CN210604879U - Voltage current source test circuit - Google Patents
Voltage current source test circuit Download PDFInfo
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- CN210604879U CN210604879U CN201921332020.3U CN201921332020U CN210604879U CN 210604879 U CN210604879 U CN 210604879U CN 201921332020 U CN201921332020 U CN 201921332020U CN 210604879 U CN210604879 U CN 210604879U
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Abstract
The utility model provides a voltage current source test circuit, including voltage current source, this voltage current source includes the control unit, exports power amplifier circuit, current measurement circuit and voltage measurement circuit, and the four-wire kelvin circuit of connecting thereof, voltage current source still includes: and the two differential voltage measuring circuits are used for collecting the voltages on the voltage line and the current line of the four-wire Kelvin circuit and outputting differential voltage to the control unit through differential operation. The utility model discloses on the basis of traditional four-wire kelvin wiring, realize extra differential voltage measurement through increasing two way voltage signal measurement circuit to the pressure drop on the measuring current line, thereby the dynamic equivalent contact resistance on the current line reads back when realizing the test at every turn.
Description
Technical Field
The invention relates to the technical field of integrated circuit testing, in particular to a voltage current source testing circuit.
Background
In integrated circuit testing, a voltage current source (hereinafter referred to as a VI source) is required for signal excitation and voltage current measurement of a Device Under Test (hereinafter referred to as a DUT).
In order to improve the accuracy of output voltage and test voltage, the conventional VI source adopts a four-wire Kelvin (Kelvin) connection mode, which is a High-end current line (FH, Force High), a High-end voltage line (SH, Sense High), a Low-end current line (FL, Force Low), and a Low-end voltage line (SL, Sense Low). Wherein current is output (or input) from a High side current line (FH, Force High) and back-flowed (or output) from a Low side current line (FL, Force Low). The rf and the Rfl are equivalent resistances generated in the FH and FL transmission links, respectively, and a current flows through the rf and the Rfl, so that a certain voltage drop is generated in the current transmission link.
The voltage measurement is taken as the difference between the High side voltage line (SH, Sense High) and the Low side voltage line (SL, Sense Low) to be the voltage difference on the DUT. The SH end and the SL end are internally provided with high-impedance input ends, and the voltage of the near end and the far end of the signal is the same. Wherein Rsh and Rsl are equivalent resistances of the transmission link at the SH end and the SL end, respectively. Because the SH end and the SL end are internally provided with high-impedance input ends, the good contact between the Rsh and the Rsl is in the magnitude below ohm, and the good contact is in the magnitude above megaohm when the contact is poor. When the contact is good, compared with the high impedance with the magnitude of more than kilomega inside the SH end and the SL end, the high impedance can be ignored, so that the pressure difference between the Rsh and the Rsl is very small and can be ignored.
Fig. 1 shows a conventional VI source architecture, which includes a SH terminal and an SL terminal connected to a differential operational amplifier OP2 in common and then connected to a CONTROL terminal, a voltage follower OP1 connected in series to the SH terminal, a voltage follower OP5 connected in series to the SL terminal, a span resistor Ri connected in series to the FL terminal, a current differential measurement OP4 connected in parallel to both terminals of the span resistor Ri, and an output power amplifier OP3 connected in series between the CONTROL terminal and the FH terminal. When the VI source framework works, the CONTROL sets the VI source mode state corresponding to the VI source mode according to the needed VI source mode, drives the output power amplifier OP3 to work, outputs the VI source mode from the FH end, carries out voltage following measurement on the voltage follower OP1 and the voltage follower OP5 to respectively obtain Vsh and Vsl, obtains a Vmeter signal through the differential operational amplifier OP2, and sends the Vmeter signal into the CONTROL for feedback and measurement; meanwhile, after a signal output from the FH end flows to the FL end through the DUT, the signal flows to the GND end through the Ri finally; and the differential amplifier OP4 measures the voltage at two ends of Ri to obtain an Imeter signal, and the Imeter signal is sent to the CONTROL for feedback and measurement.
As shown in fig. 2, when a conventional VI source architecture is used to stimulate a signal or measure voltage and current at a DUT, a four-wire kelvin connection is also typically used to subtract out the voltage difference produced by the current at the equivalent resistance of the current line, thereby accurately measuring the voltage difference across the DUT.
However, in practical applications, the output from the VI source can reach the DUT through cables, various adapter sockets, gold fingers, or probes, and each link has a transmission resistance or a contact resistance, which causes different voltage drops. The power transmission resistor on the fixed connection circuit such as a cable is relatively stable, and the voltage drop on the power transmission resistor under a certain current is relatively fixed. In the case of a socket, particularly a gold finger or a probe, which has electrical connection due to pressure, the contact resistance is related to the contact pressure, and also related to the cleanliness and flatness of the contact surface.
Particularly, when the golden finger or the probe is used, the golden finger or the probe is respectively contacted with a plurality of devices for a plurality of times, so that the problems of reduction of the cleanliness of a contact surface, unevenness of the contact surface or reduction of contact pressure due to use abrasion exist; this problem causes the test contact resistance to become abnormally large, resulting in test abnormality. Therefore, the possible poor contact needs to be detected, once the poor contact is found, the surface of the golden finger or the probe needs to be cleaned in time, and if the surface is still abnormal, the contact pressure needs to be adjusted; if the abnormality still occurs, the gold finger or probe needs to be replaced to ensure good contact.
For the contact detection of a golden finger or a probe, the following methods are often adopted:
one test method, as shown in FIG. 3, uses a two-wire connection using a diode inside the DUT as a transmission loop to detect the equivalent contact resistance condition of a diode in series with a gold finger or probe, where the diode is typically a DUT pin to power terminal or a guard diode from one power terminal to another power terminal. The test method is commonly used for contact detection of digital devices, the test method can only uniformly measure equivalent contact resistance of two contact ends, can not measure Rhc or Rlc respectively, and is influenced by different batch voltage drops of device diodes, the precision of the equivalent contact resistance is not high, and the test method can usually detect contact resistance of about one hundred ohms under the constant current of 1mA of a VI source.
In another testing method shown in fig. 4 and 5, two ends (high end and low end) of the DUT are respectively connected to two output ends of the VI source, so that the contact resistances between the two ends of the DUT and the gold finger or the probe are respectively measured. The test method can only carry out unified measurement on the high-end Rfhc and Rshc or the low-end Rflc and Rslc, although the batch error caused by the diodes is reduced compared with the two-wire connection mode shown in the figure 3, and the measurement result is more accurate. However, this measurement method cannot accurately measure the equivalent contact resistances on the current lines, i.e., rfc and Rflc, which have a great influence on the voltage drop of the current lines in a high-current test, and these equivalent contact resistances may vary during each test. In each test of the VI source, if the equivalent contact resistance values can be accurately measured, whether the contact link has reliability risks (such as contact resistance change caused by oxidation, abrasion, impurities and the like of a golden finger) can be quickly judged, so that an early alarm is given according to test data, and equipment maintenance is carried out to reduce later-stage greater quality risks, such as: the problems of needle burning, device burning, VI source burning and the like are more serious especially in the tests of high power and large current.
Disclosure of Invention
In view of the above, the present invention provides a voltage current source test circuit and a test method thereof, which implement additional differential voltage measurement by adding two voltage signal measurement circuits on the basis of the traditional four-wire kelvin connection to measure the voltage drop on the current wire, thereby implementing dynamic equivalent contact resistance on the read-back current wire during each test. On the premise of not influencing the original characteristics of the VI source, the invention can also realize the measurement of extra differential voltage in the four-wire Kelvin circuit and the accurate measurement of equivalent contact resistance, thereby quickly judging whether the contact link has reliability risk or not and preventing the problem that the device is easily damaged during large-current test due to the reduction of the reliability of the contact link.
The technical scheme adopted by the invention is that the voltage current source test circuit comprises a voltage current source, wherein the voltage current source comprises a control unit, an output power amplification circuit, a current measurement circuit, a voltage measurement circuit and a four-wire Kelvin circuit connected with the voltage current source, and the voltage current source also comprises:
and the two differential voltage measuring circuits are used for collecting the voltages on the voltage line and the current line of the four-wire Kelvin circuit and outputting differential voltage to the control unit through differential operation.
By the above, on the basis of the original voltage and current source architecture, a differential voltage measurement circuit is added, when a voltage and current source measures a device to be tested, the device to be tested can be contacted through a golden finger or a probe, equivalent contact resistance can be generated, at the moment, voltages on a voltage line and a current line which are connected with the device to be tested through a four-wire Kelvin circuit are respectively collected through the differential voltage measurement circuit, differential operation is carried out, the voltages are sent to a control unit, and the control unit can calculate the equivalent contact resistance generated by the contact of the golden finger or the probe and the device to be tested according to the differential voltage and the known current obtained by the differential operation.
Wherein the differential voltage measurement circuit comprises a first differential operational amplifier and a voltage follower;
the input end of the voltage follower is connected with a current line of the four-wire Kelvin circuit, the on-line voltage of the voltage follower is collected, and the output end of the voltage follower is connected with one input end of the first differential operational amplifier;
the other input end of the first differential operational amplifier is connected with a voltage line of the four-wire Kelvin circuit, the voltage on the line of the first differential operational amplifier is collected, and the output end of the first differential operational amplifier is connected with the control unit;
the first differential operational amplifier performs differential operation on the voltages of the two input ends and outputs differential voltage to the control unit.
Therefore, the differential operation of the voltages at the two input ends can be realized through the differential operational amplifier and is fed back to the control unit.
Wherein the four-wire Kelvin circuit comprises:
one end of the high-end current line is connected with the control unit, the other end of the high-end current line is connected with the tested device, and the high-end current line is also connected with an output power amplifier in series;
one end of the low-end current line is connected with the tested device, the other end of the low-end current line is grounded, and a measuring range resistor is connected to the low-end current line in series;
the two input ends of the second differential operational amplifier collect the current at the two ends of the range resistor, and differential operation is carried out to output differential current to the control unit;
the high-end voltage line is used for collecting the voltage on the high-end current line and outputting the voltage to the third differential operational amplifier;
the low-end voltage line is used for collecting the voltage on the low-end current line and outputting the voltage to the third differential operational amplifier;
and the third differential operational amplifier outputs differential voltage of the high-low end current line to the control unit after differential operation.
Preferably, the two differential voltage measurement circuits respectively measure a differential voltage between a high-side current line and a high-side voltage line of the four-wire kelvin circuit and a differential voltage between a low-side current line and a low-side voltage line of the four-wire kelvin circuit.
Therefore, two differential voltage measuring circuits are arranged, so that the equivalent contact resistance of the high end and the low end of the four-wire Kelvin can be measured simultaneously, and the two equivalent contact resistances do not influence each other.
Wherein the voltage current source is connected with the device under test through the four-wire Kelvin circuit and forms a loop with an auxiliary device in the device under test.
Wherein the auxiliary device comprises a diode.
In this way, by using an auxiliary device such as a diode or other conductive device in the device under test, a loop can be formed with the four-wire kelvin circuit and the voltage current source, and the subsequent measurement of the differential voltage can be performed.
The invention also provides a voltage and current source testing method based on the testing circuit, which comprises the following steps:
A. a current line of the voltage current source is set by the control unit to output a constant current;
B. respectively collecting the voltage on a voltage line and the voltage on a current line of the four-wire Kelvin circuit through a differential voltage measuring circuit, and carrying out differential operation;
C. and acquiring the differential voltage output by the differential voltage measuring circuit through a control unit, and calculating the equivalent contact resistance generated by the connection of the current line and the tested device according to the current value measured on the range resistor connected with the low-end current line in series.
By last, based on above-mentioned voltage current source, set up the mode that the control unit was set for the output constant current with voltage current source through setting up the control unit, make the constant current of output pass through high-end current line, device under test and low-end current line, form the return circuit, the voltage feedback that the voltage line measured is to differential voltage measurement circuit, still gather the voltage that produces on the current line simultaneously, can calculate the current line because of the produced voltage drop of equivalent contact resistance through differential operation, through measuring the current value on the range resistance of low-end current line series connection, then according to ohm's law, under the condition of known voltage and electric current, can calculate the size of equivalent contact resistance.
Wherein, step A is preceded by the steps of:
the voltage current source is connected with the device to be tested through a four-wire Kelvin circuit and forms a loop with an auxiliary device in the device to be tested.
Thus, a complete loop is formed by connecting the high and low sides of a four-wire kelvin circuit to auxiliary devices within the device under test, respectively.
In a further improvement, before the step a, the method further comprises the steps of:
and short-circuiting a voltage line and a current line of the four-wire Kelvin circuit, and measuring the on-line equivalent resistance of the voltage line and the current line.
By last, through the voltage line and the electric current line short circuit with high-end to and the voltage line and the electric current line short circuit of low-end, measure its on-line equivalent resistance, judge whether it is in the regulation within range, if in the scope, can carry out the measurement of next step's equivalent contact resistance, if not in the scope, then judge golden finger or probe contact failure, need change.
And when the error of the current value measured on the range resistor connected with the constant current value and the low-end current line in series exceeds a limited range, judging that the current line is in poor contact with the tested device.
From the above, normally, since the current line and the device under test are connected in series, the current value measured by the measuring resistor connected in series with the low-end current line should be the same as the output constant current value, and at this time, the equivalent contact resistance can be calculated according to the measured current value and the differential voltage, but when the current line and the device under test are in poor contact, an error is generated between the measured current value on the measuring resistor and the output constant current value, and when the error range is large and exceeds a limited range, for example, 5%, the poor contact between the current line and the device under test can be determined.
In summary, compared with the existing voltage current source structure and test circuit, the invention has the following advantages:
the differential voltage measurement circuit added on the high-low end line can realize additional differential voltage measurement;
the added differential voltage measuring circuit can simultaneously measure differential voltage on high-low-end lines;
the added differential voltage measurement circuit does not influence the original characteristics of the voltage current source, namely the voltage current source can still simultaneously measure differential voltage when in normal FV, FI, CV and CI.
Drawings
FIG. 1 is a circuit schematic of a conventional voltage current source;
FIG. 2 is a schematic diagram of a conventional voltage current source with a four wire Kelvin connection with a DUT;
FIG. 3 is a prior art circuit diagram of a contact resistance of a DUT contact golden finger or probe;
FIG. 4 is a circuit diagram of another prior art method for testing the contact resistance of a DUT high-end contact gold finger or probe;
FIG. 5 is a circuit diagram of another prior art method for testing the contact resistance of a DUT low-end contact gold finger or probe;
FIG. 6 is a schematic circuit diagram of a voltage current source according to the present invention;
FIG. 7 is a schematic circuit diagram of a first embodiment of a voltage-current source for measuring equivalent contact resistance according to the present invention;
FIG. 8 is a schematic circuit diagram of a second embodiment of the present invention for measuring the equivalent contact resistance by the voltage current source.
Detailed Description
A detailed description will be given below of a specific embodiment of the voltage-current source test circuit according to the present invention with reference to fig. 6 to 8.
As shown in FIG. 6, the present invention provides a new voltage current source (hereafter referred to as VI source), which adds two differential voltage measurement circuits on the basis of the original VI source four-wire Kelvin connection mode to measure the differential voltage between the VI source and the DUT, and then calculates the equivalent contact resistance generated when the driving circuit is connected to the device under test according to the known current.
Specifically, the original architecture of the VI source includes a CONTROL, an output power amplifier circuit, a current measuring circuit, a voltage measuring circuit, and a four-wire kelvin circuit connected thereto, where the four-wire kelvin circuit is a High-end current line (FH, ForceHigh), a High-end voltage line (SH, Sense High), a Low-end current line (FL, Force Low), and a Low-end voltage line (SL, Sense Low), respectively;
when the VI source framework works, the CONTROL sets the VI source mode to a corresponding VI source mode state according to the needed VI source mode, drives the output power amplifier OP3 to work, outputs current from the FH end, carries out voltage following measurement on the voltage follower OP1 and the voltage follower OP5 to respectively obtain Vsh and Vsl, obtains a Vmeter signal through the differential operational amplifier OP2, and sends the Vmeter signal to the CONTROL for feedback and measurement; meanwhile, after a signal output from the FH end flows to the FL end through the DUT, the signal flows to the GND end through the range resistor Ri; the differential amplifier OP4 measures the voltage at two ends of the range resistor Ri to obtain an Imeter signal, and the Imeter signal is sent to the CONTROL for feedback and measurement;
on the basis of the original VI source framework, two differential voltage measuring circuits are additionally arranged and are respectively used for measuring the differential voltage of an FH end and an SH end and the differential voltage of an FL end and an SL end;
the differential voltage measuring circuit connected to the FH end and the SH end comprises a differential operational amplifier OP8 and a voltage follower OP6 connected to the SHx end, wherein the input end of the differential operational amplifier OP8 receives the voltage of the SHx end and the voltage of the SH end respectively, during operation, the Vshx voltage measured at the SHx end is fed into the positive input end of the differential operational amplifier OP8 through the voltage follower OP6, the Vsh voltage at the SH end is fed into the negative input end of the differential operational amplifier OP8 through the voltage follower OP1, the Vshx voltage and the Vsh voltage are subjected to differential operation through the differential operational amplifier OP8 to obtain a differential voltage Vdiff _ High, and the differential voltage Vdiff _ High is fed into a CONTROL for measurement;
similarly, the differential voltage measurement circuit connected to the FL terminal and the SL terminal includes a differential operational amplifier OP9 and a voltage follower OP7 connected to the SLx terminal, the input terminal of the differential operational amplifier OP9 receives the voltage of the SLx terminal and the voltage of the SL terminal, respectively, during operation, the Vslx voltage measured at the SLx terminal is sent to the negative input terminal of the differential operational amplifier OP9 through the voltage follower OP7, the Vsl voltage at the SL terminal is sent to the positive input terminal of the differential operational amplifier OP9 through the voltage follower OP5, the Vslx voltage and the Vsl voltage are subjected to differential operation by the differential operational amplifier OP9 to obtain a differential voltage Vdiff _ Low, and the differential voltage Vdiff _ Low is sent to CONTROL for measurement;
as shown in fig. 7, in an embodiment of the present invention, the equivalent contact resistance of the contact end of the device under test is measured by using the improved VI source, but before the DUT is connected by using the four-wire kelvin connection method, it is first detected whether the sum of Rfhc and Rshc and the sum of Rflc and Rslc are within a certain range by shorting FH line and SH line and shorting FL line and SL line, respectively, and if so, the DUT is connected by using the four-wire kelvin connection method, the SHx end is connected to one end of the FH line in the four-wire kelvin near the DUT, the SLx end is connected to one end of the FL line in the four-wire kelvin near the DUT, and then the equivalent contact resistance values of Rfhc and Rflc are detected by using a differential voltage measurement circuit in cooperation with a device such as an auxiliary device diode of the DUT;
the following description of the equivalent contact resistance test performed by taking the auxiliary device diode of the DUT as an example shows the specific working principle as follows:
the VI source is controlled by a CONTROL, a fixed current I is constantly output from the FL end, the current I flows back to the FH end after passing through the FL line, the DUT line and the FH line which are connected on the periphery of the VI source, the SHx end is connected with one end, close to the DUT, of the FH line through a peripheral lead wire, the voltage on the FH line can be measured, the current I passes through a voltage follower OP6 on a differential voltage measurement circuit and then is fed back to a positive input end of a differential operational amplifier OP8, the sensing voltage on the SH line passes through a voltage follower OP1 in the VI source and then is fed back to a negative input end of the differential operational amplifier OP8, after differential operation, the differential operational amplifier OP8 outputs a differential voltage Vdiff _ High, because the SH end and the SHx end are internally provided with High-impedance input ends, the voltage of the near end and the far end of the signal is the same, and the resistances Rsh, Rshc and Rshx can be ignored, so the equivalent contact resistance generated on the Vdiff _ High line is the FH voltage generated by the R, then measuring the current value of a range resistor Ri connected in series on a low-end current line FL, and calculating the value of Vdiff _ High and the current value of the range resistor Ri according to ohm's law, namely calculating the value of Rfhc, wherein under the normal condition, the current value of the range resistor Ri is equal to the output fixed current I, namely Rfhc is Vdiff _ High/I;
similarly, the SLx terminal may also measure the voltage on the FL line, and the measured voltage passes through a voltage follower OP7 on the differential voltage measurement circuit and then is fed back to the negative input terminal of the differential operational amplifier OP9, the sensed voltage on the SL line passes through a voltage follower OP5 inside the VI source and then is fed back to the positive input terminal of the differential operational amplifier OP9, after the differential operation, the differential operational amplifier OP9 outputs a differential voltage Vdiff _ Low, and according to ohm's law, the equivalent contact resistance Rflc generated on the FL line can be calculated, that is, Rflc is Vdiff _ Low/I;
it should be noted that, normally, the current value of the range resistor Ri connected in series on the low-end current line FL is equal to the fixed current I output by the high-end current line FL, however, when the current line (gold finger or probe) and the device under test are in poor contact, the current value of the range resistor Ri and the fixed current I have an error, and when the error range exceeds a limited range (for example, 5%), the current line is determined to be in poor contact, and the equivalent contact resistance generated when the poor contact is generated can be calculated according to the current value of the range resistor Ri and the differential voltage.
In another embodiment of the present invention, as shown in fig. 8, when there are multiple current lines connected in parallel between the VI source and the DUT, the differential voltage measurement circuit can measure the voltage by providing a relay on each current line and switching to the corresponding current line through the relay, and the measurement principle is the same as that of the above embodiment;
by turning on the relays Ksh1, Kfh1, Ksl1, Kfl1, the equivalent contact resistance values of Rfhc1 and Rflc1 can be measured, respectively. Similarly, when the relays Ksh2, Kfh2, Ksl2 and Kfl2 are turned on, the equivalent contact resistance values of Rfhc2 and Rflc2 can be measured, and the equivalent contact resistance values of Rfhcn and Rflcn can also be measured.
The present embodiment is consistent with the principle of the above embodiments, and the specific measurement process and principle are not described again, but the difference lies in that when a plurality of current lines are connected between the VI source and the device under test, due to the adoption of the switch switching, the accurate measurement can be performed by switching to any two concerned contact resistance points, thereby realizing a more flexible measurement mode.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (6)
1. A voltage current source test circuit, includes voltage current source, and this voltage current source includes the control unit, exports power amplifier circuit, current measurement circuit and voltage measurement circuit, and the four-wire Kelvin circuit that its is connected, its characterized in that, voltage current source still includes:
and the two differential voltage measuring circuits are used for respectively collecting the voltages on the voltage line and the current line of the four-wire Kelvin circuit and outputting differential voltage to the control unit through differential operation.
2. The test circuit of claim 1, wherein the differential voltage measurement circuit comprises a first differential operational amplifier and a voltage follower;
the input end of the voltage follower is connected with a current line of the four-wire Kelvin circuit, the on-line voltage of the voltage follower is collected, and the output end of the voltage follower is connected with one input end of the first differential operational amplifier;
the other input end of the first differential operational amplifier is connected with a voltage line of the four-wire Kelvin circuit, the voltage on the line of the first differential operational amplifier is collected, and the output end of the first differential operational amplifier is connected with the control unit;
the first differential operational amplifier performs differential operation on the voltages of the two input ends and outputs differential voltage to the control unit.
3. The test circuit of claim 1, wherein the four-wire kelvin circuit comprises:
one end of the high-end current line is connected with the control unit, the other end of the high-end current line is connected with the tested device, and the high-end current line is also connected with an output power amplifier in series;
one end of the low-end current line is connected with the tested device, the other end of the low-end current line is grounded, and a measuring range resistor is connected to the low-end current line in series;
the two input ends of the second differential operational amplifier collect the current at the two ends of the range resistor, and differential operation is carried out to output differential current to the control unit;
the high-end voltage line is used for collecting the voltage on the high-end current line and outputting the voltage to the third differential operational amplifier;
the low-end voltage line is used for collecting the voltage on the low-end current line and outputting the voltage to the third differential operational amplifier;
and the third differential operational amplifier outputs differential voltage of the high-low end current line to the control unit after differential operation.
4. The test circuit of claim 1, wherein the two differential voltage measurement circuits measure a differential voltage of a high side current line and a high side voltage line and a differential voltage of a low side current line and a low side voltage line of the four-wire kelvin circuit, respectively.
5. The test circuit of claim 1, wherein the voltage current source connects the device under test through the four-wire kelvin circuit in a loop with an auxiliary device within the device under test.
6. The test circuit of claim 5, wherein the auxiliary device comprises a diode.
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| CN114236243A (en) * | 2021-11-19 | 2022-03-25 | 湖南省拓联精密科技有限公司 | Resistance measuring method, device, equipment and storage medium |
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| CN114236243A (en) * | 2021-11-19 | 2022-03-25 | 湖南省拓联精密科技有限公司 | Resistance measuring method, device, equipment and storage medium |
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