Resistance measuring circuit, resistance measuring method and digital multimeter

Abstract

The present application discloses a resistance measurement circuit, a resistance measurement method and a digital multimeter. The resistance measurement circuit includes a constant voltage power supply circuit, a resistor array circuit, a current protection circuit and an analog-to-digital conversion circuit. The current protection circuit is used for overcurrent protection, the constant voltage power supply circuit is used to provide a constant voltage power supply, the resistor array circuit is used to select and connect a reference resistor with a known resistance value, and the analog-to-digital conversion circuit is used to obtain the voltage value at both ends of the resistor to be measured and the voltage value at both ends of the reference resistor with a known resistance value, and obtain the resistance value of the resistor to be measured according to the voltage value at both ends of the resistor to be measured, the resistance value of the reference resistor and the voltage value at both ends of the reference resistor. By using the voltage at both ends of the reference resistor as the reference voltage of the analog-to-digital converter, the measurement accuracy of the resistor to be measured is only related to the number of bits of the analog-to-digital converter and the resistance value accuracy of the reference resistor. Since the factors affecting the measurement accuracy are reduced, the measurement accuracy of the resistance value is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic instruments and meters, and in particular to a resistance measuring circuit, a resistance measuring method and a digital multimeter. Background Art

[0002] Digital multimeter is a commonly used instrument in electrical measurement technology. It combines the achievements of electronic technology, computing technology, automation technology and electrical measurement technology. It has become an indispensable instrument in modern measurement with its advantages such as convenient operation, accurate reading, compact size and convenient carrying. It can measure DC current, AC current, DC voltage, AC voltage, resistance, capacitance, forward voltage drop of diode, etc. It is replacing analog (i.e. pointer type) multimeter in many fields. It has the advantages of easy use, high sensitivity, fast measurement speed, wide range, strong overload capacity, high input impedance, objectivity of indication value (no visual error), strong expansion ability, etc. It is widely used in intelligent measurement fields such as electronic and electrical measurement, industrial automation instrumentation, automatic test system, etc., showing strong vitality. With the advancement of science and technology, the functions of digital multimeters are becoming more and more powerful, raising the measurement technology of electrical and non-electrical quantities to a new level. At present, the principle of measuring resistance by digital multimeter is based on Ohm's law. Generally, multimeter uses voltage division method to measure resistance. The resistance reading value is actually the current reading value. Since the electrical measurement accuracy is related to multiple factors of the measurement environment, the error between the measured value of resistance and the true value is large. Summary of the invention

[0003] The main technical problem solved by the present invention is how to improve the accuracy of resistance measurement.

[0004] According to a first aspect, the present invention provides a resistance measurement circuit for measuring the resistance value of a resistor to be measured, the resistance measurement circuit comprising a measurement positive connection terminal, a measurement negative connection terminal, a constant voltage power supply circuit, a resistor array circuit, a current protection circuit and an analog-to-digital conversion circuit;

[0005] The measuring positive connection terminal and the measuring negative connection terminal are used to be connected to two ends of the resistor to be measured respectively;

[0006] The current protection circuit is connected to the measurement positive connection terminal and the resistor bank circuit respectively; the current protection circuit is used to provide overcurrent protection for the resistance measurement circuit; the current protection circuit includes a first connection terminal and a second connection terminal, the first connection terminal of the current protection circuit is connected to the measurement positive connection terminal, and the second connection terminal of the current protection circuit is connected to the resistor bank circuit;

[0007] The constant voltage power supply circuit is connected to the resistor array circuit; the constant voltage power supply circuit is used to output constant voltage power to the resistor array circuit; the constant voltage power supply circuit includes a power input terminal and a power output terminal, the power input terminal is used to input a preset voltage source, and the power output terminal is connected to the resistor array circuit;

[0008] The resistor array circuit comprises a first connection end, a second connection end and at least one reference resistor, the first connection end of the resistor array circuit is connected to the power output end of the constant voltage power supply circuit, and the second connection end of the resistor array circuit is connected to the second connection end of the current protection circuit; the resistor array circuit is used to connect one of the reference resistors between the power output end of the constant voltage power supply circuit and the second connection end of the current protection circuit; wherein the resistance values ​​of any two of the reference resistors in the resistor array circuit are different;

[0009] The analog-to-digital conversion circuit is connected to the measurement positive connection terminal, the measurement negative connection terminal, the constant voltage power supply circuit, the resistor array circuit and the current protection circuit respectively; the analog-to-digital conversion circuit is used to obtain the voltage signal VINN of the measurement positive connection terminal, the voltage signal VINP of the measurement negative connection terminal, the voltage signal VREFP of the power output terminal and the voltage signal VREFN of the second connection terminal of the resistor array circuit, and obtain the resistance value of the resistor to be measured according to the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN and the resistance value of the reference resistor connected between the power output terminal of the constant voltage power supply circuit and the second connection terminal of the current protection circuit; the analog-to-digital conversion circuit includes a first connection terminal, a second connection terminal, a third connection terminal and a fourth connection terminal, the first connection terminal of the analog-to-digital conversion circuit is connected to the power output terminal of the constant voltage power supply circuit, the second connection terminal of the analog-to-digital conversion circuit is connected to the second connection terminal of the resistor array circuit, the third connection terminal of the analog-to-digital conversion circuit is connected to the measurement positive connection terminal, and the fourth connection terminal of the analog-to-digital conversion circuit is connected to the measurement negative connection terminal.

[0010] In one embodiment, the constant voltage power supply circuit includes an amplifier U1, the positive input terminal of the amplifier U1 is connected to the power input terminal of the constant voltage power supply circuit, and the negative input terminal of the amplifier U1 and the output terminal of the amplifier U1 are connected to the power output terminal of the constant voltage power supply circuit.

[0011] In one embodiment, the current protection circuit includes a diode, a resistor R PTC and / or fuses;

[0012] The positive connection end of the diode is connected to the second connection end of the resistor bank circuit, and the negative connection end of the diode is connected to the measurement positive connection end;

[0013] One end of the fuse is connected to the second connection end of the resistor bank circuit, and the other end is connected to the measurement positive connection end;

[0014] Resistor R PTC One end is connected to the second connection end of the resistor bank circuit, and the other end is connected to the measurement positive connection end.

[0015] In one embodiment, the resistor array circuit includes a single-pole multi-throw switch S1 and at least one reference resistor, the single-pole multi-throw switch S1 includes a fixed end and moving ends equal to the number of reference resistors; one end of each of the reference resistors is connected to the first connection end of the resistor array circuit, and the other end is connected to a moving end of the single-pole multi-throw switch S1; the fixed end of the single-pole multi-throw switch S1 is connected to the second connection end of the resistor array circuit; the single-pole multi-throw switch S1 is used to connect one of the reference resistors between the power output end of the constant voltage power supply circuit and the second connection end of the current protection circuit.

[0016] In one embodiment, the analog-to-digital conversion circuit includes an analog-to-digital converter, which is used to convert the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP and the voltage signal VREFN into ADC code word signals, and obtain the resistance value of the resistor to be measured based on the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN converted into ADC code word signals and the resistance value of the reference resistor connected between the power output end of the constant voltage power supply circuit and the second connection end of the current protection circuit.

[0017] In one embodiment, the analog-to-digital conversion circuit further includes a resistor R11 and a resistor R12; the resistor R11 is connected between the measurement positive connection terminal and the analog-to-digital converter; the resistor R12 is connected between the measurement negative connection terminal and the analog-to-digital converter.

[0018] In one embodiment, the analog-to-digital conversion circuit further includes a buffer A1, a buffer A2, a buffer A3 and a buffer A4; the buffer A1 is connected between a first connection terminal of the analog-to-digital conversion circuit and the analog-to-digital converter; the buffer A2 is connected between a second connection terminal of the analog-to-digital conversion circuit and the analog-to-digital converter; the buffer A3 is connected in series with a resistor R11, and after being connected in series, is connected between a third connection terminal of the analog-to-digital conversion circuit and the analog-to-digital converter; the buffer A4 is connected in series with a resistor R12, and after being connected in series, is connected between a fourth connection terminal of the analog-to-digital conversion circuit and the analog-to-digital converter.

[0019] According to a second aspect, the present invention provides a digital multimeter, comprising the resistance measuring circuit described in the first aspect.

[0020] According to a third aspect, the present invention provides a resistance measurement method, which is applied to the resistance measurement circuit described in the first aspect, wherein the resistance measurement circuit includes a measurement positive connection terminal, a measurement negative connection terminal, a constant voltage power supply circuit, a resistor array circuit, a current protection circuit, and an analog-to-digital conversion circuit, and the resistance measurement method includes:

[0021] Obtaining a resistance value of a reference resistor connected between a power supply output terminal of the constant voltage power supply circuit and a second connection terminal of the current protection circuit;

[0022] Obtaining a voltage signal VINN, a voltage signal VINP, a voltage signal VREFP, and a voltage signal VREFN;

[0023] Obtaining the resistance value of the resistor to be measured according to the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN and the resistance value of a reference resistor connected between the power output terminal of the constant voltage power supply circuit and the second connection terminal of the current protection circuit;

[0024] The resistance value of the resistor to be measured is obtained by the formula:

[0025] R DUT =V IN ÷V REF *Rn;

[0026] V IN =V INP -V INN ;

[0027] V REF =V REFP -V REFN ;

[0028] Among them, R DUT is the resistance value of the resistor to be measured, Rn is the resistance value of the reference resistor, V INP is the value of the voltage signal VINP, V INN is the value of the voltage signal VINN, V REFP is the value of the voltage signal VREFP, V REFN is the value of the voltage signal VREFN.

[0029] According to a fourth aspect, the present invention provides a computer-readable storage medium, characterized in that a program is stored on the medium, and the program can be executed by a processor to implement the resistance measurement method as described in the third aspect.

[0030] The digital multimeter provided in the above embodiment includes a resistance measurement circuit. The resistance measurement circuit uses the voltage across the reference resistor as the reference voltage of the analog-to-digital converter so that the measurement accuracy of the resistance to be measured is only related to the number of bits of the analog-to-digital converter and the resistance accuracy of the reference resistor. Since the factors affecting the measurement accuracy are greatly reduced, the measurement accuracy of the resistance is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A circuit connection diagram of a resistance measuring circuit of a digital multimeter in an embodiment;

[0032] Figure 2 A circuit connection diagram of a resistance measurement circuit in another embodiment;

[0033] Figure 3 FIG. 4 is a flow chart of a resistance measurement method in another embodiment. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are for making the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different situations, or can be replaced by other elements, materials, methods. In some cases, some operations related to the present application are not shown or described in the specification, this is to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations according to the description in the specification and the general technical knowledge in the art.

[0035] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and are not meant to be a required sequence, unless otherwise specified that a certain sequence must be followed.

[0036] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0037] Please refer to Figure 1, is a circuit connection diagram of a resistance measurement circuit of a digital multimeter in an embodiment, including a voltage source VCC (generally provided by a multimeter battery), a resistor bank including a plurality of reference resistors with different resistance values ​​(resistors R1 to R6), a resistor to be measured R_DUT, an analog-to-digital converter, and an analog-to-digital converter reference voltage source Vref. Figure 1 As shown in the figure, the resistance calculation formula of the resistor to be measured R_DUT is:

[0038] V R_DUT / (VCC- V R_DUT ) = R_DUT / R3;

[0039] V R_DUT It is the voltage across the resistor R_DUT, which can be obtained by sampling the analog-to-digital converter. Its value is calculated as follows:

[0040] V R_DUT =ADC_CODE / ADC_FULLCODE*Vref;

[0041] Among them, ADC_CODE is the code word obtained by the analog-to-digital converter, ADC_FULLCODE is the code word corresponding to the full scale of the analog-to-digital converter, and Vref is the reference voltage of the analog-to-digital converter, also called the full-scale voltage.

[0042] According to the above two calculation formulas, the resistance calculation formula of the resistor to be measured R_DUT can be converted into:

[0043] R_DUT=1 / (VCC / (ADC_CODE / ADC_FULLCODE*Vref)-1)*R3;

[0044] Among them, ADC_CODE is a variable, and the voltage source VCC, full-scale voltage Vref, code word ADC_FULLCODE of the analog-to-digital converter and resistor R3 are known quantities. However, among the known quantities, except for the code word ADC_FULLCODE of the analog-to-digital converter, which is a digital value, the others are analog values, which have errors and are affected by the environment. Therefore, the accuracy of the resistance to be measured R_DUT is at least determined by the number of bits of the analog-to-digital converter, the voltage source VCC, the full-scale voltage Vref and the resistor R3. Due to too many influencing factors, the accuracy of the resistance measurement is not high.

[0045] The resistance measurement circuit in the embodiment of the present application uses the voltage across the reference resistor as the reference voltage of the analog-to-digital converter, so that the measurement accuracy of the resistance to be measured is only related to the number of bits of the analog-to-digital converter and the resistance accuracy of the reference resistor. Since the factors affecting the measurement accuracy are reduced, the measurement accuracy of the resistance is greatly improved.

[0046] The technical solution of the present application will be described in detail below with reference to embodiments.

[0047] Embodiment 1

[0048] Please refer to Figure 2 , is a circuit connection diagram of a resistance measurement circuit in another embodiment, wherein the resistance measurement circuit 100 is used to measure the resistance value of the resistance to be measured R_DUT. The resistance measurement circuit 100 includes a measurement positive connection terminal, a measurement negative connection terminal, a constant voltage power supply circuit 20, a resistance row circuit 40, a current protection circuit 30 and an analog-to-digital conversion circuit 10. The measurement positive connection terminal and the measurement negative connection terminal are used to be connected to the two ends of the resistance to be measured R_DUT, respectively. The current protection circuit 30 is connected to the measurement positive connection terminal and the resistance row circuit 40, respectively, and the current protection circuit 30 is used to provide overcurrent protection for the resistance measurement circuit 100. The current protection circuit 30 includes a first connection terminal and a second connection terminal, the first connection terminal of the current protection circuit 30 is connected to the measurement positive connection terminal, and the second connection terminal of the current protection circuit 30 is connected to the resistance row circuit 40. The constant voltage power supply circuit 20 is connected to the resistance row circuit 40, and the constant voltage power supply circuit 20 is used to output a constant voltage power supply VREFP to the resistance row circuit 40. The constant voltage power supply circuit 20 includes a power input terminal and a power output terminal. The power input terminal is used for inputting a preset voltage source VREFO, and the power output terminal is connected to the resistor array circuit 40. The resistor array circuit 40 includes a first connection terminal, a second connection terminal and at least one reference resistor. The first connection terminal of the resistor array circuit 40 is connected to the power output terminal of the constant voltage power supply circuit 20, and the second connection terminal of the resistor array circuit 40 is connected to the second connection terminal of the current protection circuit 30. The resistor array circuit 40 is used to connect a reference resistor between the power output terminal of the constant voltage power supply circuit 20 and the second connection terminal of the current protection circuit 30. Among them, the resistance values ​​of any two reference resistors in the resistor array circuit 40 are different. The analog-to-digital conversion circuit 10 is respectively connected to the measuring positive connection terminal, the measuring negative connection terminal, the constant voltage power supply circuit 20, the resistor array circuit 40 and the current protection circuit 30. The analog-to-digital conversion circuit 10 is used to obtain the voltage signal VINN of the measuring positive connection terminal, the voltage signal VINP of the measuring negative connection terminal, the voltage signal VREFP of the power output terminal and the voltage signal VREFN of the second connection terminal of the resistor array circuit, and obtain the resistance value of the resistor to be measured R_DUT according to the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN and the resistance value of the reference resistor connected between the power output terminal of the constant voltage power supply circuit 20 and the second connection terminal of the current protection circuit 30. The analog-to-digital conversion circuit 10 includes a first connection terminal, a second connection terminal, a third connection terminal and a fourth connection terminal. The first connection terminal of the analog-to-digital conversion circuit 10 is connected to the power output terminal of the constant voltage power supply circuit 20, the second connection terminal of the analog-to-digital conversion circuit 10 is connected to the second connection terminal of the resistor array circuit 40, the third connection terminal of the analog-to-digital conversion circuit 10 is connected to the measurement positive connection terminal, and the fourth connection terminal of the analog-to-digital conversion circuit 10 is connected to the measurement negative connection terminal.

[0049] In one embodiment, the constant voltage power supply circuit 20 includes an amplifier U1, a positive input terminal of the amplifier U1 is connected to a power input terminal of the constant voltage power supply circuit 20, and a negative input terminal of the amplifier U1 and an output terminal of the amplifier U1 are connected to a power output terminal of the constant voltage power supply circuit 20. In one embodiment, the model of the amplifier U1 is CA082. In one embodiment, the preset voltage source VREFO is provided by a battery of a digital multimeter.

[0050] In one embodiment, the current protection circuit 30 includes a diode, the positive connection end of the diode is connected to the second connection end of the resistor array circuit 30, and the negative connection end of the diode is connected to the measurement positive connection end. In one embodiment, the current protection circuit 30 includes a fuse, one end of the fuse is connected to the second connection end of the resistor array circuit 30, and the other end is connected to the measurement positive connection end. In one embodiment, the current protection circuit 30 includes a resistor R PTC , resistor R PTC One end of is connected to the second connection end of the resistor bank circuit 40, and the other end is connected to the measurement positive connection end.

[0051] In one embodiment, the resistor array circuit 40 includes a single-pole multi-throw switch S1 and at least one reference resistor, the single-pole multi-throw switch S1 includes a fixed end and a movable end equal to the number of reference resistors, one end of each reference resistor is connected to the first connection end of the resistor array circuit 40, and the other end is connected to a movable end of the single-pole multi-throw switch S1. The fixed end of the single-pole multi-throw switch S1 is connected to the second connection end of the resistor array circuit 40, and the single-pole multi-throw switch S1 is used to connect a reference resistor between the power output end of the constant voltage power supply circuit 20 and the second connection end of the current protection circuit 30. In one embodiment, the reference resistor includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5 and / or a resistor R6; wherein the resistance values ​​of the resistor R1, the resistor R2, the resistor R3, the resistor R4, the resistor R5 and the resistor R6 are 100Ω, 1KΩ, 10KΩ, 100KΩ, 1MΩ and 10MΩ respectively.

[0052] In one embodiment, the analog-to-digital conversion circuit 10 includes an analog-to-digital converter, which is used to convert the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP and the voltage signal VREFN into ADC code word signals, and obtain the resistance value of the resistor to be measured R_DUT based on the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN converted into the ADC code word signals and the resistance value of the reference resistor connected between the power output end of the constant voltage power supply circuit 20 and the second connection end of the current protection circuit 30.

[0053] In one embodiment, the analog-to-digital conversion circuit 10 further includes a resistor R11 and a resistor R12, wherein the resistor R11 is connected between the measurement positive connection terminal and the analog-to-digital converter, and the resistor R12 is connected between the measurement negative connection terminal and the analog-to-digital converter. In one embodiment, the analog-to-digital conversion circuit further includes a buffer A1, a buffer A2, a buffer A3, and a buffer A4, wherein the buffer A1 is connected between the first connection terminal of the analog-to-digital conversion circuit and the analog-to-digital converter, the buffer A2 is connected between the second connection terminal of the analog-to-digital conversion circuit and the analog-to-digital converter, the buffer A3 is connected in series with the resistor R11, and then connected between the third connection terminal of the analog-to-digital conversion circuit and the analog-to-digital converter, and the buffer A4 is connected in series with the resistor R12, and then connected between the fourth connection terminal of the analog-to-digital conversion circuit and the analog-to-digital converter.

[0054] In one embodiment, the present application also discloses a digital multimeter, including the resistance measuring circuit as described above, such as Figure 2 As shown, in this embodiment, the voltage signal VINN and the voltage signal VINP obtained by the analog-to-digital converter are inputs of the first differential voltage, and the differential value thereof is:

[0055] VIN=VINP-VINN;

[0056] The voltage signal VREFP and the voltage signal VREFN obtained by the analog-to-digital converter are inputs of the second differential voltage, and the differential value thereof is:

[0057] VREF=VREFP-VREFN;

[0058] According to the measurement principle of modulus:

[0059] VIN=ADC_CODE÷ADC_FULLCODE*VREF; (1)

[0060] Among them, ADC_CODE is the ADC codeword obtained by the analog-to-digital converter, and ADC_FULLCODE is the codeword corresponding to the full scale of the analog-to-digital converter (for example, for an 8-bit ADC, ADC_FULLCODE=2^8-1=255). Because the input impedance of the analog-to-digital converter is not very high. Generally less than 1MΩ, when the peripheral is a large resistor, it will affect the measurement result, so a buffer is added to all input ends of the analog-to-digital converter to increase the input impedance. The function of amplifier U1 is a constant voltage source. According to the virtual short principle of the operational amplifier, the voltages of the three pins of amplifier U1 are equal, so as long as the preset voltage source VREF0 is kept constant, the voltages of the other two pins of amplifier U1 are also kept constant. Resistors R1, R2, R3, R4, R5 and / or R6 are high-precision reference resistors, which are connected to one of the selection pins of the single-pole multi-throw switch S1. The common end (top) of the single-pole multi-throw switch S1 is connected to resistor R PTC, mainly to protect the multimeter from being damaged by high voltage, the resistor R PTC Under low current conditions, the resistance is constant, generally around 1.5KΩ, and increases under high current conditions. PTC Connect the positive input terminal of the digital multimeter, the resistor R_DUT is the resistor to be measured, and the resistor R_DUT is connected between the measurement positive connection terminal and the measurement negative connection terminal.

[0061] For example, the resistor R_DUT is about 500Ω, and the single-pole multi-throw switch S1 connects the resistor R3. According to Ohm's law:

[0062] I R_DUT =I R3 ; (2)

[0063] V R_DUT = I R_DUT *R_DUT = V R3 ÷R3*R_DUT; (3)

[0064] After transforming formula (3), we get the following formula:

[0065] R_DUT =V R_DUT ÷V R3 *R3; (4)

[0066] Among them, the voltage V across R3 R3 is equal to the second differential voltage VREF, and the voltage VR_DUT across R_DUT is equal to the first differential voltage VIN, that is:

[0067] V R3 =VREFP-VREFN=VREF; (5)

[0068] VR_DUT=VINP-VINN=VIN; (6)

[0069] Substituting formula (5) and (6) into formula (4) yields the following formula:

[0070] R_DUT=V R_DUT ÷V R3 *R3= VIN÷VREF*R3; (7)

[0071] The following formula is obtained from formula (1) and formula (7):

[0072] R_DUT= VIN÷VREF*R3= ADC_CODE÷ADC_FULLCODE*R3 (8)

[0073] Among them, ADC_CODE is a variable, ADC_FULLCODE is a known digital value, and R3 is the known value of the reference resistor. Therefore, as long as the accuracy of the resistor R3 is controlled, the measurement accuracy of the resistor below 1KΩ can be guaranteed. By expanding formula (8), we can get:

[0074] R_DUT= ADC_CODE÷ADC_FULLCODE*Rn;

[0075] Among them, Rn is the reference resistance, which is selected by the user by controlling the single-pole multi-throw switch S1 according to different measurement ranges.

[0076] The resistance measurement circuit disclosed in this embodiment includes a constant voltage power supply circuit, a resistor array circuit, a current protection circuit and an analog-to-digital conversion circuit, wherein the current protection circuit is used for overcurrent protection, the constant voltage power supply circuit is used for providing a constant voltage power supply, the resistor array circuit is used for selecting and connecting a reference resistor with a known resistance value, and the analog-to-digital conversion circuit is used for obtaining the voltage value across the resistor to be measured and the voltage value across the reference resistor with a known resistance value, and obtaining the resistance value of the resistor to be measured based on the voltage value across the resistor to be measured, the resistance value of the reference resistor and the voltage value across the reference resistor. By using the voltage across the reference resistor as the reference voltage of the analog-to-digital converter, the measurement accuracy of the resistor to be measured is only related to the number of bits of the analog-to-digital converter and the resistance value accuracy of the reference resistor, and the factors affecting the measurement accuracy are reduced, thereby greatly improving the measurement accuracy of the resistance value.

[0077] Embodiment 2

[0078] Please refer to Figure 3 , is a flow chart of a resistance measurement method in another embodiment, the resistance measurement method is applied to the resistance measurement circuit as described in the first embodiment, the resistance measurement circuit includes a measurement positive connection terminal, a measurement negative connection terminal, a constant voltage power supply circuit, a resistance row circuit, a current protection circuit and an analog-to-digital conversion circuit, the resistance measurement method includes:

[0079] Step 101, obtaining the resistance value of a reference resistor.

[0080] The resistance value of a reference resistor connected between a power supply output terminal of the constant voltage power supply circuit and a second connection terminal of the current protection circuit is obtained.

[0081] Step 102: Acquire a voltage signal of a resistance measurement circuit.

[0082] A voltage signal VINN, a voltage signal VINP, a voltage signal VREFP, and a voltage signal VREFN are obtained.

[0083] Step 103, obtaining the resistance value of the resistor to be measured.

[0084] The resistance value of the resistor to be measured is obtained according to the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN and the resistance value of the reference resistor connected between the power output terminal of the constant voltage power supply circuit and the second connection terminal of the current protection circuit, wherein the resistance value of the resistor to be measured is obtained by the formula:

[0085] R DUT =V IN ÷V REF *Rn;

[0086] V IN =V INP -V INN ;

[0087] V REF =V REFP -V REFN ;

[0088] Among them, R DUT is the resistance value of the resistor to be measured, Rn is the resistance value of the reference resistor, V INP is the value of the voltage signal VINP, V INN is the value of the voltage signal VINN, V REFP is the value of the voltage signal VREFP, V REFN is the value of the voltage signal VREFN.

[0089] Those skilled in the art will appreciate that all or part of the functions of the various methods in the above-mentioned embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, and the storage medium can include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to implement the above-mentioned functions. For example, the program is stored in the memory of the device, and when the program in the memory is executed by the processor, all or part of the above-mentioned functions can be implemented. In addition, when all or part of the functions in the above-mentioned embodiments are implemented by computer programs, the program can also be stored in a storage medium such as a server, another computer, disk, optical disk, flash disk or mobile hard disk, and can be downloaded or copied and saved in the memory of the local device, or the system of the local device is updated, and when the program in the memory is executed by the processor, all or part of the functions in the above-mentioned embodiments can be implemented.

[0090] The above specific examples are used to illustrate the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the art, according to the concept of the present invention, some simple deductions, modifications or substitutions can be made.

Claims

1. A resistance measuring circuit for measuring the resistance value of a resistor to be measured, characterized in that: It includes a measuring positive connection terminal, a measuring negative connection terminal, a constant voltage power supply circuit, a resistor array circuit, a current protection circuit and an analog-to-digital conversion circuit; The measuring positive connection terminal and the measuring negative connection terminal are used to be connected to two ends of the resistor to be measured respectively; The current protection circuit is connected to the measurement positive connection terminal and the resistor bank circuit respectively; the current protection circuit is used to provide overcurrent protection for the resistance measurement circuit; the current protection circuit includes a first connection terminal and a second connection terminal, the first connection terminal of the current protection circuit is connected to the measurement positive connection terminal, and the second connection terminal of the current protection circuit is connected to the resistor bank circuit; The constant voltage power supply circuit is connected to the resistor array circuit; the constant voltage power supply circuit is used to output constant voltage power to the resistor array circuit; the constant voltage power supply circuit includes a power input terminal and a power output terminal, the power input terminal is used to input a preset voltage source, and the power output terminal is connected to the resistor array circuit; The resistor array circuit comprises a first connection end, a second connection end and at least one reference resistor, the first connection end of the resistor array circuit is connected to the power output end of the constant voltage power supply circuit, and the second connection end of the resistor array circuit is connected to the second connection end of the current protection circuit; the resistor array circuit is used to connect one of the reference resistors between the power output end of the constant voltage power supply circuit and the second connection end of the current protection circuit; wherein the resistance values ​​of any two of the reference resistors in the resistor array circuit are different; The analog-to-digital conversion circuit is connected to the measurement positive connection terminal, the measurement negative connection terminal, the constant voltage power supply circuit, the resistor array circuit and the current protection circuit respectively; the analog-to-digital conversion circuit is used to obtain the voltage signal VINN of the measurement positive connection terminal, the voltage signal VINP of the measurement negative connection terminal, the voltage signal VREFP of the power output terminal and the voltage signal VREFN of the second connection terminal of the resistor array circuit, and obtain the resistance value of the resistor to be measured according to the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN and the resistance value of the reference resistor connected between the power output terminal of the constant voltage power supply circuit and the second connection terminal of the current protection circuit; the analog-to-digital conversion circuit includes a first connection terminal, a second connection terminal, a third connection terminal and a fourth connection terminal, the first connection terminal of the analog-to-digital conversion circuit is connected to the power output terminal of the constant voltage power supply circuit, the second connection terminal of the analog-to-digital conversion circuit is connected to the second connection terminal of the resistor array circuit, the third connection terminal of the analog-to-digital conversion circuit is connected to the measurement positive connection terminal, and the fourth connection terminal of the analog-to-digital conversion circuit is connected to the measurement negative connection terminal.

2. The resistance measuring circuit according to claim 1, characterized in that: The constant voltage power supply circuit comprises an amplifier U1, a positive input terminal of the amplifier U1 is connected to a power input terminal of the constant voltage power supply circuit, and a negative input terminal of the amplifier U1 and an output terminal of the amplifier U1 are connected to a power output terminal of the constant voltage power supply circuit.

3. The resistance measuring circuit according to claim 1, characterized in that: The current protection circuit includes a diode, a resistor R PTC and / or fuses; The positive connection end of the diode is connected to the second connection end of the resistor bank circuit, and the negative connection end of the diode is connected to the measurement positive connection end; One end of the fuse is connected to the second connection end of the resistor bank circuit, and the other end is connected to the measurement positive connection end; Resistor R PTC One end is connected to the second connection end of the resistor bank circuit, and the other end is connected to the measurement positive connection end.

4. The resistance measuring circuit according to claim 1, wherein: The resistor array circuit includes a single-pole multi-throw switch S1 and at least one reference resistor, the single-pole multi-throw switch S1 includes a fixed end and moving ends equal in number to the reference resistors; one end of each of the reference resistors is connected to the first connection end of the resistor array circuit, and the other end is connected to a moving end of the single-pole multi-throw switch S1; the fixed end of the single-pole multi-throw switch S1 is connected to the second connection end of the resistor array circuit; the single-pole multi-throw switch S1 is used to connect one of the reference resistors between the power output end of the constant voltage power supply circuit and the second connection end of the current protection circuit.

5. The resistance measuring circuit according to claim 1, wherein: The analog-to-digital conversion circuit includes an analog-to-digital converter, which is used to convert the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP and the voltage signal VREFN into ADC code word signals, and obtain the resistance value of the resistor to be measured based on the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN converted into ADC code word signals and the resistance value of the reference resistor connected between the power output end of the constant voltage power supply circuit and the second connection end of the current protection circuit.

6. The resistance measuring circuit according to claim 5, characterized in that: The analog-to-digital conversion circuit further includes a resistor R11 and a resistor R12; the resistor R11 is connected between the measurement positive connection terminal and the analog-to-digital converter; the resistor R12 is connected between the measurement negative connection terminal and the analog-to-digital converter.

7. The resistance measuring circuit according to claim 6, characterized in that: The analog-to-digital conversion circuit also includes a buffer A1, a buffer A2, a buffer A3 and a buffer A4; the buffer A1 is connected between the first connection end of the analog-to-digital conversion circuit and the analog-to-digital converter; the buffer A2 is connected between the second connection end of the analog-to-digital conversion circuit and the analog-to-digital converter; the buffer A3 is connected in series with a resistor R11, and is connected between the third connection end of the analog-to-digital conversion circuit and the analog-to-digital converter after being connected in series; the buffer A4 is connected in series with a resistor R12, and is connected between the fourth connection end of the analog-to-digital conversion circuit and the analog-to-digital converter after being connected in series.

8. A digital multimeter, characterized in that: The method comprises the resistance measuring circuit as claimed in any one of claims 1 to 7.

9. A method for measuring resistance, characterized in that: Applied to the resistance measurement circuit according to any one of claims 1 to 7, the resistance measurement circuit comprises a measurement positive connection terminal, a measurement negative connection terminal, a constant voltage power supply circuit, a resistor array circuit, a current protection circuit and an analog-to-digital conversion circuit, and the resistance measurement method comprises: Obtaining a resistance value of a reference resistor connected between a power supply output terminal of the constant voltage power supply circuit and a second connection terminal of the current protection circuit; Obtaining a voltage signal VINN, a voltage signal VINP, a voltage signal VREFP, and a voltage signal VREFN; Obtaining the resistance value of the resistor to be measured according to the voltage signal VINN, the voltage signal VINP, the voltage signal VREFP, the voltage signal VREFN and the resistance value of a reference resistor connected between the power output terminal of the constant voltage power supply circuit and the second connection terminal of the current protection circuit; The resistance value of the resistor to be measured is obtained by the formula: R DUT =V IN ÷V REF *Rn; V IN =V INP -V INN ; V REF =V REFP -V REFN ; Among them, R DUT is the resistance value of the resistor to be measured, Rn is the resistance value of the reference resistor, V INP is the value of the voltage signal VINP, V INN is the value of the voltage signal VINN, V REFP is the value of the voltage signal VREFP, V REFN is the value of the voltage signal VREFN, V IN is the difference between the voltage signal VINN and the voltage signal VINP.

10. A computer-readable storage medium, characterized in that: The medium stores a program, which can be executed by a processor to implement the resistance measurement method as claimed in claim 9.

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