Microampere-level current sampling network structure with self-adaptive threshold value and control method of microampere-level current sampling network structure

Abstract

The invention relates to the technical field of weak current detection, and aims to solve the problems that a micro-current detection technology is easily influenced by circuit noise, environmental interference and switching delay, the range switching of current depends on a software process, and the risks of sampling delay, judgment lag and program runaway exist; the invention provides a self-adaptive threshold microampere-level current sampling network structure and a control method thereof, a plurality of parallel voltage acquisition amplification branches are connected with a to-be-measured microcurrent, a logic processing control circuit and a switch unit are utilized to complete range switching, a closed-loop feedback control circuit is formed through a latch and a NOT gate, and the self-adaptive threshold microampere-level current sampling network structure is used for sampling the to-be-measured microcurrent. Logic oscillation is avoided in the switching process, and the stability of the detection process is improved; only one voltage acquisition and amplification branch is allowed to be switched on at any moment through optocoupler control, the leakage current phenomenon in micro-current measurement is effectively restrained through the high isolation characteristic of optocouplers, mutual interference between different branch resistors is avoided, thermal noise in a sampling circuit is remarkably reduced, and the sampling precision and the signal-to-noise ratio are improved.

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: 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.

[0008] 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.

[0009] 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.

[0010] 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: 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.

[0011] 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.

[0012] 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.

[0013] 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: 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 output voltage Voi of the current voltage acquisition and amplification branch. Step 2. Use the logic processing control circuit to compare the output voltage Voi of 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 for range switching. The voltage acquisition and amplification branch with the optocoupler conducting is the current active branch. Step 3. Except for the current active branch, the output end 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, and the latch enters the latch hold 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 achieve the range adaptive switching current detection of the hardware circuit.

[0014] Furthermore, the optocoupler of the switch unit controls the on and off of the voltage acquisition and amplification branch, and only one voltage acquisition and amplification branch conducts at any detection and sampling moment.

[0015] Furthermore, 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, 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, switch to the voltage acquisition and amplification branch with a measurement range larger than that 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, switch to the voltage acquisition and amplification branch with a measurement range smaller than that of the current voltage acquisition and amplification branch; After completing the range switching, the output signals of the comparators UL and UH of the current voltage acquisition and amplification branch are latched by the latch. When the enable signal E at the enable terminal of the latch connected to the output end of the NOT gate is in the valid 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.

[0016] In summary, the invention has the following beneficial effects: 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

[0017] Figure 1 This is a schematic diagram of the microampere-level current sampling network structure of the present invention; Figure 2 This is the circuit diagram of the voltage acquisition and amplification branch of the present invention; Figure 3 For upper and lower limit circuits in logic processing control circuits; Figure 4 This is the circuit diagram of the switching unit. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings.

[0019] 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 they do not limit the structure of the present invention.

[0020] like Figures 1-4 As 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.

[0021] 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.

[0022] 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.

[0023] 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: Ii_high= 10 6 Ii_low= 10 6 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.

[0024] 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.

[0025] 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.

[0026] 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: 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, it generates a voltage drop Vi 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. In the initial stage, the micro-current to be measured passes through the sampling resistor Ri of all voltage acquisition and amplification branches at the same time. After passing through the sampling resistor Ri and the instrumentation amplifier Gi, the same current will produce different output voltages in each voltage acquisition and amplification branch.

[0027] Step 2. Use the logic processing control circuit to compare the voltages output by all the 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 conducting optocoupler is the current active branch. After being judged by the logic processing control unit, only one voltage acquisition and amplification branch's optocoupler conducts at the same moment.

[0028] The range switching operation is as follows: 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, switch to the voltage acquisition and amplification branch with a voltage range greater than the measurement range of the current voltage acquisition and amplification branch; 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, switch to the voltage acquisition and amplification branch with a voltage range smaller than the measurement range of the current voltage acquisition and amplification branch; After completing the range switching, the output signals of the comparator UL and comparator UH of the current voltage acquisition and amplification branch are latched 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 the output terminal of the latch through a NOT gate.

[0029] Step 3. Except for the current active branch, the output terminals of the NOT gates in the logic processing control circuits of other voltage acquisition and amplification branches output the enable signal E to the latch, and the latch enters the latch holding 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 the range adaptive switching current detection of the hardware circuit. A closed-loop feedback control circuit is formed by the latch and the NOT gate. The latch latches the output of the comparator and feeds back the output through the NOT gate to the enable terminal of the latch, thereby avoiding logic oscillation during the range switching process and improving the stability of the current detection process.

[0030] The optocoupler of the switch unit controls the on and off of the voltage acquisition and amplification branch, and only one voltage acquisition and amplification branch conducts at any detection and sampling moment. The high isolation characteristic of the optocoupler can effectively suppress the leakage current phenomenon in the microcurrent measurement and avoid the mutual interference between the resistances of different voltage acquisition and amplification branches.

[0031] 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 self-adapting threshold microampere current sampling network structure, characterized in that: The application relates to a micro-current measuring device, which comprises a plurality of parallel voltage collection and amplification branches, the input ends of all the voltage collection and amplification branches are connected to a micro-current to be measured, a logic processing control circuit and a switch unit are arranged on each voltage collection and amplification branch, the logic processing control circuit judges whether the output voltage of the current voltage collection and amplification branch is within a preset voltage range composed of an upper limit voltage and a lower limit voltage through comparison, and outputs an enable control signal to the switch unit according to the judgment result to realize control of the light coupling of the switch unit and control of the selection state of the current voltage collection and amplification branch. The switch unit is provided with two signal control input ends, the first signal control input end of the switch unit is connected to the signal output end of the voltage collection and amplification branch, and the second signal control input end is connected to the signal output end of the logic processing control unit of the adjacent voltage collection and amplification branch.

2. The adaptive threshold microampere level current sampling network structure of claim 1, wherein: The voltage collection and amplification branch comprises a sampling resistor Ri and an instrument amplifier Gi, the input micro-current is converted into a voltage signal and amplified, and the output end of the instrument amplifier Gi is the amplified voltage to be measured Ui, wherein i represents the serial number of the voltage collection and amplification branch.

3. The adaptive threshold microampere level current sampling network structure of claim 2, wherein: The number of the voltage collection and amplification branches is not less than three, and the sampling resistor Ri has a value range of 100 omega to 10k omega.

4. The adaptive threshold microampere level current sampling network structure of claim 2, wherein: The gain calculation formula of the instrument amplifier Gi is GI = 1 + (100k omega / Rgi), Rgi represents the gain resistor of the instrument amplifier Gi, the current measurement range in the voltage collection and amplification branch is controlled through the amplifier gain resistor Rgi and the sampling resistor Ri, the gain adjustment range of the instrument amplifier Gi is 1 to 1000, the measurement range of the voltage collection and amplification branch is determined by the resistance value of the sampling resistor Ri and the gain GI of the instrument amplifier Gi, and the calculation formula of the current measurement upper limit and the current measurement lower limit of the voltage collection and amplification branch is respectively Ii_high = 0x00000000 10 6 Ii_low = 0.5 * (Ii + Ii_low) 10 6 Wherein, the units of the current measurement upper limit Ii_high and the current measurement lower limit Ii_low are μA, and the relationship between the preset upper limit voltage Vi_high and the lower limit voltage Vi_low is Vi_high=10 Vi_low, and i in Vi and Ii represents the serial number of the voltage collection and amplification branch.

5. The adaptive threshold microampere level current sampling network structure of claim 2, wherein: The logic processing control circuit comprises an upper limit circuit and a lower limit circuit for defining a preset voltage range of the current voltage acquisition amplification branch, the upper limit circuit comprises a comparator UH, a latch DH and a NOT gate EH, input ends of the comparator UH are connected to a signal output end of the voltage acquisition amplification branch and a preset upper limit voltage of the current voltage acquisition amplification branch respectively, an output end of the comparator UH is connected to an input end of the latch DH, an output end of the latch DH is connected to an input end of the NOT gate EH, an output end of the NOT gate EH is connected to an enable end of the latch DH, and simultaneously the output end of the NOT gate EH is connected to the switch unit as an output end of the upper limit circuit of the logic processing control circuit; the lower limit circuit comprises a comparator UL, a latch DL and a NOT gate EL, input ends of the comparator UL are connected to the signal output end of the voltage acquisition amplification branch and a preset lower limit voltage of the current voltage acquisition amplification branch respectively, an output end of the comparator UL is connected to an input end of the latch DL, an output end of the latch DL is connected to an input end of the NOT gate EL, an output end of the NOT gate EL is connected to an enable end of the latch DL, and simultaneously the output end of the NOT gate EL is connected to the switch unit as an output end of the lower limit circuit of the logic processing control circuit, the comparator UH and the comparator UL compare the to-be-measured output voltage of the current voltage acquisition amplification branch with the preset voltage range and output, the latch latches the output of the comparator, and the output of the NOT gate is taken as an output signal of the logic processing control circuit.

6. The adaptive threshold microampere level current sampling network structure of claim 1, wherein: The power supply circuit provides positive and negative dual power supply and a reference voltage for the voltage acquisition amplification branch, the logic processing control circuit and the switch unit.

7. A method for controlling the adaptive threshold microampere current sampling network based on the adaptive threshold microampere current sampling network structure of any one of claims 1-6, characterized in that: The to-be-measured micro current passes through the microampere current sampling network structure, a plurality of voltage acquisition amplification branches convert the micro current into a plurality of to-be-measured voltages, the logic processing control circuit compares the preset voltage range of the current voltage acquisition amplification branch with the to-be-measured voltage, controls the light coupling of the switch unit to complete selection of the voltage acquisition amplification branch, and realizes adaptive control of current sampling, and specifically comprises the following steps: Step 1. The to-be-measured micro current I flows into the microampere current sampling network structure, and a voltage drop Vi is generated on each voltage acquisition amplification branch through a sampling resistor Ri, and the output voltage Voi of the voltage drop Vi after being amplified by an instrument amplifier Gi with a preset gain is the voltage output by the current voltage acquisition amplification branch; Step 2. The logic processing control circuit compares all the voltages output by the voltage acquisition amplification branches obtained in step 1 with the preset voltage range of the voltage acquisition amplification branch, if the output voltage is within the preset voltage range, the logic processing control circuit of the current voltage acquisition amplification branch outputs a low level, and the light coupling of the switch unit is turned on, otherwise the light coupling is turned off to switch the range, and the voltage acquisition amplification branch with the turned-on light coupling is the current active branch. Step 3. The output end of the NOT gate in the logic processing control circuit of the other voltage acquisition and amplification branch except the current active branch outputs an enable signal E to the latch, the latch enters a latch holding state to shield the range switching request signal of the adjacent voltage acquisition and amplification branch before 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.

8. The adaptive threshold microampere level current sampling network control method of claim 7, wherein: The light coupling control voltage acquisition and amplification branch of the switch unit is turned on and off, and only one voltage acquisition and amplification branch is turned on at any detection sampling moment.

9. The adaptive threshold microampere level current sampling network control method of claim 7, wherein: 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, 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 voltage acquisition and amplification branch with a range larger than that of the current voltage acquisition and amplification branch is switched; If the output voltage Voi is lower than the lower limit voltage Vi_low 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 voltage acquisition and amplification branch with a range smaller than that of the current voltage acquisition and amplification branch is switched; After completing the range switching, the output end signals of the comparator UL and the comparator UH of the current voltage acquisition and amplification branch are latched by the latch, and when the enable signal E of the output end of the latch is in an effective state, the logic state is latched to the output end Q of the latch, and when the enable signal E is invalid, the original output state is maintained without change.

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