阅读说明：本技术 一种四端对交流量子电阻传递电桥及方法 (Four-terminal-pair alternating current quantum resistor transfer bridge and method ) 是由 黄晓钉 佟亚珍 蔡建臻 潘攀 孙毅 王书强 王乾娟 李晶晶 侯旭玮 于 2021-08-25 设计创作，主要内容包括：一种四端对交流量子电阻传递电桥及方法,包括供电电源S、开尔文支路A1、瓦格纳支路A0、第一源组合网络A2、第二源组合网络A3、微差补偿网络A4、主比例感应分压器IVD2、第一四端对交流电阻连接点Z1、第二四端对交流电阻连接点Z2、扼流圈H和若干指零仪D,沿主比例感应分压器IVD2的绕组外周面绕制低匝数的隔离感应绕组L0,L0为微差补偿网络A4的一次绕组提供激磁电流,避免A4的一次绕组直接连接供电电源S导致的各平衡指零网络相互影响,实现电桥快速平衡。并通过改变微差补偿网络A4的第二感应分压器T2一次绕组L3与二次绕组L4匝比的方法,仅用一套分压电容即可实现多频点的虚部微差补偿,达到虚部平衡,实现多频点的四端对交流量子电阻传递电桥。(A four-end-pair alternating current quantum resistance transfer bridge and a method thereof comprise a power supply S, a Kelvin branch A1, a Wagner branch A0, a first source combination network A2, a second source combination network A3, a differential compensation network A4, a main proportional inductive voltage divider IVD2, a first four-end-pair alternating current resistance connection point Z1, a second four-end-pair alternating current resistance connection point Z2, a choke coil H and a plurality of nulling instruments D, wherein a low-turn isolation induction winding L0 is wound along the outer peripheral surface of a winding of the main proportional inductive voltage divider IVD2, the L0 provides excitation current for a primary winding of the differential compensation network A4, the mutual influence of balanced nulling networks caused by the fact that the primary winding of the A4 is directly connected with the power supply S is avoided, and the rapid balance of the bridge is realized. By changing the turn ratio of the primary winding L3 and the secondary winding L4 of the second inductive voltage divider T2 of the differential compensation network A4, imaginary part differential compensation of multiple frequency points can be realized by only one set of voltage dividing capacitor, imaginary part balance is achieved, and a four-terminal pair alternating current quantum resistor transfer bridge of the multiple frequency points is realized.)

1. A four-terminal pair alternating current quantum resistance transfer bridge is characterized in that a low-turn isolation induction winding L0 is wound on a winding of a main proportional induction voltage divider IVD2, and the isolation induction winding L0 provides exciting current for a primary winding of a differential compensation network A4, so that mutual influence of branches caused by the fact that the primary winding of the differential compensation network A4 is directly connected with a power supply S is avoided, and rapid bridge balance is achieved.

2. The four-port ac quantum resistance transfer bridge of claim 1 or 2, wherein the outer periphery of the winding of the main proportional inductive voltage divider IVD2 is wound with one turn of the isolated inductive winding L0.

3. The four-port ac quantum resistance transfer bridge of claim 1, comprising a power supply S, a kelvin port a1, a wagner port a0, a first source combining network a2, a second source combining network A3, a differential compensation network a4, a primary proportional inductive divider IVD2, a first four-port ac resistance junction Z1, a second four-port ac resistance junction Z2, a choke H, and a plurality of nulling instruments D; the Kelvin branch A1 eliminates lead errors by proportionally distributing lead resistances between a first four-terminal pair alternating current resistance connection point Z1 and a second four-terminal pair alternating current resistance connection point Z2; the main proportional inductive voltage divider IVD2 and the wagner branch a0 are connected in parallel to the power supply S to eliminate current leakage at the main proportional arm balance point V0, and the differential compensation network a4 provides an excitation current through the isolated inductive winding L0 and compensates the compensation voltage into the bridge.

4. The four-port AC Quantum resistor transfer bridge of any of claims 1 to 3, wherein the differential compensation network A5 includes a first inductive divider T1 and a second inductive divider T2, the secondary winding L2 of the first inductive voltage divider T1 is combined with a set of voltage dividing resistors R to realize the adjustment of the real part balance of the bridge, the secondary winding L4 of the second inductive voltage divider T2 is combined with a set of voltage dividing capacitors C to realize the adjustment of the imaginary part balance of the bridge, the primary winding L3 of the second inductive voltage divider T2 is provided with a plurality of taps from high end to low end with a certain number of turns, by changing the turn ratio of the primary winding L3 and the secondary winding L4 of the second inductive voltage divider T2, the change of the impedance value of the voltage-dividing capacitor caused by the frequency change is counteracted by the change of the inductive ratio of the second inductive voltage divider T2, so that the impedance value of the voltage-dividing capacitor C is not changed along with the frequency change.

5. The four-port AC quantum resistance transfer bridge as claimed in claim 4, wherein when the primary winding L1 of the first inductive voltage divider T1, the secondary winding L2 of the first inductive voltage divider T1 and the secondary winding T4 of the second inductive voltage divider T2 have equal turns and are all 70 turns, the frequency is 1kHz, and the primary winding L3 of the second inductive voltage divider T2 is connected with a tap having 44 turns; at a frequency of 1.592kHz, the primary winding L3 of the second inductive voltage divider T2 is connected to a tap having 70 turns; at a frequency of 2kHz, the primary winding L3 of the second inductive voltage divider T2 is connected to a tap with 88 turns; at a frequency of 3.184kHz, the primary winding L3 of the second inductive voltage divider T2 is connected to a tap having 140 turns; at a frequency of 5kHz, the primary winding L3 of the second inductive voltage divider T2 is connected to a tap with 220 turns to ensure that the impedance value of the voltage dividing capacitor C does not change with the frequency.

6. The four-port AC quantum resistance transfer bridge according to claim 3, wherein the power supply S comprises a signal generator DDF1, a phase-locked amplifier DDF2 and an isolated inductive voltage divider IVD1, a primary winding of the isolated inductive voltage divider IVD1 is connected to the signal generator DDF1 and the phase-locked amplifier DDF2 through a power amplifier, a secondary winding of the isolated inductive voltage divider IVD1 is divided into a first output terminal V11, a second output terminal V12, a third output terminal V13 and a fourth output terminal V14 from a high end to a low end, and the second output terminal V12 and the third output terminal V13 supply power to a bridge main proportional inductive voltage divider IVD2 and a Wagner branch A0; the number of turns of the coil between the first output terminal V11 and the second output terminal V12 is equal to the number of turns of the coil between the third output terminal V13 and the fourth output terminal V14, the first output terminal V11 and the second output terminal V12 provide power for the bridge high voltage proportional branch where the first source combination network a2 is located, the third output terminal V13 and the fourth output terminal V14 provide power for the bridge low voltage proportional branch where the second source combination network a3 is located, and the polarity of the potential provided to the bridge high voltage proportional branch is opposite to the polarity of the potential provided to the bridge low voltage proportional branch.

7. The four-port alternating current quantum resistance transfer bridge according to claim 1, wherein the choke H or the active choke is looped over a lead wire in the measurement line to ensure that the coaxial sheath currents of the non-oriented structure are equal in magnitude and opposite in direction.

8. A method for measuring a four-terminal pair ac resistance, wherein a four-terminal pair ac resistance Rx to be measured is measured using the four-terminal pair ac quantum resistance transfer bridge of any one of claims 1 to 7, comprising the steps of:

step 1, after acquiring a nominal value of an alternating current resistor Rx of a four-terminal pair to be detected, selecting a standard four-terminal pair alternating current resistor Rs according to measurement requirements, and respectively connecting the alternating current resistor Rx of the four-terminal pair to be detected and the standard four-terminal pair alternating current resistor Rs to a first four-terminal pair alternating current resistor connection point Z1 and a second four-terminal pair alternating current resistor connection point Z2; according to the ratio of the nominal value of the alternating current resistor Rx of the four-end pair to be detected to the nominal value of the alternating current resistor Rs of the standard four-end pair, finding a proportional balance point V0 of a secondary winding of the main proportional inductive voltage divider IVD2 according to the corresponding turn ratio of the winding of the main proportional inductive voltage divider IVD 2;

step 2, adjusting the Wagner branch A0 to enable the potential at the proportional balance point V0 of the main proportional inductive voltage divider IVD2 to be the ground potential, namely enabling a fifth nulling instrument D5 connected with the balance point V0 to be null, and solving the problem of current leakage at the proportional balance point V0 of the winding of the bridge main proportional inductive voltage divider IVD 2;

step 3, adjusting the first source combination network A2 to enable a second zero indicator D2 connected between the high end of the main proportional inductive voltage divider IVD2 and the first four-terminal pair AC resistor connecting point Z1 to zero, and solving the problem that the bridge high-voltage proportional branch has current;

step 4, adjusting a second source combination network A3 to enable a third zero indicator D3 connected between the low end of a main proportional inductive voltage divider IVD2 and a second four-terminal pair alternating current resistor connecting point Z2 to zero, and solving the problem that a bridge low-voltage proportional branch has current;

step 5, adjusting the differential compensation network A4 to enable a first nulling instrument D1 connected with the Kelvin branch A1 to be nulling;

step 6, supplying power to the Kelvin branch A1 through an induction voltage supply winding B0, adjusting the Kelvin branch A1 to enable a first zero indicator D1 connected with the Kelvin branch A to indicate zero again, and solving the problem of equal proportion distribution of lead resistances between a first four-terminal pair alternating current resistance connection point Z1 and a second four-terminal pair alternating current resistance connection point Z2;

step 7, the induction voltage supply winding B0 is enabled not to supply power to the Kelvin branch A1 any more, the differential compensation network A4 is adjusted again, the first nulling instrument D1 is enabled to zero again, and the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are verified to be zero; reading the reading values of the real part and the imaginary part of the differential compensation network A4 at the moment, and obtaining the difference between the real part and the imaginary part of the four-end pair alternating current resistor Rx to be detected and the difference between the real part and the imaginary part of the standard four-end pair alternating current resistor Rs, thereby deriving the real part value and the imaginary part value of the four-end pair alternating current resistor Rx to be detected.

9. The method for measuring the four-port pair alternating current resistance according to claim 8, wherein when the nominal value of the to-be-measured four-port pair alternating current resistance Rx and the nominal value of the standard four-port pair alternating current resistance Rs are different by at least one order of magnitude, the nominal value is large and is connected to a first four-port pair alternating current resistance connection point Z1, the nominal value is small and is connected to a second four-port pair alternating current resistance connection point Z2, and the differential compensation network a4 supplies excitation current through the isolation induction winding L0 and compensates compensation voltage to a bridge arm where the second four-port pair alternating current resistance connection point Z2 is located; or when the difference between the nominal value of the four-terminal pair alternating current resistor Rx to be detected and the nominal value of the standard four-terminal pair alternating current resistor Rs is less than an order of magnitude, the standard four-terminal pair alternating current resistor Rs or the four-terminal pair alternating current resistor Rx to be detected are connected to a first four-terminal pair alternating current resistor connecting point Z1 optionally.

10. The method of claim 8, wherein in step 7, the differential compensation network a4 is adjusted again, after the first nulling instrument D1 is zeroed again, the method checks whether the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are zeroed, and if any of the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are not zeroed, the method repeats steps S2-S7 for 1-2 times, so that the first nulling instrument D1, the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are zeroed.

Technical Field

The invention relates to the technical field of alternating current resistor transmission, in particular to a four-terminal pair alternating current quantum resistor transmission bridge and a method.

Background

The resistance has frequency characteristics, and the tracing of the alternating current resistance is an international difficult problem. Based on the alternating current quantization Hall effect, the impedance unit quantity value is defined by adopting the basic physical constant, the method has the characteristic of not changing along with the change of time and space, the unity of the unit definitions of the alternating current resistance, the capacitance, the inductance and the direct current resistance can be realized, the problem of tracing the source of the current alternating current resistance can be solved, and the method is an international frontier metering technology. The key technical link is that the AC resistance value reproduced by the AC quantization Hall effect is transferred to a real object AC standard resistor with extremely small uncertainty, so that 10 needs to be developed^-8High accuracy impedance bridge of order of magnitude and realize the transfer of the non-directional impedance.

Because the four-terminal pair definition of the alternating-current impedance is the most perfect form, the alternating-current quantized Hall resistance sample is of a four-terminal pair structure, 10^-8The magnitude alternating current resistance also adopts a four-port structure. The technical index of the AC quantization Hall resistance reference is 10^-8The magnitude reproduces the magnitude of the AC impedance, so that the transfer uncertainty of the high-accuracy AC impedance bridge serving as a magnitude transfer bridge should also reach 10^-8Of the order of 10, more widely used than today^-4The magnitude of the impedance bridge or the RLC measuring instrument is higher than 4 to 5 magnitude of magnitude, and the development difficulty is very high. For research, quantum impedance standard based on alternating current quantization Hall effect is establishedAnd four-end-to-end alternating current impedance bridge is adopted to realize tracing from the alternating current resistor to the alternating current quantization Hall resistor standard. The four-terminal pair alternating-current impedance bridge conforms to the definition of alternating-current impedance, various interferences can be eliminated by adopting various technical means, and 10 can be realized^-8Transfer of magnitude of omnidirectional impedance. But the structure is very complicated, needs many times of balance, has the problem of mutual influence between a plurality of balances, makes the balanced convergence very slow, and measurement efficiency is lower, has the single problem of frequency point simultaneously.

Specifically, the four-terminal pair alternating current impedance bridge belongs to a transformer bridge with an extremely accurate proportional value, and the basic principle is to measure alternating current impedance according to the definition of four-terminal pair impedance, namely to ensure that no current flows through a voltage loop and the core-sheath current of a current loop meets the equal large reversal. The schematic diagram is shown in fig. 1. In order to eliminate lead errors, an error potential compensation method is adopted to connect a null indicator at a potential lead, an adjustable compensation power supply is connected at a current lead, such as the cooperation of three pairs of null indicators D1-S1, D2-S2 and D3-S3 in the figure 1 and the adjustable compensation power supply, when the adjustable compensation power supplies S1, S2 and S3 are adjusted to the null indicator at the potential line, the lead errors are compensated, and the current leakage problem can be avoided. The bridge is balanced to be basically completed only when the zero pointing instrument of the three groups of balanced zero pointing networks of S1-D1, S2-D2 and S3-D3 also points to zero by adjusting S4 to point to D4. Because at least 4 pairs of nulling instruments and adjustable compensation power supplies exist, the balance is specifically adjusted, when the differential compensation network A4 is adjusted to achieve the differential balance, the load of a bridge power supply is changed, further the auxiliary balance of the Wagner branch A0 which has achieved the balance is broken, the fifth nulling instrument D5 connected with the proportional balance point V0 of the winding of the main proportional inductive voltage divider IVD2 does not null any more, each zero-balancing network is broken, after further readjustment is needed to enable the third nulling instrument D3, the second nulling instrument D2 and the fifth nulling instrument D5 to null again, the differential compensation network A4 is adjusted again to achieve the differential balance, and after the adjustment of one period is completed, the balance of the Wagner branch is broken again. The greater the magnitude of the change in power supply load caused by adjusting the differential compensation network a4, the more times zero pointing needs to be adjusted cyclically and the less easily this bridge balance can be achieved. That is, each time an adjustable current source is adjusted to cause the nulling instrument of the balanced nulling network to null, the other three groups of balanced nulling networks are affected, and the cyclic adjustment needs to be repeatedly performed for many times, and in the adjusting process, each group of balanced nulling networks cannot be converged simultaneously, so that the adjustment is very laborious.

When the four-terminal pair alternating-current impedance bridge is specifically implemented, one circuit structure is very complex as shown in fig. 2, and the circuit structure comprises a power supply S, a Kelvin branch A1, a Wagner branch A0, a first source combination network A2, a second source combination network A3, a differential compensation network A4, a main proportional inductive voltage divider IVD2, a first four-terminal pair alternating-current resistor connecting point Z1, a second four-terminal pair alternating-current resistor connecting point Z2, a choke coil H and a plurality of zero-pointing instruments D.

The Kelvin branch A1 is connected to a connecting lead between the Z1 and the Z2 in a Kelvin connection mode, the sensing voltage supply winding B0 is connected with a signal generator DDF1 to supply power to the Kelvin branch A1, power can also be supplied to the Kelvin branch A1 in a mode of adding a signal source additionally, a first adjustable current source S1 is formed, and a fourth zero indicator D1, connected with the Kelvin branch A1, of the S1 forms a first balanced zero indicator network S1-D1 to eliminate lead errors of the lead between the Z1 and the Z2.

The signal generator DDF1 and the lock-in amplifier DDF2 are connected to an isolated inductive divider IVD forming the power supply S of the bridge, supplying the whole bridge. The phase locked amplifier DDF2 also acts as a nulling device D in the bridge. The secondary winding of the isolated inductive voltage divider IVD1 is sequentially divided into a first output end V11, a second output end V12, a third output end V13 and a fourth output end V14 from a high end (an upper end in fig. 2) to a low end (a lower end in fig. 2), and the second output end V12 and the third output end V13 provide power for the bridge main proportional inductive voltage divider IVD2 and the wagner branch a 0. The input end of the first source combination network A1 is connected with a first output end V11 and a second output end V12 to form a second adjustable current source S2, the end pair on the same side of a first four-terminal pair alternating current resistor connecting point Z1 is respectively connected with the output end of the first source combination network A1 and the high end of the IVD2, and a second zero-indicating induction winding B2 for inducing the lead current between the first four-terminal pair alternating current resistor connecting point Z1 and the high end of the main proportional induction voltage divider IVD2 is connected with a zero indicator D to form a second balanced zero-indicating network S2-D2 (namely a bridge high-voltage proportional branch). The input end of the second source combination network A2 is connected with the third induction output end and the fourth induction output end to form a third adjustable current source S3, the end pair on the other side of the second four-end pair alternating current resistor connection point Z2 is respectively connected with the output end of the second source combination network A2 and the low end of the IVD2, and a third zero-pointing induction winding B3 for sensing lead current between the low ends of the Z2 and the IVD2 is connected with a zero-pointing instrument D to form a third balanced zero-pointing network S3-D3 (namely a bridge low-voltage proportion branch). S is supplied to the first source combining network a2 at the same voltage and opposite potential to the second source combining network A3. The compensation voltage of the output of the differential compensation network a4 is compensated onto the lead between the low ends of Z2 and IVD 2. In the whole bridge circuit, the voltage ratio of the bridge arm where the Z1 is located to the bridge arm where the Z2 is located is equal to the resistance ratio, so that when the bridge circuit is balanced, the resistance value of the first four-terminal pair of alternating current resistors connected to the Z1 is equal to the resistance value of the second four-terminal pair of alternating current resistors connected to the Z2 plus the resistance value corresponding to the compensation voltage output to the bridge circuit by the differential compensation network A4.

In the bridge circuit, in order to realize a four-terminal pair impedance bridge 10^-8Magnitude transfer, shielding protection is achieved by using a Wagner branch A0, current leakage of a proportional balance point V0 of a main proportional arm of a main proportional inductive voltage divider IVD2 is eliminated, and final balance of a four-terminal-to-alternating-current resistance transfer bridge is achieved by using a differential compensation network A4. At present, a differential compensation network a4 of a four-terminal pair alternating current impedance bridge is directly powered by a bridge power supply S and is connected in parallel with a tegner branch a0, when differential adjustment is performed, the previously balanced supplementary balance of the tegner branch is broken due to the change of load, and after the differential adjustment is performed, the supplementary balance of the tegner branch is adjusted to seriously affect the differential balance, that is, the mutual influence between the supplementary balance of the tegner and the differential balance is particularly prominent, so that the convergence process of the bridge balance is slower.

In addition, balancing of the four-terminal pair ac resistance transfer bridge requires both real and imaginary part balancing. The imaginary part compensation voltage is usually obtained by dividing voltage of a group of voltage dividing capacitors and output resistors, and when the frequency changes, the impedance value 1/j ω c generated by the capacitors changes, so that multiple groups of voltage dividing capacitors are needed to realize multiple frequency points, and the structure and the switching of the four-terminal pair alternating current impedance bridge are very complex and are not easy to realize.

Disclosure of Invention

The invention provides a four-end-to-AC quantum resistance transfer bridge and a method, wherein an isolation induction winding for providing exciting current for a primary winding of a differential compensation network is wound on a winding of a main proportional induction voltage divider, the number of turns of the coil of the isolation induction winding is less, and the isolation induction winding can be set to be only one turn, so that the mutual influence of all balance null networks caused by the direct connection of the primary winding of the differential compensation network with a power supply is avoided, and the 10 th implementation mode is realized^-8On the basis of magnitude high-accuracy four-terminal alternating current resistance transmission, mutual interference between auxiliary balanced Wagner branches and a differential compensation network is greatly reduced, and bridge balance is rapidly converged.

The technical scheme of the invention is as follows:

a low-turn isolation induction winding L0 is wound on a winding of a main proportional induction voltage divider IVD2, and the isolation induction winding L0 provides exciting current for a primary winding of a differential compensation network A5, so that the mutual influence of branches caused by the fact that the primary winding of the differential compensation network A5 is directly connected with a power supply S is avoided, and the rapid balance of the bridge is realized.

Preferably, the outer peripheral surface of the winding of the main proportional induction voltage divider IVD2 is wound with one turn of the isolated induction winding L0.

Preferably, the four-terminal-pair alternating-current quantum resistance transfer bridge comprises a power supply S, a Kelvin branch A1, a Wagner branch A0, a first source combination network A2, a second source combination network A3, a differential compensation network A4, a main proportional inductive voltage divider IVD2, a first four-terminal-pair alternating-current resistance connection point Z1, a second four-terminal-pair alternating-current resistance connection point Z2, a choke coil H and a plurality of nulling instruments D; the Kelvin branch A1 eliminates lead errors by proportionally distributing lead resistances between a first four-terminal pair alternating current resistance connection point Z1 and a second four-terminal pair alternating current resistance connection point Z2; the main proportional inductive voltage divider IVD2 and the wagner branch a0 are connected in parallel to the power supply S to eliminate current leakage at the main proportional arm balance point V0, and the differential compensation network a4 provides an excitation current through the isolated inductive winding L0 and compensates the compensation voltage into the bridge.

Preferably, the differential compensation network a5 includes a first inductive voltage divider T1 and a second inductive voltage divider T2, the secondary winding L2 of the first inductive voltage divider T1 is combined with a set of voltage dividing resistors R to achieve adjustment of the real part balance of the bridge, the secondary winding L4 of the second inductive voltage divider T2 is combined with a set of voltage dividing capacitors C to achieve adjustment of the imaginary part balance of the bridge, the primary winding L3 of the second inductive voltage divider T2 is provided with a plurality of taps from the high end to the low end according to a certain number of turns, and by changing the turn ratio of the primary winding L3 and the secondary winding L4 of the second inductive voltage divider T2, the change of the impedance value of the voltage dividing capacitors due to the frequency change is cancelled by the change of the inductive ratio of the second inductive voltage divider T2, so that the impedance value of the voltage dividing capacitors C does not change with the frequency change.

Preferably, when the primary winding L1 of the first inductive voltage divider T1, the secondary winding L2 of the first inductive voltage divider T1 and the secondary winding T4 of the second inductive voltage divider T2 have equal turns and all have 70 turns, the frequency is 1kHz, and the primary winding L3 of the second inductive voltage divider T2 is connected with a tap having 44 turns; at a frequency of 1.592kHz, the primary winding L3 of the second inductive voltage divider T2 is connected to a tap having 70 turns; at a frequency of 2kHz, the primary winding L3 of the second inductive voltage divider T2 is connected to a tap with 88 turns; at a frequency of 3.184kHz, the primary winding L3 of the second inductive voltage divider T2 is connected to a tap having 140 turns; at a frequency of 5kHz, the primary winding L3 of the second inductive voltage divider T2 is connected to a tap with 220 turns to ensure that the impedance value of the voltage dividing capacitor C does not change with the frequency.

Preferably, the power supply S comprises a signal generator DDF1, a phase-locked amplifier DDF2, and an isolated inductive voltage divider IVD1, a primary winding of the isolated inductive voltage divider IVD1 is connected to the signal generator DDF1 and the phase-locked amplifier DDF2 through a power amplifier (not shown), a secondary winding of the isolated inductive voltage divider IVD1 is sequentially divided into a first output terminal V11, a second output terminal V12, a third output terminal V13, and a fourth output terminal V14 from a high end to a low end, and the second output terminal V12 and the third output terminal V13 provide power for a bridge main proportional inductive voltage divider IVD2 and a wigner branch a 0; the number of turns of the coil between the first output terminal V11 and the second output terminal V12 is equal to the number of turns of the coil between the third output terminal V13 and the fourth output terminal V14, the first output terminal V11 and the second output terminal V12 provide power for the bridge high voltage proportional branch where the first source combination network a2 is located, the third output terminal V13 and the fourth output terminal V14 provide power for the bridge low voltage proportional branch where the second source combination network a3 is located, and the polarity of the potential provided to the bridge high voltage proportional branch is opposite to the polarity of the potential provided to the bridge low voltage proportional branch.

Preferably, the choke coil H or the active choke coil is sleeved on a lead in the measuring circuit, so that the coaxial core sheath currents of the non-directional structure of the coaxial core sheath are equal in magnitude and opposite in direction.

A transfer method for measuring four-end pair alternating current resistance uses the four-end pair alternating current quantum resistance transfer bridge to measure the four-end pair alternating current resistance Rx to be measured, which comprises the following steps:

step 1, after acquiring a nominal value of an alternating current resistor Rx of a four-terminal pair to be detected, selecting a standard four-terminal pair alternating current resistor Rs according to measurement requirements, and respectively connecting the alternating current resistor Rx of the four-terminal pair to be detected and the standard four-terminal pair alternating current resistor Rs to a first four-terminal pair alternating current resistor connection point Z1 and a second four-terminal pair alternating current resistor connection point Z2; finding a proportional balance point V0 of the IVD2 according to the corresponding turn ratio of the winding of the main proportional inductive voltage divider IVD2 according to the ratio of the nominal value of the to-be-detected four-end pair alternating current resistor Rx to the nominal value of the standard four-end pair alternating current resistor Rs;

step 2, adjusting the Vagner branch A0 to enable the potential at the proportional balance point V0 of the main proportional inductive voltage divider IVD2 to be the ground potential, namely enabling a fifth nulling instrument D5 connected with the balance point V0 to be null, and solving the problem of current leakage of the main proportional arm of the bridge;

step 3, adjusting the first source combination network A2 to enable a second zero indicator D2 connected between the high end of the main proportional inductive voltage divider IVD2 and the first four-terminal pair AC resistor connecting point Z1 to zero, and solving the problem that the bridge high-voltage proportional branch has current;

step 4, adjusting a second source combination network A3 to enable a third zero indicator D3 connected between the low end of a main proportional inductive voltage divider IVD2 and a second four-terminal pair alternating current resistor connecting point Z2 to zero, and solving the problem that a bridge low-voltage proportional branch has current;

step 5, adjusting the differential compensation network A4 to enable a first nulling instrument D1 connected with the Kelvin branch A1 to be nulling;

step 6, supplying power to the Kelvin branch A1 through an induction voltage supply winding B0, adjusting the Kelvin branch A1 to enable a first zero indicator D1 connected with the Kelvin branch A to indicate zero again, and solving the problem of equal proportion distribution of lead resistances between a first four-terminal pair alternating current resistance connection point Z1 and a second four-terminal pair alternating current resistance connection point Z2;

step 7, the induction voltage supply winding B0 is enabled not to supply power to the Kelvin branch A1 any more, the differential compensation network A4 is adjusted again, the first nulling instrument D1 is enabled to zero again, and the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are verified to be zero; reading the reading values of the real part and the imaginary part of the differential compensation network A4 at the moment, and obtaining the difference between the real part and the imaginary part of the four-end pair alternating current resistor Rx to be detected and the difference between the real part and the imaginary part of the standard four-end pair alternating current resistor Rs, thereby deriving the real part value and the imaginary part value of the four-end pair alternating current resistor Rx to be detected.

Preferably, when the nominal value or the estimated value of the ac resistance Rx of the four-terminal pair to be measured is 10 times or more of that of the ac resistance Rs of the standard four-terminal pair, the ac resistance Rx of the four-terminal pair to be measured is connected to the first ac resistance connection point Z1 of the four-terminal pair, the ac resistance Rs of the standard four-terminal pair is connected to the second ac resistance connection point Z2 of the four-terminal pair, and the differential compensation network a4 provides an excitation current through the isolation induction winding L0 and compensates a compensation voltage to a bridge arm where the ac resistance Rs of the standard four-terminal pair is located.

Preferably, when the nominal value or the estimated value of the standard four-terminal pair alternating current resistor Rs is 10 times or more of the nominal value of the to-be-detected four-terminal pair alternating current resistor Rx, the to-be-detected four-terminal pair alternating current resistor Rx is connected to a second four-terminal pair alternating current resistor connection point Z2, the standard four-terminal pair alternating current resistor Rs is connected to a first four-terminal pair alternating current resistor connection point Z1, and the differential compensation network a4 provides an excitation current through the isolation induction winding L0 and compensates a compensation voltage to a bridge arm where the to-be-detected four-terminal pair alternating current resistor Rx is located.

Preferably, when the difference between the nominal value or the estimated value of the alternating current resistor Rx of the four-terminal pair to be measured and the standard alternating current resistor Rs is less than 10 times, the standard alternating current resistor Rs or the four-terminal pair to be measured is optionally connected to the first four-terminal pair alternating current resistor connection point Z1.

Preferably, in step 7, the infinitesimal compensation network a4 is adjusted again, after the first nulling instrument D1 is nulling again, whether or not the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are all null-pointing may be selected to be verified, and if any one of the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 is not null-pointing, the steps S2-S7 are repeated 1-2 times, so that the first nulling instrument D1, the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are all null-pointing.

Compared with the prior art, the invention has the advantages that:

1. the four-terminal pair alternating current quantum resistance transfer bridge and the method thereof of the invention are characterized in that a low-turn isolated induction winding L0 is separately wound on the winding of the main proportional induction voltage divider IVD2 to supply power to the differential compensation network, because the isolated induction winding L0 induces voltage from the winding of the main proportional induction voltage divider IVD2 in an induction mode, and the number of turns of the coil of the isolated induction winding L0 is very small, most preferably one turn, the load added by the differential compensation network A4 to the bridge power supply S is almost negligible, namely when the differential compensation network A4 is adjusted to participate in a set of voltage dividing resistance R and a set of voltage dividing capacitance C which are measured, the load is equivalent to a constant load, and the auxiliary balance null network of the Wagner branch cannot be greatly influenced or even cannot be influenced, thereby reducing the mutual interference of the differential adjusting network A4 and other auxiliary balance zero-pointing networks, and enabling the balance of the bridge to converge faster.

2. According to the four-terminal-pair alternating current quantum resistance transfer bridge and the method, the method of changing the turn ratio of the primary winding L3 and the secondary winding L4 of the second inductive voltage divider T2 is changed, the phase shift of multi-frequency points can be realized by only using one set of imaginary part differential compensation capacitor bank, the imaginary part differential adjustment is realized, the imaginary part balance is achieved, and then a set of voltage dividing capacitor C is obtained, so that the four-terminal-pair alternating current quantum resistance transfer bridge of the multi-frequency points can be obtained.

Drawings

FIG. 1 is a schematic diagram of a four terminal pair AC impedance transfer bridge;

FIG. 2 is a circuit diagram of a four-terminal pair AC resistance transfer bridge that is not easily balanced;

FIG. 3 is a circuit diagram of a four-port AC quantum resistance transfer bridge according to the present invention;

FIG. 4 is a schematic diagram of a main proportional voltage divider of the four-port AC quantum resistance transfer bridge according to the present invention;

fig. 5 is an internal circuit diagram of a differential injection network in the four-port ac quantum resistance transfer bridge according to the present invention.

The reference numbers in the figures are:

s1-first adjustable current source, S2-second adjustable current source, S3-second adjustable current source, D1-first nulling instrument, D2-second nulling instrument, D3-third nulling instrument, D4-fourth nulling instrument, D5-fifth nulling instrument, S1-D1-first balanced nulling network, S1-D1-second balanced nulling network, S1-D1-third balanced nulling network, IVD 1-isolated inductive divider, V1-first output, V1-second output, V1-third output, V1-fourth output, IVD 1-main proportional inductive divider, V1-proportional balance point, L1-isolated inductive winding, a 1-open circuit branch, a 1-first source combining network, a 1-second source combining network, a 1-B inductive divider, first 1-first inductive voltage-supply voltage-compensating network, B1-B inductive voltage-compensating network, b3-third nulling sense winding, B4-compensation winding, Z1-first four-terminal pair ac resistor connection point, Z2-second four-terminal pair ac resistor connection point, DDF 1-signal generator, DDF 2-power amplifier, R-voltage dividing resistor, R1-first voltage dividing resistor, R2-second voltage dividing resistor, R3-third voltage dividing resistor, R4-fourth voltage dividing resistor, R5-fifth voltage dividing resistor, R6-resistor, C-voltage dividing capacitor, C1-first voltage dividing capacitor, C2-second voltage dividing capacitor, C3-third voltage dividing capacitor, C4-fourth voltage dividing capacitor, C5-fifth voltage dividing capacitor, T1-first sense voltage divider, T2-second sense voltage divider, T3-differential injection winding, L1-first sense voltage divider primary winding, L2-first sense voltage divider, L3-second sense voltage divider, L4-second sense voltage divider, h-choke, Rx-four-end AC resistance to be measured, Rs-standard four-end AC resistance.

Detailed Description

In order to facilitate an understanding of the invention, the invention is described in more detail below with reference to specific examples.

Example 1

As shown in fig. 3, a circuit diagram of a four-terminal-to-ac quantum-resistor transfer bridge includes an isolated inductive voltage divider IVD1, a differential compensation network a4, a ratio inductive voltage divider IVD2, a wigner branch a5, a first four-terminal-to-ac-resistor connection point Z1, a second four-terminal-to-ac-resistor connection point Z2, a choke H, and a nulling device D. The first four-terminal pair alternating current resistor connecting point Z1 is connected with a standard four-terminal pair alternating current resistor Rs, the standard four-terminal pair alternating current resistor Rs is preferably a four-terminal pair Hall quantum resistor, and the standard four-terminal pair alternating current resistor Rs can also be calibrated to reach 10^-8Or other higher uncertainty level of standard resistance. And the second four-terminal pair alternating current resistor connecting point Z2 is connected with a four-terminal pair alternating current resistor Rx to be detected.

The nominal resistance value ratio of the standard four-terminal pair alternating current resistor Rs to the four-terminal pair alternating current resistor Rx to be measured is 10:1, and the winding coil turns of the IVD2 are 110 turns.

The number of turns of the coil between the first output terminal V11 and the second output terminal V12 of the IVD1 is equal to the number of turns of the coil between the third output terminal V13 and the fourth output terminal V14, both of which are 10 turns, the number of turns of the coil between the second output terminal V12 and the third output terminal V13 is 100 turns, after the signal generator DDF1 and the lock-in amplifier DDF2 inject the IVD1, the potential of the first output terminal V11 is 11V, the potential of the second output terminal V12 is 10V, the potential of the third output terminal V13 is-1V, and the potential of the fourth output terminal V14 is-2V.

The main proportional inductive voltage divider IVD2 is an auto-coupled inductive voltage divider with a high side potential equal to the potential of the second output terminal V12 at 10V and a low side potential equal to the potential of the third output terminal V13 at-1V. In order to balance the main proportional arm of the bridge initially, the turn ratio on the IVD2 winding should be 10:1 due to the power load of the winding being squared with the number of turns in the main proportional arm, i.e., the proportional balance point V0 of IVD2 should be at the tap 100 turns from its high end. The proportional balance point V0 is connected to the fifth nulling instrument D5 through the first nulling sensing winding B1, but because the main proportional arm has leakage, the fifth nulling instrument D5 connected to the proportional balance point V0 does not null before measurement and balance adjustment, and here, the fifth nulling instrument D5 is null by adjusting the tegner branch a0 connected in parallel to the IVD2, that is, the potential of the proportional balance point V0 is the ground potential, so as to achieve supplementary balance of the tegner branch, and ensure that no leakage current flows through the main proportional arm, that is, to eliminate the influence of leakage. Wherein, the fifth nulling instrument D5 may preferably be connected (e.g., switched) to the nulling instruments D of fig. 2 and 3, respectively, when the first nulling instrument D1, the second nulling instrument D2, and the third nulling instrument D3 are balanced by the bridge; alternatively, when the bridge is balanced, the fifth nulling instrument D5 may be connected to a single nulling instrument, and the remaining first nulling instrument D1, second nulling instrument D2, and third nulling instrument D3 may share the nulling instruments D in fig. 2 and 3 by switching. In the present embodiment, the first nulling device D1 is equivalent to D1 and D4 in fig. 1.

In the four-terminal pair bridge, a non-directional structure needs to ensure that the core current of each coaxial line is equal in magnitude and opposite in direction, and the current adopted solution is to sleeve a choke coil H or an active choke coil H to ensure the non-directional structure of a measuring line. As shown in fig. 4, 1 turn of the isolated sensing winding L0 is wound around the winding of the main proportional sensing voltage divider IVD2, the voltage that the 1 turn of the isolated sensing winding L0 can sense is 0.1V, that is, the exciting current of the primary winding of the differential compensation network a4 is obtained from the isolated sensing winding L0, since the voltage is sensed by the isolated winding and the influence on the IVD2 itself is very small, the voltage is reflected to the wagner branch a0 and the power supply S, since the load of the power supply and the number of turns are in a square relationship, that is, the load of the differential compensation sensing voltage supply winding B4 in the main proportional arm of the bridge is one percent, the load of the differential compensation network a4 to the power supply of the bridge is also one percent of the original load. Can ignore basically, can not cause the balanced change of the branch road of Wagner even, even can cause the balanced and balanced mutual interference of the poor balance of Wagner branch road, also can be very fast through several times of adjustment, reach the bridge balance for the bridge is balanced can fast convergence, reduces the accent balanced time and the work load of bridge by a wide margin.

If shown in fig. 2, the high and low voltage terminals of the IVD2, the wagner branch a1, and the differential compensation network a4 are connected in parallel between the second output terminal V12 and the third output terminal V13. The supply voltage of the differential compensation network a4 is 10V, and the overall power type load thereof will directly affect the tegaser a0, and the effect on the tegaser a0 balance is at least 100 times that of the present invention, and for each balance nulling network whose convergence performance is different, the effect is reflected in the time length for adjusting the bridge balance, the scheme shown in fig. 2 needs at least 1-2 days, even a week, but the scheme shown in the present application needs only a few minutes. The working strength of measuring personnel is greatly reduced, and the long and withered property of the measuring process is relieved.

Example 2

A method for measuring four-terminal pair alternating current resistance, using the four-terminal pair alternating current quantum resistance transfer bridge to measure the four-terminal pair alternating current resistance Rx to be measured, includes the following steps:

step 1, estimating or acquiring a nominal value of an alternating current resistor Rx of the four-terminal pair to be measured to be 100 omega, selecting a standard alternating current resistor Rs of the four-terminal pair to be measured to be a Hall quantum resistor according to measurement requirements, preferably 1K omega, and setting the uncertainty level to be 10^-8Omega. Connecting a second four-terminal pair alternating current resistor Rx of the four-terminal pair to be tested to an alternating current resistor connecting point Z2, and connecting a standard four-terminal pair alternating current resistor Rs to a first four-terminal pair alternating current resistor connecting point Z1; according to the ratio of the nominal value of the four-end-to-alternating current resistor Rx to be measured to the nominal value of the standard four-end-to-alternating current resistor Rs, finding out a proportional balance point V0 of the IVD2 at a tap position 100 turns away from the high end of the winding according to the corresponding turn ratio of 10:1 of the winding of the main proportional induction voltage divider IVD2；

Step 2, adjusting the Vagner branch A0 to enable the potential at the proportional balance point V0 of the main proportional inductive voltage divider IVD2 to be the ground potential, namely enabling a fifth nulling instrument D5 connected with the balance point V0 to be null, and solving the problem of current leakage of the main proportional arm of the bridge;

step 3, adjusting the first source combination network A2 to enable a second zero indicator D2 connected between the high end of the main proportional inductive voltage divider IVD2 and the first four-terminal pair AC resistor connecting point Z1 to zero, and solving the problem that the bridge high-voltage proportional branch has current;

step 4, adjusting a second source combination network A3 to enable a third zero indicator D3 connected between the low end of a main proportional inductive voltage divider IVD2 and a second four-terminal pair alternating current resistor connecting point Z2 to zero, and solving the problem that a bridge low-voltage proportional branch has current;

step 5, adjusting the differential compensation network A4 to make the first nulling instrument D1 (which is equivalent to D4 in FIG. 1) connected to the Kelvin branch A1 null;

step 6, supplying power to the Kelvin branch A1 through an induction voltage supply winding B0, adjusting the Kelvin branch A1 to enable a first zero indicator D1 (which is equivalent to D3 in the picture 1) connected with the Kelvin branch A to indicate zero, enabling lead resistances between the alternating current resistor Rx of the four pairs to be detected and the alternating current resistor Rs of the standard four pairs to be distributed in proportion, further eliminating errors caused by leads connecting the alternating current resistor Rx of the four pairs to be detected and the alternating current resistor Rs of the standard four pairs, and solving the problem of equal proportion distribution of the lead resistances between a connecting point Z1 of the alternating current resistor connected with the first four pairs and a connecting point Z2 of the alternating current resistor connected with the second four pairs; the sensing voltage supply winding B0 is preferably an isolated sensing winding with one or more additional turns on the main proportional sensing voltage divider IVD 2; or supplied in the form of a kelvin leg a1 by adding a signal source to the inductive supply voltage winding B0.

Step 7, the induction voltage supply winding B0 is enabled not to supply power to the Kelvin branch A1 any more, the differential compensation network A4 is adjusted again, and the first zero indicator D1 (which is equivalent to D4 in the figure 1) is enabled to indicate zero again; the standard four-terminal pair AC resistor Rs is an impedance unit value defined by basic physical constants based on AC quantization Hall effect, and the uncertainty of the impedance unit value can reach 10 at present^-8Therefore, it is finally necessary to adjust the differential compensation network a4 so that the first nulling instrument D1 (corresponding to D4 in fig. 1) is nulling again. The real part partial pressure value and the imaginary part partial pressure value of the differential compensation network A4 can be obtained by adjusting the number and the positions of a set of divider resistors and a set of divider capacitors in the differential compensation network A4 which are connected to a bridge circuit, further the real part difference and the imaginary part difference between an alternating current resistor Rx of a four-terminal pair to be detected and an alternating current resistor Rs of a standard four-terminal pair are obtained, and the standard four-terminal pair is used for 10 pairs of the alternating current resistors Rs^-8The uncertainty level of the magnitude is completely transmitted to the four pairs of alternating current resistors Rx to be measured through the electric bridge.

As another embodiment, when the nominal value of the ac resistor Rx of the four-terminal pair to be measured is 1K Ω, and the ac resistor Rs of the standard four-terminal pair is 100 Ω, the ac resistor Rx of the four-terminal pair to be measured is connected to the ac resistor connection point Z1 of the first four-terminal pair, the ac resistor Rs of the standard four-terminal pair is connected to the ac resistor connection point Z2 of the second four-terminal pair, and the differential compensation network a4 provides an excitation current through the isolation induction winding L0 and compensates a compensation voltage to a bridge arm where the ac resistor Rs of the standard four-terminal pair is located. The internal structure of the differential compensation network a4 is shown in fig. 4, and will be described in detail in the following embodiment.

Preferably, in step 7, after the differential compensation network a4 is adjusted again to make the first nulling instrument D1 zero again, it is selected to check whether or not the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 all zero. When the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are not selected to be checked to see whether all are null, the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 are all null by default. When the second zero indicator D2, the third zero indicator D3 and the fifth zero indicator D5 are selected to check whether all indicate zero, if all indicate zero in the second zero indicator D2, the third zero indicator D3 and the fifth zero indicator D5, the difference between the real part and the imaginary part of the alternating current resistor Rx and the standard four-end pair alternating current resistor Rs to be measured can be obtained through zero setting (zero setting for 5 times) in one period, and therefore the real part value and the imaginary part value of the alternating current resistor Rx to be measured are derived. If any of the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 does not null, the steps S2-S7 are repeated 1-2 times, so that the first nulling instrument D1, the second nulling instrument D2, the third nulling instrument D3 and the fifth nulling instrument D5 all null.

Example 3

The internal structure of the differential compensation network a4 is shown in fig. 5, and includes a first inductive voltage divider T1, a second inductive voltage divider T2, a set of voltage dividing resistors R (R1-R5) connected to a secondary winding L2 of the first inductive voltage divider T1, a set of voltage dividing capacitors C (C1-C5) connected to a secondary winding L4 of the second inductive voltage divider T2, a resistor R6, and a compensation winding B4, where the secondary winding L2 of the first inductive voltage divider T1 and the secondary winding L4 of the second inductive voltage divider T2 are respectively provided with 10 taps, and each tap is provided with 5 connection points for respectively connecting the corresponding voltage dividing resistor R (R1-R5) or the voltage dividing capacitor C (C1-C5). The voltage-dividing resistor R (R1-R5) and the voltage-dividing capacitor C (C1-C5) are respectively connected or not connected with corresponding taps, the current value on the resistor R6 can be changed, the differential injection voltage injected into a lead between the lower end of the IVD2 and the AC resistor connecting point Z2 through the compensation winding B4 is changed, the first zero-pointing balance network D1 is enabled to point zero, and the differential adjustment function is achieved.

The primary winding L3 of the second inductive voltage divider T2 is an adjustable winding, the primary winding L3 of the second inductive voltage divider T2 is provided with a plurality of taps according to a certain turn ratio, preferably, 6 taps are provided in fig. 5, and the 1 st tap, the 2 nd tap, the 3 rd tap, the 4 th tap, the 5 th tap and the 6 th tap are respectively from a high end to a low end, the 6 th tap is directly connected to a low-voltage end of the isolation inductive winding L0, and the high-voltage end of the isolation inductive winding L0 is selectively connected to the 1 st tap, the 2 nd tap, the 3 rd tap, the 4 th tap or the 5 th tap according to the magnitude of frequency. And then, the four-end-pair alternating current quantum resistance transfer bridge with multiple frequency points can be obtained by not changing each capacitor of the voltage division capacitor C. Namely, a set of voltage-dividing capacitor C is adopted, so that the four-end-to-alternating current quantum resistor transfer bridge with multiple frequency points can be realized.

First induction voltage divider primary winding L1, first induction voltage divider secondary winding L2 and second induction voltage divider secondary winding L4 turn number equal is 70 circles, first induction voltage divider secondary winding L2 and second induction voltage divider secondary winding L4 all are equipped with 10 taps, and the coil turn number between per two adjacent taps is 7 circles, each divider resistance one end in R1-R5 all with resistance R6 series connection, the other end can select the connection respectively any tap of first induction voltage divider secondary winding L2, each divider capacitance one end in the divider capacitance C1-C5 all with resistance R6 series connection, the other end can select any tap of connecting L4 respectively. The current value of the resistor R6 is changed by connecting different taps, and the differential voltage injected into a lead between the low-voltage end of the main proportional inductive voltage divider IVD2 and the Z2 by the L0 is further changed, so that the function of differential adjustment is realized.

A first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5 in R1-R5, wherein the resistances of R1, R2, R3, R4 and R5 are 1K omega, 10K omega, 100K omega, 10K omega, 1M omega and 10M omega respectively; and the capacitances of the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4 and the fifth capacitor C5 in the C1-C5 are respectively 10pF, 100pF, 1nF, 10nF and 100nF, and the capacitances of the C1, the C2, the C3, the C4 and the C5 are respectively 10pF, 100pF, 1nF, 10nF and 100 nF.

Preferably, the number of turns n1 of the first excitation winding L1, the number of turns n2 of the real part differential sensing winding L2 and the number of turns n8 of the imaginary part differential sensing winding L4 are all 70 turns, and the number of turns n7 of the coil between the 5 th tap and the 6 th tap is 44 turns when the frequency is 1 kHz; when the frequency is 1.592kHz, the number of coil turns n6 between the 4 th tap and the 6 th tap is 70 turns; when the frequency is 2kHz, the number of turns n5 of the coil between the 3 rd tap and the 6 th tap is 88 turns; when the frequency is 3.184kHz, the number of coil turns n4 between the 2 nd tap and the 6 th tap is 140 turns; when the frequency is 5kHz, the number of turns n3 of the coil between the 1 st tap and the 6 th tap is 220 turns so as to ensure that the impedance of the imaginary part differential compensation capacitor bank is unchanged. Namely, the four-terminal pair alternating current quantum resistance transfer bridge of the multi-frequency point is obtained by not changing each capacitor of the imaginary part differential compensation capacitor bank.

It should be noted that the above-described embodiments may enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail with reference to the drawings and examples, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.