A testing device and method for measuring contact resistance of a four-wire probe

Abstract

The application aims to provide a testing device and method for measuring contact resistance of a four-wire probe. The application comprises a current source, a power supply voltage and a resistance to be measured, the resistance to be measured comprising a source end contact resistance, a detection end contact resistance and an equivalent product resistance, the current source being connected with the equivalent product resistance through the source end contact resistance, the equivalent product resistance being grounded through a current sampling resistance, the power supply voltage being connected with a pull-up resistance through a relay, the pull-up resistance being grounded through an equivalent input resistance, one end of the detection end contact resistance being connected with a node of the source end contact resistance and the equivalent product resistance, and the other end of the detection end contact resistance being connected with a node of the pull-up resistance and the equivalent input resistance. The application is applied to the technical field of four-wire measurement.

Description

Technical Field

[0001] This invention relates to the technical field of four-wire measurement, and particularly to a testing device and detection method for measuring the contact resistance of a four-wire probe. Background Technology

[0002] PCBA refers to Printed Circuit Board Assembly; Four-wire Resistance Test refers to four-wire resistance testing; on a benchtop multimeter, Source_P refers to the positive source terminal, Source_N refers to the negative source terminal, Sense_P refers to the positive sensing terminal, and Sense_N refers to the negative sensing terminal; B2BConnector refers to a board-to-board connector. Currently, resistance testing methods include four-wire and two-wire testing. For applications requiring small resistance values ​​and high accuracy, two-wire testing methods are insufficient, necessitating the use of four-wire testing. However, in confined spaces, the probes can only contact the device under test via the adapter board. Ensuring reliable contact of each of the four wires with the device under test is crucial for accurate test results.

[0003] Four-wire measurements are suitable for applications requiring high precision, such as those where the resistance under test is only 1Ω or less. Two-wire measurements are difficult to apply to applications with high precision requirements because the probe impedance is 0.5Ω, which can easily interfere with the actual test data. However, four-wire measurements require simultaneous operation of all four probes and secure contact with the device under test. Most users believe that as long as the four signals Source_P, Sense_P, Source_N, and Sense_N are all connected to the test circuit, the result will be accurate. In fact, they overlook the fact that if one or more of these four signals are disconnected, the test result will be inaccurate. However, in actual measurement scenarios, the spacing is very small, making it difficult to hold all four probes by hand. It is necessary to transfer the signals from the device under test through the PCB and adapter cables for testing. Depending on the actual physical connection, the following three situations will occur: Currently, resistance testing methods include four-wire and two-wire systems. For applications requiring small resistance values ​​and high precision, two-wire systems are insufficient, necessitating four-wire testing. However, in confined spaces, contact between the probe and the device under test (DUT) is limited to the lower probe and adapter plate. If there is severe contact failure or breakage at the source or sense, the four-wire test results become unreliable. For example, Chinese patent CN118376971A discloses a four-wire resistance measurement circuit continuity detection device and method. This method is best suited for testing severe contact failures, and the detected values ​​are close to the actual values. However, this method can only detect open circuits and cannot predict contact resistance. Therefore, it is necessary to provide a four-wire test device and method for measuring probe contact resistance. This method is low-cost, suitable for small-pitch applications, and addresses situations where manual operation is difficult to determine circuit continuity. It is easily portable, applicable to high-precision four-wire testing in various applications, automatically determines whether the test circuit has an open circuit, and automatically identifies severe contact failures, ensuring the reliability of the measurement results. Before each test, all circuits are confirmed to be normal to ensure test accuracy. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a test device and detection method based on four-wire measurement probe contact resistance. It is low in cost, applicable to small-pitch applications, and applications where it is difficult to judge the continuity of the circuit by hand. It is easy to transfer and applicable to high-precision four-wire testing in different applications. It automatically judges whether there is an open circuit in the test circuit and whether there is serious poor contact in the test circuit, which can ensure the reliability of the measurement results. Before each test, all circuits are confirmed to be normal before the test is performed to ensure the test accuracy.

[0005] The technical solution adopted in this invention is as follows: This invention includes a current source, a supply voltage, and a resistor to be measured. The resistor to be measured includes a source-end contact resistor, a detection-end contact resistor, and an equivalent product resistor. The current source is connected to the equivalent product resistor via the source-end contact resistor. The equivalent product resistor is grounded via a current sampling resistor. The supply voltage is connected to a pull-up resistor via a relay. The pull-up resistor is grounded via an equivalent input resistor. One end of the detection-end contact resistor is connected to the node of the source-end contact resistor and the equivalent product resistor, and the other end of the detection-end contact resistor is connected to the node of the pull-up resistor and the equivalent input resistor.

[0006] As can be seen from the above solution, the cost of this application is low, requiring only a few resistors and relays, making it suitable for small-pitch applications and applications where it is difficult to operate and determine the continuity of the circuit; it can automatically determine whether there is an open circuit in the test circuit; it can automatically determine whether there is serious poor contact in the test circuit; it has good compatibility and is suitable for high-precision four-wire testing in different applications.

[0007] In a preferred embodiment, the current source includes a voltage regulator, which is connected to a first operational amplifier, a second operational amplifier, and a digital-to-analog converter. The first operational amplifier, the second operational amplifier, and the digital-to-analog converter are connected in sequence, and the digital-to-analog converter is connected to PP_5V.

[0008] In a preferred embodiment, the resistor under test is connected to an adapter plate, and the resistor under test contacts the adapter plate via pin blocks.

[0009] In a preferred embodiment, the resistor under test is connected to an MCU module, which controls the current source to output a 50uA current to enable the relay switching circuit.

[0010] In a preferred embodiment, the relay is connected to a buffer amplifier, and the buffer amplifier is connected to an analog-to-digital converter. A preferred embodiment is that the detection method includes the following steps: Step A: Place the object to be tested on the acupoint and clamp it in place using a cylinder; Step B: Set up computer communication, control the cylinder to fix the test object, and the B2B connector of the test object contacts the adapter board through the pin block and is transferred to the test board through the adapter cable. Step C: Eliminate source-end false tests. Control the current source to output 50uA current via the MCU module to enable the relay switching circuit. Measure the voltage Vsampling across the current sampling resistor using the analog-to-digital converter. At this time, the actual current I flowing through the equivalent product resistor is: Under normal circumstances, the actual current I should be equal to the preset current. In this case, the possibility of mismeasurement at the source end is ruled out, and the test can continue. If they are not equal, there is a serious problem with the contact at the source end. If the actual current I = 0, there is a problem with the contact at the source end. In this case, the measurement should be stopped to avoid mismeasurement. Step D: Measure the contact resistance at the detection terminal. After eliminating source-end errors, enable the relay to introduce the supply voltage V_supply, which is 3.3V. Let point A be the node between the pull-up resistor and the equivalent input resistance, and point B be the node between the source-end contact resistance and the equivalent product resistance. Measure the voltage VA3V3 at point A using the analog-to-digital converter. Then, disable the relay and continue measuring the voltage VANO at point A. Based on the above measurements, the voltage V_B at point B is determined by the following formula: Therefore, the equivalent product resistance is: Therefore, the contact resistance of the detection end is: ; Step E: In the practical application scenario of this invention, contact resistance exceeding 40K Ohm results in unacceptable testing errors. Therefore, if the contact resistance R_Sense at the detection end is less than 40K Ohm, severe contact defects are ruled out, ensuring the accuracy of the four-wire measurement. The setting of the judgment condition for the contact resistance R_Sense at the detection end depends on the application scenario's requirements for testing accuracy. This requirement can be calibrated by measuring a standard resistor and can be determined and modified independently. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the present invention; Figure 2 This is a circuit system block diagram of the present invention; Figure 3 This is a test flowchart of the present invention; Figure 4 This is a simulation diagram of R_Sense from this invention; Figure 5 This is the circuit diagram of the adapter board; Figure 6 This is the circuit schematic of the MCU module. Detailed Implementation

[0012] like Figures 1 to 2 As shown, in this embodiment, the present invention includes a current source, a supply voltage, and a resistor under test. The resistor under test includes a source contact resistor R_Source, a sensing contact resistor R_Sense, and an equivalent product resistance R_Dut. The current source is connected to the equivalent product resistance R_Dut via the source contact resistor R_Source. The equivalent product resistance R_Dut is grounded via a current sampling resistor R_Sampling. The supply voltage is connected to a pull-up resistor R_Pullup via a relay K1004. The pull-up resistor R_Pullup is grounded via an equivalent input resistor R_Input. One end of the sensing contact resistor R_Sense is connected to the node of the source contact resistor R_Source and the equivalent product resistance R_Dut, and the other end of the sensing contact resistor R_Sense is connected to the node of the pull-up resistor R_Pullup and the equivalent input resistance R_Input.

[0013] The current source output is 50uA; the supply voltage is V_supply, which is 3.3V; the pull-up resistor R_Pullup is used to introduce the pull-up power supply variable, and in this circuit it is 10M ohm; the equivalent input resistance R_Input is the equivalent input resistance of the ADC chip, and in this circuit it is 2.1M ohm; the current sampling resistor R_Sampling is used to confirm the measured current, and in this circuit it is 10 ohm.

[0014] like Figures 1 to 2 As shown, in this embodiment, the current source includes a voltage regulator U1801, which is connected to a first operational amplifier U1802, a second operational amplifier U1805, and a digital-to-analog converter U1804. The first operational amplifier U1802, the second operational amplifier U1805, and the digital-to-analog converter U1804 are connected in sequence, and the digital-to-analog converter U1804 is connected to PP_5V. The current source is used to generate a constant current of 50uA and is responsible for providing the current source.

[0015] like Figure 5 As shown, in this embodiment, the resistor under test is connected to an adapter plate, and the resistor under test contacts the adapter plate through a pin block.

[0016] like Figure 6 As shown, in this embodiment, the resistor under test is connected to an MCU module, and the MCU module controls the current source to output a 50uA current, enabling the relay K1004 switching circuit.

[0017] like Figures 1 to 2 As shown, in this embodiment, the relay K1004 is connected to a buffer amplifier U1001, and the buffer amplifier U1001 is connected to an analog-to-digital converter U1002.

[0018] The buffer amplifier U1001 is a 25x op-amp IC. The resistance of the object under test is converted from voltage using Ohm's law. The analog-to-digital converter U1002 is a voltage acquisition IC (because U1002 is responsible for measuring voltage, its own reference voltage is 2048mV. Before entering U1002 for testing, it passes through R4 and R5 for a 1 / 2 voltage divider, so the maximum measurable voltage is 4096mV. Since the amplification factor of U1001 is 25x, 4096 / 25 = 163.84mV. The maximum resistance range is about 3200Ω, and the test result for a 1Ω resistor is 50uV).

[0019] like Figure 4As shown, in this embodiment, if the contact resistance exceeds 40K ohms, it will significantly affect the test accuracy, and at this point it will be judged as a serious contact failure. Therefore, the measurement will stop when the contact resistance R_Sense at the detection end exceeds 40K ohms to avoid false measurements. like Figure 3 As shown, in this embodiment, the detection method includes the following steps: Step A: Place the object to be tested on the acupoint and clamp it in place using a cylinder; Step B: Set up computer communication, control the cylinder to fix the test object, and the B2B connector of the test object contacts the adapter board through the pin block and is transferred to the test board through the adapter cable. Step C: Eliminate source-end false tests. Control the current source to output 50uA current via the MCU module, enabling the relay K1004 to switch the circuit. Measure the voltage Vsampling across the current sampling resistor R_Sampling via the analog-to-digital converter U1002. At this time, the actual current I flowing through the equivalent product resistor R_Dut is: Under normal circumstances, the actual current I should be equal to the preset current. In this case, the possibility of mismeasurement at the source end is ruled out, and the test can continue. If they are not equal, there is a serious problem with the contact at the source end. If the actual current I = 0, there is a problem with the contact at the source end. In this case, the measurement should be stopped to avoid mismeasurement. Step D: Measure the contact resistance at the detection terminal. After eliminating source-end errors, enable the relay K1004 to introduce the supply voltage V_supply, which is 3.3V. Let point A be the node between the pull-up resistor R_Pullup and the equivalent input resistance R_Input, and point B be the node between the source-end contact resistance R_Source and the equivalent product resistance R_Dut. Measure the voltage V at point A using the analog-to-digital converter U1002. A3V3 The relay K1004 was then disabled, and the voltage V at point A was continued to be measured. ANO Based on the above measurements, the voltage V_B at point B is determined by the following formula: Furthermore, the equivalent product resistance R_Dut: Therefore, the contact resistance R_Sense at the detection end: ; Step E: In the practical application scenario of this invention, contact resistance exceeding 40K Ohm results in unacceptable testing errors. Therefore, if the contact resistance R_Sense at the detection end is less than 40K Ohm, severe contact defects are ruled out, ensuring the accuracy of the four-wire measurement. The setting of the judgment condition for the contact resistance R_Sense at the detection end depends on the application scenario's requirements for testing accuracy. This requirement can be calibrated by measuring a standard resistor and can be determined and modified independently.

[0020] Although the embodiments of the present invention are described with reference to actual solutions, they do not constitute a limitation on the meaning of the present invention. Modifications to the embodiments and combinations with other solutions based on this specification will be obvious to those skilled in the art.

Claims

1. A testing device for measuring the contact resistance of a probe based on a four-wire system, comprising a current source, a supply voltage, and a resistor to be measured, characterized in that: The resistor under test includes a source contact resistor (R_Source), a sensing contact resistor (R_Sense), and an equivalent product resistor (R_Dut). The current source is connected to the equivalent product resistor (R_Dut) via the source contact resistor (R_Source). The equivalent product resistor (R_Dut) is grounded via a current sampling resistor (R_Sampling). The supply voltage is connected to a pull-up resistor (R_Pullup) via a relay (K1004). The pull-up resistor (R_Pullup) is grounded via an equivalent input resistor (R_Input). One end of the sensing contact resistor (R_Sense) is connected to the node of the source contact resistor (R_Source) and the equivalent product resistor (R_Dut), and the other end of the sensing contact resistor (R_Sense) is connected to the node of the pull-up resistor (R_Pullup) and the equivalent input resistor (R_Input).

2. The testing device based on a four-wire probe contact resistance measurement according to claim 1, characterized in that, The current source includes a voltage regulator (U1801), which is connected to a first operational amplifier (U1802), a second operational amplifier (U1805), and a digital-to-analog converter (U1804). The first operational amplifier (U1802), the second operational amplifier (U1805), and the digital-to-analog converter (U1804) are connected in sequence, and the digital-to-analog converter (U1804) is connected to PP_5V.

3. The testing device based on a four-wire probe contact resistance measurement according to claim 2, characterized in that, The resistor under test is connected to an adapter plate, and the resistor under test contacts the adapter plate through a pin block.

4. The testing device based on a four-wire probe contact resistance measurement according to claim 3, characterized in that, The resistor under test is connected to an MCU module, which controls the current source to output a 50uA current, enabling the relay (K1004) switching circuit.

5. The testing device based on a four-wire probe contact resistance measurement according to claim 4, characterized in that, The relay (K1004) is connected to a buffer amplifier (U1001), and the buffer amplifier (U1001) is connected to an analog-to-digital converter (U1002).

6. A detection method comprising a testing apparatus based on a four-wire probe contact resistance measurement device as described in claim 5, characterized in that, The detection method includes the following steps: Step A: Place the object to be tested on the acupoint and clamp it in place using a cylinder; Step B: Set up computer communication, control the cylinder to fix the test object, and the B2B connector of the test object contacts the adapter board through the pin block and is transferred to the test board through the adapter cable. Step C: Eliminate source-end false tests. Control the current source to output a 50uA current via the MCU module, enabling the relay (K1004) to switch the circuit. Measure the voltage Vsampling of the current sampling resistor (R_Sampling) via the analog-to-digital converter (U1002). At this time, the actual current I flowing through the equivalent product resistor (R_Dut) is: Under normal circumstances, the actual current I should be equal to the preset current. In this case, the possibility of mismeasurement at the source end is ruled out, and the test can continue. If they are not equal, there is a serious problem with the contact at the source end. If the actual current I = 0, there is a problem with the contact at the source end. In this case, the measurement should be stopped to avoid mismeasurement. Step D: Measure the contact resistance at the detection terminal. After eliminating source-end errors, enable the relay (K1004) to introduce the supply voltage V_supply, which is 3.3V. Let point A be the node between the pull-up resistor (R_Pullup) and the equivalent input resistance (R_Input), and point B be the node between the source-end contact resistance (R_Source) and the equivalent product resistance (R_Dut). Measure the voltage V at point A using the analog-to-digital converter (U1002). A3V3 The relay (K1004) was then disabled, and the voltage V at point A was continued to be measured. ANO Based on the above measurements, the voltage V_B at point B is determined by the following formula: Furthermore, the equivalent product resistance (R_Dut): Therefore, the contact resistance of the detection end (R_Sense): ； Step E: When the contact resistance (R_Sense) of the detection terminal exceeds 40K ohm, the measurement is stopped to avoid false measurements; when the contact resistance (R_Sense) of the detection terminal is less than 40K ohm, serious contact problems are ruled out, ensuring the accuracy of the four-wire measurement.

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