Impedance measurement device and method based on weak current measurement

Abstract

The application discloses a kind of impedance measurement device and method based on weak current measurement, impedance measurement device based on weak current measurement includes automatic balance bridge, current measurement module and voltage measurement module;Voltage measurement module is used to measure the voltage signal of the impedance to be measured and range resistance module;Current measurement module includes measurement input cable, current amplification unit and potential synchronous unit;Measurement input cable includes coaxially arranged outer shield layer, inner shield layer and center signal line;Outer shield layer is grounded;Center signal line is used to detect the unbalanced current between the impedance to be measured and range resistance module, and input current amplification unit;Potential synchronous unit includes shield layer driving structure and compensation structure;Shield layer driving structure is used to output driving signal to drive the potential synchronization of inner shield layer and center signal line;Compensation structure compensates the phase and amplitude of driving signal, solves the problem that traditional automatic balance bridge weak signal is difficult to extract, transmission is easy to lose.

Description

Technical Field

[0001] This application relates to the field of impedance measurement technology, and in particular to an impedance measurement device and method based on weak current measurement. Background Technology

[0002] In the field of modern science and technology and engineering applications, impedance measurement technology is widely used in scenarios such as electronic component characteristic analysis and material electrical property characterization, and improving measurement accuracy has always been one of the core requirements of this field.

[0003] In practical impedance measurement scenarios, the automatic balancing bridge method has become a commonly used technical solution for measuring the impedance under test due to its mature principle and simple structure. However, the impedance-related electrical signal output by the automatic balancing bridge often has significant weakness characteristics: on the one hand, the signal amplitude is extremely low, often a very weak current signal in the fA range; on the other hand, such weak signals are easily submerged by complex noises such as environmental electromagnetic interference and circuit parasitic noise, making it extremely difficult to extract the useful signal. At the same time, during long-distance signal transmission and subsequent processing, not only is it easy to introduce additional noise interference, but the distributed capacitance and parasitic inductance of the transmission link may also cause signal phase and amplitude shifts and amplitude attenuation.

[0004] Existing conventional signal amplification and detection methods are insufficient to effectively amplify weak signals while achieving accurate noise suppression and signal fidelity. They often suffer from problems such as insufficient noise suppression capability, severe signal distortion, and poor range adaptability. Ultimately, the accuracy and stability of impedance measurement cannot meet the application requirements of high-precision scenarios, thus limiting the further promotion and application of the automatic balancing bridge method in the field of high-precision impedance measurement. Summary of the Invention

[0005] To address the existing technical problems, this invention provides an impedance measurement device and method based on weak current measurement. It uses a three-coaxial cable to collect the unbalanced weak current from an automatic balancing bridge, and amplifies the signal using a current amplification unit. Simultaneously, a potential synchronization unit ensures that the inner shielding layer and the center signal line are at the same potential, canceling transmission interference. After the bridge is balanced, the voltage signals of the impedance under test and the range resistance module are measured synchronously, ultimately achieving impedance calculation. This solves the problems of difficult extraction and easily distorted transmission of weak signals from traditional automatic balancing bridges.

[0006] In a first aspect, embodiments of this application provide an impedance measurement device based on weak current measurement, including an automatic balancing bridge, a current measurement module, and a voltage measurement module;

[0007] The automatic balancing bridge includes a first excitation source, a second excitation source, a range resistor module, and a balance adjustment module; the voltage measurement module is used to measure the voltage signal of the impedance to be measured and the range resistor module.

[0008] The current measurement module includes a measurement input cable, a current amplification unit, and a potential synchronization unit; the measurement input cable includes a coaxial outer shielding layer, an inner shielding layer, and a center signal line; the outer shielding layer is grounded; the center signal line is used to detect the unbalanced current between the impedance under test and the range resistance module, and inputs it to the current amplification unit;

[0009] The potential synchronization unit includes a shielding layer driving structure and a compensation structure. The first input terminal of the shielding layer driving structure is connected to the input terminal of the current amplification unit, and the output terminal is connected to the inner shielding layer. It is used to output a driving signal to drive the potential synchronization of the inner shielding layer and the center signal line. The compensation structure is connected between the second input terminal and the output terminal of the shielding layer driving structure. It is used to compensate the phase and amplitude of the driving signal based on the length of the measurement input cable.

[0010] In one alternative embodiment, the current amplification unit includes a first amplification structure and a range adjustment structure;

[0011] The first amplification structure includes a first amplification element, the input terminal of which is the input terminal of the current amplification unit, used to convert a weak current signal into a voltage signal;

[0012] The range adjustment structure includes a first switching element and multiple feedback resistors with different resistance values; the first end of the multiple feedback resistors is connected to the input end of the first amplification structure, and the second end is connected to the first end of the first switching element; the second end of the first switching element is connected to the output end of the first amplification structure, and the feedback resistors are switched based on the range control signal.

[0013] In one alternative embodiment, the range adjustment structure further includes multiple capacitors; the multiple capacitors are connected in parallel across the feedback resistor.

[0014] In one alternative embodiment, the current amplification unit further includes a second amplification structure;

[0015] The second amplification structure includes a second switching element, a second amplification element, and a first peripheral resistor structure; the second switching element is used to receive and connect different first peripheral resistor structures to the second amplification element based on the amplification control signal, so that the second amplification element amplifies the signal by different factors.

[0016] In one alternative embodiment, the shielding layer driving structure includes a unity-gain buffer;

[0017] The first input terminal of the unity-gain buffer is connected to the input terminal of the first amplifying element, and the output terminal is connected to the inner shielding layer; the second input terminal of the unity-gain buffer is connected to the first terminal of the compensation structure, and the second terminal of the compensation structure is connected to the output terminal of the unity-gain buffer.

[0018] In one alternative embodiment, the compensation structure includes a compensation resistor, a compensation capacitor, and an adjustable capacitor;

[0019] One end of the compensation resistor is connected to the second input terminal of the unity-gain buffer, and the other end is connected to one end of the compensation capacitor; the other end of the compensation capacitor is connected to the output terminal of the unity-gain buffer; one end of the adjustable capacitor is connected to the connection point of the compensation resistor and the compensation capacitor, and the other end is grounded.

[0020] An adjustable capacitor is used to receive and adjust its own capacitance value based on a compensation adjustment signal to compensate for the phase margin; the compensation adjustment signal is determined based on the length of the measurement input cable.

[0021] In an optional embodiment, the PCB board is further included, and a protective ring is provided on the PCB board. The protective ring is a conductive ring surrounding the high-impedance input node of the current amplification unit. The high-impedance input node includes the input terminal of the first amplification element and the input terminal of the range adjustment structure.

[0022] The protective ring is connected to the output terminal of the shielding layer drive structure and is synchronized with the potential of the inner shielding layer and the center signal line.

[0023] In one alternative embodiment, a cutout area is provided on the PCB board; the cutout area is located between the interface of the measurement input cable and the current measurement module, and is a physical isolation area filled with high insulating material, used to cut off the surface leakage current path between the measurement input cable and other circuit modules.

[0024] In one optional embodiment, the voltage measurement module includes a third switching element and a voltage measurement element;

[0025] The first input terminal of the third switching element is connected between the impedance to be measured and the first excitation source, the second input terminal is connected between the range resistor module and the second excitation source, and the output terminal is connected to the voltage measuring element. It is used to acquire the first voltage signal of the impedance to be measured or the second voltage signal of the range resistor module based on the switching control signal.

[0026] Secondly, embodiments of this application provide an impedance measurement method, based on the impedance measurement device based on weak current measurement described in the first aspect, comprising:

[0027] The reference resistance value of the range resistance module is determined based on the impedance to be measured;

[0028] The unbalanced current between the impedance to be measured and the range resistance module is obtained using the current measurement module.

[0029] The phase and amplitude offset of the unbalanced current are compensated by a compensation structure based on the length of the measurement input cable, and the compensated unbalanced current is determined as the unbalanced current.

[0030] If the unbalanced current is not zero, a balance adjustment signal is generated by the balance adjustment module based on the unbalanced current, and the second excitation source is adjusted based on the balance adjustment signal to obtain the adjusted unbalanced current; or; if the unbalanced current is zero, the first voltage signal across the impedance to be measured and the second voltage signal of the range resistor module are obtained.

[0031] The impedance value of the impedance to be measured is determined based on the first voltage signal, the second voltage signal, and the reference resistance value.

[0032] Thirdly, embodiments of this application provide an impedance measurement apparatus, the apparatus comprising:

[0033] The first determining module is used to determine the reference resistance value of the range resistance module based on the impedance to be measured.

[0034] The current measurement module is used to obtain the unbalanced current between the impedance to be measured and the range resistance module.

[0035] The compensation module is used to compensate for the phase and amplitude offset of the unbalanced current based on the length of the measurement input cable using the compensation structure, and to determine the compensated unbalanced current as the unbalanced current.

[0036] The voltage measurement module is used to generate a balance adjustment signal based on the unbalanced current using the balance adjustment module if the unbalanced current is not zero, and adjust the second excitation source based on the balance adjustment signal to obtain the adjusted unbalanced current; or, if the unbalanced current is zero, obtain the first voltage signal across the impedance to be measured and the second voltage signal of the range resistor module.

[0037] The second determining module is used to determine the impedance value of the impedance to be measured based on the first voltage signal, the second voltage signal, and the reference resistance value.

[0038] Fourthly, embodiments of this application provide an electronic device, which includes a processor and a memory. The memory stores at least one instruction, at least one program, code set, or instruction set. The processor loads and executes the at least one instruction, at least one program, code set, or instruction set to implement the impedance measurement method of the first aspect.

[0039] Fifthly, embodiments of this application provide a computer-readable storage medium storing at least one instruction or at least one program, wherein the at least one instruction or at least one program is loaded and executed by a processor to implement the impedance measurement method of the first aspect.

[0040] Sixthly, embodiments of this application provide a computer program product or computer program including computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions, causing the computer device to perform the impedance measurement method of the first aspect.

[0041] The impedance measurement device and method based on weak current measurement provided in this application have the following technical effects:

[0042] The impedance measurement device based on weak current measurement includes an automatic balancing bridge, a current measurement module, and a voltage measurement module. The automatic balancing bridge includes a first excitation source, a second excitation source, the impedance to be measured, a range resistance module, and a balance adjustment module. The voltage measurement module is used to measure the voltage signals of the impedance to be measured and the range resistance module. The current measurement module includes a measurement input cable, a current amplification unit, and a potential synchronization unit. The measurement input cable includes a coaxially arranged outer shielding layer, an inner shielding layer, and a center signal line. The outer shielding layer is grounded. The center signal line is used to detect the unbalanced current between the impedance to be measured and the range resistance module and input it to the current amplification unit. The potential synchronization unit includes a shielding layer driving structure and a compensation structure. The first input terminal of the shielding layer driving structure is connected to the input terminal of the current amplification unit, and the output terminal is connected to the inner shielding layer, used to output a driving signal to drive the potential synchronization of the inner shielding layer and the center signal line. The compensation structure is connected between the second input terminal and the output terminal of the shielding layer driving structure, used to compensate for the phase and amplitude of the driving signal based on the length of the measurement input cable. In this application, the unbalanced weak current of the automatic balancing bridge is collected by using a three-coaxial cable, and the signal is amplified by the current amplification unit. At the same time, the potential synchronization unit makes the inner shielding layer and the center signal line at the same potential to cancel transmission interference. After the bridge is balanced, the voltage signals of the impedance to be measured and the range resistance module are measured synchronously to finally realize the impedance calculation. This solves the problems of weak signal extraction and transmission distortion in traditional automatic balancing bridges. Attached Figure Description

[0043] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of an impedance measurement device based on weak current measurement provided in an embodiment of this application;

[0045] Figure 2This is a schematic diagram of an automatic balancing bridge provided in an embodiment of this application. Figure 1 ;

[0046] Figure 3 This is a schematic diagram of a current measurement module provided in an embodiment of this application;

[0047] Figure 4 This is a schematic diagram of a first current amplification unit provided in an embodiment of this application;

[0048] Figure 5 This is a circuit diagram of a first current amplification unit provided in an embodiment of this application;

[0049] Figure 6 This is a schematic diagram illustrating the effect of a first enlarged structure provided in an embodiment of this application;

[0050] Figure 7 This is a circuit diagram of a current amplification unit provided in an embodiment of this application;

[0051] Figure 8 This is a schematic diagram illustrating the effect of a second enlarged structure provided in an embodiment of this application. Figure 1 ;

[0052] Figure 9 This is a schematic diagram illustrating the effect of a second enlarged structure provided in an embodiment of this application. Figure 2 ;

[0053] Figure 10 This is a schematic diagram of a shielding layer driving structure provided in an embodiment of this application;

[0054] Figure 11 This is a circuit diagram of a shielding layer driving structure provided in an embodiment of this application;

[0055] Figure 12 This is a schematic diagram of a PCB protection ring layout provided in an embodiment of this application;

[0056] Figure 13 This is a bandwidth comparison curve between a conventional solution and the solution of this application, provided in an embodiment of this application;

[0057] Figure 14 This is a comparison chart of leakage current tests under different cable lengths provided in an embodiment of this application;

[0058] Figure 15 This is a flowchart illustrating an impedance measurement method provided in an embodiment of this application. Figure 1 ;

[0059] Figure 16 This is a flowchart illustrating an impedance measurement method provided in an embodiment of this application. Figure 2 ;

[0060] Figure 17 This is a schematic diagram of the structure of an impedance measurement device provided in an embodiment of this application;

[0061] Figure 18 This is a hardware structure block diagram of a server for an impedance measurement method provided in an embodiment of this application. Detailed Implementation

[0062] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0063] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0064] Please see Figure 1 , Figure 1 This is a schematic diagram of an impedance measurement device based on weak current measurement provided in an embodiment of this application, including an automatic balancing bridge 1, a current measurement module 2, and a voltage measurement module 3.

[0065] In this embodiment, the automatic balancing bridge 1 includes a first excitation source 11, a second excitation source 12, a range resistor module 14, and a balance adjustment module 15, forming an automatic balancing bridge for measuring the impedance to be measured 13.

[0066] The first excitation source 11 is used to provide an excitation source signal for the impedance to be measured 13, the second excitation source 12 is used to provide an excitation source signal for the range resistor module 14, and the balance adjustment module 15 is used to adjust the second excitation source 12 based on the unbalanced current between the impedance to be measured 13 and the range resistor module 14 so that the automatic balancing bridge 1 can achieve balance.

[0067] Figure 2 This is a schematic diagram of an automatic balancing bridge provided in an embodiment of this application. Figure 1The core principle of the automatic balancing bridge for impedance measurement is the equivalent matching of the electrical parameters of the impedance to be measured 13 and the range resistor module 14 with known parameters in the bridge's balanced state. The first excitation source 11 and the second excitation source 12 provide stable excitation signals, such as sinusoidal signals, which act on the branch of the impedance to be measured 13 and the branch of the range resistor module 14, respectively, forming the two core branches of the bridge. Since the parameters of the impedance to be measured 13 are unknown, the impedances of the two branches are initially mismatched, resulting in an unbalanced current.

[0068] The balance adjustment module 15 captures this unbalanced current and generates an adjustment signal through vector modulation or other means. It adjusts the second excitation source 12 and then adjusts the equivalent parameters of the range resistor module 14 in reverse until the unbalanced current of the automatic balancing bridge approaches zero. At this time, the bridge reaches a balanced state.

[0069] Since the resistance value of the range resistor module 14 is known, the specific value of the impedance to be measured 13 can be deduced by reading the parameters of the range resistor module 14 in the balanced state, thus realizing impedance measurement.

[0070] In one alternative embodiment, the range resistor module 14 includes multiple reference resistors with different resistance values ​​and multiple range switches. The resistance values ​​of the reference resistors may be 10Ω, 100Ω, 1kΩ, 10kΩ, etc.

[0071] Each reference resistor is connected in series with the range switch, and multiple sets of series-connected reference resistors are connected in parallel with the range switch. Multiple reference resistors with different resistance values ​​cover a wide range and can match various test objects from low impedance to high impedance, avoiding the problem that a single reference resistor cannot meet the measurement requirements of different impedances.

[0072] like Figure 2 As shown, when the automatic balancing bridge is in a balanced state, the feedback current Ir flowing through the range resistor module Rr is equal to the test current Ix flowing through the impedance to be measured, Ir=Ix, therefore the voltage Vr across the range resistor module Rr=Ir×Rr=Ix×Rr.

[0073] The test current Ix is determined by the impedance Zx of the impedance to be measured and the voltage Vx across the impedance to be measured, that is, Ix = Vx / Zx.

[0074] Therefore, the formula for calculating the impedance Zx of the impedance to be measured is Zx=(Vx / Vr)×Rr. Since the resistance value of the reference resistor Rr is known, it is only necessary to measure the ratio of Vx to Vr and multiply the ratio of Vx to Vr by the resistance value of the reference resistor Rr to obtain the impedance Zx of the impedance to be measured, thus realizing the measurement of the impedance to be measured.

[0075] In this embodiment, the voltage measurement module 3 is used to measure the voltage signals across the impedance to be measured 13 and the range resistor module 14.

[0076] In an alternative embodiment, to avoid tracking errors between the two voltmeters, Vx and Vr can be measured by alternating the use of a single vector voltmeter. Therefore, the voltage measurement module 3 includes a third switching element and a voltage measurement element.

[0077] Specifically, the first input terminal of the third switching element is connected between the impedance to be measured 13 and the first excitation source 11, the second input terminal is connected between the range resistor module 14 and the second excitation source 12, and the output terminal is connected to the voltage measuring element, which is used to acquire the first voltage signal of the impedance to be measured 13 or the second voltage signal of the range resistor module 14 based on the switching control signal.

[0078] Figure 3 This is a schematic diagram of a current measurement module provided in an embodiment of this application, as shown below. Figure 3 As shown, in one possible embodiment, the current measurement module 2 includes a measurement input cable 21, a current amplification unit 22, and a potential synchronization unit 23.

[0079] In this embodiment, the measurement input cable 21 serves as the core signal transmission carrier between the bridge and the current amplification unit 22. It is specifically designed for the weak characteristics of the fA-level unbalanced current between the impedance to be measured 13 and the range resistor module 14. It adopts a three-layer coaxial shielding structure. Through precise material selection and structural optimization, it achieves low-loss and low-interference transmission of weak current signals, laying the foundation for the high-precision measurement of the subsequent current amplification unit 22.

[0080] like Figure 3 As shown, the three-layer coaxial structure of the measurement input cable 21 consists of a center signal line 213, an inner shielding layer 212, and an outer shielding layer 211 from the inside out, with each layer isolated by a high-insulation material.

[0081] Specifically, the center signal line 213 is a direct transmission channel for weak current. To avoid loss and noise introduction during signal transmission, the signal line is made of low-noise, high-purity copper material, which can effectively reduce the resistance loss and thermal noise of the conductor itself. The diameter of the center signal line 213 can be 0.1-0.5mm. While ensuring mechanical strength, the resistance of the transmission path is minimized. Its core function is to accurately detect the unbalanced current between the impedance to be measured 13 and the range resistor module 14, and transmit the weak current signal to the input terminal of the current amplification unit 22 without distortion.

[0082] The inner shielding layer 212, located outside the center signal line 213, primarily serves to eliminate capacitive coupling interference between the center signal line 213 and the outer shielding layer 211. Specifically, it is composed of a high-density woven copper mesh, which can tightly adhere to the outside of the center signal line 213 to form a continuous protective layer. To further enhance insulation performance, fluoroplastic is used as the insulating material between the inner shielding layer 212 and the center signal line 213. This material has a dielectric constant ≤2.1, which is much lower than that of conventional insulating materials. It can significantly reduce interlayer parasitic capacitance, avoid attenuation or distortion of weak current signals caused by capacitive coupling, and ensure the potential stability of the center signal line 213.

[0083] The outer shielding layer 211, as the outermost protective structure of the cable, adopts a composite structure of double-layer braided copper mesh and aluminum foil. The double-layer braided copper mesh can effectively block the intrusion of high-frequency electromagnetic radiation in space, while the aluminum foil layer can form complete shielding against low-frequency electromagnetic interference. The two work together to achieve full-band electromagnetic shielding coverage. At the same time, the outer shielding layer 211 is directly connected to the system chassis ground, which can quickly conduct the electromagnetic interference signals captured by the shield to the ground, completely cutting off the coupling path of the interference signals to the central signal line 213, and creating a clean electromagnetic environment for the transmission of weak current.

[0084] Furthermore, the insulation material between each layer of the cable is uniformly made of polytetrafluoroethylene (PTFE) or irradiated cross-linked polyethylene (XLPE). Both materials possess excellent insulation properties and chemical stability, and their volume resistivity is greater than 10 Ω·cm. 16 The current is Ω·cm, which can minimize the leakage current between layers, avoid the shunting of weak current signals caused by interlayer leakage current, and ensure that the current signal input to the current amplification unit 22 is completely consistent with the unbalanced current being measured.

[0085] In one possible embodiment, the potential synchronization unit 23 includes a shielding layer driving structure and a compensation structure.

[0086] Specifically, the first input terminal of the shielding layer driving structure is connected to the input terminal of the current amplification unit 22, and the output terminal is connected to the inner shielding layer 212, used to output a driving signal to drive the potential synchronization of the inner shielding layer 212 and the center signal line 213. A compensation structure is connected between the second input terminal and the output terminal of the shielding layer driving structure, used to compensate for the phase and amplitude of the driving signal based on the length of the measurement input cable 21.

[0087] In this application, the unbalanced weak current of the automatic balancing bridge is collected by using a three-coaxial cable, and the signal is amplified in conjunction with the current amplification unit 22. At the same time, the potential synchronization unit 23 makes the inner shielding layer 212 and the center signal line 213 at the same potential to cancel transmission interference. After the bridge is balanced, the voltage signals of the impedance to be measured 13 and the range resistor module 14 are measured synchronously to finally realize the impedance calculation, which solves the problems of difficult extraction and easy distortion of weak signals in traditional automatic balancing bridges.

[0088] Figure 4 This is a schematic diagram of a first current amplification unit provided in an embodiment of this application, as shown below. Figure 4 As shown, in an optional embodiment, the current amplification unit 22 is the core unit for processing weak current signals in this application. Its core task is to accurately convert the fA-level unbalanced current signal transmitted by the measurement input cable 21 into a voltage signal that can be processed subsequently. At the same time, it realizes multi-range gain adjustment to adapt to the measurement needs of weak currents of different amplitudes. Therefore, the current amplification unit 22 includes a first amplification structure and a range adjustment structure.

[0089] Specifically, the first amplification structure includes a first amplification element. The input terminal of the first amplification element is the input terminal of the current amplification unit and is directly connected to the center signal line 213 of the measurement input cable 21, converting the weak current signal into a voltage signal.

[0090] Because the input signal is an extremely weak current in the fA range, extremely high requirements are placed on the input impedance, bias current, and noise characteristics of the amplification element. Therefore, the first amplification element in this application is the JFET operational amplifier OPA656, which has excellent low noise and high impedance characteristics, with an input impedance greater than 10 Ω. 15 Ω can minimize the shunt loss of the input signal; at the same time, its input bias current is less than 0.1fA, which is far below the level of the measured signal, effectively avoiding the interference of the bias current on the measured signal and ensuring the accuracy of the current-to-voltage conversion.

[0091] Figure 5 This is a circuit diagram of a first current amplification unit provided in an embodiment of this application, as shown below. Figure 5 As shown, the inverting input terminal of the OPA656 is connected to the center signal line 213 as the signal input terminal, the non-inverting input terminal is grounded, and the output terminal is connected to the range adjustment structure, forming a basic transimpedance amplification circuit.

[0092] The range adjustment structure includes a first switching element and multiple feedback resistors with different resistance values. The first end of each feedback resistor is connected to the input terminal of the first amplification structure, and the second end is connected to the first end of the first switching element. The second end of the first switching element is connected to the output terminal of the first amplification structure, and the feedback resistors are switched based on the range control signal.

[0093] The range adjustment structure changes the gain of the first amplification structure by switching the value of the feedback resistor connected to the transimpedance amplification circuit, thereby enabling the adaptive measurement of weak current signals of different amplitudes.

[0094] In the embodiments of this application, multiple high-resistance resistors and matching compensation capacitors form a range adjustment structure, which is the feedback network of OPA656, and determines the transimpedance amplification gain and bandwidth.

[0095] Among them, high-resistance resistors, as the core gain control components, are vacuum-sealed or glass-encapsulated. This encapsulation method can effectively isolate the influence of environmental humidity and temperature changes on resistor performance, and their resistance range covers 10. 6 -10 12 The resistor has a gain rating of Ω, which can meet the needs of multiple gain levels from low to high; at the same time, the temperature coefficient of the resistor is less than 50ppm / ℃, ensuring that the resistance value is stable over a wide temperature range and avoiding gain errors caused by temperature drift.

[0096] In one alternative embodiment, the range adjustment structure further includes multiple capacitors connected in parallel across the feedback resistor.

[0097] To balance the bandwidth characteristics of feedback resistors with different resistance values, compensation capacitors are connected in parallel across some high-resistance feedback resistors. Polypropylene film capacitors are selected as compensation capacitors. These capacitors have the characteristics of low loss and high stability, with a capacitance range of 0.5-5pF. By connecting them in parallel with the feedback resistors, the cutoff bandwidth of the system can be set, suppressing circuit self-oscillation caused by high-frequency noise and parasitic parameters, and ensuring the stability and fidelity of signal amplification at different gain levels.

[0098] The first switching element of this application is configured as a precision relay switch consisting of several relays. By switching different feedback resistors through the precision relay switch, multi-range gain selection can be achieved.

[0099] Each precision relay is controlled by a range control signal (GAIN_SET gain setting terminal in the input diagram). Through the logic control of this signal, the precise connection of different feedback resistors can be achieved to meet the measurement requirements of current signals with different amplitudes (fA level).

[0100] like Figure 5 As shown in the diagram, the signal input is pin 4 of the OPA656, and the signal output is pin 1 of the OPA656. There are four gain levels: 100Ω, 10KΩ, 1MΩ, and 100MΩ, corresponding to gains of 6dB, 46dB, 86dB, and 126dB respectively.

[0101] When the relay connects R756 as the feedback resistor to OPA656, the feedback resistor of the first amplification structure is R756 in the figure, the input resistors are R761 and R762 in the figure, and the gain is R756 / (R761+R762)=100Ω / (24.9Ω+24.9Ω)=6dB.

[0102] When the relay connects R757 as the feedback resistor to the OPA656, the feedback resistor of the first amplification structure is R757 in the figure, the input resistors are R761 and R762 in the figure, and the gain is R757 / (R761+R762)=10KΩ / (24.9Ω+24.9Ω)=46dB.

[0103] When the relay connects R754 as the feedback resistor to the OPA656, the feedback resistor of the first amplification structure is R754 in the figure, the input resistors are R761 and R762 in the figure, and the gain is R754 / (R761+R762)=1MΩ / (24.9Ω+24.9Ω)=86dB.

[0104] When the relay connects R755 as the feedback resistor to the OPA656, the feedback resistor of the first amplification structure is R755 in the figure, the input resistors are R761 and R762 in the figure, and the gain is R755 / (R761+R762)=100MΩ / (24.9Ω+24.9Ω)=126dB.

[0105] Figure 6 This is a schematic diagram illustrating the effect of a first enlarged structure provided in an embodiment of this application. Figure 6 When the range of the first amplification structure is 100Ω, with a 100KHz, 1Vpp sine wave input and an external 100Ω resistor, the output waveform of pin 1 of the OPA656 is as follows.

[0106] Figure 7 This is a circuit diagram of a current amplification unit provided in an embodiment of this application. In an optional embodiment, the current amplification unit 22 further includes a second amplification structure to further amplify the voltage signal converted by the first amplification structure.

[0107] like Figure 7 As shown, the second amplification structure includes a second switching element, a second amplification element, and a first peripheral resistor structure; the second switching element is used to receive and connect different first peripheral resistor structures to the second amplification element based on the amplification control signal, so that the second amplification element amplifies the signal by different factors.

[0108] The second amplifying element in this application is configured as AD8138, with signal inputs at pins 1 and 8 of AD8138, signal outputs at pins 4 and 5 of AD8138, and a gain of 0dB or 20dB. Relay K33 is used to switch the gain between 0dB and 20dB.

[0109] When the common pins 3 and 6 of relay K33 are connected to pins 2 and 7 respectively, the feedback resistors of the second amplification structure are R766 and R768 in the figure, the input resistors are R769 and R770 in the figure, and the gain is (R769+R770) / (R766+R768)=(909Ω+909Ω) / (100Ω+100Ω)=20dB;

[0110] When the common pins 3 and 6 of relay K33 are connected to pins 4 and 5 respectively, the feedback resistors of the second amplification structure are R766, R768 and R769 in the figure, the input resistor is R770 in the figure, and the gain is R770 / (R766+R768+R769)=909Ω / (100Ω+100Ω+909Ω)=0dB.

[0111] Figure 8 This is a schematic diagram illustrating the effect of a second enlarged structure provided in an embodiment of this application. Figure 1 , Figure 8 It is the output waveform after amplifying a 100kHz, 1Vpp sine wave by 0dB when the gain of the second amplification structure is 0dB. Figure 9 This is a schematic diagram illustrating the effect of a second enlarged structure provided in an embodiment of this application. Figure 2 , Figure 9 The output waveform is obtained by amplifying a 100kHz, 10mVpp sine wave by 20dB when the second amplification structure is 20dB.

[0112] Figure 10 This is a schematic diagram of a shielding layer driving structure provided in an embodiment of this application. In an optional embodiment, the shielding layer driving structure includes a unity-gain buffer. The unity-gain buffer serves as the core signal processing unit. Its first input terminal is directly connected to the input terminal of the first amplifying element, i.e., the virtual ground point of the transimpedance amplifier, for acquiring the potential of the core signal node. The output terminal is connected to the inner shielding layer 212 of the triaxial cable. By sampling the input signal potential in real time, the inner shielding layer 212 is driven to maintain the same potential as the center signal line 213, so that the voltage difference ΔV between the two is ≤1mV, thereby eliminating the displacement current caused by the distributed capacitance.

[0113] Figure 11This is a circuit diagram of a shielding layer driving structure provided in an embodiment of this application. A unity-gain buffer needs to achieve potential sampling, signal replication, and shielding layer driving, and must simultaneously meet three key requirements: high input impedance, low output impedance, and ultra-low bias current. Based on this, this application uses a JFET (Junction Field-Effect Transistor) input stage operational amplifier AD8091 to construct a unity-gain buffer. The input bias current of AD8091 is less than 1fA, far lower than the measured fA-level current signal. Even if directly connected to the sensitive input node of a transimpedance amplifier, it will not cause shunt loss to the weak current signal, ensuring the authenticity of the sampled potential. The output impedance of the buffer is less than 1Ω, possessing extremely strong capacitive load driving capability, and can directly match the capacitive load characteristics of the inner shielding layer 212 of a three-coaxial cable (typically 50-500pF / meter). Even when connected to a cable several meters long, it can ensure stable transmission of the driving signal and accurate potential control. The amplifier operates in unity-gain mode, with a stable gain close to 1, enabling precise replication of the potential signal of the sampling node, ensuring potential synchronization between the inner shielding layer 212 and the center signal line 213.

[0114] In the signal sampling stage, a direct same-source sampling design is adopted. The first input terminal of AD8091 is directly connected to the virtual ground of the transimpedance amplifier. This node is the core node for transmitting ultra-weak current in the center signal line 213, ensuring that the sampling potential is completely consistent with the potential of the center signal line 213.

[0115] In the signal replication stage, relying on the precise unity-gain characteristic of the AD8091 operational amplifier, the sampled potential signal is replicated into a drive signal without distortion, providing a precise signal source for subsequent potential synchronization control.

[0116] The core principle for eliminating parasitic capacitance interference is based on the fundamental formula for capacitor current: i = C × dV / dt, where i is the current flowing through the capacitor, C is the capacitance, and dV is the voltage difference across the capacitor. In a triaxial cable, a distributed capacitance C_cable naturally exists between the center signal line 213 and the inner shielding layer 212. If a voltage difference dV exists between them, a charging and discharging current i will be generated. This current will directly shunt the weak measured current in the fA range, leading to serious measurement errors.

[0117] This application uses a drive signal output through a unity-gain buffer to force the potential of the inner shielding layer 212 to constantly follow the potential change of the center signal line 213, keeping the voltage difference ΔV between them within 1mV, i.e., dV≈0. Based on the above formula, the charging and discharging current i flowing through the distributed capacitance C_cable is approximately 0 at this time. The parasitic capacitance, which originally had a significant impact on measurement accuracy, is completely "neutralized," as if it has disappeared from the circuit. It no longer shuns the weak current signal, nor does it form a low-pass filter with the feedback resistor of the subsequent amplification module to limit the system bandwidth.

[0118] In traditional cable shielding designs, the shielding layer is typically grounded directly. This makes the shielding layer a capacitance to ground, creating a passive source of interference, which is extremely detrimental to the transmission of ultra-weak signals. However, in the shielding layer driving strategy of this application, the shielding layer is completely transformed into an active control electrode. It is no longer a simple, silent protective layer, but an active layer controlled by the input signal itself. Its potential state is dynamically adjusted by an internal unity-gain buffer, enabling it to actively adapt to changes in the input signal and precisely neutralize the negative impact of its own capacitance. This represents a fundamental upgrade from "passive protection" to "active control."

[0119] In real-world applications, no operational amplifier is ideal. Unity-gain buffers inevitably experience phase delay and gain roll-off at high frequencies. This means that the voltage on the shield cannot perfectly and instantaneously follow changes in the input signal. Tiny potential differences can reintroduce the effects of parasitic capacitance at high frequencies, potentially leading to stability issues such as system oscillations.

[0120] To mitigate performance losses caused by non-ideal components, a compensation structure is incorporated between the input and output of the unity-gain buffer. Specifically, the second input of the unity-gain buffer is connected to the first end of the compensation structure, while the second end of the compensation structure feeds back to the output of the unity-gain buffer, forming a closed-loop compensation circuit to ensure the accuracy and stability of the drive signal.

[0121] The compensation structure specifically includes a compensation resistor, a compensation capacitor, and an adjustable capacitor. One end of the compensation resistor is connected to the second input terminal of the unity-gain buffer, and the other end forms a common node with one end of the compensation capacitor. The other end of the compensation capacitor is connected to the output terminal of the unity-gain buffer. One end of the adjustable capacitor is connected to the common node of the compensation resistor and the compensation capacitor, and the other end is directly grounded, forming a flexibly adjustable phase compensation branch.

[0122] Through the aforementioned precise RC compensation network, on the one hand, the fixed RC combination of the compensation resistor and the compensation capacitor ensures that the buffer gain is as close to 1 as possible throughout the entire target frequency band, achieving amplitude matching; on the other hand, the dynamic adjustment of the adjustable capacitor minimizes the phase difference between the buffer input and output, achieving phase matching. The basic compensation link of the compensation structure consists of a compensation resistor and a compensation capacitor connected in series, where the resistance value of the compensation resistor is set to a range of 10-100Ω, and the capacitance value of the compensation capacitor is set to a range of 2-10pF. This RC series network can achieve basic amplitude matching and phase calibration within the target frequency band, ensuring that the buffer gain is stably close to 1. The adjustable capacitor serves as a dynamic compensation element, and its capacitance value can be flexibly adjusted through the compensation adjustment signal. The adjustment logic is directly related to the length of the measurement input cable 21: the longer the cable, the larger its distributed capacitance, and the greater the phase offset compensation required by the unity-gain buffer. In this case, the capacitance value of the adjustable capacitor needs to be increased through the compensation adjustment signal to improve the phase lead compensation effect and ensure that the phase margin of the module is always within a safe range.

[0123] This dual compensation design solves the non-ideal characteristics of unity-gain buffers in practical applications. Even at very high frequencies, the shielding layer drive can still work effectively, avoiding the phase delay and gain roll-off problems that are prone to occur at high frequencies, and preventing the residual potential difference and system instability risks caused by these issues.

[0124] Through the aforementioned shielding drive structure and compensation structure, the bandwidth of the entire automatic balancing bridge is no longer limited by the distributed capacitance of the detector and cable, but is mainly determined by the gain-bandwidth product of the operational amplifier in the current amplification unit 22, significantly improving the measurement capability of high-frequency weak current signals. Even when connected to cables several meters long or detectors with huge capacitance, the system will not oscillate, exhibiting strong environmental adaptability. In actual use, users do not need to carefully calculate and compensate capacitance parameters for different detectors or cables of different lengths; they only need to adjust the compensation adjustment signal of the adjustable capacitor according to the cable length, greatly simplifying the system integration process.

[0125] In summary, the shielding layer drive structure, through its innovative design of active potential synchronization and precise phase compensation, completely solves the problem of parasitic capacitance interference in the transmission of ultra-weak current signals. Together with the three-layer shielding structure of the measurement input cable 21 and the high-precision amplification function of the current amplification unit 22, it forms a complete closed-loop protection system, jointly constructing a technical link of "pure signal transmission - precise conversion and amplification - active interference suppression". This provides a solid and reliable technical guarantee for the high-precision impedance measurement of impedance measurement devices based on weak current measurement.

[0126] Continue as Figure 3As shown, in an optional embodiment, the above circuit structure also needs to be mounted on a printed circuit board (PCB). Therefore, the impedance measuring device based on weak current measurement also includes a PCB. A protective ring 4 is provided on the PCB. The protective ring 4 is a conductive ring surrounding the high-impedance input node of the current amplification unit. The high-impedance input node includes the input terminal of the first amplification element and the input terminal of the range adjustment structure.

[0127] The protective ring 4 is connected to the output end of the shielding layer drive structure and is synchronized with the potential of the inner shielding layer 212 and the center signal line 213.

[0128] The high-impedance input node includes the input terminal of the first amplifying element (i.e., the virtual ground of the transimpedance amplifier) ​​and the input terminal of the range adjustment structure. Specifically, it includes the center pin of the input connector, the input side pad of the feedback resistor, the input side pad of the feedback capacitor, and the grounded inverting and non-inverting input terminals of the operational amplifier.

[0129] The aforementioned nodes are critical links in the transmission of weak current signals and are highly susceptible to surface leakage current. The potential terminal of the guard ring 4 is connected to the output terminal of the shielding layer driving structure, which can follow the potential changes of the driving signal in real time and achieve potential synchronization with the inner shielding layer 212 and the center signal line 213, forming an equipotential protection ring around the high-impedance node. This can effectively block the leakage current path on the PCB board surface and prevent leakage current from shunting the weak current signal.

[0130] Figure 12 This is a schematic diagram of a PCB protection ring layout provided in an embodiment of this application, as shown below. Figure 12 As shown, the protection ring 4 forms a high-impedance island region, while the outside is a low-impedance region where output traces, power supplies, and digital lines are installed.

[0131] This application uses a polytetrafluoroethylene PCB substrate, the protective ring 4 is made of copper, the creepage distance between it and the input node is >3mm, the surface is treated with immersion gold and the solder mask layer is removed.

[0132] Continue as Figure 3 As shown, in one optional embodiment, a cutout area 5 is provided on the PCB board. The cutout area 5 is located between the interface of the measurement input cable 21 and the current measurement module 2. It is a physical isolation area filled with highly insulating material, used to cut off the surface leakage current path between the measurement input cable 21 and other circuit modules. By physically disconnecting the conductor connection, the surface leakage current path that may exist between the interface of the measurement input cable 21 and other circuit modules is cut off. At the same time, the near-field electromagnetic coupling interference between the input side and the subsequent circuit is reduced, creating a clean physical channel for the transmission of weak current signals from the cable interface to the current amplification unit.

[0133] By optimizing the structure of the protective ring 4 and the hollowed-out area 5, leakage and interference paths are blocked from a physical perspective, forming a dual guarantee of electrical protection and physical isolation with the shielding layer drive structure.

[0134] In other possible embodiments, the current measurement module 2 described above can also be applied in high-speed photoelectric detection scenarios, specifically in fields such as laser communication, spectral analysis, and quantum optics, where the core measurement object is the ultra-weak photocurrent output by the photodetector.

[0135] The specific triaxial cable configuration is a 4-meter low-noise triaxial cable: as the signal transmission carrier, the outer shielding layer 211 of the triaxial structure is grounded, and the inner shielding layer 212 is synchronized with the potential by the shielding drive module, which can effectively block electromagnetic interference in the 4-meter transmission path. The first amplification element is configured as an amplifier with a transimpedance gain of 107V / A (10MΩ). The transimpedance amplifier circuit constructed with a 10MΩ feedback resistor converts fA-level current into mV-level voltage. The shielding drive module is based on AD4898-1, which is a high-bandwidth, high-drive-capacity buffer chip. Its 50MHz bandwidth is much higher than the system's 100kHz measurement bandwidth, ensuring no phase delay in the drive signal. The ±30mA output current can easily drive the capacitive load of the inner shielding layer 212 of the 4-meter triaxial cable, realizing the potential synchronization between the inner shielding layer 212 and the center signal line 213, completely eliminating signal shunting caused by distributed capacitance, and ensuring the integrity of signal transmission within the 100kHz bandwidth.

[0136] Through the collaborative design of low-noise transmission, broadband amplification, and precise shielding drive, the core performance of "-3dB bandwidth 100kHz, full bandwidth equivalent input noise ≤50fA" is achieved, perfectly adapting to high-speed photoelectric detection scenarios.

[0137] In another possible embodiment, the aforementioned current measurement module 2 can also be applied to a multi-channel synchronous measurement system, specifically in a high-precision bioelectrical signal acquisition scenario. This scenario primarily targets the acquisition of bioelectrical signals such as electroencephalogram (EEG), electromyography (EMG), and electrocardiogram (ECG). The core requirements are multi-channel synchronization, strong common-mode rejection, and ultra-low crosstalk. The multi-channel synchronous measurement system adopts a 4-channel independent shielded drive architecture. Each measurement channel is equipped with an independent shielded drive structure. Independent driving prevents interference from a single channel from spreading to other channels through the drive link. The 4 channels share a reference voltage and clock signal, and the crosstalk between channels is <-120dB.

[0138] Figure 13 This is a bandwidth comparison curve between a conventional solution and the solution of this application, provided in an embodiment of this application. Figure 14This is a comparison chart of leakage current testing under different cable lengths provided in the embodiments of this application. Compared with the traditional dual-coaxial scheme, the tri-coaxial shielded drive scheme of this invention has significant advantages: In terms of the measurement lower limit, the traditional scheme can only reach 100fA, while this invention raises the measurement lower limit to 0.1fA, improving accuracy by 1000 times; Regarding the influence of cable capacitance, the bandwidth of the traditional scheme is inversely proportional to the cable capacitance, while this invention achieves bandwidth that is basically independent of cable length, improving bandwidth stability by 10-100 times; In terms of common-mode rejection capability, the common-mode rejection ratio of the traditional scheme at 50Hz is 80-100dB, while this invention improves it to 120-140dB, enhancing the common-mode interference resistance by 100-1000 times; Regarding the leakage current problem of long cables, the leakage current of the traditional scheme reaches 1pA-1nA, while this invention controls it below 0.1fA, improving the leakage current suppression effect by 10 times. 4 -10 7 In terms of temperature stability, the traditional solution is 10 fA / ℃, while this invention optimizes it to 0.1 fA / ℃, improving temperature drift control capability by 100 times.

[0139] In summary, this invention, through its innovative design of a three-coaxial shielded drive, achieves a performance leap that is difficult for traditional solutions to match in core dimensions such as measurement accuracy, bandwidth stability, anti-interference capability, leakage current suppression, and temperature stability, making it more suitable for high-precision measurement scenarios of fA-level ultra-weak currents.

[0140] The following describes a specific embodiment of an impedance measurement method according to this application. Figure 15 This is a flowchart illustrating an impedance measurement method provided in an embodiment of this application. Figure 1 This specification provides method operation steps as shown in the embodiments or flowcharts, but based on conventional or non-inventive labor, more or fewer operation steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only execution order. In actual system or server products, the methods shown in the embodiments or drawings can be executed sequentially or in parallel (e.g., in a parallel processor or multi-threaded processing environment). Specifically, as shown in the embodiments or drawings... Figure 15 As shown, it may include:

[0141] S201: Determine the reference resistance value of the range resistance module based on the impedance to be measured.

[0142] S202: Use the current measurement module to obtain the unbalanced current between the impedance to be measured and the range resistance module.

[0143] S203: The compensation structure is used to compensate for the phase and amplitude offset of the unbalanced current based on the length of the measurement input cable, and the compensated unbalanced current is determined as the unbalanced current.

[0144] S204: If the unbalanced current is not zero, generate a balance adjustment signal based on the unbalanced current using the balance adjustment module, adjust the second excitation source based on the balance adjustment signal, and obtain the adjusted unbalanced current; or; if the unbalanced current is zero, obtain the first voltage signal across the impedance to be measured and the second voltage signal of the range resistor module.

[0145] S205: Determine the impedance value of the impedance to be measured based on the first voltage signal, the second voltage signal, and the reference resistance value.

[0146] Figure 16 This is a flowchart illustrating an impedance measurement method provided in an embodiment of this application. Figure 2 The method may include:

[0147] S301: Determine the reference resistance value of the range resistance module based on the impedance to be measured.

[0148] In one possible embodiment, based on the estimated range of the impedance to be measured, a resistor with a magnitude close to that of the impedance to be measured is selected as the reference resistor Rr from among a plurality of reference resistors with different resistance values ​​in the range resistor module.

[0149] By performing the above operations, the current flowing through the impedance to be measured and the reference resistor are on the same order of magnitude, resulting in higher detection accuracy of subsequent unbalanced current and voltage signals and avoiding signal distortion caused by range mismatch.

[0150] S302: Use the current measurement module to obtain the unbalanced current between the impedance to be measured and the range resistance module.

[0151] S303: The compensation structure compensates for the phase and amplitude offset of the unbalanced current based on the length of the measurement input cable, and the compensated unbalanced current is determined as the unbalanced current.

[0152] The distributed capacitance of a cable increases with its length, which can shunt unbalanced current signals, especially high-frequency components, causing signal amplitude attenuation. The longer the cable, the greater the attenuation. Similarly, the distributed inductance of a cable increases with its length, causing phase lag in signal transmission. The phase lag is more significant for high-frequency signals, with the phase lag of a 4-meter cable reaching 3-5 times that of a low-frequency signal.

[0153] Therefore, it is necessary to compensate for the phase and amplitude shifts of the unbalanced current.

[0154] In one possible embodiment, the compensation structure consists of a fixed RC compensation network and an adjustable capacitor adjustment branch, which work together to complete the compensation.

[0155] The fixed RC compensation network consists of a compensation resistor with a fixed resistance and a compensation capacitor with a fixed capacitance, connected in series, used for fundamental amplitude compensation. Its parameters have been optimized according to the target measurement frequency band and can offset the fundamental amplitude attenuation of cables of conventional length.

[0156] The adjustable capacitor has a capacitance range of 1-4.7pF. One end is connected to the RC network node and the other end is grounded. Its core function is to receive the compensation adjustment signal and dynamically change the capacitance value to achieve accurate compensation for phase shift. The core basis for the adjustment signal is the length of the input cable.

[0157] In this embodiment of the application, a phase amplitude detection unit can also be set at the cable output end to collect the unbalanced current signal after initial compensation in real time, compare it with the input standard signal, and calculate the real-time offset.

[0158] If the offset exceeds the threshold, a fine-tuning command is generated, and a compensation adjustment signal is output through the D / A conversion circuit to change the capacitance value of the adjustable capacitor. For example, when the temperature rises, the distributed capacitance of a 4-meter cable increases, and the phase lag increases from 3.8° to 6.2°, the adjustment signal controls the capacitance value of the adjustable capacitor to increase from 2.3pF to 4.7pF until the offset returns to within the threshold.

[0159] When the phase amplitude detection unit detects that the signal offset is consistently stable within the threshold, it indicates that the compensation has achieved the expected effect. At this time, the compensated unbalanced current signal is determined as the effective unbalanced current and is transmitted to the current amplification unit through the signal isolation circuit for subsequent current-voltage conversion and high-precision amplification.

[0160] S304: Determine if the unbalanced current is zero. If yes, execute S306; otherwise, execute S305.

[0161] S305: Based on the unbalanced current, the balance adjustment module generates a balance adjustment signal, adjusts the second excitation source based on the balance adjustment signal, obtains the adjusted unbalanced current, and executes S304.

[0162] S306: Acquire the first voltage signal across the impedance to be measured and the second voltage signal from the range resistor module.

[0163] If the unbalanced current is not zero, a balance adjustment signal is generated by the balance adjustment module based on the unbalanced current, and the second excitation source is adjusted based on the balance adjustment signal to obtain the adjusted unbalanced current.

[0164] If the unbalanced current is zero, obtain the first voltage signal across the impedance to be measured and the second voltage signal from the range resistor module.

[0165] If the unbalanced current is not zero, an adjustment signal is generated to fine-tune the amplitude or phase of the second excitation source. The unbalanced current after adjustment is repeatedly detected until the current approaches zero, that is, the bridge reaches balance.

[0166] Once the unbalanced current is zero, meaning the automatic balancing bridge has reached a balanced state, the voltage measurement module detects and acquires the first analog voltage signal Vx corresponding to the impedance under test and the second analog voltage signal Vr corresponding to the range resistor module. At this point, the unbalanced interference of the two signals has been eliminated, providing a stable and accurate original signal for subsequent amplification.

[0167] S307: Determine the impedance value of the impedance to be measured based on the first voltage signal, the second voltage signal, and the reference resistance value.

[0168] The formula for calculating the impedance Zx of the impedance to be measured is Zx=(Vx / Vr)×Rr, which is based on the ratio of the first voltage signal Vx to the second voltage signal Vr, multiplied by the known resistance value of the reference resistor Rr, to obtain the impedance Zx of the impedance to be measured, thus realizing the measurement of the impedance to be measured.

[0169] This application also provides an impedance measurement device. Figure 17 This is a schematic diagram of the structure of an impedance measurement device provided in an embodiment of this application, as shown below. Figure 17 As shown, the device 400 includes:

[0170] The first determining module 401 is used to determine the reference resistance value of the range resistance module based on the impedance to be measured.

[0171] The current measurement module 402 is used to obtain the unbalanced current between the impedance to be measured and the range resistance module.

[0172] The compensation module 403 is used to compensate for the phase and amplitude offset of the unbalanced current based on the length of the measurement input cable using the compensation structure, and to determine the compensated unbalanced current as the unbalanced current.

[0173] The voltage measurement module 404 is used to generate a balance adjustment signal based on the unbalanced current using the balance adjustment module if the unbalanced current is not zero, and adjust the second excitation source based on the balance adjustment signal to obtain the adjusted unbalanced current; or; if the unbalanced current is zero, obtain the first voltage signal across the impedance to be measured and the second voltage signal of the range resistor module.

[0174] The second determining module 405 is used to determine the impedance value of the impedance to be measured based on the first voltage signal, the second voltage signal and the reference resistance value.

[0175] The apparatus and method embodiments in this application are based on the same application concept.

[0176] The methods and embodiments provided in this application can be executed on a computer terminal, server, or similar computing device. Taking running on a server as an example, Figure 18 This is a hardware structure block diagram of a server for an impedance measurement method provided in an embodiment of this application. Figure 18 As shown, the server 500 can vary significantly due to different configurations or performance. It may include one or more Central Processing Units (CPUs) 510 (CPUs 510 may include, but are not limited to, microprocessors such as MCUs or programmable logic devices such as FPGAs), a memory 530 for storing data, and one or more storage media 520 (e.g., one or more mass storage devices) for storing application programs 523 or data 522. The memory 530 and storage media 520 may be temporary or persistent storage. The program stored in the storage media 520 may include one or more modules, each module may include a series of instruction operations on the server. Furthermore, the CPU 510 may be configured to communicate with the storage media 520 and execute the series of instruction operations stored in the storage media 520 on the server 500. Server 500 may also include one or more power supplies 560, one or more wired or wireless network interfaces 550, one or more input / output interfaces 540, and / or one or more operating systems 521, such as Windows Server™, Mac OS X™, Unix™, Linux™, FreeBSD™, etc.

[0177] The input / output interface 540 can be used to receive or send data via a network. Specific examples of the network described above may include a wireless network provided by the communication provider of server 500. In one example, the input / output interface 540 includes a network interface controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the input / output interface 540 may be a radio frequency (RF) module used for wireless communication with the Internet.

[0178] Those skilled in the art will understand that Figure 18 The structure shown is for illustrative purposes only and does not limit the structure of the aforementioned electronic device. For example, server 500 may also include... Figure 18 The more or fewer components shown, or having the same Figure 18 The different configurations shown.

[0179] This application provides an electronic device, which includes a processor and a memory. The memory stores at least one instruction, at least one program, code set, or instruction set. The processor loads and executes the at least one instruction, at least one program, code set, or instruction set to implement the above-described data processing method.

[0180] Embodiments of this application also provide a computer-readable storage medium, which can be disposed in a server to store at least one instruction, at least one program, code set, or instruction set related to implementing an impedance measurement method in the method embodiment. The at least one instruction, the at least one program, the code set, or the instruction set is loaded and executed by the processor to implement the impedance measurement method described above.

[0181] Optionally, in this embodiment, the storage medium may be located at at least one of the multiple network servers in a computer network. Optionally, in this embodiment, the storage medium may include, but is not limited to, various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0182] As can be seen from the embodiments of the impedance measurement method, apparatus, electronic device, or storage medium provided in this application, the reference resistance value of the range resistance module is determined based on the impedance to be measured; the unbalanced current between the impedance to be measured and the range resistance module is obtained using a current measurement module; the phase and amplitude offset of the unbalanced current is compensated based on the length of the measurement input cable using a compensation structure, and the compensated unbalanced current is determined as the unbalanced current; if the unbalanced current is not zero, a balance adjustment signal is generated based on the unbalanced current using a balance adjustment module, and the second excitation source is adjusted based on the balance adjustment signal to obtain the adjusted unbalanced current; or; if With zero unbalanced current, the first voltage signal across the impedance to be measured and the second voltage signal from the range resistor module are acquired. Based on the first and second voltage signals and the reference resistance value, the impedance value of the impedance to be measured is determined. The weak unbalanced current of the automatic balancing bridge is collected using a three-coaxial cable, and the signal is amplified in conjunction with the current amplification unit. At the same time, the potential synchronization unit ensures that the inner shielding layer and the center signal line are at the same potential, thus canceling transmission interference. After the bridge is balanced, the voltage signals of the impedance to be measured and the range resistor module are measured synchronously, and finally the impedance is calculated. This solves the problems of difficult extraction and easy distortion of weak signals in traditional automatic balancing bridges.

[0183] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0184] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0185] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0186] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An impedance measurement device based on weak current measurement, characterized in that, Includes an automatic balancing bridge, a current measurement module, and a voltage measurement module; The automatic balancing bridge includes a first excitation source, a second excitation source, a range resistor module, and a balance adjustment module; the voltage measurement module is used to measure the impedance to be measured and the voltage signal of the range resistor module. The current measurement module includes a measurement input cable, a current amplification unit, and a potential synchronization unit; the measurement input cable includes an outer shielding layer, an inner shielding layer, and a center signal line arranged coaxially; the outer shielding layer is grounded; the center signal line is used to detect the unbalanced current between the impedance to be measured and the range resistance module, and inputs it to the current amplification unit; The potential synchronization unit includes a shielding layer driving structure and a compensation structure; the first input terminal of the shielding layer driving structure is connected to the input terminal of the current amplification unit, and the output terminal is connected to the inner shielding layer, for outputting a driving signal to drive the potential synchronization of the inner shielding layer and the center signal line; The compensation structure is connected between the second input terminal and the output terminal of the shielding layer driving structure, and is used to compensate for the phase and amplitude of the driving signal based on the length of the measurement input cable; The shielding layer driving structure includes a unity-gain buffer; The compensation structure includes a compensation resistor, a compensation capacitor, and an adjustable capacitor; One end of the compensation resistor is connected to the second input terminal of the unity-gain buffer, and the other end is connected to one end of the compensation capacitor; the other end of the compensation capacitor is connected to the output terminal of the unity-gain buffer; one end of the adjustable capacitor is connected to the connection node of the compensation resistor and the compensation capacitor, and the other end is grounded; The adjustable capacitor is used to receive and adjust its own capacitance value based on a compensation adjustment signal to compensate for the phase margin; the compensation adjustment signal is determined based on the length of the measurement input cable.

2. The impedance measuring device based on weak current measurement according to claim 1, characterized in that, The current amplification unit includes a first amplification structure and a range adjustment structure; The first amplification structure includes a first amplification element, the input terminal of which is the input terminal of the current amplification unit, used to convert the weak current signal into a voltage signal; The range adjustment structure includes a first switching element and multiple feedback resistors with different resistance values; the first end of the multiple feedback resistors is connected to the input end of the first amplification structure, and the second end is connected to the first end of the first switching element; the second end of the first switching element is connected to the output end of the first amplification structure, and the feedback resistors are switched based on the range control signal.

3. The impedance measuring device based on weak current measurement according to claim 2, characterized in that, The range adjustment structure also includes multiple capacitors; the multiple capacitors are respectively connected in parallel across the two ends of the feedback resistor.

4. An impedance measuring device based on weak current measurement according to claim 2, characterized in that, The current amplification unit also includes a second amplification structure; The second amplification structure includes a second switching element, a second amplification element, and a first peripheral resistor structure; the second switching element is used to receive and connect different first peripheral resistor structures to the second amplification element based on the amplification control signal, so that the second amplification element amplifies the signal by different factors.

5. An impedance measuring device based on weak current measurement according to claim 2, characterized in that, The first input terminal of the unity-gain buffer is connected to the input terminal of the first amplifying element, and the output terminal is connected to the inner shielding layer; the second input terminal of the unity-gain buffer is connected to the first terminal of the compensation structure, and the second terminal of the compensation structure is connected to the output terminal of the unity-gain buffer.

6. An impedance measuring device based on weak current measurement according to claim 2, characterized in that, It also includes a PCB board, on which a protective ring is provided. The protective ring is a conductive ring surrounding the high-impedance input node of the current amplification unit. The high-impedance input node includes the input terminal of the first amplification element and the input terminal of the range adjustment structure. The protective ring is connected to the output terminal of the shielding layer driving structure and is synchronized with the potential of the inner shielding layer and the center signal line.

7. An impedance measuring device based on weak current measurement according to claim 6, characterized in that, The PCB board has a cutout area; the cutout area is located between the interface of the measurement input cable and the current measurement module, and is a physical isolation area filled with high insulation material, used to cut off the surface leakage path between the measurement input cable and other circuit modules.

8. An impedance measuring device based on weak current measurement according to claim 1, characterized in that, The voltage measurement module includes a third switching element and a voltage measurement element; The first input terminal of the third switching element is connected between the impedance to be measured and the first excitation source, the second input terminal is connected between the range resistor module and the second excitation source, and the output terminal is connected to the voltage measuring element, for acquiring the first voltage signal of the impedance to be measured or the second voltage signal of the range resistor module based on the switching control signal.

9. An impedance measurement method, characterized in that, An impedance measuring device based on weak current measurement as described in any one of claims 1-8, comprising: The reference resistance value of the range resistance module is determined based on the impedance to be measured; The unbalanced current between the impedance to be measured and the range resistance module is obtained using the current measurement module. The compensation structure is used to compensate for the phase and amplitude offset of the unbalanced current based on the length of the measurement input cable, and the compensated unbalanced current is determined as the unbalanced current. If the unbalanced current is not zero, a balance adjustment signal is generated by the balance adjustment module based on the unbalanced current, and the second excitation source is adjusted based on the balance adjustment signal to obtain the adjusted unbalanced current; or; if the unbalanced current is zero, the first voltage signal across the impedance to be measured and the second voltage signal of the range resistor module are obtained. The impedance value of the impedance to be measured is determined based on the first voltage signal, the second voltage signal, and the reference resistance value.

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