Configurable Multi-Channel Analog Quantity Acquisition System and Calibration Method

Abstract

The configurable multi-channel analog quantity acquisition system and calibration method of the present invention relate to the airborne analog quantity interface acquisition technology, and include a main path, a comparison path, a control unit and an electromechanical system. The main path and the comparison path respectively perform data interaction with the control unit, and the control unit performs data interaction with the electromechanical system. By comparing the data collected in real time by the main path and the comparison path, the system reliability can be improved; by configuring the switch matrix, the system can work in a single-ended working mode or a differential working mode; by configuring the gain network coefficient, the system can adjust the amplification factor in real time to adapt to the wide-range analog quantity acquisition. The calibration method includes zero-level system error calibration, A / D conversion unit full-scale error calibration and system full-scale error calibration. By comprehensively applying the system and calibration method of the present invention, the voltage acquisition range and working mode can be configured to achieve high-precision acquisition of multi-channel analog quantities.

Description

Technical Field

[0001] The present invention belongs to the technical field of sonar buoys, and particularly relates to a configurable multi-channel analog acquisition system and a calibration method. Background Art

[0002] A large number of analog input sensors such as temperature, flow, pressure, liquid level, and speed are included in the aircraft electromechanical system, and the requirements for their measurement accuracy, acquisition speed, and data stability are getting higher and higher. On the other hand, in order to more truly and accurately reflect the characteristics of the measured object, many test items have turned to dynamic parameter testing. As an important part of the aircraft electromechanical management data acquisition system, the data throughput capacity, acquisition accuracy, processing speed, and system reliability of the analog acquisition system directly affect the control indicators of the aircraft electromechanical management system. Therefore, designing a multi-channel, high-precision, high-reliability, and high-data-throughput-capacity analog acquisition system has become an important way to improve the comprehensive level and control performance of aircraft electromechanics.

[0003] The systematic error of the analog acquisition interface mainly comes from the zero-level systematic error caused by ground wire interference, the full-scale error of the A / D conversion unit, and the non-linear systematic error caused by the voltage division equivalent network, instrumentation operational amplifier, gain configuration network, etc. Traditional analog acquisition systems often perform simple acquisition and correction, and cannot accurately reflect the characteristics of the external system, and their acquisition accuracy directly affects the aircraft control performance. Summary of the Invention

[0004] In view of this, the present invention provides a configurable multi-channel analog acquisition system to solve the technical problem of large systematic error of the analog acquisition interface.

[0005] There is provided a configurable multi-channel analog acquisition system applicable to signal acquisition of an airborne electromechanical system. The system includes a main path, a comparison path, and a control unit. The main path and the comparison path perform data interaction with the control unit respectively, and the control unit performs data interaction with the electromechanical system;

[0006] The main path includes a conditioning unit, a first switch matrix, a first instrumentation operational amplifier, a first four-to-one switch, a first voltage follower unit, a first phase compensation unit, and a first A / D conversion unit connected in sequence. The comparison path includes a second switch matrix and a second instrumentation operational amplifier, a second four-to-one switch, a second voltage follower unit, a second phase compensation unit, and a second A / D conversion unit. The conditioning unit is used for conditioning of signal input. Among them: the first switch matrix is used to select the channel of signal input and is electrically connected to a reference reference source, so that the analog acquisition system operates in a single-ended working mode or a differential working mode. When in the single-ended working mode, the first switch matrix and the second switch matrix are mutually exclusive; when operating in the differential working mode, the switching logics of the first switch matrix and the second switch matrix are the same;

[0007] A second switch matrix for selecting a channel for signal input and electrically connected to a reference source, causing the analog acquisition system to operate in a single-ended mode or a differential mode;

[0008] The first gain configuration network inputs signals to the first instrumentation amplifier, and realizes preset configuration of the amplification factor through parameter configuration;

[0009] The positive terminal of the first instrumentation amplifier is connected to the output terminal of the first switch matrix, and the negative terminal is connected to the output terminal of the second switch matrix for amplifying the differential voltage of the first switch matrix and the second switch matrix. The output terminal is sequentially connected to the first four-to-one switch, a voltage follower unit, a phase compensation unit, and an A / D conversion unit;

[0010] The first four-to-one switch and the second four-to-one switch can diagnose a faulty circuit by selecting different input terminals;

[0011] The positive terminal of the second instrumentation amplifier is connected to the output terminal of the second switch matrix, and the negative terminal is connected to the output terminal of the first switch matrix for amplifying the differential voltage of the second switch matrix and the first switch matrix. The output terminal is sequentially connected to a second four-to-one switch, a second voltage follower unit, a second phase compensation unit, and a second A / D conversion unit;

[0012] By real-time comparison of the first A / D conversion unit and the second A / D conversion unit, it is detected whether the analog system is faulty, ensuring the reliability and accuracy of the input voltage;

[0013] The control unit includes a DSP, an FPGA, an SRAM, and a FLASH. The DSP performs data interaction with the FPGA through a DMA bus. The FPGA interacts with the main path and the comparison path simultaneously through a control address bus, a control bus, and a data bus. The DSP performs data processing and BIT calculation, and the FPGA performs acquisition channel logic control.

[0014] Advantages of the present invention:

[0015] Overcoming the defect of large acquisition error in the prior art, by real-time comparison of data acquired by the main path and the comparison path to improve system reliability; by configuring the switch matrix, the system can operate in a single-ended mode or a differential mode; by configuring the gain network coefficient, the system can adjust the amplification factor in real time to adapt to wide-range analog acquisition. The calibration method includes zero-level system error calibration, A / D conversion unit full-scale error calibration, and system full-scale error calibration. By comprehensively applying the system and calibration method of the present invention, the voltage acquisition range and working mode can be configured to achieve high-precision acquisition of multi-channel analog quantities. Description of the Drawings

[0016] To more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the accompanying drawings required for the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0017] Figure 1 It is a functional block diagram of a configurable multi-channel analog acquisition system;

[0018] Figure 2 It is a flowchart for executing the comprehensive calibration method;

[0019] Figure 3 It is a flowchart for calibrating the zero-level system error;

[0020] Figure 4 It is a flowchart for calibrating the full-scale error of the A / D conversion unit;

[0021] Figure 5 It is a flowchart for calibrating the full-scale error of the system;

[0022] Wherein:

[0023] 21. The first switch matrix; 22. The first instrumentation operational amplifier; 23. The first four-way one-select switch; 24. The first voltage follower unit; 25. The first phase compensation unit; 26. The first A / D conversion unit; 31. The second switch matrix; 32. The second instrumentation operational amplifier; 33. The second four-way one-select switch; 34. The second voltage follower unit; 35. The second phase compensation unit; 36. The second A / D conversion unit. Specific Embodiments

[0024] The following will describe the embodiments of the present disclosure in detail with reference to the accompanying drawings.

[0025] The following illustrates the embodiments of the present disclosure through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present disclosure, rather than all embodiments. The present disclosure can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0026] Note that the following description pertains to various aspects of embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on this disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of the aspects set forth herein can be used to implement a device and / or practice a method. Additionally, this device and / or method can be implemented using other structures and / or functionality in addition to one or more of the aspects described herein.

[0027] As Figure 1 shown, the configurable multi-channel analog acquisition system is applicable to signal acquisition of the airborne upper electro-mechanical system. The system includes a main path, a comparison path, and a control unit. The main path and the comparison path (both through the address bus, control bus, and data bus) perform data interaction with the control unit, and the control unit performs data interaction with the electro-mechanical system;

[0028] The main path includes a conditioning unit (conditioning of the signal input and determining whether the external signal is disconnected or not connected) electrically connected in sequence, a first switch matrix 21, a first instrumentation amplifier 22, a first four-to-one switch 23, a first voltage follower unit 24, a first phase compensation unit 25, and a first A / D conversion unit 26. The comparison path includes a second switch matrix 31 and a second instrumentation amplifier 32, a second four-to-one switch 33, a second voltage follower unit 34, a second phase compensation unit 35, and a second A / D conversion unit;

[0029] Wherein: Both the first switch matrix 21 and the second switch matrix 31 are multi-select switches for selecting the channel of the signal input (as one of the channels in the conditioning unit). Specifically, the first switch matrix 21 is electrically connected to a reference source, for example, (+10V, -10V, reference ground). The operation of the first switch matrix 21 causes the analog acquisition system to operate in a single-ended working mode or a differential working mode (the single-ended working mode or the differential working mode is switched or selected based on the parameter configuration of the electro-mechanical management system). When operating in the single-ended working mode, for the first switch matrix 21 and the second switch matrix 31 included in the main path and the comparison path, the input of one of them is configured as analog input, and the input of the other is configured as analog ground input. Specifically:

[0030] When operating in the differential working mode, the switching logic of the first switch matrix 21 and the second switch matrix 31 is the same; when operating in the single-ended working mode, the first switch matrix 21 and the second switch matrix 31 are mutually exclusive. Mutually exclusive means that one of the first switch matrix 21 and the second switch matrix 31 is configured as input, and the other is configured as reference ground;

[0031] The working principle of the second switch matrix 31 is the same as that of the first switch matrix 21, which is used to select the channel for signal input (one channel in the conditioning unit). Specifically, the second switch matrix 31 is also configured with reference reference sources (+10V, -10V, reference ground) as power supplies, enabling the analog acquisition system to operate in a single-ended mode or a differential mode;

[0032] The first gain configuration network inputs signals to the first instrumentation operational amplifier 22 and realizes the preset configuration of the amplification factor through parameter configuration, and is used as a resistor network;

[0033] The positive terminal of the first instrumentation operational amplifier 22 is connected to the output terminal of the first switch matrix 21, and the negative terminal is connected to the output terminal of the second switch matrix 31 for amplifying the differential voltage of the first switch matrix 21 and the second switch matrix 31. The output terminal is sequentially connected to the first four-way selector switch 23, the first voltage follower unit 24, the first phase compensation unit 25, and the first A / D conversion unit 26;

[0034] The first four-way selector switch 23 can diagnose the faulty circuit by selecting different inputs. When it is disconnected, 10V is input, and it is judged whether the output of the first A / D conversion unit 26 is 10V. If it is not 10V, it indicates a fault. Similarly, it can be known whether (the first voltage follower unit 24, the first phase compensation unit 25, and the first A / D conversion unit 26) are faulty. If the first A / D conversion unit 26 is normal but the system still has a fault, it means that there is a problem with the circuit in front of the first A / D conversion unit 26.

[0035] The positive terminal of the second instrumentation operational amplifier 32 is connected to the output terminal of the second switch matrix 31, and the negative terminal is connected to the output terminal of the first switch matrix 21 for amplifying the differential voltage of the second switch matrix 31 and the first switch matrix 21. The output terminal is sequentially connected to the second four-way selector switch 33, the second voltage follower unit 34, the second phase compensation unit 35, and the second A / D conversion unit;

[0036] By comparing the first A / D conversion unit 26 and the second A / D conversion unit in real time, it is detected whether the analog quantity system is faulty, ensuring the reliability and accuracy of the input voltage. Detection is carried out through self-checking. First, no signal is input, and self-checking is performed for the input of 10V and -10V voltages. If there is a problem, repair it. If there is no problem, it can be used normally; if there is a problem during use, it is used as a single-ended with the ground (analog ground).

[0037] Overall, the hardware architectures and control logics of the comparison path and the main path are exactly the same.

[0038] The control unit includes a DSP, an FPGA, an SRAM, and a FLASH. The DSP interacts with the FPGA through a DMA bus for data exchange. The FPGA interacts with both the main path and the comparison path simultaneously through the control address bus, the control bus, and the data bus. The DSP performs data processing and BIT resolution, and the FPGA performs acquisition channel logic control.

[0039] As the specific implementation provided in this case, the last three channel inputs of the first switch matrix 21, the first switch matrix 21, the first four-to-one switch 23, and the second four-to-one switch 33 are +10V reference reference source, -10V reference reference source, and analog ground respectively.

[0040] As the specific implementation provided in this case, the conditioning circuit includes a resistor RI, a resistor R0, a voltage-dividing equivalent resistor R2, a capacitor C1, a diode V1, and a diode V2. The resistor R1 and the capacitor C1 form a low-pass filtering function; the diodes V1 and V2 form a voltage clamping function; the voltage-dividing equivalent resistor R2 is connected to the FPGA through the control bus, and the resistor R1 and the voltage-dividing equivalent resistor R2 form a high-voltage adjustment function; R0 is connected to a -2.5V power supply to form an external load disconnection judgment function, and the value of R0 is generally between 1MΩ and 10MΩ.

[0041] As the specific implementation provided in this case, when the voltage collected by the main channel or the comparison channel is less than 1 / 3 of the full scale, or greater than 2 / 3 of the full scale, the resistance values of the first gain configuration network, the second gain configuration network, and the voltage-dividing equivalent resistor R2 are adjusted so that the acquisition result is between 1 / 3 and 2 / 3 of the full scale. For example, for the main channel, with a full scale of 10V, if the acquisition result is 1V, the signal is amplified by adjusting the first gain configuration network until (the voltage is less than 1 / 3 of the full scale or greater than 2 / 3 of the full scale) and no amplification is required. The result at this time is used as the output result of the A / D main path.

[0042] Functionality: When the input signal is single-ended input, if the collected voltage is less than the negative voltage threshold, it is determined that the input channel is open; when the input signal is differential input, if the acquisition result of one path of the main path and the comparison path is positive full-scale deflection and the acquisition result of the other path is negative full-scale deflection, it is determined that the differential input is open.

[0043] Secondly, a calibration method for multi-channel analog acquisition is provided, as Figure 2 shown. It uses the above-mentioned system in part or in whole and uses zero-level system error calibration, A / D conversion unit full-scale error calibration, and system full-scale error calibration, including:

[0044] Step 1: Use zero-level system error calibration to calibrate the nonlinear errors caused by the offset voltage and offset current of the main path and the comparison path;

[0045] Step 2. Use the full-scale errors of the first and second A / D conversion units to calibrate the non-linear errors caused by the first A / D conversion unit 26 or the second A / D conversion unit 36;

[0046] Step 3. Use the system full-scale error calibration to combine with the non-linear error calibration to calibrate the non-linear errors caused by the voltage-dividing equivalent network, the first instrumentation operational amplifier 22, the second instrumentation operational amplifier 32, and the gain configuration network;

[0047] Step 4. Use the system full-scale error calibration minus the zero-level system error calibration result as the final calibration result. Specifically:

[0048] I. As shown in Figure 3 , the zero-level system error calibration includes:

[0049] Step 1: Switch the inputs of the first four-way switch 23 and the second four-way switch 33 to the fourth channel, which is the analog ground. The acquisition results of the first A / D conversion unit 26 and the second A / D conversion unit 36 are V 01a and V 02a respectively;

[0050] Step 2: Switch the inputs of the first switch matrix 21 and the second switch matrix 31 to the (n + 3)-th channel, which is the analog ground. Switch the inputs of the first four-way switch 23 and the second four-way switch 33 to the first channel. The acquisition results of the first A / D conversion unit 26 and the second A / D conversion unit 36 are V 01b and V 02b respectively;

[0051] Step 3: Calculate the zero-level system error calibration of the main channel as V 01 = V 01b - V 01a , and calculate the zero-level system error calibration of the comparison channel as V 02 = V 02b - V 02a .

[0052] II. As shown in Figure 4 , the full-scale error calibration includes:

[0053] Step 1: For the positive full-scale acquisition of the A / D conversion unit, switch the inputs of the first four-way switch 23 and the second four-way switch 33 to the second channel, which is the +10V reference source. The acquisition results of the first A / D conversion unit 26 and the second A / D conversion unit 36 are V A1+a and V A2+a respectively. Calculate the positive full-scale acquisition result of the first A / D conversion unit 26 as V A1+ = V A1+a - V 01a, the positive full-scale acquisition result of the second A / D conversion unit 36 is V A2+ = V A2+a - V 02a ;

[0054] Step 2: A / D conversion unit negative full-scale acquisition. The inputs of the first four-to-one switch 23 and the second four-to-one switch 33 are switched to the third channel -10V reference source. The acquisition results of the first A / D conversion unit 26 and the second A / D conversion unit 36 are V A1-b and V A2-b respectively. Calculate that the positive full-scale acquisition result of the first A / D conversion unit 26 is V A1- = V A1-b - V 01a , and the positive full-scale acquisition result of the second A / D conversion unit 36 is V A2- = V A2-b - V 02a ;

[0055] Step 3: Calculate the non-linear gain error of the A / D conversion unit, including:

[0056] The non-linear gain error of the first A / D conversion unit 26 ;

[0057] The non-linear gain error of the second A / D conversion unit 36 ;

[0058] Step 4: Calculate the non-linear offset error of the A / D conversion unit, including:

[0059] The non-linear offset error of the first A / D conversion unit 26: ;

[0060] The non-linear offset error of the second A / D conversion unit 36: ;

[0061] Step 5: Calculate the full-scale error calibration of the A / D conversion unit, including:

[0062] The full-scale error calibration of the first A / D conversion unit 26 is: , being the acquisition result of the first A / D conversion unit;

[0063] The full-scale error calibration of the second A / D conversion unit 36 is: , being the acquisition result of the A / D conversion unit 1.

[0064] III. The full-scale error calibration of the system as Figure 5 shown, including:

[0065] Step 1: The system performs positive full-scale acquisition. The inputs of the first switch matrix 21 and the second switch matrix 32 are switched to the (n + 2)-th channel +10V reference source. The inputs of the first four-to-one switch 23 and the second four-to-one switch 33 are switched to the first channel. The amplification factors of the first gain network and the second gain network are configured to be 1. The acquisition results of the first A / D conversion unit 26 and the second A / D conversion unit 36 are V S1+a and V S2+a ;

[0066] The positive full-scale acquisition result of the first A / D conversion unit is , and the positive full-scale acquisition result of the second A / D conversion unit is ;

[0067] Step 2: The system performs negative full-scale acquisition. The inputs of the first switch matrix 21 and the second switch matrix 31 are switched to the (n + 3)-th channel -10V reference source. The inputs of the first four-to-one switch 23 and the second four-to-one switch 33 are switched to the first channel. The amplification factors of the first gain network and the second gain network are configured to be 1. The acquisition results of the first A / D conversion unit 26 and the second A / D conversion unit 36 are V S1-b and V S2-b . Calculate that the negative full-scale acquisition result of the first A / D conversion unit 26 is , and calculate that the negative full-scale acquisition result of the second A / D conversion unit 36 is ;

[0068] Step 3: Calculate the channel non-linear gain error, including:

[0069] The non-linear gain error of the main channel is ;

[0070] The non-linear gain error of the comparison channel is ;

[0071] Step 4: Calculate the channel non-linear offset error.

[0072] The non-linear offset error of the main channel: ;

[0073] The non-linear offset error of the comparison channel: ;

[0074] Step 5: Calculate the full-scale error calibration of the channel, including:

[0075] The full-scale error calibration of the main channel is: , where: is the acquisition result after full-scale error calibration by the A / D conversion unit. The calculation method is: , It is the acquisition result of the first A / D conversion unit of the main channel;

[0076] The full-scale error calibration of the comparison channel is: , where: is the acquisition result after the full-scale error calibration of the A / D conversion unit, and the calculation method is: , is the acquisition result of the second main channel A / D conversion unit.

[0077] The above is only the specific implementation manner of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any change or replacement that can be easily thought of by those skilled in the art within the technical scope disclosed by the present disclosure should be covered by the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

1. A configurable multi-channel analog acquisition system, applicable to signal acquisition of an airborne electromechanical system, characterized in that The system includes a main path, a comparison path, and a control unit. The main path and the comparison path respectively perform data interaction with the control unit, and the control unit performs data interaction with the electromechanical system; The main path includes a conditioning unit, a first switch matrix, a first instrumentation amplifier, a first four-to-one switch, a first voltage follower unit, a first phase compensation unit, and a first A / D conversion unit connected in sequence. The comparison path includes a second switch matrix and a second instrumentation amplifier, a second four-to-one switch, a second voltage follower unit, a second phase compensation unit, and a second A / D conversion unit. The conditioning unit is used for conditioning of signal input. Among them, The first switch matrix is used to select the channel of signal input and is electrically connected to a reference reference source, causing the analog acquisition system to work in a single-ended working mode or a differential working mode. When in the single-ended working mode, the first switch matrix and the second switch matrix are mutually exclusive; when working in the differential working mode, the switching logics of the first switch matrix and the second switch matrix are the same; The second switch matrix is used to select the channel of signal input and is electrically connected to a reference reference source, causing the analog acquisition system to work in a single-ended working mode or a differential working mode; A gain configuration network is used to input a signal to the first instrumentation amplifier, and preset configuration of the amplification factor is achieved through parameter configuration; The positive terminal of the first instrumentation amplifier is connected to the output terminal of the first switch matrix, and the negative terminal is connected to the output terminal of the second switch matrix for amplifying the differential voltage of the first switch matrix and the second switch matrix. The output terminal is sequentially connected to the first four-to-one switch, the first voltage follower unit, the first phase compensation unit, and the first A / D conversion unit. The first four-to-one switch and the second four-to-one switch can diagnose a faulty circuit by selecting different input terminals; The positive terminal of the second instrumentation amplifier is connected to the output terminal of the second switch matrix, and the negative terminal is connected to the output terminal of the first switch matrix for amplifying the differential voltage of the second switch matrix and the first switch matrix. The output terminal is sequentially connected to the second four-to-one switch, the second voltage follower unit, the second phase compensation unit, and the second A / D conversion unit; By real-time comparison of the first A / D conversion unit and the second A / D conversion unit, it is detected whether the analog quantity system is faulty, ensuring the reliability and accuracy of the input voltage; The control unit includes a DSP, an FPGA, an SRAM, and a FLASH. The DSP performs data interaction with the FPGA through a DMA bus. The FPGA simultaneously interacts with the main path and the comparison path through a control address bus, a control bus, and a data bus. The DSP performs data processing and BIT resolution, and the FPGA performs acquisition channel logic control.

2. The configurable multi-channel analog quantity acquisition system according to claim 1, characterized in that: Both the first switch matrix and the second switch matrix are multi-switch matrices. The last three channel inputs of the first switch matrix, the second switch matrix, the first four-to-one switch, and the second four-to-one switch are respectively a +10V reference reference source, a -10V reference reference source, and an analog ground.

3. The configurable multi-channel analog quantity acquisition system according to claim 1, characterized in that It also includes a conditioning circuit, which includes a resistor RI, a resistor R0, a voltage-dividing equivalent resistor R2, a capacitor C1, a diode V1, and a diode V2, wherein: The resistor R1 and the capacitor C1 form a low-pass filtering function; the diode V1 and the diode V2 form a voltage clamping function; the voltage-dividing equivalent resistor R2 is connected to the FPGA through the control bus, and the resistor R1 and the voltage-dividing equivalent resistor R2 form a high-voltage adjustment function; R0 is connected to the -2.5V power supply to form an external load disconnection judgment function.

4. The configurable multi-channel analog quantity acquisition system according to claim 1, wherein When working in a single-ended working mode, the input of one of the first switch matrix and the second switch matrix is randomly configured as an analog input, and the input of the other is configured as an analog ground input; When operating in a differential operating mode, the switching logic of the first switch matrix and the second switch matrix are the same.

5. A calibration method for multi-channel analog quantity acquisition, characterized in that, The system according to any one of claims 1 to 4 is used, and zero-level system error calibration, A / D conversion unit full-amplitude error calibration and system full-amplitude error calibration are used, including: Step 1: Using zero-scale system error to calibrate nonlinear errors caused by bias voltage and offset current of the main path and comparison path; Step 2: using the full amplitude errors of the first and second A / D conversion units to calibrate the nonlinear error caused by the first A / D conversion unit or the second A / D conversion unit; Step 3 uses system full amplitude error calibration, combined with nonlinear error calibration to calibrate the nonlinear error caused by the voltage divider equivalent network, the first instrumentation amplifier, the second instrumentation amplifier, and the first gain configuration network; Step 4: Use the system full-scale error calibration minus the zero-scale system error calibration result as the final calibration result.

6. The calibration method according to claim 5, wherein The zero-level system error calibration includes: Step 1: The inputs of the first four-choose-one switch and the second four-choose-one switch are switched to the fourth channel as the analog ground, and the acquisition results of the first A / D conversion unit and the second A / D conversion unit are V 01a and V 02a ; Step 2: The inputs of the first switch matrix and the second switch matrix are switched to the analog ground of the n+3th channel, the inputs of the first four-to-one switch and the second four-to-one switch are switched to the 1st channel, and the acquisition results of the first A / D conversion unit and the second A / D conversion unit are V 01b and V 02b ; Step 3: Calculate the zero-scale system error calibration of the main channel as V 01 = V 01b -V 01a , the comparison channel zero-scale system error is calibrated to V 02 = V 02b -V 02a .

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