit, a magnetic flux feedback excitation power supply, and a voltage signal reading device. Non-contact measurement is performed by using a magnetic flux pickup and feedback structure, and the induced current is canceled by the magnetic flux feedback excitation power supply, so as to achieve low impedance and high sensitivity measurement.
It achieves high-precision measurement of minute currents. The sensor is small in size and has low internal resistance. It does not generate alternating signal interference to the circuit under test and has high sensitivity and high practicality.
Smart Images
Figure CN116203302B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of current measurement, specifically relating to a miniature superconducting non-contact current sensor based on a superconducting quantum interference device. Background Technology
[0002] Many industrial and scientific experiments require high-precision measurements of minute current signals. Besides their small amplitude (<1mA), the current signals to be measured may also present challenges due to the low internal resistance of the equivalent current source in parallel. For example, if the goal is to measure the magnitude of a superconducting current flowing in a superconducting loop, the real part of the equivalent parallel internal resistance of the current source is 0Ω from an external perspective. This means that any resistance sampling-amplification galvanometer with a non-zero internal resistance, regardless of its sensitivity, cannot measure the magnitude of this current signal.
[0003] Non-contact Hall effect or fluxgate galvanometers can avoid the problem of internal resistance, but they are generally large in size, making it difficult to couple with tiny (<1mm) test structures. If a dedicated lead is provided for coupling with a fluxgate current sensor, the large size of the sensor will inevitably introduce a large inductive impedance, which is unacceptable for tiny test structures with an impedance of <100nH. Furthermore, fluxgate methods often require an alternating excitation signal to excite the core during operation, which inevitably affects the circuit under test, making it unacceptable in applications with low internal resistance and weak interference immunity.
[0004] In summary, there is still a lack of a microcurrent testing device with ultra-low internal resistance (0Ω real part, 100pH~100nH imaginary part), ultra-high sensitivity (<1pA), and no interference from alternating signals to the circuit under test. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a miniature superconducting non-contact current sensor based on a superconducting quantum interference device. By employing a miniature, superconducting non-contact current sensor, the invention solves the problems of large size, high internal resistance, and large parasitic impedance introduced by commercially available current sensors, sampling circuits, and non-contact current sensors.
[0006] To achieve the above objectives, the technical solution adopted by this invention is: a miniature superconducting non-contact current sensor based on a superconducting quantum interference device (QFID). The current sensor includes a QFID, a galvanometer probe, a room-temperature amplification circuit, a magnetic flux feedback excitation power supply, and a voltage signal reading device. The galvanometer probe includes a magnetic flux pickup structure, a magnetic flux feedback structure, an electrical contact point, and a substrate. The magnetic flux pickup structure of the galvanometer probe is connected to the QFID, and the magnetic flux feedback structure of the galvanometer probe is connected to the magnetic flux feedback excitation power supply. The QFID is connected to the room-temperature amplification circuit, and the room-temperature amplification circuit is connected to the voltage signal reading device. The magnetic flux pickup structure, magnetic flux feedback structure, and electrical contact point of the galvanometer probe are all integrated on the substrate. The QFID and the galvanometer probe are placed in a low-temperature environment together with the object under test. The magnetic flux pickup structure is close to the current-carrying wire of the object under test. The signal generated by the QFID is amplified by the room-temperature amplification circuit and then converted into a measured current value by a necessary conversion coefficient, which is then output by the voltage signal reading device.
[0007] Furthermore, the current sensor also applies an excitation current through the magnetic flux feedback excitation power supply to counteract the induced current in the magnetic flux coupling structure, and infers the magnitude of the current in the measured object through the current value applied by the magnetic flux feedback excitation power supply.
[0008] Furthermore, the flux pickup structure includes a superconducting flux pickup coil and a superconducting current-carrying conductive structure, with the conductive lines surrounding a known area.
[0009] Furthermore, the magnetic flux feedback structure includes a passive coil connected in series with the magnetic flux pickup structure and an active coil connected to the magnetic flux feedback excitation power supply, wherein the active coil and the passive coil have good magnetic flux coupling.
[0010] Furthermore, the electrical contact points include a first electrical contact point, a second electrical contact point, a third electrical contact point, and a fourth electrical contact point. The magnetic flux pickup structure is connected to the input contact of the superconducting quantum interference device through the first and second electrical contact points, and the active coil of the magnetic flux feedback structure is connected to the magnetic flux feedback excitation power supply through the third and fourth electrical contact points.
[0011] Furthermore, the magnetic flux pickup structure, the magnetic flux feedback structure, and the electrical contact point are made of materials that can enter the superconducting state at the operating temperature.
[0012] Furthermore, the magnetic flux pickup structure, the magnetic flux feedback structure, and the electrical contact points are made of Nb.
[0013] Furthermore, the superconducting quantum interference device includes a first input contact, a second input contact, a contact group connected to the room-temperature amplifier circuit, and a Josephson junction structure.
[0014] Furthermore, the low-temperature environment is below 4K.
[0015] Furthermore, the cryogenic environment is at least one of a cryogenic refrigerator, a liquid nitrogen Dewar jar, or a liquid helium Dewar jar.
[0016] The beneficial technical effects of this invention are as follows:
[0017] 1. Unlike clamp meters, which require clamping the sampling clamp onto the circuit under test and require a sufficiently long wire to be enclosed by the clamp, this invention discloses a high-sensitivity current sensor based on magnetic flux coupling. The object under test does not need to be large in size, the magnetic flux pickup structure is only about 10 to 500 μm in size, and it does not need to enclose the circuit under test.
[0018] 2. Compared to commercially available fA (femtoamp) meters, this invention has extremely high current sensitivity but very high internal resistance. Fluxgate galvanometers, like this invention, are non-contact measurement devices, but their larger iron cores introduce larger imaginary impedances, and their measurement methods can cause high-frequency interference to the circuit under test. The current sensor disclosed in this invention combines the advantages of non-contact, low impedance (including real and imaginary parts), and small size, making it highly practical and accurate. Attached Figure Description
[0019] Figure 1 This is a schematic diagram illustrating the connection between the magnetic flux pickup structure, the magnetic flux feedback structure, and the electrical contact point in a miniature superconducting non-contact current sensor based on a superconducting quantum interference device, as shown in an embodiment of the present invention.
[0020] Figure 2 This is a schematic diagram of the structure of a superconducting quantum interference device in a miniature superconducting non-contact current sensor based on a superconducting quantum interference device, as shown in an embodiment of the present invention.
[0021] Figure 3 This is a schematic diagram illustrating the working principle of a miniature superconducting non-contact current sensor based on a superconducting quantum interference device, as shown in an embodiment of the present invention.
[0022] Wherein: 1.1-First electrical contact point, 1.2-Second electrical contact point, 1.3-Third electrical contact point, 1.4-Fourth electrical contact point, 1.5-Fluid pickup structure, 1.6-Passive coil, 1.7-Active coil, 2.1-First input contact, 2.2-Second input contact, 2.3-Contact group, 2.4-Josephson junction structure. Detailed Implementation
[0023] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.
[0024] Example 1
[0025] SQUID (Superconducting Quantum Interference Device) utilizes the fact that the magnetic flux contained in a superconducting loop must be an integer number of magnetic flux quanta Φ0 = 2.067 × 10⁻⁶. -15 The properties of Wb allow for precise measurement of magnetic fields with a sensitivity of less than 10 μΦ0. A superconducting input coil can convert a current signal into a magnetic field signal. Conversely, the magnitude of the input current signal can be deduced from the magnitude of the magnetic field signal measured by the superconducting quantum interference device (SQUID). This invention discloses a miniature superconducting non-contact current sensor based on a superconducting quantum interference device, utilizing this method to achieve high-precision measurement of minute measured currents.
[0026] The aforementioned superconducting input coil is typically part of the internal structure of a superconducting quantum interference device and is exposed to the outside world through two input electrical contact points. The current signal directly obtained by the above method is not the measured current signal, but rather the induced current signal generated inside the flux pickup structure after the flux generated by the measured current signal is picked up by the flux pickup structure.
[0027] This invention provides a miniature superconducting non-contact current sensor based on a superconducting quantum interference device, comprising a superconducting quantum interference device, a galvanometer probe, a room temperature amplifier circuit, a magnetic flux feedback excitation power supply, and a voltage signal reading device.
[0028] The galvanometer probe includes a flux pickup structure, a flux feedback structure, electrical contacts, and a substrate.
[0029] The flux pickup structure includes a superconducting flux pickup coil and a superconducting current-carrying conductive structure. The flux pickup structure and the superconducting quantum interference device are installed in a cryogenic environment. The cryogenic environment can be a cryogenic refrigerator, liquid nitrogen, or a liquid helium Dewar flask, and the cryogenic environment is below 4K.
[0030] The flux pickup structure is connected to a superconducting quantum interference device (SQU), the flux feedback structure is connected to a flux feedback excitation power supply, the SQU is connected to a room-temperature amplifier circuit, and the room-temperature amplifier circuit is connected to a voltage signal reading device. All components of the flux pickup structure are fabricated on the substrate. The substrate can be part of the object under test (DUT) or exist independently of the DUT.
[0031] All components of the galvanometer probe reside on its substrate. In this example, the substrate is a 5mm x 5mm Si wafer, but it could also be an electronic substrate or other substrate suitable for fabricating planar multilayer circuits.
[0032] like Figure 1As shown, the flux pickup structure 1.5 should be a single-turn or multi-turn coil; in this embodiment, only a single-turn coil is used as an example. The characteristic of the flux pickup structure 1.5 is that the conductive lines surround a known area. The flux feedback structure consists of a passive coil 1.6 connected in series with the flux pickup structure and an active coil 1.7 connected to an external flux feedback excitation power supply. Good flux coupling should exist between the active and passive coils. The active and passive coils can be single-turn or multi-turn coils. The flux pickup structure is connected to the input contact of the superconducting quantum interference device through the first electrical contact point 1.1 and the second electrical contact point 1.2. The active coil 1.7 of the flux feedback structure is connected to the flux feedback excitation power supply through the third electrical contact point 1.3 and the fourth electrical contact point 1.4. The flux pickup structure, the flux feedback structure, and the electrical contacts should be made of materials capable of entering a superconducting state at the operating temperature, such as Nb.
[0033] like Figure 2 As shown, the superconducting quantum interference device includes a first input contact 2.1, a second input contact 2.2, a contact group 2.3 connected to the temperature amplifier circuit, and a Josephson junction structure 2.4.
[0034] The superconducting quantum interference device and galvanometer probe should be placed in a low-temperature environment together with the object being measured.
[0035] like Figure 3 As shown, in operation, the magnetic flux pickup structure is placed close to the current-carrying conductor of the object under test (DUT). The magnetic flux generated by the current in the DUT enters the magnetic flux coupling structure, producing an induced current signal, which then enters the superconducting quantum interference device (SQU). The signal generated by the SQU is amplified and shaped by a room-temperature amplifier circuit, and then converted into a measured current value by necessary conversion factors. This value is then output by a voltage signal reading device. If the measured current value exceeds the device's range, or if it is undesirable for the induced current generated in the magnetic flux coupling structure to affect the DUT, a known excitation current can be applied through the magnetic flux feedback excitation power supply to cancel the induced current in the magnetic flux coupling structure. In this case, the output value of the voltage signal reading device should be 0 or a small fixed value. At this point, the output of the voltage signal reading device no longer directly reflects the magnitude of the current in the DUT, but the magnitude of the current in the DUT can be inferred from the current value applied by the magnetic flux feedback excitation power supply.
[0036] In this invention, the superconducting quantum interference device (SQUID) is essentially a sensitive galvanometer. To achieve non-contact measurement, a probe is used to convert the magnetic flux generated by the current in the circuit under test into a current signal measured by the SQUID, which is then converted into the current value in the circuit under test. The probe also has a magnetic flux feedback structure. By applying a feedback electrical signal to the probe through a magnetic flux feedback excitation power supply, the induced current generated within the probe can be canceled out. This feedback structure, in addition to expanding the current measurement range of the device, also reduces the impedance (imaginary part) introduced by the device.
[0037] As can be seen from the above embodiments, the miniature superconducting non-contact current sensor based on a superconducting quantum interference device (SQU) disclosed in this invention includes a SQU, a galvanometer probe, a room-temperature amplification circuit, a magnetic flux feedback excitation power supply, and a voltage signal reading device. The galvanometer probe includes a magnetic flux pickup structure, a magnetic flux feedback structure, an electrical contact point, and a substrate. The magnetic flux pickup structure is connected to the SQU, and the magnetic flux feedback structure is connected to the magnetic flux feedback excitation power supply. The SQU is connected to the room-temperature amplification circuit, which is connected to the voltage signal reading device. The magnetic flux pickup structure is close to the current-carrying wire of the object being measured. The signal generated by the SQU is amplified by the room-temperature amplification circuit, converting the output voltage signal into the measured current value and outputting it. Using the current sensor disclosed in this invention, there is no alternating signal interference to the measured circuit. It has technical advantages such as compact structure, low internal resistance, high sensitivity, strong practicality, and high measurement accuracy, laying a reliable foundation for high-precision measurement of minute current signals.
[0038] The device described in this invention is not limited to the embodiments described in the specific implementation. Other implementation methods derived by those skilled in the art based on the technical solution of this invention also fall within the scope of technical innovation of this invention.
Claims
1. A micro-superconducting non-contact current sensor based on a superconducting quantum interference device, characterized by: The current sensor comprises a superconducting quantum interference device, a current meter probe, a room temperature amplification circuit, a magnetic flux feedback excitation power supply and a voltage signal reading device, the current meter probe comprises a magnetic flux pickup structure, a magnetic flux feedback structure, an electrical contact point and a substrate, the magnetic flux pickup structure of the current meter probe is connected with the superconducting quantum interference device, the magnetic flux feedback structure of the current meter probe is connected with the magnetic flux feedback excitation power supply, the superconducting quantum interference device is connected with the room temperature amplification circuit, the room temperature amplification circuit is connected with the voltage signal reading device, the magnetic flux pickup structure, the magnetic flux feedback structure and the electrical contact point of the current meter probe are integrated on the substrate, the superconducting quantum interference device and the current meter probe are placed in a low-temperature environment together with a measured object, the magnetic flux pickup structure is close to a current-carrying conductor of the measured object, after the signal generated by the superconducting quantum interference device passes through the room temperature amplification circuit, the output voltage signal is converted into a measured current value through a necessary conversion coefficient, and the voltage signal reading device outputs; the magnetic flux pickup structure does not need to surround the measured circuit, and only surrounds a known area, the magnetic flux pickup structure comprises a superconducting magnetic flux pickup coil and a superconducting current-carrying conductive structure; the magnetic flux feedback structure comprises a passive coil connected in series with the magnetic flux pickup structure and an active coil connected with the magnetic flux feedback excitation power supply, and the active coil and the passive coil have good magnetic flux coupling; when the measured current value exceeds the equipment range or the induced current generated in the magnetic flux coupling structure affects the measured object, the current sensor further applies an excitation current through the magnetic flux feedback excitation power supply to offset the induced current in the magnetic flux coupling structure, and the current value applied by the magnetic flux feedback excitation power supply is used to infer the current size in the measured object.
2. A micro-SQUID based superconducting non-contact current sensor according to claim 1, wherein: The electrical contact point comprises a first electrical contact point, a second electrical contact point, a third electrical contact point and a fourth electrical contact point, the magnetic flux pickup structure is connected with the input contact point of the superconducting quantum interference device through the first electrical contact point and the second electrical contact point, and the active coil of the magnetic flux feedback structure is connected with the magnetic flux feedback excitation power supply through the third electrical contact point and the fourth electrical contact point.
3. A micro-superconducting non-contact current sensor based on a superconducting quantum interference device as claimed in claim 2, characterized in that: The magnetic flux pickup structure, the magnetic flux feedback structure and the electrical contact point are made of a material capable of entering a superconducting state at a working temperature.
4. A micro-superconducting non-contact current sensor based on a superconducting quantum interference device as claimed in claim 3, characterized in that: The magnetic flux pickup structure, the magnetic flux feedback structure and the electrical contact point are made of Nb.
5. A micro-SQUID-based superconducting non-contact current sensor according to claim 1, wherein: The superconducting quantum interference device comprises a first input contact point, a second input contact point, a contact group connected with the room temperature amplification circuit and a Josephson junction structure.
6. A micro-SQUID-based superconducting non-contact current sensor according to claim 1, wherein: The low-temperature environment is below 4 K.
7. A micro-SQUID-based superconducting non-contact current sensor according to claim 1, wherein: The low-temperature environment is at least one of a low-temperature refrigerator, a liquid nitrogen Dewar flask or a liquid helium Dewar flask.
Citation Information
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