Infrared temperature measurement sensor calibration method

Abstract

The invention discloses an infrared temperature measurement sensor calibration method, and the method comprises the steps: preferentially building a temperature and voltage corresponding relation of an infrared sensor of the same parameter type in the infrared temperature measurement sensor of the same parameter type; the calibration method comprises the following steps of: respectively carrying out two times of temperature measurement experiments on the infrared temperature measurement sensor to be calibrated, and recording the black body temperature and the environment temperature in the temperature measurement experiments; inquiring the voltage-temperature relation table of the parameter type by taking the blackbody temperature and the environment temperature as known quantities, and obtaining the theoretical voltage of each temperature measurement experiment; calculating the system coefficient of the infrared temperature measurement sensor to be calibrated based on the theoretical voltage and the measurement voltage in the corresponding temperature measurement experiment; according to the invention, rapid calibration of infrared temperature measurement sensors of the same parameter type is realized, full inspection of products of the same parameter type can be completed in an extremely short time, systematic risks are reduced, and calibration time and calibration cost are saved.

Description

Technical Field

[0001] This invention belongs to the field of infrared temperature measurement technology, and in particular relates to a calibration method for an infrared temperature sensor. Background Technology

[0002] Non-contact temperature measurement eliminates the need for direct contact with the object being measured, which is crucial for applications in certain special scenarios, such as temperature measurement and target detection in high-voltage, high-current electrical environments, high-temperature environments, or hazardous areas, as well as temperature measurement in areas with rapid temperature changes.

[0003] Infrared temperature sensors are highly sensitive to infrared radiation and can quickly respond to temperature changes in target objects. They can capture changes in the infrared radiation of the measured object in a very short time, which makes infrared sensors have fast response and high accuracy and reliability in automatic control and temperature monitoring systems.

[0004] Infrared temperature sensors require calibration before leaving the factory, typically using high-order curve fitting. Because infrared output is non-linear, calibration requires measuring multiple ambient and target temperature points to establish the sensor's high-order coefficients for better accuracy. However, this curve fitting method suffers from drawbacks: a large number of calibration points, low calibration efficiency due to long ambient temperature stabilization times, and high computational demands on subsequent processing units, all of which increase the production cost of infrared temperature sensors. Summary of the Invention

[0005] The purpose of this invention is to provide a calibration method for infrared temperature sensors. Compared with the calibration method of multi-point curve fitting, it reduces the number of ambient temperatures and target temperatures to be calibrated, thereby reducing the computational load and difficulty of the system.

[0006] This invention adopts the following technical solution: an infrared temperature sensor calibration method, which involves the following steps for calibrating infrared temperature sensors of the same parameter type: Two temperature measurement experiments were conducted on the infrared temperature sensor to be calibrated, and the blackbody temperature and ambient temperature were recorded during the temperature measurement experiments. Using the blackbody temperature and ambient temperature as known quantities, the voltage-temperature relationship table for this parameter type is consulted to obtain the theoretical voltage for each temperature measurement experiment; the voltage-temperature relationship table is established based on an infrared temperature sensor of the same parameter type. The system coefficients of the infrared temperature sensor to be calibrated are calculated based on the theoretical voltage and the measured voltage in the corresponding temperature measurement experiment.

[0007] The preferred method for establishing the voltage-temperature relationship table is as follows: Within the measurement range of the infrared temperature sensor, the blackbody temperature is kept constant while the ambient temperature is changed, and the measured voltage value of the infrared temperature sensor under different ambient temperature conditions is recorded. Within the measurement range of the infrared temperature sensor, the ambient temperature is kept constant while the blackbody temperature is changed, and the measured voltage values ​​of the infrared temperature sensor under different blackbody temperature conditions are recorded. A voltage-temperature relationship curve for this type of infrared sensor is constructed based on blackbody temperature, ambient temperature, and measured voltage value. Establish a voltage-temperature relationship table for this type of infrared sensor based on the voltage-temperature relationship curve.

[0008] Preferably, the voltage-temperature relationship table for this parameter type, using blackbody temperature and ambient temperature as known quantities, includes: Find the theoretical voltage corresponding to the blackbody temperature and reference temperature in the voltage-temperature relationship table.

[0009] Preferably, a hash algorithm is used to look up the theoretical voltage corresponding to the blackbody temperature and the reference temperature in the voltage-temperature relationship table.

[0010] Preferably, the ambient temperature remains constant in both temperature measurement experiments.

[0011] Preferred methods for calculating the system coefficients of the infrared temperature sensor to be calibrated include: , in, k The correlation value represents the system coefficient of the infrared temperature sensor to be calibrated. v 11 This represents the measured voltage value of the infrared temperature sensor in the first temperature measurement experiment. v 12 This indicates the measured voltage value of the infrared temperature sensor in the second temperature measurement experiment. V ( t 11 , t ref () represents the blackbody temperature in the first temperature measurement experiment. t 11 and reference temperature t ref The corresponding theoretical voltage, V ( t 12 , t ref () represents the blackbody temperature in the first temperature measurement experiment. t 12 and reference temperature t ref The corresponding theoretical voltage.

[0012] Preferably, the method for calculating the system coefficients of the infrared temperature sensor to be calibrated further includes: k = , in, Represents the Stefan-Boltzmann constant. This represents the radiant power per unit area of ​​a blackbody. h This represents the system coefficient of the infrared temperature sensor.

[0013] The beneficial effects of this invention are as follows: This invention establishes a voltage-temperature relationship table for infrared temperature sensors of the same parameter type based on multiple temperature measurement experiments of the same parameter type. Then, based on this table, two test experiments are conducted on other infrared temperature sensors of the same parameter type. This enables rapid calibration of infrared temperature sensors of the same parameter type to be calibrated. It can complete the full inspection of products of the same parameter type in a very short time, reduce systemic risks, and save calibration time and calibration costs. Attached Figure Description

[0014] Figure 1 This is a circuit diagram of the infrared conversion chip in an embodiment of the present invention; Figure 2 This is a flowchart of an infrared temperature sensor calibration method according to an embodiment of the present invention. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] Because of structural errors in the infrared temperature sensor (such as different distances between the sensor and the object being measured, resulting in the object not fully filling the sensor's field of view and introducing background temperature) or errors in the values ​​of components in the circuit, the intensity of infrared radiation received by the sensor from the object during the temperature measurement process will also change. The intensity of thermal radiation directly affects the magnitude of the sensor's voltage signal, and thus affects the final temperature detection.

[0017] This invention discloses a calibration method for infrared temperature sensors. For samples in infrared temperature sensors of the same parameter type, such as... Figure 2 As shown, the calibration is performed using the following steps: Two temperature measurement experiments are conducted on the infrared temperature sensor to be calibrated, and the blackbody temperature and ambient temperature are recorded during the experiments; the voltage-temperature relationship table for this parameter type is consulted using the blackbody temperature and ambient temperature as known quantities to obtain the theoretical voltage for each temperature measurement experiment; firstly, a voltage-temperature relationship table for infrared temperature sensors of the same parameter type is established; and the system coefficients of the infrared temperature sensor to be calibrated are calculated based on the theoretical voltage and the corresponding measured voltage in the temperature measurement experiment.

[0018] This invention establishes a voltage-temperature relationship table for infrared temperature sensors of the same parameter type based on multiple temperature measurement experiments of the same parameter type. Then, based on this table, two test experiments are conducted on other infrared temperature sensors of the same parameter type to be calibrated. This enables rapid calibration of infrared temperature sensors of the same parameter type to be calibrated. It can complete the full inspection of products of this parameter type in a very short time, reduce systemic risks, and save calibration time and calibration costs.

[0019] For infrared temperature sensors of the same parameter type, at least one infrared temperature sensor was selected to conduct experimental tests on its output voltage values ​​under different ambient temperatures and blackbody temperatures; a voltage-temperature relationship table for infrared temperature sensors of this parameter type was obtained and established.

[0020] It should be noted that since infrared temperature sensors of the same parameter type have the same component parameters and structural parameters, theoretically, their performance should also be the same. However, due to errors in component parameters, manufacturing processes, and installation, infrared sensors of the same parameter type may have slight variations in error. Therefore, calibrating infrared sensors of the same parameter type by establishing voltage-temperature curves will greatly reduce the number of calibration parameter points and calibration procedures, shorten calibration time, thereby improving calibration efficiency and reducing calibration costs.

[0021] Any object with a temperature above absolute zero emits infrared radiation, and its energy distribution is closely related to its surface temperature. As the surface temperature of a target object increases, its radiated energy also increases. The intensity of the radiated energy mainly depends on the object's shape, temperature, and the properties of its surface material. This is primarily reflected in the Stefan-Boltzmann theorem, the formula of which is as follows: (1) in, W Indicates infrared radiation energy. Let be the Stefan-Boltzmann constant, taken as 5.67 × 10⁻⁶. −8 W / (m 2 ⋅K 4 ), The radiated power per unit area of ​​a blackbody (W / m²) 2 ), The absolute temperature (K) of the target object.

[0022] The object being measured is the target of the measurement; all objects above absolute zero emit infrared radiation. The detection unit of an infrared temperature sensor consists of an infrared conversion chip and an internal ambient temperature detector. The infrared conversion chip detects the infrared radiation emitted by the object and converts it into a voltage signal of a corresponding proportion.

[0023] Infrared conversion chips are based on the Seebeck effect and consist of two different metals connected together. When the temperature changes, the two metals have different thermal effects, resulting in a thermoelectric electromotive force (EMF) between their cold and hot nodes. The magnitude of this EMF is proportional to the temperature. Since the generated EMF is the temperature difference between the cold and hot nodes, an internal ambient temperature detector is integrated to measure the temperature of the cold node. The hot node measures the temperature corresponding to the radiation intensity of the object being measured. Thus, the thermoelectric EMF of the object can be obtained from the temperature difference between the cold and hot nodes, allowing the calculation of the target's temperature.

[0024] like Figure 1 As shown, the sensor internally provides two analog signal voltage outputs. One output is the voltage corresponding to the thermal radiation of the object being measured by the thermopile. v 1. The other output is the voltage measured by the thermistor to measure the ambient temperature. v 2. Used for temperature compensation of the first signal. A 24-bit differential signal acquisition unit is used to acquire signals from both channels.

[0025] One of the channels is used for data acquisition of the small signal from the infrared detection unit, IN0 TP- and IN1 TP+, to obtain the differential signal. v 1. The signal output by the infrared detection unit is a small signal of μV / ℃, so a 24-bit differential acquisition unit is used to acquire the signals from the positive and negative terminals of the infrared conversion chip, where C31 and C32 are filter capacitors.

[0026] Another channel is used for data acquisition of internal ambient temperature, IN2 T+ and IN3 T-, with the differential voltage set to... v 2. R30 and R31 are voltage divider resistors, and the differential voltage across R31 is measured. v 2. The resistance RT of the ambient temperature detector can be obtained. The ambient temperature value can be obtained through the RT meter. RT = REFP * R31 / v 2-R30-R31. To reduce interference from external power supplies, the infrared sensor detection unit is powered by a regulated power supply and the ground wire is isolated from the digital ground. REFP is the positive terminal of the regulated power supply, REFN is the negative terminal of the regulated power supply, and T1 in the figure is the infrared sensor detection unit.

[0027] In one embodiment, the method for establishing the voltage-temperature relationship table is as follows: Within the measurement range of the infrared temperature sensor, keeping the blackbody temperature constant while changing the ambient temperature, record the measured voltage values ​​of the infrared temperature sensor of this parameter type under different ambient temperature conditions; within the measurement range of the infrared temperature sensor, keeping the ambient temperature constant while changing the blackbody temperature, record the measured voltage values ​​of the infrared temperature sensor of this parameter type under different blackbody temperature conditions; construct a voltage-temperature relationship curve for this parameter type based on the blackbody temperature, ambient temperature, and measured voltage values; and establish a voltage-temperature relationship table based on the voltage-temperature relationship curve. Thus, the voltage-temperature relationship table corresponding to this parameter type of infrared temperature sensor can be obtained.

[0028] When using multiple infrared temperature sensors of this parameter type to generate voltage-temperature relationship curves, multiple sets of data can be fitted to generate voltage-temperature relationship curves, and then a corresponding voltage-temperature relationship table can be generated based on the voltage-temperature relationship curves.

[0029] As a specific implementation, Table 1 below shows a set of example data for this invention. The temperature unit in the table is °C, and the voltage unit is mV. The table shows that when the blackbody temperature is 20 °C and the ambient temperature is 5 °C, the voltage value of the infrared temperature sensor is 1.069 mV.

[0030] Table 1 Regarding the ambient temperature, the voltage signal v2 measured by the thermistor can be converted into a resistance value. Then, the corresponding temperature value can be obtained by looking up the corresponding resistance value in a table. Thermistors are shipped with a corresponding resistance-temperature table, allowing the temperature value to be obtained by looking up the table based on the resistance value. Table 2 shows the resistance-temperature table corresponding to the platinum resistance thermometer PT1000 in this embodiment of the invention. For example, when the resistance value is 105.32Ω, the corresponding temperature value is -10℃.

[0031] Table 2 It should be noted that the data in Tables 1 and 2 of this invention are merely illustrative examples. In actual use, the number of data in the temperature and voltage tables needs to be designed according to the accuracy requirements of sensors of the same parameter type.

[0032] In the table lookup process of this invention, a hash algorithm is used to find the theoretical voltage corresponding to the blackbody temperature and reference temperature in the voltage-temperature relationship table. Specifically, to improve calibration efficiency and provide a fast response, a hash algorithm is introduced in the table lookup parsing part, enabling the results to be output quickly and accurately.

[0033] Generally, a definite correspondence function is established between the key and the storage location of the key-value pair. hash (), so that each key corresponds to a unique storage location in the structure, i.e. P [ hash ( key )]=& value In this context, a hash table is a key-value pair of data. P It is an array of pointers used to store the address of the value. hash () represents the corresponding functional relationship. Therefore, this method is very fast because it eliminates the need for multiple key comparisons, making it suitable for data organization and retrieval.

[0034] A simple hash The functional relationship can be replaced by a rounding function. The resistance value is rounded down to the nearest integer and used as the array index address. The corresponding temperature is then stored at the corresponding address. That is: hash ( key =ROUND(R) T ), where ROUND is the floor function, R T The values ​​in the table represent the resistance values. Given sufficient memory space, the algorithm is extremely efficient, meaning it has a high computational speed and can process large amounts of data in a short time. This efficiency gives hash algorithms a significant advantage when processing large datasets, resulting in a fast response time.

[0035] In this invention, the voltage signal of the thermopile (i.e., the element used to measure the object being measured) in the infrared temperature sensor... v 1. Due to the influence of ambient temperature, temperature compensation is required. This can be derived from the Stefan-Boltzmann theorem: (2) in, This represents the Stefan-Boltzmann constant, with a value of 5.67 × 10⁻⁶. −8 W / (m 2 ⋅K 4 ), This represents the radiant power per unit area of ​​a blackbody (W / m²). 2 ), This represents the system coefficients of the sensor. This indicates that the ambient temperature is The blackbody temperature is The output voltage at that time.

[0036] Furthermore, Equation 3 can be derived from Equation 2 based on the reference voltage: (3) in, At an ambient temperature of The blackbody temperature is Output voltage at that time At an ambient temperature of The blackbody temperature is Output voltage at that time In this embodiment, the standard reference temperature is represented as the ambient temperature.

[0037] Therefore, the voltage output based on the reference voltage at the target temperature can be obtained as follows: (4) because and It is a fixed constant, therefore The coefficients can be simplified and combined into correlation values. Formula 4 can be simplified to: (5) Therefore, it can be concluded that the voltage signal output of the thermopile... v 1. Even after system parameter restoration, it is still affected by ambient temperature and requires temperature compensation. The final voltage value after temperature compensation Finally, by consulting a table, the accurate temperature value of the object being measured can be obtained.

[0038] Furthermore, a fixed ambient temperature is set. And respectively change the blackbody temperature to and Formulas 6 and 7 can be obtained from Formula 3: (6) (7) Therefore, the methods for calculating the system coefficients of the infrared temperature sensor to be calibrated include: (8) in, k The correlation value represents the system coefficient of the infrared temperature sensor to be calibrated. v 11 This represents the measured voltage value of the infrared temperature sensor in the first temperature measurement experiment. v 12 This indicates the measured voltage value of the infrared temperature sensor in the second temperature measurement experiment. V ( t 11 , t ref () represents the blackbody temperature in the first temperature measurement experiment. t11 and reference temperature t ref The corresponding theoretical voltage, V ( t 12 , t ref () represents the blackbody temperature in the first temperature measurement experiment. t 12 and reference temperature t ref The corresponding theoretical voltage.

[0039] After obtaining the relevant values, the method for calculating the system coefficients of the infrared temperature sensor to be calibrated also includes: k = (9) The system coefficient of the infrared temperature sensor can be calculated using this formula. h .

[0040] Therefore, when the ambient temperature remains constant in the two temperature measurement experiments, looking up the voltage-temperature relationship table with the blackbody temperature and ambient temperature as known quantities includes: finding the theoretical voltage corresponding to the blackbody temperature and reference temperature in the voltage-temperature relationship table.

[0041] In summary, this invention discloses an easy-to-operate, low-cost, and highly reliable infrared temperature sensor and its calibration method. It features fast response, high sensitivity, good reliability, high production efficiency, and low cost. It can be applied to the measurement of object temperature, especially for objects with rapidly changing temperatures, high-voltage, high-current electrical components, and objects in high-temperature, moving, or hazardous areas.

[0042] The calibration method of the infrared temperature sensor of the present invention is used to correct the system coefficient of the infrared temperature sensor, so that infrared temperature sensors of the same parameter type can output consistent temperature detection signals after calibration, thereby enabling the infrared temperature sensor to measure the temperature value of the object being measured more accurately.

[0043] Based on the infrared sensor calibration method, a voltage-temperature table was established for infrared sensors of the same parameter type. The sensor was calibrated by changing the temperatures of two blackbody objects under the same ambient temperature. The calibrated sensor was then used to measure target objects with known temperatures under different ambient temperatures to verify the reliability and accuracy of the method. Specific experimental parameters are shown in Table 3.

[0044] Table 3 Where Tobj represents the temperature of the object being measured, in °C, with the target temperature ranging from 0 to 100 °C, and Tamb represents the ambient temperature, in °C, ranging from 0 to 80 °C. Infrared sensors calibrated using this method can achieve an accuracy within ±0.5 °C when measuring different target temperatures under varying ambient temperatures.

Claims

1. A calibration method for an infrared temperature sensor, characterized in that, For infrared temperature sensors of the same parameter type, the following steps are used for calibration: Two temperature measurement experiments were conducted on the infrared temperature sensor to be calibrated, and the blackbody temperature and ambient temperature were recorded during the temperature measurement experiments. Using the blackbody temperature and ambient temperature as known quantities, a voltage-temperature relationship table for this parameter type is consulted to obtain the theoretical voltage for each temperature measurement experiment; wherein, the voltage-temperature relationship table is established based on an infrared temperature sensor of the same parameter type; The system coefficients of the infrared temperature sensor to be calibrated are calculated based on the theoretical voltage and the corresponding measured voltage in the temperature measurement experiment.

2. The infrared temperature sensor calibration method as described in claim 1, characterized in that, The method for establishing the voltage-temperature relationship table is as follows: Within the measurement range of the infrared temperature sensor, the blackbody temperature is kept constant while the ambient temperature is changed, and the measured voltage value of the infrared temperature sensor under different ambient temperature conditions is recorded. Within the measurement range of the infrared temperature sensor, the ambient temperature is kept constant while the blackbody temperature is changed, and the measured voltage values ​​of the infrared temperature sensor under different blackbody temperature conditions are recorded. A voltage-temperature relationship curve for this type of infrared sensor is constructed based on blackbody temperature, ambient temperature, and measured voltage value. Establish a voltage-temperature relationship table for this type of infrared sensor based on the voltage-temperature relationship curve.

3. The infrared temperature sensor calibration method as described in claim 2, characterized in that, Using the blackbody temperature and ambient temperature as known quantities, the voltage-temperature relationship table for this parameter type includes: Find the theoretical voltage corresponding to the blackbody temperature and reference temperature in the voltage-temperature relationship table.

4. The infrared temperature sensor calibration method as described in claim 3, characterized in that, A hash algorithm is used to find the theoretical voltage corresponding to the blackbody temperature and the reference temperature in the voltage-temperature relationship table.

5. A calibration method for an infrared temperature sensor as described in claim 3 or 4, characterized in that, The ambient temperature remained constant in both temperature measurement experiments.

6. The infrared temperature sensor calibration method as described in claim 5, characterized in that, The methods for calculating the system coefficients of the infrared temperature sensor to be calibrated include: ， in, k The correlation value represents the system coefficient of the infrared temperature sensor to be calibrated. v 11 This represents the measured voltage value of the infrared temperature sensor in the first temperature measurement experiment. v 12 This indicates the measured voltage value of the infrared temperature sensor in the second temperature measurement experiment. V ( t 11 , t ref () represents the blackbody temperature in the first temperature measurement experiment. t 11 and reference temperature t ref The corresponding theoretical voltage, V ( t 12 , t ref () represents the blackbody temperature in the first temperature measurement experiment. t 12 and reference temperature t ref The corresponding theoretical voltage.

7. The infrared temperature sensor calibration method as described in claim 6, characterized in that, The methods for calculating the system coefficients of the infrared temperature sensor to be calibrated also include: k = ， in, Represents the Stefan-Boltzmann constant. This represents the radiant power per unit area of ​​a blackbody. h This represents the system coefficient of the infrared temperature sensor.

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