A thermocouple exhaust temperature sensor automatic calibration system and method

Abstract

The invention discloses an automatic calibration system and method for a thermocouple exhaust temperature sensor. The automatic calibration system includes a single-chip microcomputer lower computer software, a host computer monitoring software, a thermocouple exhaust temperature sensor, a DAC controller, a communication module, a computer and a power module; the automatic calibration method includes the following steps: (1) initializing the host computer, (2) initializing the thermocouple exhaust temperature sensor, (3) initializing the DAC controller, and (4) starting calibration after the host computer sends a ready mark message. The invention shortens the calibration time, eliminates the calibration interference caused by the precision error of the thermocouple probe, realizes the calibration of the PCB board of the thermocouple sensor, improves the calibration efficiency and the accuracy of the calibration result, and solves the problems of the traditional calibration method being complicated, time-consuming and temperature unstable.

Description

Technical Field

[0001] The invention relates to a temperature sensor, and in particular to an automatic calibration system and method for a thermocouple exhaust temperature sensor. Background Art

[0002] At present, the main components of heavy-duty diesel vehicle after-treatment devices include: exhaust gas recirculation system EGR, diesel oxidation catalyst DOC, diesel particulate filter DPF, selective catalytic reduction system SCR and ammonia trap ASC.

[0003] The exhaust temperature sensor plays an important role in monitoring the intake temperature of the diesel oxidation catalyst DOC, diesel particulate filter DPF and selective catalytic reduction system SCR for the after-treatment system. Only when the exhaust temperature reaches a specific range can the conversion efficiency of the diesel oxidation catalyst DOC, diesel particulate filter DPF and selective catalytic reduction system SCR reach the highest level. The increase in the number of exhaust temperature sensors and the precise measurement of temperature have put forward new requirements for the calibration of the sensors.

[0004] The commonly used calibration method for temperature sensors is to place the temperature sensor to be calibrated and a calibrated temperature sensor of a higher level of accuracy in an adjustable constant temperature device, adjust the constant temperature device to several selected temperature points, manually compare and record the readings of the two, and obtain a series of corresponding differences. After multiple heating and cooling, repeated testing, wait for the difference to stabilize and record it as the correction value for the sensor that needs to be calibrated.

[0005] However, the manual calibration method of the thermocouple temperature sensor requires special operators to monitor and operate it, and the time waiting for the temperature of the thermostat to rise or fall is too long. After each calibration, the temperature needs to be readjusted and the wiring needs to be reconnected, which takes a lot of time. In addition, the thermostat has temperature errors, and the single test time is too long, resulting in fewer test data samples. The probes of different temperature sensors also have measurement errors due to differences in manufacturing processes. The above problems will affect the accuracy of the calibration results.

[0006] In addition, there are many factors in the entire sensor system that lead to reduced measurement accuracy of the thermocouple exhaust temperature sensor, including: inconsistent sensor probe length; different contact resistances at welding points due to welding process; inconsistent reference voltages of the microcontroller ADC module or external AD chip; inconsistent external discrete voltage regulator filter components, etc. The traditional calibration method cannot calibrate the PCB board separately because both the PCB board and the thermocouple probe may have accuracy errors, and the calibration cannot continue when the thermocouple probe has excessive errors or fails. Summary of the invention

[0007] Purpose of the invention: The present invention proposes an automatic calibration system and method for a thermocouple exhaust temperature sensor to reduce the temperature measurement error of the thermocouple exhaust temperature sensor caused by the above reasons, realizes the calibration of the PCB board of the thermocouple exhaust temperature sensor, avoids the sensor system measurement error caused by the thermocouple probe error and the above reasons; and solves the problems of complex equipment, long time consumption and unstable temperature of the traditional calibration method.

[0008] Technical solution: The automatic calibration system of the thermocouple exhaust temperature sensor of the present invention includes a single-chip microcomputer lower computer software, a host computer monitoring software, a thermocouple exhaust temperature sensor, a DAC controller, a communication module, a computer and a power supply module;

[0009] The microcontroller lower computer software is responsible for voltage collection, fault feedback and uploading of collection results;

[0010] The upper computer monitoring software is responsible for monitoring the status of the single-chip lower computer and the DAC controller; the output end of the DAC controller is connected to the thermocouple exhaust temperature sensor.

[0011] The thermocouple exhaust temperature sensor microcontroller includes a main control chip, an ADC module, a CAN transceiver and a power supply chip.

[0012] The automatic calibration method of the thermocouple exhaust temperature sensor of the present invention comprises the following steps:

[0013] (1) Initialization of the host computer:

[0014] (1.1) The host computer sends a handshake message to the thermocouple exhaust temperature sensor and DAC controller, and sends a random number plaintext along with the frame, waiting for the response from the thermocouple exhaust temperature sensor and DAC controller;

[0015] (1.2) When both the thermocouple exhaust temperature sensor and the DAC controller reply, stop sending the handshake message; if the fault bit in the received message contains a fault flag, the specific fault is displayed through the human-machine interface; if there is no fault, proceed to the next step;

[0016] (1.3) By comparing the received handshake message with the ciphertext stored locally on the host computer, determine whether the thermocouple exhaust temperature sensor and DAC controller have been tampered with. If tampered with, an alarm is issued through the host computer. If not, proceed to the next step;

[0017] (1.4) Send the host computer ready message and wait for the thermocouple exhaust temperature sensor calibration request;

[0018] (2) Initialization of the thermocouple exhaust temperature sensor

[0019] (2.1) Read the last byte of the flash memory on the thermocouple exhaust temperature sensor microcontroller. If it is the same as the preset value 0xAA, skip the calibration process, feedback the calibration completion to the upper computer, and jump to the normal working process; if the last byte is different from the preset value 0xAA, proceed to the next step;

[0020] (2.2) Perform write and read operations on the calibration data area used by the thermocouple exhaust temperature sensor to repeatedly determine whether the flash memory area is damaged; if damaged, send a fault command to the host computer during the handshake stage;

[0021] (2.3) Collect data from the thermocouple exhaust temperature sensor. If a short circuit or open circuit occurs, send a fault command to the host computer during the handshake phase; if there is no fault, proceed to the next step;

[0022] (2.4) The voltage of the two thermistors on the thermocouple exhaust temperature sensor is collected by ADC. After the conversion is completed, the temperature is obtained by looking up the table, and it is assumed that the test environment is at the set value; if the temperature deviation of the two thermistors is too large, or the temperature exceeds the set value too much, a fault command is sent to the upper computer during the handshake stage; if there is no fault, execute the next step;

[0023] (2.5) Wait for the host computer to send a handshake message. After receiving it, send a handshake message to the host computer, and use the given encryption algorithm to calculate the ciphertext according to the random number and attach it to the handshake message; wait for the host computer to send a ready mark message.

[0024] (3) DAC controller initialization:

[0025] (3.1) DAC controller outputs the set voltage value;

[0026] (3.2) The DAC controller collects the corresponding voltage value. If the error between the collected voltage value and the actual output voltage value is greater than 0.1mV, it is considered that there is a fault in the DAC controller output, and the DAC analog output fault is sent to the upper computer during the handshake phase; if there is no fault, proceed to the next step;

[0027] (3.3) Wait for the host computer to send a handshake message, and after receiving it, send a handshake message to the host computer, and use the given encryption algorithm to calculate the ciphertext according to the random number and attach it to the handshake message; wait for the host computer to send a ready mark message;

[0028] (4) The host computer starts calibration after sending the ready message:

[0029] (4.1) After receiving the ready message from the host computer, the thermocouple exhaust temperature sensor shields the normal working message, sends a calibration request to the host computer, sends a message, and stops sending after receiving the confirmation message reply from the host computer;

[0030] (4.2) The host computer waits for the sensor calibration request instruction, and after receiving the calibration request of the thermocouple exhaust temperature sensor, sends a confirmation reply to the thermocouple exhaust temperature sensor;

[0031] (4.3) The host computer sends the output analog voltage V to the DAC controller through the bus in a loop 1 , stop sending after receiving the confirmation message reply from the DAC controller;

[0032] (4.4) After receiving the ready message from the host computer, the DAC controller waits for the voltage output command from the host computer, and replies with confirmation information after receiving the voltage output command from the host computer;

[0033] (4.5) The DAC controller generates the analog voltage V sent by the host computer. 1 Instruction, set each DAC controller output channel to V1; send output completion instruction to the host computer, and stop sending after receiving the confirmation information reply from the host computer;

[0034] (4.6) The host computer waits for the DAC controller to output the completion instruction, and replies with confirmation information after receiving the output completion instruction from the DAC controller;

[0035] (4.7) The host computer sends a voltage collection command to the thermocouple exhaust temperature sensor, and stops sending after receiving a confirmation message reply from the thermocouple exhaust temperature sensor;

[0036] (4.8) The thermocouple exhaust temperature sensor waits for the voltage acquisition command from the host computer, and replies with confirmation information after receiving the voltage acquisition command from the host computer;

[0037] (4.9) The thermocouple exhaust temperature sensor collects the four-way thermocouple analog voltage and records and stores it as A1;

[0038] (4.10) The thermocouple exhaust temperature sensor uploads the voltage data obtained in step (4.9) to the host computer, sends a message, and stops sending after receiving a confirmation message reply from the host computer;

[0039] (4.11) The host computer waits for the thermocouple exhaust temperature sensor to upload the collected voltage data, and replies with confirmation information after receiving the data uploaded by the thermocouple exhaust temperature sensor;

[0040] (4.12) The host computer stores the data uploaded by the thermocouple exhaust temperature sensor and records it as U1;

[0041] (4.13) Repeat steps (4.3) to (4.12) to obtain A1, A2...An and U2, U3...Un according to the analog voltage V2, V3...Vn of the host computer;

[0042] (4.14) The host computer calculates the difference between Un and Vn, i.e., the offset, based on the actual data U1-Un obtained by the thermocouple exhaust temperature sensor, and corrects the voltage-temperature MAP originally set by the thermocouple exhaust temperature sensor by the offset;

[0043] (4.15) The host computer sends the corrected voltage-temperature MAP to the sensor, sends a message, and stops sending after receiving the confirmation message reply from the thermocouple exhaust temperature sensor;

[0044] (4.16) The thermocouple exhaust temperature sensor waits to receive the voltage-temperature MAP from the host computer, and replies with confirmation information after receiving the voltage-temperature MAP;

[0045] (4.17) The thermocouple exhaust temperature sensor writes the corrected voltage-temperature MAP to the MCU flash memory and writes 0xAA to the last byte of the flash memory;

[0046] (4.18) The thermocouple exhaust temperature sensor sends a calibration completion command to the upper computer, sends a message, and stops sending after receiving a confirmation message from the upper computer, thus completing the calibration;

[0047] (4.19) The host computer waits for the calibration completion instruction of the thermocouple exhaust temperature sensor, and replies with confirmation information after receiving the calibration completion instruction of the thermocouple exhaust temperature sensor;

[0048] (4.20) The host computer sends a calibration completion command to the DAC controller, sends a message, and stops sending after receiving a confirmation message reply from the DAC controller, thus ending the calibration;

[0049] (4.21) The DAC controller waits for the calibration completion command from the host computer. After receiving the calibration completion command from the host computer, it replies with a confirmation message to end the calibration.

[0050] In step (1.1), the host computer uses a given encryption algorithm to calculate the ciphertext according to the random number.

[0051] In step (2.5), the ciphertext is calculated using the given encryption algorithm according to the random number and attached to the handshake message.

[0052] In step (4.3), V 1 The voltage value corresponding to the typical temperature value of the thermocouple.

[0053] Beneficial effects: Compared with the prior art, the present invention shortens the calibration time, eliminates the calibration interference caused by the accuracy error of the thermocouple probe, realizes the calibration of the thermocouple sensor PCB board, improves the calibration efficiency and the accuracy of the calibration results, and has a high degree of automation. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1It is a schematic diagram of the structure of the automatic calibration system of the thermocouple exhaust temperature sensor of the present invention;

[0055] Figure 2 This is a flow chart of the automatic calibration method of the thermocouple exhaust temperature sensor of the present invention;

[0056] Figure 3 This is a summary table of fault codes of the host computer used in the present invention. DETAILED DESCRIPTION

[0057] The automatic calibration system of the thermocouple exhaust temperature sensor of the present invention includes two parts: hardware and software. The software part includes single-chip microcomputer lower computer software and upper computer monitoring software; the single-chip microcomputer lower computer is mainly responsible for controlling each module of the single-chip microcomputer, including voltage acquisition and fault feedback and uploading of acquisition results; the upper computer monitoring software is responsible for status monitoring and control of the single-chip microcomputer lower computer and DAC controller, and real-time observation of the working status of the single-chip microcomputer and DAC controller and the feedback data.

[0058] The hardware part includes thermocouple exhaust temperature sensor, DAC controller, communication module, computer and power module. The microcontroller of the thermocouple exhaust temperature sensor mainly includes the main control chip, ADC module, CAN transceiver, power chip, etc. The ADC module uses LMP90080, which is a 16-bit low-power ADC. The amplification gain and sampling frequency can be set by programming, and the gain settings of 1x, 2x, 4x, 8x, 16x, 32x, 64x or 128x are provided; the ADC module uses differential input for sampling, and LMP90080 provides up to 4 differential channels: CH0, CH1, CH2 and CH3, so four analog voltages can be collected at the same time.

[0059] The DAC controller is a 16-bit 4-channel ADC that can output analog voltage to 4 thermocouples at the same time, with a resolution of 0.075mv and a reference voltage of 1V. The power supply is a 12V regulated DC power supply. The communication module includes a dual-channel CAN card and a CAN bus.

[0060] Press the system hardware Figure 1The computer, thermocouple exhaust temperature sensor, and DAC controller are connected to the CAN card through the CAN bus, the output end of the DAC controller is connected to the hot and cold end wires of the thermocouple exhaust temperature sensor through a wire, and the power supply is connected to the DAC controller and the thermocouple exhaust temperature sensor for power supply. The computer, thermocouple exhaust temperature sensor, and DAC controller are connected to the CAN card through the CAN bus, data transmission and command transmission are performed through CAN communication, the output end of the DAC is connected to the hot and cold end wires of the thermocouple exhaust temperature sensor through a wire, and the power supply is connected to the DAC controller and the temperature sensor for power supply. The thermocouple exhaust temperature sensor sends a calibration request to the upper computer through CAN communication. After receiving the calibration request, the upper computer controls the DAC module to output a specific analog voltage. After the analog voltage output is completed, the upper computer sends an acquisition instruction to the sensor through CAN communication, and the sensor performs data acquisition. After the acquisition is completed, the result is uploaded to the upper computer through CAN communication. After the upper computer processes the data, the result is sent to the microcontroller through CAN communication, and the microcontroller finally writes the calibration data into the flash memory.

[0061] The calibration process is divided into two parts: the first part is the initialization of each control component; the second part is the calibration implementation body.

[0062] The automatic calibration method of the thermocouple exhaust temperature sensor of the present invention comprises the following steps:

[0063] (1) Host computer initialization

[0064] (1.1) The host computer sends a handshake message to the thermocouple exhaust temperature sensor and the DAC controller at a rate of one frame per 100ms, and sends a random number plaintext with the frame. The host computer uses a given encryption algorithm to calculate the ciphertext according to the random number and waits for the reply from the thermocouple exhaust temperature sensor and the DAC controller;

[0065] (1.2) When both the thermocouple exhaust temperature sensor and the DAC controller reply, stop sending the handshake message; if the fault bit in the received message contains a fault flag, the specific fault is displayed through the human-machine interface to prompt the operator with the specific result and specific operation; if there is no fault, proceed to the next step;

[0066] (1.3) By comparing the received handshake message with the ciphertext stored locally on the host computer, determine whether the thermocouple exhaust temperature sensor and DAC controller have been maliciously tampered with. If tampered with, an alarm is issued through the host computer; if not, proceed to the next step;

[0067] (1.4) Send the host computer ready message and wait for the thermocouple exhaust temperature sensor calibration request;

[0068] (2) Initialization of the thermocouple exhaust temperature sensor

[0069] (2.1) Read the last byte of the flash memory on the thermocouple exhaust temperature sensor microcontroller. If it is the same as the preset value 0xAA, skip the calibration process, feedback the calibration completion to the upper computer, and jump to the normal working process; if the last byte is different from the preset value 0xAA, proceed to the next step;

[0070] (2.2) Perform write-read operations on the calibration data area (e.g., 20 bytes of data) used by the thermocouple exhaust temperature sensor, and repeat twice to determine whether the flash memory area is damaged; if damaged, send a fault command to the host computer during the handshake phase;

[0071] (2.3) Collect data from the thermocouple exhaust temperature sensors of the four channels to determine whether the wiring of the thermocouple exhaust temperature sensors is reliable. If a short circuit or open circuit occurs, send a fault command to the host computer during the handshake phase; if there is no fault, execute the next step;

[0072] (2.4) The voltage of the two thermistors on the sensor board is collected by ADC. After the conversion is completed, the temperature is obtained by looking up the table, and the test environment is assumed to be 25°C; if the temperature deviation between the two is too large or the temperature exceeds 25°C too much, a fault command is sent to the host computer during the handshake stage; if there is no fault, execute the next step;

[0073] (2.5) Wait for the host computer to send a handshake message. After receiving it, send a handshake message to the host computer, and use the given encryption algorithm to calculate the ciphertext according to the random number and attach it to the handshake message; wait for the host computer to send a ready mark message.

[0074] (3) DAC controller initialization

[0075] (3.1) The DAC controller outputs several sets of voltage values ​​during normal operation, such as 10mV and 20mV;

[0076] (3.2) The DAC controller collects the corresponding voltage value through the internal loop. If the error between the collected voltage value and the actual output voltage value is more than 0.1mV, it is considered that there is a fault in the DAC controller output, and the DAC analog output fault is sent to the upper computer during the handshake stage; if there is no fault, proceed to the next step;

[0077] (3.3) Wait for the host computer to send a handshake message, and after receiving it, send a handshake message to the host computer, and use the given encryption algorithm to calculate the ciphertext according to the random number and attach it to the handshake message; wait for the host computer to send a ready mark message; the host computer displays a summary of the fault code as follows Figure 3 ;

[0078] (4) Calibration body: After each module is initialized and there is no fault feedback, the host computer starts calibration after sending a ready message:

[0079] (4.1) After receiving the ready message from the host computer, the thermocouple exhaust temperature sensor shields the normal working message, sends a calibration request to the host computer, sends a message at a rate of one frame per 100ms, and stops sending after receiving the confirmation message reply from the host computer;

[0080] (4.2) The host computer waits for the sensor calibration request instruction, and after receiving the calibration request of the thermocouple exhaust temperature sensor, sends a confirmation reply to the thermocouple exhaust temperature sensor;

[0081] (4.3) The host computer sends the output analog voltage V1 to the DAC controller through the bus in a loop, sending messages at a rate of one frame per 100ms. After receiving the confirmation message from the DAC controller, it stops sending. (V 1 is the voltage value corresponding to the typical temperature value of the thermocouple);

[0082] (4.4) After receiving the ready message from the host computer, the DAC controller waits for the voltage output command from the host computer, and replies with confirmation information after receiving the voltage output command from the host computer;

[0083] (4.5) The DAC controller generates the analog voltage V sent by the host computer. 1 Instruction, set each DAC controller output channel to V1; send output completion instruction to the host computer, send messages at a rate of one frame per 100ms, and stop sending after receiving the confirmation message reply from the host computer;

[0084] (4.6) The host computer waits for the DAC controller to output the completion instruction, and replies with confirmation information after receiving the output completion instruction from the DAC controller;

[0085] (4.7) The host computer sends a voltage acquisition instruction to the thermocouple exhaust temperature sensor, sending messages at a rate of one frame per 100ms, and stops sending after receiving the confirmation message reply from the thermocouple exhaust temperature sensor.

[0086] (4.8) The thermocouple exhaust temperature sensor waits for the voltage acquisition command from the host computer, and replies with confirmation information after receiving the voltage acquisition command from the host computer;

[0087] (4.9) The thermocouple exhaust temperature sensor collects the four-way thermocouple analog voltage and records and stores it as A1;

[0088] (4.10) The thermocouple exhaust temperature sensor uploads the voltage data obtained in step (4.9) to the host computer, sends messages at a rate of one frame per 100ms, and stops sending after receiving the confirmation message reply from the host computer;

[0089] (4.11) The host computer waits for the thermocouple exhaust temperature sensor to upload the collected voltage data, and replies with confirmation information after receiving the data uploaded by the thermocouple exhaust temperature sensor;

[0090] (4.12) The host computer stores the data uploaded by the thermocouple exhaust temperature sensor and records it as U1;

[0091] (4.13) Repeat steps (4.3) to (4.12) to obtain A1, A2...An and U2, U3...Un according to the analog voltage V2, V3...Vn of the host computer;

[0092] (4.14) The host computer calculates the difference between Un and Vn, i.e., the offset, based on the actual data U1-Un obtained by the thermocouple exhaust temperature sensor, and corrects the voltage-temperature MAP originally set by the thermocouple exhaust temperature sensor by the offset, i.e., performs synchronous offset processing on the originally set voltage-temperature MAP;

[0093] (4.15) The host computer sends the corrected voltage-temperature MAP to the thermocouple exhaust temperature sensor, sending messages at a rate of one frame per 100ms, and stops sending after receiving the confirmation message reply from the thermocouple exhaust temperature sensor;

[0094] (4.16) The thermocouple exhaust temperature sensor waits to receive the voltage-temperature MAP from the host computer, and replies with confirmation information after receiving the voltage-temperature MAP;

[0095] (4.17) The thermocouple exhaust temperature sensor writes the corrected voltage-temperature MAP into the MCU on-chip flash memory and writes 0xAA into the last byte of the flash memory;

[0096] (4.18) The thermocouple exhaust temperature sensor sends a calibration completion command to the host computer, sending messages at a rate of one frame per 100ms. After receiving the confirmation message reply from the host computer, it stops sending and ends the calibration.

[0097] (4.19) The host computer waits for the calibration completion instruction of the thermocouple exhaust temperature sensor, and replies with confirmation information after receiving the calibration completion instruction of the thermocouple exhaust temperature sensor;

[0098] (4.20) The host computer sends a calibration completion command to the DAC controller, sending messages at a rate of one frame every 100ms. After receiving the confirmation message reply from the DAC controller, it stops sending and ends the calibration;

[0099] (4.21) The DAC controller waits for the calibration completion command from the host computer. After receiving the calibration completion command from the host computer, it replies with a confirmation message to end the calibration.

Claims

1. A method for automatic calibration of a thermocouple exhaust temperature sensor, characterized in that: The following steps are involved: (1) Initialization of the host computer: (1.1) The host computer sends a handshake message to the thermocouple exhaust temperature sensor and DAC controller, and sends a random number plaintext along with the frame, waiting for the response from the thermocouple exhaust temperature sensor and DAC controller; (1.2) When both the thermocouple exhaust temperature sensor and the DAC controller reply, stop sending the handshake message; if the fault bit in the received message contains a fault flag, the specific fault is displayed through the human-machine interface; if there is no fault, proceed to the next step; (1.3) By comparing the received handshake message with the ciphertext stored locally on the host computer, determine whether the thermocouple exhaust temperature sensor and DAC controller have been tampered with. If tampered with, an alarm is issued through the host computer. If not, proceed to the next step; (1.4) Send the host computer ready message and wait for the thermocouple exhaust temperature sensor calibration request; (2) Initialization of the thermocouple exhaust temperature sensor (2.1) Read the last byte of the flash memory on the thermocouple exhaust temperature sensor microcontroller. If it is the same as the preset value 0xAA, skip the calibration process, feedback the calibration completion to the upper computer, and jump to the normal working process; if the last byte is different from the preset value 0xAA, proceed to the next step; (2.2) Perform write and read operations on the calibration data area used by the thermocouple exhaust temperature sensor to repeatedly determine whether the flash memory area is damaged; if damaged, send a fault command to the host computer during the handshake stage; (2.3) Collect data from the thermocouple exhaust temperature sensor. If a short circuit or open circuit occurs, send a fault command to the host computer during the handshake phase; if there is no fault, proceed to the next step; (2.4) The voltage of the two thermistors on the thermocouple exhaust temperature sensor is collected by ADC. After the conversion is completed, the temperature is obtained by looking up the table, and it is assumed that the test environment is at the set value; if the temperature deviation of the two thermistors is too large, or the temperature exceeds the set value too much, a fault command is sent to the upper computer during the handshake stage; if there is no fault, execute the next step; (2.5) Wait for the host computer to send a handshake message, and after receiving it, send a handshake message to the host computer, and use the given encryption algorithm to calculate the ciphertext according to the random number and attach it to the handshake message; wait for the host computer to send a ready mark message; (3) DAC controller initialization: (3.1) DAC controller outputs the set voltage value; (3.2) The DAC controller collects the corresponding voltage value. If the error between the collected voltage value and the actual output voltage value is greater than 0.1mV, it is considered that there is a fault in the DAC controller output, and the DAC analog output fault is sent to the upper computer during the handshake phase; if there is no fault, proceed to the next step; (3.3) Wait for the host computer to send a handshake message, and after receiving it, send a handshake message to the host computer, and use the given encryption algorithm to calculate the ciphertext according to the random number and attach it to the handshake message; wait for the host computer to send a ready mark message; (4) The host computer starts calibration after sending the ready message: (4.1) After receiving the ready message from the host computer, the thermocouple exhaust temperature sensor shields the normal working message, sends a calibration request to the host computer, sends a message, and stops sending after receiving the confirmation message reply from the host computer; (4.2) The host computer waits for the sensor calibration request instruction, and after receiving the calibration request of the thermocouple exhaust temperature sensor, sends a confirmation reply to the thermocouple exhaust temperature sensor; (4.3) The host computer cyclically sends the output analog voltage V1 to the DAC controller through the bus, and stops sending after receiving the confirmation message reply from the DAC controller; (4.4) After receiving the ready message from the host computer, the DAC controller waits for the voltage output command from the host computer, and replies with confirmation information after receiving the voltage output command from the host computer; (4.5) The DAC controller sets each DAC controller output channel to V1 according to the analog voltage V1 instruction sent by the host computer; sends an output completion instruction to the host computer, and stops sending after receiving a confirmation message reply from the host computer; (4.6) The host computer waits for the DAC controller to output the completion instruction, and replies with confirmation information after receiving the output completion instruction from the DAC controller; (4.7) The host computer sends a voltage collection command to the thermocouple exhaust temperature sensor, and stops sending after receiving a confirmation message reply from the thermocouple exhaust temperature sensor; (4.8) The thermocouple exhaust temperature sensor waits for the voltage acquisition command from the host computer, and replies with confirmation information after receiving the voltage acquisition command from the host computer; (4.9) The thermocouple exhaust temperature sensor collects the four-way thermocouple analog voltage and records and stores it as A1; (4.10) The thermocouple exhaust temperature sensor uploads the voltage data obtained in step (4.9) to the host computer, sends a message, and stops sending after receiving a confirmation message reply from the host computer; (4.11) The host computer waits for the thermocouple exhaust temperature sensor to upload the collected voltage data, and replies with confirmation information after receiving the data uploaded by the thermocouple exhaust temperature sensor; (4.12) The host computer stores the data uploaded by the thermocouple exhaust temperature sensor and records it as U1; (4.13) Repeat steps (4.3) to (4.12) to obtain A1, A2...An and U2, U3...Un according to the analog voltage V2, V3...Vn of the host computer; (4.14) The host computer calculates the difference between Un and Vn, i.e., the offset, based on the actual data U1-Un obtained by the thermocouple exhaust temperature sensor, and corrects the voltage-temperature MAP originally set by the thermocouple exhaust temperature sensor by the offset; (4.15) The host computer sends the corrected voltage-temperature MAP to the sensor, sends a message, and stops sending after receiving the confirmation message reply from the thermocouple exhaust temperature sensor; (4.16) The thermocouple exhaust temperature sensor waits to receive the voltage-temperature MAP from the host computer, and replies with confirmation information after receiving the voltage-temperature MAP; (4.17) The thermocouple exhaust temperature sensor writes the corrected voltage-temperature MAP to the MCU flash memory and writes 0xAA to the last byte of the flash memory; (4.18) The thermocouple exhaust temperature sensor sends a calibration completion command to the upper computer, sends a message, and stops sending after receiving a confirmation message from the upper computer, thus completing the calibration; (4.19) The host computer waits for the calibration completion instruction of the thermocouple exhaust temperature sensor, and replies with confirmation information after receiving the calibration completion instruction of the thermocouple exhaust temperature sensor; (4.20) The host computer sends a calibration completion command to the DAC controller, sends a message, and stops sending after receiving a confirmation message reply from the DAC controller, thus ending the calibration; (4.21) The DAC controller waits for the calibration completion command from the host computer. After receiving the calibration completion command from the host computer, it replies with a confirmation message to end the calibration.

2. The automatic calibration method for thermocouple exhaust temperature sensor according to claim 1, characterized in that: In step (1.1), the host computer uses a given encryption algorithm to calculate the ciphertext according to the random number.

3. The automatic calibration method for thermocouple exhaust temperature sensor according to claim 1, characterized in that: In step (2.5), the ciphertext is calculated using the given encryption algorithm according to the random number and attached to the handshake message.

4. The automatic calibration method for thermocouple exhaust temperature sensor according to claim 1, characterized in that: In step (4.3), V1 is the voltage value corresponding to the typical temperature value of the thermocouple.

5. A system using the automatic calibration method of the thermocouple exhaust temperature sensor according to claim 1, characterized in that: Including microcontroller lower computer software, upper computer monitoring software, thermocouple exhaust temperature sensor, DAC controller, communication module, computer and power supply module; The microcontroller lower computer software is responsible for voltage collection, fault feedback and uploading of collection results; The upper computer monitoring software is responsible for status monitoring and control of the single-chip microcomputer lower computer and the DAC controller; the output end of the DAC controller is connected to the cold and hot end wires of the thermocouple exhaust temperature sensor.

6. The automatic calibration system for thermocouple exhaust temperature sensors according to claim 5, characterized in that: The thermocouple exhaust temperature sensor single chip computer includes a main control chip, an ADC module, a CAN transceiver and a power chip.

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