Device for measuring surface temperature in non-contact manner

Abstract

The invention relates to the technical field of surface temperature measurement based on an infrared radiation principle, and discloses a non-contact surface temperature measurement device which realizes surface temperature measurement through cooperation of a plurality of components. The optical system is located in front of the infrared detector, the field angle is determined, infrared radiation is focused, and a 3D printing black sealing shell of the optical system is rainproof and windproof. The infrared radiation detector of the MLX90614 chip converts infrared energy into a voltage signal and processes data, the data is sent to the main processor through the signal conditioning circuit for analog-to-digital conversion and other operations, and the sensor is endowed with digital and intelligent characteristics. The communication module comprises an RS-232 serial port and a ZigBee wireless communication module and is used for data transmission and connection with an upper computer, and the state monitoring module monitors the work of the processor. Hardware design is completed by using an embedded system and a ZigBee technology, software design is realized by IAR and Z-Stack protocol stacks, and the surface temperature can be accurately measured. The device also has two-way communication and online upgrading functions, the emissivity and the distance are corrected through an algorithm, the efficiency is improved, the standard requirements are met, and meteorological observation and ground temperature measurement are assisted.

Description

Technical Field

[0001] The present invention relates to the technical field of measuring surface temperature using the principle of infrared radiation, and specifically to a device for non-contact measurement of surface temperature. Background Art

[0002] In the field of ground temperature measurement, there are mainly two measurement methods at home and abroad: contact type and non-contact type.

[0003] Contact temperature measurement method:

[0004] For example, the glass liquid ground temperature observation method and the platinum resistance ground temperature observation method in the "Ground Meteorological Observation Specification". Common sensing elements include thermocouples and thermal resistance sensors. Thermocouple temperature measurement is based on the fact that two different metal conductors are spliced to form a closed loop. When the temperatures at two points are different, a thermal electromotive force is generated, which is proportional to the temperature difference, thereby realizing temperature measurement.

[0005] The contact temperature measurement method can measure the true temperature of an object, but it has many disadvantages. During measurement, the sensing probe needs to be in full contact with the underlying surface to reach thermal equilibrium. The temperature transfer takes time, there is a hysteresis phenomenon, the dynamic characteristics are poor, the response speed is slow, and it is greatly affected by the external environment and the placement method. For example, when a platinum resistance ground temperature sensor measures the surface temperature, the placement method of its temperature sensing probe makes the measured temperature the average temperature of the underlying surface and the air surface in contact, which is deviated from the true surface temperature, and there is a hysteresis in the process of reaching thermal equilibrium.

[0006] Non-contact temperature measurement method:

[0007] It mainly measures temperature through laser interference, sound waves, and infrared radiation. Among them, the use of infrared radiation for temperature measurement is the most extensive. Its advantages are that it does not contact the object to be measured, does not interfere with the surface temperature distribution of the object, and has a fast response.

[0008] However, the measurement accuracy of this method is affected by influencing factors such as the emissivity of the underlying surface, the detection height, and atmospheric radiation. At present, there are few infrared sensors in China that specifically use the principle of infrared radiation to measure surface temperature. The ground temperature sensor used for assessment in the second-generation automatic weather station is an analog infrared temperature sensor, without a dedicated signal processing unit, and the data collector needs to collect and process the signal.

[0009] In view of the insufficient intelligence of infrared ground temperature sensors in the existing meteorological system, in order to meet the requirements of refined, intelligent, and modern surface temperature measurement, improve the work efficiency of infrared temperature measurement, and realize scientific and information management, it is necessary to design a device for non-contact measurement of surface temperature for ground temperature collection work such as automatic weather stations. Summary of the Invention

[0010] The purpose of the present invention is to provide a device for non-contact measurement of surface temperature to solve the problems raised in the above background art.

[0011] To achieve the above object, the present invention provides the following technical solution: A non-contact device for measuring surface temperature, comprising:

[0012] An optical system, disposed in front of the infrared temperature detector, for determining the size of the sensor field of view and focusing the infrared radiation energy onto the absorption window of the detector;

[0013] An infrared radiation detector, using the MLX90614 precision digital temperature measurement chip of Melexis company, for converting infrared energy into a weak voltage signal in millivolts, and controlling the temperature acquisition and processing process through an internal state machine, and then transmitting the calculated temperature data via PWM or SMBus mode;

[0014] A signal conditioning circuit, for processing the voltage signal output by the infrared radiation detector;

[0015] A main processor, for performing analog-to-digital conversion, processing and temperature calculation on the signal processed by the signal conditioning circuit, and capable of realizing the acquisition, analog-to-digital conversion, storage and data processing of analog signals, endowing the sensor with digital and intelligent features;

[0016] A communication module, including an RS-232 serial port and a ZigBee wireless communication module, for realizing the connection with the host computer and data transmission, wherein the ZigBee wireless communication module is implemented by a CC2530 chip, and the RS-232 serial port communication part uses an SN65C3232 chip to realize the conversion between the TTL level signal of the main control chip and the RS-232 signal;

[0017] A status monitoring module, disposed on the processor, for real-time monitoring of the working process of the microprocessor.

[0018] Preferably, the sensor housing of the optical system is made by 3D printing technology, using black wire, which is light-shielding and non-reflective. The housing is a sealed cavity, which can prevent rain and wind to ensure the normal operation of the sensor.

[0019] Preferably, the device further includes an acquisition base plate, and the peripheral circuit of the acquisition base plate includes:

[0020] The CC2530 minimum system circuit, including a power supply part for supplying power to each device, a crystal oscillator part for providing a clock frequency for the main chip CC2530F256, a reset part for restarting the software system, a download circuit for program download and debugging, and a radio frequency circuit for ZigBee wireless communication of the collected data in the later stage. The crystal oscillator is mainly composed of external crystal oscillators with frequencies of 32MHz and 32.768KHz respectively, and a capacitor filter circuit with filtering and decoupling functions is also added to the circuit;

[0021] The system power supply circuit is powered by a 12V DC voltage. Through a two-stage step-down circuit, the input +12V DC voltage is reduced to 5V and -5V to supply power to some chips that require 5V / -5V voltages. Then, the 5V is further reduced to 3.3V, and the analog and digital power supplies are separated. The first-stage voltage conversion chip uses the TPS5430 chip of TI. The TPS5430 chip is used for the 12V to -5V conversion, and the negative voltage adjustable output integrated voltage regulator chip LM137 is used to realize the -5V to -3.3V conversion.

[0022] Preferably, the device further includes a temperature signal acquisition circuit, which mainly consists of an infrared temperature signal acquisition part and a Pt100 platinum resistance reference temperature signal acquisition part. The infrared temperature signal acquisition part is realized by directly connecting the MLX90614 high-precision digital infrared detector to the IO pins of the main control chip.

[0023] Preferably, the device further includes an ultrasonic signal acquisition circuit, and the HC-SR04 ultrasonic sensor is used to collect distance data.

[0024] Preferably, the device further includes an external clock circuit, which is designed using the DS3231 chip. The clock is controlled through the I2C protocol, and it is powered by a hybrid power supply method of VCC3.3V and a CR1220 button battery. When there is an external power supply, the external power supply supplies power to Vbat. When the external power supply is disconnected, BAT1 supplies power.

[0025] Preferably, the device further includes a FLASH storage circuit. The W25X32 is selected as the external storage unit to increase the storage space. The CC2530F256 includes 8KB of RAM and 256KB of FLASH. The RAM mainly stores the collected data, input variables, and intermediate results of operations, etc. The FLASH is mainly used to store system constants, etc.

[0026] Preferably, the device further includes a data correction algorithm module, and the data correction algorithm module includes:

[0027] An emissivity correction unit, which is used to correct the measured temperature according to the emissivity values of different underlying surfaces. The MLX90614 calibrates the emissivity of the object to 1, and the emissivity calibration coefficient is stored at 004h in the EEPROM. When actually measuring the surface temperature, the temperature data is calculated according to the current underlying surface emissivity value written into the program. Common underlying surfaces such as grass have an emissivity of 0.980, cement ground has an emissivity of 0.933, and soil has an emissivity of 0.974;

[0028] A distance compensation unit is used to compensate the collected temperature values according to the measured distance. The distance coefficient K of MLX90614 is 1:6. The distance from 0 - 100 cm is equally divided with a base of 5 cm. By linearly fitting to calculate the relationship between the infrared temperature T and the distance parameter D, the temperature compensation value To is obtained, and then the temperature value T is corrected.

[0029] Preferably, the device further includes an OTA online upgrade module. When the OTA server sends an image upgrade request to the OTA client in the form of unicast or broadcast, after the client is informed that there is a new image available, it determines whether the new image can be used by querying the next image request and response message. After the firmware update request is successful, the client writes the received image to the specified Flash location. After the upgrade image download is completed, the server responds to the "upgrade end" request, and the client enters the new firmware program according to the instruction.

[0030] Preferably, the main processor uses the CC2530F256 chip of Texas Instruments, which provides resources for ZigBee wireless transmission, and the 256KB FLASH memory provides space for the storage of TEDS.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. This non-contact device for measuring surface temperature comprehensively uses embedded system technology and ZigBee technology to complete the design of the signal acquisition hardware part, and combines IAR and the Z-Stack protocol stack based on CC2530 to realize the software part design, successfully realizing the accurate measurement of surface temperature using infrared radiation, providing strong feasibility support for the automatic measurement of ground temperature in comprehensive meteorological observation.

[0033] 2. This non-contact device for measuring surface temperature has a two-way communication function. Through the RS-232 serial port and the ZigBee wireless communication module, it can achieve stable and efficient data transmission with the upper computer, meeting the requirements of different scenarios.

[0034] 3. This non-contact device for measuring surface temperature has an online upgrade function. With the help of the OTA online upgrade module, developers can timely update and optimize the program or data processing algorithm, directly remotely update the internal program of the infrared temperature sensor, improving the adaptability and functionality of the device.

[0035] 4. This non-contact device for measuring surface temperature. The data correction algorithm module can correct the collected data according to the emissivity of the underlying surface and the measurement distance, effectively improving the measurement accuracy, making the measurement results more accurate and reliable, thus meeting the refined, intelligent, and modern specifications and requirements for surface temperature measurement, strongly improving the working efficiency of infrared temperature measurement, and realizing the scientific and information-based management of surface temperature measurement. Brief Description of the Drawings

[0036] Figure 1 is the overall structural block diagram of the present invention;

[0037] Figure 2 is the overall structural diagram of the system hardware of the present invention;

[0038] Figure 3 is the schematic diagram of the detector field of view angle;

[0039] Figure 4 is the schematic diagram and physical diagram of the housing;

[0040] Figure 5 is the circuit diagram of the CC2530 minimum system;

[0041] Figure 6 is the 5V and 3.3V positive voltage circuit;

[0042] Figure 7 is the LM137 negative voltage conversion circuit;

[0043] Figure 8 is the overall software flowchart;

[0044] Figure 9 is the OTA online upgrade workflow diagram;

[0045] Figure 10 is the data acquisition program flowchart;

[0046] Figure 11 is the communication module flowchart;

[0047] Figure 12 is the distance compensation processing flowchart. Detailed Embodiment

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0049] The present invention provides a technical solution:

[0050] A non-contact device for measuring the surface temperature of the ground

[0051] Temperature measurement principle (basic law of thermal radiation)

[0052] (1) Kirchhoff's law

[0053] Kirchhoff's radiation law states that in nature, for any object that has reached a certain thermodynamic equilibrium, the ratio of its radiation power spectral density (M) to its radiation absorption ratio (α) at a certain temperature is constant and equal to the radiation power density (f) of any blackbody at that temperature. That is:

[0054]

[0055] (2) Planck's formula

[0056] Planck's law details the relationship between the monochromatic emissive power of an absolute blackbody, wavelength, and thermodynamic temperature. The higher the temperature of an object, the higher the spectral radiant energy it emits. When thermodynamic equilibrium is reached between the Earth's surface and the atmosphere, at a wavelength of λ and a temperature of T, the energy value of the radiation of an absolute blackbody can be calculated by Planck's law:

[0057]

[0058] where C1 and C2 are the first and second radiation constants respectively, and C1 = 3.7418×10 8 (μm 4 ·W / m 2 ) and C2 = 1.439×10 4 (μm·K).

[0059] (3) Stefan-Boltzmann law

[0060] For any blackbody within a certain period of time, the total infrared energy M(T) emitted from a certain area on its surface is proportional to the fourth power of its own thermodynamic temperature T, that is:

[0061] M(T) = σ·ε·T 4

[0062] where M(T) is the radiance of the object, σ is the Stefan-Boltzmann constant, and its value is: σ = 2π 5 k 4 / 15c 2 h 3 = 5.6704×10 -8 W / m 2 ·K 4 , ε is the emissivity of the object, and T is the absolute temperature value of the blackbody. When the radiance M(T) of an object at temperature T is equal to the radiance M(T0) of a blackbody T0, there is

[0063] M(T) = M(T0)

[0064] That is: σεT 4 = σT0 4

[0065] After conversion, the actual temperature of the object to be measured is where: T is the actual temperature, T0 is the radiation temperature, and ε is the emissivity of the underlying surface.

[0066] An optical system is added in front of the infrared temperature detector. The main purpose of the optical system is to determine the size of the sensor's field of view, so that as much infrared radiation energy as possible can be "focused" on the absorption window of the detector. The detector converts the infrared energy into a weak voltage signal in the millivolt range. After being processed by the signal conditioning circuit, the voltage signal is sent to the main processor for analog-to-digital conversion, processing, and temperature calculation. Since the main processor can realize the acquisition, analog-to-digital conversion, storage, and data processing of analog signals, it endows the sensor with digital and intelligent features; at the same time, the function of the software system is fully utilized, and the connection with the host computer is realized through the RS232 serial port. The collected and processed data is transmitted to the computer in text form for algorithm research, thus greatly improving the reliability and data accuracy of the sensor. At the same time, a status monitoring module is designed on the processor to monitor the working process of the microprocessor in real time. See the overall structure block diagram in Figure 1 described.

[0067] The hardware part mainly consists of the design of the front-end optical structure and the design of the hardware board for infrared and ultrasonic signal acquisition. During the design of the optical structure, it should be ensured that as much infrared radiation energy as possible can be collected by the detection element of the sensor. The detector converts the infrared radiation energy into a voltage signal that can be recognized by the hardware acquisition board. After the voltage signal is processed by signal conditioning and amplification, it is sent to the main processor for analog-to-digital conversion and temperature calculation. Finally, it is wirelessly transmitted to the in-field ZigBee terminal node through the ZigBee coordinator, and the connection with the host computer is realized through the RS-232 serial port to obtain the temperature and distance data after acquisition and processing in real time. The data is saved to the PC in text form. The complete hardware structure of the system can be mainly divided into three aspects, namely front-end signal acquisition, core data processing, and data communication. The basic principle block diagram of the hardware is as Figure 2 shown.

[0068] (1) Front-end signal acquisition

[0069] 1. The infrared radiation detector selects the MLX90614 precision digital temperature measurement chip of Melexis. The MLX90614 controls the temperature acquisition and processing process through an internal state machine, and then transmits the calculated temperature data via the PWM or SMBus mode.

[0070] 2. Optical system. Its main function is to enable the infrared surface temperature sensor to receive as much infrared radiation energy as possible, and to concentrate the radiation energy onto the sensor probe for absorption by the probe. The sensor housing is made using 3D printing technology, with a black wire selected. It blocks light and does not reflect light. At the same time, the housing is a sealed cavity that can prevent rain and wind, ensuring the normal operation of the sensor. Figure 3 It is a schematic diagram of the detector's field of view angle. Figure 4 It is a schematic diagram and a physical diagram of the housing.

[0071] 3. Design of the peripheral circuit of the acquisition board

[0072] (1) The board uses the CC2530 minimum system circuit, which mainly includes a power supply part for supplying power to each device, a crystal oscillator part for providing the clock frequency to the main chip CC2530F256, and a reset part that can restart the software system. In addition, a download circuit for program download and debugging and a radio frequency circuit for ZigBee wireless communication of the collected data in the later stage are designed in the circuit. The crystal oscillator in this minimum system circuit is mainly composed of two parts, with frequencies of 32 MHz and 32.768 KHz respectively, and both are external crystal oscillators. A capacitor filter circuit with filtering and decoupling functions is also added to the minimum system circuit. Adding a 1 μF decoupling capacitor to ground next to the input power supply can make the system run more stably. The minimum system circuit diagram of the CC2530F256 chip is as Figure 5 shown.

[0073] (2) Design of the system power supply circuit. The system is powered by a 12V DC voltage. Since the normal operation of some chips requires 5V, -5V, 3.3V, and -3.3V, the power supply part of this system is designed as a two-stage step-down circuit. First, the input +12V DC voltage is stepped down to 5V and -5V to supply power to some chips that require 5 / -5V voltages. Secondly, the 5V is stepped down to 3.3V to separate the analog and digital power supplies according to the different requirements of different chips, reducing unnecessary signal crosstalk. In the design of the power supply step-down circuit, a DC / DC converter with a wide input voltage range is used as the STEP-DOWN step-down converter. The first-stage voltage conversion chip uses the TPS5430 chip of TI Company. The voltage conversion of TPS5430 is as Figure 6 shown.

[0074] The AD620 chip in the infrared signal amplification circuit requires a negative voltage for power supply. Therefore, a negative voltage conversion circuit is designed. By using the buck-boost technology in reverse, the TPS5430 can output a negative voltage. The 12V to -5V still uses the TPS5430, and the second-stage step-down converts -5V to -3.3V using the negative voltage adjustable output integrated voltage regulator chip LM137. The voltage conversion schematic diagram is as Figure 7 shown.

[0075] (2) Design of temperature signal acquisition circuit. The temperature signal acquisition circuit mainly consists of two parts, namely the acquisition of infrared temperature signal and Pt100 platinum resistance reference temperature signal. Since MLX90614 is a high-precision digital infrared detector, the infrared detector can be directly connected to the IO pin of the main control chip to achieve the acquisition of infrared temperature.

[0076] (3) Ultrasonic signal acquisition circuit. In this system, there are mainly two communication modes. The ZigBee wireless communication part can be completed through the built-in resources of CC2530F256. The RS-232 serial communication part uses the SN65C3232 chip to implement the serial communication function, realizing the conversion between the TTL level signal of the main control chip and the RS-232 signal.

[0077] (4) External clock circuit. The external clock circuit is mainly designed by the DS3231 chip. DS3231 uses a 16-pin 300mil SO package and can control the clock through the I2C protocol. Even when there is no power supply, it can still accurately time. The external real-time clock circuit is powered by a hybrid power supply method of VCC3.3V and CR1220 button battery. When there is an external power supply, the external power supply supplies power to Vbat. When the external power supply is disconnected, BAT1 supplies power. This can ensure the continuous operation of the RTC and the content of the backup register is not lost.

[0078] (5) FLASH storage circuit. CC2530F256 contains 8KB of RAM and 256KB of FLASH. Among them, RAM mainly stores the acquired data, input variables, and intermediate results of operations, etc.; FLASH is mainly used to store system constants, etc. 8KB of RAM can only store a small amount of data and run a small number of programs. Therefore, an external storage unit needs to be added to increase the storage space. This motherboard selects W25X32 as the external storage unit.

[0079] System software design

[0080] The software part is mainly used to realize the acquisition and processing of infrared data and ultrasonic data. When the sensor is powered on and starts working, the temperature and ultrasonic data acquisition program continuously samples the output signals of the detector and the sensor, and sends the collected and processed results to the external memory for storage; for the communication part that performs ZigBee wireless transmission and serial port transmission on the collected data, the outdoor acquisition bottom board transmits the data collected by the detector and the ultrasonic sensor through ZigBee wireless transmission to the indoor signal receiving bottom board, and the indoor signal receiving bottom board communicates with the PC upper computer through the RS-232 serial port and displays and stores the results in a fixed position for later data analysis; at the same time, when the data acquisition and processing program needs to be updated, the hardware bottom board realizes near wireless field OTA upgrade and maintenance through ZigBee wireless communication, and finally realizes distance compensation and reflectivity correction of the temperature through the program. Its overall software flowchart is as Figure 8 shown.

[0081] The main function of the online upgrade program is to complete the firmware update. When developers have more optimized programs or data processing algorithms, they can perform OTA online upgrade to directly remotely download the infrared temperature sensor to achieve wireless upgrade of the internal program of the processor. When program upgrade is not required, it enters the Z-Stack protocol stack and starts the operation of the main application program. The Z-Stack protocol stack runs using the task polling method and is mainly responsible for the implementation of the application program functions. The entire software design is mainly programmed in C language, and the IAR software development platform is used in combination with the SmartRF04EB emulator for internal register and program debugging.

[0082] 1. OTA online upgrade. When online upgrade is required, the OTA server first sends a mirror upgrade request to the OTA client in the form of unicast or broadcast, and the client is informed that there is a new mirror available. Then the OTA client will, periodically or after receiving the mirror notification message, determine whether these new images can be used by querying the next image request and response messages. When the firmware update request is successful, the client writes the received mirror to the specified Flash location. After the upgrade mirror download is completed, the server responds to the "upgrade end" request. At this point, the client may immediately enter the new firmware program or may be instructed to wait for a certain period of time before entering the new firmware program. Figure 9 is the flowchart of the OTA online upgrade work.

[0083] 2. Sensor data acquisition. In this design, there is mainly the infrared data acquisition of the infrared detector MLX90614 and the distance data acquisition of the HC-SR04 ultrasonic sensor. The data acquisition part is obtained by writing the corresponding acquisition program through IAR. After the system is powered on, the I / O pins of the main control chip are initialized first, and then the two sensors enter their own acquisition programs respectively and work together. The overall flowchart of data acquisition is as follows Figure 10 as shown

[0084] 3. Wireless and serial communication. This design mainly realizes data transmission through two communication methods: RS-232 serial communication and ZigBee wireless communication. After the external field sensors collect data, they will first transmit the data to the internal field acquisition board through the ZigBee wireless communication method. The wireless communication module can be realized by using the wireless serial port chip of CC2530. After the chip is powered on, the chip initializes each I / O port and the Z-Stack protocol stack first, automatically forms a network through the coordinator, and then after the internal field terminal device successfully joins the network, the external field signal acquisition board starts to send the sensor-collected data to the internal field terminal device. After the terminal device receives the ZigBee data, it parses the data and sends it to the PC-side upper computer through the RS-232 serial port for real-time display, storage and processing. The implementation flowchart of the wireless and serial communication part is as follows Figure 11 .

[0085] 4. Design of data correction algorithm. In actual situations, most of the collected signals are non-linear. Therefore, after the infrared detector and the ultrasonic sensor receive their respective data, the non-linear error caused by the input and output of the system can be corrected by an algorithm to obtain a more accurate temperature value. In this design, the method of curve fitting is used to realize the non-linear correction of the collected data

[0086] (1) Emissivity correction design. As a standard, MLX90614 calibrates the emissivity of an object to 1, and the emissivity calibration coefficient is stored at 004h of the EEPROM (the factory default value is 1.0 = 0xFFFF), a 16-bit value. And there is

[0087] Emissivity = dec2hex[round(65535×ε)]

[0088] Among them, dec2hex[round(X)] represents decimal to hexadecimal conversion and takes the rounded value. In this case, the emissivity value is: ε = 0.1...1.0. Therefore, when actually measuring the surface temperature, according to the emissivity value of the current underlying surface, the emissivity is written into the program, and then the temperature data is calculated. Before writing the data, an erasure operation is performed first. In actual observations, three underlying surfaces (grassland, cement ground, soil) are usually selected for observation. The emissivities of these three underlying surfaces are shown in the following table:

[0089]

[0090] (2) Distance compensation design. As the measurement distance increases, the measurement temperature error of the measured object also increases. Therefore, it is necessary to perform temperature compensation on the collected temperature value according to the distance. The temperature value obtained by adding the compensation value to the measured temperature value is more accurate, improving the temperature measurement accuracy.

[0091] The distance coefficient K of MLX90614 is 1:6, that is, the ratio of the distance S from the infrared temperature sensor to the measurement target to the diameter D of the measurement target is 1:6. That is, if the heat source diameter D is 20 cm, the distance from the measured object should preferably not exceed 120 cm. The larger K is, the higher the resolution. Therefore, the distance from 0 to 100 cm is equally divided at intervals of 5 cm, which are 1 cm, 5 cm, 10 cm......95 cm, 100 cm, a total of 21 temperature data. The true temperature is the temperature value measured by Pt100 under the same conditions. The relationship between the infrared temperature T and the distance parameter D is calculated by linear fitting of the collected data, so as to obtain the temperature compensation value To for the distance. Then it is programmed and downloaded in the processor according to the formula to obtain the corrected temperature value T. Figure 12 It is the data processing flow.

[0092] Through the embedded system technology and the relatively mature ZigBee technology, the design of the signal acquisition hardware part is completed. At the same time, the software part is designed by using IAR and the Z-Stack protocol stack based on CC2530. Finally, it is realized that the surface temperature can be accurately measured by infrared radiation, providing feasible support for the automatic measurement of ground temperature in comprehensive meteorological observation. At the same time, the present invention also has functions such as two-way communication and online upgrade. In the later stage, online calibration functions such as emissivity correction and distance correction are performed on the collected data through algorithms, meeting the specifications and requirements of refinement, intelligence, modernization, etc. for the surface temperature measurement, improving the working efficiency of infrared temperature measurement, and realizing scientific and information-based management of surface temperature measurement.

[0093] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A device for non-contact measurement of ground surface temperature, characterized in that: include: The optical system is arranged in front of the infrared temperature detector and is used to determine the sensor's field of view angle so that the infrared radiation energy is focused on the detector's absorption window; The infrared radiation detector uses the MLX90614 precision digital temperature measurement chip from Melexis, which is used to convert infrared energy into a weak voltage signal at the millivolt level, and control the temperature collection and processing process through the internal state machine, and then transmit the calculated temperature data via PWM or SMBus mode; A signal conditioning circuit, used for processing the voltage signal output by the infrared radiation detector; The main processor is used to perform analog-to-digital conversion, processing and temperature calculation on the signal after being processed by the signal conditioning circuit, and can realize the acquisition, analog-to-digital conversion, storage and data processing of analog signals, giving the sensor digital and intelligent characteristics; The communication module includes an RS-232 serial port and a ZigBee wireless communication module, which are used to realize the connection with the host computer and the transmission of data. The ZigBee wireless communication module is implemented by the CC2530 chip, and the RS-232 serial port communication part adopts the SN65C3232 chip to realize the conversion between the TTL level signal of the main control chip and the RS-232 signal; The status monitoring module is arranged on the processor and is used for real-time monitoring of the working process of the microprocessor.

2. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The sensor housing of the optical system is made of 3D printing technology, and is made of black wire material, which is light-shielding and non-reflective. The housing is a sealed cavity that can prevent rain and wind to ensure the normal operation of the sensor.

3. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The device also includes a collection baseboard, and the peripheral circuit of the collection baseboard includes: The CC2530 minimum system circuit includes a power supply part for supplying power to each device, a crystal oscillator part for providing clock frequency to the main chip CC2530F256, a reset part for restarting the software system, a download circuit for program download and debugging, and a radio frequency circuit for ZigBee wireless communication of the collected data in the later stage. The crystal oscillator is mainly composed of an external crystal oscillator with frequencies of 32MHz and 32.768KHz, and a capacitor filter circuit with filtering and decoupling functions is added to the circuit; The system power supply circuit is powered by 12V DC voltage. The input +12V DC voltage is reduced to 5V and -5V through a two-stage step-down circuit to power some chips that require 5 / -5V voltage, and then the 5V is reduced to 3.3V. The analog and digital power supplies are separated. The first-stage voltage conversion chip uses TI's TPS5430 chip, 12V to -5V uses TPS5430 chip, and -5V to -3.3V uses negative voltage adjustable output integrated voltage regulator chip LM137.

4. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The device also includes a temperature signal acquisition circuit, which is mainly composed of an infrared temperature signal acquisition part and a Pt100 platinum resistance reference temperature signal acquisition part. The infrared temperature signal acquisition part is realized by directly connecting the MLX90614 high-precision digital infrared detector to the IO pin of the main control chip.

5. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The device also includes an ultrasonic signal acquisition circuit, which uses an HC-SR04 ultrasonic sensor to collect distance data.

6. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The device also includes an external clock circuit, which is designed using a DS3231 chip, performs clock control through an I2C protocol, and is powered by a mixed power supply method of VCC3.3V and a CR1220 button battery. When there is an external power supply, the external power supply supplies power to Vbat, and when the external power supply is disconnected, BAT1 supplies power.

7. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The device also includes a FLASH storage circuit, and W25X32 is selected as an external storage unit to increase storage space, wherein CC2530F256 includes 8KB of RAM and 256KB of FLASH, the RAM mainly stores collected data, input variables, and intermediate results of operations, etc., and the FLASH is mainly used to store system constants, etc.

8. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The device also includes a data correction algorithm module, and the data correction algorithm module includes: The emissivity correction unit is used to correct the measured temperature according to the emissivity values ​​of different underlying surfaces. The MLX90614 calibrates the emissivity of the object to 1. The emissivity calibration coefficient is stored in 004h of the EEPROM. When the actual surface temperature is measured, the program is written to calculate the temperature data according to the emissivity value of the current underlying surface. Common underlying surfaces such as grass have an emissivity of 0.980, cement ground has an emissivity of 0.933, and soil has an emissivity of 0.

974. The distance compensation unit is used to compensate the collected temperature value according to the measured distance. The distance coefficient K of MLX90614 is 1:

6. The distance from 0-100cm is divided into equal distances with 5cm as the base. The relationship between the infrared temperature T and the distance parameter D is calculated by linear fitting to obtain the distance to temperature compensation value To, and then correct the temperature value T.

9. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The device also includes an OTA online upgrade module. When the OTA server sends an image upgrade request to the OTA client in the form of unicast or broadcast, the client is informed that a new image is available, and then determines whether the new image is available by querying the next image request and response message. After the firmware update request is successful, the client writes the received image to the specified Flash location. After the upgrade image is downloaded, the server responds to the "upgrade end" request, and the client enters the new firmware program according to the instructions.

10. The device for non-contact measurement of ground surface temperature according to claim 1, characterized in that: The main processor uses the CC2530F256 chip of Texas Instruments, which provides resources for ZigBee wireless transmission, and 256KB of FLASH flash memory provides space for the storage of TEDS.

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