Real-time measuring circuit and measuring method for milliohm-level resistor

Abstract

The invention discloses a milliohm-level resistance real-time measuring circuit which comprises a power supply circuit, a voltage division circuit, an operational amplifier circuit, a lifting circuit, an ADC acquisition module, an MCU and an LED display screen which are sequentially connected in series, the MCU is connected with the power supply circuit through a relay switch circuit, and the power supply circuit is connected with the voltage division circuit through a current mutual inductance circuit. The invention also discloses a milliohm-level resistor real-time measurement method, which comprises the following steps of: utilizing the measurement circuit, performing wiring measurement on the measured resistor by adopting a four-wire method, controlling the relay by the MCU to circularly switch on power supply in real time, performing voltage division, operational amplification and lifting processing on a signal, then performing segmented acquisition, performing effective acquisition value judgment and A / D conversion by the MCU, and finally displaying a calculated resistance value on the LED display screen. The invention belongs to the technical field of circuit measurement, adopts segmented acquisition, is high in acquisition precision and high in stability, and can continuously and circularly measure in real time for a long time as a relay is switched on for power supply at regular time.

Description

Technical Field

[0001] The invention belongs to the technical field of circuit measurement, and relates to a milliohm-level resistance real-time measurement circuit. The invention also relates to a milliohm-level resistance real-time measurement method. Background Art

[0002] In engineering applications, it is often necessary to accurately measure various types of small contact resistances in real time, such as slip ring carbon brushes, high current switches, contact resistance of terminal blocks and other devices, with resistance values ​​ranging from 0 to 1000mΩ. Changes in resistance values ​​have a great impact on the current carrying capacity of the equipment. If the resistance value is too large, the current carrying capacity will be reduced. Therefore, long-term continuous circulation and real-time monitoring are required. When the resistance value is too large, timely reminders and maintenance should be carried out.

[0003] At present, milliohm meters are generally used to measure small resistors. They mainly use the bridge principle and Kelvin principle. A constant current is applied across the resistor to be measured, and then the voltage across the resistor is measured to calculate the resistance value according to Ohm's law. Although the milliohm meter has a simple measurement method, the display resolution of resistance values ​​in different ranges is obviously different, such as: the resolution of 0-9mΩ is 0.001mΩ, the resolution of 10-99mΩ is 0.01mΩ, and the resolution of 100-999mΩ is 0.1mΩ, resulting in a decrease in displayed accuracy. In addition, the power consumption is large when measuring milliohm-level small resistors, and it is mostly used for single measurements, which is not convenient for on-site long-term continuous cycle real-time measurement. Summary of the invention

[0004] The purpose of the present invention is to provide a milliohm-level resistance real-time measurement circuit, which solves the problem that when a milliohm meter is used to measure a small resistance in the prior art, the measurement accuracy is not accurate and the real-time measurement cannot be continuously cycled for a long time.

[0005] Another object of the present invention is to provide a real-time measurement method for milliohm resistance, which solves the problem of insufficient measurement accuracy when using a milliohm meter in the prior art.

[0006] The technical solution adopted by the present invention is a real-time measurement circuit of milliohm resistance, which includes a power supply circuit, a voltage divider circuit, an operational amplifier circuit, a lifting circuit, an ADC acquisition module, an MCU, and an LED display screen connected in series in sequence. The MCU is connected to the power supply circuit through a relay switch circuit, and the power supply circuit is connected to the voltage divider circuit through a current mutual inductance circuit.

[0007] Another technical solution adopted by the present invention is a real-time measurement method of milliohm resistance, which is implemented by using the above-mentioned real-time measurement circuit of milliohm resistance according to the following steps: Step 1, using the four-wire method to connect the measured resistor Rx, the MCU controls the relay switch circuit to cycle on and off the power supply in real time, obtains the current I1 and the terminal voltage V1 flowing through the measured resistor Rx, and converts the current I1 into the voltage V2; Step 2, simultaneously performing voltage division processing and operational amplifier processing on the voltage V1 and the voltage V2 respectively; Step 3: The signal after the voltage divider operational amplifier is raised for collection by the ADC acquisition module; Step 4: The ADC acquisition module acquires the AC voltage signal, transmits the acquired signal to the MCU for processing, and finally displays it in real time through the LED display.

[0008] The beneficial effects of the present invention include the following aspects: 1) Segmented acquisition is adopted, and the current and terminal voltage flowing through the measured resistor are segmentedly acquired according to different range values ​​of the measured resistor, thereby improving the acquisition accuracy, and the full-scale resolution is 0.001mΩ, which is better than the resolution and measurement accuracy displayed by the conventional milliohm meter. 2) The power supply of the measured resistor is opened at a fixed time through the relay switch circuit, and the real-time measurement can be continuously cycled for a long time, which is better than the single measurement of the conventional milliohm meter. 3) The four-wire method is adopted for measurement, which eliminates the influence of the resistance of the measuring line itself on the acquisition accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a structural block diagram of the milliohm resistance real-time measurement circuit of the present invention; Figure 2 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 1 ; Figure 3 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 2 ; Figure 4 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 3 ; Figure 5 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 4 ; Figure 6 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 5 ; Figure 7 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 6 ; Figure 8 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 7 ; Fig. 9 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 8 ; Fig.10 This is part of the principle of the milliohm resistance real-time measurement circuit of the present invention. Figure 9 ; Fig.11 The present invention is a four-wire measurement wiring diagram of a milliohm-level resistance real-time measurement circuit.

[0010] In the figure, 101. power supply circuit, 102. relay switch circuit, 103. current mutual induction circuit, 104. voltage divider circuit, 105. operational amplifier circuit, 106. lifting circuit, 107. ADC acquisition module, 108. MCU, 109. LED display; in addition, 1041, 1042, 1043, 1044, 1045, 1046, 1047, 1048 are eight unit voltage divider circuits, 1051, 1052, 1053, 1054, 1055, 1056, 1057, 1058 are eight unit operational amplifier circuits, and 1061, 1062, 1063, 1064, 1065, 1066, 1067, 1068 are eight unit lifting circuits. DETAILED DESCRIPTION

[0011] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0012] Reference Figure 1 The milliohm resistance real-time measurement circuit of the present invention has a structure that includes a power supply circuit 101, a voltage divider circuit 104, an operational amplifier circuit 105, a lifting circuit 106, an ADC acquisition module 107, an MCU 108, and an LED display screen 109, which are connected in series in sequence. The MCU 108 is connected to the power supply circuit 101 through the relay switch circuit 102, and the power supply circuit 101 is connected to the voltage divider circuit 104 through the current mutual induction circuit 103; Among them, the power supply circuit 101 corresponds to Figure 2 The dotted box 101 part; Relay switch circuit 102 corresponds to Figure 2 The dotted line frame 102 portion; The current mutual inductance circuit 103 corresponds to Figure 2 The dotted line frame 103 part; The eight unit voltage divider circuits of the voltage divider circuit 104 correspond to Figure 3 The dotted line frame 1041 part, Figure 4 The dotted line box 1042 part, Figure 5 The dotted line box 1043 part, Figure 6 The dotted box 1044 in Figure 7 The dotted line frame 1045 part, Figure 8 The dotted box 1046 part, Fig. 9 The dotted box 1047 part, Fig.10 The dotted box 1048 part; The eight unit operational amplifier circuits of the operational amplifier circuit 105 correspond to Figure 3The dotted line frame 1051 part, Figure 4 The dotted box 1052 part, Figure 5 The dotted box 1053 part, Figure 6 The dotted line box 1054 part, Figure 7 The dotted line box 1055 part, Figure 8 The dotted box 1056 part, Fig. 9 The dotted line box 1057 part, Fig.10 The dotted box 1058 part; The eight unit lifting circuits of the lifting circuit 106 correspond to Figure 3 The dotted line frame 1061 part, Figure 4 The dotted box 1062 part, Figure 5 The dotted line box 1063 part, Figure 6 The dotted box 1064 part, Figure 7 The dotted line frame 1065 part, Figure 8 The dotted line box 1066 part, Fig. 9 The dotted box 1067 part, Fig.10 The dotted box 1068 part.

[0013] The internal structure, interconnection relationship and functions of the aforementioned circuits are described as follows: 1) Power supply circuit 101 (see Figure 2 ), the structure is that the "+" of the constant AC voltage source U is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the 1st pin of the relay K1 in the relay switch circuit 102, and the "-" of the constant AC voltage source U is connected to the 2nd pin of the transformer T1 in the current mutual inductance circuit 103. The power supply circuit 101 is used to provide a constant AC voltage input to the measured resistor.

[0014] 2) Relay switch circuit 102 (see Figure 2 ), the structure is that the 4th foot of the relay K1 is connected to the reference source VCC1, the 1st foot of the relay K1 is connected to the resistor R1 in the power supply circuit 101, and the 2nd foot of the relay K1 is connected to one end of the measured resistor Rx ( Figure 2 The upper end) is connected, the 3rd pin of the relay K1 is connected to the 1st pin of the transistor Q1; the 2nd pin of the transistor Q1 is connected to the control signal K through the resistor R4, the 2nd pin of the transistor Q1 is also connected to the 3rd pin of the transistor Q1 through the resistor R3, and the 3rd pin of the transistor Q1 is grounded. The relay switch circuit 102 is used to turn on and off the power supply circuit of the measured resistor, and is controlled by the MCU. When the control signal K is at a high level, the 1st and 3rd pins of the transistor Q1 are turned on, and the 1st and 2nd pins of the control relay K1 are connected, and the power supply circuit is turned on; when the control signal K is at a low level, the 1st and 3rd pins of the transistor Q1 are turned off, and the 1st and 2nd pins of the control relay K1 are disconnected, and the power supply circuit is turned off.

[0015] 3) Current mutual induction circuit 103 (see Figure 2 ), which is used to scale the current flowing through the measured resistor Rx, and then convert it into the terminal voltage V2, and use the "output terminal V2+" and "output terminal V2-" to complete the output. The structure is that the 1st pin of the transformer T1 is connected to the other end of the measured resistor Rx ( Figure 2 The 2nd pin of the transformer T1 is connected to the “-” of the constant AC voltage source U in the power supply circuit 101, and the 3rd pin of the transformer T1 is connected to the cathode of the diode D1, the anode of the diode D2, and one end of the resistor R2 ( Figure 2 The right end), the output end V2+ are connected at the same time, the 4th foot of the transformer T1 is connected to the positive electrode of the diode D1, the negative electrode of the diode D2, and the other end of the resistor R2 ( Figure 2 Left end), output terminal V2- are connected at the same time.

[0016] 4) The voltage divider circuit 104 includes eight unit voltage divider circuits with the same structure. The voltage divider circuit 104 is used for voltage division processing of the terminal voltage V1 of the measured resistor Rx and the voltage V2 after current conversion. Among them, the unit voltage divider circuit 1041 (see Figure 3 ), the structure is that resistors R5 and R6 are connected in series between the terminal voltage V1+ and the terminal voltage V1-, the connection node between the resistors R5 and R6 is connected to the 3rd pin of the operational amplifier U1 in the unit operational amplifier circuit 1051, and the terminal voltage V1- is connected to the end of the resistor R7 in the unit operational amplifier circuit 1051 ( Figure 3 The lower end of the device is connected to the ground with the terminal voltage V1- at the same time; Unit voltage divider circuit 1042 (see Figure 4 ), the structure is that the resistor R11 and the resistor R12 are connected in series between the terminal voltage V1+ and the terminal voltage V1-, the connection node between the resistor R11 and the resistor R12 is connected to the 3rd pin of the operational amplifier U2 in the unit operational amplifier circuit 1052, and the terminal voltage V1- is connected to the end of the resistor R13 in the unit operational amplifier circuit 1052 ( Figure 4 The lower end of the device is connected to the ground with the terminal voltage V1- at the same time; Unit voltage divider circuit 1043 (see Figure 5 ), the structure is that resistors R17 and R18 are connected in series between the terminal voltage V1+ and the terminal voltage V1-, the connection node between the resistors R17 and R18 is connected to the 3rd pin of the operational amplifier U3 in the unit operational amplifier circuit 1053, and the terminal voltage V1- is connected to the end of the resistor R19 in the unit operational amplifier circuit 1053 ( Figure 5 The lower end of the device is connected to the ground with the terminal voltage V1- at the same time; Unit voltage divider circuit 1044 (see Figure 6), the structure is that resistors R23 and R24 are connected in series between the terminal voltage V1+ and the terminal voltage V1-, the connection node between the resistors R23 and R24 is connected to the 3rd pin of the operational amplifier U4 in the unit operational amplifier circuit 1054, and the terminal voltage V1- is connected to the end of the resistor R25 in the unit operational amplifier circuit 1054 ( Figure 6 The lower end of the device is connected to the ground with the terminal voltage V1- at the same time; Unit voltage divider circuit 1045 (see Figure 7 ), the structure is that resistors R29 and R30 are connected in series between the terminal voltage V1+ and the terminal voltage V1-, the connection node between the resistors R29 and R30 is connected to the 3rd pin of the operational amplifier U5 in the unit operational amplifier circuit 1055, and the terminal voltage V1- is connected to the end of the resistor R31 in the unit operational amplifier circuit 1055 ( Figure 7 The lower end of the device is connected to the ground with the terminal voltage V1- at the same time; Unit voltage divider circuit 1046 (see Figure 8 ), the structure is that the resistor R35 and the resistor R36 are connected in series between the terminal voltage V1+ and the terminal voltage V1-, the connection node between the resistor R35 and the resistor R36 is connected to the 3rd pin of the operational amplifier U6 in the unit operational amplifier circuit 1056, and the terminal voltage V1- is connected to the end of the resistor R37 in the unit operational amplifier circuit 1056 ( Figure 8 The lower end of the device is connected to the ground with the terminal voltage V1- at the same time; Unit voltage divider circuit 1047 (see Fig. 9 ), the structure is that the resistor R41 and the resistor R42 are connected in series between the terminal voltage V2+ and the terminal voltage V2-, the connection node between the resistor R41 and the resistor R42 is connected to the 3rd pin of the operational amplifier U7 in the unit operational amplifier circuit 1057, and the terminal voltage V2- is connected to the end of the resistor R43 in the operational amplifier circuit 1057 ( Fig. 9 The lower end of the device is connected to the ground with the terminal voltage V2- at the same time; Unit voltage divider circuit 1048 (see Fig.10 ), the structure is that resistors R47 and R48 are connected in series between the terminal voltage V2+ and the terminal voltage V2-, the connection node between the resistors R47 and R48 is connected to the 3rd pin of the operational amplifier U8 in the unit operational amplifier circuit 1058, and the terminal voltage V2- is connected to the end of the resistor R49 in the operational amplifier circuit 1058 ( Fig.10 The lower end of the ) is connected, and the terminal voltage V2- is grounded at the same time.

[0017] 5) Operational amplifier circuit 105, including eight unit operational amplifier circuits with the same structure, the operational amplifier circuit 105 is used to perform operational amplifier processing on the voltage signal. Among them, the unit operational amplifier circuit 1051 (see Figure 3), the structure is that the 8th pin of the operational amplifier U1 is connected to the reference source VCC2, the 4th pin of the operational amplifier U1 is connected to the reference source -VCC2, the 3rd pin of the operational amplifier U1 is connected to the node between the resistor R5 and the resistor R6, the 2nd pin of the operational amplifier U1 is grounded through the resistor R7, the 2nd pin of the operational amplifier U1 is connected to the 1st pin of the operational amplifier U1 through the resistor R8, the 1st pin of the operational amplifier U1 is connected to the node between the resistor R9 and the resistor R10 in the unit lifting circuit 1061, and the 1st pin of the operational amplifier U1 is also provided with an output port of the voltage V3; Unit operational amplifier circuit 1052 (see Figure 4 ), the structure is that the 8th pin of the operational amplifier U2 is connected to the reference source VCC2, the 4th pin of the operational amplifier U2 is connected to the reference source -VCC2, the 3rd pin of the operational amplifier U2 is connected to the node between the resistor R11 and the resistor R12, the 2nd pin of the operational amplifier U2 is grounded through the resistor R13, the 2nd pin of the operational amplifier U2 is connected to the 1st pin of the operational amplifier U2 through the resistor R14, the 1st pin of the operational amplifier U2 is connected to the node between the resistor R15 and the resistor R16 in the unit lifting circuit 1062, and the 1st pin of the operational amplifier U2 is also provided with an output port of the voltage V4; Unit operational amplifier circuit 1053 (see Figure 5 ), the structure is that the 8th pin of the operational amplifier U3 is connected to the reference source VCC2, the 4th pin of the operational amplifier U3 is connected to the reference source -VCC2, the 3rd pin of the operational amplifier U3 is connected to the node between the resistor R17 and the resistor R18, the 2nd pin of the operational amplifier U3 is grounded through the resistor R19, the 2nd pin of the operational amplifier U3 is connected to the 1st pin of the operational amplifier U3 through the resistor R20, the 1st pin of the operational amplifier U3 is connected to the node between the resistor R21 and the resistor R22 in the unit lifting circuit 1063, and the 1st pin of the operational amplifier U3 is also provided with an output port of the voltage V5; Unit operational amplifier circuit 1054 (see Figure 6 ), the structure is that the 8th pin of the operational amplifier U4 is connected to the reference source VCC2, the 4th pin of the operational amplifier U4 is connected to the reference source -VCC2, the 3rd pin of the operational amplifier U4 is connected to the node between the resistor R23 and the resistor R24, the 2nd pin of the operational amplifier U4 is grounded through the resistor R25, the 2nd pin of the operational amplifier U4 is connected to the 1st pin of the operational amplifier U4 through the resistor R26, the 1st pin of the operational amplifier U4 is connected to the node between the resistor R27 and the resistor R28 in the unit lifting circuit 1064, and the 1st pin of the operational amplifier U4 is also provided with an output port of the voltage V6; Unit operational amplifier circuit 1055 (see Figure 7), the structure is that the 8th pin of the operational amplifier U5 is connected to the reference source VCC2, the 4th pin of the operational amplifier U5 is connected to the reference source -VCC2, the 3rd pin of the operational amplifier U5 is connected to the node between the resistor R29 and the resistor R30, the 2nd pin of the operational amplifier U5 is grounded through the resistor R31, the 2nd pin of the operational amplifier U5 is connected to the 1st pin of the operational amplifier U5 through the resistor R32, the 1st pin of the operational amplifier U5 is connected to the node between the resistor R33 and the resistor R34 in the unit lifting circuit 1065, and the 1st pin of the operational amplifier U5 is also provided with an output port of the voltage V7; Unit operational amplifier circuit 1056 (see Figure 8 ), the structure is that the 8th pin of the operational amplifier U6 is connected to the reference source VCC2, the 4th pin of the operational amplifier U6 is connected to the reference source -VCC2, the 3rd pin of the operational amplifier U6 is connected to the node between the resistor R35 and the resistor R36, the 2nd pin of the operational amplifier U6 is grounded through the resistor R37, the 2nd pin of the operational amplifier U6 is connected to the 1st pin of the operational amplifier U6 through the resistor R38, the 1st pin of the operational amplifier U6 is connected to the node between the resistor R39 and the resistor R40 in the unit lifting circuit 1066, and the 1st pin of the operational amplifier U6 is also provided with an output port of the voltage V8; Unit operational amplifier circuit 1057 (see Fig. 9 ), the structure is that the 8th pin of the operational amplifier U7 is connected to the reference source VCC2, the 4th pin of the operational amplifier U7 is connected to the reference source -VCC2, the 3rd pin of the operational amplifier U7 is connected to the node between the resistor R41 and the resistor R42, the 2nd pin of the operational amplifier U7 is grounded through the resistor R43, the 2nd pin of the operational amplifier U7 is connected to the 1st pin of the operational amplifier U7 through the resistor R44, the 1st pin of the operational amplifier U7 is connected to the node between the resistor R45 and the resistor R46 in the unit lifting circuit 1067, and the 1st pin of the operational amplifier U7 is also provided with an output port of the voltage V9; Unit op amp circuit 1058 (see Fig.10 ), the structure is that pin 8 of the operational amplifier U8 is connected to the reference source VCC2, pin 4 of the operational amplifier U8 is connected to the reference source -VCC2, pin 3 of the operational amplifier U8 is connected to the node between resistor R47 and resistor R48, pin 2 of the operational amplifier U8 is grounded through resistor R49, pin 2 of the operational amplifier U8 is connected to pin 1 of the operational amplifier U8 through resistor R50, pin 1 of the operational amplifier U8 is connected to the node between resistor R51 and resistor R52 in the unit lifting circuit 1068, and pin 1 of the operational amplifier U8 is also provided with an output port of voltage V10 as the voltage output of the unit operational amplifier circuit 1058.

[0018] 6) The lifting circuit 106 includes eight lifting circuits with the same structure. The lifting circuit 106 is used to convert the negative voltage signal in the AC into a positive voltage signal for collection by the ADC acquisition module. Among them, the unit lifting circuit 1061 (see Figure 3 ), the structure is that the reference source VCC3 is connected to the ground through the resistor R9 and the resistor R10 in sequence, and the node between the resistor R9 and the resistor R10 is connected to the 1st pin of the operational amplifier U1 in the unit operational amplifier circuit 1051 and ADC1 at the same time; Unit lifting circuit 1062 (see Figure 4 ), the structure is that the reference source VCC3 is connected to the ground through the resistor R15 and the resistor R16 in sequence, and the node between the resistor R15 and the resistor R16 is connected to the 1st pin of the operational amplifier U2 in the unit operational amplifier circuit 1052 and ADC2 at the same time; Unit lifting circuit 1063 (see Figure 5 ), the structure is that the reference source VCC3 is connected to the ground through the resistor R21 and the resistor R22 in sequence, and the node between the resistor R21 and the resistor R22 is connected to the 1st pin of the operational amplifier U3 in the unit operational amplifier circuit 1053 and ADC3 at the same time; Unit lifting circuit 1064 (see Figure 6 ), the structure is that the reference source VCC3 is connected to the ground through the resistor R27 and the resistor R28 in sequence, and the node between the resistor R27 and the resistor R28 is connected to the 1st pin of the operational amplifier U4 in the unit operational amplifier circuit 1054 and ADC4 at the same time; Unit lifting circuit 1065 (see Figure 7 ), the structure is that the reference source VCC3 is connected to the ground through the resistor R33 and the resistor R34 in sequence, and the node between the resistor R33 and the resistor R34 is connected to the 1st pin of the operational amplifier U5 in the unit operational amplifier circuit 1055 and ADC5 at the same time; Unit lifting circuit 1066 (see Figure 8 ), the structure is that the reference source VCC3 is connected to the ground through the resistor R39 and the resistor R40 in sequence, and the node between the resistor R39 and the resistor R40 is connected to the 1st pin of the operational amplifier U6 in the unit operational amplifier circuit 1056 and ADC6 at the same time; Unit lifting circuit 1067 (see Fig. 9 ), the structure is that the reference source VCC3 is connected to the ground through the resistor R45 and the resistor R46 in sequence, and the node between the resistor R45 and the resistor R46 is connected to the 1st pin of the operational amplifier U7 and ADC7 in the unit operational amplifier circuit 1057 at the same time; Unit lifting circuit 1068 (see Fig.10), the structure is that the reference source VCC3 is connected to the ground after passing through the resistor R51 and the resistor R52 in sequence, and the node between the resistor R51 and the resistor R52 is simultaneously connected to the 1st pin of the operational amplifier U8 in the unit operational amplifier circuit 1058 and ADC8.

[0019] 7) ADC acquisition module 107, using AD7779ACPZ chip, with 8 channels and 24-bit resolution, is used for collecting the aforementioned 8 groups of ADC voltages.

[0020] 8) MCU108, using STM32F407ZGT6 chip, is used for effective signal judgment and processing, collected signal conversion, relay switch control, resistance calculation, and display control.

[0021] 9) LED display screen 109, used for displaying the final resistance value of the measured resistor Rx.

[0022] The method of the present invention adopts a four-wire method, a segmented acquisition method, and a volt-ampere method during implementation. The four-wire method is used to measure the measured resistor Rx, the segmented acquisition method is used to collect and process the signals of the current and terminal voltage flowing through the measured resistor Rx in different ranges, and the volt-ampere method is used to calculate the final resistance value of the measured resistor Rx, which is finally displayed on the LED display screen 109.

[0023] The milliohm resistance real-time measurement method of the present invention is implemented by using the above-mentioned milliohm resistance real-time measurement circuit according to the following steps: Step 1: Use the four-wire method to connect the measured resistor Rx, MCU108 controls the relay switch circuit 102 to cycle and turn on the power supply in real time, obtain the current I1 and terminal voltage V1 flowing through the measured resistor Rx, and convert the current I1 into the voltage V2. The specific process is: Reference Fig.11 , one end of the measured resistor Rx ( Fig.11 The upper end of the resistor Rx is connected to the 2nd foot of the relay K1 in the relay switch circuit 102. At the same time, the other end of the measured resistor Rx ( Fig.11 The lower end of the current transformer 103 is connected to the 1st foot of the transformer T1 in the current transformer circuit 103, and the MCU 108 controls the relay switch circuit 102 to cycle and open the power supply in real time; When MCU108 outputs a high-level control signal K, pins 1 and 3 of transistor Q1 are turned on, the control relay is turned on, and a path is formed between the power supply circuit 101 and the measured resistor Rx, generating a current I1. , current I1 flows through the measured resistor Rx, generating voltage V1, ; The current I1 flows through the transformer T1 in the current transformer circuit 103, and the transformer T1 has a transformation ratio of n:1, and induces a current I2. , and then flows through resistor R2, generating voltage V2, ; Step 2, simultaneously performing voltage division processing and operational amplifier processing on the voltage V1 and the voltage V2 respectively; The specific process is: The voltage V1 obtained in step 1 is divided and processed by operational amplifier. First, the voltage V1 is divided through six unit voltage divider circuits, and the outputs are as follows: The output voltage of the unit voltage divider circuit 1041 is ; The output voltage of the unit voltage divider circuit 1042 is ; The output voltage of the unit voltage divider circuit 1043 is ; The output voltage of the unit voltage divider circuit 1044 is ; The output voltage of the unit voltage divider circuit 1045 is ; The output voltage of the unit voltage divider circuit 1046 is ; Then, the divided output voltage is used as the input of the corresponding unit operational amplifier circuit, and is processed by the corresponding six unit operational amplifier circuits respectively, and the respective output voltages are as follows: Output voltage of unit operational amplifier circuit 1051 , the voltage divider op amp ratio of voltage V3 to voltage V1 ; The output voltage of the unit operational amplifier circuit 1052 , the voltage divider op amp ratio of voltage V4 to voltage V1 ; Output voltage of unit operational amplifier circuit 1053 , the voltage divider op amp ratio of voltage V5 to voltage V1 ; Output voltage of unit operational amplifier circuit 1054 , the voltage divider op amp ratio of voltage V6 to voltage V1 ; Output voltage of unit operational amplifier circuit 1055 , the voltage divider op amp ratio of voltage V7 to voltage V1 ; Output voltage of unit operational amplifier circuit 1056 , the voltage divider op amp ratio of voltage V8 to voltage V1 , Note: In an operational amplifier, the output voltage cannot exceed the reference source VCC2; At the same time, the voltage V2 obtained in step 1 is divided and processed by operational amplifier. The specific process is: First, the voltage V2 is divided by the remaining two unit voltage divider circuits, and the output is as follows: The output voltage of the unit voltage divider circuit 1047 is ; The output voltage of the unit voltage divider circuit 1048 is ; Then, the divided output voltage is used as the input of the remaining two unit operational amplifier circuits. After being processed by the remaining two unit operational amplifier circuits, the output is as follows: Output voltage of unit operational amplifier circuit 1057 , the voltage divider op amp ratio of voltage V8 to voltage V1 ; Output voltage of unit operational amplifier circuit 1058 , the voltage divider op amp ratio of voltage V10 to voltage V1 .

[0024] Step 3: The signal after the voltage divider operational amplifier is raised for collection by the ADC acquisition module 107. The specific process is: Since the output after the voltage divider operational amplifier is an AC voltage signal with positive and negative polarities, and the ADC acquisition module 107 can only acquire positive polarity voltage signals, the boost circuit 106 is used to convert the negative polarity into positive polarity; In the boost circuit 106, a DC component is applied by dividing the voltage through two resistors of the same resistance value. After the DC voltage and the AC voltage are superimposed, the voltage signals finally input to the ADC acquisition module 107 are ADC1, ADC2, ADC3, ADC4, ADC5, ADC6, ADC7, and ADC8, ranging from 0 to VCC3.

[0025] Step 4: The ADC acquisition module 107 acquires the AC voltage signal and transmits the acquired signal to the MCU 108 for calculation, and finally displays it in real time through the LED display screen 109. The specific process is: 4.1) The ADC acquisition module 107 acquires eight ADC input signals and transmits the acquired values ​​to the MCU 108. The MCU 108 performs interval judgment on the acquired values, selects valid acquired values, and then performs A / D conversion processing on the valid acquired values; Specifically, according to the different ranges of the measured resistor Rx, the voltage V1 at both ends thereof is divided into six sections for processing, each section corresponds to a unit voltage divider circuit, a unit operational amplifier circuit and a unit boost circuit, and finally different output voltages ADC are obtained; According to different ranges of the measured resistance Rx, the voltage V2 corresponding to the current I1 flowing through the measured resistance Rx is divided into two sections for processing, each section corresponds to a unit voltage divider circuit, a unit operational amplifier circuit and a unit boost circuit, and finally different output voltages ADC are obtained; In the ADC acquisition module 107, the ADC acquisition value range is 0 to 16777216, corresponding to the input voltage 0 to VCC3. When the input voltage exceeds VCC3, the acquisition value remains at 16777216. Based on this characteristic, the following two conditions are judged: For the input voltage signals ADC1, ADC2, ADC3, ADC4, ADC5, and ADC6, the judgment condition is: first determine whether the ADC acquisition values ​​corresponding to the six inputs are full-scale, if they are full-scale, remove them, and then select the maximum value in the full-scale range as the effective acquisition value of the voltage V1 this time; For the input voltage signals ADC7 and ADC8, the judgment condition is: first determine whether the ADC acquisition values ​​corresponding to the two inputs are full-scale, if they are full-scale, remove them, and then select the maximum value in the non-full-scale as the effective acquisition value of the voltage V2 this time; 4.2) MCU108 calculates the effective value Ix of the current flowing through the measured resistor Rx and the effective value Ux of the terminal voltage according to the values ​​after A / D conversion. Calculate the value of the measured resistance Rx; 4.3) MCU108 outputs the value of the measured resistance Rx to the LED display screen 109 for real-time display.

[0026] This cycle is repeated to record the test values ​​at regular intervals, thus achieving continuous tracking measurement of the measured resistance Rx.

[0027] Experimental verification 1) According to the aforementioned measurement circuit structure of the present invention, the basic parameters of the measurement circuit are set.

[0028] like Figure 2 As shown, Figure 2 The amplitude of the constant voltage AC source U is 3300mV (because the power signal is an AC continuously changing signal, for the convenience of calculation, the following calculation is based on the maximum value of the power signal in the positive direction of 3300mV. Each point in the actual signal can be calculated in this way), the resistance R1 = 165mΩ, when the relay switch is closed and turned on, the current flowing through the measured resistance Rx (unit mΩ) , unit is A; the voltage across the measured resistor Rx , unit is mV.

[0029] Figure 2 The ratio of the current transformer T1 is 1000:1, R2 = 100Ω, then the voltage , in mV. The reference source VCC1 is 3300mV DC, and the reference source VCC2 is 5000mV DC.

[0030] 2) The voltage V1 across the resistor Rx is divided into six sections for processing, as follows: The first section) 0.001mΩ~0.01mΩ (because the resolution is 0.001mΩ, the minimum value of this measurement section is taken as 0.001mΩ), Corresponding to the unit voltage divider circuit 1041 and the unit operational amplifier circuit 1051, the voltage divider operational amplifier ratio A1=8250, and the output voltage V3 ranges from 164.999 to 1650mV.

[0031] The second section) 0.01mΩ~0.1mΩ, Corresponding to the unit voltage divider circuit 1042 and the unit operational amplifier circuit 1052, the voltage divider operational amplifier ratio A2=825, and the output voltage V4 ranges from 164.990 to 1650 mV.

[0032] The third section) 0.1mΩ~1mΩ, Corresponding to the unit voltage divider circuit 1043 and the unit operational amplifier circuit 1053, the voltage divider operational amplifier ratio A3=83, and the output voltage V5 ranges from 165.899 to 1650mV.

[0033] The fourth section) 1mΩ~10mΩ, Corresponding to the unit voltage divider circuit 1044 and the unit operational amplifier circuit 1054, the voltage divider operational amplifier ratio A4=8.75, and the output voltage V6 ranges from 173.946 to 1650mV.

[0034] The fifth section) 10mΩ~50mΩ, Corresponding to the unit voltage divider circuit 1045 and the unit operational amplifier circuit 1055, the voltage divider operational amplifier ratio A5=2.15, and the output voltage V7 ranges from 405.429 to 1650mV.

[0035] The sixth section) 50mΩ~1000mΩ, Corresponding to the unit voltage divider circuit 1046 and the unit operational amplifier circuit 1056, the voltage divider operational amplifier ratio A6=0.5825, and the output voltage V8 ranges from 447.035 to 1650mV.

[0036] 3) The voltage V2 corresponding to the current I1 flowing through the measured resistor Rx is divided into two sections for processing, as follows: a) 0.001mΩ~275mΩ (because the resolution is 0.001mΩ, the minimum value is taken as 0.001mΩ), Corresponding to the unit voltage divider circuit 1047 and the unit operational amplifier circuit 1057, the voltage divider operational amplifier ratio A7=0.825, and the output voltage V9 ranges from 618.750 to 1650 mV.

[0037] b) 275mΩ~1000mΩ, Corresponding to the unit voltage divider circuit 1048 and the unit operational amplifier circuit 1058, the voltage divider operational amplifier ratio A8=2.2, and the output voltage V10 ranges from 623.176 to 1650mV.

[0038] 4) In the boost circuit, VCC3 is 3300mV DC, the applied DC component is 1650mV, and eight-unit boost circuits are used. After the DC voltage and AC voltage are superimposed, the output voltage ADC range is 0 to 3300mV.

[0039] Example 1 Based on the basic setting of the aforementioned measurement circuit, the implementation process of this embodiment 1 is: When the product marked value of the measured resistance Rx is 0.005mΩ, the current I1=19.999A, the terminal voltage V1=0.100mV, and the voltage V2=1999.939mV; After being processed by the voltage divider circuit 104 and the corresponding operational amplifier circuit 105, the output voltages are: V3=824.975mV, V4=82.498mV, V5=8.300mV, V6=0.875mV, V7=0.215mV, V8=0.058mV, V9=1649.950mV, V10=4399.867mV; After being processed by the lifting circuit 106, the ADC acquisition module 107 is used as an input to the ADC acquisition module 107, and the corresponding ADC acquisition values ​​are: the acquisition value of ADC1 is 12582784, the acquisition value of ADC2 is 8808025, the acquisition value of ADC3 is 8430803, the acquisition value of ADC4 is 8393056, the acquisition value of ADC5 is 8389701, the acquisition value of ADC6 is 8388904, the acquisition value of ADC7 is 16776961, and the acquisition value of ADC8 is 16777216; According to the judgment rule in the above step 5, the valid acquisition value in ADC1 to ADC6 is ADC1, corresponding to 0.001mΩ to 0.01mΩ, and the valid acquisition value in ADC7 to ADC8 is ADC7, corresponding to 0.001mΩ to 275mΩ.

[0040] MCU108 performs A / D conversion on the effective collected values, and then calculates that the effective value of the terminal voltage V1 is 0.100mV and the effective value of the current I1 is 19.999A. The value of the measured resistance Rx is calculated to be 0.005 mΩ, and finally the value is output to the LED display screen 109 for real-time display.

[0041] Example 2 Based on the basic setting of the aforementioned measurement circuit, the implementation process of this embodiment 2 is: When the product marked value of the measured resistance Rx is 0.05mΩ, the current I1=19.994A, the terminal voltage V1=1.000mV, and the voltage V2=1999.394mV; After being processed by the voltage divider circuit 104 and the corresponding operational amplifier circuit 105, the output voltages are V3=5000mV, V4=824.750mV, V5=82.975mV, V6=8.747mV, V7=2.149mV, V8=0.582mV, V9=1649.500mV, and V10=4398.667mV; After being processed by the lifting circuit 106, the ADC acquisition module 107 is used as an input, and the ADC acquisition module 107 acquires the input signal, and the corresponding ADC acquisition values ​​are: the acquisition value of ADC1 is 16777216, the acquisition value of ADC2 is 12581641, the acquisition value of ADC3 is 8810452, the acquisition value of ADC4 is 8433079, the acquisition value of ADC5 is 8399535, the acquisition value of ADC6 is 8391568, the acquisition value of ADC7 is 16774674, and the acquisition value of ADC8 is 16777216; According to the judgment rule in the above step 5, the valid acquisition value in ADC1 to ADC6 is ADC2, corresponding to 0.01mΩ to 0.1mΩ, and the valid acquisition value in ADC7 to ADC8 is ADC7, corresponding to 0.001mΩ to 275mΩ.

[0042] MCU108 performs A / D conversion on the effective collected values, and then calculates that the effective value of the terminal voltage V1 is 1.000mV and the effective value of the current I1 is 19.994A. The value of the measured resistance Rx is calculated to be 0.050 mΩ, and finally the value is output to the LED display screen 109 for real-time display.

[0043] Example 3 Based on the basic setting of the aforementioned measurement circuit, the implementation process of this embodiment 3 is: When the product marked value of the measured resistance Rx is 0.5mΩ, the current I1=19.940A, the terminal voltage V1=9.970mV, and the voltage V2=1993.958mV; After being processed by the voltage divider circuit 104 and the corresponding operational amplifier circuit 105, the output voltages are V3=5000mV, V4=5000mV, V5=827.492mV, V6=87.236mV, V7=21.435mV, V8=5.807mV, V9=1645.015mV, and V10=4386.707mV; After being processed by the lifting circuit 106, the ADC acquisition module 107 is used as an input, and the ADC acquisition module 107 acquires the input signal, and the corresponding ADC acquisition values ​​are: the acquisition value of ADC1 is 16777216, the acquisition value of ADC2 is 16777216, the acquisition value of ADC3 is 12595583, the acquisition value of ADC4 is 8832114, the acquisition value of ADC5 is 8497583, the acquisition value of ADC6 is 8418132, the acquisition value of ADC7 is 16751872, and the acquisition value of ADC8 is 16777216; According to the judgment rule in the above step 5, the valid acquisition value in ADC1 to ADC6 is ADC3, corresponding to 0.1mΩ to 1mΩ, and the valid acquisition value in ADC7 to ADC8 is ADC7, corresponding to 0.001mΩ to 275mΩ.

[0044] MCU108 performs A / D conversion on the effective collected values, and then calculates that the effective value of the terminal voltage V1 is 9.970mV and the effective value of the current I1 is 19.940A. The value of the measured resistance Rx is calculated to be 0.500 mΩ, and finally the value is output to the LED display screen 109 for real-time display.

[0045] Example 4 Based on the basic setting of the aforementioned measurement circuit, the implementation process of this embodiment 4 is: When the product marked value of the measured resistor Rx is 5mΩ, the current I1=19.412A, the terminal voltage V1=97.059mV, and the voltage V2=1941.176mV; After being processed by the voltage divider circuit 104 and the corresponding operational amplifier circuit 105, the output voltages are V3=5000mV, V4=5000mV, V5=5000mV, V6=849.265mV, V7=208.676mV, V8=56.537mV, V9=1601.471mV, and V10=4270.588mV; After being processed by the lifting circuit 106, the ADC acquisition module 107 is used as an input, and the ADC acquisition module 107 acquires the input signal, and the corresponding ADC acquisition values ​​are: the acquisition value of ADC1 is 16777216, the acquisition value of ADC2 is 16777216, the acquisition value of ADC3 is 16777216, the acquisition value of ADC4 is 12706273, the acquisition value of ADC5 is 9449520, the acquisition value of ADC6 is 8676041, the acquisition value of ADC7 is 16530492, and the acquisition value of ADC8 is 16777216; According to the judgment rule in step 5 above, the valid acquisition value in ADC1 to ADC6 is ADC4, corresponding to 1mΩ to 10mΩ, and the valid acquisition value in ADC7 to ADC8 is ADC7, corresponding to 0.001mΩ to 275mΩ.

[0046] MCU108 performs A / D conversion on the effective collected values, and then calculates that the effective value of the terminal voltage V1 is 97.059mV and the effective value of the current I1 is 19.412A. The value of the measured resistance Rx is calculated to be 5.000 mΩ, and finally the value is output to the LED display screen 109 for real-time display.

[0047] Example 5 Based on the basic setting of the aforementioned measurement circuit, the implementation process of this embodiment 5 is: When the product marked value of the measured resistance Rx is 25mΩ, the current I1=17.368A, the terminal voltage V1=434.211mV, and the voltage V2=1736.842mV; After being processed by the voltage divider circuit 104 and the corresponding operational amplifier circuit 105, the output voltages are V3=5000mV, V4=5000mV, V5=5000mV, V6=3799.342mV, V7=933.553mV, V8=252.928mV, V9=1432.895mV, and V10=3821.053mV; After being processed by the lifting circuit 106, the ADC acquisition module 107 is used as the input, and the ADC acquisition module 107 acquires the input signal, and the corresponding ADC acquisition values ​​are: the acquisition value of ADC1 is 16777216, the acquisition value of ADC2 is 16777216, the acquisition value of ADC3 is 16777216, the acquisition value of ADC4 is 16777216, the acquisition value of ADC5 is 13134794, the acquisition value of ADC6 is 9674493, the acquisition value of ADC7 is 15673451, and the acquisition value of ADC8 is 16777216; According to the judgment rule in the above step 5, the valid acquisition value in ADC1 to ADC6 is ADC5, corresponding to 10mΩ to 50mΩ, and the valid acquisition value in ADC7 to ADC8 is ADC7, corresponding to 0.001mΩ to 275mΩ.

[0048] MCU108 performs A / D conversion on the effective collected values, and then calculates that the effective value of the terminal voltage V1 is 434.211mV and the effective value of the current I1 is 17.368A. The value of the measured resistance Rx is calculated to be 25.001 mΩ, and finally the value is output to the LED display screen 109 for real-time display.

[0049] Example 6 Based on the basic setting of the aforementioned measurement circuit, the implementation process of this embodiment 6 is: When the product marked value of the measured resistor Rx is 500mΩ, the current I1=4.962A, the terminal voltage V1=2481.203mV, and the voltage V2=496.241mV; After being processed by the voltage divider circuit 104 and the corresponding operational amplifier circuit 105, the output voltages are: V3=5000mV, V4=5000mV, V5=5000mV, V6=5000mV, V7=5000mV, V8=1445.301mV, V9=409.398mV, V10=1091.729mV; After being processed by the lifting circuit 106, the ADC acquisition module 107 is used as the input, and the ADC acquisition module 107 acquires the input signal, and the corresponding ADC acquisition values ​​are: the acquisition value of ADC1 is 16777216, the acquisition value of ADC2 is 16777216, the acquisition value of ADC3 is 16777216, the acquisition value of ADC4 is 16777216, the acquisition value of ADC5 is 16777216, the acquisition value of ADC6 is 15736524, the acquisition value of ADC7 is 10469991, and the acquisition value of ADC8 is 13938965; According to the judgment rule in step 5 above, the valid acquisition value in ADC1 to ADC6 is ADC6, corresponding to 50mΩ to 1000mΩ, and the valid acquisition value in ADC7 to ADC8 is ADC8, corresponding to 275mΩ to 1000mΩ.

[0050] MCU108 performs A / D conversion on the effective collected values, and then calculates that the effective value of the terminal voltage V1 is 2481.203mV and the effective value of the current I1 is 4.962A. The value of the measured resistance Rx is calculated to be 500.041 mΩ, and finally the value is input to the LED display screen 109 for real-time display.

[0051] In summary, the milliohm resistance real-time measurement circuit and measurement method of the present invention have high acquisition accuracy and high stability, and are applicable to long-term continuous real-time measurement of various types of contact small resistances (0-1000mΩ), and the resistance value display is convenient.

Claims

1. Milliohm resistance real-time measurement circuit, characterized by: The invention comprises a power supply circuit (101), a voltage divider circuit (104), an operational amplifier circuit (105), a lifting circuit (106), an ADC acquisition module (107), an MCU (108), and an LED display screen (109), which are sequentially connected in series; the MCU (108) is connected to the power supply circuit (101) through a relay switch circuit (102); and the power supply circuit (101) is connected to the voltage divider circuit (104) through a current mutual induction circuit (103).

2. The milliohm resistance real-time measurement circuit according to claim 1, characterized in that: The relay switch circuit (102) has a structure in which pin 4 of the relay K1 is connected to a reference source VCC1, pin 1 of the relay K1 is connected to a resistor R1 in the power supply circuit (101), pin 2 of the relay K1 is connected to one end of a resistor Rx to be measured, and pin 3 of the relay K1 is connected to pin 1 of a transistor Q1; pin 2 of the transistor Q1 is connected to a control signal K via a resistor R4, pin 2 of the transistor Q1 is further connected to pin 3 of the transistor Q1 via a resistor R3, and pin 3 of the transistor Q1 is grounded.

3. The milliohm resistance real-time measurement circuit according to claim 1, characterized in that: The current mutual inductance circuit (103) has a structure in which pin 1 of the mutual inductance transformer T1 is connected to the other end of the measured resistor Rx, pin 2 of the mutual inductance transformer T1 is connected to the "-" of the constant AC voltage source U in the power supply circuit (101), pin 3 of the mutual inductance transformer T1 is simultaneously connected to the cathode of the diode D1, the anode of the diode D2, one end of the resistor R2, and the output terminal V2+, and pin 4 of the mutual inductance transformer T1 is simultaneously connected to the anode of the diode D1, the cathode of the diode D2, the other end of the resistor R2, and the output terminal V2-.

4. The milliohm resistance real-time measurement circuit according to claim 1, characterized in that: The voltage divider circuit (104) comprises eight unit voltage divider circuits with the same structure; wherein the structure of the unit voltage divider circuit (1041) is that a resistor R5 and a resistor R6 are connected in series between the terminal voltage V1+ and the terminal voltage V1-, the connection node between the resistor R5 and the resistor R6 is connected to the 3rd pin of the operational amplifier U1 in the unit operational amplifier circuit (1051), the terminal voltage V1- is connected to the end of the resistor R7 in the unit operational amplifier circuit (1051), and the terminal voltage V1- is also grounded.

5. The milliohm resistance real-time measurement circuit according to claim 1, characterized in that: The operational amplifier circuit (105) comprises eight unit operational amplifier circuits with the same structure; wherein the structure of the unit operational amplifier circuit (1051) is that pin 8 of the operational amplifier U1 is connected to the reference source VCC2, pin 4 of the operational amplifier U1 is connected to the reference source -VCC2, pin 3 of the operational amplifier U1 is connected to the node between the resistor R5 and the resistor R6, pin 2 of the operational amplifier U1 is grounded via the resistor R7, pin 2 of the operational amplifier U1 is connected to pin 1 of the operational amplifier U1 via the resistor R8, pin 1 of the operational amplifier U1 is connected to the node between the resistor R9 and the resistor R10 in the unit lifting circuit (1061), and pin 1 of the operational amplifier U1 is also provided with an output port of a voltage V3.

6. The milliohm resistance real-time measurement circuit according to claim 1, characterized in that: The lifting circuit (106) comprises eight unit lifting circuits with the same structure; wherein the structure of the unit lifting circuit (1061) is that the reference source VCC3 is connected to the ground through the resistor R9 and the resistor R10 in sequence, and the node between the resistor R9 and the resistor R10 is simultaneously connected to the pin 1 of the operational amplifier U1 in the unit operational amplifier circuit (1051) and ADC1.

7. A method for real-time measurement of milliohm resistance, using the real-time measurement circuit for milliohm resistance according to any one of claims 1 to 6, characterized in that: Follow these steps to implement: Step 1: A four-wire method is used to connect the resistor Rx to be measured, and the MCU (108) controls the relay switch circuit (102) to cycle on and off the power supply in real time, obtains the current I1 and the terminal voltage V1 flowing through the resistor Rx to be measured, and converts the current I1 into the voltage V2; Step 2, simultaneously performing voltage division processing and operational amplifier processing on the voltage V1 and the voltage V2 respectively; Step 3, performing a boost process on the signal after the voltage divider operational amplifier, so as to provide it for collection by the ADC collection module (107); Step 4: The ADC acquisition module (107) acquires the AC voltage signal and transmits the acquired signal to the MCU (108), and finally displays it in real time through the LED display screen (109).

8. The method for real-time measurement of milliohm resistance according to claim 7, characterized in that: In step 2, the specific process is: The voltage V1 obtained in step 1 is subjected to voltage division and operational amplifier processing. The specific process is: First, the voltage V1 is divided by six unit voltage divider circuits, and the output is as follows: The output voltage of the unit voltage divider circuit (1041) is ; The output voltage of the unit voltage divider circuit (1042) is ; The output voltage of the unit voltage divider circuit (1043) is ; The output voltage of the unit voltage divider circuit (1044) is ; The output voltage of the unit voltage divider circuit (1045) is ; The output voltage of the unit voltage divider circuit (1046) is ; Then, the divided output voltage is used as the input of the corresponding unit operational amplifier circuit. After being processed by the corresponding six unit operational amplifier circuits, the respective output voltages are as follows: Output voltage of unit operational amplifier circuit (1051) , the voltage divider op amp ratio of voltage V3 to voltage V1 ; Output voltage of unit operational amplifier circuit (1052) , the voltage divider op amp ratio of voltage V4 to voltage V1 ; Output voltage of unit operational amplifier circuit (1053) , the voltage divider op amp ratio of voltage V5 to voltage V1 ; Output voltage of unit operational amplifier circuit (1054) , the voltage divider op amp ratio of voltage V6 to voltage V1 ; Output voltage of unit operational amplifier circuit (1055) , the voltage divider op amp ratio of voltage V7 to voltage V1 ; Output voltage of unit operational amplifier circuit (1056) , the voltage divider op amp ratio of voltage V8 to voltage V1 ; At the same time, the voltage V2 obtained in step 1 is subjected to voltage division and operational amplifier processing. The specific process is: First, the voltage V2 is divided by the remaining two unit voltage divider circuits, and the output is: The output voltage of the unit voltage divider circuit (1047) is ; The output voltage of the unit voltage divider circuit (1048) is ; Then, the divided output voltage is used as the input of the remaining two unit operational amplifier circuits. After being processed by the remaining two unit operational amplifier circuits, the output is: Output voltage of unit operational amplifier circuit (1057) , the voltage divider op amp ratio of voltage V8 to voltage V1 ; Output voltage of unit operational amplifier circuit (1058) , the voltage divider op amp ratio of voltage V10 to voltage V1 .

9. The method for real-time measurement of milliohm resistance according to claim 7, characterized in that: In step 3, the specific process is: The output of the voltage divider op amp is an AC voltage signal with positive and negative polarities. The negative polarity is converted into positive polarity using a boost circuit (106). In the boost circuit (106), the voltage is divided by two resistors of the same resistance value, and a DC component is applied. After the DC voltage and the AC voltage are superimposed, the voltage signals finally input to the ADC acquisition module (107) are ADC1, ADC2, ADC3, ADC4, ADC5, ADC6, ADC7, ADC8, ranging from 0 to VCC3.

10. The method for real-time measurement of milliohm resistance according to claim 7, characterized in that: In step 4, the specific process is: 4.1) The ADC acquisition module (107) acquires eight ADC input signals and transmits the acquired values ​​to the MCU (108). The MCU 108 (108) performs interval judgment on the acquired values, selects valid acquired values, and then performs A / D conversion processing on the valid acquired values; In the ADC acquisition module (107), the ADC acquisition value range is 0 to 16777216, corresponding to the input voltage 0 to VCC3. When the input voltage exceeds VCC3, the acquisition value remains at 16777216. Based on this characteristic, the following two conditions are judged: For the input voltage signals ADC1, ADC2, ADC3, ADC4, ADC5, and ADC6, the judgment condition is: first determine whether the ADC acquisition values ​​corresponding to the six inputs are full-scale, if they are full-scale, remove them, and then select the maximum value in the full-scale range as the effective acquisition value of the voltage V1 this time; For the input voltage signals ADC7 and ADC8, the judgment condition is: first determine whether the ADC acquisition values ​​corresponding to the two inputs are full-scale, if they are full-scale, remove them, and then select the maximum value in the non-full-scale as the effective acquisition value of the voltage V2 this time; 4.2) MCU (108) calculates the effective value Ix of the current flowing through the measured resistor Rx and the effective value Ux of the terminal voltage according to the A / D converted data. Calculate the value of the measured resistance Rx; 4.3) MCU (108) outputs the value of the measured resistance Rx to the LED display screen (109) for real-time display.

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