Signal acquisition circuit, IO card and distributed control system
By designing a signal acquisition circuit including a controller, an analog-to-digital converter, a HART modem, a filter circuit and a switching circuit, the problem of adjustment of the signal acquisition circuit in the prior art is solved, and efficient acquisition and processing of analog current signals and digital signals is realized, and the reliability and accuracy of the system are improved.
Patent Information
- Application Number
- CN202411363353.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-27
- Publication Date
- 2025-04-18
AI Technical Summary
In the prior art, the signal acquisition circuit needs to be adjusted when measuring analog current signals and digital signals, resulting in increased system complexity and reduced reliability.
A signal acquisition circuit is designed, including a controller, an analog-to-digital converter, a HART modem, a filter circuit and a switching circuit, which can simultaneously receive analog signals from ordinary sensors and HART signals from sensors with HART communication functions, and convert and filter signals through HART modem and filter circuit.
It realizes the acquisition and processing of different types of signals, simplifies the design of signal acquisition circuit, reduces system complexity, and improves the accuracy and stability of signal acquisition.
Smart Images
Figure CN119845313A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the field of analog quantity acquisition, and in particular to a signal acquisition circuit, an IO card, and a distributed control system. Background Art
[0002] In industrial environments, various non-electrical signals measured by sensors (such as temperature, pressure, flow, etc.) usually need to be converted into standard analog electrical signals so that they can be transmitted to local systems for processing or sent to remote systems. This is because electrical signals have the advantages of fast transmission speed and easy processing. However, during long-distance transmission, voltage signals are susceptible to various interferences, which affect the accuracy and stability of the signal, such as voltage drops caused by electromagnetic interference and line resistance. Since there is resistance on the wire, if information is transmitted using voltage signals, certain errors and interference will be generated on the wire. In contrast, current signals have better anti-interference ability and stability during transmission. Therefore, when transmitting over long distances, current signals are usually used to represent the measured parameters, such as temperature and pressure, by the values between the currents.
[0003] Among them, the 4-20mA standard analog current signal is the most widely used current signal in industry. There are specific reasons for choosing this signal range:
[0004] First, 4mA represents the zero point, that is, the output when the sensor does not detect any signal. This can avoid misjudgment caused by zero current when the signal line is disconnected or the sensor fails; 20mA represents the full scale, that is, the output corresponding to the maximum signal detected by the sensor, which can cover the needs of most industrial applications.
[0005] Second, the 4-20mA signal is a constant current source signal. The current size will not change due to changes in line resistance during transmission, so it has good anti-interference ability and stability.
[0006] Nowadays, with the development of intelligent technology in industrial production, higher requirements are placed on the measurement system. Digital signals are gradually being applied and promoted in long-distance information. At present, in industrial production, 4-20mA analog current signals and digital signals coexist in long-distance information transmission, and the original signal acquisition circuit cannot achieve this. This requires the measurement system to adjust the signal acquisition circuit online when achieving the purpose of measurement. Summary of the invention
[0007] The technical problem to be solved by the present disclosure is to overcome the defect in the prior art that the signal acquisition circuit needs to be adjusted when measuring analog current signals and digital signals, and to provide a signal acquisition circuit, an IO card and a distributed control system.
[0008] The present invention solves the above technical problems through the following technical solutions:
[0009] In a first aspect, a signal acquisition circuit is provided, the signal acquisition circuit comprising a controller, an analog-to-digital converter, a HART modem, a filtering circuit and a switching circuit;
[0010] The output end of the analog-to-digital converter is connected to the input end of the controller, and the input end of the analog-to-digital converter is connected to one end of the filter circuit;
[0011] The other end of the filter circuit is used to connect to the output end of the sensor, and the sensor is the first sensor or the second sensor; the filter circuit is used to filter the HART signal output by the second sensor or to convert the analog current signal output by the first sensor into an analog voltage signal and transmit it to the analog-to-digital converter; wherein the second sensor is a sensor with a HART communication function;
[0012] One end of the HART modem is connected to the controller, the other end of the HART modem is connected to one end of the switch circuit, and the other end of the switch circuit is connected to the other end of the filter circuit.
[0013] Optionally, the switch circuit includes a plurality of switches, the switch circuit is electrically connected to the controller, and the switches, the sensors and the filter circuits correspond to each other one by one; different filter circuits are connected to the controller via different analog channels in the analog-to-digital converter;
[0014] One end of each of the multiple switches is connected to one end of the HART modem, and the other ends of the multiple switches are respectively connected to the other end of the corresponding sensor and the corresponding filter circuit;
[0015] The controller is used to control the on and off of the switch.
[0016] Optionally, the signal acquisition circuit further includes a power supply,
[0017] The positive electrode of the second sensor is connected to the positive electrode of the power supply, the negative electrode of the second sensor is connected to the positive electrode of the corresponding analog channel through the filter circuit, and the negative electrode of the power supply and the negative electrode of the corresponding analog channel are both grounded.
[0018] Optionally, the second sensor comprises a power supply,
[0019] The positive electrode of the second sensor is connected to the positive electrode of the corresponding analog channel through the filter circuit, and the negative electrode of the second sensor is connected to the negative electrode of the corresponding analog channel through the filter circuit.
[0020] Optionally, the signal acquisition circuit further includes a first isolation circuit, which is connected in series between the HART modem and the controller.
[0021] Optionally, the signal acquisition circuit further includes a second isolation circuit; the second isolation circuit is connected in series between the analog-to-digital converter and the controller.
[0022] Optionally, the controller includes an FPGA chip and an MCU chip, and the FPGA chip is connected to the analog-to-digital converter, the HART modem and the MCU chip respectively;
[0023] The FPGA chip is used to transmit the first digital signal and / or the second digital signal to the MCU chip;
[0024] The first digital signal is a digital signal obtained by converting the analog signal output by the first sensor through the analog-to-digital converter, and the second digital signal is a digital signal obtained by demodulating the HART signal through the HART modem.
[0025] Optionally, the MCU chip is used to send instructions to the second sensor through the FPGA chip and the HART modem.
[0026] In a second aspect, an IO card is provided, wherein the IO card comprises the signal acquisition circuit as described in the first aspect.
[0027] In a third aspect, a distributed control system is provided, the distributed control system comprising a sensor and the signal acquisition circuit as described in the first aspect;
[0028] The other end of the filter circuit in the signal acquisition circuit is connected to the output end of the sensor.
[0029] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present disclosure.
[0030] The positive and progressive effects of the present disclosure are: the input end of the controller is connected through the output end of the analog-to-digital converter, and the input end of the analog-to-digital converter is connected to one end of the filter circuit; the other end of the filter circuit is used to connect the output end of the first sensor or the second sensor, and the filter circuit is used to filter the HART signal output by the second sensor and to convert the analog current signal output by the first sensor into an analog voltage signal and transmit it to the analog-to-digital converter; wherein the second sensor is a sensor with a HART communication function; one end of the HART modem is connected to the controller, the other end of the HART modem is connected to one end of the switch circuit, and the other end of the switch circuit is connected to the other end of the filter circuit; therefore, the signal acquisition circuit can receive both the analog signal of the ordinary sensor, i.e., the first sensor, and the HART signal of the sensor with a HART communication function, i.e., the second sensor, thereby meeting the requirements of connecting different devices; at the same time, the connection of the second sensor uses the analog channel of the original analog-to-digital converter, so it is only necessary to add a HART modem, a switch circuit and a filter circuit to the original circuit, and there is no need to change the original circuit. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 A schematic diagram of a signal acquisition circuit provided in Embodiment 1 of the present disclosure;
[0032] Figure 2 A schematic diagram of a filter circuit provided in Embodiment 1 of the present disclosure;
[0033] Figure 3 A schematic diagram of another signal acquisition circuit provided in Embodiment 1 of the present disclosure;
[0034] Figure 4 A schematic diagram of another signal acquisition circuit provided in Embodiment 1 of the present disclosure;
[0035] Figure 5 A schematic diagram of another signal acquisition circuit provided in Embodiment 1 of the present disclosure;
[0036] Figure 6 A schematic diagram of another signal acquisition circuit provided in Embodiment 1 of the present disclosure;
[0037] Figure 7 A schematic diagram of another signal acquisition circuit provided in Embodiment 1 of the present disclosure;
[0038] Figure 8 A schematic diagram of a protection circuit provided in Embodiment 1 of the present disclosure;
[0039] Fig. 9 A schematic diagram of a distributed control system provided in Example 3 of the present disclosure. DETAILED DESCRIPTION
[0040] The present disclosure is further described below by way of examples, but the present disclosure is not limited to the scope of the examples.
[0041] Prefixes such as "first" and "second" are used in the embodiments of the present disclosure only to distinguish different description objects, and have no limiting effect on the position, order, priority, quantity or content of the described objects. The use of prefixes such as ordinal numbers to distinguish description objects in the embodiments of the present disclosure does not constitute a limitation on the described objects. For the statement of the described objects, please refer to the description in the context of the claims or embodiments, and no unnecessary limitation should be constituted due to the use of such prefixes. In addition, in the description of the present embodiment, unless otherwise specified, the meaning of "plurality" is two or more.
[0042] Example 1
[0043] Figure 1 This is a schematic diagram of a signal acquisition circuit provided in this embodiment. The signal acquisition circuit 100 includes a controller 101, an analog-to-digital converter 102, a HART modem 103, a filter circuit 104 and a switch circuit 105.
[0044] The output end of the analog-to-digital converter 102 is connected to the input end of the controller 101, and the input end of the analog-to-digital converter 102 is connected to one end of the filter circuit 104; the other end of the filter circuit 104 is used to connect to the output end of the sensor 106, and the sensor is a first sensor or a second sensor; the filter circuit 104 is used to filter the HART signal output by the second sensor or to convert the analog current signal output by the first sensor into an analog voltage signal and transmit it to the analog-to-digital converter; wherein the second sensor is a sensor with a HART communication function; one end of the HART modem 103 is connected to the controller 101, and the other end of the HART modem 103 is connected to one end of the switch circuit 105, and the other end of the switch circuit 105 is connected to the other end of the filter circuit 104.
[0045] In a specific example, the analog-to-digital converter can use SPI (Serial Peripheral Interface) or IIC (Inter-Integrated Circuit, also known as I2C) signals to exchange data with the controller and the sensor.
[0046] In this embodiment, when the other end of the filter circuit is used to connect to the output end of the first sensor, the switch circuit is controlled to be disconnected, and the first sensor can convert various non-electrical signals (such as temperature, pressure, flow, etc.) measured into 4-20mA analog current signals, and the analog current signal is converted into an analog voltage signal through the filter circuit and transmitted to the analog-to-digital converter. The analog-to-digital converter can convert the analog voltage signal into a digital signal and transmit it to the controller.
[0047] The second sensor is a sensor with HART communication function, such as temperature sensor, pressure transmitter, flow meter, etc. with HART communication function. HART (Highway Addressable Remote Transducer) protocol is a two-way communication protocol that can realize digital signal communication on the existing analog signal transmission line. It realizes the transition between analog system and digital system by superimposing digital signal on 4-20mA analog signal. HART protocol supports both analog (4-20mA) and digital communication on the same pair of wires, ensuring compatibility with existing analog systems. HART protocol adopts half-duplex communication mode, based on FSK (frequency shift keying) technology of Bell 202 standard. Among them, FSK technology uses two sine waves of different frequencies (1200Hz and 2200Hz) to represent logic "0" and "1" respectively. The average value of these frequency signals is 0, so these frequency signals will not interfere with the transmission of 4-20mA analog signals. The HART protocol is widely used in the field of industrial automation, especially in process control systems, for communication between intelligent field instruments (such as pressure, liquid level, temperature, and flow transmitters) and control room equipment.
[0048] In this embodiment, when the other end of the filter circuit is used to connect to the output end of the second sensor, the switch circuit is controlled to be turned on, and the HART modem is configured to receive the digital signal instruction sent by the controller through UART (Universal Asynchronous Receiver / Transmitter) communication, and modulate the digital signal instruction sent by the controller, convert it into an analog signal and send it to the second sensor. The digital signal instruction sent by the controller is used to control different parameters of the second sensor, such as the measurement range, alarm threshold, etc. At the same time, the HART modem can convert the HART signal sent back by the second sensor into a digital signal and feed it back to the controller.
[0049] In a specific example, the HART modem can use the SD2057 chip, which integrates all necessary filtering, signal detection, modulation, demodulation, and HART signal waveform shaping functions, so only a small number of peripheral passive components are needed to meet the functional requirements of the HART physical layer specification. The HART modem can filter out unnecessary signals such as high frequency and low frequency, and improve the accuracy of signal acquisition.
[0050] In a specific implementation, in order to further improve the acquisition accuracy of the signal acquisition circuit, a filter circuit may be provided between the switch circuit and the HART modem to filter out unnecessary noise signals such as high frequency and low frequency.
[0051] In this embodiment, the sensor is connected to the analog-to-digital converter via a filter circuit, and the filter circuit may be an RC filter circuit, such as Figure 2 As shown, the filter circuit 104 includes a first capacitor 41, a second capacitor 42 and a resistor 43. One end of the first capacitor 41 is connected to one end of the resistor 43, and the other end of the first capacitor 41 is grounded; one end of the second capacitor 42 is connected to the other end of the resistor 43, and the other end of the second capacitor 42 is grounded. In the case where the sensor is the first sensor, the resistor 43 is used to convert the analog current signal output by the first sensor into an analog voltage signal that can be collected by the digital-to-analog converter. In the case where the sensor is the second sensor, the principle of capacitor blocking alternating current and passing direct current in the RC filter circuit is used to filter out the alternating current signal in the HART signal, so that the HART signal cannot be transmitted through the analog-to-digital converter.
[0052] In this embodiment, the signal acquisition circuit can receive both analog signals of common sensors and HART signals of sensors with HART communication function, thus realizing the need to connect different devices, meeting the needs of on-site intelligent devices and supporting traditional instruments and equipment. At the same time, the connection of the second sensor uses the analog channel of the original analog-to-digital converter, so it is only necessary to add a HART modem and a filter circuit to the original circuit without changing the original circuit.
[0053] In an optional embodiment, Figure 3 As shown, the switch circuit 105 includes a plurality of switches (not shown in the figure), the switch circuit is electrically connected to the controller, and the switches, the sensors and the filter circuits correspond to each other one by one; different filter circuits are connected to the controller through different analog channels in the analog-to-digital converter; one end of the plurality of switches is connected to one end of the HART modem, and the other ends of the plurality of switches are respectively connected to the corresponding sensors and the other ends of the corresponding filter circuits; the controller is used to control the on and off of the switches.
[0054] In this embodiment, the on and off of each switch in the switch circuit is controlled by a controller to control the input and output of the analog current signal of the first sensor and the HART signal of the second sensor.
[0055] In a specific embodiment, the analog-to-digital converter has eight analog channels and can be connected to eight sensors, wherein the eight sensors can all be second sensors to achieve the transmission of HART signals of eight sensors with HART communication function. For example, the analog-to-digital converter can use the power supply ADC chip SGM58200, and the I2C interface of SGM58200 allows communication through two lines (SDA and SCL), supporting multiple devices to share the same bus. The device also has a programmable digital comparator that can be set to a traditional comparator or a window comparator mode to trigger an alarm within a specific threshold range.
[0056] In a specific example, the analog-to-digital converter is a 24-bit analog-to-digital converter. When the sensor is a first sensor, the analog-to-digital converter collects the analog voltage signal after passing through the filtering circuit and converts the analog voltage signal into an IIC signal to transmit to the controller.
[0057] In an optional embodiment, Figure 4 As shown, the signal acquisition circuit also includes a power supply 108, the positive electrode of the second sensor 107 is connected to the positive electrode of the power supply 108, the negative electrode of the second sensor 107 is connected to the positive electrode of the corresponding analog channel through the filter circuit 104, and the negative electrode of the power supply and the negative electrode of the corresponding analog channel are both grounded. In this embodiment, the power supply to the second sensor can be realized by external power supply.
[0058] In an optional embodiment, Figure 5 As shown, the second sensor 107 includes a power supply (not shown in the figure), the positive electrode of the second sensor is connected to the positive electrode of the corresponding analog channel through the filter circuit 104, and the negative electrode of the second sensor is connected to the negative electrode of the corresponding analog channel through the filter circuit. In this embodiment, the second sensor can also be powered by an internal power supply.
[0059] In an optional embodiment, Figure 6 As shown, the signal acquisition circuit further includes a first isolation circuit 109, which is connected in series between the HART modem and the controller.
[0060] In this embodiment, the first isolation circuit may include a photoelectric isolator. After the HART modem converts the HART signal into a digital signal, the signal is fed back to the controller through the photoelectric isolator. The photoelectric isolator can prevent problems such as power reverse and ground short circuit, thereby improving the safety and reliability of the entire circuit; since the photoelectric isolator uses optical isolation to transmit signals and does not require physical contact, it can also avoid damage to the device caused by noise, looseness, oxidation and other factors caused by contact; the photoelectric isolator also has good electrical insulation and anti-interference capabilities, and has strong common mode suppression capabilities.
[0061] In an optional embodiment, Figure 6 As shown, the signal acquisition circuit also includes a second isolation circuit 110; the second isolation circuit is connected in series between the analog-to-digital converter and the controller. In this embodiment, the second isolation circuit may include a photoelectric isolator, and after the analog-to-digital converter converts the analog signal output by the first sensor into a digital signal, the signal is fed back to the controller through the photoelectric isolator.
[0062] In an optional embodiment, Figure 7 As shown, the controller 101 includes an FPGA chip 21 and an MCU chip 22, and the FPGA chip is respectively connected to the analog-to-digital converter, the HART modem and the MCU chip; the FPGA chip is used to transmit a first digital signal and / or a second digital signal to the MCU chip; the first digital signal is a digital signal after the analog signal output by the first sensor is converted by the analog-to-digital converter, and the second digital signal is a digital signal after the HART signal is demodulated by the HART modem.
[0063] In this embodiment, the FPGA chip in the signal acquisition circuit can transmit the first digital signal and / or the second digital signal to the MCU chip. Therefore, the signal acquisition circuit can realize the function of receiving both the analog signal of the ordinary sensor and the HART signal of the sensor with HART communication function; that is, it realizes the demand of connecting different devices, meets the needs of on-site intelligent devices, and supports traditional instruments and equipment.
[0064] In an optional implementation, the MCU chip is used to send instructions to the second sensor through the FPGA chip and the HART modem. The instruction is a digital signal, and the FPGA chip processes the digital signal and sends it to the HART modem, and the HART modem converts the processed digital signal of the FPGA chip into an analog signal and sends it to the second sensor.
[0065] In an optional embodiment, the signal acquisition circuit also includes a protection circuit, which corresponds to the analog-to-digital converter. The protection circuit can prevent damage caused by voltage spikes, electrostatic discharge, power supply fluctuations, or incorrect wiring. According to the data sheet and application environment of the analog-to-digital converter, determine the required type of protection, such as overvoltage protection, overcurrent protection, electrostatic discharge protection, etc., to ensure that the protection circuit can respond quickly and limit or eliminate damage to the analog-to-digital converter under abnormal conditions. In this embodiment, the protection circuit can be connected to the power line and signal line of the analog-to-digital converter. For example, a TVS diode can be added to the power input of the analog-to-digital converter to prevent voltage spikes.
[0066] In a specific example, the signal acquisition circuit further includes a protection circuit 111, Figure 8 Schematic diagram of a protection circuit, the protection circuit 111 includes a self-recovery fuse 51, a TVS diode 52, a pull-up resistor 53 and a pull-down resistor 54, and the connection relationship is as follows Figure 8 Specifically, the resettable fuse can realize the protection of channel misconnection; the TVS diode can realize surge protection; the pull-up resistor and the pull-down resistor are used to increase the voltage difference. When the input signal is approximately equal to 0mA, it can be determined whether it is a disconnection situation.
[0067] Example 2
[0068] This embodiment provides an IO card, and the IO card includes the signal acquisition circuit as described in Embodiment 1.
[0069] The IO card can receive both analog signals from common sensors and HART signals from sensors with HART communication functions, thus meeting the need to connect different devices, satisfying the needs of on-site intelligent devices and supporting traditional instruments and equipment. At the same time, the connection of the second sensor uses the analog channel of the original analog-to-digital converter, so only the HART modem and filter circuit need to be added to the original circuit, without changing the original circuit, thus reducing the complexity of the circuit and software and improving the circuit reliability.
[0070] Example 3
[0071] This embodiment provides a distributed control system, such as Figure 1 As shown, the distributed control system includes a sensor 106 and a signal acquisition circuit 100 as described in Example 1; the other end of the filter circuit in the signal acquisition circuit is connected to the output end of the sensor.
[0072] A distributed control system is a computer control system used for industrial process control. It distributes control functions to multiple control nodes instead of concentrating them in a central control room. Distributed control systems connect various control nodes through a communication network to achieve real-time exchange and processing of data. Distributed control systems are widely used in process control in industries such as petroleum, chemical, electric power, water treatment, and food processing. It improves production efficiency, safety, and reliability by providing highly automated and optimized control strategies.
[0073] In an optional embodiment, Fig. 9 As shown, the distributed control system also includes a host computer 30. In this embodiment, the controller sends feedback information to the host computer after receiving it, and the host computer sends an instruction to select the channel data type to the controller, that is, it supports 4-20mA analog signals, HART signals, and supports input data acquisition and output data control.
[0074] In a specific example, the host computer also provides a graphical user interface that allows users to monitor the status of the distributed control system, operate equipment, and view reports. Specifically, the host computer can monitor the status of the distributed control system and trigger alarms and event responses, such as fault detection and exception handling. Users can complete the identification and analysis of data types by configuring the software on the host computer, which greatly reduces the difficulty of manual identification and improves the efficiency of the distributed control system.
[0075] Although the specific embodiments of the present disclosure are described above, those skilled in the art should understand that this is only an example, and the protection scope of the present disclosure is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present disclosure, but these changes and modifications all fall within the protection scope of the present disclosure.
Claims
1. A signal acquisition circuit, characterized in that: The signal acquisition circuit includes a controller, an analog-to-digital converter, a HART modem, a filtering circuit and a switching circuit; The output end of the analog-to-digital converter is connected to the input end of the controller, and the input end of the analog-to-digital converter is connected to one end of the filter circuit; The other end of the filter circuit is used to connect to the output end of the sensor, and the sensor is the first sensor or the second sensor; the filter circuit is used to filter the HART signal output by the second sensor or to convert the analog current signal output by the first sensor into an analog voltage signal and transmit it to the analog-to-digital converter; wherein the second sensor is a sensor with a HART communication function; One end of the HART modem is connected to the controller, the other end of the HART modem is connected to one end of the switch circuit, and the other end of the switch circuit is connected to the other end of the filter circuit.
2. The signal acquisition circuit according to claim 1, characterized in that: The switch circuit includes a plurality of switches, the switch circuit is electrically connected to the controller, and the switches, the sensors and the filter circuits correspond to each other one by one; different filter circuits are connected to the controller via different analog channels in the analog-to-digital converter; One end of each of the multiple switches is connected to one end of the HART modem, and the other ends of the multiple switches are respectively connected to the other end of the corresponding sensor and the corresponding filter circuit; The controller is used to control the on and off of the switch.
3. The signal acquisition circuit according to claim 1, characterized in that: The signal acquisition circuit also includes a power supply, The positive electrode of the second sensor is connected to the positive electrode of the power supply, the negative electrode of the second sensor is connected to the positive electrode of the corresponding analog channel through the filter circuit, and the negative electrode of the power supply and the negative electrode of the corresponding analog channel are both grounded.
4. The signal acquisition circuit according to claim 1, characterized in that: The second sensor includes a power source, The positive electrode of the second sensor is connected to the positive electrode of the corresponding analog channel through the filter circuit, and the negative electrode of the second sensor is connected to the negative electrode of the corresponding analog channel through the filter circuit.
5. The signal acquisition circuit according to claim 4, characterized in that: The signal acquisition circuit also includes a first isolation circuit, which is connected in series between the HART modem and the controller.
6. The signal acquisition circuit according to claim 5, characterized in that: The signal acquisition circuit also includes a second isolation circuit; the second isolation circuit is connected in series between the analog-to-digital converter and the controller.
7. The signal acquisition circuit according to claim 6, characterized in that: The controller includes an FPGA chip and an MCU chip, and the FPGA chip is connected to the analog-to-digital converter, the HART modem and the MCU chip respectively; The FPGA chip is used to transmit the first digital signal and / or the second digital signal to the MCU chip; The first digital signal is a digital signal obtained by converting the analog signal output by the first sensor through the analog-to-digital converter, and the second digital signal is a digital signal obtained by demodulating the HART signal through the HART modem.
8. The signal acquisition circuit according to claim 7, characterized in that: The MCU chip is used to send instructions to the second sensor through the FPGA chip and the HART modem.
9. An IO card, characterized in that: The IO card comprises the signal acquisition circuit as described in any one of claims 1-8.
10. A distributed control system, characterized in that: The distributed control system comprises a sensor and a signal acquisition circuit as claimed in any one of claims 1 to 8; The other end of the filter circuit in the signal acquisition circuit is connected to the output end of the sensor.