Multi-channel thermocouple signal acquisition system

Abstract

The utility model discloses a multichannel thermocouple signal acquisition system, and mainly solves the technical problems of high cost and complex data summarization processing of an existing temperature measurement system. The number of input channels of the multi-channel analog switch module is not less than the number of temperature measurement points to be measured, and the thermocouples are electrically connected with the corresponding input channels of the multi-channel analog switch module correspondingly through amplification compensation modules. The analog-to-digital conversion module, the signal isolation module and the controller are electrically or communicatively connected to the downstream of an output channel of the multi-channel analog switch module in sequence; and a corresponding output port of the controller is correspondingly and electrically connected with a channel selection port of the multi-channel analog switch module through the signal isolation module. The problems of multi-point temperature measurement and system expansion are solved through channel time division multiplexing, and the flexibility of the system and the special requirements of modules can be improved.

Description

Technical Field

[0001] This application relates to the field of temperature monitoring technology, specifically to a multi-channel thermocouple signal acquisition system. Background Technology

[0002] Methanol reforming for hydrogen production involves reacting methanol with water vapor in the presence of a catalyst to generate hydrogen, which is then used to power fuel cells. This technology offers advantages such as easy storage and transportation of raw materials, high system integration, and relatively high power generation efficiency, demonstrating its application potential in distributed energy and mobile power sources.

[0003] When a methanol reforming system is operating, multiple measuring points, such as the evaporator outlet, catalyst bed temperature gradient, and hot and cold ends of the heat exchanger, need to be monitored simultaneously to ensure efficient and stable system operation. Type K thermocouples, with their advantages of wide temperature range, good stability, and low cost, are widely used for temperature monitoring and control in methanol reforming hydrogen production power generation systems. However, in implementing the technical solutions in this application, the inventors discovered that existing technical solutions using PLC systems and dedicated PLC temperature measurement modules for methanol reforming system temperature measurement suffer from large system size and high cost. Furthermore, differences in module development environments and methods among different PLC manufacturers lead to poor compatibility and hinder the collection and aggregation of temperature data. On the other hand, technical solutions using microcontroller-embedded temperature measurement systems for methanol reforming system temperature measurement require multiple temperature acquisition terminals to collect temperature data from multiple points, resulting in complex communication and aggregation of data from multiple acquisition points.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the background technology of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] In view of at least one of the above technical problems, this disclosure provides a multi-channel thermocouple signal acquisition system, which mainly solves the technical problems of high cost and complex data aggregation and processing of existing temperature measurement systems.

[0006] According to one aspect of this disclosure, a multi-channel thermocouple signal acquisition system is provided, comprising a multi-channel analog switch module with an input channel number not less than the number of temperature measurement points to be measured, a plurality of thermocouples electrically connected to corresponding input channels of the multi-channel analog switch module via an amplification compensation module, an analog-to-digital converter module, a signal isolation module, and a controller sequentially electrically or communicatively connected downstream of the output channel of the multi-channel analog switch module; the corresponding output port of the controller is electrically connected to the channel selection port of the multi-channel analog switch module via the signal isolation module.

[0007] In some embodiments of this disclosure, the thermocouple and the amplification compensation module are electrically connected to an RC filter unit for suppressing radio frequency interference.

[0008] In some embodiments of this disclosure, the amplification compensation module includes a thermocouple amplifier with a bias voltage input pin and a bias reference voltage unit electrically connected to the bias voltage input pin and used for negative temperature acquisition.

[0009] In some embodiments of this disclosure, the bias reference voltage unit includes a voltage reference chip, which is used to output a bias voltage greater than the internal reference voltage of the thermocouple amplifier.

[0010] In some embodiments of this disclosure, the analog-to-digital conversion module and the signal isolation module, and the signal isolation module and the controller are respectively connected via an SPI data read bus.

[0011] In some embodiments of this disclosure, the output channel of the multi-channel analog switch is electrically connected to the input port of the analog-to-digital converter module via a low-pass filter.

[0012] In some embodiments of this disclosure, the signal isolation module includes a control signal isolation unit electrically connected between the corresponding output port of the controller and the channel selection port of the multi-channel analog switch module, and a sampling isolation unit electrically connected between the analog-to-digital conversion module and the controller.

[0013] One or more technical solutions provided in the embodiments of this application have at least one of the following technical effects or advantages: the multi-channel analog switch module can realize time-division multiplexing of multi-point thermocouple temperature measurement, thereby solving the problem of summarizing and processing multi-channel signal data when monitoring multiple points of temperature in methanol reforming. By using time-division multiplexing of multi-channel AD measurement, the number of channels can be easily expanded, and conventional microprocessors can meet the data acquisition requirements. This avoids the problems of poor adaptability caused by the need for a dedicated sampling module in traditional temperature data acquisition and high cost caused by the need to reuse multiple sets of acquisition devices when facing multi-channel data acquisition. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the principle of a multi-channel thermocouple signal acquisition system in one embodiment of this application.

[0015] Figure 2 This is a partial circuit schematic diagram of a multi-channel analog switch module in one embodiment of this application.

[0016] Figure 3 This is a partial circuit diagram of the amplification compensation module in one embodiment of this application.

[0017] Figure 4 This is a partial circuit diagram of the bias reference voltage unit in one embodiment of this application.

[0018] Figure 5 This is a partial circuit schematic diagram of an analog-to-digital conversion module in one embodiment of this application.

[0019] Figure 6 This is a partial circuit diagram of the sampling isolation unit in one embodiment of this application.

[0020] Figure 7 This is a partial circuit schematic diagram of the control signal isolation unit in one embodiment of this application.

[0021] Figure 8 This is a partial circuit schematic diagram of the isolated power supply module in another embodiment of this application. Detailed Implementation

[0022] The programs involved or relied upon in the following embodiments are all conventional or simple programs in this technical field. Those skilled in the art can make conventional choices or adaptive adjustments according to specific application scenarios.

[0023] Unless otherwise specified, all devices and other components involved in the following embodiments are commercially available products.

[0024] To better understand the technical solution of this application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] To address the technical challenges of high temperature monitoring costs and difficulties in aggregating and processing multi-channel temperature data during existing methanol reforming hydrogen production processes, this paper discloses a multi-channel thermocouple signal acquisition system. (See [link to relevant documentation]). Figure 1 It includes a multi-channel analog switch module with several input channels, wherein the number of input channels of the multi-channel analog switch module is no less than the number of temperature measurement points to be measured, thereby meeting the temperature measurement requirements at multiple points. See details... Figure 2In this embodiment, the multi-channel analog switch module includes a 16-channel analog switch chip of model CD4067BM. Its corresponding AD849X_OUT0~AD849X_OUT15 are 16 thermocouple temperature measurement signal input channels, while CD4067_COM1 is a 16-to-1 output channel of the analog switch chip. The four input channels CD4067_ADDRIN_A~CD4067_ADDRIN_D serve as channel selection control channels, i.e., channel selection ports, for the analog switch chip. The analog switch chip selects one of the 16 thermocouple temperature measurement signal input channels and connects it to the output channel according to the channel selection information input to the corresponding channel selection port. This allows for multi-channel thermocouple temperature measurement through time-division multiplexing of channels, thereby reducing the number of components and the cost of the temperature measurement and signal acquisition system. Furthermore, in Figure 2 In this configuration, the CD4067_INH1 terminal of the 16-channel analog switch chip is used to input the chip select enable signal. Therefore, by controlling the chip select enable, two multi-channel analog switch chips can be connected in parallel for expansion, improving system flexibility.

[0026] Each input channel of the multi-channel analog switch module is electrically connected to a thermocouple to measure temperature at different locations. However, through long-term practical research, the inventors discovered that the signals output by the temperature-measuring thermocouples suffer from problems such as small amplitude and susceptibility to interference and noise. This leads to a certain deviation between the final temperature acquisition data and the actual temperature value, affecting the accuracy and reliability of the measurement results. Therefore, in this embodiment, each thermocouple is electrically connected to its corresponding input channel of the multi-channel analog switch module through an amplification and compensation module. See also... Figure 1 , Figure 1 Only the thermocouples electrically connected to the CH0 input channel of the multi-channel analog switch module are shown in the image. Other thermocouples can be found in [reference needed]. Figure 1 The circuit diagram shown corresponds to the electrical connections of the other input channels of the multi-channel analog switch module, which will not be elaborated further in this example. For details, please refer to [link / reference needed]. Figure 1 A thermocouple calculates temperature by measuring the thermoelectric potential difference between the contact point (hot junction) and the reference junction (cold junction) of two different metal conductors. When the junctions of the two different metals are at different temperatures, a thermoelectric electromotive force is generated in the circuit, the magnitude of which is proportional to the temperature difference. Figure 1As shown in the figure, T0 is the hot junction of the thermocouple, and T+ and T- are the cold junctions. When the hot junction is under different temperature conditions, a corresponding electromotive force, i.e., an output voltage, will be output between the cold junctions T+ and T-. Since this output voltage is low, the cold junction of the thermocouple is electrically connected to an amplification and compensation module to amplify the signal output by the thermocouple. Simultaneously, considering that the output signal of the thermocouple is strongly correlated with the cold junction temperature, if the cold junction temperature is unstable or deviates from 0°C, it will directly lead to measurement errors. Therefore, in this embodiment, an amplification and compensation module is used to compensate for the cold junction temperature of the thermocouple.

[0027] For details, see Figure 3 In this embodiment, the amplification compensation module includes a thermocouple amplifier of model AD8495ARMZ-R7, whose AD849X_IN0_P and AD849X_IN0_N are used to electrically connect to the cold junctions T+ and T- of the thermocouple, serving as the inputs of thermocouple amplifier U1. Considering that in practice, thermocouples are deployed at different temperature measurement points, to avoid the radio frequency interference signals that may be introduced by the long leads of the thermocouples affecting the accuracy of temperature measurement, therefore, in this embodiment, see... Figure 1 An RC filter unit is installed between the cold junction (the output terminal of the thermocouple) and the thermocouple amplifier. See details below. Figure 3 The RC filter unit includes resistors R4 and R7 and capacitor C10 to filter out power frequency interference and electromagnetic noise in the circuit. Additionally, the AD8495ARMZ-R7 thermocouple amplifier used in this example integrates a temperature sensor for direct cold junction temperature monitoring and compensation. To ensure the reliability of cold junction temperature monitoring, in this embodiment, the thermocouple amplifier is positioned close to the cold junction interface of the thermocouple, thereby ensuring accurate acquisition of cold junction temperature changes for compensation and improving the effectiveness of the compensation. Figure 3 In this circuit, AD849X_OUT0 is used to output the filtered, amplified, and compensated thermocouple sensor signal. This output terminal is electrically connected to the corresponding input channel of the multi-channel analog switch chip.

[0028] Furthermore, considering the small output voltage of the thermocouple amplifier at negative temperatures, to avoid noise interference overwhelming the negative voltage signal and to facilitate sampling by the subsequent analog-to-digital conversion module, in this embodiment, the AD849X_REF0 terminal of the thermocouple amplifier is electrically connected to the bias reference voltage unit for input bias reference voltage, thereby achieving negative temperature acquisition by the thermocouple. For details, see... Figure 4The bias reference voltage unit includes a voltage reference chip of model REF3012AIDBZR. The AD849X_5V0 terminal is used to input a 5V voltage, and the AD849X_REF0 terminal is used to output a 1.25V reference voltage to the AD849X_REF0 terminal of the thermocouple amplifier. The reference voltage output by this terminal is greater than the reference voltage inside the thermocouple amplifier, thereby meeting the requirements for accurate low-temperature measurement.

[0029] See Figure 1 Downstream of the output channel of the multi-channel analog switch module are sequentially connected an analog-to-digital converter module, a signal isolation module, and a controller. The analog-to-digital converter module converts the analog signal output by the thermocouple into a digital signal that the controller can recognize and use, and the signal isolation module provides electrical isolation between the thermocouple measurement section and the controller signal processing section.

[0030] Among them, see Figure 1 The output channels of the multi-channel analog switch module are electrically connected to the corresponding inputs of the analog-to-digital converter module. Specifically, in this embodiment, see [link to relevant documentation]. Figure 5 The analog-to-digital converter module includes an ADS8320E / 2K5 analog-to-digital converter. Its CD4067_COM1 terminal corresponds to the input terminal of the analog-to-digital converter and is used for electrical connection to the output channel of the 16-channel analog switch chip in this example. See [link to relevant documentation]. Figure 5 A low-pass filter consisting of resistor R184 and capacitor C202 is installed between the output channel of the analog switch chip (CD4067_COM1 terminal) and the input port of the analog-to-digital converter to filter out input noise. Additionally, Figure 5 In this circuit, the ADC_12V0 is connected to a 12V power supply, which is regulated to 5.0V by a U52 voltage reference chip (LM4040CIN3-5.0) and used as the reference voltage for the analog-to-digital converter (ADC), connected to the VREF pin of the ADC. The analog temperature signal output from the thermocouple is processed by the ADC and converted into a corresponding digital signal, which is then output through the ADS8320_DOUT_R terminal.

[0031] To achieve electrical isolation between the analog and digital sections of a multi-channel thermocouple signal acquisition system, thereby mitigating interference between different potential domains and improving system anti-interference capabilities and security, this embodiment includes a signal isolation module comprising a sampling isolation unit and a control signal isolation unit. In this example, the sampling isolation unit is integrated into the SPI data bus communication connection between the analog-to-digital converter and the controller; see [link to details]. Figure 6The sampling isolation unit includes an isolator chip of model CA_IS3731HW. Its ADS8320_DOUT_R terminal is used to connect to the output of the analog-to-digital converter, and the ADS8320_DOUT terminal is used as the output of the isolator chip to communicate with the I / O port of the controller, thereby realizing electrical isolation between analog and digital communication.

[0032] This multi-channel thermocouple signal acquisition system uses time-division multiplexing of each temperature measurement channel to achieve multi-channel thermocouple temperature measurement. Therefore, the controller controls the conduction channels of the multi-channel analog switch module. Thus, in this example, a control signal isolation unit is set up to achieve electrical isolation between the controller output and the input of the multi-channel analog switch chip. See details... Figure 7 In this example, the control signal isolation unit includes an isolator chip of model CA_IS3760HW. The signal on its VIx side comes from the input of the controller control signal, and the signal on its VOx side is the isolated control output, which is used to electrically connect to the channel selection control pin of the 16-channel analog switch chip CD4067BM.

[0033] In this example, the controller uses a microcontroller. Additionally, in some other embodiments, the multi-channel thermocouple signal acquisition system also includes an isolation power supply module to isolate the power supply between the thermocouple analog signal processing section and the controller digital processing section. See details... Figure 8 In this example, the isolated power supply module includes an isolated power supply chip with model number URB2412S-6WR3 and a power of 6W, with an isolation voltage of 1600VDC. The DC_24V_IN terminal is connected to the system's main DC24V power supply. In addition, the inductors L1 and L2 in the isolated power supply module are used to filter out power frequency interference and noise in the power supply to improve power quality and system sampling accuracy.

[0034] Although some preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0035] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include these modifications and variations.

Claims

1. A multi-channel thermocouple signal acquisition system, characterized in that, The system includes a multi-channel analog switch module with no fewer input channels than the number of temperature measurement points to be measured; several thermocouples electrically connected to the corresponding input channels of the multi-channel analog switch module via an amplification and compensation module; an analog-to-digital converter module, a signal isolation module, and a controller that are sequentially electrically or communicatively connected downstream of the output channels of the multi-channel analog switch module; and the corresponding output port of the controller is electrically connected to the channel selection port of the multi-channel analog switch module via the signal isolation module.

2. The multi-channel thermocouple signal acquisition system according to claim 1, characterized in that, The thermocouple and the amplification compensation module are electrically connected by an RC filter unit for suppressing radio frequency interference.

3. The multi-channel thermocouple signal acquisition system according to claim 1, characterized in that, The amplification and compensation module includes a thermocouple amplifier with a bias voltage input pin and a bias reference voltage unit electrically connected to the corresponding bias voltage input pin for negative temperature acquisition.

4. The multi-channel thermocouple signal acquisition system according to claim 3, characterized in that, The bias reference voltage unit includes a voltage reference chip, which is used to output a bias voltage greater than the internal reference voltage of the thermocouple amplifier.

5. The multi-channel thermocouple signal acquisition system according to claim 1, characterized in that, The analog-to-digital conversion module and the signal isolation module, as well as the signal isolation module and the controller, are connected via an SPI data read bus.

6. The multi-channel thermocouple signal acquisition system according to claim 1, characterized in that, The output channel of the multi-channel analog switch is electrically connected to the corresponding input port of the analog-to-digital converter module through a low-pass filter.

7. The multi-channel thermocouple signal acquisition system according to claim 1, characterized in that, The signal isolation module includes a control signal isolation unit electrically connected between the corresponding output port of the controller and the channel selection port of the multi-channel analog switch module, and a sampling isolation unit electrically connected between the analog-to-digital conversion module and the controller.

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