Weak current testing device and testing path online self-calibration method thereof

Abstract

The invention discloses a weak current testing device and a testing path online self-calibration method thereof, and relates to the field of electronic component testing. The problems that an existing test channel comprises a relay, a PCB wire and other components, multi-channel time-sharing switching causes signal loss, component characteristic offset aggravates signal distortion in long-term use, a real-time calibration mechanism is lacked in the prior art, and dynamic errors cannot be tracked through offline calibration are solved. The device provided by the invention is realized by adopting a three-coaxial cable, wherein the three-coaxial cable comprises an outer skin shielding layer, an inner core and an inner skin signal layer; the inner core is used for transmitting a detected weak current signal, the positive end of the high-voltage power supply is connected with an outer conductor of the three-coaxial cable, the other end of the ammeter is connected with the inner core of the three-coaxial cable and connected with a detected device after passing through one end of the ammeter, the other end of the detected device returns to the negative end of the high-voltage power supply, and the sheath shielding layer is directly grounded. The device is also suitable for small current in a high-voltage environment and eliminates errors in a test process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic component testing, in particular to a weak current testing device and an online self-calibration method for testing paths thereof. BACKGROUND

[0002] In the field of weak current measurement, there are many problems in the prior art that need to be solved. The traditional testing system mostly uses ordinary coaxial cables such as BNC and SMA to transmit signals, and the insulation characteristics thereof are not ideal, which can easily produce significant leakage current under high voltage, for example, the leakage current can reach 350nA under 350V voltage, while the reverse leakage current of the measured diode is only in the order of 1uA, which seriously affects the measurement accuracy, and the insulation performance of the cable fluctuates with time and environment, and the error is further amplified in long-term testing. In addition, there are problems of loss and matching in signal transmission, and impedance mismatching of ordinary cables leads to reflection and attenuation during long-distance transmission, and the DC measurement interface does not effectively compensate the voltage drop of the wire resistance. Although some researches have proposed methods such as amplifier optimization, PCB protection ring, filtering, or explored multiplexing and synchronization technology for multi-channel measurement, and detection devices based on embedded systems, but they have not effectively solved the core problems of leakage current interference under high voltage and dynamic error calibration of the testing path. SUMMARY

[0003] The present application is to overcome the core problems of leakage current interference under high voltage and dynamic error calibration of the testing path in the field of weak current measurement in the prior art, and the testing path includes multiple components such as relays and PCB lines, and the multi-channel time-sharing switching leads to signal loss, and the characteristics of the components deviate during long-term use, which further aggravates signal distortion, and the prior art lacks real-time calibration mechanism, and offline calibration cannot track dynamic error. Therefore, a weak current testing device and an online self-calibration method for testing paths thereof are proposed.

[0004] To solve the above technical problems, the present application is realized by the following technical scheme: Scheme one, the present application proposes a weak current testing device, which is realized by using three coaxial cables, the three coaxial cables include an outer skin shielding layer, an inner core and an inner skin signal layer; the inner core is used for transmitting the measured weak current signal, the positive terminal of the high voltage power supply is connected to the outer conductor of the three coaxial cables, after passing through one end of the ammeter, the other end of the ammeter is connected to the inner core of the three coaxial cables and connected to the measured device, the other end of the measured device returns to the negative terminal of the high voltage power supply, and the outer skin shielding layer is directly grounded.

[0005] Further, a preferred embodiment is provided, wherein the device further comprises the step of configuring an SMA / BNC interface impedance matcher adapted to the three coaxial cables.

[0006] Further, a preferred embodiment is provided, wherein the triaxial cable is implemented by using a large outer diameter coaxial wire, and the large outer diameter is greater than or equal to 8 mm.

[0007] Further, a preferred embodiment is provided, wherein the device further comprises a step of designing a voltage or current adapter by using a four-wire method, and the voltage or current adapter is used to control the wire resistance voltage drop error in a range of less than or equal to 1 mV.

[0008] Scheme II, the method for online self-calibration of a test channel based on the micro-weak current test device according to any one of scheme I, the method comprises the following steps: Step 1, switch the test tool to a calibration state by a relay, and connect a current calibration source, a high-precision ammeter and a high-precision voltmeter, wherein the output current value of the current calibration source is 100 μA±0.1 μA; Step 2, the current calibration source injects a high-precision current signal of 100 μA at the test tool interface, and the ammeter is used to measure at least three times continuously, and the average value is taken as the initial error of the test channel; Step 3, switch the test tool to a measurement state, and apply a reverse bias to the device under test by a direct current power supply, and the voltage value is controlled in a range of 400 V±5 V, so that the device generates a reverse leakage current; Step 4, measure the reverse current of the device under test by using a high-precision ammeter, and record it as ; Step 5, correct the measurement value by using the initial error obtained in step 2 to obtain a calibrated current value , and complete the online self-calibration of the test channel.

[0009] Further, a preferred embodiment is provided, wherein the calculation method of the initial error of the test channel in step 2 is as follows:

[0010] wherein is the multiple measurement values of the ammeter, is the number of measurements.

[0011] Further, a preferred embodiment is provided, wherein the calculation method of the calibrated current value in step 5 is as follows: .

[0012] Scheme III, a terminal device, comprising a memory and a processor, the memory stores a computer program, when the processor runs the computer program stored in the memory, the processor executes the method of scheme II.

[0013] The present application has the advantages that: The weak current testing device and the testing path online self-calibration method thereof adopt three coaxial cables to suppress leakage current, reduce transmission loss by combining interface matching design, and compensate errors in real time through online self-calibration of the testing path.

[0014] The weak current testing device and the testing path online self-calibration method thereof design an online calibration mechanism for errors of the testing path caused by long-term use or environmental changes, acquire initial errors of the path in real time and correct them, effectively offset signal distortion caused by factors such as environment, component aging, and path switching, and ensure the accuracy and stability of long-term testing.

[0015] The application designs a method for dynamically adjusting a threshold value, and improves the adaptive ability and detection effect of the model.

[0016] The application is also applicable to weak current in a high-voltage environment and eliminates errors in the testing process, and ensures the accuracy and stability of measurement results in long-term power-on testing.

[0017] The application is directly used in the field of electronic component testing, mainly for weak current characteristic testing and long-term reliability testing of semiconductor devices, and provides high-precision testing support for performance evaluation and quality detection of electronic components. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The low-loss isolation type three-axis signal transmission structure schematic diagram is described in embodiment nine.

[0019] Figure 2 The low-loss three-coaxial adapter structure schematic diagram for high-voltage and high-frequency synchronous transmission is described in embodiment nine.

[0020] Figure 3 The weak current testing connection schematic diagram achieved by using three coaxial cables is described in embodiment one.

[0021] Figure 4 The weak current testing principle diagram achieved by using three coaxial cables is described in embodiment one.

[0022] Figure 5 The diode reverse current testing tool connection schematic diagram is described in embodiment nine.

[0023] Figure 6 The diode reverse current testing calibration process circuit connection schematic diagram is described in embodiment nine.

[0024] Figure 7The schematic diagram of the diode reverse current test process circuit connection according to the ninth embodiment.

[0025] The three coaxial cables 4 include the outer skin shielding layer 1, the inner core 2 and the inner skin signal layer 3. DETAILED DESCRIPTION

[0026] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments of the present application.

[0027] Embodiment one, the embodiment proposes a weak current test device, the device is realized by three coaxial cables 4, the three coaxial cables 4 include the outer skin shielding layer 1, the inner core 2 and the inner skin signal layer 3; the inner core 2 is used for transmitting the measured weak current signal, the positive terminal of the high-voltage power supply is connected with the outer conductor of the three coaxial cables 4, after passing through one end of the ammeter, the other end of the ammeter is connected with the inner core 2 of the three coaxial cables 4 and connected with the measured device, the other end of the measured device returns to the negative terminal of the high-voltage power supply, and the outer skin shielding layer 1 is directly grounded.

[0028] Embodiment two, the embodiment is a further limitation of the weak current test device according to the first embodiment, and the device further includes the step of configuring the SMA / BNC interface impedance matching device matched with the three coaxial cables 4.

[0029] Embodiment three, the embodiment is a further limitation of the weak current test device according to the first embodiment, and the three coaxial cables 4 are realized by large-diameter coaxial wires, and the size of the large-diameter is ≥8mm.

[0030] Embodiment four, the embodiment is a further limitation of the weak current test device according to the first embodiment, and the device further includes the step of designing a voltage or current adapter by using a four-wire method, and the voltage or current adapter is used to control the wire resistance voltage drop error within the range of ≤1mV.

[0031] Embodiment five, the embodiment proposes a test channel online self-calibration method based on the weak current test device according to any one of the first to fourth embodiments, and the method includes the following steps: Step 1, switch the test tool to the calibration state by the relay, and connect the current calibration source, the high-precision ammeter and the high-precision voltmeter, wherein the output current value of the current calibration source is 100μA±0.1μA; Step 2, the current calibration source injects a high-precision current signal of 100μA at the test tool interface, and the ammeter is used to measure at least three times continuously, and the average value is taken as the initial error of the test channel ; Step 3, switch the test tooling to the measurement state, apply a reverse bias to the device under test by a DC power supply, control the voltage value at 400V±5V, so that the device generates a reverse leakage current; Step 4, measure the reverse current of the device under test by using a high-precision ammeter, denoted as ; Step 5, correct the measurement value by using the initial error of the test path obtained in step 2 , to obtain the calibrated current value , complete the online self-calibration of the test path.

[0032] Embodiment six, this embodiment is a further limitation of the test path online self-calibration method described in embodiment five, the calculation method of the initial error of the test path in step 2 .

[0033] Wherein is the multiple measurement values of the ammeter, is the number of measurements.

[0034] Embodiment seven, this embodiment is a further limitation of the test path online self-calibration method described in embodiment five, the calculation method of the calibrated current value in step 5 . .

[0035] Embodiment eight, this embodiment proposes a terminal device, which includes a memory, a processor, and a computer program stored on the memory and executable on the processor, and the processor executes the program to realize the method described in embodiment five.

[0036] Embodiment nine, see Figures 1 to 7 for a description of this embodiment, which is a further explanation and description of the above-mentioned embodiments: Step 1: selection and connection of three coaxial cables.

[0037] Select a three-coaxial cable 4 including an inner core 2, an inner skin signal layer 3, and an outer skin shielding layer 1, wherein the inner core 2 is used to transmit the weak current signal to be measured, the inner skin signal layer 3 is used as a protective shield, and the outer skin shielding layer 1 is grounded. The connection method is: the positive terminal of the high-voltage power supply is connected to the outer conductor of the three-coaxial cable 4, after passing through one end of the ammeter, the other end of the ammeter is connected to the inner core 2 in the three-coaxial cable 4 and connected to the device under test, the other end of the device under test returns to the negative terminal of the high-voltage power supply, and the outer skin shielding layer is directly grounded.

[0038] Step 2: signal matching and loss control.

[0039] SMA / BNC interface impedance matching device for adapting triaxial cable, impedance range is controlled in 50Ω±2Ω, high frequency signal transmission reflection coefficient is ensured to be ≤-20dB; large outer diameter ≥8mm coaxial cable is adopted, transmission loss is reduced to ≤0.5dB / m; for direct current voltage or current measurement interface, four-wire method is adopted to design voltage or current adapter, wire resistance voltage drop error is controlled to be ≤1mV.

[0040] Step three: test path online calibration 1. Preparing before calibration Before each measurement period, the test tool is switched to the calibration state through the relay to ensure the stability of the path. The current calibration source, high-precision ammeter and high-precision voltmeter are connected, and the output current value of the current calibration source is 100 μA±0.1 μA.

[0041] 2. Obtain initial error The current calibration source injects a high-precision current signal of 100 μA at the interface of the test tool, and the ammeter measures continuously for more than 3 times, and the average value is taken as the initial error of the test path , that is

[0042] Wherein is the multiple measurement value of the ammeter, is the number of measurements.

[0043] Step four: actual measurement of weak current and error correction 1. Apply bias voltage to the measured device The test tool is switched to the measurement state, and the reverse bias voltage is applied to the measured device through the DC power supply, and the voltage value is controlled in 400V±5V, so that the device generates a reverse leakage current.

[0044] 2. Measure the current signal The reverse current of the measured device is measured by using a high-precision current, which is recorded as .

[0045] 3. Error correction The initial error obtained in step two is used The measurement value is corrected to obtain the accurate current value , and the formula is: .

[0046] The above steps can ensure that the current measurement error is ≤±1% in long-term power-on test by suppressing the leakage current through the triaxial cable and combining the online calibration mechanism.

[0047] The present application is based on the triaxial cable for weak current test experiment verification, such as Figure 3As shown, the high-voltage power supply positive terminal is connected to the outer conductor of the three coaxial cable, then connected to one end of the ammeter, and connected to the inner core of the three coaxial cable through the other end of the ammeter, connected to the device under test, and finally returned to the power supply negative terminal, and the outer shield layer of the three coaxial cable is connected to the ground, and the principle is as shown in Figure 4 .

[0048] The selected fluoroplastic cable insulation material has a resistance Rleak=1GΩ, in the case of using a common cable without a protective layer, the ammeter shows the sum of the current on the device and the leakage current on the cable, assuming that the supply voltage is 350V, then the leakage current Ileak=350nA, and the reverse leakage current of the diode is in the order of 1μA, therefore the cable leakage has a great influence on the measurement of the reverse leakage current of the diode; and the three coaxial cable connection method with a protective layer is equivalent to connecting a parasitic resistance path in parallel across the high and low ends of the ammeter, and the voltage drop Vd of the ammeter is much smaller than the power supply voltage, so in the case of the same insulation resistance, the measured value on the ammeter is basically consistent with the current value on the actual device, ensuring the accuracy of the test.

[0049] The present application takes the reverse current test process of the fast recovery diode as an example to verify the current test path calibration method, and the schematic diagram is as shown in Figure 5 .

[0050] Before the current test, in order to reduce the influence of the environment, test path and other factors on the current test result during the test, before each test starts, the test tool is first switched to the calibration state to obtain the initial error of the current test path, and the connection structure is as shown in Figure 6 .

[0051] The relay is used to bypass the DC voltage source outside the path, a 100μA high-precision current signal is connected to the test tool interface by using the current calibration source, and then the current value of the current signal is tested by using the ammeter as the initial error of the test path ; then the test tool is switched to the reverse current test state, and the connection diagram is as shown in Figure 7 .

[0052] During the reverse current test of the fast recovery diode, a reverse bias is first provided for the diode under test by using a DC current source to generate a reverse leakage current inside, the voltmeter in the test system is controlled to make the reverse voltage of the diode accurate at 400V, and then the reverse current is measured by using the ammeter ; then the measured current value is subtracted from the initial error , that is, the accurate current test value can be obtained, and the above operation can effectively reduce the error influence during the test.

[0053] Those skilled in the art can understand that the above description is only the preferred embodiment of the present application, and the features described in various embodiments of the present disclosure and / or claims can be combined or combined, even if such combination or combination is not explicitly described in the present disclosure. It is not intended to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacement for part of the technical features, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0054] Although preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application. Obviously, those skilled in the art can make various modifications and changes to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and changes of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and changes.

Claims

1. A weak current testing device, characterized in that, The device is implemented using a triaxial cable (4), which includes an outer shielding layer (1), an inner core (2), and an inner signal layer (3). The inner core (2) is used to transmit the weak current signal to be measured. The positive end of the high-voltage power supply is connected to the outer conductor of the triaxial cable (4), and after passing through one end of the ammeter, the other end of the ammeter is connected to the inner core (2) of the triaxial cable (4) and connected to the device under test. The other end of the device under test returns to the negative end of the high-voltage power supply, and the outer shielding layer (1) is directly grounded.

2. The weak current testing device according to claim 1, characterized in that, The device also includes the step of configuring an SMA / BNC interface impedance matching device adapted to a triaxial cable (4).

3. The weak current testing device according to claim 1, characterized in that, The three coaxial cables (4) are implemented using large-diameter coaxial wires, and the outer diameter of the large-diameter wires is ≥8mm.

4. The weak current testing device according to claim 1, characterized in that, The device further includes a step of designing a voltage or current adapter using a four-wire method, wherein the voltage or current adapter is used to control the voltage drop error of the wire resistance within the range of ≤1mV.

5. A method for online self-calibration of a test path based on a weak current testing device according to any one of claims 1-4, characterized in that, The method includes the following steps: Step 1: Switch the test fixture to calibration mode via relay, and connect the current calibration source, high-precision ammeter and high-precision voltmeter. The output current value of the current calibration source is 100μA±0.1μA. Step 2: Inject a high-precision 100μA current signal into the test fixture interface using the current calibration source. Measure the current signal continuously at least three times using an ammeter, and take the average value as the initial error of the test path. ; Step 3: Switch the test fixture to the measurement state, apply a reverse bias voltage to the device under test through the DC power supply, and control the voltage value at 400V±5V to make the device generate reverse leakage current. Step 4: Measure the reverse current of the device under test using a high-precision ammeter, and record it as... ; Step 5: Use the initial error obtained in Step 2. The measured value is corrected to obtain the calibrated current value. Complete the online self-calibration of the test path.

6. The online self-calibration method for test pathways according to claim 5, characterized in that, Initial error of the test path in step 2 The calculation method is as follows: in These are multiple measurements taken by the ammeter. For the number of times measured.

7. The online self-calibration method for test pathways according to claim 5, characterized in that, The calibrated current value in step 5 The calculation method is as follows: .

8. A terminal device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the program to implement the method of claim 5.

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