Self-calibrating high-accuracy resistance ratio reference arm

Abstract

This invention relates to a self-calibrating, high-accuracy resistance ratio reference arm, comprising an adjusting arm, a fixed arm, a first reversing switch, a second reversing switch, and a null indicator. The adjusting arm and the fixed arm each include several pairs of paired first and second main resistance pairs. An adjustable resistor and a first adjusting resistor are connected in series and in parallel with the first main resistance pair at the beginning of the adjusting arm. A second adjusting resistor is connected in parallel with the second main resistance pair at the end of the fixed arm. The adjusting arm and the fixed arm are connected in series, and the positive and negative terminals of the first and second reversing switches are connected to the beginning of the adjusting arm and the end of the fixed arm, respectively. This invention employs a high-precision resistor pairing combination and incorporates a low-weight adjustment structure, reducing the overall bridge arm resistance temperature coefficient, minimizing the impact of ambient temperature on the ratio arm resistance, and ensuring the accuracy and stability of the reference ratio arm resistance value. It features high reliability, high stability, high accuracy, and self-calibration capability.

Description

Technical Field

[0001] This invention relates to the field of electronic technology, and in particular to a self-calibrating, high-accuracy resistance ratio reference arm. Background Technology

[0002] The bridge method is a commonly used method for measuring resistance, such as... Figure 1 As shown, taking the Wheatstone bridge as an example, it consists of four resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R1, R1, R1, R2, R1, R1, R2, R3, R1, R1, R1, R2 ... N The four arms of a bridge are connected in a quadrilateral. A galvanometer is connected to one diagonal of the quadrilateral, forming the "bridge". When the potentials between the two endpoints of the bridge are equal, the current in the bridge circuit is zero, and the galvanometer pointer points to zero. At this point, the bridge is said to be in equilibrium. Based on the equilibrium condition of the bridge, if the resistances of three arms are known, the resistance R can be calculated using the formula for measuring resistance using a bridge. N The resistance of the other bridge arm can be calculated by multiplying R2 by R3 and then by R1. This is the principle behind measuring resistance using a single-arm bridge. Here, we call R2 the reference resistor, and the bridge arm composed of R3 and R1 is called the reference arm. Therefore, the accuracy of the known reference resistor R2 and the accuracy of the ratio of the reference arm R3 / R1 directly affect the measurement accuracy of the resistor being measured. Furthermore, in some high-accuracy resistor ratio voltage dividers, the resistors in the voltage divider section often need to be calibrated, which also requires the use of a high-accuracy reference ratio arm for adjustment and calibration.

[0003] Currently, common resistance ratio arm solutions have the following drawbacks:

[0004] (1) At present, the accuracy of non-digital single-arm resistance measurement is generally 0.1 to 0.05, which is low. At the same time, since it directly uses fixed resistor components to build the circuit, it cannot self-calibrate the ratio accuracy of the ratio arm. Inaccurate ratio arm resistance will bring a certain error to the final ratio.

[0005] (2) Currently, the resistance ratio arm solution has high requirements for the ambient temperature and is greatly affected by ambient temperature fluctuations. Summary of the Invention

[0006] To address the technical problems existing in the prior art, the present invention aims to provide a self-calibrating high-accuracy resistance ratio reference arm, which features high reliability, high stability, high accuracy, and self-calibration capability.

[0007] To achieve the above-mentioned objectives, the present invention provides a self-calibrating, high-accuracy resistance ratio reference arm, comprising:

[0008] The adjusting arm includes several sets of first main resistor pairs, an adjustable resistor, and a first regulating resistor. Each set of first main resistor pairs includes two first main resistors connected in parallel. The two first main resistors connected in parallel have opposite temperature drift directions and opposite aging deviation directions. Several sets of first main resistor pairs are connected in series, and the absolute values ​​of the temperature drift coefficients of several sets of first main resistor pairs are the same. The adjustable resistor and the first regulating resistor are connected in series and in parallel with the first main resistor pair at the beginning of the adjusting arm.

[0009] The fixed arm includes several sets of second main resistor pairs and second adjusting resistors. Each set of second main resistor pairs includes two second main resistors connected in parallel. The two second main resistors connected in parallel have opposite temperature drift directions and opposite aging deviation directions. Several sets of second main resistor pairs are connected in series in sequence. The absolute values ​​of the temperature drift coefficients of several sets of second main resistor pairs are the same. The second adjusting resistor is connected in parallel with the second main resistor pair at the tail end of the fixed arm.

[0010] The adjusting arm and the fixed arm are connected in series end to end;

[0011] The reversing switch includes a first reversing switch and a second reversing switch that are linked together. Each reversing switch includes a terminal, a positive terminal, a negative terminal, and a switching switch. The switching switch is connected to either the positive terminal or the negative terminal, so that the terminal is connected to different circuits. The positive terminal of the first reversing switch is connected to the head end of the adjusting arm, and the negative terminal of the first reversing switch is connected to the tail end of the fixed arm. The positive terminal of the second reversing switch is connected to the tail end of the fixed arm, and the negative terminal of the second reversing switch is connected to the head end of the adjusting arm.

[0012] The zero-point indicator has one end connected in series between the adjusting arm and the fixed arm, and the other end connected to a terminal block.

[0013] According to one technical solution of the present invention, the adjustable resistor and the first regulating resistor are configured such that 50% of the nominal value of the adjustable resistor is connected in series with the first regulating resistor to balance the resistance deviation between the regulating arm and the fixed arm.

[0014] According to one technical solution of the present invention, the first main resistor and the second main resistor are fixed on the PCB board by flip-chip bonding, the end faces of the resistor leads on the first main resistor and the second main resistor are facing away from the surface of the PCB board, and the back faces of the first main resistor and the second main resistor are fixed to the surface of the PCB board by a high-resistance adhesive.

[0015] According to one technical solution of the present invention, the resistor leads are connected through a Hammon junction structure.

[0016] According to one technical solution of the present invention, each group of the first main resistor pair and each group of the second main resistor pair are provided with an equipotential shielding loop, the equipotential shielding loop comprising:

[0017] A perimeter shielding ring is set on the PCB board to form a shielding space, and the two resistors of each resistor pair are set inside the shielding space.

[0018] A connecting wire and an equipotential resistor are disposed between two adjacent wall shielding rings, and the equipotential resistor is connected to the two adjacent wall shielding rings through the connecting wire.

[0019] According to one technical solution of the present invention, the temperature drift coefficient of the adjustable resistor, the first regulating resistor and the second regulating resistor is not greater than 100ppm / ℃.

[0020] According to one technical solution of the present invention, the resistance value of the second regulating resistor is not less than 1000 times the resistance value of the single first main resistor or the second main resistor.

[0021] According to one technical solution of the present invention, the terminal is a 99.99% high-purity oxygen-free copper terminal, and its surface is treated with anti-oxidation using a rotating self-friction structure process. The terminal is provided with a high-insulation polytetrafluoroethylene insulation component.

[0022] According to one technical solution of the present invention, the connection circuit between the first main resistor, the second main resistor, the adjustable resistor, the first regulating resistor, the second regulating resistor, the first reversing switch, the second reversing switch, the null indicator, and the connection circuit between the connecting line and the equipotential resistor are connected by direct soldering of the device pins, and the solder used in the connection circuit is a special low thermoelectric potential solder.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention proposes a self-calibrating, high-accuracy resistance ratio reference arm. An adjusting resistor is connected in parallel with at least one set of first resistors, so that the adjusting resistor is added to the ratio arm in a low-weight adjustment structure, which ensures the accuracy and stability of the resistance value of the reference ratio arm. At the same time, through a reversing switch, the accuracy of the resistance ratio arm can be self-calibrated, thereby further improving the accuracy of the reference ratio arm.

[0025] In this invention, the main resistors that make up the adjusting arm and the fixed arm are first paired and connected in parallel according to the temperature drift aging deviation requirements. The matched main resistor pairs are then connected in series in sequence. By adopting a temperature coefficient matching method, the temperature coefficient of the entire bridge arm resistor is reduced, the influence of ambient temperature on the ratio arm resistor is reduced, and the stability of the reference arm ratio is improved. By adopting a series and parallel connection of multiple sets of resistors, the rated power of the bridge arm resistor is increased and the voltage coefficient is reduced.

[0026] This invention addresses the problem of leakage current in the PCB board by using a flip-chip soldering method to mount the resistor on the PCB board. The resistor leads do not make any contact with the PCB board, thereby effectively avoiding leakage current caused by the PCB board and preventing the series and parallel differences caused by leakage current from affecting the measurement results of resistance measurement using the reference arm.

[0027] This invention employs an equipotential shielding design, setting up an independent equipotential shielding loop for each resistor pair and extending the connecting wires overhead, so that all resistors are surrounded by the same potential. This completely avoids electric field leakage current between resistor pairs and adjacent resistor pairs, and between resistor pairs and the casing. By setting up the shielding circuit, the leakage current and voltage coefficient are prevented from affecting the bridge arm ratio, thereby further improving the accuracy of the reference ratio arm.

[0028] This invention employs various measures to reduce contact thermoelectric potential, and improves the design from aspects such as terminal structure, connection method, and contact materials to comprehensively reduce the influence of thermoelectric potential in the circuit, thereby avoiding the adverse effects of thermoelectric potential on the stability and accuracy of high-precision resistors, and thus affecting the accuracy of high-precision resistor measurement results. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0030] Figure 1 A schematic representation of the Wheatstone bridge circuit diagram;

[0031] Figure 2 This schematic diagram illustrates the structure of a self-calibrating, high-accuracy resistivity ratio reference arm provided in one embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram illustrating a matched main resistor pair according to one embodiment of the present invention;

[0033] Figure 4 This schematic diagram illustrates the structure of a resistor on a PCB board according to an embodiment of the present invention.

[0034] Figure 5 This schematic diagram illustrates the connection of resistor leads according to one embodiment of the present invention.

[0035] Figure 6 The schematic diagram illustrates the structure of an equipotential shielding loop according to one embodiment of the present invention.

[0036] The correspondence between the reference numerals and the components is as follows:

[0037] 1. Adjusting arm; 2. Fixed arm; 3. First reversing switch; 4. Second reversing switch; 5. Null indicator; 6. PCB board; 7. Resistor lead; 8. High-resistance adhesive; 9. Harmon joint; 10. Fence shielding ring; 11. Equipotential resistor; R5. Adjustable resistor; R6. First adjusting resistor; R7. Second adjusting resistor. Detailed Implementation

[0038] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0039] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0040] like Figure 2 As shown, a self-calibrating high-accuracy resistance ratio reference arm of the present invention includes an adjusting arm 1, a fixed arm 2, a first reversing switch 3, a second reversing switch 4, and a null indicator 5.

[0041] The regulating arm 1 includes several sets of first main resistor pairs, an adjustable resistor R5, and a first regulating resistor R6. Taking an regulating arm 1 with N sets of first main resistor pairs as an example, the first main resistors R101, R102, ..., R10N, R201, R202, ..., R20N that make up the regulating arm 1 are matched with each other to form a first main resistor pair. The two first resistors forming a first main resistor pair are connected in parallel, and the temperature drift directions and aging deviation directions of the two parallel first main resistors are opposite. The N sets of first main resistor pairs are connected in series, and the absolute values ​​of the temperature drift coefficients of the several sets of first main resistor pairs are the same.

[0042] The adjustable resistor R5 and the first adjusting resistor R6 are connected in series and then connected in parallel with the first main resistor at the beginning of the adjusting arm 1. The resistance ratio of the reference arm can be adjusted by adjusting the adjustable resistor R5 or setting the value of the first adjusting resistor R6.

[0043] The fixed arm 2 includes several sets of second main resistor pairs and second adjusting resistors R7. Taking the adjusting arm 1, which includes N sets of second main resistor pairs, as an example, the second main resistors R301, R302, ..., R30N, R401, R402, ..., R40N that make up the adjusting arm 1 are matched to form second main resistor pairs, such as R301 and R401, R302 and R402, ..., R30N and R40N. The two second resistors forming a second main resistor pair are connected in parallel, and the temperature drift directions and aging deviation directions of the two parallel second main resistors are opposite. The N sets of second main resistor pairs are connected in series sequentially, and the absolute values ​​of the temperature drift coefficients of the several sets of second main resistor pairs are the same. The second adjusting resistor R7 is connected in parallel with the second main resistor pair at the tail end of the fixed arm 2.

[0044] The adjusting arm 1 and the fixed arm 2 are connected in series, that is, the first main resistor pair consisting of the first main resistor R10N and the first main resistor R20N is connected in series with the second main resistor pair consisting of the second main resistor R30N and the second main resistor R40N.

[0045] In one embodiment of the present invention, the adjustable resistor R5 and the first adjusting resistor R6 are configured such that 50% of the nominal value of the adjustable resistor R5 is connected in series with the adjusting resistor to balance the resistance deviation between the adjusting arm 1 and the fixed arm 2. The temperature drift coefficient of the adjustable resistor R5, the first adjusting resistor R6, and the second adjusting resistor R7 is not greater than 100ppm / ℃.

[0046] The reversing switch is a double-pole double-throw switch, comprising a first reversing switch 3 and a second reversing switch 4 that are linked together. The first and second reversing switches 3 and 4 are coaxially connected to achieve synchronous switching. The first and second reversing switches 3 and 4 are used to switch the direction in which the adjusting arm 1 and the fixed arm 2 are connected to the circuit to achieve self-calibration of the resistance ratio reference arm. Each reversing switch includes a terminal, a positive terminal, a negative terminal, and a switching switch. The switching switch is connected to either the positive or negative terminal, allowing the second terminal to be connected to different circuits. The positive terminal of the first reversing switch 3 is connected to the beginning of the adjusting arm 1, and the negative terminal is connected to the end of the fixed arm 2. The first reversing switch 3 has a terminal A. The positive terminal of the second reversing switch 4 is connected to the end of the fixed arm 2, and the negative terminal is connected to the beginning of the adjusting arm 1. The second reversing switch 4 has a terminal C.

[0047] One end of the zero indicator 5 is connected in series between the adjusting arm 1 and the fixed arm 2, and the other end of the zero indicator 5 is connected to a terminal B.

[0048] In one embodiment of the present invention, such as Figure 4 As shown, the first main resistor and the second main resistor are soldered onto the PCB board 6 by flip-chip bonding. The end faces of the resistor leads 7 on the first and second main resistors are facing away from the surface of the PCB board 6. The back faces of the first and second main resistors are fixed to the surface of the PCB board 6 by high-resistance adhesive 8.

[0049] Resistive devices are generally placed on circuit boards. When the power is applied, there is a potential difference between the pins of the resistor. Therefore, leakage current will be generated between the resistor pins within the circuit board area. If the resistivity of the circuit board material itself is not high, a conductor of leakage current may be formed on the surface of the circuit board, resulting in a large series-parallel difference in the measurement results.

[0050] To effectively reduce the leakage current caused by soldering resistors on the PCB, the resistors on the bridge arms are assembled using an "inverted" lap soldering process. The resistor leads 7 do not make any contact with the PCB board 6. The PCB board 6 only serves as a support, thereby effectively avoiding the leakage current caused by the PCB board 6 and thus effectively improving the bridge arm ratio.

[0051] In one embodiment of the present invention, such as Figure 5 As shown, resistor lead 7 is connected via a Hammon joint 9 structure, which minimizes the influence of resistor lead 7.

[0052] In one embodiment of the present invention, such as Figure 6As shown, the first and second main resistor pairs are provided with equipotential shielding loops. The equipotential shielding loops include a perimeter shielding ring 10, connecting wires, and equipotential resistors 11. The perimeter shielding rings 10 are mounted on the PCB board 6, forming a shielding space on the PCB board. The two resistors of each resistor pair are placed within the shielding space. The connecting wires and equipotential resistors 11 are positioned between two adjacent perimeter shielding rings 10, and the equipotential resistors 11 are connected to the two adjacent perimeter shielding rings 10 via connecting wires.

[0053] By using overhead lead-out connecting wires, all resistors are surrounded by the same potential, completely avoiding electric field leakage current between resistor pairs and adjacent resistor pairs, and between the resistors and the casing. This is also an important measure to ensure the proportions of the bridge arms.

[0054] In one embodiment of the present invention, terminals A, B, and C are all 99.99% high-purity oxygen-free copper terminals, and their surfaces are treated with an anti-oxidation process using a rotating self-friction structure. Terminals A, B, and C are provided with high-insulation polytetrafluoroethylene insulating components to improve the insulation performance between the terminals and the reference arm housing. The connection circuit between the first main resistor, the second main resistor, the adjustable resistor R5, the first adjusting resistor R6, the second adjusting resistor R7, the reversing switch, the null indicator 5, and the connection circuit between the connecting line and the equipotential resistor 11 are connected by direct soldering of the device pins. The solder used in the connection circuit is a special low thermal potential solder. Preferably, the special low thermal potential solder is CdSnPb special low thermal potential solder to reduce the low thermal potential caused by soldering.

[0055] The method of using this invention is as follows:

[0056] First, based on the actual input voltage and impedance requirements, select appropriate main resistor components with suitable resistance values ​​and power ratings. Ideally, choose main resistors with the same resistance value to reduce the difficulty and workload of subsequent pairing. All selected main resistor components undergo screening and testing, and are paired according to temperature drift and aging deviation requirements, then connected in parallel. The N pairs of paired main resistors are then connected in series sequentially, and divided into two main groups according to temperature drift and aging deviation requirements: adjusting arm 1 and fixed arm 2. For example... Figure 3 As shown, the temperature drift aging deviation requirements are: the temperature drift directions of the two paired main resistors R are opposite and the aging deviation values ​​are opposite; the absolute values ​​of the N pairs of main resistors that form the adjusting arm 1 or the fixed arm 2 after temperature drift matching are consistent.

[0057] Based on the actual resistance values ​​of the N pairs of main resistors on adjusting arm 1 and the N pairs of main resistors on fixed arm 2, estimate the resistance values ​​of adjusting resistors R6 and R7 respectively. To ensure adjustment accuracy, the resistance values ​​of adjusting resistors R6 and R7 are generally not less than 1000 times that of a single main resistor. Connect adjusting resistors R6 and R7 in parallel to the first main resistor pair at the beginning of adjusting arm 1 and the second main resistor pair at the end of fixed arm 2, respectively.

[0058] An adjustable resistor R5 is connected in series with the adjusting resistor R6 on the adjusting arm 1 to achieve precise adjustment. The selection principle for the adjustable resistor R5 is: 50% of the nominal value of the adjustable resistor R5 connected in series with the adjusting resistor R6 can balance the resistance deviation between the adjusting arm 1 and the fixed arm 2.

[0059] Since the temperature drift coefficients of adjustable resistors R5, R6, and R7 are no greater than 100ppm / ℃, the overall resistance accuracy of the bridge arm can be guaranteed to be within the 1E-8 level.

[0060] After the resistance matching is completed, the switching terminals of the reversing switch are connected to the main resistors of the adjusting arm 1 and the fixed arm 2 to form a self-calibrating, high-accuracy resistance ratio reference arm. A standard resistor or the resistor to be measured can be connected between terminals A and B, and between terminals B and C, forming a single-arm bridge for testing the resistance ratio or resistance value.

[0061] By using a double-pole double-throw reversing switch, the first reversing switch 3 and the second reversing switch 4 are switched synchronously, realizing the forward and reverse reversing of the circuit. With the help of a null indicator and an external voltage auxiliary circuit, the bridge arm can be self-calibrated.

[0062] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0063] Finally, it should be noted that the above description represents a preferred embodiment of the present invention. It should be pointed out that although preferred embodiments have been described, those skilled in the art, once they understand the basic inventive concept of the present invention, can make various improvements and modifications without departing from the principles described herein. These improvements and modifications should also be considered within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

Claims

1. A self-calibrating, high-accuracy resistance ratio reference arm, characterized in that, include: The adjusting arm (1) includes several sets of first main resistor pairs, an adjustable resistor (R5), and a first regulating resistor (R6). Each set of first main resistor pairs includes two first main resistors connected in parallel. The two first main resistors connected in parallel have opposite temperature drift directions and opposite aging deviation directions. Several sets of first main resistor pairs are connected in series in sequence, and the absolute values ​​of the temperature drift coefficients of several sets of first main resistor pairs are the same. The adjustable resistor (R5) and the first regulating resistor (R6) are connected in series in sequence and in parallel with the first main resistor pair at the head end of the adjusting arm (1). The fixed arm (2) includes several sets of second main resistor pairs and second regulating resistors (R7). Each set of second main resistor pairs includes two second main resistors connected in parallel. The two second main resistors connected in parallel have opposite temperature drift directions and opposite aging deviation directions. Several sets of second main resistor pairs are connected in series in sequence. The absolute values ​​of the temperature drift coefficients of several sets of second main resistor pairs are the same. The second regulating resistor (R7) is connected in parallel with the second main resistor pair at the tail end of the fixed arm (2). The adjusting arm (1) and the fixed arm (2) are connected in series end to end; The reversing switch includes a first reversing switch (3) and a second reversing switch (4) that are linked together. Each reversing switch includes a terminal, a positive terminal, a negative terminal, and a switching switch. The switching switch is connected to the positive terminal or the negative terminal, so that the terminal is connected to different circuits. The positive terminal of the first reversing switch (3) is connected to the head end of the adjusting arm (1), and the negative terminal of the first reversing switch (3) is connected to the tail end of the fixed arm (2). The positive terminal of the second reversing switch (4) is connected to the tail end of the fixed arm (2), and the negative terminal of the second reversing switch (4) is connected to the head end of the adjusting arm (1). The zero-pointing instrument (5) has one end connected in series between the adjusting arm (1) and the fixed arm (2), and the other end connected to a terminal block.

2. The self-calibrating high-accuracy resistance ratio reference arm according to claim 1, characterized in that, The adjustable resistor (R5) and the first regulating resistor (R6) are configured such that 50% of the nominal value of the adjustable resistor (R5) is connected in series with the first regulating resistor (R6) to balance the resistance deviation between the regulating arm (1) and the fixed arm (2).

3. The self-calibrating high-accuracy resistance ratio reference arm according to claim 1, characterized in that, The first main resistor and the second main resistor are fixed on the PCB board (6) by flip-chip bonding. The end face of the resistor lead (7) on the first main resistor and the second main resistor is set away from the surface of the PCB board (6). The back face of the first main resistor and the second main resistor is fixed to the surface of the PCB board (6) by high-resistance adhesive (8).

4. The self-calibrating high-accuracy resistance ratio reference arm according to claim 3, characterized in that, The resistor lead (7) is connected via a Hammon joint (9) structure.

5. The self-calibrating high-accuracy resistance ratio reference arm according to claim 1, characterized in that, Each group of first main resistor pairs and each group of second main resistor pairs are provided with an equipotential shielding loop, the equipotential shielding loop comprising: A wall shielding ring (10) is set on the PCB board (6) to form a shielding space, and the two resistors of each resistor pair are set in the shielding space; A connecting line and an equipotential resistor (11) are provided between two adjacent wall shielding rings (10), and the equipotential resistor (11) is connected to the two adjacent wall shielding rings (10) through the connecting line.

6. The self-calibrating high-accuracy resistance ratio reference arm according to claim 1, characterized in that, The temperature drift coefficient of the adjustable resistor (R5), the first regulating resistor (R6), and the second regulating resistor (R7) is no greater than 100ppm / ℃.

7. The self-calibrating high-accuracy resistance ratio reference arm according to claim 1, characterized in that, The resistance of the second regulating resistor (R7) is not less than 1000 times the resistance of the first main resistor or the second main resistor alone.

8. The self-calibrating high-accuracy resistance ratio reference arm according to claim 1, characterized in that, The terminal is made of 99.99% high-purity oxygen-free copper, and its surface is treated with anti-oxidation using a rotating self-friction structure process. The terminal is equipped with a high-insulation polytetrafluoroethylene insulation component.

9. The self-calibrating high-accuracy resistance ratio reference arm according to claim 5, characterized in that, The connection circuit between the first main resistor, the second main resistor, the adjustable resistor (R5), the first regulating resistor (R6), the second regulating resistor (R7), the first reversing switch (3), the second reversing switch (4), the null indicator (5), and the connection circuit between the connecting line and the equipotential resistor (11) are connected by direct soldering of the device pins, and the solder used in the connection circuit is a special low thermoelectric potential solder.

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