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

Abstract

The invention discloses an anti-interference resistance detection circuit board and system based on four-wire system measurement, and relates to the technical field of industrial automatic detection. Aiming at the problems of low measurement precision, weak interference resistance and limited channel expansion of a traditional two-wire system, a current loop and a voltage sampling loop which are independently and electrically isolated are adopted, and a lead resistance error is eliminated through Kelvin connection; an EMI filter, a photoelectric coupler and a double-layer shielding cable are integrated, so that the influence of electromagnetic interference and a ground loop is inhibited; a single circuit board supports the parallel connection of at least two measuring units, realizes the cascade connection of multiple boards by combining an EtherCAT bus, and supports 384 channels at most. The measuring error is smaller than or equal to + / -0.1%, the single-channel detection time is smaller than or equal to 10 ms, the requirements of high-density and high-beat scenes such as perovskite photovoltaic glass are met, the method is suitable for 100-100 Momega wide-range resistance measurement, the signal transmission error rate in the industrial strong electromagnetic environment is extremely low, and the detection precision and the system reliability are remarkably improved.

Description

Technical Field

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

[0002] In the field of industrial automation testing, resistance measurement is a key link 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 battery cells are integrated on a single piece of glass, and the production line rhythm requires that all battery resistance tests of a single piece of glass be completed within 30 seconds. This places extremely high demands on the speed, accuracy and anti-interference ability of battery testing.

[0003] Traditional resistance testing equipment typically uses a two-wire measurement relay board as a signal transfer device. Its working principle is to apply current to the object being measured through two wires, collect the voltage signal, and then calculate the resistance value according to Ohm's law. This two-wire measurement method has the following drawbacks: 1. Insufficient measurement accuracy. In two-wire measurements, the wire resistance is included in the resistance of the object being measured, resulting in measurement errors. This error is particularly significant in long-distance or low-resistance measurements. 2. Weak anti-interference capability. Industrial environments are prone to a large number of electromagnetic interference, signal crosstalk and other problems. Traditional relay boards do not provide effective protection against power supply fluctuations, control signal interference and signal transmission interference, which can easily lead to abnormal measurement data. 3. In addition, traditional relay boards support limited detection channels, usually ≤32 channels. In addition, traditional relay boards do not support multi-board coordinated control and cannot meet the batch testing requirements of high-density detection scenarios such as perovskite photovoltaic glass.

[0004] Therefore, there is an urgent need for a relay board and detection system that can simultaneously improve measurement accuracy and anti-interference capabilities and support flexible expansion, so as to solve the application bottleneck of existing technologies in high-density, high-beat industrial detection scenarios. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide an anti-interference relay board and a detection system based on four-wire measurement. According to an embodiment of the present invention, a first solution is provided: an anti-interference resistance detection circuit board based on four-wire measurement, comprising at least two measurement units; The measuring unit includes an independent electrically isolated current loop and a voltage sampling loop; The current loop is connected to the constant current power module through a relay switch. The on / off 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 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 to be measured through a horn plug and the excitation current is applied to the resistor to be measured. The two wires Sense+ and Sense- of the voltage sampling circuit are in contact with the two poles of the resistor to be measured through the horn plug and collect the voltage drop of the excitation current passing through the resistor to be measured. The voltage drop signal is converted into a digital signal through the filtering circuit, the amplifying circuit and the ADC analog-to-digital converter and then transmitted to the central controller; The central controller configures the excitation current of the resistor to be measured and calculates the resistance value of the resistor to be measured after collecting the voltage drop.

[0006] 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 through Kelvin connections.

[0007] 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, and a ceramic capacitor or an electrolytic capacitor is connected in parallel to the power pin of the power consumption component of the control board to form a secondary 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.

[0008] Furthermore, a photoelectric coupler is connected in series between the relay switch and the remote I / O interface. The input end of the photoelectric coupler is connected to the remote I / O interface and receives a digital control signal. The output end of the photoelectric coupler is connected to the control pin of the relay drive circuit to transmit the isolated digital control signal to the relay switch to control the on and off of the current loop. The input and output interval voltage of the photoelectric coupler is not less than 2500V to achieve electrical isolation of the control signal and electromagnetic interference suppression.

[0009] Furthermore, the relay drive circuit includes an NPN-type transistor amplifier module and a freewheeling diode, the collector of the NPN-type transistor amplifier module is connected in series with the relay coil, the emitter of the NPN-type transistor amplifier module is grounded, and the base of the NPN-type transistor amplifier module receives the output signal of the photocoupler through a 1kΩ resistor.

[0010] Furthermore, the digital signal line connecting the relay switch and the I / O interface adopts a double-shielded coaxial cable. The coaxial cable is provided with a central conductor, an insulation layer, an aluminum foil inner shielding layer, a braided mesh outer shielding layer and an outer sheath from the inside to the outside. The aluminum foil inner shielding layer and the braided mesh outer shielding layer are respectively grounded through multiple copper core wires. One end of the multiple copper core wires is connected to the small grounding copper bus of the circuit board, and the other end is connected to the system grounding network, and the grounding resistance is ≤2 ohms.

[0011] Furthermore, the at least two measuring units are connected in parallel to the output end of the constant current power supply module.

[0012] Furthermore, the constant current power supply module includes a resistance meter, wherein the positive voltage test terminal, the negative voltage test terminal, the positive current output terminal, and the negative current output terminal of the resistance meter are respectively connected to the common terminal of each measuring unit, each measuring unit is connected in series with a photoelectric coupler, the input terminal of the photoelectric coupler is connected to the remote I / O interface and receives a digital control signal, and controls the on-off state of the photoelectric coupler to control the resistance meter to switch between the multiple resistances to be measured; The central controller collects the voltage drop across the resistor to be measured by configuring a constant excitation current through a resistance meter and then calculates the resistance value of the resistor to be measured.

[0013] Furthermore, it also includes an EtherCAT bus communication module. The central controller connects at least two anti-interference resistance detection circuit boards through the EtherCAT bus communication module and realizes synchronous control between the boards. The synchronization period is ≤1ms and supports a maximum expansion of 384 measurement channels.

[0014] According to an embodiment of the present invention, using 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: An anti-interference resistance detection system based on four-wire measurement comprises any one of the above-mentioned anti-interference resistance detection circuit boards based on four-wire measurement.

[0015] Compared with the existing technology, the technical solution provided by this application has the following unique beneficial effects: The system uses independent, electrically isolated current and voltage sampling circuits, and Kelvin connections to prevent the influence of wire and contact resistance on measurement results. This reduces the error to within ±0.1%, especially in low-resistance measurement scenarios. This solves the problem of wire resistance being included in the measured value in traditional two-wire measurements. The constant-current power supply module implements current parameter configuration through the digital communication interface of the central controller, resulting in excellent output current stability. Combined with a 16-bit ADC, it ensures high-precision conversion of voltage sampling signals, further improving the accuracy of resistance calculations. The multi-level electromagnetic interference suppression design and signal link isolation protection can effectively filter out the high-frequency noise inside the circuit board, while ensuring stable signal transmission in strong industrial electromagnetic environments; A single circuit board supports multiple measurement units connected in parallel, with channel switching independently controlled by optocouplers. Single-channel measurement time is less than 10ms, meeting the production line tact requirements for perovskite photovoltaic glass, which requires full-board testing within a specified timeframe (e.g., 30s). Inter-board synchronization control based on the EtherCAT bus supports eight circuit boards connected in parallel to form 384 measurement channels, resolving the bottleneck of traditional relay boards in high-density testing scenarios. Expansion also eliminates the need for system recalibration. The present invention can be directly applied to batch resistance detection of products such as photovoltaic cells and electronic components. It is particularly suitable for scenarios with strong electromagnetic interference, high detection density, and strict precision requirements. It also supports adapting to a wide range of resistance measurements from 100MΩ to 100MΩ by adjusting the constant current source parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] in: Figure 1 The figure is a framework diagram of an anti-interference resistance detection circuit board based on four-wire measurement in one embodiment. DETAILED DESCRIPTION

[0018] In order 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 in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of this application.

[0019] Example 1 The technical problem solved by this embodiment is that the existing resistance detection equipment usually uses a relay board of a two-wire measurement method as a signal adapter. Its working principle is to apply current to the object to be measured through two wires and collect voltage signals, and then calculate the resistance value according to Ohm's law. The two-wire measurement method has the following defects: insufficient measurement accuracy. In two-wire measurement, the wire resistance will be included in the resistance value of the object to be measured, resulting in measurement errors, especially in long-distance or small resistance measurements. The error is more significant; weak anti-interference ability. There are a lot of electromagnetic interference, signal crosstalk and other problems in the industrial environment. The traditional relay board does not take effective protective measures against power fluctuations, control signal interference and signal transmission interference, which can easily lead to abnormal measurement data; in addition, the detection channels supported by the traditional relay board single board are limited, usually ≤32 channels, and the traditional relay board single board does not support multi-board collaborative control, and cannot meet the batch testing requirements of high-density detection scenarios such as perovskite photovoltaic glass. Therefore, there is an urgent need for a relay board and detection system that can simultaneously improve measurement accuracy, anti-interference ability and support flexible expansion to solve the application bottleneck of the existing technology in high-density, high-beat industrial detection scenarios.

[0020] This embodiment specifically provides an anti-interference resistance detection circuit board based on four-wire measurement, including at least two measurement units; The measuring unit includes an independent electrically isolated current loop and a voltage sampling loop; The current loop is connected to the constant current power module through a relay switch. The on / off 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 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 to be measured through a horn plug and the excitation current is applied to the resistor to be measured. The two wires Sense+ and Sense- of the voltage sampling circuit are in contact with the two poles of the resistor to be measured through the horn plug and collect the voltage drop of the excitation current passing through the resistor to be measured. The voltage drop signal is converted into a digital signal through the filtering circuit, the amplifying circuit and the ADC analog-to-digital converter and then transmitted to the central controller; The central controller configures the excitation current of the resistor to be measured and calculates the resistance value of the resistor to be measured after collecting the voltage drop.

[0021] This embodiment is an anti-interference resistance detection circuit board based on four-wire measurement, such as Figure 1As shown in the figure, 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 end of the constant current power supply module. The central controller configures the constant current power supply parameters through the digital communication interface and controls the on and off of the measurement unit through the remote I / O interface. At the same time, multi-board collaborative expansion is achieved through the EtherCAT bus.

[0022] Each measurement unit includes an independent electrically isolated current loop and voltage sampling loop, which are physically separated by Kelvin connections to avoid the influence of wire resistance and contact resistance on measurement accuracy.

[0023] The measurement unit's current circuit is connected to a constant-current power supply module via an electromagnetic relay. The relay's on / off control is controlled by a digital signal sent by the central controller via the 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. Its input / output voltage is ≥2500V, effectively suppressing electromagnetic interference. The measurement unit's drive circuit utilizes an NPN transistor amplifier module. The transistor base receives the optocoupler's output signal 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 reverse electromotive force damage when the coil is de-energized. The wire connections are as follows: the Force+ and Force- wires of the current circuit connect to the terminals of the resistor under test via a horn plug. Silver-plated copper wire with a cross-sectional area of ​​0.5mm² is used to minimize loop resistance.

[0024] The measurement unit's voltage sampling circuit also connects its Sense+ and Sense- wires to the resistor under test via horn connectors, collecting the voltage drop generated by the excitation current across the resistor. The signal then passes through a second-order RC filter, an instrumentation amplifier, and a 16-bit ADC. The converted digital signal is then transmitted to the central controller via the I²C bus. To mitigate interference, a 10μF tantalum capacitor and a 0.1μF ceramic capacitor are connected in parallel to the ADC's reference voltage terminal, forming a decoupling network to suppress the impact of power supply noise on sampling accuracy.

[0025] The constant-current power module's anti-interference design utilizes a high-precision resistance meter. Its output current range is 1μA-1A, with stability ≤0.01% / h. To suppress grid interference, an EMI filter is connected in series with the module input. Specifically, a common-mode inductor (a magnetic ring type with an inductance of 10mH and a rated current of 3A) and an X7R ceramic differential-mode capacitor are connected in series with the common-mode inductor and then connected to the power input. Furthermore, a 10μF electrolytic capacitor and a 0.1μF ceramic capacitor are connected in parallel to the power pins of the control board's power-consuming components, forming a two-stage filtering network to filter out high-frequency noise within the board.

[0026] Signal transmission and grounding: Shielded cable selection: Double-shielded coaxial cable is used for the digital signal lines between the relay switches and the I / O interface. Its structure, from inside to outside, consists of: a center conductor, polyethylene insulation, an inner aluminum foil shield, a tinned copper braid outer shield, and a PVC outer jacket. The inner and outer shields are each grounded via multiple strands of copper wire, with a ground resistance of ≤2Ω. Grounding design: An independent grounding busbar is installed on the circuit board, connected to the system ground grid via a 6mm² copper stud, achieving single-point grounding and preventing ground loop interference.

[0027] To meet the needs of high-density testing, this embodiment supports multi-board collaboration. A central controller connects eight test circuit boards via an EtherCAT bus communication module, achieving inter-board synchronization with a synchronization cycle of ≤1ms. Each circuit board contains 32 measurement units, which can be expanded to 256 measurement channels across eight boards. Single-channel measurement time is ≤10ms, meeting the production line requirement of completing full-board testing of perovskite photovoltaic glass (each panel has 200 cells) within 30 seconds.

[0028] Workflow: S1: parameter configuration, the central controller sends instructions to the constant current power module through the digital communication interface (RS485 protocol) to configure the excitation current; S2: Channel switching: the central controller sends a control signal through the remote I / O interface, which drives the relay switch after isolation by the photoelectric coupler to select the current loop of the target measurement unit; S3: Signal acquisition: The voltage sampling circuit collects the voltage drop across the resistor to be measured through Sense+ and Sense-, and transmits it to the central controller after filtering, amplification and ADC conversion; 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; S5: Multi-board synchronization: Through the distributed clock synchronization function of the EtherCAT bus, parallel measurement of multiple circuit boards is achieved to improve detection efficiency.

[0029] The independent electrically isolated current loop and voltage sampling loop are adopted, and the Kelvin connection is used to avoid the influence of wire resistance and contact resistance on the measurement results. Especially in the small resistance measurement scenario, the error can be reduced to within ±0.1%, which solves the problem of wire resistance being included in the measured value in traditional two-wire measurement; the constant current power supply module realizes current parameter configuration through the digital communication interface of the central controller, and has good output current stability. With the 16-bit ADC analog-to-digital converter, it ensures high-precision conversion of voltage sampling signals, further improving the accuracy of resistance calculation; it adopts 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 strong industrial electromagnetic environments; a single circuit board supports It supports multiple measurement units in parallel and independently controls channel switching through optocouplers. The measurement time of a single channel is less than 10ms, meeting the production line rhythm requirement of perovskite photovoltaic glass to complete full-board detection within a specified time (30S, etc.). Based on the inter-board synchronous control of the EtherCAT bus, it supports 8 circuit boards in parallel to form 384 measurement channels, solving the bottleneck that traditional relay boards cannot meet high-density detection scenarios, and the expansion process does not require recalibration of the system. The present invention can be directly applied to batch resistance detection of products such as photovoltaic cells and electronic components, and is particularly suitable for scenarios with strong electromagnetic interference, high detection density, and strict precision requirements. At the same time, it supports adapting to the wide range of resistance measurement needs of 100MΩ~100MΩ by adjusting the constant current source parameters.

[0030] Example 2 This embodiment provides a specific anti-interference resistance detection circuit board based on four-wire measurement, including at least two measurement units; the measurement unit includes an independent electrically isolated current loop and voltage sampling loop; the current loop is connected to the constant current power supply module through a relay switch, and the on and off 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 to be measured through a horn plug and the excitation current is applied to the resistor to be measured; the two wires Sense+ and Sense- of the voltage sampling loop are connected to the two poles of the resistor to be measured through a horn plug and collect the voltage drop of the excitation current through the resistor to be measured. The voltage drop signal is converted into a digital signal through a filtering circuit, an amplifying 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 to be measured and calculates the resistance value of the resistor to be measured after collecting the voltage drop.

[0031] 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 through Kelvin connections.

[0032] 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. A ceramic capacitor or an electrolytic capacitor is connected in parallel to the power pin of the power-consuming component of the control board to form a secondary 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 and then connected to the power supply input terminal.

[0033] Specifically, a photocoupler is connected in series between the relay switch and the remote I / O interface. The input end of the photocoupler is connected to the remote I / O interface and receives a digital control signal. The output end of the photocoupler is connected to the control pin of the relay drive circuit and transmits the isolated digital control signal to the relay switch to control the on and off of the current loop. The input and output interval voltage of the photocoupler is not less than 2500V to achieve electrical isolation of the control signal and suppress electromagnetic interference.

[0034] Specifically, the relay drive 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 photocoupler through a 1kΩ resistor.

[0035] Specifically, the digital signal line connecting the relay switch and the I / O interface adopts a double-shielded coaxial cable. The coaxial cable is provided with a center conductor, an insulation layer, an aluminum foil inner shielding layer, a braided mesh outer shielding layer and an outer sheath from the inside to the outside. The aluminum foil inner shielding layer and the braided mesh outer shielding layer are respectively grounded through multiple copper core wires. One end of the multiple copper core wires is connected to the small grounding copper bus of the circuit board, and the other end is connected to the system grounding network. The grounding resistance is ≤2 ohms.

[0036] 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 measuring unit, each measuring unit is connected in series with a photoelectric coupler, the input terminal of the photoelectric coupler is connected to the remote I / O interface and receives a digital control signal, and the resistor meter is controlled to switch between multiple resistors to be measured by controlling the on-off state of the photoelectric coupler; the central controller collects the voltage drop across the resistor to be measured by configuring a constant excitation current on the resistor meter and then calculates the resistance value of the resistor to be measured.

[0037] Specifically, it also includes an EtherCAT bus communication module. The central controller connects at least two anti-interference resistance detection circuit boards through the EtherCAT bus communication module and realizes synchronous control between the boards. The synchronization period is ≤1ms and supports a maximum expansion of 384 measurement channels.

[0038] This embodiment solves the problems of insufficient two-wire measurement accuracy (error ≤±0.1%), weak anti-interference capability, and limited number of channels in traditional two-wire measurement through 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 particularly suitable for industrial scenarios with strong electromagnetic interference and high detection density.

[0039] Example 3 Based on the four-wire measurement-based anti-interference resistance detection circuit board of Example 2, this embodiment is designed for on-resistance detection of IGBT modules in new energy vehicle motor controllers. It addresses the existing issues of insufficient measurement accuracy and low detection efficiency in strong electromagnetic interference environments. As the core power device in motor controllers, IGBT modules have an on-resistance, typically ranging from 1mΩ to 100mΩ, which directly affects heat dissipation and power loss, necessitating rapid batch detection within the production line.

[0040] This embodiment's test circuit board 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 testing. The central controller communicates with a host computer via EtherCAT. This single circuit board can cover all six on-resistance tests for a single IGBT module, with two channels reserved for redundancy.

[0041] Each measurement unit's current and voltage sampling circuits utilize a four-terminal Kelvin connection. Low-impedance silver-plated copper wire is used as the conductor, and contact is established with the collector-emitter pins of the IGBT module via spring-probe-style horn plugs with a contact resistance of less than 5mΩ, minimizing the impact of contact resistance on milliohm-level measurements. The voltage sampling circuit's filter circuit is optimized to a third-order Butterworth low-pass filter, coupled with a 24-bit ADC, ensuring a measurement resolution of 0.01mΩ for a 1mΩ resistor.

[0042] The constant-current power module features a dual-output design: one output range is 100mA to 1A, compatible with resistors from 1mΩ to 10mΩ, and the other output range is 10mA to 100mA. Range switching is automatic via the central controller's digital communication interface. An internal temperature compensation circuit is incorporated into the module: a negative temperature coefficient thermistor is connected in series between the EMI filter and the control board. This circuit monitors the ambient temperature in real time and provides feedback to the central controller. A software algorithm corrects current output deviations, maintaining a temperature drift of ≤±5ppm / °C.

[0043] To address high-frequency pulse interference on the motor controller production line, this embodiment adds a ferrite bead array to the signal chain, connected in parallel between the output of the optocoupler and the relay driver circuit to suppress high-frequency noise coupling. The relay switch control signal line uses a triple-shielded cable with an inner shield of aluminum foil and a double-layer braided mesh. The grounding method is optimized to multiple points (intervals ≤ 30 cm) to ensure that the shield layer's impedance is less than 1Ω in the high-frequency range.

[0044] The specific workflow is: S101: Automatic range switching: The central controller calls the preset parameters according to the IGBT module model and automatically configures the constant current power supply output. For example, when detecting a 1mΩ resistance, it outputs 1A current. S102: Synchronously sends 8 control signals through the remote I / O interface, which drive the relay switches of 8 measurement units after isolation by the photoelectric coupler, thus achieving parallel conduction of 8 channels; S103: 24-bit ADC synchronously collects 8-channel 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 less than 2ms. S104: The central controller calculates the on-resistance according to the formula R=U / I and uploads it to the host computer via the EtherCAT bus with a communication rate of 100Mbps. The single detection cycle is ≤40ms, meeting the production line beat requirements.

[0045] This embodiment, through multi-channel parallel detection, wide-range constant current output, and high-frequency interference suppression, achieves the following results on new energy vehicle IGBT module production lines: In a 1MHz electromagnetic interference environment, the measurement error of 1mΩ to 100mΩ resistors is ≤±0.05%; a single circuit board supports 8-channel parallel detection, and the detection time of a single IGBT module (6 resistors) is ≤40ms, a three-fold improvement compared to traditional equipment; and the operating temperature range is -40°C to 85°C, meeting the wide temperature requirements of automotive electronics production lines without the need for regular calibration. This embodiment can be directly integrated into the motor controller automated test platform or expanded to 32 channels via the EtherCAT bus, i.e., four circuit boards connected in parallel, to meet the needs of higher-capacity production lines.

[0046] Example 4 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 including at least two measurement units; the measurement unit including an independent electrically isolated current loop and voltage sampling loop; the current loop is connected to a constant current power supply module via a relay switch, the on / off of the relay switch is controlled by a central controller sending a digital signal via a remote I / O interface, the output current of the constant current power supply module is configured by the central controller via a digital communication interface, the two wires Force+ and Force- of the current loop are connected to the two poles of the resistor to be measured via a horn plug and an excitation current is applied to the resistor to be measured; the two wires Sense+ and Sense- of the voltage sampling loop are connected to the two poles of the resistor to be measured via a horn plug and collect the voltage drop of the excitation current through the resistor to be measured, the voltage drop signal is converted into a digital signal by a filtering circuit, an amplification 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 to be measured, collects the voltage drop, and calculates the resistance value of the resistor to be measured.

[0047] Those skilled in the art will appreciate that all or part of the processes in the above-described method embodiments can be implemented by instructing the relevant hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When executed, the program can include the processes of the above-described method embodiments. Any reference to memory, storage, database, or other media used in the various embodiments provided herein may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may 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), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct RAMbus dynamic RAM (DRDRAM), and RAMbus dynamic RAM (RDRAM).

[0048] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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.

[0049] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall 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 2 measuring units; The measuring unit includes an independent electrically isolated current loop and a voltage sampling loop; The current loop is connected to the constant current power module through a relay switch. The on / off 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 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 to be measured through a horn plug and the excitation current is applied to the resistor to be measured. The two wires Sense+ and Sense- of the voltage sampling circuit are in contact with the two poles of the resistor to be measured through the horn plug and collect the voltage drop of the excitation current passing through the resistor to be measured. The voltage drop signal is converted into a digital signal through the filtering circuit, the amplifying circuit and the ADC analog-to-digital converter and then transmitted to the central controller; The central controller configures the excitation current of the resistor to be measured and calculates the resistance value of the resistor to be measured after collecting the voltage drop.

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 through Kelvin connections.

3. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 1 is characterized in that: 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. The power pins of the power consumption components of the control board are connected in parallel with ceramic capacitors or electrolytic capacitors to form a secondary 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.

4. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 1, characterized in that: A photoelectric coupler is connected in series between the relay switch and the remote I / O interface. The input end of the photoelectric coupler is connected to the remote I / O interface and receives a digital control signal. The output end of the photoelectric coupler is connected to the control pin of the relay drive circuit and transmits the isolated digital control signal to the relay switch to control the on and off of the current loop. The input and output interval voltage of the photoelectric coupler is not less than 2500V to achieve electrical isolation of the control signal and electromagnetic interference suppression.

5. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 4, characterized in that: The relay drive 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 photoelectric coupler through a 1kΩ resistor.

6. 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 and the I / O interface adopts a double-shielded coaxial cable. The coaxial cable is provided with a central conductor, an insulation layer, an aluminum foil inner shielding layer, a braided mesh outer shielding layer and an outer sheath from the inside to the outside. The aluminum foil inner shielding layer and the braided mesh outer shielding layer are respectively grounded through multiple copper core wires. One end of the multiple copper core wires is connected to the small grounding copper busbar of the circuit board, and the other end is connected to the system grounding grid. The grounding resistance is ≤2 ohms.

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

8. The anti-interference resistance detection circuit board based on four-wire measurement according to claim 7, characterized in that: The constant current power supply module includes a resistor meter, wherein the positive voltage test terminal, the negative voltage test terminal, the positive current output terminal, and the negative current output terminal of the resistor meter are respectively connected to the common terminal of each measuring unit. Each measuring unit is connected in series with a photoelectric coupler. The input terminal of the photoelectric coupler is connected to the remote I / O interface and receives a digital control signal. By controlling the on-off state of the photoelectric coupler, the resistor meter is controlled to switch between multiple resistances to be measured. The central controller collects the voltage drop across the resistor to be measured by configuring a constant excitation current through a resistance meter and then calculates the resistance value of the resistor to be measured.

9. 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 at least two anti-interference resistance detection circuit boards through the EtherCAT bus communication module and realizes synchronous control between the boards. The synchronization period is ≤1ms and supports expansion of up to 384 measurement channels.

10. An anti-interference resistance detection system based on four-wire measurement, characterized in that: An anti-interference resistance detection circuit board based on four-wire measurement comprising any one of claims 1 to 9.

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