Analog quantity current input module, current acquisition method and programmable logic controller

Abstract

The invention provides an analog quantity current input module, a current acquisition method and a programmable logic controller, and the analog quantity current input module comprises a signal acquisition end which is provided with a plurality of mutually independent signal acquisition channels, each signal acquisition channel comprises a front-end signal conditioning circuit, an analog-to-digital conversion chip and a digital isolator with an isolated power supply signal; the front-end signal conditioning circuit converts an input current signal into a voltage signal, performs resistance-capacitance filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the central region of the measuring range of the analog-to-digital converter; the analog-to-digital converter collects an output signal of the front-end signal conditioning circuit for sampling to obtain a sampling signal; and the signal processing end is communicated with the analog-to-digital converter through the digital isolator so as to receive the sampling signal and process the sampling signal. According to the invention, the board occupation area can be effectively reduced and the circuit structure is simplified.

Description

Technical Field

[0001] This invention relates to the field of analog current input module, current acquisition method and programmable logic controller. Background Technology

[0002] In the non-safety domains of the nuclear power industry, analog input modules are a crucial component of programmable logic controllers (PLCs), used to acquire current signals from various sensors and convert them into digital signals for processing by the control system. With the increasing demands for signal acquisition accuracy, channel isolation, and system reliability in nuclear power equipment, the design of analog current input modules faces new challenges. However, existing analog current input modules still present some problems when applied in the nuclear power industry. First, conventional analog input units require each channel to employ an independent isolated DC-DC module and complete protection, signal conditioning, and acquisition designs to achieve inter-channel isolation. This results in a large number of voltage types and components, increasing system complexity and failure rate. Second, the need for independent power and signal isolation for each channel leads to a large PCB footprint, which is inconsistent with the design philosophy of modern high-density I / O units. Furthermore, the presence of multiple voltages increases circuit design complexity and power consumption, which is detrimental to the long-term stable operation of the system. Summary of the Invention

[0003] In view of the problems existing in the prior art, the present invention proposes an analog current input module, a current acquisition method and a programmable logic controller, which mainly solves the problems that the existing analog current input modules are highly complex, occupy a large layout area and are difficult to meet the application requirements of nuclear power scenarios.

[0004] To achieve the above and other objectives, the technical solution adopted by the present invention is as follows.

[0005] This invention provides an analog current input module, comprising: The signal acquisition terminal has multiple independent signal acquisition channels. Each signal acquisition channel includes a front-end signal conditioning circuit, an analog-to-digital converter chip, and a digital isolator with isolated power supply signals. The front-end signal conditioning circuit converts the input current signal into a voltage signal, performs RC filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the center region of the analog-to-digital converter's range. The analog-to-digital converter samples the output signal of the front-end signal conditioning circuit to obtain a sampled signal. Each signal sampling channel is powered by the digital isolator. The signal processing terminal communicates with the analog-to-digital converter through the digital isolator to receive and process the sampled signal.

[0006] In one embodiment of the present invention, the front-end signal conditioning circuit includes a sampling resistor, an RC filter unit, an instrumentation amplifier, and a reference voltage chip. The current signal is converted into a 0-1V voltage signal by the sampling resistor, filtered by the RC filter unit, and then sent to the instrumentation amplifier for common-mode rejection. Finally, a reference voltage of 1.2V is provided by the reference voltage chip, thereby raising the voltage range of the voltage signal output by the instrumentation amplifier to 1.2-2.2V. The instrumentation amplifier and the reference voltage chip are powered by the digital isolator.

[0007] In one embodiment of the present invention, the resistance of the sampling resistor is 50 ohms.

[0008] In one embodiment of the present invention, the amplification factor of the instrumentation amplifier is configured to be 1, and the instrumentation amplifier has overvoltage tolerance capability.

[0009] In one embodiment of the present invention, the digital isolator provides a power supply voltage of 3.3V.

[0010] In one embodiment of the present invention, the analog-to-digital converter receives the differential signal provided by the instrumentation amplifier, uses the 1.2V voltage provided by the reference voltage chip as the reference voltage, and uses the 3.3V voltage provided by the digital isolator as the logic level and power supply voltage to generate the sampling signal. The analog-to-digital converter is a 24-bit Sigma-Delta type analog-to-digital converter.

[0011] In one embodiment of the present invention, the signal acquisition terminal is grounded near the signal input side through a pull-down resistor, so that the voltage acquired when the signal acquisition terminal is not connected is kept at 0V, thereby realizing the disconnection detection.

[0012] The present invention also provides a current acquisition method based on the aforementioned analog current input module, the method comprising: Current signals are received through multiple relatively independent signal acquisition channels; Each of the signal acquisition channels converts the received current signal into a voltage signal, performs RC filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the center region of the analog-to-digital converter's range. Sampling is performed by the analog-to-digital converter, wherein each signal acquisition channel is independently powered and isolated from the signal processing terminal by a digital processor.

[0013] The present invention also provides a programmable logic controller, including: the analog current input module.

[0014] The present invention also provides a nuclear power device, including the aforementioned programmable logic controller.

[0015] As described above, the analog current input module, current acquisition method, and programmable logic controller provided by the present invention have the following beneficial effects.

[0016] The analog current input module is powered by a 3.3V digital isolator chip with isolated power supply, reducing the number of voltage types, lowering cost and board space, and reducing losses. The module has a small number of components; besides resistors and capacitors, it only contains an instrumentation amplifier, ADC chip, reference voltage chip, and digital isolator with isolated power supply, resulting in a high-density analog input unit with high compatibility with high-density I / O units. High-precision, low-temperature drift sampling resistors, differential input / output instrumentation amplifiers, and a 24-bit Sigma-Delta ADC chip ensure high accuracy; test results show the module's accuracy is better than 0.1%FS. Each channel is powered by an independent power supply, providing inter-channel interference immunity; test results show that when a square wave signal is applied to one channel, the code value of another channel remains almost unchanged. A 4-20mA open-circuit detection function is achieved by using a high-value pull-down resistor at the front end of the acquisition channel, while reducing leakage current and minimizing the impact of open-circuit detection on the acquired signal. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the analog current input module in one embodiment of the present invention; Figure 2 This is a schematic diagram of the wiring terminals of the signal acquisition terminal in one embodiment of the present invention; Figure 3 This is a flowchart illustrating the current acquisition method of the analog current input module in one embodiment of the present invention; Figure 4 This is a schematic diagram of the architecture of a programmable logic controller in one embodiment of this application. Detailed Implementation

[0018] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and 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 invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0019] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0020] Figure 1 This is a schematic diagram of the structure of an analog current input module in one embodiment of the present invention. The module includes a signal acquisition terminal and a signal processing terminal.

[0021] The signal acquisition unit has multiple independent signal acquisition channels. Each channel includes a front-end signal conditioning circuit, an analog-to-digital converter (ADC) chip, and a digital isolator with isolated power supply signals. The front-end signal conditioning circuit converts the input current signal into a voltage signal, performs RC filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the center region of the ADC's range. The ADC samples the output signal of the front-end signal conditioning circuit to obtain the sampled signal. Each signal sampling channel is powered by a digital isolator. The signal processing unit communicates with the ADC through the digital isolator to receive and process the sampled signal. The signal processing unit further processes the data, performs filtering and calibration, and then packages the data before transmitting it to the system's main control module.

[0022] The front-end signal conditioning circuit specifically includes a sampling resistor, an RC filter unit, an instrumentation amplifier, and a reference voltage chip. The current signal is converted into a 0-1V voltage signal by the sampling resistor. A high-precision, low-temperature-drift resistor with a resistance of 50 ohms is used, enabling the generation of an accurate 0-1V voltage signal within an input current range of 0-20mA. After filtering by the RC filter unit, the voltage signal is sent to the instrumentation amplifier for common-mode rejection. The instrumentation amplifier's amplification factor is configured to 1, and it has overvoltage tolerance capability to protect subsequent circuits from damage in abnormal conditions. Finally, a 1.2V reference voltage is provided by the reference voltage chip, raising the voltage range of the instrumentation amplifier's output signal to 1.2-2.2V, placing the signal within the optimal operating range of the analog-to-digital converter (i.e., the center region of the range). The instrumentation amplifier and reference voltage chip are powered by a digital isolator, which provides a 3.3V supply voltage. The RC filter unit can use a first-order RC low-pass filter. After filtering, the voltage signal enters the instrumentation amplifier via differential input. The instrumentation amplifier's amplification factor is set to 1. This greatly suppresses the common-mode rejection ratio and reduces interference without affecting the signal. A digital isolator with an isolated power supply can integrate isolation DC-DC converters and signal isolation onto a single chip, reducing board space.

[0023] The analog-to-digital converter (ADC) receives the differential signal from the instrumentation amplifier, uses a 1.2V reference voltage from the reference voltage chip as the reference voltage, and a 3.3V logic level and power supply voltage from the digital isolator to generate the sampling signal. The ADC employs a 24-bit Sigma-Delta type, characterized by high precision and high resolution, accurately converting analog signals into digital signals. The ADC utilizes a high-resolution, high-precision, and small-package ADC chip, ensuring efficient data acquisition while minimizing board space.

[0024] The signal acquisition terminal is grounded near the signal input via a pull-down resistor, ensuring that the voltage acquired when the terminal is not connected remains at 0V, thus enabling open-circuit detection. This design allows the system to automatically detect disconnections in the input signal line, improving system reliability and safety. A high-resistance resistor can be used to enable short-circuit detection for the 4-20mA input of the analog current input module. When the module is not connected, the acquired voltage remains at 0V, and the module uses 0-4mA for short-circuit detection. The high resistance of the pull-down resistor also prevents leakage current. The specific resistance value can be configured and adjusted according to actual application requirements; no restrictions are imposed here.

[0025] like Figure 2 As shown, the external structure of the analog current input module includes terminals for multiple signal acquisition channels, as well as structural components for installation and fixation. This design allows the module to be easily installed in the control system and can simultaneously process multiple current signal inputs, meeting the needs of industrial automation control systems.

[0026] Through the above structural design, this analog current input module can achieve high-precision acquisition and processing of multiple current signals. Simultaneously, the electrical isolation function provided by the digital isolator effectively prevents interference and protects system safety. The module's open-circuit detection function enhances system reliability, making it suitable for various industrial control applications.

[0027] Specifically, for each individual channel of the module, the 4-20mA and 0-20mA signals enter the module through the terminals and first go to the front-end signal conditioning circuit. The current passes through a 50Ω sampling resistor, converting the current signal into a 0-1V voltage signal. The voltage signal then passes through a first-order RC filter circuit with a cutoff frequency of 1.6kHz. The filtered signal is then sent to the instrumentation amplifier, which not only improves common-mode rejection but also meets the ±30V overvoltage requirement.

[0028] After the signal exits the instrumentation amplifier, it is boosted by a 1.2V reference voltage. This is to raise the sampling area to the center of the ADC chip's range, where linearity is good and accuracy at both ends of the sampling range is ensured. The 1.2V reference voltage is provided by a reference voltage chip, which has an initial accuracy of 0.1% and a maximum temperature drift of 8ppm / ℃. This 1.2V reference voltage also serves as the reference voltage for the ADC chip, reducing the impact of temperature drift.

[0029] The signal enters the ADC chip in differential input form. The chip uses an external reference voltage and operates on 3.3V for both logic level and power supply. The ADC's digital signal is isolated from the core board's voltage system via a digital isolator, and the chip also integrates an isolated DC-DC power supply. The 3.3V output from this chip powers the ADC chip, instrumentation amplifier, and reference voltage chip.

[0030] The signal output from the digital isolator is directly transmitted to the FPGA chip at the signal processing end. The FPGA then processes and packages the data before sending it to the system's central communication processing module. Users can retrieve the collected data through a host computer.

[0031] A signal is applied to the input channel, using 1 / 10 of the full-scale range as the minimum scale value. The current signal is then tested, and the data is read from the host computer software. The data obtained is shown in the table below:

[0032] It can be seen that the module's accuracy is better than 0.1%FS.

[0033] Two channels were then selected. Channel 1 was used for 10mA signal acquisition, and channel 2 was used with a signal generator to apply V=5V, 1Hz / 1KHz / 10KHz square wave signals. The code value changes of channel 1 were then read. The following data were obtained: Code value of channel 1 before applying the square wave signal: 32762; Code value after applying the 1Hz square wave signal: 32762; Code value after applying the 1KHz square wave signal: 32761; Code value after applying the 10KHz square wave signal: 32761. It can be seen that the module has the ability to resist interference between channels.

[0034] Based on the above, the analog current input module of this invention has an independent power supply system for each channel, which can greatly reduce the influence between channels. Unlike conventional analog input units that use ±15V to power the conditioning circuit, this invention only requires a 3.3V power supply, provided by a digital isolator with an isolated power supply, reducing the number of power supply types, saving space, and reducing losses. After the current signal enters the module, it is converted into a voltage signal by a precision resistor, then filtered and denoised by an instrumentation amplifier, and sent to a high-precision ADC. The ADC sends the converted digital signal to the digital isolator with an isolated power supply, and then to the core processor at the signal processing end, ensuring the high accuracy of the module. The acquisition section only contains an instrumentation amplifier, an ADC chip, a reference voltage chip, a digital isolator with an isolated power supply, and related resistors and capacitors, greatly reducing the number of components in each channel, making the analog input module highly dense.

[0035] Figure 3 This is a flowchart illustrating a current acquisition method for an analog current input module according to an embodiment of the present invention. The method is based on the aforementioned analog current input module.

[0036] The current acquisition method includes the following steps: Step S300: Receive current signals through multiple relatively independent signal acquisition channels.

[0037] In this step, multiple independent signal acquisition channels each receive current signals from different sources. For example... Figure 2 As shown, each signal acquisition channel receives current signal input in the range of 0-20mA through its own terminal block.

[0038] Step 310: Each signal acquisition channel converts the received current signal into a voltage signal, performs RC filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the center region of the analog-to-digital converter's range.

[0039] In this step, the current signal is first converted into a 0-1V voltage signal by a sampling resistor (50 ohms), and then filtered by an RC filter unit to remove high-frequency interference and noise. The filtered signal is then sent to an instrumentation amplifier for common-mode rejection to suppress common-mode interference signals. Finally, a reference voltage chip provides a 1.2V reference voltage, raising the voltage signal range to 1.2-2.2V, placing the signal in the center region of the analog-to-digital converter's range (where linearity is optimal), thus improving sampling accuracy.

[0040] Step 320: Sampling is completed through an analog-to-digital converter, wherein each signal acquisition channel is powered independently and isolated from the signal processing terminal by a digital processor.

[0041] In this step, the analog-to-digital converter (ADC) samples the voltage signal output from the front-end signal conditioning circuit. The ADC is a 24-bit Sigma-Delta type, receiving the differential signal from the instrumentation amplifier. It uses a 1.2V reference voltage provided by a reference voltage chip as the reference voltage and a 3.3V digital isolator as the logic level and power supply voltage to generate the sampling signal. Each signal acquisition channel is independently powered by a digital isolator, which provides a 3.3V supply voltage and achieves electrical isolation between the signal acquisition channel and the signal processing terminal, effectively preventing interference and protecting system safety.

[0042] In this method, the signal acquisition terminal is grounded near the signal input via a pull-down resistor, ensuring that the voltage acquired when the signal acquisition terminal is not connected remains at 0V, thus achieving the disconnection detection function. This design enables the system to automatically detect when the input signal line is disconnected, improving the system's reliability and safety.

[0043] Through the above steps, this current acquisition method can achieve high-precision acquisition and processing of multiple current signals. Simultaneously, the electrical isolation provided by the digital isolator effectively prevents interference and protects system safety. This method is suitable for various industrial control applications, especially those requiring high-precision current signal acquisition.

[0044] This embodiment provides a programmable logic controller (PLC) including an analog current input module. The analog current input module of the PLC includes a signal acquisition terminal and a signal processing terminal. The signal acquisition terminal has multiple independent signal acquisition channels, each including a front-end signal conditioning circuit, an analog-to-digital converter (ADC) chip, and a digital isolator with isolated power supply signals. The front-end signal conditioning circuit converts the input current signal into a voltage signal, performs RC filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the center region of the ADC's range. The ADC samples the output signal of the front-end signal conditioning circuit to obtain a sampled signal. Each signal sampling channel is powered by a digital isolator. The signal processing terminal communicates with the ADC through the digital isolator to receive and process the sampled signals.

[0045] Please see Figure 4 , Figure 4This is a schematic diagram of the architecture of a programmable logic controller (PLC) according to one embodiment of this application. The PLC includes a main control module, a communication processing module, an I / O module, and a power supply. The power supply can be a 24V power supply. The I / O module can include the aforementioned analog current input module. The I / O module communicates with the communication processing module based on LVDS. The collected signals are filtered and merged by the communication processing module before being sent to the main control module. The main control module can interact with a PC and display the collected information on the PC's display interface.

[0046] In one embodiment, the front-end signal conditioning circuit includes a sampling resistor, an RC filter unit, an instrumentation amplifier, and a reference voltage chip. The current signal is converted into a 0-1V voltage signal by the sampling resistor, filtered by the RC filter unit, and then sent to the instrumentation amplifier for common-mode rejection. Finally, a 1.2V reference voltage is provided by the reference voltage chip, raising the voltage range of the output voltage signal from the instrumentation amplifier to 1.2-2.2V. The instrumentation amplifier and the reference voltage chip are powered by a digital isolator. This design raises the voltage signal to the center region of the analog-to-digital converter's range, improving sampling accuracy.

[0047] In one embodiment, the sampling resistor has a resistance of 50 ohms. This resistance value is designed so that when the current signal is 0-20mA, the converted voltage signal ranges from 0-1V, meeting the requirements of subsequent signal processing.

[0048] In one embodiment, the instrumentation amplifier is configured with a gain of 1 and has overvoltage withstand capability. This design ensures accurate signal transmission, enhances the system's resistance to abnormal currents, and improves the overall reliability of the module.

[0049] In one embodiment, the digital isolator provides a 3.3V supply voltage. This voltage is suitable for powering subsequent electronic components while achieving electrical isolation between signal channels, enhancing the system's immunity to interference.

[0050] In one embodiment, the analog-to-digital converter (ADC) receives a differential signal from an instrumentation amplifier, uses a 1.2V voltage from a reference voltage chip as the reference voltage, and a 3.3V voltage from a digital isolator as the logic level and power supply voltage to generate a sampling signal. The ADC employs a 24-bit Sigma-Delta type, which provides higher sampling accuracy to meet the precision measurement requirements of industrial control environments.

[0051] In one embodiment, the signal acquisition terminal is grounded near the signal input via a pull-down resistor, ensuring that the voltage acquired when the signal acquisition terminal is not connected remains at 0V, thus enabling open-circuit detection. This design enhances the system's self-diagnostic capabilities; when the input signal line is disconnected, the system can automatically detect this abnormal state, improving the system's reliability and safety.

[0052] The working process of this programmable logic controller is as follows: it receives current signals through multiple relatively independent signal acquisition channels; each signal acquisition channel converts the received current signal into a voltage signal, performs RC filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the center region of the analog-to-digital converter's range; sampling is completed through the analog-to-digital converter. Each signal acquisition channel is independently powered and isolated from the signal processing terminal by a digital processor.

[0053] This programmable logic controller (PLC) integrates a high-precision analog current input module, enabling high-precision acquisition and processing of multiple current signals. The electrical isolation design of each signal channel enhances the system's anti-interference capability and safety, making it suitable for control applications in various complex industrial environments. Simultaneously, the module's open-circuit detection function improves the system's self-diagnostic capabilities, making system operation more reliable.

[0054] This invention provides a nuclear power equipment, which includes a programmable logic controller (PLC) and an analog current input module.

[0055] The programmable logic controller (PLC) in this nuclear power equipment has the same structure as the aforementioned PLC, including an analog current input module with multiple signal acquisition channels. This analog current input module includes a signal acquisition end and a signal processing end. The signal acquisition end has multiple independent signal acquisition channels, each channel including a front-end signal conditioning circuit, an analog-to-digital converter chip, and a digital isolator with isolated power supply signals.

[0056] In this nuclear power equipment, the front-end signal conditioning circuit of the analog current input module converts the input current signal into a voltage signal. After applying RC filtering and common-mode rejection to the voltage signal, the voltage range is raised to the center region of the analog-to-digital converter's (ADC) range. The ADC samples the output signal of the front-end signal conditioning circuit to obtain the sampled signal. Each signal sampling channel is powered by a digital isolator, and the signal processing unit communicates with the ADC through the digital isolator to receive and process the sampled signal.

[0057] The analog current input module in the programmable logic controller of this nuclear power plant adopts the technical features described in Embodiment 3, including a sampling resistor of 50 ohms, an instrumentation amplifier with an amplification factor of 1 and overvoltage withstand capability, a digital isolator providing a 3.3V power supply voltage, a 24-bit Sigma-Delta analog-to-digital converter, and a signal acquisition end grounded near the signal input side through a pull-down resistor to achieve a disconnection detection function.

[0058] This nuclear power equipment utilizes a high-precision analog current input module, enabling high-precision acquisition and processing of multiple current signals in a nuclear power environment. The electrical isolation design of each signal channel enhances the system's anti-interference capability and safety, making it particularly suitable for operating environments like nuclear power plants where safety and reliability requirements are extremely high. The module's open-circuit detection function improves the system's self-diagnostic capabilities, making the nuclear power equipment more reliable and effectively reducing safety risks during operation.

[0059] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An analog current input module, characterized in that, include: The signal acquisition terminal has multiple independent signal acquisition channels. Each signal acquisition channel includes a front-end signal conditioning circuit, an analog-to-digital converter chip, and a digital isolator with isolated power supply signal. The front-end signal conditioning circuit converts the input current signal into a voltage signal, performs RC filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the center region of the range of the analog-to-digital converter. The analog-to-digital converter samples the output signal of the front-end signal conditioning circuit to obtain a sampled signal; wherein each of the signal sampling channels is powered by the digital isolator. The signal processing terminal communicates with the analog-to-digital converter through the digital isolator to receive and process the sampled signal.

2. The analog current input module according to claim 1, characterized in that, The front-end signal conditioning circuit includes a sampling resistor, an RC filter unit, an instrumentation amplifier, and a reference voltage chip. The current signal is converted into a 0-1V voltage signal by the sampling resistor, filtered by the RC filter unit, and then sent to the instrumentation amplifier for common-mode rejection. Finally, the reference voltage chip provides a 1.2V reference voltage, raising the voltage range of the voltage signal output by the instrumentation amplifier to 1.2-2.2V. The instrumentation amplifier and the reference voltage chip are powered by the digital isolator.

3. The analog current input module according to claim 2, characterized in that, The resistance of the sampling resistor is 50 ohms.

4. The analog current input module according to claim 2, characterized in that, The amplification factor of the instrumentation amplifier is configured to be 1, and the instrumentation amplifier has overvoltage tolerance capability.

5. The analog current input module according to claim 2, characterized in that, The digital isolator provides a 3.3V supply voltage.

6. The analog current input module according to claim 5, characterized in that, The analog-to-digital converter receives the differential signal provided by the instrumentation amplifier, uses the 1.2V voltage provided by the reference voltage chip as the reference voltage, and the 3.3V voltage provided by the digital isolator as the logic level and power supply voltage to generate the sampling signal. The analog-to-digital converter is a 24-bit Sigma-Delta type analog-to-digital converter.

7. The analog current input module according to claim 1, characterized in that, The signal acquisition terminal is grounded near the signal input side through a pull-down resistor, so that the voltage acquired when the signal acquisition terminal is not connected remains at 0V, thereby realizing the disconnection detection.

8. A current acquisition method based on the analog current input module according to any one of claims 1-7, characterized in that, The method includes: Current signals are received through multiple relatively independent signal acquisition channels; Each of the signal acquisition channels converts the received current signal into a voltage signal, performs RC filtering and common-mode rejection on the voltage signal, and then raises the voltage range of the voltage signal to the center region of the analog-to-digital converter's range. Sampling is performed by the analog-to-digital converter, wherein each signal acquisition channel is independently powered and isolated from the signal processing terminal by a digital processor.

9. A programmable logic controller, characterized in that, include: The analog current input module as described in any one of claims 1-8.

10. A nuclear power equipment, characterized in that, Includes the programmable logic controller as described in claim 9.

Images