High-precision digital AC bridge and its quantum resistance transfer method

Abstract

A high-precision digital AC bridge and its quantum resistance transfer method include: an adjustable signal source, a power inductive voltage divider, a Wagner balanced branch, a first current injection combined network, a second current injection combined network, a multi-stage inductive voltage divider, a Kelvin balanced branch, a standard resistor, and a measuring resistor; wherein, the Kelvin balanced branch includes a voltage injection signal source and a digital measurement and acquisition module; the number of turns of each winding of the multi-stage inductive voltage divider is adjusted so that the ratio of the voltage across the standard resistor to the voltage across the resistor under test is 10. ‑5 The invention addresses the issues of lead wire error, contact resistance error, and external interference, improving the accuracy of value transfer. It involves adjusting the first and second voltages injected into the standard resistor and the resistor under test by the voltage injection signal source to ensure they are equal; measuring the differential current in the balanced branch; and incorporating this differential current as a compensation quantity into the quantum resistance transfer.

Description

Technical Field

[0001] This invention belongs to the field of metrology equipment technology, specifically relating to a high-precision digital AC bridge and its quantum resistance transfer method. Background Technology

[0002] Metrology is the cornerstone of scientific and technological development. With the advancement of measurement and control technology, high-precision resistors play a vital role in scientific research and manufacturing across various fields. Resistors possess frequency characteristics, and in high-frequency circuits, they are affected by parasitic inductance, parasitic capacitance, and proximity effects, leading to deviations between the resistance value reproduced by high-precision resistors and the frequency. Currently, AC resistance metrology standards have not been replaced by quantum metrology standards. Due to the complex and strong magnetic environment in which quantized Hall resistors operate, AC traceability is extremely difficult.

[0003] Existing technologies utilize cutting-edge measurement techniques such as cryogenic current comparators and superconducting flux interferometers to achieve high-precision value transfer of quantized Hall resistors. However, these advanced technologies require maintaining phase stability and consistency during the transfer process, making them unsuitable for high-frequency circuits.

[0004] Furthermore, the resistance value of a quantized Hall resistor depends only on physical constants, exhibiting very high accuracy and stability. However, this resistance value is a series of non-integer values ​​with quantized characteristics. Since standard resistors with resistance values ​​in multiples of ten are mostly used in resistance value transfer, the two impedances are not integers when compared. This results in a slight potential difference in the comparison branch, leading to errors in traditional AC bridge circuits due to this slight potential difference. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-precision digital AC bridge and its quantum resistance transfer method. The AC bridge connection uses a four-terminal pair defined connection to solve the problems of lead wire error, contact resistance error and external interference, thereby improving the accuracy of value transfer.

[0006] The present invention proposes the following technical solution.

[0007] This invention proposes a high-precision digital AC bridge, comprising:

[0008] Adjustable signal source, power inductive voltage divider, Wagner balanced branch, first current injection combined network, second current injection combined network, multi-stage inductive voltage divider, Kelvin balanced branch, standard resistor and measuring resistor; wherein, the Kelvin balanced branch includes voltage injection signal source and digital measurement and acquisition module.

[0009] An adjustable signal source is connected to the primary side of a power inductive voltage divider. The secondary side of the power inductive voltage divider has four taps: a secondary first tap, a secondary first tap, a secondary second tap, and a secondary last tap. One end of the Wagner balance branch is connected to the secondary first tap of the power inductive voltage divider and the other end of a standard resistor. The other end of the Wagner balance branch is connected to the secondary second tap of the power inductive voltage divider and the other end of the resistor under test. The input of the first current injection combination network is connected in parallel between the secondary first tap and the secondary first tap of the power inductive voltage divider, and the output of the first current injection combination network is connected to the other end of the standard resistor. The input of the second current injection combination network is connected in parallel between the secondary second tap and the secondary last tap of the power inductive voltage divider, and the output of the second current injection combination network is connected to the other end of the resistor under test.

[0010] The multi-stage inductive voltage divider includes five cascaded windings. The input terminal of the first-stage winding is connected to one end of the Wagner balance branch and the other end of the standard resistor. The output terminal of the first-stage winding is connected to the other end of the Wagner balance branch and the other end of the resistor to be measured. The output terminal of the fifth-stage winding is connected to the input terminal of the digital measurement and acquisition module.

[0011] A voltage injection signal source injects a first voltage into one end of a standard resistor and a second voltage into one end of the resistor under test. One end of the standard resistor is connected to one end of the resistor under test. A digital measurement and acquisition module acquires the difference between the first voltage and the second voltage.

[0012] It also includes: a power amplifier; an adjustable signal source connected to the primary side of a power inductive voltage divider via the power amplifier.

[0013] The input terminal of the first winding of the multi-stage inductive voltage divider is connected to the other end of the standard resistor to form a high-potential branch; the output terminal of the first winding of the multi-stage inductive voltage divider is connected to the other end of the resistor to be measured to form a low-potential branch; the output terminal of the fifth winding of the multi-stage inductive voltage divider is connected to the input terminal of the digital measurement and acquisition module to form a balanced branch.

[0014] The adjustable signal source provides current to the standard resistor and the resistor under test through the first current injection combination network and the second current injection combination network, respectively, so that there is no current in the high potential branch and the low potential branch.

[0015] An adjustable signal source is connected in parallel with the Wagner balance branch to achieve power balance of the digital AC bridge, and the Wagner balance branch regulates the leakage current in the balance branch.

[0016] The circuit topologies of the Wagner balanced branch, the first current injection combined network, and the second current injection combined network are the same, all including: an inductively coupled ratio arm and two-terminal impedances.

[0017] It also includes: a first null pointer, a second null pointer, and a third null pointer; the first null pointer is connected to the high-potential branch, the second null pointer is connected to the balanced branch, and the third null pointer is connected to the low-potential branch; each null pointer includes an inductive coupling ratio arm;

[0018] When the null pointer points to zero, it indicates that the current in the corresponding branch is zero, signifying that the Wagner balance branch, the first current injection combination network, and the second current injection combination network have completed the adjustment of the current in the corresponding branch.

[0019] The digital measurement and acquisition module includes: a voltage-current analog-to-digital converter chip and a follower;

[0020] The follower output is connected to the output of the fifth winding of the multi-stage inductive voltage divider through a balanced branch. The voltage-current analog-to-digital converter chip is connected to the balanced branch and is connected between the output of the fifth winding of the multi-stage inductive voltage divider and the follower.

[0021] The digital measurement and acquisition module also includes: a first single-pole double-throw analog switch, a second single-pole double-throw analog switch, and a third single-pole double-throw analog switch;

[0022] The common port of the first single-pole double-throw analog switch is connected to one end of a standard resistor, and the normally closed port is connected to a matching impedance; the normally open port of the first single-pole double-throw analog switch is connected to the normally closed port of the second single-pole double-throw analog switch; the common port of the second single-pole double-throw analog switch is connected to the input terminal of the follower, and the normally open port of the second single-pole double-throw analog switch is connected to the normally open port of the third single-pole double-throw analog switch; the common port of the third single-pole double-throw analog switch is connected to one end of the resistor to be measured, and the normally closed port of the third single-pole double-throw analog switch is connected to a matching impedance;

[0023] Both the first and third single-pole double-throw analog switches are normally closed.

[0024] Switch the first single-pole double-throw analog switch to the normally open port, and keep the second single-pole double-throw analog switch in the normally closed state. The voltage-current analog-to-digital converter chip measures the first voltage. Switch the third single-pole double-throw analog switch to the normally open port, and switch the second single-pole double-throw analog switch to the normally open port. Measure the second voltage. When the first voltage and the second voltage are not equal, adjust the voltage and frequency output by the voltage injection signal source until the first voltage and the second voltage are equal.

[0025] It also includes: ten sets of chokes; the chokes are connected to each branch of the bridge.

[0026] Each branch includes: the connection branch between the first current injection combined network and the secondary first tap of the power inductive voltage divider; the connection branch between the second current injection combined network and the secondary last tap of the power inductive voltage divider; the connection branch between the input terminal of the first winding of the multi-stage inductive voltage divider and the first secondary tap of the power inductive voltage divider; the connection branch between the output terminal of the first winding of the multi-stage inductive voltage divider and the second secondary tap of the power inductive voltage divider; a high-potential branch; a low-potential branch; the connection branch between the other end of the standard resistor and the output terminal of the first current injection combined network; the connection branch between the other end of the resistor under test and the output terminal of the first current injection combined network; the connection branch between the first output terminal of the Kelvin balance branch and one end of the standard resistor; and the connection branch between the second output terminal of the Kelvin balance branch and one end of the resistor under test.

[0027] The adjustable signal source is connected in parallel with the first current injection combination network and the second current injection combination network. The adjustable signal source provides current to the standard resistor and the resistor under test through the first current injection combination network and the second current injection combination network, respectively, so as to achieve no current in the high potential branch and the low potential branch. At the same time, the adjustable signal source is connected in parallel with the Wagner balance branch to realize the power supply balance of the digital AC bridge, which is used to adjust the leakage current in the balance branch.

[0028] Adjust the number of turns in each stage of the multi-stage inductive voltage divider so that the ratio of the voltage across the standard resistor to the voltage across the resistor under test is 10. -5 Order of magnitude;

[0029] Adjust the first and second voltages injected by the voltage injection signal source into the standard resistor and the resistor under test, so that the first and second voltages are equal;

[0030] The differential current in the balanced branch is measured and incorporated into the quantum resistance transfer as a compensation quantity.

[0031] The beneficial effects of this invention are that, compared with the prior art, the high-precision digital AC bridge proposed in this invention can realize high-precision value transfer of quantum Hall resistors under high-frequency AC signals. It is suitable for transferring values ​​of quantum Hall resistors to standard resistors with different resistance ratios, with a measurement range of 100Ω to 10kΩ and an uncertainty level of 10. -7 .

[0032] This invention incorporates a Kelvin balancing branch, a Wagner balancing branch, and a current injection combination network to overcome the effects of lead voltage drop between the two impedances and the leakage current of the bridge capacitor. A multi-stage inductive voltage divider is used as the main comparator circuit, converting the voltage division ratio of the resistors into the turns ratio of the multi-stage inductive voltage divider through a high-precision voltage division ratio, enabling rapid balancing and simplifying the value transfer calculation. A high-resolution, high-sensitivity, and high-precision voltage-current analog-to-digital converter chip is innovatively introduced to measure the minute difference current in the comparator circuit, which is then used as voltage compensation in the value transfer calculation, greatly improving the accuracy of value transfer. Attached Figure Description

[0033] Figure 1 This is a structural diagram of the high-precision digital AC bridge proposed in this invention;

[0034] Figure 1 The annotations in the accompanying drawings are explained as follows:

[0035] 1-Adjustable signal source, 2-Power inductive voltage divider, 3-Power amplifier, 4-Wagner balanced branch, 5a-First current injection combination network, 5b-Second current injection combination network, 6-Multi-stage inductive voltage divider, 7a-First null pointer, 7b-Second null pointer, 7c-Third null pointer, 9-Voltage injection signal source, 10-Choke, 11-First single-pole double-throw analog switch, 12-Second single-pole double-throw analog switch, 13-Third single-pole double-throw analog switch, 14-Voltage-current analog-to-digital converter chip, 15-Follower;

[0036] Figure 2 This is a circuit diagram of a multi-stage inductive voltage divider in an embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0038] This invention proposes a high-precision digital AC bridge, such as... Figure 1 As shown, it includes: an adjustable signal source 1, a power inductive voltage divider 2, a power amplifier 3, a Wagner balanced branch 4, a first current injection combination network 5a, a second current injection combination network 5b, a multi-stage inductive voltage divider 6, a first null indicator 7a, a second null indicator 7b, a third null indicator 7c, a Kelvin balanced branch, a standard resistor R0, a resistor under test R1, and ten sets of chokes. The Kelvin balanced branch includes: a voltage injection signal source 9 and a digital measurement and acquisition module.

[0039] The standard resistor is the quantum Hall resistor.

[0040] The adjustable signal source is connected to the primary side of the power inductive voltage divider, and the Wagner balanced branch is connected in parallel to the secondary side of the power inductive voltage divider.

[0041] Specifically, the adjustable signal source is connected to the primary side of the power inductive voltage divider via a power amplifier. The secondary side of the power inductive voltage divider has four taps: a secondary first tap, a secondary first tap, a secondary second tap, and a secondary last tap. The Wagner balance branch is connected in parallel between the secondary first tap and the secondary second tap of the power inductive voltage divider. The input of the first current injection combination network is connected in parallel between the secondary first tap and the secondary first tap of the power inductive voltage divider, and the input of the second current injection combination network is connected in parallel between the secondary second tap and the secondary last tap of the power inductive voltage divider. This ensures that the Wagner balance branch, the first current injection combination network, and the second current injection combination network are all connected in parallel with the adjustable signal source.

[0042] Specifically, one end of the Wagner balance branch is connected to the second secondary tap of the power inductive voltage divider and the other end of the standard resistor, and the other end of the Wagner balance branch is connected to the second secondary tap of the power inductive voltage divider and the other end of the resistor under test; the output of the first current injection combination network is connected to the other end of the standard resistor, and the output of the second current injection combination network is connected to the other end of the resistor under test.

[0043] In this embodiment, the adjustable signal source is an adjustable current source; the power inductive voltage divider is an autotransformer with a total of 100 turns in its winding, and the secondary side of the power inductive voltage divider has 4 taps; the circuit topologies of the Wagner balance branch, the first current injection combination network, and the second current injection combination network are the same, all including: an inductive coupling ratio arm and two-terminal impedance.

[0044] The multi-stage inductive voltage divider includes five cascaded windings. The input terminal of the first-stage winding is connected to one end of the Wagner balance branch and the other end of the standard resistor to achieve voltage transmission. The output terminal of the first-stage winding is connected to the other end of the Wagner balance branch and the other end of the resistor to be measured. The output terminal of the fifth-stage winding is connected to the input terminal of the digital measurement and acquisition module.

[0045] The input terminal of the first winding of the multi-stage inductive voltage divider is connected to the other end of the standard resistor to form a high-potential branch; the output terminal of the first winding of the multi-stage inductive voltage divider is connected to the other end of the resistor to be measured to form a low-potential branch; the output terminal of the fifth winding of the multi-stage inductive voltage divider is connected to the input terminal of the digital measurement and acquisition module to form a balanced branch.

[0046] This invention connects an adjustable signal source in parallel with a first current injection combination network and a second current injection combination network. The adjustable signal source provides current to the standard resistor and the resistor under test through the first and second current injection combination networks, respectively, achieving no current in the high-potential branch and the low-potential branch. This eliminates the voltage drop caused by the presence of current in the branch and improves the quantum resistance transfer accuracy. At the same time, the adjustable signal source is connected in parallel with the Wagner balance branch to achieve power balance of the digital AC bridge, which is used to adjust the leakage current in the balance branch and solve the problem of quantum resistance transfer accuracy caused by the voltage drop due to leakage current.

[0047] Specifically, the first null indicator is connected to the high-potential branch, the second null indicator is connected to the balanced branch, and the third null indicator is connected to the low-potential branch. When the null indicator points to zero, it indicates that the current in the corresponding branch is zero, signifying that the Wagner balanced branch, the first current injection combination network, and the second current injection combination network have completed the current adjustment on the corresponding branch. Each null indicator includes an inductive coupling ratio arm.

[0048] Specifically, such as Figure 2 As shown, each stage of the multi-stage inductive voltage divider has 11 turns. For the 2nd to 4th stages, the output terminal of the previous stage is connected to the input terminal of the next stage, forming a cascaded connection. In the embodiment, when the input voltage is U, the output voltage is changed to U by altering the position of the connection taps between stages. out =0.4297U The ratio of output voltage to input voltage is a ten-thousandths level ratio, which is a high-precision ratio and a rational decimal.

[0049] This invention employs a multi-stage inductive voltage divider as the main comparator circuit. The mutual inductance between the windings of each stage in the multi-stage inductive voltage divider achieves layer-by-layer voltage division. By adjusting the number of turns in each winding of the multi-stage inductive voltage divider, the voltage between the standard resistor and the resistor under test is adjusted to a preliminary equilibrium state, achieving a voltage drop of 10... -5 The ratio of winding turns is used to represent the ratio of the voltage across the standard resistor to the voltage across the resistor under test, thus achieving Wagner balance.

[0050] Specifically, the multi-stage inductive voltage divider uses a microcrystalline material with high permeability, high stability, and high resistivity as its magnetic core. A twelve-strand strand of enameled copper wire, laid flat and rotated around the central core, is used as the wire and wound onto an insulating and fixing device made of ABS material.

[0051] The output terminal of the fifth winding of the multi-stage inductive voltage divider is connected to the input terminal of the digital measurement and acquisition module. The first and second output terminals of the digital measurement and acquisition module are respectively connected to one end of the standard resistor R0 and one end of the resistor to be measured R1. The voltage injection signal source injects a first voltage V0 into one end of the standard resistor. LA voltage injection signal source injects a second voltage V1 into one end of the resistor under test. H One end of the standard resistor is connected to one end of the resistor to be measured; the digital measurement and acquisition module acquires the difference between the first voltage and the second voltage.

[0052] The digital measurement and acquisition module includes a host computer (PC), a voltage-current analog-to-digital converter chip (14), a follower (15), a first single-pole double-throw analog switch (11), a second single-pole double-throw analog switch (12), and a third single-pole double-throw analog switch (13).

[0053] Specifically, the follower output is connected to the output of the fifth winding of the multi-stage inductive voltage divider through a balanced branch, and the voltage-current analog-to-digital converter chip is connected to the balanced branch to measure the differential current present in the balanced branch.

[0054] Specifically, the voltage-current analog-to-digital converter chip is connected between the output terminal of the fifth winding of the multi-stage inductive voltage divider and the follower. That is, the follower is located in front of the voltage-current analog-to-digital converter chip, which can match the impedance of the input signal and play the roles of buffering, isolation, and amplification of gain, thereby improving the measurement accuracy of the voltage-current analog-to-digital converter chip.

[0055] Specifically, the common port of the first single-pole double-throw analog switch is connected to one end of a standard resistor, and its normally closed port is connected to a matching impedance to prevent bridge potential fluctuations when the first single-pole double-throw analog switch switches signals; the normally open port of the first single-pole double-throw analog switch switches is connected to the normally closed port of the second single-pole double-throw analog switch switches; the common port of the second single-pole double-throw analog switch switches is connected to the input terminal of the follower, and the normally open port of the second single-pole double-throw analog switch switches is connected to the normally open port of the third single-pole double-throw analog switch switches; the common port of the third single-pole double-throw analog switch switches is connected to one end of the resistor under test, and the normally closed port of the third single-pole double-throw analog switch switches is connected to a matching impedance to prevent bridge potential fluctuations when the third single-pole double-throw analog switch switches signals.

[0056] Specifically, both the first single-pole double-throw analog switch and the third single-pole double-throw analog switch are normally closed to prevent bridge potential fluctuations when the analog switches switch signals.

[0057] Specifically, the first single-pole double-throw analog switch is switched to the normally open port, while the second single-pole double-throw analog switch remains in the normally closed state. The voltage-current analog-to-digital converter chip measures the first voltage V0. L Switch the third single-pole double-throw analog switch to the normally open port, switch the second single-pole double-throw analog switch to the normally open port, and measure the second voltage V1. H When the first voltage and the second voltage are not equal, adjust the voltage and frequency of the voltage injected signal source until the first voltage and the second voltage are equal, thus completing the Kelvin balance.

[0058] After Wagner balancing, the voltage ratio between the standard resistor and the resistor under test is 10. -5 On the order of magnitude, Kelvin balancing is performed to make the first voltage and the second voltage equal. At this time, there is a slight difference current in the balancing branch. The slight difference current is measured by a voltage-current analog-to-digital converter chip and incorporated into the quantum resistor transfer as a compensation quantity to solve the problem of low accuracy of traditional inductive voltage divider AC bridge.

[0059] In the high-precision digital AC bridge proposed in this invention, the Kelvin balancing branch is connected to both ends of the connection line between the standard resistor and the resistor under test. Due to the current in the bridge loop, a voltage difference exists between the two ends of the connection line. Through the switching and coordination of three single-pole double-throw analog switches, the digital measurement and acquisition module acquires the voltage difference between the two ends of the connection line between the standard resistor and the resistor under test. The voltage injected into the standard resistor and the resistor under test is adjusted using a voltage injection signal source. After Kelvin balancing adjustment, the voltage difference between the two ends of the connection line is reduced to 0, thereby improving the measurement accuracy through Kelvin balancing. At this time, the digital measurement and acquisition module measures the differential current; the differential current is used as a compensation current and incorporated into the quantum resistance transfer calculation, thereby obtaining a high-precision voltage division ratio between the quantum Hall resistance and the resistor under test. The high uncertainty level of the quantum Hall resistance is completely transferred to the resistor under test, thus solving the problem of low accuracy in traditional inductive voltage divider AC bridges.

[0060] Specifically, the digital measurement and acquisition module also includes: an STM32 lower-level machine; the STM32 lower-level machine performs analog switching circuit switching and voltage and current analog-to-digital conversion chip acquisition and measurement according to the instructions issued by the upper-level machine.

[0061] Specifically, the voltage analog-to-digital converter chip has a measurement accuracy of 24 bits, and the voltage analog-to-digital converter chip has a measurement accuracy of 22 bits. After converting the voltage signal and current signal into digital signals, they are sampled and transmitted to the host computer, with a sampling frequency of over 200kS / s.

[0062] This invention incorporates a digital acquisition and measurement module into the comparison process between a quantum Hall resistor and a standard resistor. It utilizes a high-precision, high-sensitivity voltage-to-current analog-to-digital converter chip to rapidly measure the minute differential potential present in the comparison circuit after initial balancing. This solves the problem that traditional value transfer methods can only compare two AC resistors with an integer ratio. Furthermore, by incorporating the obtained minute differential potential value as compensation into the value transfer calculation, the accuracy of value transfer is further improved, achieving an uncertainty level of 10. -7 .

[0063] Specifically, the voltage injection signal source includes: an adjustable voltage source and an injection transformer.

[0064] Chokes are connected to each branch of the bridge circuit to ensure that the current in the cores of the coaxial lines with non-directional structures is equal in magnitude and opposite in direction. Each branch includes: the branch connecting the first current injection combination network to the secondary first tap of the power inductive voltage divider; the branch connecting the second current injection combination network to the secondary last tap of the power inductive voltage divider; the branch connecting the input terminal of the first winding of the multi-stage inductive voltage divider to the first secondary tap of the power inductive voltage divider; the branch connecting the output terminal of the first winding of the multi-stage inductive voltage divider to the second secondary tap of the power inductive voltage divider; a high-potential branch; a low-potential branch; the branch connecting the other end of the standard resistor to the output terminal of the first current injection combination network; the branch connecting the other end of the resistor under test to the output terminal of the first current injection combination network; the branch connecting the first output terminal of the Kelvin balance branch to one end of the standard resistor; and the branch connecting the second output terminal of the Kelvin balance branch to one end of the resistor under test.

[0065] The high-precision digital AC bridge proposed in this invention adopts a four-terminal pair definition structure and combines multiple compensation networks with shielding structures to reduce the influence of cable resistance and contact resistance, while fully avoiding the influence of the complex strong magnetic environment in which the quantum Hall resistor is located, thereby improving the accuracy of AC quantum Hall resistor value transmission.

[0066] This invention also proposes a quantum resistance transfer method for a high-precision digital AC bridge, comprising:

[0067] The adjustable signal source is connected in parallel with the first current injection combination network and the second current injection combination network. The adjustable signal source provides current to the standard resistor and the resistor under test through the first current injection combination network and the second current injection combination network, respectively, so as to achieve no current in the high potential branch and the low potential branch. At the same time, the adjustable signal source is connected in parallel with the Wagner balance branch to realize the power supply balance of the digital AC bridge, which is used to adjust the leakage current in the balance branch.

[0068] Adjust the number of turns in each stage of the multi-stage inductive voltage divider so that the ratio of the voltage across the standard resistor to the voltage across the resistor under test is 10. -5 Order of magnitude;

[0069] Adjust the first and second voltages injected by the voltage injection signal source into the standard resistor and the resistor under test, so that the first and second voltages are equal;

[0070] The differential current in the balanced branch is measured and incorporated into the quantum resistance transfer as a compensation quantity.

[0071] This invention proposes a high-precision quantum resistance transfer method based on the principle of inductive voltage division, employing a four-terminal pair defined structure. The four-terminal pair defined connection eliminates the influence of cable resistance and contact resistance. Furthermore, various compensation networks and shielding structures can be incorporated into the four-terminal pair structure to ensure that the bridge circuit can achieve high-precision quantum resistance transfer within a high-frequency range.

[0072] An inductive voltage divider is a type of autotransformer, typically composed of a main coil and multiple secondary coils. It achieves high-precision voltage division ratios by dividing the voltage layer by layer through the mutual inductance between the coils. This invention converts the voltage division ratio of two impedances into the turns ratio of the inductive voltage divider using a high-precision voltage division ratio, and then performs value transfer calculations.

[0073] With the rapid development of semiconductor devices, the measurement accuracy and minimum resolution of voltage-current analog-to-digital converter (ADC) chips have reached a considerably high level, possessing advantages such as high sensitivity and high acquisition frequency. Considering the advantages of ADC chips, this invention incorporates them as compensation devices into the comparison branch. The minute difference current measured by the chip is substituted into the final value transfer calculation, thus solving the error caused by the minute difference potential in traditional AC bridge circuits and achieving high-precision value transfer of AC quantized resistance.

[0074] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0075] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0076] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0077] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A high-precision digital AC bridge, characterized in that, include: Adjustable signal source, power inductive voltage divider, Wagner balanced branch, first current injection combined network, second current injection combined network, multi-stage inductive voltage divider, Kelvin balanced branch, standard resistor and measuring resistor; wherein, the Kelvin balanced branch includes voltage injection signal source and digital measurement and acquisition module. An adjustable signal source is connected to the primary side of a power inductive voltage divider. The secondary side of the power inductive voltage divider has four taps: a secondary first tap, a secondary first tap, a secondary second tap, and a secondary last tap. One end of the Wagner balance branch is connected to the secondary first tap of the power inductive voltage divider and the other end of a standard resistor. The other end of the Wagner balance branch is connected to the secondary second tap of the power inductive voltage divider and the other end of the resistor under test. The input of the first current injection combination network is connected in parallel between the secondary first tap and the secondary first tap of the power inductive voltage divider, and the output of the first current injection combination network is connected to the other end of the standard resistor. The input of the second current injection combination network is connected in parallel between the secondary second tap and the secondary last tap of the power inductive voltage divider, and the output of the second current injection combination network is connected to the other end of the resistor under test. The multi-stage inductive voltage divider includes five cascaded windings. The input terminal of the first-stage winding is connected to one end of the Wagner balance branch and the other end of the standard resistor. The output terminal of the first-stage winding is connected to the other end of the Wagner balance branch and the other end of the resistor to be measured. The output terminal of the fifth-stage winding is connected to the input terminal of the digital measurement and acquisition module. A voltage injection signal source injects a first voltage into one end of a standard resistor and a second voltage into one end of the resistor under test. One end of the standard resistor is connected to one end of the resistor under test. A digital measurement and acquisition module acquires the difference between the first voltage and the second voltage. The digital measurement and acquisition module includes: a first single-pole double-throw (SPD) analog switch, a second single-pole double-throw (SPD) analog switch, and a third single-pole double-throw (SPD) analog switch; the common port of the first SPD analog switch is connected to one end of a standard resistor, and its normally closed port is connected to a matching impedance; the normally open port of the first SPD analog switch is connected to the normally closed port of the second SPD analog switch; the common port of the second SPD analog switch is connected to the input terminal of a follower, and the normally open port of the second SPD analog switch is connected to the normally open port of the third SPD analog switch; the common port of the third SPD analog switch is connected to one end of the resistor to be measured, and the normally closed port of the third SPD analog switch is connected to a matching impedance; both the first and third SPD analog switches are normally closed.

2. The high-precision digital AC bridge according to claim 1, characterized in that, It also includes: a power amplifier; an adjustable signal source connected to the primary side of a power inductive voltage divider via the power amplifier.

3. The high-precision digital AC bridge according to claim 1, characterized in that, The input terminal of the first winding of the multi-stage inductive voltage divider is connected to the other end of the standard resistor to form a high-potential branch; the output terminal of the first winding of the multi-stage inductive voltage divider is connected to the other end of the resistor to be measured to form a low-potential branch; the output terminal of the fifth winding of the multi-stage inductive voltage divider is connected to the input terminal of the digital measurement and acquisition module to form a balanced branch.

4. The high-precision digital AC bridge according to claim 3, characterized in that, The adjustable signal source provides current to the standard resistor and the resistor under test through the first current injection combination network and the second current injection combination network, respectively, so that there is no current in the high potential branch and the low potential branch. An adjustable signal source is connected in parallel with the Wagner balance branch to achieve power balance of the digital AC bridge, and the Wagner balance branch regulates the leakage current in the balance branch.

5. The high-precision digital AC bridge according to claim 4, characterized in that, The circuit topologies of the Wagner balanced branch, the first current injection combined network, and the second current injection combined network are the same, all including: an inductively coupled ratio arm and two-terminal impedances.

6. The high-precision digital AC bridge according to claim 4, characterized in that, It also includes: a first null pointer, a second null pointer, and a third null pointer; the first null pointer is connected to the high-potential branch, the second null pointer is connected to the balanced branch, and the third null pointer is connected to the low-potential branch; each null pointer includes an inductive coupling ratio arm; When the null pointer points to zero, it indicates that the current in the corresponding branch is zero, signifying that the Wagner balance branch, the first current injection combination network, and the second current injection combination network have completed the adjustment of the current in the corresponding branch.

7. The high-precision digital AC bridge according to claim 3, characterized in that, The digital measurement and acquisition module includes: a voltage-current analog-to-digital converter chip and a follower; The follower output is connected to the output of the fifth winding of the multi-stage inductive voltage divider through a balanced branch. The voltage-current analog-to-digital converter chip is connected to the balanced branch and is connected between the output of the fifth winding of the multi-stage inductive voltage divider and the follower.

8. The high-precision digital AC bridge according to claim 1, characterized in that, Switch the first single-pole double-throw analog switch to the normally open port, and keep the second single-pole double-throw analog switch in the normally closed state. The voltage-current analog-to-digital converter chip measures the first voltage. Switch the third single-pole double-throw analog switch to the normally open port, and switch the second single-pole double-throw analog switch to the normally open port. Measure the second voltage. When the first voltage and the second voltage are not equal, adjust the voltage and frequency output by the voltage injection signal source until the first voltage and the second voltage are equal.

9. The high-precision digital AC bridge according to claim 3, characterized in that, It also includes: ten sets of chokes; the chokes are connected to each branch of the bridge. Each branch includes: the connection branch between the first current injection combined network and the secondary first tap of the power inductive voltage divider; the connection branch between the second current injection combined network and the secondary last tap of the power inductive voltage divider; the connection branch between the input terminal of the first winding of the multi-stage inductive voltage divider and the first secondary tap of the power inductive voltage divider; the connection branch between the output terminal of the first winding of the multi-stage inductive voltage divider and the second secondary tap of the power inductive voltage divider; a high-potential branch; a low-potential branch; the connection branch between the other end of the standard resistor and the output terminal of the first current injection combined network; the connection branch between the other end of the resistor under test and the output terminal of the first current injection combined network; the connection branch between the first output terminal of the Kelvin balance branch and one end of the standard resistor; and the connection branch between the second output terminal of the Kelvin balance branch and one end of the resistor under test.

10. A quantum resistance transfer method for a high-precision digital AC bridge, implemented using the high-precision digital AC bridge according to any one of claims 1 to 9, characterized in that, include: The adjustable signal source is connected in parallel with the first current injection combination network and the second current injection combination network. The adjustable signal source provides current to the standard resistor and the resistor under test through the first current injection combination network and the second current injection combination network, respectively, so as to achieve no current in the high potential branch and the low potential branch. At the same time, the adjustable signal source is connected in parallel with the Wagner balance branch to realize the power supply balance of the digital AC bridge, which is used to adjust the leakage current in the balance branch. Adjust the number of turns in each stage winding of the multi-stage inductive voltage divider so that the ratio of the voltage across the standard resistor to the voltage across the resistor under test is 1: Order of magnitude; Adjust the first and second voltages injected by the voltage injection signal source into the standard resistor and the resistor under test, so that the first and second voltages are equal; Measure the differential current in a balanced branch; The differential current is used as a compensation quantity and incorporated into the quantum resistance transmission.

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