Current sampling circuit, current measuring instrument and monitoring device

Abstract

The utility model discloses a current sampling circuit, current measuring instrument and monitoring equipment, current sampling circuit includes: sampling resistance, amplifier, first operational amplifier and second operational amplifier, the first input of amplifier is connected with the first end of sampling resistance, and the second input is connected with the second end of sampling resistance, the noninverting input of first operational amplifier is connected with the first end of sampling resistance and is the negative input of current sampling circuit, and the output of first operational amplifier is connected with the second end of sampling resistance, the noninverting input of second operational amplifier is connected with the noninverting input of first operational amplifier, and the noninverting input of second operational amplifier is connected with the output and is the positive input of current sampling circuit. The technical scheme passes through first operational amplifier and second operational amplifier, and makes the equivalent internal resistance of sampling resistance to external circuit zero, thereby avoid the loop voltage loss of traditional current sampling circuit because of sampling resistance.

Description

Technical Field

[0001] This utility model relates to the field of current measurement technology, and in particular to a current sampling circuit, a current measuring instrument, and a monitoring device. Background Technology

[0002] Current sampling is a fundamental function in electronic measurement and control systems, widely used in digital multimeters, sensor signal acquisition, precision testing instruments, and medical testing equipment. A common current sampling method involves connecting a sampling resistor in series with the current being measured. The current value is indirectly obtained by detecting the voltage drop across the sampling resistor, and then amplified and processed by an amplifier.

[0003] However, this type of traditional current sampling circuit has a significant drawback: its input resistance is equal to the resistance of the sampling resistor. When the sampling resistor is large, it introduces a non-negligible voltage drop in the circuit. For example, in the low current range of a high-precision digital multimeter, a sampling resistor of tens or even hundreds of ohms is often required to ensure sampling accuracy. But in this case, a large voltage drop will occur in the current path, which not only changes the operating state of the measured object but may also lead to measurement errors. Utility Model Content

[0004] This utility model provides a current sampling circuit, a current measuring instrument, and a monitoring device to solve the above-mentioned technical problems.

[0005] The first aspect of this utility model provides a current sampling circuit, including: Sampling resistor; An amplifier, wherein its first input terminal is connected to the first terminal of the sampling resistor, and the second input terminal of the amplifier is connected to the second terminal of the sampling resistor; A first operational amplifier, wherein the inverting input terminal of the first operational amplifier and the first terminal of the sampling resistor are connected together as the negative input terminal of the current sampling circuit, and the output terminal of the first operational amplifier is connected to the second terminal of the sampling resistor; The second operational amplifier has its non-inverting input connected to the non-inverting input of the first operational amplifier, and its inverting input and output are connected together as the positive input of the current sampling circuit.

[0006] Optionally, the first operational amplifier adjusts the potential difference across the sampling resistor to make the equivalent input resistance of the current sampling circuit zero.

[0007] Optionally, the inverting input terminal and the output terminal of the second operational amplifier receive the input current signal to isolate and buffer the input current signal.

[0008] Optionally, the amplifier is an instrumentation amplifier to differentially amplify the voltage formed by the sampling resistor.

[0009] Optionally, the output voltage Uoutput of the current sampling circuit satisfies the following formula: Uoutput = IINTPUT × RS × G; Where IINTPUT is the input current, RS is the resistance of the sampling resistor, and G is the gain of the amplifier.

[0010] Optionally, the current sampling circuit further includes a temperature detection module and a gain correction module. The temperature detection module is arranged adjacent to the sampling resistor. The output terminal of the temperature detection module is connected to the input terminal of the gain correction module, and the output terminal of the gain correction module is connected to the control terminal of the amplifier.

[0011] Optionally, the amplifier is a gain-adjustable amplifier.

[0012] A second aspect of this utility model provides a current measuring instrument, including the current sampling circuit provided in the first aspect.

[0013] Optionally, the current measuring instrument further includes: a signal processing module, a display module, and a power supply module. The input terminal of the signal processing module is connected to the output terminal of the amplifier, the output terminal of the signal processing module is connected to the input terminal of the display module, and the power supply module is connected to the amplifier, the first operational amplifier, the second operational amplifier, the signal processing module, and the display module.

[0014] A third aspect of this utility model provides a monitoring device, including the current measuring instrument described in the second aspect.

[0015] The technical advantages of this embodiment are as follows: By introducing a first operational amplifier and a second operational amplifier across the sampling resistor, the equivalent internal resistance of the sampling resistor to the external circuit is made zero, thereby avoiding the loop voltage loss caused by the sampling resistor in traditional current sampling circuits. This circuit can achieve high-precision current sampling in micro-current and small-range measurement scenarios, and is particularly suitable for applications with strict requirements for circuit internal resistance voltage drop, such as high-precision measuring instruments, sensor signal acquisition, and medical testing. Attached Figure Description

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

[0017] Figure 1 This is a schematic diagram of the first structure of a current sampling circuit provided in Embodiment 1 of this utility model; Figure 2 This is a circuit diagram of a current sampling circuit provided in Embodiment 1 of this utility model; Figure 3 This is a schematic diagram of a second structure of a current sampling circuit provided in Embodiment 1 of this utility model; Figure 4 This is a schematic diagram of the structure of a current measuring instrument provided in Embodiment 2 of this utility model; In the diagram: 101, sampling resistor; 102, amplifier; 103, first operational amplifier; 104, second operational amplifier; 201, temperature detection module; 202, gain correction module; 301, signal processing module; 302, display module; 303, power supply module. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model.

[0019] It should be understood that this invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of this invention to those skilled in the art. In the drawings, for clarity, the dimensions of layers and regions, as well as their relative dimensions, may be exaggerated. The same reference numerals denote the same elements throughout.

[0020] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this utility model, the first element, component, area, layer, or portion discussed below may be referred to as the second element, component, area, layer, or portion.

[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0022] To fully understand this utility model, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by this utility model. Preferred embodiments of this utility model are described in detail below; however, in addition to these detailed descriptions, this utility model may have other embodiments.

[0023] Example 1 This embodiment provides a current sampling circuit, such as Figure 1 As shown, it includes: Sampling resistor 101; Amplifier 102 has its first input terminal connected to the first terminal of sampling resistor 101, and its second input terminal connected to the second terminal of sampling resistor 101. The first operational amplifier 103 has its inverting input terminal and the first terminal of the sampling resistor 101 connected together as the negative input terminal of the current sampling circuit, and its output terminal is connected to the second terminal of the sampling resistor 101. The second operational amplifier 104 has its non-inverting input connected to the non-inverting input of the first operational amplifier 103, and its inverting input and output are connected together as the positive input of the current sampling circuit.

[0024] The sampling resistor 101 is placed in the current sampling circuit to convert the input current into a voltage signal. When current flows through the sampling resistor 101, a voltage difference is generated across it, which carries information about the magnitude of the input current.

[0025] Amplifier 102 amplifies the voltage difference across sampling resistor 101 to obtain an output voltage signal proportional to the input current. Preferably, it is an instrumentation amplifier with high input impedance and high common-mode rejection ratio, ensuring accurate current sampling.

[0026] Specifically, the first operational amplifier 103 adjusts the potential difference across the sampling resistor 101 to make the equivalent input resistance of the current sampling circuit zero. By adjusting the output through the virtual short characteristic of the operational amplifier, the potential difference across the sampling resistor 101 is brought close to zero, thereby achieving a near-zero equivalent input resistance of the current sampling circuit and avoiding voltage loss introduced into the loop by the sampling resistor 101.

[0027] In this circuit, the non-inverting input of the second operational amplifier 104 is connected to the non-inverting input of the first operational amplifier 103; the inverting input and output are connected together, forming a voltage follower structure; the common connection point of the inverting input and output serves as the positive input of the current sampling circuit, used to receive the input current. Its function is to isolate and buffer the input current signal before outputting it, featuring high input impedance and low output impedance, ensuring the stability and accuracy of signal transmission while avoiding interference with the preceding circuitry.

[0028] The technical advantages of this embodiment are as follows: By introducing a first operational amplifier 103 and a second operational amplifier 104 across the sampling resistor 101, the equivalent internal resistance of the sampling resistor 101 to the external circuit is made zero, thereby avoiding the loop voltage loss caused by the sampling resistor 101 in traditional current sampling circuits. This circuit can achieve high-precision current sampling in micro-current, small-range measurement scenarios, and is particularly suitable for applications with strict requirements for circuit internal resistance voltage drop, such as high-precision measuring instruments, sensor signal acquisition, and medical testing.

[0029] As one implementation method, the output voltage U of the current sampling circuit output Satisfy the following formula: U output =I INTPUT ×R×G; Among them, I INTPUTR is the input current, R is the resistance of the sampling resistor, and G is the gain of the amplifier.

[0030] In actual operation, the input current I INTPUT The current flows through sampling resistor 101, forming a voltage signal across it. This voltage signal serves as the input to amplifier 102, where it is amplified by gain G, ultimately resulting in an output voltage U proportional to the input current at the circuit output. output Since the first operational amplifier 103 maintains the potential difference across the sampling resistor 101 at near zero through negative feedback, the sampling resistor 101 does not introduce additional voltage loss in the input circuit. Therefore, the formula for calculating the output voltage can accurately reflect the linear relationship between the input current, the sampling resistor 101, and the amplifier gain.

[0031] The technical advantages of this implementation are as follows: Through this formula, the circuit achieves precise linear conversion between current and voltage, ensuring high accuracy and predictability of current sampling; under different ranges, only the resistance value of sampling resistor 101 or the gain G of the amplifier needs to be adjusted to flexibly adapt to different input current ranges; it maintains the characteristic of zero equivalent internal resistance, avoiding the loop voltage drop problem introduced by sampling resistor 101, thus making it suitable for detection applications with extremely high requirements for accuracy and internal resistance.

[0032] As an example, such as Figure 2 As shown, amplifier 101 is instrumentation amplifier U1, sampling resistor 102 is resistor RS, first operational amplifier 103 is operational amplifier U2A, second operational amplifier 104 is operational amplifier U2B, and INPUT+ and INPUT- are inputs. This circuit has the following characteristics: Due to the virtual short-circuit characteristics of operational amplifiers U2A and U2B, the circuit input internal resistance is zero. Due to the virtual open-circuit characteristics of operational amplifiers U2A, U2B, and instrumentation amplifier U1, the current flowing through resistor RS is equal to the input current. RS =I INTPUT Circuit output voltage U output =I INTPUT *RS*G, when the measurement range is relatively small and the sampling resistor value is relatively large, the resistor RS will not introduce loop voltage loss during the test, which is suitable for application scenarios with high requirements for internal resistance voltage drop.

[0033] As one implementation method, such as Figure 3 As shown, the current sampling circuit also includes a temperature detection module 201 and a gain correction module 202. The temperature detection module 201 is arranged adjacent to the sampling resistor 101. The output terminal of the temperature detection module 201 is connected to the input terminal of the gain correction module 202, and the output terminal of the gain correction module 202 is connected to the control terminal of the amplifier 102.

[0034] The temperature detection module 201 can be a negative temperature coefficient thermistor (NTC), a positive temperature coefficient thermistor (PTC), a semiconductor temperature sensor, or an integrated temperature detection chip. Its mounting position is close to the sampling resistor 101 to ensure that the detected temperature matches the actual operating temperature of the sampling resistor 101. The temperature detection module 201 outputs a voltage or current signal proportional to the temperature, which is provided to the gain correction module 202.

[0035] The gain correction module 202 includes, but is not limited to, the following structures: (1) Analog structure: It consists of a variable resistor network, a voltage-controlled amplifier (VGA) or a thermistor feedback network. When the temperature rises and the resistance of the sampling resistor increases, the gain correction module automatically reduces the gain coefficient of the amplifier; when the temperature drops, the gain coefficient is appropriately increased, thereby maintaining the linear stability of the output signal.

[0036] (2) Digital structure: includes an analog-to-digital converter (ADC), a microcontroller unit (MCU), and a digital potentiometer or programmable gain amplifier (PGA). The temperature signal output from the temperature detection module is converted by the ADC and then input to the MCU. The MCU calculates a correction coefficient based on a preset temperature-gain relationship and transmits it via I... 2 The gain settings of a digital potentiometer or PGA can be controlled via C or SPI bus to achieve temperature-adaptive closed-loop regulation.

[0037] (3) Photoelectric structure: It adopts an optical coupling network composed of a photoresistor and a light-emitting diode (LED). The LED is driven by a temperature signal. The change in its light intensity causes the resistance of the photoresistor to change, thereby indirectly adjusting the feedback impedance of the amplifier, realizing non-contact gain control, and has good electrical isolation performance.

[0038] With the above structure, when the temperature detection module detects a temperature change in the sampling resistor, the gain correction module outputs a control signal to the amplifier's control terminal in real time to dynamically adjust the amplifier's gain, thereby adjusting the output voltage U of the current sampling circuit. output Satisfy the following formula: U output =I INTPUT ×R S (T)×G S (T); Among them, I INTPUT R is the current flowing through the sampling resistor. S (T) represents the actual temperature value of the sampling resistor at temperature T, and G S (T) is the actual gain coefficient of the amplifier at temperature T, which is dynamically adjusted by the gain correction module to compensate for the temperature drift of the sampling resistor.

[0039] The technical advantage of this embodiment is that by introducing a temperature detection module and a gain correction module into the current sampling circuit, it can automatically compensate for the resistance deviation of the sampling resistor caused by temperature changes, thus ensuring that the amplifier output voltage remains stable under different temperature conditions. This embodiment significantly improves the temperature stability and long-term accuracy of current sampling, reduces measurement errors caused by environmental temperature drift, and is particularly suitable for applications with strict requirements for temperature drift, such as outdoor equipment, high-precision instruments, and medical testing.

[0040] Optionally, amplifier 102 is a gain-adjustable amplifier.

[0041] The gain-adjustable amplifier is used to differentially amplify the voltage signal across the sampling resistor and automatically adjust its internal gain coefficient according to the control signal output by the gain correction module, thereby achieving adaptive amplification of the input signal.

[0042] Specifically, the gain-adjustable amplifier can take one of the following structural forms: (1) Voltage-controlled structure: The amplifier has an internal control port for receiving external analog control voltage signals. The gain correction module generates a control voltage proportional to the temperature based on the temperature signal output by the temperature detection module, and inputs it to the amplifier control terminal to change the ratio of its internal feedback resistor and dynamically adjust the amplification factor. This type of structure can be implemented by a voltage-controlled amplifier (VGA, Variable Gain Amplifier), such as the AD8336 and LMH6502.

[0043] (2) Digitally controlled structure: A programmable gain network is set inside or outside the amplifier, and the gain correction module is connected through a digital interface (such as I). 2 The amplifier sends digital control commands (either C or SPI) to the amplifier to select a preset gain level (e.g., ×1, ×2, ×5, ×10). This scheme can be implemented using a programmable gain amplifier (PGA) or by connecting a digital potentiometer in series in the amplifier feedback path.

[0044] (3) Hybrid control structure: The voltage control and digital control are combined. First, the temperature signal is read by the microcontroller and the target gain value is calculated. Then, the corresponding analog voltage signal is output to control the amplifier, thereby achieving dual adjustment of high precision and high response speed.

[0045] When the temperature detection module detects an increase in the temperature of the sampling resistor, the gain correction module generates a control signal to reduce the amplification factor of the gain-adjustable amplifier; when the temperature decreases, the amplification factor increases accordingly, thereby offsetting the output offset caused by the change in the resistance value of the sampling resistor.

[0046] The technical advantage of this implementation is that, by employing a gain-adjustable amplifier, the current sampling circuit can automatically adjust the amplification ratio under different temperatures and input current amplitudes, achieving high-precision, wide dynamic range signal amplification. This design not only compensates for the temperature drift error of the sampling resistor but also enables the circuit to have adaptive measurement capabilities, making it particularly suitable for high-precision digital multimeters, sensor detection modules, and medical current monitoring equipment.

[0047] Example 2 Embodiment 2 of the present invention provides a current measuring instrument, including the current sampling circuit provided in Embodiment 1.

[0048] The current sampling circuit is used to acquire the measured current in real time. Its core components include a sampling resistor 101, an amplifier 102, a first operational amplifier 103, and a second operational amplifier 104. Through the virtual shorting effect of the first operational amplifier 103, the equivalent internal resistance of the sampling resistor 101 at the input terminal is made close to zero, avoiding the voltage loss introduced in the loop by the traditional current sampling method. At the same time, through the virtual shorting and voltage following function of the second operational amplifier 104, the input current signal is isolated and buffered, ensuring the stability of the sampling results.

[0049] Furthermore, such as Figure 4 As shown, the current measuring instrument also includes: a signal processing module 301, a display module 302, and a power supply module 303. The input terminal of the signal processing module 301 is connected to the output terminal of the amplifier 102, and the output terminal of the signal processing module 301 is connected to the input terminal of the display module 302. The power supply module 303 is connected to the amplifier 102, the first operational amplifier 103, the second operational amplifier 104, the signal processing module 301, and the display module 302.

[0050] The signal processing module 301 is connected to the output of the current sampling circuit and is used to perform analog-to-digital conversion, filtering and arithmetic processing on the amplified voltage signal to obtain the corresponding current value. The display module 302 is connected to the signal processing module 301 and is used to display the measured current value in digital or graphical form. The power supply module 303 is used to provide a stable power supply for the current sampling circuit, the signal processing module 301 and the display module 302.

[0051] In this embodiment, the current measuring instrument utilizes the current sampling circuit of Embodiment 1 to achieve high-precision current detection. Especially in the case of micro-current and small-range measurement scenarios, it can ensure that the measurement does not cause additional interference to the circuit under test.

[0052] By applying the current sampling circuit of Embodiment 1 to a current measuring instrument, Embodiment 2 achieves the following technical effects: it avoids the loop voltage drop introduced by the sampling resistor 101, maintaining the working stability of the measured loop; different ranges of current measurement can be achieved by selecting different sampling resistors 101 and amplifier gains; and the integrity and accuracy of the measurement signal are ensured by the second operational amplifier 104, making it suitable for applications such as digital multimeters, sensor detection, and medical testing equipment.

[0053] As an example, the current sampling circuit of Embodiment 1 is applied to the microcurrent range of a six-and-a-half-digit digital multimeter.

[0054] Within this measurement range, the typical input current range is 0–100 μA. To ensure measurement accuracy, traditional methods require the use of a sampling resistor with a relatively large resistance (e.g., 100 Ω to 1 kΩ) to generate a sufficient voltage signal for the amplifier to detect. However, this method introduces a significant voltage drop in the loop, causing voltage distortion in the circuit under test and affecting measurement accuracy.

[0055] In this embodiment, the current sampling circuit of Embodiment 1 is used: the sampling resistor 101 is selected as 1 kΩ, which is used to convert the 100μA current into a 100 mV voltage signal; the first operational amplifier 103 is adjusted by negative feedback to ensure that the potential difference across the sampling resistor 101 is close to zero, thereby eliminating the equivalent internal resistance of the input terminal and avoiding the loop voltage loss caused by the sampling resistor 101; the second operational amplifier 104 acts as a voltage follower to isolate and buffer the voltage signal generated by the sampling resistor 101 to ensure stable signal transmission; the instrumentation amplifier amplifies the buffered voltage signal.

[0056] The technical advantages of this implementation are as follows: even if the sampling resistor is as high as 1kΩ, the input terminal exhibits an equivalent zero internal resistance, without changing the voltage distribution of the circuit under test; the weak voltage signal is amplified to the detectable range of the ADC by using the amplifier gain G, thereby improving the measurement sensitivity and resolution; and the current measurement range can be extended to the mA level or even higher simply by adjusting the sampling resistor and amplifier gain according to different ranges.

[0057] This third embodiment provides a monitoring device, including the current measuring instrument provided in the second aspect.

[0058] The present invention also provides an application scenario in which the current measuring instrument of Embodiment 2 is applied to the current detection of medical electrocardiogram monitoring equipment.

[0059] In electrocardiogram (ECG) monitoring devices, the signal current acquired by electrode patches is typically in the extremely low range of nA to μA. In traditional current sampling methods, the presence of the sampling resistor 101 introduces a voltage drop between the patient and the device, which not only reduces measurement accuracy but may also potentially impact human safety. Therefore, in medical monitoring scenarios, the sampling circuit must possess extremely high accuracy and near-zero internal resistance.

[0060] In this embodiment, the current measuring instrument provided in Embodiment 2 is used: the sampling resistor 101 is selected as 10 kΩ so that a measurable voltage signal can be generated even under nA-level current; the first operational amplifier 103 makes the potential difference across the sampling resistor close to zero, thereby ensuring that the equivalent input internal resistance of the circuit is zero and avoiding voltage loss in the loop introduced by the sampling resistor; the second operational amplifier 104 acts as a voltage follower to isolate and buffer weak current signals and ensure stable signal transmission; the amplifier further amplifies the voltage signal to ensure that the output voltage falls within the optimal sampling range of the analog-to-digital converter (ADC).

[0061] For example, when the input current I input When the current is 100 nA, the sampling voltage is only 1 mV under the condition of R = 10 kΩ. After amplification by amplifier G = 100, the output voltage is 100 mV, which can be stably acquired and processed by the ADC, thus ensuring the integrity and accuracy of the ECG signal.

[0062] The technical advantages of this implementation are: ensuring that no additional voltage loss is introduced during the human body signal acquisition process, thus improving safety; maintaining high-precision sampling within the current range of nA to μA; avoiding distortion of weak signals during transmission through operational amplifier buffering and isolation; and ensuring that the medical electrocardiogram monitoring equipment maintains stable and reliable current detection capability during long-term operation.

[0063] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. A current sampling circuit, characterized in that, include: Sampling resistor; An amplifier, wherein its first input terminal is connected to the first terminal of the sampling resistor, and the second input terminal of the amplifier is connected to the second terminal of the sampling resistor; A first operational amplifier, wherein the inverting input terminal of the first operational amplifier and the first terminal of the sampling resistor are connected together as the negative input terminal of the current sampling circuit, and the output terminal of the first operational amplifier is connected to the second terminal of the sampling resistor; The second operational amplifier has its non-inverting input connected to the non-inverting input of the first operational amplifier, and its inverting input and output are connected together as the positive input of the current sampling circuit.

2. The current sampling circuit as described in claim 1, characterized in that, The first operational amplifier adjusts the potential difference across the sampling resistor to make the equivalent input resistance of the current sampling circuit zero.

3. The current sampling circuit as described in claim 1, characterized in that, The inverting input terminal and the output terminal of the second operational amplifier receive the input current signal to isolate and buffer the input current signal.

4. The current sampling circuit as described in claim 1, characterized in that, The amplifier is an instrumentation amplifier used to differentially amplify the voltage formed by the sampling resistor.

5. The current sampling circuit as described in claim 1, characterized in that, The output voltage U of the current sampling circuit output Satisfy the following formula: IN output =I INTPUT ×RS×G; Among them, I INTPUT is the input current, RS is the resistance of the sampling resistor, and G is the amplifier gain.

6. The current sampling circuit as described in claim 1, characterized in that, The current sampling circuit further includes a temperature detection module and a gain correction module. The temperature detection module is arranged adjacent to the sampling resistor. The output terminal of the temperature detection module is connected to the input terminal of the gain correction module, and the output terminal of the gain correction module is connected to the control terminal of the amplifier.

7. The current sampling circuit as described in claim 6, characterized in that, The amplifier is a gain-adjustable amplifier.

8. A current measuring instrument, characterized in that, Includes the current sampling circuit as described in any one of claims 1 to 7.

9. The current measuring instrument as described in claim 8, characterized in that, The current measuring instrument further includes a signal processing module, a display module, and a power supply module. The input terminal of the signal processing module is connected to the output terminal of the amplifier, and the output terminal of the signal processing module is connected to the input terminal of the display module. The power supply module is connected to the amplifier, the first operational amplifier, the second operational amplifier, the signal processing module, and the display module.

10. A monitoring device, characterized in that, Includes the current measuring instrument as described in claim 8 or 9.

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