Resistance measuring circuit and resistance value measuring device

Abstract

The invention discloses a resistance measuring circuit and a resistance value measuring device.The resistance measuring circuit comprises a power input end, a resistance measuring channel, a first reference resistance switching circuit, a current switching circuit and a control circuit, and the first current transmission end of the resistance measuring channel is connected with the power input end; the first end and the second end of the resistance measurement channel are respectively connected to two ends of a to-be-measured resistor; the first end of the first reference resistance switching circuit is connected with the second current transmission end of the resistance measurement channel, and the second end of the first reference resistance switching circuit is connected with the grounding end; the first end of the current switching circuit is connected with the second current transmission end of the resistance measurement channel, and the second end of the current switching circuit is connected with the grounding end; the invention aims to improve the measurement range of the resistance measurement device.

Description

Resistance measuring circuit and resistance measuring device Technical Field

[0001] This invention relates to the field of resistance measurement technology, and in particular to a resistance measurement circuit and a resistance value measurement device. Background Technology

[0002] In electronic testing and quality inspection, resistance measurement needs to cover a wide range from micro-ohms to mega-ohms. However, current resistance measuring devices can usually only measure one of the micro-ohm or mega-ohm ranges. Therefore, users need to use both micro-ohm and mega-ohm measuring devices to measure resistance, which is quite inconvenient. Summary of the Invention

[0003] The main objective of this invention is to provide a resistance measurement circuit and a resistance measurement device, which aims to improve the measurement range of the resistance measurement device.

[0004] To achieve the above objectives, the present invention proposes a resistance measurement circuit, comprising a power input terminal, a resistance measurement channel, a first reference resistor switching circuit, a current switching circuit, and a control circuit. The first current transmission terminal of the resistance measurement channel is connected to the power input terminal. The first and second terminals of the resistance measurement channel are respectively used to connect to the two ends of the resistor under test. The resistance measurement channel guides the current input through the first current transmission terminal into the resistor under test and guides the current of the resistor under test to flow out through the second current transmission terminal of the resistance measurement channel. The first terminal of the first reference resistor switching circuit is connected to the second current transmission terminal of the resistance measurement channel, and the second terminal of the first reference resistor switching circuit is connected to a ground terminal. The first terminal of the current switching circuit is connected to the power input terminal. The second current transmission terminal of the resistance measurement channel is connected, and the second terminal of the current switching circuit is connected to the ground terminal. The current switching circuit is used to switch the current flowing through the resistance measurement channel. The control circuit is used to obtain the resistance value range of the resistor under test, and when the resistance value range of the resistor under test is not less than a preset resistance value, it controls the first reference resistance switching circuit to switch its own resistance value according to the resistance value range of the resistor under test, so that the resistance value of the first reference resistance switching circuit and the resistance value range of the resistor under test are in the same order of magnitude. The control circuit is also used to control the current switching circuit to switch the current flowing through the resistance measurement channel according to the resistance value range of the resistor under test when the resistance value range of the resistor under test is less than a preset resistance value, so that the voltage of the resistor under test is within a preset voltage range.

[0005] In one embodiment, the first reference resistor switching circuit includes: a plurality of first reference resistors and a plurality of first switching components. The first ends of the plurality of first reference resistors are all connected to the second current transmission end of the resistance measurement channel. The second ends of the plurality of first reference resistors are connected to the first ends of the plurality of first switching components in a one-to-one correspondence. The first ends of the plurality of reference resistors are all connected to a ground end. The controlled end of the first switching component is electrically connected to the control circuit.

[0006] In one embodiment, the current switching circuit includes: a constant current source circuit and a second reference resistor switching circuit. A first terminal of the constant current source circuit is connected to a second current transmission terminal of the resistance measurement channel. A second terminal of the constant current source circuit is connected to a first terminal of the second reference resistor switching circuit. A second terminal of the second reference resistor switching circuit is connected to a ground terminal. The first and second terminals of the second reference resistor switching circuit are also connected to a controlled terminal of the constant current source circuit. The controlled terminal of the second reference resistor switching circuit is electrically connected to a control circuit. The constant current source circuit is used to switch the current flowing through the resistance measurement channel based on the voltage of the second reference resistor switching circuit. The control circuit is used to control the second reference resistor switching circuit to switch the resistance value according to the resistance range of the resistor under test, thereby controlling the constant current source circuit to switch the current flowing through the resistance measurement channel, so that the voltage of the resistor under test is within a preset voltage range.

[0007] In one embodiment, the constant current source circuit includes: an amplifier circuit, the first input terminal of which is connected to the first terminal of the second reference resistor switching circuit, and the second input terminal of which is connected to the second terminal of the second reference resistor switching circuit; a comparator circuit, the output terminal of which is connected to the first input terminal of the comparator circuit, and the second input terminal of the comparator circuit is used to connect to a first voltage; and a switching transistor circuit, the output terminal of which is connected to the controlled terminal of the switching transistor circuit, the first terminal of which is connected to the second current transmission terminal of the resistance measurement channel, and the second terminal of which is connected to the second terminal of the second reference resistor switching circuit.

[0008] In one embodiment, the second reference resistor switching circuit includes: a plurality of second reference resistors and a plurality of second switching components. The first ends of the plurality of second reference resistors are all connected to the second end of the constant current source circuit. The second ends of the plurality of second reference resistors are connected to the first ends of the plurality of second switching components in a one-to-one correspondence. The first ends and second ends of the plurality of second reference resistors are also electrically connected to the constant current source circuit. The second end of the second switching component is connected to the ground terminal. The controlled end of the second switching component is electrically connected to the control circuit.

[0009] In one embodiment, the resistance measurement circuit further includes: a first polarity switching circuit and a second polarity switching circuit. A first terminal of the first polarity switching circuit is connected to the power input terminal, a second terminal of the first polarity switching circuit is connected to a ground terminal, and a third terminal of the first polarity switching circuit is connected to a first current transmission terminal of the resistance measurement channel. A first terminal of the second polarity switching circuit is connected to the power input terminal, a second terminal of the second polarity switching circuit is connected to a ground terminal, and a third terminal of the second polarity switching circuit is connected to a second terminal of the first reference resistance switching circuit. Both the controlled terminals of the first and second polarity switching circuits are electrically connected to the control circuit. The first polarity switching circuit controls the connection of the resistance measurement channel to one of the power input terminal and the ground terminal, and the second polarity switching circuit controls the connection of the second terminal of the first reference resistance switching circuit to the other of the power input terminal and the ground terminal. The resistance measurement channel also guides the current input through the second current transmission terminal into the resistor under test, and guides the current of the resistor under test out through the first current transmission terminal of the resistance measurement channel.

[0010] In one embodiment, the first polarity switching circuit includes a third switch assembly and a fourth switch assembly. A first terminal of the third switch assembly is connected to the power input terminal. A second terminal of the third switch assembly is connected to both the first terminal of the fourth switch assembly and the first current transmission terminal of the resistance measurement channel. A second terminal of the fourth switch assembly is connected to a ground terminal. Both the controlled terminals of the third and fourth switch assemblies are electrically connected to the control circuit. The second polarity switching circuit includes a fifth switch assembly and a sixth switch assembly. A first terminal of the fifth switch assembly is connected to the power input terminal. A second terminal of the fifth switch assembly is connected to both the first terminal of the sixth switch assembly and the second terminal of the reference resistance switching circuit. A second terminal of the sixth switch assembly is connected to a ground terminal. Both the controlled terminals of the fifth and sixth switch assemblies are electrically connected to the control circuit.

[0011] In one embodiment, the resistance measurement circuit further includes a third polarity switching circuit, which includes an upper bridge arm first switch, an upper bridge arm second switch, a lower bridge arm first switch, and a lower bridge arm second switch. The first ends of the upper bridge arm first switch and the upper bridge arm second switch are both connected to the power input terminal. The second ends of the upper bridge arm first switch are respectively connected to the first current transmission terminal of the resistance measurement channel and the first end of the lower bridge arm first switch. The second ends of the upper bridge arm second switch are respectively connected to the second end of the resistance measurement channel and the first end of the lower bridge arm second switch. The second ends of the lower bridge arm first switch and the lower bridge arm second switch are connected. The controlled terminals of the upper bridge arm first switch, upper bridge arm second switch, lower bridge arm first switch, and lower bridge arm second switch are all electrically connected to the control circuit. The resistance measurement channel is also used to guide the current input through the second current transmission terminal into the resistor under test, and to guide the current of the resistor under test out through the first current transmission terminal of the resistance measurement channel.

[0012] In one embodiment, the current switching circuit includes: a constant current source circuit and a second reference resistor switching circuit. The first terminal of the constant current source circuit is connected to the second terminal of the first switch of the lower bridge arm and the second terminal of the second switch of the lower bridge arm, respectively. The resistance measurement circuit further includes: a fourth polarity switching circuit. The fourth polarity switching circuit includes an upper bridge arm third switch, an upper bridge arm fourth switch, a lower bridge arm third switch, and a lower bridge arm fourth switch. The first terminals of the upper bridge arm third switch and the upper bridge arm fourth switch are both connected to the second terminal of the constant current source circuit. The second terminals of the upper bridge arm third switch are connected to the first terminals of the second reference resistor switching circuit and the lower bridge arm third switch, respectively. The second terminals of the upper bridge arm fourth switch are connected to the second terminals of the second reference resistor switching circuit and the lower bridge arm fourth switch, respectively. The second terminals of the lower bridge arm third switch and the lower bridge arm fourth switch are both connected to a ground terminal. The controlled terminals of the upper bridge arm third switch, the upper bridge arm fourth switch, the lower bridge arm third switch, and the lower bridge arm fourth switch are all electrically connected to the control circuit.

[0013] The present invention also proposes a resistance measuring device, including a probe assembly and a resistance measuring circuit as described in any of the above claims. The probe assembly is used to connect to both ends of the resistor to be measured, and the probe assembly is connected to the first current transmission terminal and the second terminal of the resistance measuring channel of the resistance measuring circuit.

[0014] This invention includes a resistance measurement channel, a first reference resistor switching circuit, a current switching circuit, and a control circuit. The control circuit acquires the resistance range of the resistor under test. When the resistance range of the resistor under test is not less than a preset resistance value, the control circuit controls the first reference resistor switching circuit to switch its own resistance value according to the resistance range of the resistor under test, so that the resistance value of the first reference resistor switching circuit is within the same order of magnitude as the resistance range of the resistor under test. Subsequently, the control circuit synchronously acquires the voltage drop across the resistor under test and the voltage drop across the reference resistor switching circuit, and calculates the resistance value of the resistor under test using a proportional calculation method based on the known reference resistor value. The control circuit also controls the current switching circuit to switch the current flowing through the resistance measurement channel according to the resistance range of the resistor under test, so that the voltage across the resistor under test is within a preset voltage range, when the resistance range of the resistor under test is less than the preset resistance value, so that the voltage across the resistor under test is within the preset voltage range. Simultaneously, the control circuit calculates the resistance value of the resistor under test based on the voltage across the resistor under test and the current switching circuit switching the current flowing through the resistance measurement channel, using Ohm's law.

[0015] Through the above-described configuration, the resistance measurement circuit of this invention can seamlessly cover the measurement needs of large resistances not less than a preset resistance value and small resistances less than a preset threshold, significantly expanding the effective range of a single measuring device. In practical applications, the resistance measurement device integrating this circuit can independently complete the measurement of the vast majority of resistances in electronic testing and quality inspection, without relying on multiple dedicated devices working together. This effectively avoids the cumbersome operation caused by instrument switching in traditional solutions, greatly simplifies the testing process, and improves testing efficiency and user experience. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 is a schematic diagram of the circuit structure of one embodiment of the present invention; Figure 2 is a schematic diagram of the circuit structure of another embodiment of the present invention; Figure 3 is a schematic diagram of the circuit structure of yet another embodiment of the present invention; Figure 4 is a schematic diagram of the circuit structure of yet another embodiment of the present invention; Figure 5 is a schematic diagram of the circuit structure of yet another embodiment of the present invention; Figure 6 is a schematic diagram of the circuit structure of another embodiment of the present invention; Figure 7 is a schematic diagram of the circuit structure of another embodiment of the present invention; Figure 8 is a schematic diagram of the circuit structure of yet another embodiment of the present invention; Figure 9 is a schematic diagram of the circuit structure of yet another embodiment of the present invention; Figure 10 is a schematic diagram of the circuit structure of yet another embodiment of the present invention; Figure 11 is a schematic diagram of the circuit structure of another embodiment of the present invention; Figure 12 is a schematic diagram of the circuit structure of yet another embodiment of the present invention; Figure 13 is a schematic diagram of the circuit structure of yet another embodiment of the present invention; Figure 14 is a schematic diagram of the circuit structure of yet another embodiment of the present invention.

[0018] Reference numerals in the attached diagrams are as follows: 10, Resistance measurement channel; 20, First reference resistor switching circuit; 21, First switching assembly; 22, First reference resistor; 30, Current switching circuit; 31, Constant current source circuit; 311, Amplifier circuit; 312, Comparator circuit; 313, Switching transistor circuit; 32, Second reference resistor switching circuit; 321, Second reference circuit; 322, Second switching assembly; 40, Control circuit; 50, First polarity switching circuit; 60, Second polarity switching circuit; 51, Third switching assembly; 52, Fourth switching assembly; 61, Fifth switching assembly; 70, Polarity selector; 80, Operational amplifier; 90, Channel switching circuit; 91, Sixth switching assembly.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] In electronic testing and quality inspection, resistance measurement needs to cover a wide range from micro-ohms to mega-ohms. However, current resistance measuring devices can usually only measure one of the micro-ohm or mega-ohm ranges. Therefore, users need to use both micro-ohm and mega-ohm measuring devices to measure resistance, which is quite inconvenient.

[0024] To address the aforementioned problems, this invention proposes a resistance measurement circuit. In one embodiment, referring to FIG1, the resistance measurement circuit includes: a power input terminal, a resistance measurement channel 10, a first reference resistance switching circuit 20, a current switching circuit 30, and a control circuit 40. The first current transmission terminal of the resistance measurement channel 10 is connected to the power input terminal. The first and second terminals of the resistance measurement channel 10 are respectively used to connect to the two ends of the resistor under test. The resistance measurement channel 10 is used to guide the current input through the first current transmission terminal into the resistor under test, and to guide the current of the resistor under test to flow out through the second current transmission terminal of the resistance measurement channel 10. The first terminal of the first reference resistance switching circuit 20 is connected to the second current transmission terminal of the resistance measurement channel 10, and the second terminal of the first reference resistance switching circuit 20 is connected to the ground terminal. The current switching circuit 40... The first end of circuit 30 is connected to the second current transmission end of the resistance measurement channel 10, and the second end of the current switching circuit 30 is connected to the ground end. The current switching circuit 30 is used to switch the current flowing through the resistance measurement channel 10. The control circuit 40 is used to obtain the resistance value range of the resistor to be measured, and when the resistance value range of the resistor to be measured is not less than a preset resistance value, it controls the first reference resistance switching circuit 20 to switch its own resistance value according to the resistance value range of the resistor to be measured, so that the resistance value of the first reference resistance switching circuit 20 and the resistance value range of the resistor to be measured are in the same order of magnitude. The control circuit 40 is also used to control the current switching circuit 30 to switch the current flowing through the resistance measurement channel 10 according to the resistance value range of the resistor to be measured when the resistance value range of the resistor to be measured is less than a preset resistance value, so that the voltage of the resistor to be measured is within a preset voltage range.

[0025] In this embodiment, the first and second ends of the resistance measurement channel 10 can be connected to the two ends of the resistor under test via the probe assembly, respectively. The first end of the resistance measurement channel 10 is also connected to the first current transmission terminal, and the second end of the resistance measurement channel 10 is also connected to the second current transmission terminal, so that the current input from the current input terminal can flow into the resistor under test through the first current transmission terminal and flow out through the second current transmission terminal. In practical applications, the resistance measurement channel 10 can be implemented using a mechanical fixture. The mechanical fixture has four probes (or pins) with Kelvin connections integrated inside, and only the interfaces of the "first current transmission terminal", "second current transmission terminal" and "first end and second end" are exposed externally.

[0026] It should be noted that the resistance range of the resistor under test can be known in advance by the user and input into the control circuit 40 through the human-machine interface. Alternatively, when the measurement of the resistor under test begins, the current switching circuit 30 initially switches the current of the resistor measurement channel 10 to a safe small current by default, and the control circuit 40 roughly calculates the resistance range of the resistor under test by detecting the voltage of the resistor under test and the small current.

[0027] In this embodiment, when the resistance value of the resistor under test is not less than a preset resistance value, it indicates that the resistor under test is a large resistor, such as a megohm-level resistor. It is understood that a large resistor will generate a tiny current under a fixed voltage, and this tiny current is difficult to measure accurately. Calculating the resistance value of the resistor under test using the weak current flowing through it and the voltage across it would result in a large error. Therefore, when the resistance value of the resistor under test is not less than the preset resistance value, the control circuit 40 acquires the voltage of the resistor under test and the voltage of the first reference resistor switching circuit 20, and calculates the resistance value of the resistor under test based on the voltage of the resistor under test, the voltage of the first reference resistor switching circuit 20, and the resistance value, using a proportional calculation method. This eliminates the need to calculate based on the resistance value flowing through the resistor under test, thus avoiding the error caused by calculating using a weak current.

[0028] It should be noted that, when the resistance value of the resistor under test is not less than the preset resistance value, the control circuit 40 also controls the first reference resistor switching circuit 20 to switch its own resistance value according to the resistance value range of the resistor under test. This ensures that the resistance value of the first reference resistor switching circuit 20 and the resistance value range of the resistor under test are within the same order of magnitude. For example, when the resistance value range of the resistor under test is approximately 5.6kΩ, the control circuit 40 determines that 5.6kΩ belongs to the 1kΩ~10kΩ range and accordingly controls the first reference resistor switching circuit 20 to switch its own resistance value to 10kΩ, so that the resistance value of the first reference resistor switching circuit 20 and the resistance value range of the resistor under test are within the same order of magnitude. With this setting, when the reference resistor switching circuit and the resistor under test are in the same order of magnitude, their voltage division is close, the voltage ratio calculation error is minimized, and it can ensure that the voltage drop of the resistor under test and the voltage drop on the reference resistor switching circuit are balanced and within the voltage detection range of the control circuit 40. This suppresses the relative quantization error and measurement noise amplification effect caused by the control circuit 40 detecting an excessively small voltage signal.

[0029] When the resistance value of the resistor under test is less than the preset resistance value, it indicates that the resistor under test belongs to the category of small resistors, such as resistors in the micro-ohm range. It is understandable that when the resistance value of the resistor under test is small, the voltage signal across its terminals is weak, and the control circuit 40 is easily affected by noise and quantization errors when detecting its voltage. In some cases, the control circuit 40 may even fail to detect the voltage due to its low voltage. To address this, the control circuit 40 controls the first reference resistor switching circuit 20 to turn off and the current switching circuit 30 to turn on, so that current flows sequentially through the resistor under test and the current switching circuit 30. Furthermore, based on the resistance value range of the resistor under test, the control circuit 40 controls the current switching circuit 30 to switch the current flowing through the resistance measurement channel 10, ensuring that the voltage of the resistor under test is within the preset voltage range. For example, if the resistance value of the resistor under test is approximately 5mΩ, the control circuit 40 sequentially multiplies the currents that can be switched by the multiple current switching circuits 30 by 5mΩ until a current exists that can bring the voltage of the resistor under test within the preset voltage range of 10-500mV. The preset voltage range is the voltage detection range of the control circuit 40. Researchers can set this range based on the actual or optimal voltage detection range of the control circuit 40. With this setting, regardless of how small the resistor under test is, the voltage across it can be actively "lifted" to the measurable and accurate range of the control circuit 40, fundamentally solving the problem of weak signal detection failure. Simultaneously, the control circuit 40 switches the current flowing through the resistance measurement channel 10 based on the voltage and current switching circuit 30 of the resistor under test, and calculates the resistance value of the resistor under test according to Ohm's law.

[0030] It should be noted that the preset resistance value is a set boundary threshold, which is used by the control circuit 40 to determine whether the resistance to be measured should be calculated using the above-mentioned proportional calculation method or Ohm's law method; the preset resistance value can be determined by experimental calibration based on the system hardware parameters and actual measurement error data, so as to optimize the measurement accuracy across the entire range.

[0031] It should be noted that the resistance value that the first reference resistor switching circuit 20 can switch and the current value that the current switching circuit 30 can switch are both known values, so that the control circuit 40 can calculate the resistance value of the resistor to be measured based on the known resistance value of the first reference resistor switching circuit 20 or the known current of the current switching circuit 30.

[0032] In this embodiment, the control circuit 40 can be implemented using a main controller, such as an MCU (Microcontroller Unit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), or SOC (System-on-Chip). The analog-to-digital converter within the control circuit 40 is connected to the first and second current transmission terminals of the resistance measurement channel 10 to detect the voltage drop across the resistor under test. It is also connected to the first and second terminals of the first reference resistor switching circuit 20 to detect the voltage drop across the first reference resistor switching circuit 20.

[0033] Through the above-described configuration, the resistance measurement circuit of this invention can seamlessly cover the measurement needs of large resistances not less than a preset resistance value and small resistances less than a preset threshold, significantly expanding the effective range of a single measuring device. In practical applications, the resistance measurement device integrating this circuit can independently complete the measurement of the vast majority of resistances in electronic testing and quality inspection, without relying on multiple dedicated devices working together. This effectively avoids the cumbersome operation caused by instrument switching in traditional solutions, greatly simplifies the testing process, and improves testing efficiency and user experience.

[0034] In one embodiment of the present invention, optionally, referring to FIG2, the first reference resistor switching circuit 20 includes: a plurality of first reference resistors 22 and a plurality of first switching components 21. The first ends of the plurality of first reference resistors 22 are all connected to the second current transmission terminal of the resistance measurement channel 10, the second ends of the plurality of first reference resistors 22 are connected one-to-one with the first ends of the plurality of first switching components 21, the first ends of the plurality of reference resistors are all connected to a ground terminal, and the controlled terminal of the first switching component 21 is electrically connected to the control circuit 40. The first switching component 21 is implemented using a switching transistor, such as a MOSFET, IGBT, thyristor, transistor, power transistor, etc., and / or using a switching device, such as a contactor, circuit breaker, and relay.

[0035] In this embodiment, the resistance values ​​of the multiple first reference resistors 22 are stored in the control circuit 40. When the control circuit 40 receives the resistance range of the resistor to be measured, it compares it with the resistance values ​​of the multiple first reference resistors 22 one by one, selects the first reference resistor 22 whose resistance range is in the same order of magnitude as the resistor to be measured, and controls the first switch assembly 21 connected to the first reference resistor 22 to be turned on, while controlling the other first switch assemblies 21 to be turned off. For example, when the resistance range of the resistor to be measured is approximately 5.6kΩ, the control circuit 40 determines that 5.6kΩ belongs to the 1kΩ~10kΩ range, and accordingly controls the first switch assembly 21 connected to the first reference resistor 22 with a resistance value of 10kΩ to be turned on, while controlling the other first switch assemblies 21 to be turned off.

[0036] With this configuration, when the first reference resistor 22 and the resistor under test are of the same order of magnitude, their voltage divisions are close, resulting in the smallest voltage ratio calculation error. This ensures that the voltage drop of the resistor under test and the voltage drop on the reference resistor switching circuit are balanced and within the voltage detection range of the control circuit 40, thus suppressing the relative quantization error and measurement noise amplification effect caused by the control circuit 40 detecting an excessively small voltage signal.

[0037] Optionally, the first reference resistor switching circuit 20 can also be implemented using a single-pole multi-throw switch and multiple first reference resistors 22. The moving contact of the single-pole multi-throw switch is connected to the second current transmission terminal of the resistance measurement channel 10, and the multiple stationary contacts of the single-pole multi-throw switch are connected one-to-one with the first terminals of the multiple first reference resistors 22. When the control circuit 40 receives the resistance value range of the resistor to be measured, it compares it with the resistance values ​​of the multiple first reference resistors 22 one by one, selects the first reference resistor 22 that is in the same order of magnitude as the resistance value range of the resistor to be measured, and controls the stationary contact and moving contact connected to the first reference resistor 22.

[0038] In one embodiment of the present invention, optionally, referring to FIG3, the current switching circuit 30 includes: a constant current source circuit 31 and a second reference resistor switching circuit 32. The first end of the constant current source circuit 31 is connected to the second current transmission end of the resistance measurement channel 10, and the second end of the constant current source circuit 31 is connected to the first end of the second reference resistor switching circuit 32. The second end of the second reference resistor switching circuit 32 is connected to a ground terminal. The first and second ends of the second reference resistor switching circuit 32 are also connected to the controlled end of the constant current source circuit 31. The controlled end of the second reference resistor switching circuit 32 is electrically connected to the control circuit 40. The constant current source circuit 31 is used to switch the current flowing through the resistance measurement channel 10 based on the voltage of the second reference resistor switching circuit 32. The control circuit 40 is used to control the second reference resistor switching circuit 32 to switch the resistance value according to the resistance value range of the resistor to be measured, thereby controlling the constant current source circuit 31 to switch the current flowing through the resistance measurement channel 10 so that the voltage of the resistor to be measured is within a preset voltage range.

[0039] In this embodiment, each resistance value that the second reference resistor switching circuit 32 can switch to is pre-calibrated. The constant current source circuit 31 can form a closed-loop control based on its built-in known reference voltage, or the reference voltage output by the control circuit 40 to the constant current source circuit 31 and the feedback voltage across the second reference resistor switching circuit 32, so as to make the current flowing through the resistance measurement channel 10 accurate and stable. Thus, the control circuit 40 can calculate the resistance value with high precision based on the known current value and the voltage across the resistor to be measured, according to Ohm's law, thereby reducing the system error introduced by current fluctuations.

[0040] In one embodiment, referring to FIG4, the constant current source circuit 31 includes: an amplifier circuit 311, the first input terminal of which is connected to the first terminal of the second reference resistor switching circuit 32, and the second input terminal of which is connected to the second terminal of the second reference resistor switching circuit 32; a comparator circuit 312, the output terminal of which is connected to the first input terminal of the comparator circuit 312, and the second input terminal of which is used to connect to a first voltage; and a switching transistor circuit 313, the output terminal of which is connected to the controlled terminal of the switching transistor circuit 313, the first terminal of which is connected to the second current transmission terminal of the resistance measurement channel 10, and the second terminal of which is connected to the second terminal of the second reference resistor switching circuit 32. The amplifier circuit 311 is implemented using at least one amplifier, the comparator circuit 312 is implemented using at least one comparator, one of the first input terminal and the second input terminal of the comparator circuit 312 is an inverting input terminal and the other is a non-inverting input terminal, and the switching transistor circuit 313 is implemented using at least one switching transistor.

[0041] Amplifier circuit 311 amplifies the voltage drop of the second reference resistor switching circuit 32 and outputs it to the first input terminal of comparator circuit 312, thereby improving the signal-to-noise ratio and the comparison sensitivity of comparator circuit 312. Comparator circuit 312 compares the first voltage and the voltage of the second reference resistor switching circuit 32, and outputs a high-level signal or a low-level signal to switching transistor circuit 313 according to the comparison result, so as to adjust the conduction level or conduction frequency of switching transistor circuit 313, thereby adjusting the current in the circuit.

[0042] To illustrate with an example, when the switching circuit 313 uses an NMOS transistor, with the first input terminal being the non-inverting input terminal and the second input terminal being the inverting input terminal, if the approximate resistance value of the resistor to be measured is small, for example, less than 2 milliohms, the control circuit 40 controls the second reference resistor switching circuit 32 to switch to a smaller fixed resistance value (e.g., 2 milliohms). At this time, the voltage of the second reference resistor switching circuit 32 is small and less than the first voltage, so that the comparator circuit 312 outputs a high-level signal to the switching circuit 313, increasing the conduction threshold of the switching circuit 313, thereby increasing the current in the measurement circuit, for example, 20A. If the approximate resistance value of the resistor to be measured is large, for example, greater than 2 milliohms and less than 2 ohms, the control circuit 40 controls the second reference resistor switching circuit 32 to switch to a larger fixed resistance value. At this time, the voltage of the second reference resistor switching circuit 32 increases and is greater than the first voltage, so that the comparator circuit 312 outputs a low-level signal to the switching circuit 313, decreasing the conduction threshold of the switching circuit 313, thereby decreasing the current in the measurement circuit, for example, 2A. In this way, the voltage of the resistor under test can be controlled to always be within the measurement range of the control circuit 40. The control circuit 40 will not be damaged due to excessive voltage of the resistor under test, nor will the measurement accuracy be affected due to insufficient voltage of the resistor under test, thus improving the reliability of resistance measurement.

[0043] In one embodiment, referring to FIG5, the second reference resistor switching circuit 32 includes: a plurality of second reference resistors 321 and a plurality of second switching components 322. The first ends of the plurality of second reference resistors 321 are all connected to the second end of the constant current source circuit 31. The second ends of the plurality of second reference resistors 321 are connected one-to-one with the first ends of the plurality of second switching components 322. The first and second ends of the plurality of second reference resistors 321 are also electrically connected to the constant current source circuit 31. The second end of the second switching component 322 is connected to the ground terminal. The controlled terminal of the second switching component 322 is electrically connected to the control circuit 40. The second switching component 322 is implemented using a switching transistor, such as a MOSFET, IGBT, thyristor, transistor, power transistor, etc., and / or using a switching device, such as a contactor, circuit breaker, and relay.

[0044] It should be noted that the control circuit 40 has pre-stored the current flowing through the resistance measurement channel 10 corresponding to the control constant current source circuit 31 for each second reference resistor 321. Therefore, when the control circuit 40 receives the resistance value range of the resistor to be measured, it multiplies the various currents that the control constant current source circuit 31 corresponding to each second reference resistor 321 can switch until a certain current can make the voltage of the resistor to be measured within the preset voltage range. Then, it controls the second switch component 322 connected to the second reference resistor 321 corresponding to the current to be turned on, and controls the other second switch components 322 to be turned off, so that the voltage of the resistor to be measured is within the preset voltage range.

[0045] The multiple second reference resistors 321 have different resistance values ​​and can increase in a stepped manner according to a set sequence. When the control circuit 40 switches between different resistance values ​​of the second reference resistors 321, the voltage fed back to the constant current source circuit 31 changes in a stepped manner, thereby causing the current in the adjustment loop of the constant current source circuit 31 to decrease in a corresponding stepped manner. With this setting, there is always a current that can adjust the voltage across the resistor under test to the preset voltage range, thus balancing measurement safety and accuracy and achieving reliable adaptive matching.

[0046] Optionally, the current switching circuit 30 can also be implemented using an operational amplifier, a MOSFET, and the aforementioned second reference resistor switching circuit 32. The first terminal of the MOSFET is connected to the second current transmission terminal of the resistance measurement channel 10, and the second terminal is connected to the ground terminal. The non-inverting input terminal of the operational amplifier is connected to a known reference voltage, and the inverting input terminal is connected to the first terminal of the second reference resistor switching circuit 32 to sample the voltage of the second reference resistor switching circuit 32 in real time. The operational amplifier is used to adjust the gate voltage of the MOSFET according to the set voltage and the voltage of the second reference resistor switching circuit 32, so as to switch the current magnitude in the entire loop by adjusting the conduction degree or conduction frequency of the MOSFET, thereby realizing the switching of the current flowing through the resistance measurement channel 10.

[0047] In high-precision resistance measurement, thermoelectric potential is a significant interference factor affecting measurement accuracy. When different metal materials (such as copper wire, solder joints, and leads) exist in the measurement circuit and the temperatures of the contact points are inconsistent, a microvolt-level parasitic voltage (i.e., thermoelectric potential) will be generated due to the Seebeck effect. This voltage will be directly superimposed on the measurement signal across the resistor under test and the second reference resistor 321, causing the ADC sampling result to deviate from the true value.

[0048] In one embodiment of the present invention, referring to FIG6, the resistance measurement circuit further includes: a first polarity switching circuit 50 and a second polarity switching circuit 60. A first terminal of the first polarity switching circuit 50 is connected to the power input terminal, a second terminal of the first polarity switching circuit 50 is connected to the ground terminal, and a third terminal of the first polarity switching circuit 50 is connected to the first current transmission terminal of the resistance measurement channel 10. A first terminal of the second polarity switching circuit 60 is connected to the power input terminal, a second terminal of the second polarity switching circuit 60 is connected to the ground terminal, and a third terminal of the second polarity switching circuit 60 is connected to the first reference resistance switching circuit 20. The second terminal is connected, and the controlled terminal of the first polarity switching circuit 50 and the controlled terminal of the second polarity switching circuit 60 are both electrically connected to the control circuit 40; the first polarity switching circuit 50 is used to control the resistance measurement channel 10 to be connected to one of the power input terminal and the ground terminal, and the second polarity switching circuit 60 is used to control the second terminal of the first reference resistance switching circuit 20 to be connected to the other of the power input terminal and the ground terminal; wherein, the resistance measurement channel 10 is also used to guide the current input through the second current transmission terminal to flow into the resistor under test, and guide the current of the resistor under test to flow out through the first current transmission terminal of the resistance measurement channel 10.

[0049] In this embodiment, when the resistance measurement circuit measures the resistance to be measured, the control circuit 40 first controls the first reference resistance switching circuit 20 to switch its own resistance value according to the resistance range of the resistance to be measured, so that the resistance value of the first reference resistance switching circuit 20 is within the same order of magnitude as the resistance value of the resistance to be measured. The control circuit 40 also controls the power input terminal of the first switching circuit to connect to the first current transmission terminal of the resistance measurement channel 10, and controls the ground terminal to connect to the second terminal of the first reference resistance switching circuit 20, so that current flows from the resistance measurement channel 10 to the first reference resistance switching circuit 20. Simultaneously, the control circuit 40 collects the forward voltage drop of the resistance to be measured and the forward voltage drop of the first reference resistance switching circuit 20. Subsequently, the control circuit 40 also controls the ground terminal to connect to the first current transmission terminal of the resistance measurement circuit, and controls the power input terminal to connect to the second terminal of the first reference resistance switching circuit 20, so that current flows from the first reference resistance switching circuit 20 to the resistance measurement channel 10. Simultaneously, the control circuit 40 collects the reverse voltage drop of the resistance to be measured and the reverse voltage drop of the first reference resistance switching circuit 20.

[0050] Since the thermoelectric potential is a DC bias voltage with a fixed direction and is independent of the current direction, while the voltage drop across the resistor under test and the first reference resistor switching circuit 20 is proportional to the current direction, the thermoelectric potential is superimposed on both the forward and reverse voltage drops in both measurements. The control circuit 40 subtracts the forward voltage from the reverse voltage to eliminate the influence of the thermoelectric potential, retaining only twice the true voltage drop. Similarly, subtracting the two measurements from the first reference resistor switching circuit 20 can also eliminate the thermoelectric potential in its path. Finally, the control circuit 40 calculates the ratio of the forward and reverse voltage difference of the resistor under test to the forward and reverse voltage difference of the first reference resistor switching circuit 20, and then multiplies it by the known resistance value of the first reference resistor switching circuit 20 to obtain the accurate resistance value of the resistor under test.

[0051] In this embodiment, optionally, referring to FIG7, the first polarity switching circuit 50 includes: a third switch component 51 and a fourth switch component 52. The first end of the third switch component 51 is connected to the power input terminal, the second end of the third switch component 51 is connected to the first end of the fourth switch component 52 and the first current transmission terminal of the resistance measurement channel 10, the second end of the fourth switch component 52 is connected to the ground terminal, and the controlled ends of the third switch component 51 and the fourth switch component 52 are both electrically connected to the control circuit 40; the second polarity switching circuit 60 includes: a fifth switch component 61 and a sixth switch component 91. The first end of the fifth switch component 61 is connected to the power input terminal, the second end of the fifth switch component 61 is connected to the first end of the sixth switch component 91 and the second end of the reference resistance switching circuit, the second end of the sixth switch component 91 is connected to the ground terminal, and the controlled ends of the fifth switch component 61 and the sixth switch component 91 are both electrically connected to the control circuit 40. The third switch assembly 51, the fourth switch assembly 52, the fifth switch assembly 61 and the sixth switch assembly 91 can all be implemented using switching transistors, such as MOSFETs, IGBTs, thyristors, transistors, power transistors, etc., and / or using switching devices, such as contactors, circuit breakers and relays.

[0052] Control circuit 40 is used to control the third switch assembly 51 to be turned on and the fourth switch assembly 52 to be turned off, so that the power input terminal is connected to the first current transmission terminal of the resistance measurement channel 10, or to control the third switch assembly 51 to be turned off and the fourth switch assembly 52 to be turned off, so that the ground terminal is connected to the second terminal of the first reference resistance switching circuit 20. Control circuit 40 is also used to control the fifth switch assembly 61 to be turned on and the sixth switch assembly 91 to be turned off, so that the power input terminal is connected to the second terminal of the first reference resistance switching circuit 20, or to control the fifth switch assembly 61 to be turned off and the sixth switch assembly 91 to be turned off, so that the ground terminal is connected to the second terminal of the first reference resistance switching circuit 20.

[0053] Optionally, the first and second switching circuits can also be implemented using a single-pole double-throw switch. When the first switching circuit is a single-pole double-throw switch, the moving contact of the single-pole double-throw switch is connected to the first current transmission terminal of the resistance measurement channel 10, the first stationary contact is connected to the power input terminal, and the second stationary contact is connected to the ground terminal. The control circuit 40 is used to control the moving contact to connect to the first stationary contact so that the power input terminal is connected to the first current transmission terminal of the resistance measurement channel 10, or to control the moving contact to connect to the second stationary contact so that the ground terminal is connected to the first current transmission terminal of the resistance measurement channel 10. When the second switching circuit is a single-pole double-throw switch, the moving contact of the single-pole double-throw switch is connected to the second terminal of the reference resistor circuit, the first stationary contact is connected to the power input terminal, and the second stationary contact is connected to the ground terminal. The control circuit 40 is used to control the moving contact to connect to the first stationary contact so that the power input terminal is connected to the second terminal of the first reference resistor switching circuit 20, or to control the moving contact to connect to the second stationary contact so that the ground terminal is connected to the second terminal of the first reference resistor switching circuit 20.

[0054] In one embodiment of the present invention, referring to FIG8, the resistance measurement circuit further includes: a third polarity switching circuit, the third polarity switching circuit including an upper bridge arm first switch K11, an upper bridge arm second switch K12, a lower bridge arm first switch K21, and a lower bridge arm second switch K22. The first ends of the upper bridge arm first switch K11 and the upper bridge arm second switch K12 are both connected to the power input terminal. The second end of the upper bridge arm first switch K11 is connected to the first current transmission terminal of the resistance measurement channel 10 and the first end of the lower bridge arm first switch K21, respectively. The second end of the upper bridge arm second switch K12 is connected to the first current transmission terminal of the resistance measurement channel 10 and the first end of the lower bridge arm first switch K22. The two ends are respectively connected to the second end of the resistance measurement channel 10 and the first end of the lower bridge arm second switch K22. The second end of the lower bridge arm first switch K21 and the second end of the lower bridge arm second switch K22 are connected. The controlled ends of the upper bridge arm first switch K11, upper bridge arm second switch K12, lower bridge arm first switch K21 and lower bridge arm second switch K22 are all electrically connected to the control circuit 40. The resistance measurement channel 10 is also used to guide the current input through the second current transmission terminal into the resistor under test, and guide the current of the resistor under test to flow out through the first current transmission terminal of the resistance measurement channel 10.

[0055] In this embodiment, both the upper and lower bridge arm switches can be implemented using switching transistors such as MOSFETs, IGBTs, thyristors, transistors, and power transistors. The third polarity switching circuit is used to switch the direction of current flowing through the resistor under test. When the first switch K11 of the upper bridge arm and the second switch K22 of the lower bridge arm are on, and the second switches K12 of the upper bridge arm and K22 of the lower bridge arm are off, the current flows through the resistor under test in the first direction. When the second switches K12 of the upper bridge arm and K22 of the lower bridge arm are on, and the first switch K11 of the upper bridge arm and K22 of the lower bridge arm are off, the current flows through the resistor under test in the second direction. The first direction is from the power input terminal to the ground terminal, and the second direction is from the ground terminal to the power input terminal.

[0056] During the measurement process, the control circuit 40 controls the direction of the current flowing through the resistor under test in the third polarity switching circuit to either the first direction or the second direction, and collects the voltage drop of the resistor under test in the first direction. Subsequently, the control circuit switches the direction of the current flowing through the resistor under test to either the first direction or the second direction, and collects the voltage drop of the resistor under test in the second direction.

[0057] It should be noted that the first directional voltage drop consists of two parts: one is the actual voltage drop generated by the resistor under test under the action of current, which is in the same direction as the current; the other is the thermoelectric potential, which is independent of the direction of the current. Therefore, the first directional voltage drop is equal to: the actual voltage drop of the resistor under test (positive value) + the thermoelectric potential (fixed offset).

[0058] Since the first and second directions are opposite, the voltage drop generated by the resistor under test also reverses synchronously (becomes negative); however, the polarity of the thermoelectric potential remains unchanged (still the same fixed offset). Therefore, the voltage drop in the second direction is: the true resistance voltage drop (negative) + the thermoelectric potential (fixed offset). Next, the two measurement results are subtracted and halved: when the two readings are subtracted, the identical thermoelectric potential portions cancel each other out; while the true voltage drop of the resistor under test, due to its opposite sign, becomes twice as much after subtraction; taking half again precisely restores the original true voltage drop value. Finally, based on the true voltage drop of the resistor under test and the current flowing through it, the true resistance value of the resistor under test can be calculated, eliminating the influence of the thermoelectric potential.

[0059] When the current switching circuit 30 includes the constant current source circuit 31 and the second reference resistor switching circuit 32 of the above embodiments, the resistance measurement channel 10, the constant current source circuit 31 and the second reference resistor switching circuit 32 are connected in series in the same circuit. When the direction of the current flowing through the resistance measurement channel 10 is switched, the direction of the current flowing through the second reference resistor switching circuit 32 should also be switched synchronously to maintain the consistency of the loop current.

[0060] In this embodiment, referring to Figure 9, the first terminal of the constant current source circuit 31 is connected to the second terminal of the first switch K21 of the lower bridge arm and the second terminal of the second switch K22 of the lower bridge arm, respectively. The resistance measurement circuit further includes a fourth polarity switching circuit, which includes an upper bridge arm third switch K13, an upper bridge arm fourth switch K14, a lower bridge arm third switch K23, and a lower bridge arm fourth switch K24. The first terminals of the upper bridge arm third switch K13 and the upper bridge arm fourth switch K14 are both connected to the second terminal of the constant current source circuit 31. The first terminal of the upper bridge arm third switch K13 is connected to the second terminal of the constant current source circuit 31. The second terminal of switch 3 is connected to the first terminal of the second reference resistor switching circuit 32 and the first terminal of the lower bridge arm third switch K23, respectively. The second terminal of the upper bridge arm fourth switch K14 is connected to the second terminal of the second reference resistor switching circuit 32 and the first terminal of the lower bridge arm fourth switch K24, respectively. The second terminals of the lower bridge arm third switch K23 and the lower bridge arm fourth switch K24 are both connected to the ground terminal. The controlled terminals of the upper bridge arm third switch K13, the upper bridge arm fourth switch K14, the lower bridge arm third switch K23 and the lower bridge arm fourth switch K24 are all electrically connected to the control circuit 40.

[0061] The control circuit 40 synchronizes the upper bridge arm third switch K13 with the upper bridge arm first switch K11, the upper bridge arm fourth switch K14 with the upper bridge arm second switch K12, the lower bridge arm third switch K23 with the lower bridge arm first switch K21, and the lower bridge arm fourth switch K24 with the lower bridge arm second switch K22, so that the direction of the current flowing through the second reference resistor switching circuit 32 is consistent with the direction of the current flowing through the resistor to be measured, thereby maintaining the consistency of the loop current.

[0062] Furthermore, referring to FIG10, when the second reference resistor switching circuit 32 includes a plurality of second reference resistors 321 and a plurality of second switch components 322 as described in the above embodiment, the number of fourth polarity switching circuits is plurality. The second end of the upper bridge arm third switch K13 of each fourth polarity switching circuit is connected to the first end of a second reference resistor 321 and the first end of the lower bridge arm third switch K23, respectively. The second end of the upper bridge arm fourth switch K14 of each second polarity switching circuit 60 is connected to the second end of a second reference resistor 321 and the first end of the corresponding lower bridge arm fourth switch K24, respectively.

[0063] With this configuration, the control circuit 40 can select only the target second reference resistor 321 and its corresponding fourth polarity switching circuit, while the remaining second switching components 322 and second polarity switching circuit 60 are completely disconnected. During commutation measurement, only the currently active second reference resistor 321 branch is switched in the forward / reverse direction to avoid problems such as parasitic paths, leakage current, and cross-coupling caused by multiple second reference resistors 321 switching in parallel.

[0064] It should be noted that, under the action of the fourth polarity switching circuit, the voltage polarity across the second reference resistor switching circuit 32 will reverse with the change of current direction. When the current reverses (for example, switching from the first direction to the second direction), the voltage drop of the second reference resistor switching circuit 32, which was originally "the voltage at the first terminal is positive and the voltage at the second terminal is negative", becomes "the voltage at the first terminal is negative and the voltage at the second terminal is positive". If this reverse voltage is directly sent to the constant current source circuit 31, it may cause the constant current source circuit 31 to become unstable and unable to maintain the stability of the current in the circuit.

[0065] In one embodiment of the present invention, referring to FIG11, the resistance measurement circuit further includes: a polarity selector 70, the first input terminal of the polarity selector 70 being connected to the first terminal of the second reference resistance switching circuit 32, the second input terminal of the polarity selector 70 being connected to the second terminal of the second reference resistance switching circuit 32, and the output terminal of the polarity selector 70 being connected to the constant current source circuit 31. The polarity selector 70 is used to convert the voltage polarity output by the second reference resistance switching circuit 32 to positive and output it to the constant current source circuit 31.

[0066] In this embodiment, it is assumed that the current flowing through the second reference resistor switching circuit 32 in the initial state is in the first direction, at which time the potential of its first terminal is higher than that of the second terminal. Under the coordination of the control circuit 40, the polarity selector 70 selects to output the voltage of the first terminal to the constant current source circuit 31 as a positive polarity feedback signal. When the control circuit 40 drives the second polarity switching circuit 60 to switch the current flowing through the second reference resistor switching circuit 32 to the second direction, the polarity of the potentials at both ends of the second reference resistor switching circuit 32 is reversed (the potential of the second terminal becomes higher), and the polarity selector 70 operates synchronously, switching to output the voltage of the second terminal to the constant current source circuit 31, thereby ensuring that the feedback voltage always remains positive and maintaining the stable operation of the constant current loop.

[0067] In one embodiment, when the constant current source circuit 31 includes the amplifier circuit 311, comparator circuit 312, and switching transistor circuit 313 described in the above embodiments, the polarity selector 70 can be implemented using two single-pole double-throw switches. The moving contacts of the two single-pole double-throw switches are respectively connected to the first input terminal and the second input terminal of the amplifier circuit 311. The first stationary contact and the second stationary contact of one single-pole double-throw switch are respectively connected to the first terminal and the second terminal of the second reference resistor switching circuit 32. The second stationary contact and the first stationary contact of the other single-pole double-throw switch are respectively connected to the first terminal and the second terminal of the second reference resistor switching circuit 32. The control circuit 40 controls the two single-pole double-throw switches in a coordinated manner so that the voltage received at the first input terminal is always the higher of the first terminal voltage and the second terminal voltage of the second reference resistor switching circuit 32, and the voltage received at the second input terminal is always the lower of the first terminal voltage and the second terminal voltage of the second reference resistor switching circuit 32, so that the polarity of the voltage received by the amplifier circuit 311 is always positive.

[0068] In another embodiment, the polarity selector 70 can be implemented using a main controller, such as an MCU (Microcontroller Unit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), or SOC (System-on-Chip). The main controller directly samples the two ends of the second reference resistor switching circuit 32 via a differential ADC, and takes the absolute value of the sampled value according to the direction of the current flowing through the second reference resistor switching circuit 32, so that the voltage polarity output to the constant current source circuit 31 is always positive.

[0069] In one embodiment of the present invention, referring to FIG12, the resistance measurement circuit further includes: an operational amplifier 80, the first input terminal of the operational amplifier 80 being connected to the first current input terminal of the resistance measurement channel 10, the second input terminal of the operational amplifier 80 being connected to the second current input terminal of the resistance measurement channel 10, and the output terminal of the operational amplifier 80 being electrically connected to the control circuit 40.

[0070] In this embodiment, the operational amplifier 80 is used to amplify the voltage drop of the resistor under test and output it to the control circuit 40 so that the control circuit 40 can detect the voltage drop of the resistor under test, avoiding the control circuit 40 from being unable to detect the resistor if the voltage drop is too small, thereby improving the reliability of the resistance measurement.

[0071] In one embodiment of the present invention, referring to FIG13, the number of resistance measurement channels 10 is multiple, and the resistance measurement circuit further includes a channel switching circuit 90. The first terminal of the channel switching circuit 90 is connected to the power input terminal, and the second terminal of the channel switching circuit 90 is connected to the first terminal of the first reference resistance switching circuit 20 and the first terminal of the current switching circuit 30, respectively. The channel switching circuit 90 is also electrically connected to multiple resistance measurement channels 10, and the channel switching circuit 90 is also electrically connected to the control circuit 40. The control circuit 40 is connected to the controlled terminal of the channel switching circuit 90.

[0072] When multiple resistance measurement channels 10 are connected to multiple different resistors under test, the control circuit 40 controls the channel switching circuit 90 to connect the corresponding resistors under test to the measurement loop in sequence according to the preset timing sequence, thereby realizing fully automatic polling test of multiple resistors under test without manual measurement, which greatly improves the efficiency of resistance measurement.

[0073] It is understood that the control circuit 40 is connected to the first terminal and the fourth terminal of the channel switching circuit 90 respectively, so that the control circuit 40 can detect the voltage drop of the resistor to be measured in any of the access resistor measurement channels 10.

[0074] In this embodiment, the channel switching circuit 90 can be implemented using multiple switching components. Optionally, referring to FIG14, the channel switching circuit 90 includes multiple seventh switching components, which are sequentially connected in series between the power input terminal and the first terminal of the first reference resistor switching circuit 20. Each seventh switching component is connected in parallel with one of the resistance measurement channels 10. The seventh switching components can be implemented using bidirectional switches such as contactors, circuit breakers, and relays. When it is necessary to measure the resistance to be measured on a target channel, the seventh switching component connected in parallel with that channel is disconnected, thereby connecting the target channel to the measurement circuit; simultaneously, the remaining seventh switching components are kept on, thereby bypassing the remaining non-target channels from the measurement circuit. By sequentially switching and repeating this operation, time-division sequential measurement of multiple resistances to be measured can be achieved.

[0075] Optionally, the first terminals of multiple seventh switch components are all connected to the power input terminal, and the second terminals of the multiple seventh switch components are connected one-to-one with the first terminals of multiple resistance measurement channels 10. The second terminals of the multiple resistance measurement channels 10 are respectively connected to the first terminal of the first reference resistance switching circuit 20 and the first terminal of the current switching circuit 30. When it is necessary to measure the resistance to be measured on a target channel, the seventh switch component connected in series with that channel is turned on, thereby connecting that channel to the measurement circuit; at the same time, the remaining seventh switch components are turned off to disconnect other non-target channels from the measurement circuit. By sequentially switching on different seventh switch components, multiple resistances to be measured can be cyclically measured in a time-division manner.

[0076] The present invention also proposes a resistance measuring device, including a probe assembly and a resistance measuring circuit as described above.

[0077] It is worth noting that since the resistance measuring device of the present invention is based on the resistance measuring circuit described above, the embodiments of the resistance measuring device of the present invention include all the technical solutions of all the embodiments of the resistance measuring circuit described above, and the technical effects achieved are exactly the same, so they will not be repeated here.

[0078] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A resistance measuring circuit, characterized in that, It includes a power input terminal, a resistance measurement channel, a first reference resistance switching circuit, a current switching circuit, and a control circuit. The first current transmission terminal of the resistance measurement channel is connected to the power input terminal, and the first and second terminals of the resistance measurement channel are respectively used to connect to the two ends of the resistor to be measured. The resistance measurement channel is used to guide the current input through the first current transmission terminal into the resistor under test, and to guide the current of the resistor under test out through the second current transmission terminal of the resistance measurement channel; the first terminal of the first reference resistance switching circuit is connected to the second current transmission terminal of the resistance measurement channel, and the second terminal of the first reference resistance switching circuit is connected to the ground terminal; the first terminal of the current switching circuit is connected to the second current transmission terminal of the resistance measurement channel, and the second terminal of the current switching circuit is connected to the ground terminal, and the current switching circuit is used to switch the current flowing through the resistance measurement channel; the control circuit is used to obtain the resistance value range of the resistor under test, and when the resistance value range of the resistor under test is not less than a preset resistance value, to control the first reference resistance switching circuit to switch its own resistance value according to the resistance value range of the resistor under test, so that the resistance value of the first reference resistance switching circuit and the resistance value range of the resistor under test are in the same order of magnitude; the control circuit is also used to control the current switching circuit to switch the current flowing through the resistance measurement channel according to the resistance value range of the resistor under test when the resistance value range of the resistor under test is less than the preset resistance value, so that the voltage of the resistor under test is within the preset voltage range.

2. The resistance measuring circuit as described in claim 1, characterized in that, The first reference resistor switching circuit includes: a plurality of first reference resistors and a plurality of first switching components. The first ends of the plurality of first reference resistors are all connected to the second current transmission end of the resistance measurement channel. The second ends of the plurality of first reference resistors are connected to the first ends of the plurality of first switching components one by one. The first ends of the plurality of reference resistors are all connected to the ground end. The controlled end of the first switching component is electrically connected to the control circuit.

3. The resistance measuring circuit as described in claim 1, characterized in that, The current switching circuit includes a constant current source circuit and a second reference resistor switching circuit. The first terminal of the constant current source circuit is connected to the second current transmission terminal of the resistance measurement channel. The second terminal of the constant current source circuit is connected to the first terminal of the second reference resistor switching circuit. The second terminal of the second reference resistor switching circuit is connected to a ground terminal. The first and second terminals of the second reference resistor switching circuit are also connected to the controlled terminal of the constant current source circuit. The controlled terminal of the second reference resistor switching circuit is electrically connected to the control circuit. The constant current source circuit is used to switch the current flowing through the resistance measurement channel based on the voltage of the second reference resistor switching circuit. The control circuit is used to control the second reference resistor switching circuit to switch the resistance value according to the resistance range of the resistor under test, thereby controlling the constant current source circuit to switch the current flowing through the resistance measurement channel, so that the voltage of the resistor under test is within a preset voltage range.

4. The resistance measuring circuit as described in claim 3, characterized in that, The constant current source circuit includes: an amplifier circuit, the first input terminal of which is connected to the first terminal of the second reference resistor switching circuit, and the second input terminal of which is connected to the second terminal of the second reference resistor switching circuit; a comparator circuit, the output terminal of which is connected to the first input terminal of the comparator circuit, and the second input terminal of which is used to connect to a first voltage; and a switching transistor circuit, the output terminal of which is connected to the controlled terminal of the switching transistor circuit, the first terminal of which is connected to the second current transmission terminal of the resistance measurement channel, and the second terminal of which is connected to the second terminal of the second reference resistor switching circuit.

5. The resistance measuring circuit as described in claim 3, characterized in that, The second reference resistor switching circuit includes: a plurality of second reference resistors and a plurality of second switching components. The first ends of the plurality of second reference resistors are all connected to the second end of the constant current source circuit. The second ends of the plurality of second reference resistors are connected to the first ends of the plurality of second switching components in a one-to-one correspondence. The first and second ends of the plurality of second reference resistors are also electrically connected to the constant current source circuit. The second end of the second switching component is connected to the ground terminal. The controlled terminal of the second switching component is electrically connected to the control circuit.

6. The resistance measuring circuit according to any one of claims 1 to 5, characterized in that, The resistance measurement circuit further includes: a first polarity switching circuit and a second polarity switching circuit. A first terminal of the first polarity switching circuit is connected to the power input terminal, a second terminal of the first polarity switching circuit is connected to the ground terminal, and a third terminal of the first polarity switching circuit is connected to the first current transmission terminal of the resistance measurement channel. A first terminal of the second polarity switching circuit is connected to the power input terminal, a second terminal of the second polarity switching circuit is connected to the ground terminal, and a third terminal of the second polarity switching circuit is connected to the second terminal of the first reference resistance switching circuit. Both the controlled terminals of the first and second polarity switching circuits are electrically connected to the control circuit. The first polarity switching circuit controls the connection of the resistance measurement channel to one of the power input terminal and the ground terminal. The second polarity switching circuit controls the connection of the second terminal of the first reference resistance switching circuit to the other of the power input terminal and the ground terminal. The resistance measurement channel also guides the current input through the second current transmission terminal into the resistor under test and guides the current of the resistor under test out through the first current transmission terminal of the resistance measurement channel.

7. The resistance measuring circuit as described in claim 6, characterized in that, The first polarity switching circuit includes a third switch assembly and a fourth switch assembly. The first end of the third switch assembly is connected to the power input terminal. The second end of the third switch assembly is connected to the first end of the fourth switch assembly and the first current transmission terminal of the resistance measurement channel, respectively. The second end of the fourth switch assembly is connected to a ground terminal. Both the controlled ends of the third and fourth switch assemblies are electrically connected to the control circuit. The second polarity switching circuit includes a fifth switch assembly and a sixth switch assembly. The first end of the fifth switch assembly is connected to the power input terminal. The second end of the fifth switch assembly is connected to the first end of the sixth switch assembly and the second end of the reference resistance switching circuit, respectively. The second end of the sixth switch assembly is connected to a ground terminal. Both the controlled ends of the fifth and sixth switch assemblies are electrically connected to the control circuit.

8. The resistance measuring circuit according to any one of claims 1 to 5, characterized in that, The resistance measurement circuit further includes a third polarity switching circuit, which comprises an upper bridge arm first switch, an upper bridge arm second switch, a lower bridge arm first switch, and a lower bridge arm second switch. The first ends of the upper bridge arm first switch and the upper bridge arm second switch are both connected to the power input terminal. The second ends of the upper bridge arm first switch are respectively connected to the first current transmission terminal of the resistance measurement channel and the first end of the lower bridge arm first switch. The second ends of the upper bridge arm second switch are respectively connected to the second end of the resistance measurement channel and the first end of the lower bridge arm second switch. The second ends of the lower bridge arm first switch and the lower bridge arm second switch are also connected. The controlled terminals of the upper bridge arm first switch, upper bridge arm second switch, lower bridge arm first switch, and lower bridge arm second switch are all electrically connected to the control circuit. The resistance measurement channel is also used to guide the current input through the second current transmission terminal into the resistor under test, and to guide the current of the resistor under test out through the first current transmission terminal of the resistance measurement channel.

9. The resistance measuring circuit as described in claim 8, characterized in that, The current switching circuit includes a constant current source circuit and a second reference resistor switching circuit. The first terminal of the constant current source circuit is connected to the second terminal of the first switch of the lower bridge arm and the second terminal of the second switch of the lower bridge arm, respectively. The resistance measurement circuit further includes a fourth polarity switching circuit, which includes an upper bridge arm third switch, an upper bridge arm fourth switch, a lower bridge arm third switch, and a lower bridge arm fourth switch. The first terminals of the upper bridge arm third switch and the upper bridge arm fourth switch are both connected to the second terminal of the constant current source circuit. The second terminal of the upper bridge arm third switch is connected to the first terminal of the second reference resistor switching circuit and the first terminal of the lower bridge arm third switch, respectively. The second terminal of the upper bridge arm fourth switch is connected to the second terminal of the second reference resistor switching circuit and the first terminal of the lower bridge arm fourth switch, respectively. The second terminals of the lower bridge arm third switch and the lower bridge arm fourth switch are both connected to a ground terminal. The controlled terminals of the upper bridge arm third switch, the upper bridge arm fourth switch, the lower bridge arm third switch, and the lower bridge arm fourth switch are all electrically connected to the control circuit.

10. A resistance measuring device, characterized in that, The device includes a probe assembly and a resistance measurement circuit as described in any one of claims 1 to 9, wherein the probe assembly is used to connect to both ends of the resistor to be measured, and the probe assembly is connected to the first current transmission terminal and the second terminal of the resistance measurement channel of the resistance measurement circuit.

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