An anti-interference resistance detection circuit board and detection system based on four-wire measurement

Abstract

This invention discloses an anti-interference resistance detection circuit board and system based on four-wire measurement, belonging to the field of industrial automation testing technology. Addressing the problems of low accuracy, weak anti-interference, and limited channel expansion in traditional two-wire measurement, this invention employs independently electrically isolated current and voltage sampling loops, eliminating wire resistance errors through Kelvin connections; it integrates EMI filters, optocouplers, and double-shielded cables to suppress electromagnetic interference and ground loop effects; a single circuit board supports at least two measurement units in parallel, and multiple boards can be cascaded using an EtherCAT bus, supporting a maximum of 384 channels. This invention achieves a measurement error ≤ ±0.1% and a single-channel detection time ≤ 10ms, meeting the requirements of high-density, high-cycle scenarios such as perovskite photovoltaic glass. It is suitable for resistance measurement in a wide range of 100MΩ to 100MΩ, exhibiting extremely low signal transmission error rate in strong industrial electromagnetic environments, significantly improving detection accuracy and system reliability.

Description

Technical Field

[0001] This invention relates to an anti-interference relay board and detection system based on four-wire measurement, specifically in the field of industrial automation testing equipment technology, and is particularly suitable for scenarios such as rapid batch detection of resistance in perovskite thin-film batteries. Background Technology

[0002] In the field of industrial automation testing, resistance measurement is a key step in the quality inspection of products such as electronic components and photovoltaic cells. Taking the production of perovskite photovoltaic glass as an example, about 200 cell units are integrated on a single piece of glass, and the production line cycle requires that the resistance of all cells on a single piece of glass be completed within 30 seconds. This places extremely high demands on the speed, accuracy and anti-interference capability of the battery testing system.

[0003] Traditional resistance testing equipment typically uses a relay board in a two-wire measurement method as a signal transfer device. Its working principle involves applying current to the object being measured through two wires and acquiring the voltage signal, then calculating the resistance value based on Ohm's law. However, the two-wire measurement method has the following drawbacks:

[0004] 1. Insufficient measurement accuracy: In two-wire measurement, the resistance of the wires will be included in the resistance value of the object being measured, resulting in measurement error, which is more significant in long-distance or small resistance measurements.

[0005] 2. Weak anti-interference capability: Industrial environments are rife with electromagnetic interference and signal crosstalk. Traditional relay boards do not have effective protection against power fluctuations, control signal interference, and signal transmission interference, which can easily lead to abnormal measurement data.

[0006] 3. In addition, traditional relay boards support a limited number of detection channels, typically ≤32, and do not support multi-board collaborative control, which cannot meet the batch testing needs of high-density detection scenarios such as perovskite photovoltaic glass.

[0007] Therefore, there is an urgent need for a relay board and detection system that can simultaneously improve measurement accuracy, anti-interference capability, and support flexible expansion, in order to solve the application bottleneck of existing technologies in high-density, high-frequency industrial detection scenarios. Summary of the Invention

[0008] To address the shortcomings of the prior art, the present invention aims to provide an anti-interference relay board and detection system based on four-wire measurement.

[0009] According to an embodiment of the present invention, the first solution is: an anti-interference resistance detection circuit board based on four-wire measurement, comprising at least two measurement units;

[0010] The measurement unit includes an independently electrically isolated current loop and a voltage sampling loop;

[0011] The current loop is connected to the constant current power supply module through a relay switch. The opening and closing of the relay switch is controlled by the central controller through a digital signal sent by the remote I / O interface. The output current of the constant current power supply module is configured by the central controller through a digital communication interface. The two wires Force+ and Force- of the current loop are connected to the two poles of the resistor under test through a jack and the excitation current is applied to the resistor under test.

[0012] The two wires Sense+ and Sense- of the voltage sampling circuit are connected to the two poles of the resistor under test through a horn plug and the voltage drop across the resistor under test by the excitation current is collected. The voltage drop signal is converted into a digital signal by a filter circuit, an amplifier circuit and an ADC analog-to-digital converter and then transmitted to the central controller.

[0013] The central controller configures the excitation current of the resistor under test and calculates the resistance value of the resistor under test after collecting the voltage drop.

[0014] Furthermore, the two wires Force+ and Force- of the current loop and the two wires Sense+ and Sense- of the voltage sampling loop are electrically isolated by Kelvin connection.

[0015] Furthermore, the constant current power supply module includes a power supply input terminal, an EMI filter, and a control board connected in sequence. The EMI filter is connected in series between the power supply input terminal and the control board to suppress electromagnetic interference from the external power grid. Ceramic capacitors or electrolytic capacitors are connected in parallel at the power supply pins of the power-consuming components of the control board to form a two-stage filter network to filter out electromagnetic interference inside the control board.

[0016] The EMI filter includes a common-mode inductor and a differential-mode capacitor. The inductance of the common-mode inductor is 1mH-10mH, and the capacitance of the differential-mode capacitor is 1000pF-0.1μF. The common-mode inductor and the differential-mode capacitor are connected in series to the power supply input terminal.

[0017] Furthermore, an optocoupler is connected in series between the relay switch and the remote I / O interface. The input end of the optocoupler is connected to the remote I / O interface and receives digital control signals. The output end of the optocoupler is connected to the control pin of the relay drive circuit, transmitting the isolated digital control signals to the relay switch to control the on / off state of the current loop. The input-output voltage gap of the optocoupler is not less than 2500V to achieve electrical isolation of the control signals and suppression of electromagnetic interference.

[0018] Furthermore, the relay driving circuit includes an NPN transistor amplifier module and a freewheeling diode. The collector of the NPN transistor amplifier module is connected in series with the relay coil, the emitter of the NPN transistor amplifier module is grounded, and the base of the NPN transistor amplifier module receives the output signal of the optocoupler through a 1kΩ resistor.

[0019] Furthermore, the digital signal line connecting the relay switch to the I / O interface uses a double-shielded coaxial cable. The coaxial cable is provided with a center conductor, an insulating layer, an inner aluminum foil shielding layer, a braided outer shielding layer, and an outer sheath from the inside out. The inner aluminum foil shielding layer and the outer braided outer shielding layer are grounded through multi-strand copper core wires. One end of the multi-strand copper core wire is connected to the grounding copper busbar of the circuit board, and the other end is connected to the system grounding grid. The grounding resistance is ≤2 ohms.

[0020] Furthermore, the at least two measurement units are connected in parallel to the output terminal of the constant current power supply module.

[0021] Furthermore, the constant current power supply module includes a resistor. The positive voltage test terminal, negative voltage test terminal, positive current output terminal, and negative current output terminal of the resistor are respectively connected to the common terminal of each measurement unit. Each measurement unit is connected in series with an optocoupler. The input terminal of the optocoupler is connected to a remote I / O interface and receives digital control signals. By controlling the on / off state of the optocoupler, the resistor can switch between multiple resistors under test for measurement.

[0022] The central controller uses a resistor meter to set a constant excitation current to collect the voltage drop across the resistor under test and then calculates the resistance value of the resistor under test.

[0023] Furthermore, it also includes an EtherCAT bus communication module. The central controller connects to at least two anti-interference resistor detection circuit boards through the EtherCAT bus communication module and realizes inter-board synchronous control with a synchronization period of ≤1ms, supporting a maximum of 384 measurement channels.

[0024] According to an embodiment of the present invention, utilizing the anti-interference resistance detection circuit board based on four-wire measurement in the first solution provided by the present invention, a second solution is provided as follows:

[0025] An anti-interference resistance detection system based on four-wire measurement includes any of the above-mentioned anti-interference resistance detection circuit boards based on four-wire measurement.

[0026] Compared with the prior art, the unique advantages of the technical solution provided in this application are as follows:

[0027] The system employs independently electrically isolated current and voltage sampling loops, using Kelvin connections to avoid the influence of wire resistance and contact resistance on the measurement results. Especially in low-resistance measurement scenarios, the error can be reduced to within ±0.1%, solving the problem of including wire resistance in the measured value in traditional two-wire measurements. The constant current power supply module enables current parameter configuration through the digital communication interface of the central controller, ensuring good output current stability. Combined with a 16-bit ADC analog-to-digital converter, it ensures high-precision conversion of the voltage sampling signal, further improving the accuracy of resistance calculation.

[0028] It adopts a multi-level electromagnetic interference suppression design and signal link isolation protection, which can effectively filter out high-frequency noise inside the circuit board, while ensuring stable signal transmission in industrial strong electromagnetic environments.

[0029] A single circuit board supports multiple measurement units connected in parallel, and the channel switching is independently controlled by an optocoupler. The measurement time of a single channel is less than 10ms, which meets the production line cycle requirements for perovskite photovoltaic glass to complete full board testing within a specified time (30S, etc.). Based on EtherCAT bus, the board-to-board synchronous control supports 8 circuit boards connected in parallel to form 384 measurement channels, which solves the bottleneck that traditional relay boards cannot meet the high-density testing scenarios, and the expansion process does not require recalibrating the system.

[0030] This invention can be directly applied to batch resistance testing of products such as photovoltaic cells and electronic components. It is especially suitable for scenarios with strong electromagnetic interference, high testing density, and strict accuracy requirements. At the same time, it supports adapting to a wide range of resistance measurement needs of 100MΩ~100MΩ by adjusting the constant current source parameters. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] in:

[0033] Figure 1 This is a frame diagram of an anti-interference resistance detection circuit board based on four-wire measurement in one embodiment. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Example 1

[0036] The technical problem addressed in this embodiment is that existing resistance testing equipment typically uses a relay board with a two-wire measurement method as a signal transfer device. Its working principle involves applying current to the object under test through two wires and acquiring the voltage signal, then calculating the resistance value according to Ohm's law. The two-wire measurement method has the following drawbacks: insufficient measurement accuracy (the resistance of the wires is included in the resistance value of the object under test, leading to measurement errors, especially significant in long-distance or low-resistance measurements); weak anti-interference capability (in industrial environments, there are numerous electromagnetic interference and signal crosstalk issues, and traditional relay boards lack effective protection against power fluctuations, control signal interference, and signal transmission interference, easily leading to abnormal measurement data); furthermore, traditional relay boards support a limited number of detection channels, typically ≤32, and do not support multi-board collaborative control, failing to meet the batch testing needs of high-density testing scenarios such as perovskite photovoltaic glass. Therefore, there is an urgent need for a relay board and testing system that can simultaneously improve measurement accuracy, anti-interference capability, and support flexible expansion to overcome the application bottlenecks of existing technologies in high-density, high-frequency industrial testing scenarios.

[0037] This embodiment specifically provides an anti-interference resistance detection circuit board based on four-wire measurement, including at least two measurement units;

[0038] The measurement unit includes an independently electrically isolated current loop and a voltage sampling loop;

[0039] The current loop is connected to the constant current power supply module through a relay switch. The opening and closing of the relay switch is controlled by the central controller through a digital signal sent by the remote I / O interface. The output current of the constant current power supply module is configured by the central controller through a digital communication interface. The two wires Force+ and Force- of the current loop are connected to the two poles of the resistor under test through a jack and the excitation current is applied to the resistor under test.

[0040] The two wires Sense+ and Sense- of the voltage sampling circuit are connected to the two poles of the resistor under test through a horn plug and the voltage drop across the resistor under test by the excitation current is collected. The voltage drop signal is converted into a digital signal by a filter circuit, an amplifier circuit and an ADC analog-to-digital converter and then transmitted to the central controller.

[0041] The central controller configures the excitation current of the resistor under test and calculates the resistance value of the resistor under test after collecting the voltage drop.

[0042] This embodiment provides an anti-interference resistance detection circuit board based on four-wire measurement, such as... Figure 1 As shown, the overall architecture includes multiple independent measurement units, a constant current power supply module, a central controller, and an EtherCAT bus communication module. Two independent measurement units are connected in parallel to the output of the constant current power supply module. The central controller configures the constant current power supply parameters through a digital communication interface and controls the on / off state of the measurement units through a remote I / O interface. At the same time, it realizes multi-board collaborative expansion through the EtherCAT bus.

[0043] Each measurement unit includes an independently electrically isolated current loop and a voltage sampling loop, which are physically separated by a Kelvin connection to avoid the influence of wire resistance and contact resistance on measurement accuracy.

[0044] The current loop of the measurement unit is controlled by a relay switch: the current loop is connected to the constant current power supply module via an electromagnetic relay. The on / off state of the relay switch is controlled by a digital signal sent by the central controller through a remote I / O interface. To achieve electrical isolation of the control signal, an optocoupler is connected in series between the relay switch and the remote I / O interface, with an input-output voltage gap ≥2500V, which can effectively suppress electromagnetic interference. The drive circuit of the measurement unit uses an NPN transistor amplifier module. The base of the transistor receives the output signal from the optocoupler through a 1kΩ current-limiting resistor. The collector is connected in series with the relay coil, and the emitter is grounded. A freewheeling diode is connected in parallel across the coil to prevent back electromotive force from damaging the component when the coil is de-energized. The wire connection method is as follows: the Force+ and Force- wires of the current loop are connected to the two poles of the resistor under test through a jack. The wires are silver-plated copper wires with a cross-sectional area of ​​0.5mm² to reduce the loop resistance.

[0045] The voltage sampling loop of the measurement unit connects the Sense+ and Sense- wires to the two terminals of the resistor under test via jacks, acquiring the voltage drop generated by the excitation current flowing through the resistor. The signal sequentially passes through a second-order RC filter circuit, an instrumentation amplifier, and a 16-bit ADC analog-to-digital converter. The converted digital signal is then transmitted to the central controller via the I²C bus. For interference suppression, a 10μF tantalum capacitor and a 0.1μF ceramic capacitor are connected in parallel at the reference voltage terminal of the ADC converter to form a decoupling network, suppressing the impact of power supply noise on sampling accuracy.

[0046] The constant current power supply module features an anti-interference design, employing a high-precision resistor meter with an output current range of 1μA-1A and a stability of ≤0.01% / h. To suppress mains interference, an EMI filter is connected in series at the module input. Specifically, this includes a common-mode inductor: a magnetic ring-type common-mode inductor with an inductance of 10mH and a rated current of 3A; and a differential-mode capacitor: an X7R ceramic capacitor connected in series with the common-mode inductor and connected to the power input. Furthermore, a 10μF electrolytic capacitor and a 0.1μF ceramic capacitor are connected in parallel at the power pins of the power-consuming components on the control board, forming a two-stage filter network to filter out high-frequency noise within the board.

[0047] Signal transmission and grounding treatment, shielded cable selection: The digital signal line between the relay switch and the I / O interface uses a double-shielded coaxial cable. Its structure, from the inside out, consists of: a center conductor, a polyethylene insulation layer, an aluminum foil inner shield, a tinned copper wire braided outer shield, and a PVC outer sheath. The inner and outer shields are grounded via multi-strand copper core wires, with a grounding resistance ≤2Ω. Grounding design: The circuit board is equipped with an independent grounding copper busbar, connected to the system grounding grid via a 6mm² copper post, achieving single-point grounding and avoiding ground loop interference.

[0048] To meet the demands of high-density testing, this embodiment supports multi-board collaborative operation. The central controller connects to eight testing circuit boards via an EtherCAT bus communication module, enabling synchronous control between boards with a synchronization cycle of ≤1ms. Each circuit board contains 32 measurement units, and the eight boards can be expanded to 256 measurement channels. The measurement time per channel is ≤10ms, meeting the production line cycle requirement of completing full-board testing of perovskite photovoltaic glass (200 cell units per board) within 30 seconds.

[0049] Workflow:

[0050] S1: Parameter configuration. The central controller sends instructions to the constant current power supply module through the digital communication interface (RS485 protocol) to configure the excitation current.

[0051] S2: Channel switching. The central controller sends a control signal through the remote I / O interface, which drives the relay switch after being isolated by the optocoupler, and selects the current loop of the target measurement unit.

[0052] S3: Signal acquisition. The voltage sampling circuit acquires the voltage drop across the resistor under test through Sense+ and Sense-, and transmits it to the central controller after filtering, amplification and ADC conversion.

[0053] S4: Resistance calculation. The central controller calculates the resistance value according to Ohm's law (R=U / I) and uploads the data to the host computer via the EtherCAT bus.

[0054] S5: Multi-board synchronization. Through the distributed clock synchronization function of the EtherCAT bus, parallel measurement of multiple circuit boards can be achieved, improving testing efficiency.

[0055] The system employs independently electrically isolated current and voltage sampling loops, using Kelvin connections to avoid the influence of wire and contact resistance on measurement results. Especially in low-resistance measurement scenarios, the error can be reduced to within ±0.1%, solving the problem of wire resistance being included in the measured value in traditional two-wire measurements. The constant current power supply module configures current parameters through the digital communication interface of the central controller, ensuring good output current stability. Combined with a 16-bit ADC analog-to-digital converter, it ensures high-precision conversion of the voltage sampling signal, further improving the accuracy of resistance calculation. Multi-level electromagnetic interference suppression design and signal link isolation protection effectively filter out high-frequency noise within the circuit board while ensuring stable signal transmission in strong industrial electromagnetic environments. A single circuit board supports… This invention supports multiple parallel measurement units and independent channel switching via optocouplers. The measurement time for a single channel is less than 10ms, meeting the production line cycle requirements for perovskite photovoltaic glass to complete full-board testing within a specified time (e.g., 30s). Based on EtherCAT bus-based inter-board synchronous control, it supports 8 circuit boards connected in parallel to form 384 measurement channels, solving the bottleneck of traditional relay boards being unable to meet high-density testing scenarios. Moreover, the expansion process does not require system recalibration. This invention can be directly applied to batch resistance testing of photovoltaic cells, electronic components, and other products, and is especially suitable for scenarios with strong electromagnetic interference, high testing density, and strict accuracy requirements. It also supports adapting to a wide range of resistance measurement needs from 100MΩ to 100MΩ by adjusting the constant current source parameters.

[0056] Example 2

[0057] This embodiment provides a specific anti-interference resistance detection circuit board based on four-wire measurement, including at least two measurement units. Each measurement unit includes an independently electrically isolated current loop and a voltage sampling loop. The current loop is connected to a constant current power supply module via a relay switch. The on / off state of the relay switch is controlled by a central controller sending a digital signal through a remote I / O interface. The output current of the constant current power supply module is configured by the central controller through a digital communication interface. The two wires Force+ and Force- of the current loop are connected to the two poles of the resistor under test via a jack and apply the excitation current to the resistor under test. The two wires Sense+ and Sense- of the voltage sampling loop are connected to the two poles of the resistor under test via a jack and collect the voltage drop across the resistor under test caused by the excitation current. The voltage drop signal is converted into a digital signal by a filter circuit, an amplifier circuit, and an ADC analog-to-digital converter before being transmitted to the central controller. The central controller configures the excitation current of the resistor under test and calculates the resistance value of the resistor under test after collecting the voltage drop.

[0058] Specifically, the two wires Force+ and Force- of the current loop and the two wires Sense+ and Sense- of the voltage sampling loop are electrically isolated by Kelvin connection.

[0059] Specifically, the constant current power supply module includes a power supply input terminal, an EMI filter, and a control board connected in sequence. The EMI filter is connected in series between the power supply input terminal and the control board to suppress electromagnetic interference from the external power grid. Ceramic capacitors or electrolytic capacitors are connected in parallel at the power supply pins of the power-consuming components of the control board to form a two-stage filter network to filter out electromagnetic interference inside the control board. The EMI filter includes a common-mode inductor and a differential-mode capacitor. The inductance value of the common-mode inductor is 1mH-10mH, and the capacitance value of the differential-mode capacitor is 1000pF-0.1μF. The common-mode inductor and the differential-mode capacitor are connected in series to the power supply input terminal.

[0060] Specifically, an optocoupler is connected in series between the relay switch and the remote I / O interface. The input end of the optocoupler is connected to the remote I / O interface and receives digital control signals. The output end of the optocoupler is connected to the control pin of the relay drive circuit, transmitting the isolated digital control signals to the relay switch to control the on / off state of the current loop. The input-output voltage gap of the optocoupler is not less than 2500V to achieve electrical isolation of the control signals and suppression of electromagnetic interference.

[0061] Specifically, the relay driving circuit includes an NPN transistor amplifier module and a freewheeling diode. The collector of the NPN transistor amplifier module is connected in series with the relay coil, the emitter of the NPN transistor amplifier module is grounded, and the base of the NPN transistor amplifier module receives the output signal of the optocoupler through a 1kΩ resistor.

[0062] Specifically, the digital signal line connecting the relay switch to the I / O interface uses a double-shielded coaxial cable. The coaxial cable has a center conductor, an insulating layer, an inner aluminum foil shielding layer, a braided outer shielding layer, and an outer sheath arranged sequentially from the inside to the outside. The inner aluminum foil shielding layer and the outer braided outer shielding layer are grounded through multi-strand copper core wires. One end of each multi-strand copper core wire is connected to the grounding copper busbar of the circuit board, and the other end is connected to the system grounding grid. The grounding resistance is ≤2 ohms.

[0063] Specifically, the constant current power supply module includes a resistor meter. The positive voltage test terminal, negative voltage test terminal, positive current output terminal, and negative current output terminal of the resistor meter are respectively connected to the common terminal of each measurement unit. Each measurement unit is connected in series with an optocoupler. The input terminal of the optocoupler is connected to a remote I / O interface and receives digital control signals. By controlling the on / off state of the optocoupler, the resistor meter is controlled to switch between multiple resistors under test for measurement. The central controller uses the resistor meter to configure a constant excitation current to collect the voltage drop across the resistor under test and then calculates the resistance value of the resistor under test.

[0064] Specifically, it also includes an EtherCAT bus communication module. The central controller connects to at least two anti-interference resistor detection circuit boards through the EtherCAT bus communication module and realizes inter-board synchronous control with a synchronization period of ≤1ms, supporting a maximum of 384 measurement channels.

[0065] This embodiment solves the problems of insufficient accuracy (error ≤ ±0.1%), weak anti-interference ability, and limited number of channels in traditional two-wire measurement by using four-wire measurement, independent electrical isolation, multi-level anti-interference design, and bus expansion technology. It can be directly applied to batch resistance testing of products such as perovskite thin-film batteries and electronic components, and is especially suitable for industrial scenarios with strong electromagnetic interference and high detection density.

[0066] Example 3

[0067] Based on the anti-interference resistance detection circuit board of Embodiment 2 using four-wire measurement, this embodiment is designed for the scenario of detecting the on-resistance of IGBT modules in new energy vehicle motor controllers, solving the problems of insufficient measurement accuracy and low detection efficiency in existing technologies under strong electromagnetic interference environments. As the core power device of the motor controller, the on-resistance of the IGBT module, typically ranging from 1mΩ to 100mΩ, directly affects heat dissipation performance and power loss, requiring rapid batch testing on the production line.

[0068] The detection circuit board in this embodiment includes eight independent measurement units, a wide-range constant current power supply module, a central controller, and a high-speed data transmission module. The eight measurement units are connected in parallel, supporting eight channels of parallel detection. The central controller communicates with the host computer via an EtherCAT bus. A single circuit board can cover all six on-resistance detection requirements of one IGBT module, with the remaining two channels reserved for redundancy.

[0069] The current and voltage sampling loops of each measurement unit use Kelvin four-terminal connections. Low-impedance silver-plated copper wire is used, and spring-loaded horn-type connectors are used to ensure a contact resistance of <5mΩ, minimizing the impact of contact resistance on milliohm-level measurements. The voltage sampling loop's filtering circuit is optimized to a third-order Butterworth low-pass filter, working in conjunction with a 24-bit ADC to ensure a measurement resolution of 0.01mΩ for a 1mΩ resistance.

[0070] The constant current power supply module adopts a dual-output design: one output is 100mA~1A, compatible with resistors from 1mΩ to 10mΩ, and the other outputs 10mA~100mA, automatically switching ranges via the digital communication interface of the central controller. An internal temperature compensation circuit is added: a negative temperature coefficient thermistor is connected in series between the EMI filter and the control board to monitor the ambient temperature in real time and feed it back to the central controller. Software algorithms correct current output deviations, with temperature drift ≤ ±5ppm / ℃.

[0071] To address high-frequency pulse interference in the motor controller production line, this embodiment adds a ferrite bead array to the signal link, connected in parallel between the output of the optocoupler and the relay drive circuit, to suppress high-frequency noise coupling. The control signal line of the relay switch uses a triple-shielded cable, with an inner shield of aluminum foil and a double-layer braided mesh. The grounding method is optimized to multi-point grounding (interval ≤30cm) to ensure that the impedance of the shielding layer is <1Ω in the high-frequency band.

[0072] The specific workflow is as follows:

[0073] S101: Automatic range switching: The central controller calls preset parameters according to the IGBT module model and automatically configures the constant current power supply output, such as outputting 1A current when detecting a 1mΩ resistance.

[0074] S102: It synchronously sends 8 control signals through the remote I / O interface, which drive the relay switches of 8 measurement units after being isolated by optocouplers, so as to realize the parallel conduction of 8 channels;

[0075] S103: A 24-bit ADC simultaneously acquires 8 voltage signals at a sampling rate of 30kSPS and transmits them to the central controller via DMA direct memory access technology. The single-channel data processing time is <2ms.

[0076] S104: The central controller calculates the on-resistance according to the formula R=U / I and uploads it to the host computer via EtherCAT bus with a communication rate of 100Mbps. The single detection cycle is ≤40ms, which meets the production line cycle requirements.

[0077] This embodiment achieves the following results on the IGBT module production line for new energy vehicles through multi-channel parallel detection, wide-range constant current output, and high-frequency interference suppression design: Measurement error of resistance from 1mΩ to 100mΩ is ≤±0.05% under 1MHz electromagnetic interference; a single circuit board supports 8-channel parallel detection, and the detection time for a single IGBT module (6 resistors) is ≤40ms, a 3-fold improvement over traditional equipment; the operating temperature range is -40℃ to 85℃, meeting the wide-temperature environment requirements of automotive electronics production lines, and eliminating the need for periodic calibration. This embodiment can be directly integrated into an automated testing platform for motor controllers, or expanded to 32 channels via EtherCAT bus, i.e., 4 circuit boards connected in parallel, to adapt to higher production capacity requirements.

[0078] Example 4

[0079] This embodiment provides an anti-interference resistance detection system based on four-wire measurement, including an anti-interference resistance detection circuit board based on four-wire measurement. The detection circuit board includes at least two measurement units. Each measurement unit includes an independently electrically isolated current loop and a voltage sampling loop. The current loop is connected to a constant current power supply module via a relay switch. The on / off state of the relay switch is controlled by a central controller sending a digital signal through a remote I / O interface. The output current of the constant current power supply module is configured by the central controller through a digital communication interface. The two wires Force+ and Force- of the current loop are connected to the two poles of the resistor under test via a jack and apply the excitation current to the resistor under test. The two wires Sense+ and Sense- of the voltage sampling loop are connected to the two poles of the resistor under test via a jack and collect the voltage drop across the resistor under test caused by the excitation current. The voltage drop signal is converted into a digital signal by a filter circuit, an amplifier circuit, and an ADC analog-to-digital converter before being transmitted to the central controller. The central controller configures the excitation current of the resistor under test and calculates the resistance value of the resistor under test after collecting the voltage drop.

[0080] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0081] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An anti-interference resistance detection circuit board based on four-wire measurement, characterized in that, Includes at least two measurement units; The measurement unit includes an independently electrically isolated current loop and a voltage sampling loop; The current loop is connected to the constant current power supply module through a relay switch. The opening and closing of the relay switch is controlled by the central controller through a digital signal sent by the remote I / O interface. The output current of the constant current power supply module is configured by the central controller through a digital communication interface. The two wires Force+ and Force- of the current loop are connected to the two poles of the resistor under test through a jack and the excitation current is applied to the resistor under test. The two wires Sense+ and Sense- of the voltage sampling circuit are connected to the two poles of the resistor under test through a horn plug and the voltage drop across the resistor under test by the excitation current is collected. The voltage drop signal is converted into a digital signal by a filter circuit, an amplifier circuit and an ADC analog-to-digital converter and then transmitted to the central controller. The central controller configures the excitation current of the resistor under test and calculates the resistance value of the resistor under test after collecting the voltage drop. The constant current power supply module includes a power supply input terminal, an EMI filter, and a control board connected in sequence. The EMI filter is connected in series between the power supply input terminal and the control board to suppress electromagnetic interference from the external power grid. Ceramic capacitors or electrolytic capacitors are connected in parallel at the power supply pins of the power-consuming components of the control board to form a two-stage filter network to filter out electromagnetic interference inside the control board. The EMI filter includes a common-mode inductor and a differential-mode capacitor. The inductance of the common-mode inductor is 1mH-10mH, and the capacitance of the differential-mode capacitor is 1000pF-0.1μF. The common-mode inductor and the differential-mode capacitor are connected in series and then connected to the power supply input terminal. An optocoupler is connected in series between the relay switch and the remote I / O interface. The input end of the optocoupler is connected to the remote I / O interface and receives digital control signals. The output end of the optocoupler is connected to the control pin of the relay drive circuit, transmitting the isolated digital control signals to the relay switch to control the on / off state of the current loop. The input-output voltage of the optocoupler is not less than 2500V to achieve electrical isolation of the control signals and suppression of electromagnetic interference.

2. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 1, characterized in that, The two wires Force+ and Force- of the current loop and the two wires Sense+ and Sense- of the voltage sampling loop are electrically isolated by Kelvin connection.

3. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 1, characterized in that, The relay driving circuit includes an NPN transistor amplifier module and a freewheeling diode. The collector of the NPN transistor amplifier module is connected in series with the relay coil, the emitter of the NPN transistor amplifier module is grounded, and the base of the NPN transistor amplifier module receives the output signal of the optocoupler through a 1kΩ resistor.

4. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 1, characterized in that, The digital signal line connecting the relay switch to the I / O interface uses a double-shielded coaxial cable. The coaxial cable has a center conductor, an insulation layer, an inner aluminum foil shielding layer, a braided mesh outer shielding layer, and an outer sheath arranged sequentially from the inside to the outside. The inner aluminum foil shielding layer and the outer braided mesh shielding layer are grounded through multi-strand copper core wires. One end of each multi-strand copper core wire is connected to the grounding copper busbar of the circuit board, and the other end is connected to the system grounding grid. The grounding resistance is ≤2 ohms.

5. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 1, characterized in that, The at least two measurement units are connected in parallel to the output terminal of the constant current power supply module.

6. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 5, characterized in that, The constant current power supply module includes a resistor. The positive voltage test terminal, negative voltage test terminal, positive current output terminal, and negative current output terminal of the resistor are respectively connected to the common terminal of each measurement unit. Each measurement unit is connected in series with an optocoupler. The input terminal of the optocoupler is connected to a remote I / O interface and receives digital control signals. By controlling the on / off state of the optocoupler, the resistor can switch between multiple resistors under test for measurement. The central controller uses a resistor meter to set a constant excitation current to collect the voltage drop across the resistor under test and then calculates the resistance value of the resistor under test.

7. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 1, characterized in that, It also includes an EtherCAT bus communication module. The central controller connects to at least two anti-interference resistor detection circuit boards through the EtherCAT bus communication module and realizes inter-board synchronous control with a synchronization period of ≤1ms. It supports a maximum of 384 measurement channels.

8. An anti-interference resistance detection system based on four-wire measurement, characterized in that, The interference-resistant resistance detection circuit board based on four-wire measurement according to any one of claims 1-7.

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