A method for testing high value resistors with variable square wave excitation and dual feedback loops

Abstract

The present application relates to the field of electronic measurement technology, more particularly, it is especially related to a kind of variable square wave excitation double feedback loop high resistance test method.The device of the present application includes: voltage source, voltage loop, measured resistance, four-wire test cable equivalent resistance, current loop, differential amplification module, sampling end module;Variable square wave excitation double feedback loop high resistance test method includes: S1, constant DC voltage of positive and negative alternation is generated by voltage source;S2, constant DC voltage connects voltage loop;S3, the output of the voltage loop is connected to the measured resistance through test cable;S4, test cable is connected to current loop;S5, current loop output is connected to differential amplification module;S6, differential amplification module output is connected to sampling end module.The present application realizes high-precision weak current detection and stable voltage control, and relies on four-wire structure to provide basis for efficient protection, so as to realize more rapid, more stable, more accurate measurement to extremely high resistance value.

Description

Technical Field

[0001] This invention relates to the field of electronic measurement technology, and more specifically, to a method for testing high-value resistances using a variable square wave excitation dual feedback loop. Background Technology

[0002] In fields such as electronics and materials science, accurate measurement of high-resistance resistors is crucial. For example, (1) in semiconductor device manufacturing, precise measurement of the resistance of insulating layers is required to evaluate their performance. (2) in materials science: the volume resistivity and surface resistivity of insulating materials (plastics, ceramics, glass, composites) are key indicators for evaluating their insulation performance. (3) in electronic components: insulation resistance of capacitors, insulation performance of connectors, verification of high-resistance resistors, etc. (4) in electrochemistry: studying the conductivity of electrolytes (actually measuring the reciprocal of their high resistance). (5) in electrostatic protection: evaluating the resistance characteristics of antistatic materials and devices.

[0003] Traditional high-resistance measuring instruments face several major difficulties in measuring such high resistance values: (1) Weak current detection: According to Ohm's law (R = V / I), when a reasonable voltage is applied (to avoid breakdown), the current flowing through the high resistance is extremely weak (pA, fA or even lower). It is very difficult to accurately measure such a small current, which is easily overwhelmed by noise (thermal noise, shot noise, 1 / f noise), external interference (electromagnetic interference, electrostatic interference) and the input bias current / input noise of the measuring instrument itself. (2) Polarization effect: For some materials (especially those containing ions or electrochemically active), the long-term application of DC voltage will cause the accumulation of internal charge (polarization) in the material, causing the measured current to drift over time, resulting in inaccurate and unstable measurement results. (3) Influence of test fixtures and leads: The insulation resistance of the test fixtures, the resistance of the leads (although they have little effect on the high resistance itself, they have an effect on the measurement circuit), and the distributed capacitance between leads and between leads and ground will introduce errors and delays, especially in AC or transient measurements. (4) Thermal noise: High resistance itself generates significant Johnson-Nyquist thermal noise, which limits the smallest detectable current signal.

[0004] High-resistance measurement faces severe challenges such as weak current, polarization, noise, and leakage. Traditional DC methods are plagued by polarization and low-frequency noise; AC methods are complex and limited at high frequencies; integration methods are time-consuming and have limited dynamic range; while the standard four-wire method eliminates lead resistance, it does not solve the core detection problems and protection requirements. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the purpose of this invention is to propose a high-value resistance testing method with a variable square wave excitation dual feedback loop, achieving faster, more stable, and more accurate measurement of extremely high resistance values.

[0006] To achieve the above and other related objectives, the present invention provides a method for testing high-value resistance using a variable square wave excited dual feedback loop, comprising a high-value resistance testing device using a variable square wave excited dual feedback loop, wherein the high-value resistance testing device using a variable square wave excited dual feedback loop includes: Voltage source; and A voltage loop, the input of which is connected to the voltage source; The resistor under test has one end connected to the output terminal of the voltage loop via the equivalent resistance of a four-wire test cable, and the other end connected to the input terminal of the current loop via the equivalent resistance of a four-wire test cable. A differential amplifier module, the input of which is connected to the output of the current loop, and the output of the differential amplifier module is connected to the sampling module; The high-value resistance testing method for the variable square wave excited dual feedback loop includes: S1. A constant DC voltage with alternating positive and negative values ​​is generated by a voltage source; S2, constant DC voltage connection to voltage loop; S3. The output of the voltage loop is connected to the resistor under test via a test cable; S4. The test cable is connected to the current loop; S5. The current loop output is connected to the differential amplifier module; S6. The output of the differential amplifier module is connected to the sampling terminal module.

[0007] In one embodiment of the present invention, the voltage loop includes: a voltage follower circuit, a voltage proportional adjustment circuit, an integrator circuit, and a non-inverting proportional operational circuit. The voltage follower circuit includes an operational amplifier U1; the voltage proportional adjustment circuit includes resistors Rs1 and Rs2; the integrator circuit includes an operational amplifier U2, resistors R1, R2, and R3, and a capacitor C1; the non-inverting proportional operational circuit includes an operational amplifier U3, resistors R4 and R5. One end of resistor Rs1 is connected to the voltage source, and the other end of resistor Rs1 is connected to one end of resistor Rs2, the inverting input terminal of operational amplifier U2, and one end of resistor R1. The other end of resistor Rs2 is connected to the output terminal and the inverting input terminal of operational amplifier U1. The non-inverting input terminal of operational amplifier U1 is connected to the equivalent resistance of the four-wire test cable. The other end of resistor R1 is connected to one end of capacitor C1. The other end of capacitor C1 is connected to the output terminal of operational amplifier U2 and one end of resistor R2. The other end of resistor R2 is connected to one end of resistor R3 and the non-inverting input terminal of operational amplifier U3. The output terminal of operational amplifier U3 is connected to the equivalent resistance of the four-wire test cable and one end of resistor R4. The other end of resistor R4 is connected to one end of resistor R5 and the inverting input terminal of operational amplifier U3. The other end of resistor R5 is grounded.

[0008] In one embodiment of the present invention, one end of the resistor under test Rx is connected to one end of the equivalent resistance Rw1 and one end of the equivalent resistance Rw3 of the four-wire test cable. The other end of the equivalent resistance Rw1 is connected to the non-inverting input terminal of the operational amplifier U1. The other end of the equivalent resistance Rw3 is connected to the output terminal of the operational amplifier U3. The other end of the resistor under test Rx is connected to the equivalent resistance Rw2 and the equivalent resistance Rw4 of the four-wire test cable. The other ends of the equivalent resistance Rw2 and the equivalent resistance Rw4 are connected to the current loop.

[0009] In one embodiment of the present invention, the current loop includes a voltage follower circuit, a sampling resistor, and an integrator circuit. The voltage follower circuit includes an operational amplifier U4, the sampling resistor is Rb, and the integrator circuit includes an operational amplifier U5 and a capacitor C2. The other end of the equivalent resistance Rw2 of the four-wire test cable is connected to the non-inverting input terminal of the operational amplifier U4 and one end of the sampling resistor Rb. The other end of the equivalent resistance Rw4 of the four-wire test cable is connected to the inverting input terminal of the operational amplifier U5 and one end of the capacitor C2. The inverting input terminal of the operational amplifier U4 is connected to the output terminal and connected to a differential amplifier module. The other end of the sampling resistor Rb is connected to the output terminal of the operational amplifier U5, the other end of the capacitor C2, and the differential amplifier module.

[0010] In one embodiment of the present invention, the differential amplifier module includes an operational amplifier U6, resistors Rd1, Rd2, Rd3, and Rd4. One end of resistor Rd1 is connected to the output terminal of operational amplifier U4, and the other end of resistor Rd1 is connected to one end of resistor Rd2 and the non-inverting input terminal of operational amplifier U6. The other end of resistor Rd2 is grounded. One end of resistor Rd3 is connected to the output terminal of operational amplifier U5, and the other end of resistor Rd3 is connected to the inverting input terminal of operational amplifier U6 and one end of resistor Rd4. The other end of resistor Rd4 is connected to the output terminal of operational amplifier U6.

[0011] In one embodiment of the present invention, the sampling end module includes a filtering circuit and an analog voltage signal acquisition module, wherein the analog voltage signal acquisition module includes an ADC module.

[0012] In one embodiment of the present invention, the resistor R1 and capacitor C1 of the operational amplifier U2 provide phase compensation for the operational amplifier U2.

[0013] In one embodiment of the invention, the sampling resistor Rb provides a feedback path for the current loop.

[0014] In one embodiment of the present invention, the differential amplifier gain calculation formula composed of operational amplifier U6 and resistors Rd1, Rd2, Rd3, and Rd4 is as follows: .

[0015] As described above, the high-value resistance testing method of the variable square wave excitation dual feedback loop of the present invention has the following beneficial effects: The present invention provides a high-value resistance testing method with variable square wave excitation dual feedback loop. It achieves high-precision weak current detection and stable voltage control through a precision dual feedback loop, and provides a foundation for efficient protection based on a four-wire structure, thereby enabling faster, more stable and more accurate measurement of extremely high resistance values.

[0016] The present invention discloses a high-value resistor testing method with variable square wave excitation and dual feedback loop. Under the drive of a square wave voltage source with alternating positive and negative signals, a bidirectional current excitation is generated through a current loop to sample the high-value resistor. Its core advantage lies in significantly suppressing low-frequency noise and DC drift, thereby improving the accuracy and stability of the measurement.

[0017] The present invention provides a high-value resistance testing method with variable square wave excitation dual feedback loop, which combines AC excitation with differential amplification and synchronous detection to suppress interference unrelated to the excitation frequency. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the test device structure for a high-value resistance test method with variable square wave excitation dual feedback loop according to an embodiment of the present invention. Detailed Implementation

[0019] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0020] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0021] Terms such as "first" or "second" may be used to describe various components, but these components are not limited by the terms described above. The terms described above are used to distinguish one component from another; for example, without departing from the scope of the concept according to this disclosure, a first component may be referred to as a second component, and similarly, a second component may be referred to as a first component.

[0022] Furthermore, "connected / linked" indicates that one component is directly electrically connected to another component or indirectly electrically connected through another component. Unless otherwise explicitly stated in the sentence, the singular form may include the plural form. Additionally, the terms "comprising / including" or "containing / including" as used in this specification indicate the presence or addition of one or more components, steps, operations, and elements. Specific structural or functional descriptions of examples of embodiments of the concepts disclosed in this specification are merely illustrative to describe examples of embodiments of the concepts, and examples of embodiments of the concepts can be implemented in various forms, but these descriptions are not limited to the examples of embodiments described in this specification.

[0023] Based on the concept, various modifications and changes can be applied to examples of embodiments, such that examples of embodiments will be illustrated in the accompanying drawings and described in the specification. However, examples of embodiments based on the concept are not limited to specific embodiments, but include all changes, equivalents, or substitutions included within the spirit and scope of this disclosure.

[0024] It should be understood that when describing an element as "connected" or "linked" to another element, the element may be directly connected or linked to the other element, or it may be connected or linked to the other element via a third element. Conversely, it should be understood that when an element is described as "directly connected to" or "directly linked to" another element, no other element is placed between them. Other expressions describing relationships between components (i.e., "between" and "directly between" or "adjacent to" and "directly adjacent to") need to be interpreted in the same way.

[0025] The terminology used in this specification is for the purpose of describing specific examples of implementations only and is not intended to limit this disclosure. The singular form may include the plural form unless there is an explicit contrary meaning in the context. It should be understood in this specification that the terms "comprising" or "having" indicate the presence of the features, quantities, steps, operations, components, parts, or combinations thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, operations, components, parts, or combinations thereof.

[0026] Unless otherwise defined, all terms used herein (including technical or scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art. If a term is not clearly defined in a common dictionary in this specification, it shall be interpreted as having the same meaning as in the context of the relevant art, and not as an ideal or overly formal meaning.

[0027] Descriptions of known components and processing techniques may be omitted to avoid unnecessarily obscuring the embodiments of this disclosure.

[0028] Throughout this specification, the same reference numerals refer to the same elements. Therefore, even if a reference numeral is not mentioned or described with reference to one drawing, it may be mentioned or described with reference to another drawing. Furthermore, even if a reference numeral is not shown in one drawing, it may be mentioned or described with reference to another drawing.

[0029] Additionally, the logic level of a signal may be different from or opposite to the logic level described. For example, a signal described as having a logic "high" level may optionally have a logic "low" level, and a signal described as having a logic "low" level may optionally have a logic "high" level.

[0030] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this disclosure to facilitate a better understanding of the disclosure. However, the technical solutions claimed in this disclosure can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0031] Please see Figure 1 , Figure 1 This is a schematic diagram of the testing device structure for a high-value resistance testing method using a variable square wave excited dual feedback loop according to an embodiment of the present invention. The present invention provides a high-value resistance testing method using a variable square wave excited dual feedback loop, including a high-value resistance testing device for a variable square wave excited dual feedback loop. The high-value resistance testing device for a variable square wave excited dual feedback loop includes: a voltage source; a voltage loop, the input terminal of which is connected to the voltage source; one end of the resistor under test is connected to the output terminal of the voltage loop through the equivalent resistance of a four-wire test cable, and the other end of the resistor under test is connected to the input terminal of a current loop through the equivalent resistance of a four-wire test cable; the input terminal of a differential amplifier module is connected to the output terminal of the current loop, and the output terminal of the differential amplifier module is connected to a sampling terminal module; the high-value resistance testing method using a variable square wave excited dual feedback loop includes: S1. A constant DC voltage with alternating positive and negative values ​​is generated by a voltage source; S2, constant DC voltage connection to voltage loop; S3. The output of the voltage loop is connected to the resistor under test via a test cable; S4. The test cable is connected to the current loop; S5. The current loop output is connected to the differential amplifier module; S6. The output of the differential amplifier module is connected to the sampling terminal module.

[0032] Specifically, the voltage loop includes: a voltage follower circuit, a voltage proportional adjustment circuit, an integrator circuit, and a non-inverting proportional operational circuit. The voltage follower circuit includes an operational amplifier U1; the voltage proportional adjustment circuit includes resistors Rs1 and Rs2; the integrator circuit includes an operational amplifier U2, resistors R1, R2, R3, and capacitor C1; and the non-inverting proportional operational circuit includes an operational amplifier U3, resistors R4 and R5. One end of resistor Rs1 is connected to the voltage source, and the other end of resistor Rs1 is connected to one end of resistor Rs2, the inverting input of operational amplifier U2, and one end of resistor R1. The other end of Rs2 is connected to the output and inverting input of operational amplifier U1. The non-inverting input of operational amplifier U1 is connected to the equivalent resistance of the four-wire test cable. The other end of resistor R1 is connected to one end of capacitor C1. The other end of capacitor C1 is connected to the output of operational amplifier U2 and one end of resistor R2. The other end of resistor R2 is connected to one end of resistor R3 and the non-inverting input of operational amplifier U3. The output of operational amplifier U3 is connected to the equivalent resistance of the four-wire test cable and one end of resistor R4. The other end of resistor R4 is connected to one end of resistor R5 and the inverting input of operational amplifier U3. The other end of resistor R5 is grounded.

[0033] Specifically, one end of the resistor under test Rx is connected to one end of the equivalent resistance Rw1 and one end of the equivalent resistance Rw3 of the four-wire test cable. The other end of the equivalent resistance Rw1 is connected to the non-inverting input of the operational amplifier U1. The other end of the equivalent resistance Rw3 is connected to the output of the operational amplifier U3. The other end of the resistor under test Rx is connected to the equivalent resistance Rw2 and Rw4 of the four-wire test cable. The other ends of the equivalent resistance Rw2 and Rw4 are connected to the current loop.

[0034] Specifically, the current loop includes a voltage follower circuit, a sampling resistor, and an integrator circuit. The voltage follower circuit includes an operational amplifier U4, and the sampling resistor is Rb. The integrator circuit includes an operational amplifier U5 and a capacitor C2. The other end of the equivalent resistance Rw2 of the four-wire test cable is connected to the non-inverting input of the operational amplifier U4 and one end of the sampling resistor Rb. The other end of the equivalent resistance Rw4 of the four-wire test cable is connected to the inverting input of the operational amplifier U5 and one end of the capacitor C2. The inverting input of the operational amplifier U4 is connected to the output and then to the differential amplifier module. The other end of the sampling resistor Rb is connected to the output of the operational amplifier U5, the other end of the capacitor C2, and the differential amplifier module.

[0035] Specifically, the differential amplifier module includes an operational amplifier U6, resistors Rd1, Rd2, Rd3, and Rd4. One end of resistor Rd1 is connected to the output terminal of operational amplifier U4, and the other end of resistor Rd1 is connected to one end of resistor Rd2 and the non-inverting input terminal of operational amplifier U6. The other end of resistor Rd2 is grounded. One end of resistor Rd3 is connected to the output terminal of operational amplifier U5, and the other end of resistor Rd3 is connected to the inverting input terminal of operational amplifier U6 and one end of resistor Rd4. The other end of resistor Rd4 is connected to the output terminal of operational amplifier U6.

[0036] Specifically, the sampling module includes a filtering circuit and an analog voltage signal acquisition module, the latter comprising an ADC module. Resistor R1 and capacitor C1 of operational amplifier U2 provide phase compensation for operational amplifier U2. The sampling resistor Rb provides a feedback path for the current loop.

[0037] Specifically, the gain calculation formula for the differential amplifier composed of operational amplifier U6 and resistors Rd1, Rd2, Rd3, and Rd4 is as follows: .

[0038] In one embodiment of the present invention, a method for testing high-value resistance using a variable square wave excitation dual feedback loop is described in the following detail: (1) A constant DC voltage Vpulse with alternating positive and negative values ​​is generated by a DAC voltage source. The specific frequency, duty cycle, and voltage value can be adjusted according to actual test requirements, such as generating a square wave of 1kHz and ±10V. Under the drive of the alternating positive and negative square wave voltage source, the entire circuit generates bidirectional current excitation through the current loop to sample high-value resistors. Its core advantage is that it significantly suppresses low-frequency noise and DC drift, thereby improving the accuracy and stability of the measurement. The following is a detailed analysis: 1) Eliminate DC bias error and drift: Under pure DC excitation, the amplifier's input offset voltage, temperature drift, and time drift will be superimposed on the measurement signal, forming a fixed error. However, bidirectional current alternating excitation modulates the resistance signal into an AC signal, and the pure resistance signal is separated by the sampling end synchronous demodulation technology, thus canceling the amplifier's DC error.

[0039] 2) Suppress 1 / f low-frequency noise: The 1 / f noise of electronic devices is concentrated in the low-frequency range (<100Hz), which seriously affects the accuracy of DC measurement. Positive and negative excitation will shift the effective signal spectrum to the vicinity of the excitation frequency (such as 1kHz), avoid the low-frequency region dominated by 1 / f noise, and then suppress the noise significantly through bandpass filtering.

[0040] 3) Reduce thermoelectric effect error: The Joule heat generated when current flows through the resistor will form a thermoelectric potential, which appears as a slowly drifting spurious voltage in DC measurement. Positive and negative current excitation makes the thermoelectric potential appear symmetrically in the positive and negative cycles, and its influence can be canceled by differential calculation.

[0041] 4) Resistance to power supply and ground interference: DC measurement is susceptible to common-mode interference such as power supply ripple and ground fluctuation. AC excitation combined with differential amplification and synchronous detection can suppress interference that is not related to the excitation frequency (such as 50Hz power frequency noise).

[0042] (2) The square wave excitation voltage Vpulse is connected to the voltage loop. The following is a detailed analysis: 1) The feedback resistor R1 and integrating capacitor C1 of the integrating operational amplifier U2 provide phase compensation for U2: In the voltage feedback loop, when the loop gain lags by more than -180° at the cutoff frequency, a lead compensation network needs to be added. This network compensates for the phase lag of U2 through R1 and C1 at the cutoff frequency. Add a zero-point adjustment phase margin to prevent voltage loop oscillation.

[0043] Resistors R2 and R3 form a voltage divider circuit, making .

[0044] 2) The non-inverting proportional operational circuit consists of operational amplifier U3, resistors R4 and R5, making... The output of U3 is the high-side excitation output "HForce" of the test circuit, which is connected to the high-side induction output "HSense" via a test cable. This is the positive input terminal of the operational amplifier U1 in the voltage follower circuit, enabling... It provides a feedback path for the voltage loop.

[0045] 3) In the integrating circuit, the positive input terminal of operational amplifier U2 is connected to "ground" and has a voltage of 0V. Since the voltage at the positive input terminal of U2 is equal to the voltage at the negative input terminal, the voltage at V1 in the diagram is 0V. According to the node voltage formula: We can obtain: .

[0046] 4) Due to the effect of the voltage follower operational amplifier circuit U1, it makes... Since U1 is virtually open, the current at the positive input terminal of U1 is 0. This means that all the current generated by the "HForce" terminal flows into the resistor being measured, Rx, causing... .

[0047] (3) The output of the voltage loop is connected to the resistor under test via a test cable. The following is a detailed analysis: 1) The equivalent resistance value of the high-side excitation output "HForce" of the test cable is Rw3; the equivalent resistance value of the high-side induction output "HSense" of the test cable is Rw1; the equivalent resistance value of the low-side excitation output "LForce" of the test cable is Rw2; and the equivalent resistance value of the low-side induction output "LSense" of the test cable is Rw4. The voltage across the resistor Rx being measured is Vx+ and Vx-.

[0048] 3) The four-wire measurement method eliminates the influence of lead resistance, separating excitation and detection: the measured resistor Rx is connected in series with the sampling resistor Rb, and the excitation current Is is provided by the voltage loop. Voltage detection is sampled by the current loop, avoiding the influence of lead resistance.

[0049] (4) The test cable is connected to the current loop. The following is a detailed analysis: 1) In the integrating circuit, the positive input terminal of operational amplifier U5 is connected to ground (0V). Since the voltage at the positive and negative input terminals of U5 is equal, the voltage at V8 in the diagram is 0V. When the integration of U5 stabilizes, the current flowing through the "LSense" terminal is 0. .

[0050] 2) The voltage follower circuit is enabled by operational amplifier U4. .

[0051] 3) The sampling resistor provides a feedback path for the current loop; the test current is generated by resistor Rx. After flowing through the equivalent resistance value Rw2 of "LForce", it flows into the sampling resistor Rb, and the current across resistor Rb is... ,because ,so ,Right now .

[0052] (5) The current loop output is connected to the differential amplifier. The following is a detailed analysis: 1) Formula for calculating the gain of the differential amplifier composed of operational amplifier U6 and resistors Rd1, Rd2, Rd3, and Rd4: .

[0053] 2) The main advantages of differential amplifier circuits are: suppression of zero-point drift: it can effectively suppress output voltage drift caused by factors such as temperature changes and power supply fluctuations, and improve circuit stability; strong anti-common-mode interference capability: it has a strong suppression effect on common-mode signals (such as external interference), while it can amplify differential-mode signals (useful signals) normally.

[0054] (6) The differential amplifier output is connected to the sampling terminal Vsample. The following is a detailed analysis: The sampling end includes, but is not limited to, filtering circuits, signal amplification and processing circuits, and analog voltage signal acquisition. Analog voltage signal acquisition can be accomplished by an ADC or equivalent circuits.

[0055] In summary, the high-value resistance testing method of this invention, using a variable square wave excitation dual feedback loop, achieves high-precision weak current detection and stable voltage control through a precise dual feedback loop, and provides a foundation for efficient protection based on a four-wire structure, thereby enabling faster, more stable, and more accurate measurement of extremely high resistance values. Driven by an alternating positive and negative square wave voltage source, this invention generates bidirectional current excitation through a current loop to sample high-value resistors. Its core advantage lies in significantly suppressing low-frequency noise and DC drift, thereby improving measurement accuracy and stability.

[0056] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for testing high-value resistances using a variable square wave excitation dual feedback loop, characterized in that, A high-value resistance testing device including a variable square wave excitation dual feedback loop, the high-value resistance testing device including: Voltage source; and A voltage loop, the input of which is connected to the voltage source; The resistor under test has one end connected to the output terminal of the voltage loop via the equivalent resistance of a four-wire test cable, and the other end connected to the input terminal of the current loop via the equivalent resistance of a four-wire test cable. A differential amplifier module, the input of which is connected to the output of the current loop, and the output of the differential amplifier module is connected to the sampling module; The high-value resistance testing method for the variable square wave excited dual feedback loop includes: S1. A constant DC voltage with alternating positive and negative values ​​is generated by a voltage source; S2, constant DC voltage connection to voltage loop; S3. The output of the voltage loop is connected to the resistor under test via a test cable; S4. The test cable is connected to the current loop; S5. The current loop output is connected to the differential amplifier module; S6. The output of the differential amplifier module is connected to the sampling terminal module.

2. The method for testing high-value resistance using a variable square wave excitation dual feedback loop according to claim 1, characterized in that, The voltage loop includes: a voltage follower circuit, a voltage proportional adjustment circuit, an integrator circuit, and a non-inverting proportional operational circuit. The voltage follower circuit includes an operational amplifier U1; the voltage proportional adjustment circuit includes resistors Rs1 and Rs2; the integrator circuit includes an operational amplifier U2, resistors R1, R2, R3, and capacitor C1; and the non-inverting proportional operational circuit includes an operational amplifier U3, resistors R4 and R5. One end of resistor Rs1 is connected to the voltage source, and the other end of resistor Rs1 is connected to one end of resistor Rs2, the inverting input of operational amplifier U2, and one end of resistor R1. The other end of resistor R1 is connected to the output and inverting input of operational amplifier U1. The non-inverting input of operational amplifier U1 is connected to the equivalent resistance of the four-wire test cable. The other end of resistor R1 is connected to one end of capacitor C1. The other end of capacitor C1 is connected to the output of operational amplifier U2 and one end of resistor R2. The other end of resistor R2 is connected to one end of resistor R3 and the non-inverting input of operational amplifier U3. The output of operational amplifier U3 is connected to the equivalent resistance of the four-wire test cable and one end of resistor R4. The other end of resistor R4 is connected to one end of resistor R5 and the inverting input of operational amplifier U3. The other end of resistor R5 is grounded.

3. The method for testing high-value resistance using a variable square wave excitation dual feedback loop according to claim 2, characterized in that: One end of the resistor under test Rx is connected to one end of the equivalent resistance Rw1 and one end of the equivalent resistance Rw3 of the four-wire test cable. The other end of the equivalent resistance Rw1 is connected to the non-inverting input of the operational amplifier U1. The other end of the equivalent resistance Rw3 is connected to the output of the operational amplifier U3. The other end of the resistor under test Rx is connected to the equivalent resistance Rw2 and Rw4 of the four-wire test cable. The other ends of the equivalent resistance Rw2 and Rw4 are connected to the current loop.

4. The method for testing high-value resistance using a variable square wave excitation dual feedback loop according to claim 3, characterized in that: The current loop includes a voltage follower circuit, a sampling resistor, and an integrator circuit. The voltage follower circuit includes an operational amplifier U4, and the sampling resistor is Rb. The integrator circuit includes an operational amplifier U5 and a capacitor C2. The other end of the equivalent resistance Rw2 of the four-wire test cable is connected to the non-inverting input of the operational amplifier U4 and one end of the sampling resistor Rb. The other end of the equivalent resistance Rw4 of the four-wire test cable is connected to the inverting input of the operational amplifier U5 and one end of the capacitor C2. The inverting input of the operational amplifier U4 is connected to its output and then to a differential amplifier module. The other end of the sampling resistor Rb is connected to the output of the operational amplifier U5, the other end of the capacitor C2, and the differential amplifier module.

5. The method for testing high-value resistance using a variable square wave excitation dual feedback loop according to claim 4, characterized in that: The differential amplifier module includes an operational amplifier U6, resistors Rd1, Rd2, Rd3, and Rd4. One end of resistor Rd1 is connected to the output of operational amplifier U4, and the other end of resistor Rd1 is connected to one end of resistor Rd2 and the non-inverting input of operational amplifier U6. The other end of resistor Rd2 is grounded. One end of resistor Rd3 is connected to the output of operational amplifier U5, and the other end of resistor Rd3 is connected to the inverting input of operational amplifier U6 and one end of resistor Rd4. The other end of resistor Rd4 is connected to the output of operational amplifier U6.

6. The method for testing high-value resistance using a variable square wave excitation dual feedback loop according to claim 5, characterized in that: The sampling module includes a filtering circuit and an analog voltage signal acquisition module, wherein the analog voltage signal acquisition module includes an ADC module.

7. The method for testing high-value resistance using a variable square wave excitation dual feedback loop according to claim 5, characterized in that: The resistor R1 and capacitor C1 of the operational amplifier U2 provide phase compensation for the operational amplifier U2.

8. The method for testing high-value resistance using a variable square wave excitation dual feedback loop according to claim 5, characterized in that: The sampling resistor Rb provides a feedback path for the current loop.

9. The method for testing high-value resistance using a variable square wave excitation dual feedback loop according to claim 5, characterized in that: The formula for calculating the gain of the differential amplifier composed of operational amplifier U6 and resistors Rd1, Rd2, Rd3, and Rd4 is as follows: .

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