OS test adapter PCB with four-wire precision resistance measurement

Abstract

The utility model discloses a kind of OS test switching PCB with four-wire system precision resistance measurement, including PCB substrate, OS test signal switching module, four-wire system resistance measurement module, relay switching unit, ADC measurement circuit and I2C communication interface.OS test signal switching module is docked OS tester, realize conducting and insulation test.Four-wire system resistance measurement module adopts constant-current source and four-wire system kelvin measurement mode, rely on differential amplifier circuit and high-precision ADC, complete 0.1Ω~40Ω small resistance precision measurement.Relay switching unit realizes two types of test path interlock switching and electrical isolation, and prevents signal mutual interference.The utility model integrates conducting test switching and precision resistance measurement function, compact structure, high measurement accuracy, good isolation, can realize DUT framework and ground end resistance on-line automation detection, adapt OS test system, effectively improve test efficiency and operation reliability.

Description

Technical Field

[0001] This utility model relates to the field of electronic testing equipment technology, specifically to an adapter PCB board that integrates OS (Open / Short, conduction / insulation) continuity testing and four-wire precision resistance measurement. Background Technology

[0002] In the production and testing of electronic products, OS (Output Controller) testers are widely used for rapid testing of signal continuity and insulation. Some products require simultaneous testing of the contact resistance between the DUT (Device Under Test) frame and the ground terminal. Traditional OS testing and resistance measurement use discrete equipment and two-wire measurement, which suffers from complex wiring, cumbersome switching, and low testing efficiency. The two-wire method cannot eliminate lead resistance and contact resistance errors, making it difficult to meet the high-precision measurement requirements for small resistance values ​​(0.1Ω). Furthermore, the lack of isolation between the continuity test and resistance measurement circuits easily leads to signal crosstalk, affecting test stability. Therefore, there is an urgent need for an integrated PCB board that combines OS continuity testing, four-wire precision resistance measurement, automatic switching, and reliable electrical isolation. Utility Model Content

[0003] This invention aims to overcome the shortcomings of existing technologies and provide an OS test adapter PCB board with four-wire precision resistance measurement. The board integrates OS continuity test adapter function and 0.1Ω~40Ω precision resistance measurement function. It uses relays to achieve path isolation and switching, and employs a four-wire Kelvin measurement method to eliminate measurement errors caused by leads, effectively improving test accuracy and work efficiency.

[0004] The specific technical solution is as follows: An OS test adapter PCB board with four-wire precision resistance measurement includes a PCB substrate, an OS test signal conversion module, a four-wire resistance measurement module, a relay switching unit, an ADC measurement circuit, and an I2C communication interface. The OS test signal conversion module has an external connector for connecting to an OS tester to achieve signal conduction conversion. The four-wire resistance measurement module includes a constant current source circuit, a current detection circuit, and a voltage detection circuit, and adopts four-wire Kelvin measurement with separate current and voltage loops. The relay switching unit connects to the DUT test terminal, the OS test signal conversion module, and the four-wire resistance measurement module respectively, realizing switching and electrical isolation between the two types of test paths. The ADC measurement circuit collects the output signals of the two detection circuits and transmits the sampled data to the upper processing unit via the I2C communication interface.

[0005] Furthermore, the four-wire resistance measurement module also includes an onboard reference resistor and two sets of Kelvin probes; the first set of Kelvin probes corresponds to the device under test frame (DUT_Frame), and the second set of Kelvin probes corresponds to the device under test ground terminal (DUT_GND); the two sets of Kelvin probes together constitute the four-wire Kelvin measurement structure.

[0006] Furthermore, the constant current source circuit is composed of an LM317 chip, which outputs a constant 10mA current.

[0007] Furthermore, each set of Kelvin probes includes a current driving terminal and a voltage sampling terminal; the output terminal of the constant current source circuit is connected to the first terminal of the onboard reference resistor; the first terminal of the onboard reference resistor is connected to the positive input terminal of the current detection circuit, and the second terminal of the onboard reference resistor is connected to the negative input terminal of the current detection circuit; the second terminal of the onboard reference resistor is connected to the current driving terminal of the first set of Kelvin probes; the voltage sampling terminal of the first set of Kelvin probes is connected to the positive input terminal of the voltage detection circuit; the current driving terminal of the second set of Kelvin probes is connected to the onboard ground terminal; the voltage sampling terminal of the second set of Kelvin probes is connected to the negative input terminal of the voltage detection circuit; the output terminals of the current detection circuit and the voltage detection circuit are respectively connected to the two input terminals of the ADC measurement circuit.

[0008] Furthermore, both the current detection circuit and the voltage detection circuit use AD820 differential operational amplifiers, and the two output signals are amplified by 10 times fixed gain before being input to the ADC measurement circuit.

[0009] Furthermore, the ADC measurement circuit uses the ADS1119 chip.

[0010] Furthermore, the relay switching unit disconnects the resistance measurement circuit under OS test conditions and connects the DUT to the resistance measurement circuit under resistance measurement conditions.

[0011] Furthermore, the resistance measurement range of the four-wire resistance measurement module is 0.1Ω to 40Ω.

[0012] Furthermore, all the circuits of the OS test signal conversion module, the four-wire resistance measurement module, the relay switching unit, the ADC measurement circuit, and the I2C communication interface are integrated and arranged on the PCB substrate.

[0013] Compared with the prior art, this utility model has the following advantages: 1. This device integrates OS continuity test conversion function and precision resistance measurement function into one, and all functional circuits are integrated on a single PCB substrate, simplifying the on-site wiring process and equipment layout, and effectively improving the overall testing efficiency.

[0014] 2. The four-wire Kelvin measurement structure with separate current and voltage loops can completely eliminate measurement errors caused by lead resistance and probe contact resistance, and can stably achieve high-precision resistance detection within the range of 0.1Ω to 40Ω.

[0015] 3. This utility model adopts a four-wire resistance measurement architecture and is equipped with a differential amplifier circuit to amplify and process the detection signal, effectively optimizing the signal acquisition quality and suppressing common-mode interference. The comparative test of 100 repeated measurements on a standard resistor with a nominal value of 10.000Ω has verified that, compared with the traditional two-wire test scheme, it has achieved significant improvements in measurement accuracy, measurement stability and overall test efficiency. In terms of measurement accuracy, traditional two-wire measurement schemes suffer from a systematic overestimation due to the inherent influence of the loop lead resistance. The average measurement value of 100 measurements is only 10.1486Ω, corresponding to an average relative error of 1.486% and a maximum relative error of 2.01%, indicating low overall measurement accuracy. The four-wire measurement architecture of this invention eliminates the interference of lead resistance on the measurement results in principle. Combined with a differential amplifier circuit, it improves the signal-to-noise ratio and acquisition accuracy of the detection signal. Under the same test conditions, the average measurement value can reach 9.998704Ω, corresponding to an average relative error of only -0.01296% and a maximum relative error of ±0.01543%, which is far below the 0.05% high-precision threshold in the industrial field. The measurement accuracy is more than two orders of magnitude higher than that of the traditional two-wire scheme. In terms of measurement stability, traditional two-wire measurement schemes have a measurement range of 0.107Ω and a coefficient of variation of 0.404%, resulting in significant overall measurement fluctuations that are difficult to meet the stability requirements of industrial scenarios. This invention's scheme, however, achieves a range of only 0.001543Ω after 100 measurements, with a relative fluctuation of 0.01543%, far exceeding the conventional industrial control stability standard of 0.02%. The extremely low dispersion across multiple measurements demonstrates excellent measurement repeatability and stability. Furthermore, thanks to the advantages of the four-wire architecture measurement principle and the optimization of signal acquisition quality by the differential amplifier circuit, the scheme reduces invalid sampling and signal conditioning time, resulting in a comprehensive testing efficiency improvement of over 50% compared to traditional testing schemes. It is well-suited for applications such as PCB batch testing and rapid industrial field inspection, effectively overcoming the technical shortcomings of existing two-wire measurement schemes, including insufficient accuracy, weak anti-interference capabilities, and low testing efficiency, significantly improving the accuracy, reliability, and testing efficiency of resistance measurement.

[0016] 4. By relying on the relay switching unit to complete the switching and electrical isolation of different test paths, the two working modes of OS test and resistance measurement do not interfere with each other and will not affect the normal testing of the device under test. The equipment has better safety and external compatibility.

[0017] 5. The overall system adopts a mature circuit architecture that combines a constant current source circuit, a differential amplifier circuit, and a high-precision ADC. The hardware is stable in operation, has strong anti-interference capabilities, and has high reliability in long-term use.

[0018] 6. The device is equipped with an I2C communication interface to realize digital data transmission, which can be directly adapted to existing mainstream OS testing platforms. It has strong versatility and is very suitable for automated testing scenarios in mass production lines. Attached Figure Description

[0019] Figure 1 Overall circuit structure block diagram; Figure 2 Product signal interface pin definition diagram; Figure 3 OS test signal conversion module pin definition diagram; Figure 4 , relay switching module; Figure 5 1. Constant current source circuit block diagram; Figure 6 Block diagram of differential amplifier circuit for current and voltage detection; Figure 7 ADC measurement circuit block diagram; Figure 8 I2C communication interface circuit schematic diagram. Detailed Implementation

[0020] like Figure 1 As shown, the OS test adapter PCB board with four-wire precision resistance measurement disclosed in this utility model includes a PCB substrate, an OS test signal adapter module, a four-wire resistance measurement module, a relay switching unit, an ADC measurement circuit, and an I2C communication interface.

[0021] The product signal is transmitted via two wiring paths: one part of the signal is directly connected to the OS test signal conversion module, and finally connected to the OS test instrument; the relay switching unit is connected to four physical probes, two on the side of the device under test and two on the ground terminal. (e.g.) Figure 2 As shown, the two probes on the device under test (DUT) side correspond to Probe signals A1 and A2, and the two probes on the ground side correspond to signals Dut_GND1 and Dut_GND2. All four probes are connected to the relay module. In the default operating state of the relay module, the ground signal and probe signals are directly connected to the OS test signal conversion module and then connected to the OS test instrument. This enables all product signals to be connected to the OS conversion module in the normal mode, completing the open-circuit and short-circuit continuity tests of the device.

[0022] When switching to resistance measurement mode, the relay module activates, switching DUT_GND1, DUT_GND2 and Probe signals A1, A2 from the OS test path to the DUT resistor under test terminal, connecting to the four-wire resistance measurement module, and simultaneously achieving electrical isolation between the two types of test paths.

[0023] The four-wire resistance measurement module is the core component of this invention. As shown in Figure 2, the module includes a constant current source circuit, an onboard reference resistor R_REF, a current monitoring circuit, and a voltage monitoring circuit. The four physical probes connected to the measurement circuit are divided into two groups of functional probes according to the four-wire Kelvin measurement principle: the first group consists of two probes A1 and A2 on the device under test (DUT) side, corresponding to the DUT frame Probe, serving as the current drive terminal I+ and the voltage sampling terminal V+, respectively; the second group consists of two probes DUT_GND1 and DUT_GND2 on the grounding terminal, corresponding to the DUT grounding terminal DUT_GND, serving as the current drive terminal I- and the voltage sampling terminal V-, respectively.

[0024] The constant current source circuit uses an LM317 three-terminal adjustable voltage regulator. Its output current is determined by the inherent reference voltage of the LM317, satisfying the formula... The constant current source provides a constant test current to the circuit, and the output is connected to the first terminal of the onboard reference resistor R_REF. The constant current source, the onboard reference resistor, and the resistor under test (DUT) are connected in series to form a complete test current loop.

[0025] The current monitoring circuit uses an AD820 high-precision, low-noise differential operational amplifier to form a 10x fixed-gain differential amplifier circuit. The two input terminals of the current monitoring circuit are connected to the first and second terminals of the onboard reference resistor R_REF, respectively, to acquire the voltage across the sampling resistor R_REF. After amplification by 10x fixed gain, the output voltage signal is generated. Since the voltage signal is amplified, it is necessary to reconstruct the true voltage across the sampling resistor, and then calculate the actual current in the circuit according to Ohm's law. .

[0026] The voltage monitoring circuit uses the AD820 high-precision, low-noise differential operational amplifier to form a 10x fixed-gain differential amplifier circuit. The two input terminals of the voltage monitoring circuit are connected to the voltage sampling terminals V+ and V- of the first and second sets of functional probes, respectively, to acquire the voltage across the device under test (DUT). After amplification by 10x fixed gain, the output voltage signal is generated. Since the voltage signal is an amplified signal, it is necessary to reconstruct the true voltage across the device under test, and then calculate the resistance value using Ohm's law. .

[0027] The ADC measurement circuit uses the ADS1119 high-precision analog-to-digital converter chip. Its two analog input terminals are connected to the output terminals of the current monitoring circuit and the voltage monitoring circuit, respectively, to receive... and Two analog voltage signals are used. The ADC measurement circuit establishes communication with the main control board through the I2C interface. First, it converts the acquired analog voltage signal into a digital signal. At the same time, it determines whether the output current of the constant current source is stable based on the digital signal. Under the premise of stable current, it calculates the resistance value of the product under test by combining the acquired data.

[0028] In this embodiment, the four-wire resistance measurement module has the following measurement specifications: resistance measurement range of 0.1Ω to 40Ω, test current of 10mA, and adopts four-wire Kelvin measurement method, which can meet the precision measurement requirements of small resistance contact resistance.

[0029] The working principle of this utility model is as follows: When performing OS testing, the relay switching unit remains in its default state, connecting the DUT test terminal to the OS test signal conversion module while disconnecting the four-wire resistance measurement module. The OS tester sends test signals to the device under test through the conversion board to complete the open / short circuit test.

[0030] During resistance measurement, the relay switching unit connects the DUT test terminal to the four-wire resistance measurement module while simultaneously disconnecting the OS test signal conversion module. The constant current source circuit outputs a constant 10mA current, which flows sequentially through the onboard reference resistor R_REF, the current drive terminal I+ of the first set of functional probes, the resistor under test R_DUT, the current drive terminal I- of the second set of functional probes, and finally returns to the onboard ground terminal.

[0031] The current monitoring circuit acquires the voltage across the onboard reference resistor R_REF, amplifies and converts it, and then calculates the actual current in the circuit. The voltage monitoring circuit acquires the voltage across the resistor R_DUT, amplifies and converts it to obtain the corresponding voltage signal. Because a four-wire Kelvin measurement structure is used, no current flows through the voltage sampling circuit; therefore, the lead resistance and contact resistance at the voltage sampling terminals do not affect the measurement results.

[0032] The ADC measurement circuit converts the amplified voltage signal into a digital signal and transmits it to the host computer. The host computer then obtains the precise resistance value of the measured resistor based on the above calculation logic.

[0033] This invention achieves a seamless integration of OS testing and precision resistance measurement through integrated design and four-wire Kelvin measurement technology, significantly improving testing efficiency and measurement accuracy, and has broad application prospects.

[0034] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A PCB board for OS test adapter with four-wire precision resistance measurement, comprising a PCB substrate and an OS test signal adapter module, characterized in that: It also includes a four-wire resistance measurement module, a relay switching unit, an ADC measurement circuit, and an I2C communication interface; the OS test signal conversion module has an external connector for connecting to the OS tester to achieve signal conduction conversion; the four-wire resistance measurement module includes a constant current source circuit, a current detection circuit, and a voltage detection circuit, and adopts a four-wire Kelvin measurement with separate current and voltage loops; the relay switching unit connects to the DUT test terminal, the OS test signal conversion module, and the four-wire resistance measurement module respectively, realizing the switching and electrical isolation of the two types of test paths; the ADC measurement circuit collects the output signals of the two detection circuits and transmits the sampled data to the upper processing unit via the I2C communication interface.

2. The OS test adapter PCB board with four-wire precision resistance measurement according to claim 1, characterized in that: The four-wire resistance measurement module also includes an onboard reference resistor and two sets of Kelvin probes; the first set of Kelvin probes corresponds to the device under test frame Probe, and the second set of Kelvin probes corresponds to the device under test ground terminal DUT_GND; the two sets of Kelvin probes together constitute the four-wire Kelvin measurement structure.

3. The OS test adapter PCB board with four-wire precision resistance measurement according to claim 1, characterized in that: The constant current source circuit is composed of an LM317 chip and outputs a constant 10mA current.

4. The OS test adapter PCB board with four-wire precision resistance measurement according to claim 2 or 3, characterized in that: Each set of Kelvin probes includes a current drive terminal and a voltage sampling terminal; the output terminal of the constant current source circuit is connected to the first terminal of the onboard reference resistor; the first terminal of the onboard reference resistor is connected to the positive input terminal of the current detection circuit, the second terminal of the onboard reference resistor is connected to the negative input terminal of the current detection circuit; the second terminal of the onboard reference resistor is connected to the current drive terminal of the first set of Kelvin probes. The voltage sampling terminal of the first set of Kelvin probes is connected to the positive input terminal of the voltage detection circuit; The current drive terminal of the second set of Kelvin probes is connected to the onboard ground terminal; the voltage sampling terminal of the second set of Kelvin probes is connected to the negative input terminal of the voltage detection circuit; the output terminals of the current detection circuit and the voltage detection circuit are respectively connected to the two input terminals of the ADC measurement circuit.

5. The OS test adapter PCB board with four-wire precision resistance measurement according to claim 1, characterized in that: Both the current detection circuit and the voltage detection circuit use AD820 differential operational amplifiers. The two output signals are amplified by 10 times fixed gain and then input to the ADC measurement circuit.

6. The OS test adapter PCB board with four-wire precision resistance measurement according to claim 1, characterized in that: The ADC measurement circuit uses the ADS1119 chip.

7. The OS test adapter PCB board with four-wire precision resistance measurement according to claim 1, characterized in that: The relay switching unit disconnects the resistance measurement circuit under OS test conditions and connects the DUT to the resistance measurement circuit under resistance measurement conditions.

8. The OS test adapter PCB board with four-wire precision resistance measurement according to claim 1, characterized in that: The resistance measurement range of the four-wire resistance measurement module is 0.1Ω to 40Ω.

9. The OS test adapter PCB board with four-wire precision resistance measurement according to claim 1, characterized in that: All circuits of the OS test signal conversion module, the four-wire resistance measurement module, the relay switching unit, the ADC measurement circuit, and the I2C communication interface are integrated and arranged on the PCB substrate.

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