Low-common-mode bipolar edge-control constant-current excitation low-value resistor testing method

Abstract

The invention relates to the technical field of electronic measurement, in particular to a low-common-mode bipolar edge-control constant-current excitation low-value resistance testing method. The low-common-mode bipolar edge-control constant-current excitation low-value resistor testing device comprises a bipolar edge-control voltage module, a constant-current control module, a low-common-mode excitation module, a tested resistor and a sampling end module, the method comprises the steps that S1, a DAC voltage source of a bipolar edge control voltage module provides a bipolar voltage source Vdac with an edge control function; s2, the output voltage Vref of the bipolar edge control voltage module is connected with a constant current control module; s3, the excitation output low end of the constant current control module is connected with a low common mode excitation module; s4, the excitation output low end and the excitation output high end of the low common mode excitation module are connected with the tested resistor through a test cable; and S5, the induction high end and the induction low end of the test cable are connected with a sampling end module. According to the invention, the edge control technology and the constant current excitation technology are combined, and low-common-mode and high-precision low-value resistance measurement is realized.

Description

Technical Field

[0001] This invention relates to the field of electronic measurement technology, and more specifically, to a method for testing low-value resistors using low common-mode bipolar edge-controlled constant current excitation. Background Technology

[0002] The Importance and Challenges of Low-Value Resistance Measurement: In power equipment, the contact resistance of busbars and circuit breaker contacts is typically in the milliohm or even microohm range. Its value directly affects the safe and stable operation of the equipment, and accurate measurement helps assess equipment performance and predict faults. In the field of new energy batteries, the equivalent series resistance inside the battery is crucial to its charge / discharge efficiency and lifespan; accurate measurement provides key data for battery research and development and quality control. However, low-value resistors, with their small resistance, are highly susceptible to interference from additional resistances such as lead resistance and contact resistance, leading to significant measurement errors. Furthermore, external electromagnetic interference and changes in ambient temperature can also significantly affect the measurement results, making accurate measurement extremely challenging.

[0003] Limitations of traditional measurement methods: Common methods such as the voltmeter-ammeter method calculate resistance by measuring the current flowing through the resistor and the voltage across it. While the principle is simple, for low-value resistors, the voltage drop across them is very small, making them highly susceptible to noise from the measuring instrument itself and external electromagnetic interference, thus making it difficult to guarantee measurement accuracy. Bridge methods improve measurement accuracy to some extent; for example, the Wheatstone bridge and Kelvin bridge can effectively eliminate the influence of lead resistance and contact resistance. However, during the measurement process, balancing the bridge is cumbersome, and the measurement speed is slow, making it difficult to meet the needs of rapid measurement. Furthermore, these traditional methods have limited ability to suppress common-mode interference. In complex electromagnetic environments, common-mode interference can be converted into differential-mode interference, severely affecting measurement accuracy.

[0004] Applications and limitations of constant current excitation technology: To improve measurement accuracy, constant current excitation technology is applied to the measurement of low-value resistors. By applying a constant current to the resistor under test, measuring the voltage across its terminals, and calculating the resistance using Ohm's law, the influence of power supply fluctuations on the measurement results can be reduced. However, traditional constant current excitation sources suffer from high common-mode voltage, which generates common-mode current in the measurement circuit, thus introducing measurement errors. Moreover, conventional unipolar constant current excitation methods cannot effectively eliminate the influence of nonlinear factors such as parasitic capacitance and inductance that may exist in the resistor under test, leading to deviations in the measurement results. This effect is particularly pronounced when measuring low-value resistors with high-frequency characteristics. Conventional bipolar constant current excitation methods change the polarity of the output current by switching the direction of the current flowing through the resistor under test using a relay. This results in electromagnetic interference and signal overshoot during the switching moment, affecting the test results.

[0005] The Development and Demand of Edge Control Technology: Edge control technology, also known as edge-triggered control technology, is gradually being applied in signal processing and measurement. By precisely controlling the rising and falling edges of the excitation signal, electromagnetic interference and signal overshoot generated during switching can be eliminated, enabling precise control of the measurement process and improving the response speed and resolution of the measurement system. However, the application of existing edge control technology in low-value resistance measurement is not yet mature, and a complete solution that can effectively suppress common-mode interference and overcome the challenges of low-value resistance measurement has not yet been formed. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the objective of this invention is to propose a low common-mode bipolar edge-controlled constant current excitation method for testing low-value resistances, combining edge-controlled technology with constant current excitation technology to achieve low common-mode, high-precision measurement of low-value resistances.

[0007] To achieve the above and other related objectives, the present invention provides a method for testing low-value resistors using low-common-mode bipolar edge-controlled constant current excitation, comprising a low-common-mode bipolar edge-controlled constant current excitation low-value resistor testing device, wherein the low-common-mode bipolar edge-controlled constant current excitation low-value resistor testing device includes: A bipolar edge-controlled voltage module, the output of which is connected to the input of a constant current control module; The constant current control module has its output connected to the input of the low common-mode excitation module; Low common-mode excitation module, which connects to the resistor under test and the sampling module; The method for testing low-value resistance under low common-mode bipolar edge-controlled constant current excitation includes: S1. The DAC voltage source of the bipolar edge-controlled voltage module provides a bipolar voltage source Vdac with edge-controlled function; S2. The output voltage Vref of the bipolar edge-controlled voltage module is connected to the constant current control module; S3. The low end of the excitation output of the constant current control module is connected to the low common mode excitation module; S4. The low-end and high-end excitation outputs of the low common-mode excitation module are connected to the resistor under test via a test cable. S5. The high-sensing end and the low-sensing end of the test cable are connected to the sampling end module.

[0008] In one embodiment of the present invention, the bipolar edge-controlled voltage module includes: a voltage source VP and a voltage follower circuit U1, wherein the voltage source VP is connected to the non-inverting input terminal of the voltage follower circuit U1, and the output terminal of the voltage follower circuit U1 is connected to the inverting input terminal of the voltage follower circuit U1 and a constant current control module.

[0009] In one embodiment of the present invention, the constant current control module includes: a differential amplifier circuit, a power amplifier output circuit, a voltage follower circuit, and a standard resistor Rm. The differential amplifier circuit includes an operational amplifier U2 and a resistor R1. The non-inverting input terminal of the operational amplifier U2 is connected to the output terminal of the voltage follower circuit U1, and the output terminal of the operational amplifier U2 is connected to one end of the resistor R1. The power amplifier output circuit includes a power amplifier U3, resistors R2 and R3, and a capacitor Cb1. The other end of the resistor R1 is connected to the non-inverting input terminal of the power amplifier U3, and the inverting input terminals of the power amplifier U3 are respectively connected to one end of the resistor R2. The other end of resistor R2 is connected to one end of capacitor Cb1 and the output terminal of power amplifier U3. The other end of capacitor Cb1 is connected to the comp pin of power amplifier U3. The output terminal of power amplifier U3 is connected to one end of resistor R3. The voltage follower circuit includes operational amplifier U4 and resistor R4. The other end of resistor R3 is connected to one end of standard resistor Rm and the Sense pin of operational amplifier U2. The other end of standard resistor Rm is connected to one end of resistor R4. The other end of resistor R4 is connected to the non-inverting input terminal of operational amplifier U4. The output terminal of operational amplifier U4 is connected to the Ref pin of operational amplifier U2.

[0010] In one embodiment of the present invention, the low common-mode excitation module integrator circuit and the power amplifier output circuit include an operational amplifier U5, resistors R5 and R6, and a capacitor C1. The inverting input terminal of the operational amplifier U5 is connected to one end of resistor R5 and one end of capacitor C1. The other end of capacitor C1 is connected to the output terminal of the operational amplifier U5 and one end of resistor R6. The power amplifier output circuit includes a power amplifier U6, resistors R7 and R8, and a capacitor Cb2. The other end of resistor R6 is connected to the non-inverting input terminal of the power amplifier U6. The inverting input terminal of the power amplifier U6 is connected to one end of resistor R7. The other end of resistor R7 is connected to one end of capacitor Cb2, one end of resistor R8, and the output terminal of the power amplifier U6. The other end of capacitor Cb2 is connected to the Comp pin of the power amplifier U6.

[0011] In one embodiment of the present invention, the low common-mode bipolar edge-controlled constant current excitation low-value resistance testing device further includes: the other end of the resistor R8 outputs an excitation high-end and is connected to one end of the equivalent resistance Rw3 of the four-wire test cable; the other end of the resistor R5 outputs an excitation low-end and is connected to one end of the equivalent resistance Rw1 of the four-wire test cable; the other ends of the equivalent resistance Rw3 and the four-wire test cable Rw1 are respectively connected to the two ends of the resistor under test RX; the two ends of the resistor under test RX are also respectively connected to one end of the equivalent resistance Rw2 and the four-wire test cable Rw4; the other ends of the equivalent resistance Rw2 and the four-wire test cable Rw4 respectively output an induction high-end and an induction low-end, and are connected to the sampling module.

[0012] In one embodiment of the present invention, the sampling end module includes a filtering circuit and an analog voltage signal acquisition unit, wherein the analog voltage signal acquisition unit includes an ADC unit.

[0013] In one embodiment of the present invention, the bipolar edge-controlled voltage module output voltage Vref connected to the constant current control module in step S2 includes: S21. Voltage Vref enters operational amplifier U2, closing the loop of operational amplifier U2. Operational amplifier U2 integrates feedback loop resistors with equal resistance and consistent parameters. ; The gain of the negative feedback loop of operational amplifier U2 is ,get: V3 is the voltage of the Sense pin of operational amplifier U2; The gain of the positive feedback loop of operational amplifier U2 is ,get: ; Due to the virtual short of op-amp U2, it can be known that ,Right now Where V5 is the voltage of the Ref pin of operational amplifier U2; S22. The power amplifier output circuit provides the measurement excitation current. Power amplifier U3 uses a voltage follower. The input and output voltage formulas are... ; S23, the input and output voltage formulas of the voltage follower circuit U1 ; S24. Current flowing through the standard resistor Rm for From the above formula, we can obtain: .

[0014] In one embodiment of the present invention, the standard resistor Rm is selected with an accuracy of one ten-thousandth and a temperature stability within 5PPM.

[0015] As described above, the low common-mode bipolar edge-controlled constant current excitation low-value resistance testing method of the present invention has the following beneficial effects: The present invention provides a low common-mode bipolar edge-controlled constant current excitation method for testing low-value resistors, which combines edge-controlled technology with constant current excitation technology to achieve low common-mode and high-precision low-value resistor measurement.

[0016] This invention discloses a low common-mode bipolar edge-controlled constant current excitation method for testing low-value resistors. The output voltage is continuously adjusted at a specific rate to the final required voltage value, making the rise and fall times controllable. By precisely controlling the rise and fall times of the excitation signal, electromagnetic interference and signal overshoot generated during switching can be eliminated, achieving precise control of the measurement process and improving the response speed and resolution of the measurement system. The output voltage is generated by a DAC, but can also be provided by other methods.

[0017] This invention discloses a low common-mode bipolar edge-controlled constant current excitation method for testing low-value resistors. The voltage follower circuit outputs a voltage Vref, which acts as a buffer and isolation, reducing the load effect on the voltage source and minimizing the current drawn from the voltage source by subsequent circuits. This prevents a significant drop in the signal source voltage due to subsequent circuit connections. It has strong load-carrying capacity, can provide a large current to the load, and maintains a stable output voltage that is not easily affected by load changes, ensuring the quality of the output voltage. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the bipolar edge-controlled voltage and constant current control module structure of a measurement device for a low common-mode bipolar edge-controlled constant current excitation low-value resistance testing method according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the low common-mode excitation, the resistor under test, and the sampling terminal module structure of a measurement device for a low common-mode bipolar edge-controlled constant current excitation low-value resistor testing method according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the differential amplifier structure of a measurement device for a low common-mode bipolar edge-controlled constant current excitation low-value resistance testing method 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 2 , Figure 3 , Figure 1 This is a schematic diagram of the bipolar edge-controlled voltage and constant current control module structure of a measurement device for a low common-mode bipolar edge-controlled constant current excitation low-value resistance testing method according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the low common-mode excitation, the resistor under test, and the sampling terminal module structure of a measurement device for a low common-mode bipolar edge-controlled constant current excitation low-value resistor testing method according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the differential amplifier operational amplifier structure of a measurement device for a low common-mode bipolar edge-controlled constant current excitation low-value resistor testing method according to an embodiment of the present invention. The present invention provides a low common-mode bipolar edge-controlled constant current excitation low-value resistor testing method, including a low common-mode bipolar edge-controlled constant current excitation low-value resistor testing device. The low common-mode bipolar edge-controlled constant current excitation low-value resistor testing device includes: an output terminal of a bipolar edge-controlled voltage module connected to an input terminal of a constant current control module; an output terminal of the constant current control module connected to an input terminal of a low common-mode excitation module; and a low common-mode excitation module connected to the resistor under test and a sampling terminal module. The low common-mode bipolar edge-controlled constant current excitation low-value resistor testing method includes: S1. The DAC voltage source of the bipolar edge-controlled voltage module provides a bipolar voltage source Vdac with edge-controlled function; S2. The output voltage Vref of the bipolar edge-controlled voltage module is connected to the constant current control module; S3. The low end of the excitation output of the constant current control module is connected to the low common mode excitation module; S4. The low-end and high-end excitation outputs of the low common-mode excitation module are connected to the resistor under test via a test cable. S5. The high-sensing end and the low-sensing end of the test cable are connected to the sampling end module.

[0032] Specifically, the bipolar edge-controlled voltage module includes a voltage source VP and a voltage follower circuit U1. The voltage source VP is connected to the non-inverting input terminal of the voltage follower circuit U1, and the output terminal of the voltage follower circuit U1 is connected to the inverting input terminal of the voltage follower circuit U1 and the constant current control module.

[0033] Specifically, the constant current control module includes: a differential amplifier circuit, a power amplifier output circuit, a voltage follower circuit, and a standard resistor Rm. The differential amplifier circuit includes an operational amplifier U2 and a resistor R1. The non-inverting input of the operational amplifier U2 is connected to the output of the voltage follower circuit U1, and the output of the operational amplifier U2 is connected to one end of the resistor R1. The power amplifier output circuit includes a power amplifier U3, resistors R2 and R3, and a capacitor Cb1. The other end of the resistor R1 is connected to the non-inverting input of the power amplifier U3, and the inverting inputs of the power amplifier U3 are each connected to one end of the resistor R2. The other end is connected to one end of capacitor Cb1 and the output terminal of power amplifier U3. The other end of capacitor Cb1 is connected to the comp pin of power amplifier U3. The output terminal of power amplifier U3 is connected to one end of resistor R3. The voltage follower circuit includes operational amplifier U4 and resistor R4. The other end of resistor R3 is connected to one end of standard resistor Rm and the Sense pin of operational amplifier U2. The other end of standard resistor Rm is connected to one end of resistor R4. The other end of resistor R4 is connected to the non-inverting input terminal of operational amplifier U4. The output terminal of operational amplifier U4 is connected to the Ref pin of operational amplifier U2.

[0034] Specifically, the low common-mode excitation module integrator circuit and power amplifier output circuit include an operational amplifier U5, resistors R5 and R6, and capacitor C1. The inverting input terminal of the operational amplifier U5 is connected to one end of resistor R5 and one end of capacitor C1. The other end of capacitor C1 is connected to the output terminal of the operational amplifier U5 and one end of resistor R6. The power amplifier output circuit includes a power amplifier U6, resistors R7 and R8, and capacitor Cb2. The other end of resistor R6 is connected to the non-inverting input terminal of the power amplifier U6. The inverting input terminal of the power amplifier U6 is connected to one end of resistor R7. The other end of resistor R7 is connected to one end of capacitor Cb2, one end of resistor R8, and the output terminal of the power amplifier U6. The other end of capacitor Cb2 is connected to the Comp pin of the power amplifier U6.

[0035] Specifically, the low common-mode bipolar edge-controlled constant current excitation low-value resistance testing device further includes: the other end of resistor R8 outputs an excitation high-end and is connected to one end of the equivalent resistance Rw3 of the four-wire test cable; the other end of resistor R5 outputs an excitation low-end and is connected to one end of the equivalent resistance Rw1 of the four-wire test cable; the other ends of the equivalent resistance Rw3 and the equivalent resistance Rw1 of the four-wire test cable are respectively connected to the two ends of the resistor under test RX; the two ends of the resistor under test RX are also respectively connected to one end of 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 of the four-wire test cable output a sensing high-end and a sensing low-end, respectively, and are connected to the sampling module.

[0036] Specifically, the sampling module includes a filtering circuit and an analog voltage signal acquisition unit, and the analog voltage signal acquisition unit includes an ADC unit.

[0037] In one embodiment of the invention, a bipolar voltage source Vdac with edge-controlled functionality is provided by a DAC voltage source. The following is a detailed analysis: 1) The output voltage is continuously adjusted to the final required voltage value at a specific rate, making the rise and fall times controllable. By precisely controlling the rise and fall times of the excitation signal, electromagnetic interference and signal overshoot generated during switching can be eliminated, achieving precise control of the measurement process and improving the response speed and resolution of the measurement system. The output voltage is generated by a DAC, but can also be provided by other means.

[0038] 2) The voltage follower circuit's output voltage Vref acts as a buffer and isolation, reducing the load effect on the voltage source and minimizing the current drawn from the voltage source by subsequent circuits. This prevents a significant drop in the signal source voltage due to subsequent circuit connections. It has strong load-carrying capacity, can provide a large current to the load, and its output voltage is stable and not easily affected by load changes, ensuring output voltage quality. With a voltage amplification factor close to 1, the output voltage is almost equal to the input voltage, enabling signal following transmission and ensuring that the voltage amplitude remains essentially constant during signal transmission.

[0039] In one embodiment of the present invention, the voltage follower circuit output voltage Vref is connected to a constant current control circuit. The following is a detailed analysis: 1) When voltage Vref enters the differential operational amplifier U2, it closes the loop of the differential operational amplifier. This creates two identical feedback loops at the positive and negative input terminals of the op-amp. If these two loops are mismatched, it will introduce significant second harmonic distortion. U2 is a high-precision unity-gain differential operational amplifier, which integrates feedback loop resistors with equal resistance and consistent parameters. .

[0040] The gain of the negative feedback loop of op-amp U2 is ,get: .

[0041] The gain of the positive feedback loop of op-amp U2 is ,get: .

[0042] Because of the "virtual short" of op-amp U2, it is known that ,Right now .

[0043] 2) The power amplifier output circuit provides the excitation current for measurement and consists of power amplifier U3, resistors R2 and R3, and capacitor Cb1. Power amplifier U3 uses a voltage follower configuration. The input and output voltage formulas are as follows: Resistor R2 is an overvoltage protection circuit. When the voltage across resistor R2 is too high, the current flowing through R2 will be too high, leading to excessive output current in power amplifier U3 and a risk of damage. Capacitor Cb1 is a phase compensation capacitor, increasing the phase margin of the entire feedback loop and preventing self-oscillation. Resistor R3 is a power resistor used to protect the output power of power amplifier U3 from overload.

[0044] 3) The voltage follower circuit consists of operational amplifier U4 and resistor R4, i.e. .

[0045] 4) Current flowing through the standard resistor Rm for From the above formula, we can obtain: Select a standard resistor Rm with an accuracy of 0.01% and a temperature stability within 5 PPM, and use high-precision... The reference voltage generates an ultra-high precision constant current source, whose output is the low-end excitation output "SourceL" of the test circuit.

[0046] In one embodiment of the invention, the low-end "SourceL" of the excitation output is connected to a low common-mode excitation circuit. The following is a detailed analysis: 1) The integrating circuit consists of operational amplifier U5, resistors R5 and R6, and capacitor C1. The positive input terminal of operational amplifier U5 in the integrating circuit is connected to "ground" and is 0V. Due to the "virtual short" of U5, the voltage at the positive input terminal is equal to the voltage at the negative input terminal, i.e., V6=0V. Due to the "virtual open" of U5, the current flowing through resistor R5 is 0A. Therefore, Vsourcel=V6=0V, that is, the voltage at the low end of the excitation output "SourceL" is 0V, which provides a low common-mode voltage for the entire test circuit and ensures the test accuracy.

[0047] 2) The power amplifier output circuit provides the measurement excitation current and consists of power amplifier U6, resistors R6 and R7, and capacitor Cb2. Since the test excitation current is bipolar, this circuit and the power amplifier output circuit in the constant current excitation circuit work alternately. For example, U6 generates current sourcing, while U3 sinks current. Its function is completely consistent with the power amplifier output circuit in the constant current excitation circuit. The output of the power amplifier output circuit is the high-side excitation output "SourceH" of the test circuit.

[0048] In one embodiment of the present invention, the low-end excitation output "SourceL" and the high-end excitation output "SourceH" are connected to the resistor under test via a test cable. The following is a detailed analysis: 1) The equivalent resistance of the high-side excitation output "SourceH" of the test cable is Rw3; the equivalent resistance of the high-side induction output "MeasureH" of the test cable is Rw4; the equivalent resistance of the low-side excitation output "SourceL" of the test cable is Rw1; the equivalent resistance of the low-side induction output "MeasureL" of the test cable is Rw2. The voltage across the resistor Rx being measured is Vx+ and Vx-.

[0049] 2) The four-wire measurement method can eliminate the influence of lead resistance and separate excitation and detection.

[0050] In one embodiment of the invention, the high-sensing terminal "SourceH" and the low-sensing terminal "SourceL" of the test cable are connected to the sampling terminal. 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.

[0051] In summary, the low common-mode bipolar edge-controlled constant current excitation method for testing low-value resistors of this invention combines edge-controlled technology with constant current excitation technology to achieve low common-mode, high-precision measurement of low-value resistors. This method continuously adjusts the output voltage to the final required voltage value at a specific rate, making the rise and fall times controllable. By precisely controlling the rise and fall times of the excitation signal, electromagnetic interference and signal overshoot generated during switching can be eliminated, achieving precise control of the measurement process and improving the response speed and resolution of the measurement system. The output voltage is generated by a DAC, but can also be provided by other methods.

[0052] 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 low-value resistance using low common-mode bipolar edge-controlled constant current excitation, characterized in that, This includes a low common-mode bipolar edge-controlled constant current excitation low-value resistance testing device, wherein the low common-mode bipolar edge-controlled constant current excitation low-value resistance testing device comprises: A bipolar edge-controlled voltage module, the output of which is connected to the input of a constant current control module; The constant current control module has its output connected to the input of the low common-mode excitation module; Low common-mode excitation module, which connects to the resistor under test and the sampling module; The method for testing low-value resistance under low common-mode bipolar edge-controlled constant current excitation includes: S1. The DAC voltage source of the bipolar edge-controlled voltage module provides a bipolar voltage source Vdac with edge-controlled function; S2. The output voltage Vref of the bipolar edge-controlled voltage module is connected to the constant current control module; S3. The low end of the excitation output of the constant current control module is connected to the low common mode excitation module; S4. The low-end and high-end excitation outputs of the low common-mode excitation module are connected to the resistor under test via a test cable. S5. The high-sensing end and the low-sensing end of the test cable are connected to the sampling end module.

2. The method for testing low-value resistance using low common-mode bipolar edge-controlled constant current excitation according to claim 1, characterized in that, The bipolar edge-controlled voltage module includes a voltage source VP and a voltage follower circuit U1. The voltage source VP is connected to the non-inverting input terminal of the voltage follower circuit U1, and the output terminal of the voltage follower circuit U1 is connected to the inverting input terminal of the voltage follower circuit U1 and a constant current control module.

3. The method for testing low-value resistance using low common-mode bipolar edge-controlled constant current excitation according to claim 2, characterized in that, The constant current control module includes: a differential amplifier circuit, a power amplifier output circuit, a voltage follower circuit, and a standard resistor Rm. The differential amplifier circuit includes an operational amplifier U2 and a resistor R1. The non-inverting input of the operational amplifier U2 is connected to the output of the voltage follower circuit U1, and the output of the operational amplifier U2 is connected to one end of the resistor R1. The power amplifier output circuit includes a power amplifier U3, resistors R2 and R3, and a capacitor Cb1. The other end of the resistor R1 is connected to the non-inverting input of the power amplifier U3, and the inverting input of the power amplifier U3 is connected to one end of the resistor R2. The other end of the resistor R2... One end of the capacitor Cb1 is connected to one end of the power amplifier U3, and the other end of the capacitor Cb1 is connected to the comp pin of the power amplifier U3. The output of the power amplifier U3 is connected to one end of the resistor R3. The voltage follower circuit includes an operational amplifier U4 and a resistor R4. The other end of the resistor R3 is connected to one end of a standard resistor Rm and the Sense pin of the operational amplifier U2. The other end of the standard resistor Rm is connected to one end of the resistor R4. The other end of the resistor R4 is connected to the non-inverting input of the operational amplifier U4. The output of the operational amplifier U4 is connected to the Ref pin of the operational amplifier U2.

4. The method for testing low-value resistance using low common-mode bipolar edge-controlled constant current excitation according to claim 3, characterized in that, The low common-mode excitation module includes an integrating circuit and a power amplifier output circuit. The integrating circuit includes an operational amplifier U5, resistors R5 and R6, and a capacitor C1. The inverting input of the operational amplifier U5 is connected to one end of resistor R5 and one end of capacitor C1. The other end of capacitor C1 is connected to the output of the operational amplifier U5 and one end of resistor R6. The power amplifier output circuit includes a power amplifier U6, resistors R7 and R8, and a capacitor Cb2. The other end of resistor R6 is connected to the non-inverting input of the power amplifier U6. The inverting input of the power amplifier U6 is connected to one end of resistor R7. The other end of resistor R7 is connected to one end of capacitor Cb2, one end of resistor R8, and the output of the power amplifier U6. The other end of capacitor Cb2 is connected to the Comp pin of the power amplifier U6.

5. The method for testing low-value resistance using low common-mode bipolar edge-controlled constant current excitation according to claim 4, characterized in that, The low common-mode bipolar edge-controlled constant current excitation low-value resistance testing device further includes: the other end of resistor R8 outputs an excitation high-end and is connected to one end of the equivalent resistance Rw3 of the four-wire test cable; the other end of resistor R5 outputs an excitation low-end and is connected to one end of the equivalent resistance Rw1 of the four-wire test cable; the other ends of the equivalent resistance Rw3 and the equivalent resistance Rw1 of the four-wire test cable are respectively connected to the two ends of the resistor under test RX; the two ends of the resistor under test RX are also respectively connected to one end of 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 of the four-wire test cable output a sensing high-end and a sensing low-end, respectively, and are connected to the sampling module.

6. The method for testing low-value resistance using low common-mode bipolar edge-controlled constant current excitation according to claim 1, characterized in that: The sampling module includes a filtering circuit and an analog voltage signal acquisition unit, wherein the analog voltage signal acquisition unit includes an ADC unit.

7. The method for testing low-value resistance using low common-mode bipolar edge-controlled constant current excitation according to claim 6, characterized in that: The bipolar edge-controlled voltage module output voltage Vref in step S2 is connected to the constant current control module, including: S21. Voltage Vref enters operational amplifier U2, closing the loop of operational amplifier U2. Operational amplifier U2 integrates feedback loop resistors with equal resistance and consistent parameters. ; The gain of the negative feedback loop of operational amplifier U2 is ,get: V3 is the voltage of the Sense pin of operational amplifier U2; The gain of the positive feedback loop of operational amplifier U2 is ,get: ; Due to the virtual short of op-amp U2, it can be known that ,Right now Where V5 is the voltage of the Ref pin of operational amplifier U2; S22. The power amplifier output circuit provides the measurement excitation current. Power amplifier U3 uses a voltage follower. The input and output voltage formulas are... ; S23, the input and output voltage formulas of the voltage follower circuit U1 ; S24. Current flowing through the standard resistor Rm for From the above formula, we can obtain: .

8. The method for testing low-value resistance using low common-mode bipolar edge-controlled constant current excitation according to claim 7, characterized in that: The standard resistor Rm is selected with an accuracy of one ten-thousandth and a temperature stability within 5PPM.

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