A Thermocouple Analog Input Module Based on SPARC Microcontroller

Abstract

The present invention provides a thermocouple analog input module based on a SPARC architecture microcontroller, the module comprising: an analog-to-digital conversion circuit, an optocoupler isolator, a microcontroller, a memory, and a bus control circuit. The analog-to-digital conversion circuit is used to convert the analog quantity of the electromotive force generated by the thermocouple due to the thermoelectric effect into a digital code value; the optocoupler isolator realizes isolation between the analog-to-digital conversion circuit and the microcontroller; the microcontroller is used to convert the digital code value generated by the analog-to-digital converter into the thermocouple electromotive force, and convert the thermocouple electromotive force into the corresponding temperature data according to the thermocouple graduation table or the electromotive force-temperature relationship calculation formula; the memory is used to store information such as the thermocouple graduation table or the electromotive force-temperature relationship calculation formula and channel calibration data; the bus control circuit is used to output the converted temperature data through the bus. The present invention can support a variety of cold end compensation temperature acquisition methods, which is convenient for selecting appropriate cold end compensation according to the application scenario to meet the actual temperature measurement needs.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial process control, and in particular relates to a thermocouple type analog quantity input module. Background Art

[0002] Thermocouple, as part of the circuit for measuring temperature using the thermoelectric effect, is a pair of conductors of different materials connected at one end. The end of the thermocouple where the conductors of different materials are connected is the measuring end, which is used to sense the measured temperature. The other end of the thermocouple is the reference end, which is connected to the measuring device or connected to the measuring device through a compensation wire. The compensation wire is a pair of wires with an insulating layer. The compensation wire is divided into two types: extended type and compensation type. The nominal chemical composition and nominal value of thermoelectric electromotive force of the extended type compensation wire are the same as those of the matching thermocouple. The nominal chemical composition of the compensation type compensation wire is different from that of the matching thermocouple, but its nominal value of thermoelectric electromotive force is the same as that of the matching thermocouple within a certain temperature range. When the compensation wire is correctly connected to the matching thermocouple, the compensation wire moves the reference end of the thermocouple to the output end of the pair of wires. The corresponding relationship between the thermocouple electromotive force and the measured temperature is expressed by the graduation table of the thermocouple or the polynomial derived from the graduation table. The reference end temperature of the thermocouple scale is 0°C. In order to reduce the influence of the temperature of the thermocouple reference end or the output end of the compensation wire on the measurement result during actual measurement, the measuring device needs to compensate the reference end of the thermocouple or the output end of the compensation wire relative to 0°C. Because the reference end is called the cold end relative to the measuring end, it is also called cold end compensation. The thermocouple electromotive force after cold end compensation can be converted into corresponding temperature data according to the corresponding type of thermocouple scale or electromotive force-temperature relationship polynomial, so that the thermocouple realizes the function of temperature sensor.

[0003] Conventional thermocouple analog input modules perform cold-end compensation in the following way: the cold-end compensation temperature sensor is fixed inside or outside the module, and cold-end compensation is performed by a single fixed-position temperature sensor. The limitation of this approach is that when the cold-end compensation temperature sensor is not close to the output end of the thermocouple compensation wire or the cold-end compensation sensor is interfered by an unexpected heat source, the cold-end compensation cannot effectively reduce the impact of the deviation of the thermocouple reference end or the compensation wire output end relative to 0°C on the measurement result. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a thermocouple analog input module based on a SPARC microcontroller.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] A thermocouple analog input module based on a SPARC architecture microcontroller includes: an analog-to-digital conversion circuit, an optical coupler isolator, a microcontroller, a memory, and a bus control circuit.

[0007] The analog-to-digital conversion circuit converts the analog quantity of the electromotive force generated by the thermocouple due to the thermoelectric effect into a digital quantity code value;

[0008] The optical coupler isolator realizes isolation between the analog-to-digital conversion circuit and the microcontroller;

[0009] The microcontroller converts the digital code value generated by the analog-to-digital converter into the thermocouple electromotive force, and converts the thermocouple electromotive force into the corresponding temperature data according to the thermocouple graduation table or the electromotive force-temperature relationship polynomial;

[0010] The memory is used to store information such as a thermocouple indexing table or an electromotive force-temperature relationship polynomial and channel calibration data;

[0011] The bus control circuit outputs the converted temperature data through the bus;

[0012] Furthermore, the analog-to-digital conversion circuit includes cold-end compensation, a signal conditioning circuit, an amplifier, a filter, and an analog-to-digital converter.

[0013] Furthermore, the cold end compensation can be selected from a variety of methods for obtaining the cold end temperature, including temperature measurement inside the module, temperature measurement outside the module, and setting input;

[0014] Furthermore, the analog-to-digital converter adopts a 24-bit delta-sigma ADC;

[0015] Furthermore, the microcontroller adopts a 32-bit SPARC V8 processor based on the SPARC architecture;

[0016] Furthermore, the memory is stored in FLASH.

[0017] Furthermore, the bus control circuit includes a bus controller and an EEPROM;

[0018] Furthermore, the bus controller adopts ET1200 EtherCAT bus controller;

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] Cold-end compensation can be selected from a variety of ways to obtain the cold-end temperature, including temperature measurement inside the module, temperature measurement outside the module, and setting input. This can effectively reduce the impact of the cold-end compensation temperature sensor not being close to the output end of the thermocouple compensation wire or the cold-end compensation sensor being disturbed by unexpected heat sources on the measurement results. The module supports a variety of cold-end compensation temperature acquisition methods, making it easy to select appropriate cold-end compensation according to the application scenario to meet actual temperature measurement needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The block diagram of the thermocouple analog input module based on SPARC microcontroller is shown below:

[0022] Figure 2 This is a detailed block diagram of the thermocouple analog input module based on the SPARC microcontroller. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] A thermocouple analog input module based on SPARC microcontroller, its composition block diagram is as follows Figure 1 As shown, it includes: an analog-to-digital conversion circuit, an optocoupler isolator, a microcontroller, a memory, and a bus control circuit.

[0025] Thermocouple analog input module converts the thermocouple electromotive force after cold-end compensation into temperature data, and realizes the temperature measurement of the environment at the end where the thermocouple is measured. The detailed block diagram is as follows: Figure 2 As shown, including:

[0026] The analog-to-digital conversion circuit converts the analog quantity of the electromotive force generated by the thermocouple due to the thermoelectric effect into a digital code value.

[0027] The analog-to-digital conversion circuit includes cold-end compensation, signal conditioning circuit, amplifier, filter, and analog-to-digital converter.

[0028] Signal conditioning circuits, amplifiers, and filters are used to reduce the impact of noise interference on measurement results. After the thermocouple electromotive force passes through the signal conditioning circuit, amplifier, and filter, it forms an analog signal suitable for input into the analog converter.

[0029] The analog-to-digital conversion circuit includes an analog-to-digital converter, which uses a 24-bit Δ-Σ ADC to achieve high-resolution analog-to-digital conversion of the thermocouple electromotive force. The thermocouple electromotive force is converted into a digital code value by the analog-to-digital converter, and the digital code value is mapped to the thermocouple electromotive force. The digital code value is transmitted from the analog-to-digital converter to the microcontroller through the SPI interface.

[0030] The cold end compensation can be selected from a variety of methods for obtaining the cold end temperature, such as temperature measurement inside the module, temperature measurement outside the module, and setting input. When the method of obtaining the cold end temperature by temperature measurement inside the module is adopted, the cold end compensation temperature sensor is located at the thermocouple reference end or the compensation wire output end of the thermocouple electromotive force analog input channel. When the cold end temperature is obtained by temperature measurement outside the module, the cold end compensation temperature sensor is located at the thermocouple reference end or the compensation wire output end. The cold end temperature obtained by the cold end compensation is transmitted to the microcontroller through the SPI interface via the analog-to-digital converter.

[0031] Optocoupler isolators are used to isolate analog-to-digital conversion circuits and microcontrollers, and are used to improve the ability of thermocouple analog input modules to resist electromagnetic interference.

[0032] The microcontroller adopts a 32-bit SPARC V8 processor based on the SPARC architecture. The microcontroller converts the digital code value into the thermocouple electromotive force millivolt value according to the mapping relationship between the digital code value and the thermocouple electromotive force and the channel calibration data. According to the corresponding thermocouple graduation table or the temperature-electromotive force relationship polynomial, the cold end millivolt value corresponding to the cold end temperature is obtained. The thermocouple electromotive force millivolt value is added to the cold end millivolt value to obtain the thermocouple measuring end millivolt value. According to the corresponding thermocouple graduation table or the electromotive force-temperature relationship polynomial, the corresponding temperature data of the thermocouple measuring end is obtained. In this way, the temperature measurement of the environment where the thermocouple measuring end is located is realized. The microcontroller is connected to the bus controller through the SPI interface to transmit the converted temperature data to the bus controller.

[0033] The FLASH memory is connected to the microcontroller via an SPI interface and stores the graduation table or electromotive force-temperature relationship polynomial of all types of thermocouples supported by the thermocouple analog input module.

[0034] The bus control circuit outputs the converted temperature data through the bus. The bus control circuit includes a bus controller and an EEPROM. The bus controller uses an ET1200 EtherCAT bus controller. The EEPROM is connected to the I 2 The C interface is connected to the bus controller, and the EEPROM is used to store the working mode configuration information of the bus controller. The bus controller uses the Ebus communication interface to output the converted temperature data through the EtherCAT bus.

[0035] The present invention is not limited to the above-mentioned embodiments, and any obvious improvements or changes to the above-mentioned embodiments made by those skilled in the art will not exceed the concept of the present invention and the protection scope of the appended claims.

Claims

1. A thermocouple analog input module based on a SPARC architecture microcontroller, characterized in that it includes: Analog-to-digital conversion circuit, optocoupler isolator, microcontroller, memory, bus control circuit; wherein, The analog-to-digital conversion circuit converts the analog quantity of the electromotive force generated by the thermocouple due to the thermoelectric effect into a digital quantity code value; The optical coupler isolator realizes isolation between the analog-to-digital conversion circuit and the microcontroller; The microcontroller converts the digital code value generated by the analog-to-digital converter into the thermocouple electromotive force, and converts the thermocouple electromotive force into the corresponding temperature data according to the thermocouple graduation table or the electromotive force-temperature relationship polynomial; The memory is used to store information such as a thermocouple indexing table or an electromotive force-temperature relationship polynomial and channel calibration data; The bus control circuit outputs the converted temperature data through the bus; The analog-to-digital conversion circuit includes cold junction compensation; The cold end compensation is selected from a plurality of methods of obtaining the cold end temperature, including temperature measurement inside the module, temperature measurement outside the module, and setting input; When the cold-end temperature is obtained by measuring the temperature inside the module, the cold-end compensation temperature sensor is located at the thermocouple reference end or the compensation wire output end where the thermocouple electromotive force analog input channel is connected; when the cold-end temperature is obtained by measuring the temperature outside the module, the cold-end compensation temperature sensor is located at the thermocouple reference end or the compensation wire output end.

2. The thermocouple analog input module based on SPARC architecture microcontroller according to claim 1, characterized in that: The analog-to-digital conversion circuit also includes a signal conditioning circuit, an amplifier, a filter, and an analog-to-digital converter.

3. The thermocouple analog input module based on SPARC architecture microcontroller according to claim 1, characterized in that: The analog-to-digital converter adopts a 24-bit delta-sigma ADC.

4. The thermocouple analog input module based on SPARC architecture microcontroller according to claim 1, characterized in that: The microcontroller adopts a 32-bit SPARCV8 processor based on the SPARC architecture.

5. The thermocouple analog input module based on SPARC architecture microcontroller according to claim 1, characterized in that: The memory adopts FLASH storage.

6. The thermocouple analog input module based on SPARC architecture microcontroller according to claim 1, characterized in that: The bus control circuit includes a bus controller and an EEPROM.

7. The thermocouple analog input module based on SPARC architecture microcontroller according to claim 6, characterized in that: The bus controller adopts ET1200 EtherCAT bus controller.

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