Micro-current acquisition system

Abstract

The invention discloses a micro-current acquisition system, which comprises an I / V conversion circuit and a signal processing circuit, and is characterized in that the I / V conversion circuit is used for converting a to-be-detected micro-current signal into a voltage signal, and the signal processing circuit is used for amplifying and filtering the voltage signal; the micro-current acquisition system further comprises an A / D converter which is used for converting an analog voltage signal obtained after processing of the signal processing circuit into a digital signal.

Description

Technical Field

[0001] The invention relates to the field of electrical signal detection, and in particular to a micro-current acquisition system. Background Art

[0002] Current detection, especially micro-current detection, has always been a difficult point in the detection field. The main problems are: 1. Complex structure: In order to achieve range switching, the existing technology usually needs to use multiple analog switches and multiplexers and other components, resulting in a complex circuit structure. 2. Slow response speed: Due to the complexity of the circuit structure, the response speed of the existing technology is relatively slow and cannot meet the needs of fast dynamic measurement. 3. Low stability: Due to the large number of components and the complexity of the circuit, the stability of the existing technology is limited. 4. Low accuracy: Due to the limitations of circuits and components, the measurement accuracy of the existing technology is limited and may not meet the needs of high-precision measurement. Summary of the invention

[0003] To this end, the present invention proposes a micro-current collection system that can solve at least one or more of the above problems.

[0004] In order to achieve the purpose of the present invention, the following technical solutions are adopted:

[0005] A microcurrent acquisition system includes an I / V conversion circuit and a signal processing circuit, wherein: the I / V conversion circuit is used to convert the microcurrent signal to be detected into a voltage signal, and the signal processing circuit is used to amplify and filter the above voltage signal; the microcurrent acquisition system also includes an A / D converter, which is used to convert the analog voltage signal obtained after processing by the signal processing circuit into a digital signal.

[0006] The microcurrent acquisition system, wherein: the I / V conversion circuit includes a sampling module and an operation unit; the sampling module includes multiple sampling units connected in parallel, and the sampling units are used to sample microcurrents of different sizes; the operation unit includes an operational amplifier, and the operation unit is used to convert the current signal sampled by the sampling unit into a voltage signal.

[0007] The micro-current collection system, wherein: the signal processing circuit includes a first filtering circuit, an amplifying circuit, and a second filtering circuit; the input end of the first filtering circuit is connected to the output end of the I / V conversion circuit, the output end of the first filtering circuit is connected to the input end of the amplifying circuit, the output end of the amplifying circuit is connected to the input end of the second filtering circuit, and the output end of the second filtering circuit is connected to the input end of the A / D converter.

[0008] The micro-current collection system, wherein: the sampling unit includes a small current sampling unit and a large current sampling unit.

[0009] The micro-current acquisition system includes a plurality of small current sampling units, each of which is used to acquire current signals of different current ranges.

[0010] The micro-current collection system, wherein: the large current sampling unit includes a relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the circuit structure of the micro-current collection system. DETAILED DESCRIPTION

[0012] The following is combined with Figure 1 , the specific implementation modes of the present invention are described in detail. The implementation modes are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention. Obviously, the embodiments described in the present invention are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0013] "One embodiment" or "some embodiments" described in this specification means that one or more embodiments of the present invention include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, in this specification, the terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0014] like Figure 1 As shown, the microcurrent acquisition system includes an I / V conversion circuit and a signal processing circuit. The I / V conversion circuit is used to convert the microcurrent signal to be detected into a voltage signal, and the signal processing circuit is used to amplify, filter, and process the voltage signal. The microcurrent acquisition system of the present invention also includes an A / D converter, which is used to convert the analog voltage signal obtained after processing by the signal processing circuit into a digital signal.

[0015] The I / V conversion circuit includes a sampling module and an operation unit; the sampling module includes multiple sampling units connected in parallel, and the sampling units are used to sample microcurrents of different sizes; the operation unit includes an operational amplifier U1, which can be ADA4530 or ADA4530 series, and the operation unit is used to convert the current signal sampled by the sampling unit into a voltage signal.

[0016] The sampling unit includes three small current sampling units and one large current sampling unit. The three small current sampling units have the same circuit structure. The first small current sampling unit circuit, the second small current sampling unit circuit, and the third small current sampling unit circuit all include analog switch chips.

[0017] Next, taking the first small current sampling unit as an example, the circuit structure of the small current sampling unit will be described.

[0018] The first small current sampling unit includes the first analog switch chip U3B (such as ADG441BRZ), the first sampling resistor R6 (10K ohms), and the first filter capacitor C7 (47nF). Pins 1 and 8 of the first analog switch U3B are used to receive the first small current sampling control signal (i.e., connected to the input terminal marked with 100uA in Figure 1 . The sampling (measurement) current I of the first analog switch U3B in ranges from 0 < i ≤ 100uA. Pins 2 and 7 of the first analog switch U3B are grounded; pins 3 and 6 of the first analog switch U3B are connected to the first end of the first sampling resistor R6, the second end of the first sampling resistor R6 is connected to the non-inverting input terminal (pin 1) of the operational amplifier U1, and both ends of the first filter capacitor C7 are connected to both ends of the first sampling resistor R6.

[0019] The second small current sampling unit includes the second analog switch chip U3C (such as ADG441BRZ), the second sampling resistor R7, and the second filter capacitor C8. Pins 9 and 16 of the second analog switch U3C are used to receive the second small current sampling control signal (i.e., connected to the input terminal marked with 1mA in Figure 1 . Pins 10 and 15 of the second analog switch U3C are grounded; pins 11 and 14 of the second analog switch U3C are connected to the first end of the second sampling resistor R7, the second end of the second sampling resistor R7 is connected to the non-inverting input terminal (pin 1) of the operational amplifier U1, and both ends of the second filter capacitor C8 are connected to both ends of the second sampling resistor R7. The sampling (measurement) current I of the second small current sampling unit in ranges from 100uA < i ≤ 1mA. The resistance value of the second sampling resistor R7 is 1K ohm, and the capacitance value of the second filter capacitor C8 is 470nF.

[0020] The third small current sampling unit includes the third analog switch chip U4B (such as ADG441BRZ), the third sampling resistor R8, and the third filter capacitor C9. Pins 1 and 8 of the third analog switch U4B are used to receive the third small current sampling control signal (i.e., connected to the input terminal marked with 10mA in Figure 1 . Pins 2 and 7 of the third analog switch U4B are grounded; pins 3 and 6 of the third analog switch U4B are connected to the first end of the third sampling resistor R8, the second end of the third sampling resistor R8 is connected to the non-inverting input terminal (pin 1) of the operational amplifier U1, and both ends of the third filter capacitor C9 are connected to both ends of the third sampling resistor R8. The sampling (measurement) current I of the third small current sampling unit in ranges from 1mA < i ≤ 10mA. The resistance value of the third sampling resistor R8 is 100 ohms, and the capacitance value of the third filter capacitor C9 is 4.7uF.

[0021] The large current sampling unit includes a relay (for example, G5V-2-DC3), and the relay includes a switch unit and a control unit. The switch unit includes a first switch K1B and a second switch K1C. Pin 4 of the first switch K1B and pin 13 of the second switch K1C are connected to the first end of the fourth sampling resistor R4 (20 ohms) and the first end of the fifth sampling resistor R5 (20 ohms), and the second end of the fourth sampling resistor R4 and the second end of the fifth sampling resistor R5 are connected to the non-inverting input end of the operational amplifier U1; the two ends of the fourth filter capacitor C10 (100 pF) are respectively connected to the two ends of the fourth sampling resistor R4 and the fifth sampling resistor R5; pin 8 of the first switch K1B and pin 9 of the second switch K1C are grounded; pin 6 of the first switch K1B and pin 11 of the second switch K1C are suspended. The above-mentioned manner of connecting the fourth sampling resistor R4 and the fifth sampling resistor R5 in parallel can reduce the power consumption of each resistor, and the sampling resistor will not produce resistance changes due to overheating, so that the sampling is more accurate.

[0022] The control unit includes a coil K1A and a voltage-stabilizing transistor Q1 (for example, FMMT691). The base of the voltage-stabilizing transistor Q1 is connected to the second end of a resistor R16 (1K ohm), the first end of the resistor R16 is connected to the positive end of a diode D1, and the negative end of the diode D1 is connected to a large current sampling control signal (i.e., connected to the positive end of a diode D1). Figure 1 A resistor R15 (10K ohm) is connected between the base and emitter of the voltage-stabilizing transistor Q1, the emitter is connected to a +3V voltage source, the collector is connected to the negative terminal of the diode D2, and the positive terminal of D2 is grounded; the pin 1 of the coil K1A is connected to the negative terminal of the diode D2, and the pin 16 of the diode K1A is connected to the positive terminal of D2.

[0023] The operation unit includes a first operational amplifier U1. Different from the conventional sampling circuit which uses the inverting input terminal of the first operational amplifier U1 as the sampling terminal, the present invention adopts a circuit design which uses the non-inverting input terminal of the operational amplifier U1 as the signal sampling terminal, thereby making it less likely for the operational amplifier U1 to self-oscillate and making the output of the operational amplifier more stable.

[0024] The positive input terminal (pin 1) of the first operational amplifier U1 is connected to the negative terminal of the clamping diode ZD1, and the positive terminal of the clamping diode ZD1 is grounded. The function of the clamping diode ZD1 is to protect the first operational amplifier U1 and prevent the chip from being burned due to excessive input voltage.

[0025] The first resistor R1 (1K ohm) and the first capacitor C1 (15pF) are respectively connected between the inverting input terminal (pin 8) and the output terminal (pin 6) of the first operational amplifier U1, which are used for phase compensation of the operational amplifier to ensure that the operational amplifier operates in a stable state and does not generate self-oscillation; the positive power supply terminal (pin 5) of the operational amplifier U1 is connected to a +7V voltage source; the negative power supply terminal (pin 4) of the operational amplifier is connected to a -7V voltage source; the positive power supply terminal (pin 5) is grounded through a capacitor C2 (0.1uf); the negative power supply terminal (pin 4) is grounded through a capacitor C11 (0.1uf); pin 7 is grounded; pins 2 and 3 are floating.

[0026] The signal processing circuit includes a first filter circuit, an amplifier circuit, and a second filter circuit, which are used to filter and amplify the voltage signal output from the output end (pin 6) of the operational amplifier U1. The input end of the first filter circuit is connected to the output end of the I / V conversion circuit, the output end of the first filter circuit is connected to the input end of the amplifier circuit, the output end of the amplifier circuit is connected to the input end of the second filter circuit, and the output end of the second filter circuit is connected to the input end of the A / D converter.

[0027] The first filtering circuit includes a second operational amplifier U2 (for example, OPA186IDR), the non-inverting input terminal of the second operational amplifier U2 is connected to the second terminal of the third resistor R3 (3.3K ohms), the first terminal of the third resistor is connected to the second terminal of the second resistor R2 (3.3K ohms), the second terminal of the third resistor R3 is grounded through a capacitor C5 (0.22uF); the first terminal of the second resistor R2 is connected to the output terminal (pin 6) of the operational amplifier U1; the second terminal of the second resistor R2 is connected to the first terminal of the fourth capacitor C4 (0.68uF), and ...). The second end of capacitor C4 is connected to the inverting input end of the second operational amplifier U2; the inverting input end of the second operational amplifier U2 is connected to the output end (pin 6) of the second operational amplifier U2; the positive power supply end (pin 7) of the second operational amplifier U2 is connected to the +12V voltage source; the negative power supply end (pin 4) of the second operational amplifier U2 is connected to the -12V voltage source; the positive power supply end (pin 7) is grounded through capacitor C6 (0.1uf); the negative power supply end (pin 4) is grounded through capacitor C3 (0.1uf); pins 1, 5, and 8 are floating. The output end of the first filter circuit is the output end (pin 6) of the second operational amplifier U2.

[0028] The amplifier circuit includes a third operational amplifier U5 (for example, OPA186IDR), the output end (pin 6) of the second operational amplifier U2 is connected to the non-inverting input end (pin 3) of the third operational amplifier U5, and the non-inverting input end (pin 3) of the third operational amplifier U5 is grounded through a resistor R14 (1K ohm); the inverting input end (pin 2) of the third operational amplifier U5 is connected to the second end of a resistor R10 (1K ohm), and the first end of the resistor R10 is grounded; resistors R9 (10K ohm) and R10 (10K ohm) are connected between the inverting input end (pin 2) and the output end (pin 6) of the third operational amplifier U5, respectively. The first and second ends of capacitor C12 (15pF), R9 and R10 form an 11-fold inverse proportional amplifier. Capacitor C12 is used for phase compensation of the operational amplifier to ensure that the operational amplifier works in a stable state and does not generate self-oscillation; the positive power supply terminal (pin 7) of the third operational amplifier U5 is connected to a +12V voltage source; the negative power supply terminal (pin 4) of the third operational amplifier is connected to a -12V voltage source; the positive power supply terminal (pin 7) is grounded through capacitor C3 (0.1uF); the negative power supply terminal (pin 4) is grounded through capacitor C18 (0.1uF); pins 1, 5, and 8 are floating. The output end of the amplifier circuit is the output end (pin 6) of the third operational amplifier U5.

[0029] The second filtering circuit includes a fourth operational amplifier U6 (for example, OPA186IDR), the non-inverting input terminal of the fourth operational amplifier U6 is connected to the second end of a resistor R12 (3.3K ohms), the first end of the resistor R12 is connected to the second end of a resistor R11 (3.3K ohms), the first end of the resistor R11 is connected to the output end (pin 6) of the third operational amplifier U5; the second end of the resistor R12 is grounded through a capacitor C16 (0.22uF); the second end of the resistor R11 is connected to the first end of a capacitor C15 (0.68uF), and the capacitor C15 The second end is connected to the inverting input end (pin 2) of the fourth operational amplifier U6; the inverting input end of the fourth operational amplifier U6 is connected to the output end (pin 6) of the fourth operational amplifier U6; the positive power supply end (pin 7) of the fourth operational amplifier U6 is connected to the +12V voltage source; the negative power supply end (pin 4) of the fourth operational amplifier U6 is connected to the -12V voltage source; the positive power supply end (pin 7) is grounded through capacitor C17 (0.1uf); the negative power supply end (pin 4) is grounded through capacitor C4 (0.1uF); pins 1, 5, and 8 are floating. The output end of the second filter circuit is the output end (pin 6) of the third amplifier U6.

[0030] The output end (pin 6) of the third amplifier U6 is connected to the first end of the zero resistor R13, the second end of the zero resistor R13 is connected to the input end of the A / D converter (eg AD7608), and the output end of the A / D converter outputs the digital voltage signal VOUT after analog-to-digital conversion.

[0031] The output of the A / D converter is connected to a controller (not shown in the figure), which is used to calculate the current signal I to be measured based on the received voltage signal VOUT. in The current value is calculated by the prior art, for example, by dividing VOUT by the amplification ratio of the signal processing circuit and the sampling resistor value of the I / V conversion circuit to obtain the current value of the current to be measured, and according to the current value, it is determined whether to switch the multi-channel parallel sampling units of the I / V conversion circuit to obtain the most accurate current measurement value. The switching method is to output a corresponding small current sampling control signal or a large current sampling control signal to the corresponding sampling unit to turn on the corresponding sampling unit.

[0032] The working process of the micro-current collection system of this patent is described below. The working process is as follows:

[0033] Current to be measured I in The current to be measured I in After the input, a sampling voltage will be formed on the sampling resistor of the sampling unit. The sampling voltage is input to the non-inverting input terminal of the first operational amplifier of the operation unit. The first operational amplifier acts as a follower, and its output terminal outputs an output voltage of the same magnitude as the sampling voltage. The output voltage is received by the A / D converter after primary filtering, amplification, and secondary filtering. The A / D converter converts the received analog voltage signal into a digital signal and sends it to the controller. The controller calculates the current to be measured I in The current value is obtained and compared with the measurement range of the sampling unit. If the current value is too close to the minimum or maximum measurement value of the sampling unit (for example, the difference between the two is less than 5%), the next or previous sampling module is switched to measure again to obtain an accurate measurement value.

[0034] In the present invention, when the measured current I in When the current flows through the I / V conversion circuit, the circuit intelligently selects the optimal sampling unit according to the preset current acquisition control signal, realizes the accurate conversion from current to voltage, and generates the corresponding voltage signal;

[0035] This voltage signal first enters the professionally designed signal processing circuit, which uses high-efficiency filtering technology to initially suppress and remove the noise on the voltage signal to improve the purity of the signal;

[0036] To further enhance the resolution and accuracy of the signal, the voltage signal after preliminary filtering is sent to the in-phase proportional amplifier circuit. This circuit linearly amplifies the voltage signal by precisely controlling the amplification factor, ensuring that the amplitude of the signal is significantly increased while maintaining the signal waveform without distortion, which is convenient for subsequent processing;

[0037] The amplified voltage signal enters the signal processing circuit again for secondary filtering to further filter out residual noise and interference, and finally outputs a high-quality, high signal-to-noise ratio voltage signal to meet the needs of high-precision measurement and analysis.

[0038] Through the present invention, it is possible to accurately capture tiny current changes in the range of 0 to 50mA. By integrating advanced acquisition control strategies, the system can intelligently adjust the input current to its optimal measurement range, thereby ensuring the accuracy and dynamic response capability of the measurement results. In order to further improve the signal quality and system performance, the system introduces a signal processing circuit, which effectively improves the signal-to-noise ratio of the signal, that is, it filters out noise interference through a second-order filter and enhances the signal purity. In addition, each operational amplifier is integrated with a phase compensation link to ensure the output stability of the operational amplifier. The current input operational amplifier is integrated with a protection circuit to prevent the operational amplifier from being burned due to excessive input voltage.

[0039] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A micro-current acquisition system, comprising an I / V conversion circuit and a signal processing circuit, characterized in that: The I / V conversion circuit is used to convert the microcurrent signal to be detected into a voltage signal, and the signal processing circuit is used to amplify and filter the above voltage signal; the microcurrent acquisition system also includes an A / D converter, which is used to convert the analog voltage signal obtained after processing by the signal processing circuit into a digital signal.

2. The microcurrent collection system according to claim 1, characterized in that: The I / V conversion circuit includes a sampling module and an operation unit; the sampling module includes multiple sampling units connected in parallel, and the sampling units are used to sample microcurrents of different sizes; the operation unit includes an operational amplifier, and the operation unit is used to convert the current signal sampled by the sampling unit into a voltage signal.

3. The micro-current collection system according to claim 1, characterized in that: The signal processing circuit includes a first filtering circuit, an amplifying circuit, and a second filtering circuit; the input end of the first filtering circuit is connected to the output end of the I / V conversion circuit, the output end of the first filtering circuit is connected to the input end of the amplifying circuit, the output end of the amplifying circuit is connected to the input end of the second filtering circuit, and the output end of the second filtering circuit is connected to the input end of the A / D converter.

4. The microcurrent collection system according to claim 2, characterized in that: The sampling unit includes a small current sampling unit and a large current sampling unit.

5. The micro-current collection system according to claim 4, characterized in that: There are multiple small current sampling units, which are respectively used to collect current signals with different current ranges.

6. The micro-current collection system according to claim 4, characterized in that: The high current sampling unit includes a relay.

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