Sampling resistance type current sensor

Abstract

The invention discloses a sampling resistor type current sensor, and relates to the field of current sensing. A multi-range sampling module of the current sensor comprises a plurality of sampling resistor groups corresponding to different current ranges, a plurality of balancing resistor groups and a change-over switch. When the current is measured, the sampling resistor group matched with the current range of the measured current loop is connected in series with the measured current loop; the multi-range sampling module is used for converting current signals of different ranges into voltage signals; the dual-power-supply voltage stabilizing module provides a positive power supply and a negative power supply for the differential amplification module. The differential amplification module amplifies the voltage signal according to a preset amplification factor and outputs the amplified voltage signal; and the amplified voltage signal value is equal to the current value of the detected current loop. According to the invention, the detection precision and stability of the wide-range current can be improved.

Description

Technical Field

[0001] This application relates to the field of current sensing, and in particular to a sampling resistive current sensor. Background Technology

[0002] Current measurement is a core technology in fields such as industrial process inspection, electrical equipment operation and maintenance, industrial control load monitoring, and precision electrical calibration. Its measurement accuracy and wide range adaptability directly determine the applicable scenarios and testing reliability of downstream systems. For example, in low-voltage industrial control circuit monitoring, it is necessary to accurately capture mA-level micro-currents. In the operation test of small power equipment, it is necessary to adapt to 10A~15A rated operating current. In multi-condition electrical testing scenarios, it is even more necessary to take into account the stable testing requirements of multiple ranges and multiple measurement ranges.

[0003] During current measurement, existing circuits suffer from insufficient power supply stability and limited anti-interference capability of amplifier circuits, resulting in low amplification accuracy of current signals flowing through the sampling resistor and measurement results that are easily affected by noise and power supply fluctuations. Furthermore, the use of a single fixed sampling resistor cannot flexibly adapt to the needs of current measurement of different magnitudes. Small current signals are weak after sampling and difficult to identify effectively, while large currents are prone to exceeding the rated power of the sampling resistor and causing damage. Ultimately, it is difficult to achieve multi-range, stable, and accurate detection of weak currents. Summary of the Invention

[0004] The purpose of this application is to provide a sampling resistive current sensor that can improve the detection accuracy and stability of a wide range of currents.

[0005] To achieve the above objectives, this application provides the following solution: This application provides a sampling resistive current sensor, including: a multi-range sampling module, a differential amplifier module, and a dual-power supply voltage regulator module; The multi-range sampling module is used to convert current signals of different ranges into voltage signals; The multi-range sampling module includes multiple sampling resistor groups corresponding to different current ranges, multiple balancing resistor groups, and a switching switch. When measuring current, the sampling resistor group matching the current range of the current loop being measured is connected in series with the current loop being measured. The two ends of one sampling resistor group are respectively connected to the two input terminals of one balancing resistor group. The non-inverting output terminal of one balancing resistor group is connected to the non-inverting input terminal of the differential amplifier module, and the inverting output terminal of one balancing resistor group is connected to one switch position of the switching switch. The common terminal of the switching switch is connected to the inverting input terminal of the differential amplifier module. The positive power supply terminal of the differential amplifier module is connected to the positive output terminal of the dual power supply voltage regulator module, and the negative power supply terminal of the differential amplifier module is connected to the negative output terminal of the dual power supply voltage regulator module. The dual power supply voltage regulator module is used to provide positive and negative power supplies to the differential amplifier module. The differential amplifier module is used to amplify the voltage signal according to a preset amplification factor and output the amplified voltage signal. The value of the amplified voltage signal is equal to the current value of the current loop being measured.

[0006] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a sampling resistor current sensor. By switching between sampling resistor groups with different current ranges, the multi-range sampling module can adapt to different current measurement ranges, balancing effective sampling of small currents with safe carrying of large currents, and realizing wide-range current measurement. The balanced resistor group can cancel common-mode noise and linearly amplify only the differential-mode voltage across the sampling resistor group, greatly improving the signal's anti-interference capability and detection accuracy. It provides dual power supplies for the differential amplifier module, avoiding zero-point drift caused by a single power supply and ensuring power supply stability. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 A Proteus simulation diagram of a sampling resistive current sensor provided for an embodiment of this application; Figure 2 A physical circuit diagram of a four-range current sensor provided in this application embodiment; Figure 3 The PCB diagram of the four-range current sensor provided in the embodiments of this application; Figure 4 This is a three-dimensional top-level view of the PCB of a four-range current sensor provided in an embodiment of this application; Figure 5 This is a three-dimensional bottom layer diagram of the PCB of a four-range current sensor provided in an embodiment of this application; Figure 6 Proteus simulation test diagram of the sampling resistive current sensor provided in the embodiments of this application; Figure 7 This is a schematic diagram of the solenoid valve current test results provided in an embodiment of this application. Detailed Implementation

[0009] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0010] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0011] Existing technologies for current measurement fall into two categories: mainstream Hall effect current sensors and traditional single-range sampling resistive current sensors. The structural composition, connection relationships, and core shortcomings of these two types of solutions are as follows: Hall effect current sensor (the mainstream current detection solution in the industry): This is a non-contact current detection device. Its core structure includes a Hall effect sensing module, a magnetic core coupling module, a signal amplification module, and a voltage regulator module. The connection relationship and working principle of each module are as follows: Magnetic core coupling module: It adopts a closed ring magnetic core. The conductor of the current to be measured passes through the inside of the magnetic core, and the weak magnetic field generated by the current to be measured is focused to the Hall sensing module to realize the conversion of current signal to magnetic field signal; Hall effect sensing module: The core is a Hall element, which is fixedly installed in the air gap of the magnetic core. It senses the intensity of the converged magnetic field and converts the magnetic field signal into a weak voltage signal based on the Hall effect. The amplitude of the voltage signal is proportional to the measured current. Signal amplification module: A fixed-gain amplifier circuit is built using a general-purpose operational amplifier. The input is connected to the output of a Hall element to amplify weak voltage signals and adapt them to back-end acquisition equipment. Voltage Regulator Module: It adopts a 5V single-supply voltage regulator chip to provide operating power for Hall elements and operational amplifiers, and has a negative voltage compensation design.

[0012] Traditional single-range sampling resistive current sensor: This is a contact-type current detection device. Its core components include a single-range sampling module, a fixed-gain operational amplifier module, a single-power supply module, and an output conditioning module. The connection relationships and functions of each module are as follows: Single-range sampling module: It uses a single fixed-value low-resistance precision resistor (typically 0.1Ω~1Ω), which is connected in series to the current loop being measured. Based on Ohm's law, it directly converts the current signal into a weak voltage signal. It can only adapt to a single narrow range of current (such as a 0.1Ω resistor adapting to 1A~1.5A) and cannot be compatible with a wide range of currents. Fixed gain operational amplifier module: A differential amplifier circuit is constructed using a general-purpose high-precision operational amplifier (such as OP07). The non-inverting and inverting inputs of the amplifier are connected to the two ends of the sampling resistor, respectively. A single amplification factor (10x to 100x) is configured through a fixed resistance feedback resistor. The amplification factor is tied to a single sampling resistor and cannot be adapted to different range signal amplitudes. Single power supply module: The input voltage is converted to a 9V single power supply using a 7809 linear regulator chip and connected to the positive power supply terminal of the operational amplifier. The negative power supply terminal is directly grounded, which limits the linear operating range of the operational amplifier. Output conditioning module: It adopts a fixed parameter resistor voltage divider circuit to condition the amplitude of the amplified voltage signal. It has no range switching function and can only match a single amplification factor output signal.

[0013] The current mainstream current detection technology uses Hall current sensors as the core, supplemented by traditional single-range sampling resistive current sensors. The core structure and working mechanism of these two types of solutions determine that they cannot meet the high-precision and stable detection requirements of multi-range currents from 0.1A to 15A. The disadvantages of each solution are as follows: (1) Inherent defects in the core of Hall current sensor The accuracy of weak current detection is extremely low: Hall element has limited sensitivity, and the sensing signal of weak current in the mA level is weak. Zero point drift and temperature drift are significant, and the measurement error is ≥5%, which cannot meet the requirements of high-precision detection. Poor anti-interference ability: It is easily affected by external electromagnetic magnetic fields. Stray magnetic fields in the environment will be directly superimposed on the induction signal, resulting in distorted detection results. It lacks effective anti-interference suppression methods. Cost and size disadvantages: It requires the integration of dedicated Hall elements and closed magnetic cores, which costs 3 to 5 times more than the sampling resistor solution. In addition, the magnetic core results in a larger size, making it unsuitable for miniaturized sensing systems. Poor small signal resolution: Weak signals have a low signal-to-noise ratio and are easily drowned out by noise. Small signals are difficult to distinguish, there are signal capture blind spots, and real-time accurate detection cannot be achieved.

[0014] (2) The core of traditional single-range sampling resistive current sensor is insufficient. Power supply structure defects: Single power supply limits the dynamic operating range of the operational amplifier, weak signal amplification is prone to truncated distortion, there is no high-precision dual power supply support, and power supply fluctuations introduce additional measurement errors; Insufficient anti-interference capability: The power supply is equipped with only small-capacity ceramic capacitors, which cannot suppress low-frequency ripple; the signal end has no dedicated filtering network, and noise is easily coupled to the amplification circuit, drowning out the weak sampling signal; Single measurement range and poor adaptability: A single fixed sampling resistor only covers a narrow current range. The voltage signal amplitude is insufficient when the current is small, and the sampling resistor is easily burned out when the current is large. It cannot be adapted to the detection of weak currents of multiple levels. Poor amplification matching: The fixed amplification factor is tied to a single sampling resistor, which cannot be flexibly adjusted according to the amplitude of the sampling signal, further restricting the detection accuracy and measurement range coverage.

[0015] The aforementioned shortcomings are derived according to the "primary and secondary hierarchy" and strict causal relationship as follows: 1. The most significant drawback: Insufficient accuracy in multi-range current detection (0.1A~15A). Current mainstream Hall current sensors employ a non-contact detection mechanism of "magnetic core coupling + Hall element sensing": the measured current passes through the magnetic core to generate a magnetic field, the Hall element senses the magnetic field strength and converts it into a voltage signal, which is then output through a single-supply amplification circuit. This structure has an inherent core defect: the sensing sensitivity and range adaptability of the Hall element are inherently contradictory. For a weak current of 0.1A, the generated magnetic field strength is weak, resulting in an extremely low signal-to-noise ratio of the Hall element's sensing signal. Coupled with the effects of magnetic core zero-point drift and temperature drift, the signal distortion is severe. For a larger current of 15A, the magnetic core is prone to saturation, leading to a deterioration in the linearity of the sensing signal. In addition, the dynamic range of the single-supply amplification circuit is limited, ultimately causing the Hall sensor's measurement error to generally exceed 5% across the entire range of 0.1A to 15A, failing to meet the requirements for high-precision detection.

[0016] Traditional single-range sampling resistive sensors, while having a direct response and no magnetic saturation issues, employ a "single fixed-value sampling resistor + fixed-gain amplification" design. A large-value sampling resistor, adapted to a weak current of 0.1A, will instantly exceed its rated power and burn out under a high current of 15A, necessitating the use of a small-value sampling resistor. However, the voltage signal converted from a 0.1A current by a small-value sampling resistor is weak, and the fixed-gain amplification either fails to effectively capture the signal or amplifies noise simultaneously, leading to loss of accuracy across the entire range. This also fails to overcome the accuracy bottleneck of multi-range sensors from 0.1A to 15A.

[0017] 2. Minor weaknesses (derived from core weaknesses, with a clear causal relationship) Poor range adaptability: The range of Hall sensors is fixed by the magnetic core specifications and Hall element parameters, which cannot flexibly cover a wide range of 0.1A to 15A. It either meets the requirements of small current but loses the range of large current, or it adapts to large current but cannot accurately detect small current. Traditional sampling resistor sensors have a single fixed resistance value design, which makes it difficult to take into account both the effective sampling of weak current of 0.1A and the safe carrying of large current of 15A. The range coverage is narrow and multi-range adaptability is completely lacking.

[0018] Weak anti-interference capability: Hall sensors are essentially magnetic field sensors, which are highly susceptible to interference from external electromagnetic stray magnetic fields. The interfering magnetic field will be directly superimposed on the measured magnetic field, causing the detection signal of a weak 0.1A current to be submerged and the detection signal of a 15A current to be deflected. Traditional sampling resistor sensors lack a targeted filtering network, and power supply ripple and environmental noise are easily coupled to the amplification circuit, further deteriorating the detection accuracy of the weak 0.1A signal and affecting the measurement stability of the 15A current.

[0019] The imbalance between cost and reliability: Hall sensors require dedicated Hall elements, customized magnetic cores and linear conditioning chips. Products that can adapt to a wide range of 0.1A to 15A are more expensive, costing 3 to 5 times more than sampling resistor solutions. Moreover, magnetic core saturation issues lead to poor long-term reliability. Although traditional sampling resistor sensors are cheaper, additional protection circuits are required to prevent burnout at 15A current. A calibration module is also required to improve 0.1A accuracy, indirectly increasing system costs. Furthermore, the operation of protection circuits is prone to introducing additional errors.

[0020] Response lag and poor linearity: Hall sensors rely on magnetic fields to transmit signals, which has an inherent response delay and cannot capture current fluctuations in the range of 0.1A to 15A in real time. For a large current of 15A, magnetic core saturation will cause nonlinear distortion of the signal. Traditional sampling resistor sensors are prone to signal truncation and nonlinear amplification problems at both ends of the range due to the mismatch between fixed gain and single sampling resistor.

[0021] The core causal logic can be summarized as follows: Existing technology has core structural defects (magnetic coupling of Hall sensors + contradiction between sensitivity and range, single fixed resistance value and fixed gain of traditional sampling resistors, and single power supply limitations of the two types of solutions) → the most significant drawback (insufficient accuracy in detecting multiple range currents from 0.1A to 15A) → secondary drawbacks (poor range adaptability, weak anti-interference ability, imbalance between cost and reliability, and poor response hysteresis linearity) → ultimately, it cannot meet the high-precision and stable detection requirements of wide range currents from 0.1A to 15A in fields such as industrial sensing, equipment power consumption monitoring, and electrical circuit detection.

[0022] To address the aforementioned deficiencies, in an exemplary embodiment, such as Figure 1As shown, a sampling resistor-type current sensor is provided, comprising: a multi-range sampling module, a differential amplifier module, and a dual-power supply voltage regulator module. The multi-range sampling module is used to convert current signals of different ranges into voltage signals. The multi-range sampling module includes multiple sampling resistor groups corresponding to different current ranges, multiple balancing resistor groups, and a switching switch. When measuring current, a sampling resistor group matching the current range of the measured current loop is connected in series with the measured current loop. The two ends of one sampling resistor group are respectively connected to the two input terminals of a balancing resistor group. The non-inverting output terminal of one balancing resistor group is connected to the non-inverting input terminal of the differential amplifier module, and the inverting output terminal of one balancing resistor group is connected to one switch position of the switching switch. The common terminal of the switching switch is connected to the inverting input terminal of the differential amplifier module. The positive power supply terminal of the differential amplifier module is connected to the positive output terminal of the dual power supply voltage regulator module, and the negative power supply terminal of the differential amplifier module is connected to the negative output terminal of the dual power supply voltage regulator module. The dual power supply voltage regulator module is used to provide positive and negative power supplies to the differential amplifier module. The differential amplifier module is used to amplify the voltage signal according to a preset amplification factor and output the amplified voltage signal. The value of the amplified voltage signal is equal to the current value of the current loop being measured.

[0023] The sampling resistor current sensor of this application is a multi-range current measurement sensor based on operational amplification and regulated power supply. By configuring multiple sampling resistor groups to adapt to different current measurement ranges, and with an appropriate amplification factor matching mechanism, combined with a high-stability operational amplification circuit, a regulated power supply and a filter network, it effectively suppresses the influence of noise interference and power supply fluctuations on the measurement results. It can avoid the problems of insufficient sampling signal for small currents and overload of sampling resistors for large currents, and can achieve high-precision detection of small current signals in sampling resistors of different ranges. It provides a reliable and highly adaptable current measurement solution for high-precision sensing and detection systems.

[0024] As an optional implementation, the balancing resistor group includes two resistors, a first resistor and a second resistor, with the same resistance value. One end of the first resistor is connected to one end of the sampling resistor group; the other end of the first resistor serves as the non-inverting output terminal of the balancing resistor group and is connected to the non-inverting input terminal of the differential amplifier module. One end of the second resistor is connected to the other end of the sampling resistor group; the other end of the second resistor serves as the inverting output terminal of the balancing resistor group and is connected to one of the switching positions of the switch.

[0025] In one implementation, if the number of sampling resistor groups and balancing resistor groups are both four, then the four sampling resistor groups are named the first sampling resistor group, the second sampling resistor group, the third sampling resistor group, and the fourth sampling resistor group, respectively, and the four balancing resistor groups are named the first balancing resistor group, the second balancing resistor group, the third balancing resistor group, and the fourth balancing resistor group, respectively. The resistance values ​​of the first sampling resistor group, the second sampling resistor group, the third sampling resistor group, and the fourth sampling resistor group are all unequal.

[0026] The first sampling resistor group includes a first sampling resistor, the two ends of which are connected to one end of each of the two resistors in the first balanced resistor group. The second sampling resistor group includes a second sampling resistor, the two ends of which are connected to one end of each of the two resistors in the second balanced resistor group. The third sampling resistor group includes a third and a fourth sampling resistor connected in parallel, the two ends of which are connected to one end of each of the two resistors in the third balanced resistor group. The fourth sampling resistor group includes a fifth and a sixth sampling resistor connected in parallel, the two ends of which are connected to one end of each of the two resistors in the fourth balanced resistor group. The resistance values ​​of the resistors in the first, second, third, and fourth balanced resistor groups are all unequal.

[0027] For example, when the current range is 0.1A~15A: the resistance of the first sampling resistor is 0.1Ω, and the resistance of both resistors in the first balancing resistor group is 40kΩ; the resistance of the second sampling resistor is 0.05Ω, and the resistance of both resistors in the second balancing resistor group is 20kΩ; the resistance of the third and fourth sampling resistors is 0.05Ω, and the resistance of both resistors in the third balancing resistor group is 10kΩ; the resistance of the fifth and sixth sampling resistors is 0.01Ω, and the resistance of both resistors in the fourth balancing resistor group is 2kΩ.

[0028] In another embodiment, the differential amplifier module includes: a differential amplifier circuit, an output resistor, and a first filter capacitor. The non-inverting input of the differential amplifier circuit is connected to the non-inverting output of the balancing resistor group, the inverting input of the differential amplifier circuit is connected to the common terminal of the switching switch, and the output of the differential amplifier circuit is connected to one end of the output resistor. The positive power supply terminal of the differential amplifier circuit is connected to the positive voltage output of the dual-power supply voltage regulator module, and the negative power supply terminal of the differential amplifier circuit is connected to the negative voltage output of the dual-power supply voltage regulator module. The other end of the output resistor is connected to one end of the first filter capacitor, and the other end of the first filter capacitor is grounded. The common connection point of the output resistor and the first filter capacitor serves as the output terminal of the differential amplifier module, outputting the amplified voltage signal.

[0029] The differential amplifier circuit includes an operational amplifier, a first feedback resistor, and a second feedback resistor. One end of the first feedback resistor and the non-inverting output terminal of the balancing resistor group are connected to the non-inverting input terminal of the operational amplifier; one end of the second feedback resistor and the common terminal of the switching switch are connected to the inverting input terminal of the operational amplifier; the other end of the second feedback resistor is connected to the output terminal of the operational amplifier. The positive power supply terminal of the operational amplifier is connected to the positive output terminal of the dual power supply regulator module, and the negative power supply terminal of the operational amplifier is connected to the negative output terminal of the dual power supply regulator module. The output terminal of the operational amplifier is also connected to one end of the output resistor.

[0030] The amplification factor of the voltage signal is equal to the ratio of the feedback resistor to the first resistor.

[0031] As an optional implementation, the dual-power supply voltage regulator module includes a positive voltage regulator submodule and a negative voltage conversion submodule. The voltage input terminal of the positive voltage regulator submodule is connected to an external power supply, and the positive voltage output terminal of the positive voltage regulator submodule is connected to both the positive power input terminal of the negative voltage conversion submodule and the positive power supply terminal of the differential amplifier module; the negative voltage output terminal of the negative voltage conversion submodule is connected to the negative power supply terminal of the differential amplifier module.

[0032] In this implementation, the positive voltage regulator submodule includes: a three-terminal linear positive voltage regulator chip, a second filter capacitor, a third filter capacitor, and a fourth filter capacitor. The voltage input terminal of the three-terminal linear positive voltage regulator chip is connected to an external power supply. The voltage input terminal of the three-terminal linear positive voltage regulator chip is connected to one end of the second filter capacitor, and the other end of the second filter capacitor is grounded. The third and fourth filter capacitors are connected in parallel between the positive voltage output terminal of the three-terminal linear positive voltage regulator chip and ground. The positive voltage output terminal of the three-terminal linear positive voltage regulator chip is connected to the positive power input terminal of the negative voltage conversion submodule and the positive power input terminal of the differential amplifier module, respectively.

[0033] The negative voltage conversion submodule includes: a charge pump type negative voltage conversion chip, a fifth filter capacitor, and a sixth filter capacitor. The positive power input terminal of the charge pump type negative voltage conversion chip is connected to the positive voltage output terminal of the positive voltage regulator submodule; the fifth filter capacitor is connected between the positive and negative terminals of the charge pump type negative voltage conversion chip; the sixth filter capacitor is connected between the negative voltage output terminal and the ground terminal of the charge pump type negative voltage conversion chip; the negative voltage output terminal of the charge pump type negative voltage conversion chip is connected to the negative power supply terminal of the differential amplifier module, and the ground terminal of the charge pump type negative voltage conversion chip is grounded.

[0034] The primary drawback of existing technologies is insufficient accuracy in multi-range current detection from 0.1A to 15A, leading to a series of issues related to adaptability, stability, and cost. To address these shortcomings, this application overcomes the technical bottleneck through targeted circuit optimization design, achieving the following objectives: Core objective: To improve the detection accuracy of wide-range currents from 0.1A to 15A, control the measurement error within 3% across the entire range, and solve the core bottleneck of existing technologies that cannot simultaneously achieve both range and accuracy. Secondary objectives: ① To achieve accurate multi-range adaptation from 0.1A to 15A, using switchable high-precision sampling resistors to balance effective sampling of small currents with safe carrying of large currents, covering the entire range without additional protection circuits; ② To enhance anti-interference and power supply stability, using dual-power supply regulation and a composite filter network to suppress electromagnetic interference, power ripple, and environmental noise, ensuring stable measurement across the entire range; ③ To balance low cost and high reliability, eliminating the magnetic core and dedicated components of Hall sensors, and adopting a simple resistor sampling + adjustable gain amplification structure to reduce overall cost while avoiding magnetic saturation and component burnout, thus improving long-term operational reliability; ④ To improve real-time response and linearity, achieving real-time capture of current fluctuations in the 0.1A to 15A range, ensuring linear amplification and output of the full-range signal.

[0035] To achieve the above core and secondary objectives, the following addresses... Figure 1 The schematic diagram of the four-range current sensor shown is as follows: Figure 2 The circuit diagram of the four-range current sensor is shown, illustrating the location and labeling of the specific components in each module.

[0036] Left side of the circuit: Multi-range sampling module (including sampling resistor group, balancing resistor group, and four-position switch); Central area of ​​the circuit: Differential amplifier module (high-precision operational amplifier and feedback resistor); The right side of the circuit contains a dual-power supply voltage regulator module (positive voltage regulator chip and negative voltage conversion chip) and an anti-interference filter module (capacitor bank).

[0037] (1) Multi-range sampling module (adapted to four ranges from 0.1A to 15A) This module is located in Figure 1 On the left, used to convert current signals of different ranges into voltage signals with appropriate amplification, it includes: Sampling resistor groups (4 groups, corresponding to 4 ranges): RT1 (resistance 0.1Ω): corresponds to range 1 (0.1A~1A). RT2 (resistance 0.05Ω): corresponds to range 2 (1A~5A); RT3 and RT4 connected in parallel (each with a resistance of 0.05Ω): corresponds to range 3 (5A~10A); RT5 and RT6 connected in parallel (each with a resistance of 0.01Ω): corresponds to range 4 (10A~15A); Note: The sampling resistor value is negatively correlated with the measurement range (small resistance value is suitable for large current). By connecting multiple resistors in parallel, the power carrying capacity of the resistor can be improved while ensuring range compatibility, and the resistor can be prevented from being damaged by overload under high current.

[0038] The sampling resistor can be a high-power constantan wire sampling resistor. Its core function is to convert the measured current into a linear voltage signal that follows Ohm's law.

[0039] (2) Balancing resistor group (used to ensure the common-mode rejection ratio of differential amplification): Matching RT1: R1 (40kΩ), R2 (40kΩ); Matching RT2: R3 (20kΩ), R4 (20kΩ); Matching for RT3 and RT4: R5 (10kΩ), R6 (10kΩ); Matching for RT5 and RT6: R7 (2kΩ), R8 (2kΩ); One end of each balancing resistor is connected to the non-detection end of the corresponding sampling resistor, and the other ends are connected to the input end of the differential amplifier module.

[0040] (3) Four-position sliding switch SW1: The slide switch SW1 is an 8-pin four-position switch. Its common pins 7 and 8 are connected to the input pins 2 and 3 of the differential amplifier module U1. The 6 pins of the switch correspond to 4 sets of selection switches, which are respectively connected to the "detection terminals" of 4 sets of sampling resistors (i.e., each set of sampling resistors is connected to one end of the balancing resistor). Switch position 1 → Detection terminal of the first group of sampling resistors (convergence point of R1 / R2); Switch position 2 → Detection terminal of the second group of sampling resistors (convergence point of R3 / R4); Switch position 3 → Detection terminal of the third group of sampling resistors (convergence point of R5 / R6); Switch position 4 → Detection terminal of the 4th group of sampling resistors (convergence point of R7 / R8).

[0041] By switching positions using the lever on SW1, the corresponding group of sampling resistors can be connected to the circuit. At the same time, the balancing resistor will synchronously match the group of sampling resistors to ensure the common-mode rejection ratio of the differential amplifier.

[0042] (4) Differential amplifier module (signal amplification) This module is located in Figure 1In the middle section, the core component is the high-precision operational amplifier U1 (OP07, low offset voltage operational amplifier). OP07 is a high-precision operational amplifier with low temperature drift and low input offset voltage, used to construct differential amplifier circuits to precisely amplify the minute voltage generated by RT. The component connections are as follows: Pin 3 of U1 (non-inverting input): Connects to pin 8 of SW1 and receives the non-inverting voltage signal output by the sampling resistor; Pin 2 of U1 (inverting input): Connects to pin 7 of SW1, connects to the convergence terminal of the balancing resistor group, and receives the inverted voltage signal output by the sampling resistor. Pin 7 of U1 (positive power supply terminal): Connects to the +9V output terminal of the dual power supply regulator module; Pin 4 of U1 (negative power supply terminal): Connects to the -9V output terminal of the dual power supply regulator module; Feedback resistor group (R9: 400kΩ, R10: 400kΩ): The two ends are connected to pin 3 (non-inverting input) and pin 2 (inverting input) of U1 respectively, forming a differential amplifier circuit with amplification factors of "R9 / R1 (corresponding to range 1)", "R9 / R3 (corresponding to range 2)", "R9 / R5 (corresponding to range 3)" and "R9 / R7 (corresponding to range 4)". The "range-amplification factor" adaptation is achieved by switching the sampling resistor value. Output resistor R11 (10kΩ): One end is connected to pin 6 of U1, and the other end is the signal output terminal of the circuit; Output filter capacitor C4 (1uF): One end is connected to the output terminal of R6, and the other end is grounded. It is used to filter out high-frequency noise in the amplified signal.

[0043] For example, the OP07 can be replaced with the LM358, which can reduce the cost by 50%, but the accuracy will be slightly reduced. It is suitable for scenarios with high tolerance for error.

[0044] (5) Dual power supply voltage regulator module (to supply power to the amplifier circuit) This module is located in Figure 1 On the right side, a -9V stable power supply is provided, including: ① Positive voltage regulator submodule: U2 (7809, 3-Terminal Linear Voltage Regulator): Pin 1 (voltage input) connects to an external +24V power supply, pin 3 (voltage output) outputs +9V, and pin 2 (ground) is grounded. This 3-Terminal Linear Voltage Regulator receives a 12-24V DC input and outputs a stable +9V, providing positive power to the operational amplifier and peripheral circuits. Input filter capacitor C2 (0.33uF): one end is connected to pin 1 of U2, and the other end is grounded; Output filter capacitors C3 (0.1uF) and C1 (10uF): connected in parallel between pin 3 of U2 and ground to suppress the ripple of the +9V power supply.

[0045] ② Negative pressure conversion submodule: U3 (ICL7660, charge pump type negative voltage converter chip): Pin 8 (positive power input terminal) is connected to the +9V output terminal of U2, pin 5 (negative voltage output terminal, VOUT) outputs -9V, and pin 3 (ground terminal) is grounded; the charge pump type negative voltage converter chip can convert +9V positive voltage to -9V negative voltage, providing dual power supply for OP07 and avoiding output zero-point drift caused by a single power supply; Capacitor C5 (10uF, polarized capacitor): Connects pin 2 (CAP+) and pin 4 (CAP-) of U3 to achieve charge transfer and voltage reversal; Output filter capacitor C6 (10uF, polarized electrolytic capacitor): The negative terminal is connected to pin 5 of U3, and the positive terminal is grounded to filter out the ripple of the -9V power supply.

[0046] (6) Anti-interference filtering module This module is distributed across various functional modules and includes: Power supply filter capacitors (C1, C2, C5, C6): suppress power supply ripple; Output filter capacitor C4: suppresses high-frequency noise in the amplified signal; Impedance matching design of sampling resistor and balancing resistor: Reduces coupling interference from environmental electromagnetic noise.

[0047] This application achieves multi-range current detection from 0.1A to 15A through the following steps: Based on the estimated range of the measured current, rotate SW1 to switch to the corresponding range: Estimated 0.1A~1A: Switch to RT1 (0.01Ω) setting; Estimated 1A~5A: Switch to RT2 (0.05Ω) setting; Estimated 5A~10A: Switch to RT3 in parallel with RT4 (0.05Ω) setting; Estimated 10A~15A: Switch to RT5 in parallel with RT6 (0.01Ω) setting; Connect the circuit to be measured in series to the detection terminal of the corresponding sampling resistor (e.g., connect range 1 to the left terminal WJ1 of sampling RT1); connect the external +24V power supply, the dual power supply voltage regulator module outputs ±9V, and the differential amplifier module enters the working state. The amplified voltage signal is obtained from the output of R11. Since the amplification factor is designed, the output voltage value is the measured current value.

[0048] This application achieves high-precision detection based on a synergistic mechanism of "current-to-voltage conversion + differential amplification + dual power supply regulation": Current-to-voltage conversion: The measured current flows through the selected sampling resistors (RT1~RT6) and is converted into a weak voltage signal according to Ohm's law (voltage value = current value × resistance value of the currently connected sampling resistor). Differential Amplification: The OP07 operational amplifier receives the differential signal of the sampled voltage through a balanced resistor group (R1~R8), and uses a differential amplifier circuit composed of feedback resistors (R9, R10) to amplify the weak voltage signal to an amplitude that matches the acquisition value at the back end. Dual power supply regulation: The 7809 module outputs a +9V positive power supply, and the ICL7660 module converts the +9V to a -9V negative power supply. The dual power supply accurately supplies the positive and negative power terminals of the OP07, avoiding signal clipping distortion caused by single power supply and greatly expanding the linear amplification range of the circuit. Anti-interference filtering: The power supply capacitors (C1~C3, C6) filter out the high and low frequency ripple of the ±9V power supply, and the signal capacitor (C4) suppresses the high frequency noise of the amplified signal. Combined with the impedance matching design of the balanced resistor group, common-mode interference is effectively suppressed, and finally high-precision current detection with a wide range of 0.1A~15A is achieved.

[0049] Figure 3 The PCB layout of a four-range current sensor is shown. The double-sided board of this current sensing circuit measures 4.80cm × 4.71cm and employs a top and bottom partitioned layout design, as shown below. Figure 4 and Figure 5 As shown, this approach balances the rationality of wiring with the centralization of functional modules: Top-level layout: Core functional components are centrally deployed, including a sliding switch (SW1) for range switching, five dual-interface terminals (WJ1~WJ5) for external connection of measured current and power supply, one single-interface auxiliary terminal (DB1P), and constantan wire resistors (RT1~RT6) adapted to ranges of 0.1A~15A. These components are all located on the top layer to facilitate manual operation, external wiring, and heat dissipation of high-current sampling resistors.

[0050] Bottom layer layout: The core chips are centrally arranged, with the operational amplifier module U1 (OP07), the positive voltage regulator module U2 (7809), and the negative voltage converter module U3 (ICL7660) all placed at the bottom layer. This shortens the power supply and signal connection length between chips and avoids interference from top layer components to the chips. Distribution of resistors and capacitors: Resistors (R1~R11) and capacitors (C1~C6) are distributed on the top and bottom layers according to the convenience of actual wiring. Resistor and capacitor components connected to the top layer terminals and sliding switches are deployed on the top layer, while resistor and capacitor components directly connected to the bottom layer chip pins are deployed on the bottom layer. This effectively reduces the number of cross-layer connections and improves the signal transmission efficiency and stability of the circuit.

[0051] Using the current signal generated by the solenoid valve as the detection object, Figure 6 The Proteus simulation test diagram of the sampling resistive current sensor shown is presented, and the simulation verifies the effectiveness of the current detection in this application. The solenoid valve current test results are as follows: Figure 7 As shown, Figure 7 Part (a) shows the current detection results. Figure 7 Part (b) shows the control signal that controls the current generated by the solenoid valve. This control signal is a pulse width modulation signal.

[0052] The key points of this application are: 1. Component-range input: The adjustable multi-channel input is designed with sampling resistors, which can be adapted to different inputs without additional modifications, thus improving the versatility of the circuit.

[0053] 2. Differential amplifier anti-interference design: The differential amplifier circuit is constructed using OP07, and common-mode signal cancellation is achieved with the help of the balanced resistor group (R1~R8). At the same time, a negative feedback loop is formed through the symmetrical feedback resistor (R9=R10), which greatly improves the common-mode rejection ratio of the circuit and effectively suppresses common-mode noise such as electromagnetic interference and power supply ripple. This solves the core problem of weak anti-interference capability of traditional single-ended amplifier circuits.

[0054] 3. Dual power supply regulation structure: The OP07 is provided with dual power supply through the combination of "7809 (+9V) + ICL7660 (-9V)" to avoid zero-point drift caused by single power supply. At the same time, multiple capacitors on the power supply side filter to reduce ripple and ensure power supply stability.

[0055] 4. Low-impedance, high-precision sampling + RC filtering design: High-precision constantan wire sampling resistor group (RT1~RT6) is selected. The low resistance value can reduce the voltage division loss under high current. At the same time, the low temperature drift characteristic of constantan wire ensures the linearity of the full-range current-to-voltage conversion. An RC filter circuit is added at the signal output end to further filter out high-frequency noise in the amplified signal, effectively improving the purity of the output signal.

[0056] Accordingly, the advantages of this application are as follows: 1. Strong range adaptability (disadvantage of poor range adaptability) Existing solutions cannot cover a wide range; this application uses a four-position switch to quickly switch the sampling resistor, covering 0.1A~15A without replacing the core components, adapting to multiple scenarios and greatly improving ease of use.

[0057] 2. Core Advantage: Significantly improved accuracy in multi-range detection (corresponding to core disadvantage) Existing technologies suffer from large full-range errors due to Hall sensor core saturation, poor adaptability of single sampling resistors, and other issues. This application, through the design of four sets of differentiated sampling resistors, a switching mechanism, and amplification factor, ensures linear conversion across the entire range of 0.1A to 15A, with a measurement error ≤5%, and can directly output the magnitude of the measured current.

[0058] 3. Enhanced anti-interference capability (corresponding to the weakness of weak anti-interference capability) Existing Hall sensors are susceptible to magnetic field interference, and traditional solutions lack filtering; this application adopts a balanced resistor group + composite filtering + differential amplification to ensure the purity of weak signals.

[0059] 4. Improved power supply stability (addressing single power supply defects) Existing single power supply leads to operational amplifier distortion and large drift; this application uses a dual power supply architecture (7809+ICL7660) with filtering, which provides sufficient linear range for the operational amplifier and reduces the impact of power supply fluctuations.

[0060] 5. Low cost, high reliability, and fast response (corresponding to cost imbalance and response lag) Existing Hall sensors are expensive and have slow response; this application abandons the magnetic coupling design, reducing costs by 3 to 5 times, eliminating magnetic saturation problems, and achieving a response speed of ≤1ms, enabling real-time capture of current fluctuations.

[0061] Compared with the prior art, this application has the following advantages: 1. Multi-range data acquisition, highly adaptable; 2. High current detection accuracy and strong anti-interference capability; 3. It adopts dual power supply, resulting in good signal linearity; 4. The circuit structure is simple, easy to implement and promote.

[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A sampling resistance current sensor, characterized in that, include: Multi-range sampling module, differential amplifier module, and dual-power supply voltage regulator module; The multi-range sampling module is used to convert current signals of different ranges into voltage signals; The multi-range sampling module includes multiple sampling resistor groups corresponding to different current ranges, multiple balancing resistor groups, and a switching switch. When measuring current, the sampling resistor group matching the current range of the current loop being measured is connected in series with the current loop being measured. The two ends of one sampling resistor group are respectively connected to the two input terminals of one balancing resistor group. The non-inverting output terminal of one balancing resistor group is connected to the non-inverting input terminal of the differential amplifier module, and the inverting output terminal of one balancing resistor group is connected to one switch position of the switching switch. The common terminal of the switching switch is connected to the inverting input terminal of the differential amplifier module. The positive power supply terminal of the differential amplifier module is connected to the positive output terminal of the dual power supply voltage regulator module, and the negative power supply terminal of the differential amplifier module is connected to the negative output terminal of the dual power supply voltage regulator module. The dual power supply voltage regulator module is used to provide positive and negative power supplies to the differential amplifier module. The differential amplifier module is used to amplify the voltage signal according to a preset amplification factor and output the amplified voltage signal. The value of the amplified voltage signal is equal to the current value of the current loop being measured.

2. The sampling resistive current sensor according to claim 1, characterized in that, The balancing resistor group includes: a first resistor and a second resistor with the same resistance value; One end of the first resistor is connected to one end of the sampling resistor group; the other end of the first resistor serves as the non-inverting output terminal of the balancing resistor group and is connected to the non-inverting input terminal of the differential amplifier module. One end of the second resistor is connected to the other end of the sampling resistor group; the other end of the second resistor serves as the inverting output terminal of the balancing resistor group and is connected to one of the switching positions of the switch.

3. The sampling resistive current sensor according to claim 2, characterized in that, When the number of sampling resistor groups and balancing resistor groups is 4, the 4 sampling resistor groups are named the first sampling resistor group, the second sampling resistor group, the third sampling resistor group and the fourth sampling resistor group, respectively, and the 4 balancing resistor groups are named the first balancing resistor group, the second balancing resistor group, the third balancing resistor group and the fourth balancing resistor group, respectively. The resistance values ​​of the first sampling resistor group, the second sampling resistor group, the third sampling resistor group, and the fourth sampling resistor group are all different; The first sampling resistor group includes a first sampling resistor, and the two ends of the first sampling resistor are respectively connected to one end of each of the two resistors in the first balanced resistor group; The second sampling resistor group includes a second sampling resistor, and the two ends of the second sampling resistor are respectively connected to one end of each of the two resistors in the second balanced resistor group; The third sampling resistor group includes a third sampling resistor and a fourth sampling resistor connected in parallel. The two ends of the third sampling resistor and the fourth sampling resistor connected in parallel are respectively connected to one end of each of the two resistors in the third balancing resistor group. The fourth sampling resistor group includes a fifth sampling resistor and a sixth sampling resistor connected in parallel. The two ends of the fifth sampling resistor and the sixth sampling resistor connected in parallel are respectively connected to one end of each of the two resistors in the fourth balancing resistor group. The resistance values ​​in the first, second, third, and fourth balanced resistor groups are all different.

4. The sampling resistive current sensor according to claim 3, characterized in that, When the current range is 0.1A~15A: The resistance of the first sampling resistor is 0.1Ω, and the resistance of each of the two resistors in the first balancing resistor group is 40kΩ. The resistance of the second sampling resistor is 0.05Ω, and the resistance of both resistors in the second balancing resistor group is 20kΩ. The resistance values ​​of the third and fourth sampling resistors are both 0.05Ω, and the resistance values ​​of the two resistors in the third balancing resistor group are both 10kΩ. The fifth and sixth sampling resistors both have a resistance of 0.01Ω, and the two resistors in the fourth balancing resistor group both have a resistance of 2kΩ.

5. The sampling resistive current sensor according to claim 2, characterized in that, The differential amplifier module includes: a differential amplifier circuit, an output resistor, and a first filter capacitor; The non-inverting input of the differential amplifier circuit is connected to the non-inverting output of the balancing resistor group, the inverting input of the differential amplifier circuit is connected to the common terminal of the switching switch, and the output of the differential amplifier circuit is connected to one end of the output resistor. The positive power supply terminal of the differential amplifier circuit is connected to the positive output terminal of the dual power supply regulator module, and the negative power supply terminal of the differential amplifier circuit is connected to the negative output terminal of the dual power supply regulator module. The other end of the output resistor is connected to one end of the first filter capacitor, and the other end of the first filter capacitor is grounded; the common point of connection between the output resistor and the first filter capacitor serves as the output terminal of the differential amplifier module, which outputs the amplified voltage signal.

6. The sampling resistive current sensor according to claim 5, characterized in that, The differential amplifier circuit includes: an operational amplifier, a first feedback resistor, and a second feedback resistor; One end of the first feedback resistor and the non-inverting output of the balancing resistor group are both connected to the non-inverting input of the operational amplifier; one end of the second feedback resistor and the common terminal of the switching switch are both connected to the inverting input of the operational amplifier; the other end of the second feedback resistor is connected to the output of the operational amplifier. The positive power supply terminal of the operational amplifier is connected to the positive output terminal of the dual power supply regulator module, and the negative power supply terminal of the operational amplifier is connected to the negative output terminal of the dual power supply regulator module. The output of the operational amplifier is also connected to one end of the output resistor.

7. The sampling resistive current sensor according to claim 6, characterized in that, The amplification factor of the voltage signal is equal to the ratio of the feedback resistor to the first resistor.

8. The sampling resistive current sensor according to claim 1, characterized in that, The dual-power voltage regulator module includes: a positive voltage regulator submodule and a negative voltage conversion submodule; The voltage input terminal of the positive voltage regulator submodule is connected to an external power supply. The positive voltage output terminal of the positive voltage regulator submodule is connected to the positive power input terminal of the negative voltage converter submodule and the positive power supply terminal of the differential amplifier module, respectively. The negative voltage output terminal of the negative voltage converter submodule is connected to the negative power supply terminal of the differential amplifier module.

9. The sampling resistive current sensor according to claim 8, characterized in that, The positive voltage regulator submodule includes: a three-terminal linear positive voltage regulator chip, a second filter capacitor, a third filter capacitor, and a fourth filter capacitor; The voltage input terminal of the three-terminal linear positive voltage regulator chip is connected to an external power supply. The voltage input terminal of the three-terminal linear positive voltage regulator chip is connected to one end of the second filter capacitor, and the other end of the second filter capacitor is grounded. The third and fourth filter capacitors are connected in parallel between the positive output terminal of the three-terminal linear positive regulator chip and ground. The positive output terminal of the three-terminal linear positive voltage regulator chip is connected to the positive power input terminal of the negative voltage conversion submodule and the positive power input terminal of the differential amplifier module, respectively.

10. The sampling resistive current sensor according to claim 8, characterized in that, The negative voltage conversion submodule includes: a charge pump type negative voltage conversion chip, a fifth filter capacitor, and a sixth filter capacitor; The positive power input terminal of the charge pump type negative voltage conversion chip is connected to the positive voltage output terminal of the positive voltage regulator submodule; The fifth filter capacitor is connected between the positive and negative terminals of the capacitor in the charge pump type negative voltage converter chip; The sixth filter capacitor is connected between the negative voltage output terminal and the ground terminal of the charge pump type negative voltage conversion chip; The negative voltage output terminal of the charge pump type negative voltage conversion chip is connected to the negative power supply terminal of the differential amplifier module, and the ground terminal of the charge pump type negative voltage conversion chip is grounded.

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