An adaptive threshold microampere current sampling network structure and a control method thereof

Abstract

This invention relates to the field of weak current detection technology. Microcurrent detection technology is susceptible to circuit noise, environmental interference, and switching delays. Current range switching relies on software processes, which carries risks of sampling delay, judgment lag, and program crashes. This invention provides an adaptive threshold microampere-level current sampling network structure and its control method. Several parallel voltage acquisition and amplification branches are connected to the microcurrent to be measured. Range switching is achieved using logic processing control circuits and switching units. A closed-loop feedback control circuit is formed through latches and NOT gates to avoid logic oscillations during switching, improving the stability of the detection process. Optical coupler control ensures that only one voltage acquisition and amplification branch is allowed to conduct at any given time. The high isolation characteristics of the optocoupler effectively suppress leakage current in microcurrent measurement and avoid mutual interference between resistors of different branches, significantly reducing thermal noise in the sampling circuit and improving sampling accuracy and signal-to-noise ratio.

Description

Technical Field

[0001] This invention relates to the field of weak current detection technology, and more specifically, to a microampere-level current sampling network structure with adaptive threshold and its control method. Background Technology

[0002] Microcurrent detection technology plays a crucial role in high-precision scientific research and industrial fields such as photoelectric detection and biosensing. This type of measurement is susceptible to factors such as circuit noise, environmental interference, and switching delays, placing extremely high demands on the sensitivity, dynamic range, and response speed of the sampling network.

[0003] Traditional microcurrent detection uses a resistor with a fixed resistance value as the sampling network. For example, Chinese patent (CN212675023U title: A DC microcurrent detection circuit) uses an operational amplifier structure with a fixed feedback resistor. Although it can measure microcurrents with high accuracy within a specific range, it is difficult to cope with current signals that vary over a wide range, and the detection range is limited.

[0004] To improve dynamic range, existing technologies have introduced multi-range switching mechanisms, such as the Chinese patent (CN119936460A: A Microcurrent Detection System). The clamping current sampling unit includes a sampling resistor, a Zener diode, and a MOSFET, which adaptively samples the microcurrent. However, the Zener diode in the clamping current sampling unit has inherent on-resistance and leakage current, which introduces significant errors in microampere-level current measurements, especially under high and low temperature environments where performance deteriorates further. Furthermore, the Chinese patent (CN202310966602.1: Circuit Structure and Microcurrent Meter for Extending the DC Microcurrent Measurement Range) uses a relay-based range switching scheme. While this reduces on-resistance, the mechanical structure suffers from short lifespan, slow switching speed (typically milliseconds), and susceptibility to contact sparks and electromagnetic interference, making it unsuitable for high-speed or high-reliability applications.

[0005] To improve automation, numerous range control strategies based on microcontrollers (MCUs) have emerged in recent years. Chinese patent application (CN116908529A, title: Micro-current Detection Device) uses an MCU to select a suitable resistor as a sampling circuit to convert a micro-current signal into a voltage signal. Then, an instrument operational amplifier circuit amplifies the voltage signal to a suitable amplitude, which is then read and processed by the microprocessor. While this method expands the range of micro-current detection, range switching relies on software processes, which carries risks such as sampling delay, judgment lag, and program crashes. Furthermore, it suffers from insufficient reliability in complex electromagnetic environments or applications with high real-time requirements. In addition, the introduction of the MCU increases system power consumption and cost. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an adaptive threshold microampere-level current sampling network structure and its control method. This invention achieves rapid adaptive range switching based on hardware, realizes fast response at the hardware level without an MCU, avoids logic oscillation during switching, and improves the stability of the detection process.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] An adaptive threshold microampere-level current sampling network structure includes several parallel voltage acquisition and amplification branches. The input terminals of all voltage acquisition and amplification branches are connected to the microcurrent to be measured. Each voltage acquisition and amplification branch is equipped with a logic processing control circuit and a switching unit. The logic processing control circuit compares and determines whether the output voltage of the current voltage acquisition and amplification branch is within a preset voltage range consisting of a preset upper limit voltage and a preset lower limit voltage. Based on the determination result, it outputs an enable control signal to the switching unit to control the optocoupler of the switching unit and to control the selection state of the current voltage acquisition and amplification branch. The switching unit has two signal control input terminals. The first signal control input terminal of the switching unit is connected to the signal output terminal of the voltage acquisition and amplification branch it is in, and the second signal control input terminal is connected to the signal output terminal of the logic processing control unit of the adjacent voltage acquisition and amplification branch.

[0009] Furthermore, the voltage acquisition and amplification branch includes a sampling resistor Ri and an instrumentation amplifier Gi, which converts the input micro-current into a voltage signal and amplifies it. The output of the instrumentation amplifier Gi is the amplified voltage Ui to be measured, where i represents the serial number of the voltage acquisition and amplification branch.

[0010] Furthermore, the number of voltage acquisition and amplification branches shall not be less than 3, and the sampling resistor Ri shall have a value range of 100Ω~10kΩ.

[0011] Furthermore, the gain calculation formula for the instrumentation amplifier Gi is GI = 1 + (100kΩ / Rgi), where Rgi represents the gain resistor of the instrumentation amplifier Gi. The current measurement range in the voltage acquisition amplification branch is controlled by the gain resistor Rgi and the sampling resistor Ri of the instrumentation amplifier. The gain adjustment range of the instrumentation amplifier Gi is 1~1000. The measurement range of the voltage acquisition amplification branch is determined by the resistance value of the sampling resistor Ri and the gain GI of the instrumentation amplifier Gi. The calculation formulas for the upper limit and lower limit of current measurement in the voltage acquisition amplification branch are as follows:

[0012] Ii_high= 10 6

[0013] Ii_low= 10 6

[0014] The units for the upper limit of current measurement Ii_high and the lower limit of current measurement Ii_low are μA, and the preset relationship between the upper limit voltage Vi_high and the lower limit voltage Vi_low is Vi_high = 10. In Vi_low, i in both Vi and Ii represents the serial number of the voltage acquisition and amplification branch.

[0015] Furthermore, the logic processing control circuit includes an upper limit circuit and a lower limit circuit for limiting the preset voltage range of the current voltage acquisition and amplification branch. The upper limit circuit includes a comparator UH, a latch DH, and a NOT gate EH. The input of the comparator UH is connected to the signal output of the voltage acquisition and amplification branch and the preset upper limit voltage of the current voltage acquisition and amplification branch, respectively. The output of the comparator UH is connected to the input of the latch DH, the output of the latch DH is connected to the input of the NOT gate EH, and the output of the NOT gate EH is connected to the enable terminal of the latch DH. Simultaneously, the output of the NOT gate EH serves as the output of the upper limit circuit of the logic processing control circuit and is connected to the switching unit. The lower limit circuit includes a comparator UL, a latch DL, and... The inputs of NOT gate EL and comparator UL are connected to the signal output of the voltage acquisition and amplification branch and the preset lower limit voltage of the current voltage acquisition and amplification branch, respectively. The output of comparator UL is connected to the input of latch DL, the output of latch DL is connected to the input of NOT gate EL, and the output of NOT gate EL is connected to the enable terminal of latch DL. At the same time, the output of NOT gate EL is connected to the switching unit as the output of the lower limit circuit of the logic processing control circuit. Comparators UH and UL compare the output voltage to be measured of the current voltage acquisition and amplification branch with the preset voltage range and output the results. The latch latches the output of the comparators and uses the output of the NOT gate as the output signal of the logic processing control circuit.

[0016] Furthermore, it also includes a power supply circuit that provides positive and negative dual power supplies and a reference voltage for the voltage acquisition and amplification branch, the logic processing and control circuit, and the switching unit.

[0017] An adaptive threshold microampere-level current sampling network control method is disclosed. Based on the aforementioned adaptive threshold microampere-level current sampling network structure, the microcurrent to be measured is converted into several voltages to be measured by several voltage acquisition and amplification branches through the microampere-level current sampling network structure. The logic processing control circuit compares the preset voltage range of the current voltage acquisition and amplification branch with the voltage to be measured, and controls the optocoupler of the switching unit to complete the selection of the voltage acquisition and amplification branch, thereby realizing adaptive current sampling control. The method specifically includes the following steps:

[0018] Step 1. The microcurrent I to be measured flows into the microampere-level current sampling network structure, and voltage drops Vi are generated across the sampling resistors Ri on each voltage acquisition and amplification branch. After the voltage drops Vi are amplified by the instrumentation amplifier Gi according to a preset gain, the output voltage Voi is the output voltage of the current voltage acquisition and amplification branch;

[0019] Step 2. The logic processing and control circuit compares the output voltages Voi of all voltage acquisition and amplification branches obtained in Step 1 with the preset voltage ranges of the corresponding voltage acquisition and amplification branches. If the output voltage is within the preset voltage range, the logic processing and control circuit of the current voltage acquisition and amplification branch outputs a low level, and the optocoupler in the switch unit conducts; otherwise, the optocoupler is in the off state for range switching. The voltage acquisition and amplification branch where the optocoupler conducts is the current active branch;

[0020] Step 3. Except for the current active branch, the output terminals of the NOT gates in the logic processing and control circuits of other voltage acquisition and amplification branches output an enable signal E to the latch, and the latch enters the latch and hold state to shield the range switching request signals of adjacent voltage acquisition and amplification branches before the next measurement, eliminate the oscillation phenomenon generated at the critical point of the current measurement range, and achieve range self-adaptive switching current detection of the hardware circuit.

[0021] Furthermore, the optocoupler of the switch unit controls the on and off of the voltage acquisition and amplification branches, and only one voltage acquisition and amplification branch conducts at any detection and sampling moment.

[0022] Furthermore, in Step 2, the range switching operation is as follows:

[0023] If the output voltage Voi is higher than the upper limit voltage Vi_high of the upper limit circuit, i.e., Voi > Vi_high, the comparator UH of the current voltage acquisition and amplification branch outputs a high level, and the comparator UL outputs a low level. At this time, the switch is made to a voltage acquisition and amplification branch with a measurement range larger than that of the current voltage acquisition and amplification branch;

[0024] If the output voltage Voi is lower than the lower limit voltage Vi_low of the lower limit circuit, i.e., Voi < Vi_low, the comparator UL of the current voltage acquisition and amplification branch outputs a high level, and the comparator UH outputs a low level. At this time, the switch is made to a voltage acquisition and amplification branch with a measurement range smaller than that of the current voltage acquisition and amplification branch;

[0025] After the range switching is completed, the output signals of the comparators UL and UH of the current voltage acquisition and amplification branch are latched in state by the latch. When the enable signal E at the enable terminal of the latch connected to the output terminal of the NOT gate is in the effective state, the logic state is latched to the output terminal Q of the latch. When the enable signal E is invalid, the original output state remains unchanged.

[0026] In summary, the invention has the following beneficial effects:

[0027] This invention provides a hardware-based, fast adaptive range switching system for micro-current detection. Utilizing an optocoupler combination of dual comparators and a switching unit, it achieves rapid response without an MCU. The micro-current is converted into a detectable voltage signal by a sampling resistor. After being processed by a logic control circuit and judged by the switching unit, the range is switched. A closed-loop feedback control circuit using latches and NOT gates prevents logic oscillations during switching, improving the stability of the detection process. The optocoupler in the switching unit controls the on / off state of each voltage acquisition and amplification branch, allowing only one branch to conduct at any given time. The high isolation of the optocoupler effectively suppresses leakage current in micro-current measurement and avoids mutual interference between resistors in different voltage acquisition and amplification branches. By selecting low-resistance sampling resistors and appropriately configuring the gain resistor parameters of the instrumentation amplifier, thermal noise in the sampling circuit is significantly reduced, making its impact on microampere-level current measurement negligible, thus improving sampling accuracy and signal-to-noise ratio. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the microampere-level current sampling network structure of the present invention;

[0029] Figure 2 This is the circuit diagram of the voltage acquisition and amplification branch of the present invention;

[0030] Figure 3 For upper and lower limit circuits in logic processing control circuits;

[0031] Figure 4 This is the circuit diagram of the switching unit. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings.

[0033] It should be noted that, for ease of description, the descriptions of direction in the following text are consistent with the directions in the accompanying drawings, but do not limit the structure of the present invention.

[0034] like Figures 1-4As shown, this invention discloses an adaptive threshold microampere-level current sampling network structure, including several parallel voltage acquisition and amplification branches. The input terminals of all voltage acquisition and amplification branches are connected to the microcurrent to be measured. A logic processing control circuit and a switching unit are set on each voltage acquisition and amplification branch. The logic processing control circuit compares and determines whether the output voltage of the current voltage acquisition and amplification branch is within a preset voltage range consisting of a preset upper limit voltage and a preset lower limit voltage. Based on the determination result, it outputs an enable control signal to the switching unit to control the optocoupler of the switching unit and to control the selection state of the current voltage acquisition and amplification branch. The switching unit has two signal control input terminals. The first signal control input terminal of the switching unit is connected to the signal output terminal of the voltage acquisition and amplification branch it is in, and the second signal control input terminal is connected to the signal output terminal of the logic processing control unit of the adjacent voltage acquisition and amplification branch.

[0035] The voltage acquisition and amplification branch includes a sampling resistor Ri and an instrumentation amplifier Gi, which converts the input micro-current into a voltage signal and amplifies it. The output of the instrumentation amplifier Gi is the amplified voltage Ui to be measured, where i represents the sequence number of the voltage acquisition and amplification branch. The number of voltage acquisition and amplification branches shall not be less than 3, and the value of the sampling resistor Ri shall range from 100Ω to 10kΩ.

[0036] The gain of the instrumentation amplifier Gi is calculated using the formula GI = 1 + (100kΩ / Rgi), where Rgi represents the gain resistor of the instrumentation amplifier Gi. The value of the gain resistor Rgi determines the amplification factor of the instrumentation amplifier Gi.

[0037] The current measurement range of each voltage acquisition and amplification branch is controlled by the amplifier gain resistor Rgi and the sampling resistor Ri. The gain adjustment range of the instrumentation amplifier Gi is 1~1000. The measurement range of the voltage acquisition and amplification branch is determined by the resistance value of the sampling resistor Ri and the gain GI of the instrumentation amplifier Gi. The calculation formulas for the upper limit and lower limit of current measurement of the voltage acquisition and amplification branch are as follows:

[0038] Ii_high= 10 6

[0039] Ii_low= 10 6

[0040] The units for the upper limit Ii_high and lower limit Ii_low of current measurement are μA. The preset relationship between the upper limit voltage Vi_high and the lower limit voltage Vi_low is Vi_high = 10. In Vi_low, i in both Vi and Ii represents the serial number of the voltage acquisition and amplification branch. By selecting appropriate parameters and the number of voltage acquisition and amplification branches according to actual measurement requirements, accurate measurement of microcurrent values ​​within the measurement range can be achieved. This invention uses low-resistance sampling resistors and rationally configures the parameters of the gain resistors in the instrumentation amplifier, which can significantly reduce thermal noise in the sampling circuit, making its impact on microampere-level current measurement negligible, and improving sampling accuracy and signal-to-noise ratio.

[0041] The logic processing control circuit includes an upper limit circuit and a lower limit circuit for limiting the preset voltage range of the current voltage acquisition and amplification branch. The upper limit circuit includes a comparator UH, a latch DH, and a NOT gate EH. The input of the comparator UH is connected to the signal output of the voltage acquisition and amplification branch and the preset upper limit voltage of the current voltage acquisition and amplification branch, respectively. The output of the comparator UH is connected to the input of the latch DH, the output of the latch DH is connected to the input of the NOT gate EH, and the output of the NOT gate EH is connected to the enable terminal of the latch DH. Simultaneously, the output of the NOT gate EH serves as the logic gate's input. The output of the upper limit circuit of the processing control circuit is connected to the switching unit. The lower limit circuit includes a comparator UL, a latch DL, and a NOT gate EL. The input of comparator UL is connected to the signal output of the voltage acquisition and amplification branch and the preset lower limit voltage of the current voltage acquisition and amplification branch, respectively. The output of comparator UL is connected to the input of latch DL, the output of latch DL is connected to the input of NOT gate EL, and the output of NOT gate EL is connected to the enable terminal of latch DL. Simultaneously, the output of NOT gate EL serves as the output of the lower limit circuit of the logic processing control circuit and is connected to the switching unit. Comparators UH and UL compare the output voltage to be measured in the current voltage acquisition and amplification branch with the preset voltage range and output the results. The latch latches the comparator output and uses the output of the NOT gate as the output signal of the logic processing control circuit. The output of the NOT gate, which is the output of the logic processing control circuit, is connected to the enable terminal of the latch and the second signal control terminal of the adjacent voltage acquisition and amplification branch switching unit.

[0042] The present invention also includes a power supply circuit that provides positive and negative dual power supplies and a reference voltage for the voltage acquisition and amplification branch, the logic processing and control circuit, and the switching unit. The positive and negative dual power supplies and the reference voltage are adjusted according to the actual measurement requirements.

[0043] This invention also discloses an adaptive threshold microampere-level current sampling network control method. Based on the aforementioned adaptive threshold microampere-level current sampling network structure, the microcurrent to be measured passes through the microampere-level current sampling network structure. The voltage acquisition and amplification branch converts the microcurrent into a voltage to be measured. The logic processing control circuit compares the preset voltage range of the current voltage acquisition and amplification branch with the voltage to be measured, and controls the optocoupler of the switching unit to complete the selection of the voltage acquisition and amplification branch, thereby realizing adaptive current sampling control. Specifically, it includes the following steps:

[0044] Step 1. The micro-current I to be measured flows into the microampere-level current sampling network structure, and a voltage drop Vi is generated across the sampling resistor Ri on each voltage acquisition and amplification branch. After the voltage drop Vi is amplified by the instrumentation amplifier Gi according to a preset gain, the output voltage Voi is the voltage output by the current voltage acquisition and amplification branch; in the initial stage, the micro-current to be measured passes through the sampling resistors Ri of all voltage acquisition and amplification branches simultaneously. After passing through the sampling resistor Ri and the instrumentation amplifier Gi, the same current will generate different output voltages in each voltage acquisition and amplification branch.

[0045] Step 2. The logic processing control circuit is used to compare the voltages output by all voltage acquisition and amplification branches obtained in Step 1 with the preset voltage range of the corresponding voltage acquisition and amplification branch. If the output voltage is within the preset voltage range, the logic processing control circuit of the current voltage acquisition and amplification branch outputs a low level, and the optocoupler in the switch unit conducts; otherwise, the optocoupler is in the off state and range switching is performed; the voltage acquisition and amplification branch with the optocoupler conducting is the current active branch. After being judged by the logic processing control unit, at the same moment, only the optocoupler of one voltage acquisition and amplification branch conducts.

[0046] The range switching operation is as follows:

[0047] If the output voltage Voi is higher than the upper limit voltage of the upper limit circuit, that is, Voi > Vi_high, the comparator UH of the current voltage acquisition and amplification branch outputs a high level, and the comparator UL outputs a low level. At this time, the switch is made to a voltage acquisition and amplification branch with a measurement range larger than that of the current voltage acquisition and amplification branch;

[0048] If the output voltage Voi is lower than the lower limit voltage of the lower limit circuit, that is, Voi < Vi_low, the comparator UL of the current voltage acquisition and amplification branch outputs a high level, and the comparator UH outputs a low level. At this time, the switch is made to a voltage acquisition and amplification branch with a measurement range smaller than that of the current voltage acquisition and amplification branch;

[0049] After the range switching is completed, the output signals of the comparators UL and UH of the current voltage acquisition and amplification branch are latched in state by a latch. When the enable signal E of the latch is in the valid state, the logic state is latched to the output terminal Q. When the enable signal E is invalid, the original output state remains unchanged. The enable signal of the latch is controlled by a NOT gate from the output terminal of the latch.

[0050] Step 3. Except for the currently active branch, the output of the NOT gate in the logic processing control circuit of other voltage acquisition and amplification branches outputs an enable signal E to the latch. The latch enters a latching state to shield the range switching request signal from the adjacent voltage acquisition and amplification branch before the next measurement, eliminating oscillations at the critical point of the current measurement range and realizing adaptive range switching current detection in the hardware circuit. A closed-loop feedback control circuit is formed by the latch and NOT gate. The latch latches the comparator output and feeds it back to the latch enable terminal through the NOT gate output, thereby avoiding logic oscillations during range switching and improving the stability of the current detection process.

[0051] The optocoupler in the switching unit controls the on / off state of the voltage acquisition and amplification branch, ensuring that only one voltage acquisition and amplification branch is conducting at any given detection and sampling moment. The high isolation characteristic of the optocoupler effectively suppresses leakage current in micro-current measurements and avoids mutual interference between the resistors of different voltage acquisition and amplification branches.

[0052] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A microampere-level current sampling network structure with adaptive threshold, characterized in that: It includes several parallel voltage acquisition and amplification branches. The input terminals of all voltage acquisition and amplification branches are connected to the micro current to be measured. A logic processing and control circuit and a switching unit are set on each voltage acquisition and amplification branch. The logic processing and control circuit compares and determines whether the output voltage of the current voltage acquisition and amplification branch is within a preset voltage range consisting of a preset upper limit voltage and a preset lower limit voltage. Based on the determination result, it outputs an enable control signal to the switching unit to control the optocoupler of the switching unit and to control the selection state of the current voltage acquisition and amplification branch. The switching unit has two signal control input terminals. The first signal control input terminal of the switching unit is connected to the signal output terminal of the voltage acquisition and amplification branch where it is located, and the second signal control input terminal is connected to the signal output terminal of the logic processing control circuit of the adjacent voltage acquisition and amplification branch. The logic processing control circuit includes an upper limit circuit and a lower limit circuit for limiting the preset voltage range of the current voltage acquisition and amplification branch. The upper limit circuit includes a comparator UH, a latch DH, and a NOT gate EH. The input of the comparator UH is connected to the signal output of the voltage acquisition and amplification branch and the preset upper limit voltage of the current voltage acquisition and amplification branch, respectively. The output of the comparator UH is connected to the input of the latch DH, the output of the latch DH is connected to the input of the NOT gate EH, and the output of the NOT gate EH is connected to the enable terminal of the latch DH. Simultaneously, the output of the NOT gate EH serves as the output of the upper limit circuit of the logic processing control circuit and is connected to the switching unit. The lower limit circuit includes a comparator UL, a latch DL, and a NOT gate EH. The inputs of gate EL and comparator UL are respectively connected to the signal output of the voltage acquisition and amplification branch and the preset lower limit voltage of the current voltage acquisition and amplification branch. The output of comparator UL is connected to the input of latch DL. The output of latch DL is connected to the input of NOT gate EL. The output of NOT gate EL is connected to the enable terminal of latch DL. At the same time, the output of NOT gate EL is connected to the switching unit as the output of the lower limit circuit of the logic processing control circuit. Comparator UH and comparator UL compare the output voltage to be measured of the current voltage acquisition and amplification branch with the preset voltage range and output the result. The latch latches the output of the comparator and uses the output of the NOT gate as the output signal of the logic processing control circuit. By utilizing the optocoupler combination of dual comparators and switching units, a fast response without an MCU hardware level is achieved. The microcurrent is converted into a voltage signal that can be detected by the comparator through the sampling resistor. After being judged by the logic processing control circuit and the switching unit, the range switching is completed. A closed-loop feedback control circuit is formed by latches and NOT gates to avoid logic oscillation during the switching process and improve the stability of the detection process.

2. The microampere-level current sampling network structure with adaptive threshold according to claim 1, characterized in that: The voltage acquisition and amplification branch includes a sampling resistor Ri and an instrumentation amplifier Gi, which converts the input micro-current into a voltage signal and amplifies it. The output of the instrumentation amplifier Gi is the amplified voltage Ui to be measured, where i represents the serial number of the voltage acquisition and amplification branch.

3. The microampere-level current sampling network structure with adaptive threshold according to claim 2, characterized in that: The number of voltage acquisition and amplification branches shall not be less than 3, and the sampling resistor Ri shall be in the range of 100Ω~10kΩ.

4. The microampere-level current sampling network structure with adaptive threshold according to claim 2, characterized in that: The gain calculation formula for the instrumentation amplifier Gi is GI = 1 + (100kΩ / Rgi), where Rgi represents the gain resistor of the instrumentation amplifier Gi. The current measurement range in the voltage acquisition amplification branch is controlled by the amplifier gain resistor Rgi and the sampling resistor Ri. The gain adjustment range of the instrumentation amplifier Gi is 1~1000. The measurement range of the voltage acquisition amplification branch is determined by the resistance value of the sampling resistor Ri and the gain GI of the instrumentation amplifier Gi. The calculation formulas for the upper limit and lower limit of current measurement in the voltage acquisition amplification branch are as follows: Ii_high= 10 6 Ii_low= 10 6 The units for the upper limit of current measurement Ii_high and the lower limit of current measurement Ii_low are μA, and the preset relationship between the upper limit voltage Vi_high and the lower limit voltage Vi_low is Vi_high = 10. In Vi_low, i in both Vi and Ii represents the serial number of the voltage acquisition and amplification branch.

5. The microampere-level current sampling network structure with adaptive threshold according to claim 1, characterized in that: It also includes a power supply circuit that provides positive and negative dual power supplies and a reference voltage for the voltage acquisition and amplification branch, logic processing and control circuit, and switching unit.

6. A microampere-level current sampling network control method with adaptive threshold, based on the microampere-level current sampling network structure with adaptive threshold as described in any one of claims 1 to 5, characterized in that: The micro-current to be measured passes through a microampere-level current sampling network structure. Several voltage acquisition and amplification branches convert the micro-current into several voltages to be measured. The logic processing and control circuit compares the preset voltage range of the current voltage acquisition and amplification branch with the voltage to be measured, and controls the optocoupler of the switching unit to complete the selection of the voltage acquisition and amplification branch, realizing adaptive current sampling control. Specifically, it includes the following steps: Step 1. The micro current I to be measured flows into the microampere-level current sampling network structure. In each voltage acquisition and amplification branch, a voltage drop Vi is generated through the sampling resistor Ri. The voltage drop Vi is amplified by the instrumentation amplifier Gi according to the preset gain, and the output voltage Voi is the voltage output of the current voltage acquisition and amplification branch. Step 2. Use the logic processing control circuit to compare the output voltage of all voltage acquisition and amplification branches obtained in Step 1 with the preset voltage range of the voltage acquisition and amplification branch. If the output voltage is within the preset voltage range, the logic processing control circuit of the current voltage acquisition and amplification branch outputs a low level, and the optocoupler in the switching unit is turned on; otherwise, the optocoupler is turned off, and range switching is performed; the voltage acquisition and amplification branch with the optocoupler turned on is the currently active branch. Step 3. In addition to the currently active branch, the output of the NOT gate in the logic processing control circuit of other voltage acquisition and amplification branches outputs an enable signal E to the latch. The latch enters the latch holding state to shield the range switching request signal of the adjacent voltage acquisition and amplification branch before the next measurement, eliminate the oscillation phenomenon generated at the critical point of the current measurement range, and realize the range adaptive switching current detection of the hardware circuit.

7. The microampere-level current sampling network control method with adaptive threshold according to claim 6, characterized in that: The switching unit controls the on / off state of the optocoupler-controlled voltage acquisition and amplification branch, ensuring that only one voltage acquisition and amplification branch is active at any given detection and sampling time.

8. The microampere-level current sampling network control method with adaptive threshold according to claim 6, characterized in that: In step 2, the range switching operation is as follows: If the output voltage Voi is higher than the upper limit voltage Vi_high of the upper limit circuit (i.e., Voi>Vi_high), then the comparator UH of the current voltage acquisition and amplification branch outputs a high level, and the comparator UL outputs a low level. At this time, the circuit switches to a voltage acquisition and amplification branch that is larger than the measurement range of the current voltage acquisition and amplification branch. If the output voltage Voi is lower than the lower limit voltage Vi_low of the lower limit circuit, i.e., Voi < Vi_low, the comparator UL of the current voltage acquisition and amplification branch outputs a high level, and the comparator UH outputs a low level. At this time, a voltage acquisition and amplification branch with a voltage range smaller than the measurement range of the current voltage acquisition and amplification branch is switched; After the range switching is completed, the output signals of the comparators UL and UH of the current voltage acquisition and amplification branch are latched by a latch. When the enable signal E of the latch enable terminal connected to the output terminal of the NOT gate is in an effective state, the logical state is latched to the output terminal Q of the latch. When the enable signal E is invalid, the original output state remains unchanged.

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