Temperature sensor calibration system with variable reference end temperature

Abstract

The invention relates to a temperature sensor calibration system with variable reference end temperature, and belongs to the field of temperature sensors. Comprising a temperature sensor used for outputting a thermoelectromotive force and a voltage value; the filtering module is used for filtering the thermoelectromotive force and the voltage value and transmitting the thermoelectromotive force and the voltage value to the CPU; the CPU is used for sampling the thermoelectromotive force and the voltage value, obtaining a sensitivity calibration parameter and a quota resistance calibration parameter of the temperature sensor based on the sampled data, and judging whether the next round of test is carried out or not; the constant-voltage power supply is used for applying a fixed voltage; the quota resistor is used for forming a voltage division circuit with the thermistor; and the constant-temperature water tank is used for providing a constant-temperature source for the working end of the temperature sensor. According to the system, a high-precision temperature sensor calibration result can be obtained under the conditions that the resistance value precision of the rated resistor is not high and the temperature of the reference end is not fixed, and the problems that an existing temperature sensor calibration system is low in precision, high in cost, not easy to operate and difficult to apply and popularize in production and manufacturing are solved.

Description

Technical Field

[0001] The present invention relates to the field of temperature sensors, and in particular, to a temperature sensor calibration system with a variable reference end temperature. Background Art

[0002] With the continuous development of the semiconductor industry, temperature sensors are increasingly widely used. Correspondingly, higher and higher precision requirements are imposed on temperature sensors. Due to reasons such as manufacturing processes, the output of temperature sensors often has deviations and needs to be calibrated to improve its output accuracy. Therefore, a high-precision, low-cost, and easy-to-operate calibration system for temperature sensors has important research significance.

[0003] Currently, existing calibration systems for temperature sensors fix the temperature of the reference end, so that the thermoelectromotive force generated by the thermocouple only changes with the temperature of the working end, and calibrate the temperature output by the temperature sensor by measuring the thermoelectromotive force. However, the measured value of the thermoelectromotive force is usually very small. The thermoelectromotive force corresponding to a temperature difference of 100 degrees is only dozens or even more than a dozen millivolts. This means that a small measurement error will lead to a large calibration deviation. Moreover, in order to keep the reference end in a constant temperature environment, it is usually necessary to provide additional equipment to place the reference end in it, such as a container filled with ice-water mixture, an iron box with a water jacket, and a container filled with oil. This not only has a high cost but also is not easy to implement and is not suitable for popularization and application in production manufacturing. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a temperature sensor calibration system with a variable reference end temperature to solve the problems of low accuracy, high cost, difficult operation, and difficulty in popularization and application in production manufacturing of existing temperature sensor calibration systems.

[0005] The present invention provides a temperature sensor calibration system with a variable reference end temperature, and the system includes:

[0006] A temperature sensor, including pins 1 to 4. Pins 1 and 3 are used to output thermoelectromotive force, and a thermistor is connected in series between pins 2 and 4 to output a voltage value;

[0007] A filtering module, used to filter the thermoelectromotive force output by pins 1 and 3 of the temperature sensor and the voltage value output by pins 2 and 4 and transmit them to the CPU;

[0008] A CPU, used to sample the thermoelectromotive force and voltage value transmitted by the filtering module, obtain the sensitivity calibration parameter and the rated resistance calibration parameter of the temperature sensor based on the sampled data, and determine whether to perform the next round of testing based on the sensitivity calibration parameter;

[0009] A constant voltage power supply, used to apply a fixed voltage between pin 2 of the temperature sensor and the ground;

[0010] A fixed resistor, connected in series between pin 4 of the temperature sensor and ground, is used to form a voltage division circuit with the thermistor;

[0011] A constant temperature water bath, including a first temperature constant temperature water bath and a second temperature constant temperature water bath, is used to provide a constant temperature source for the working end of the temperature sensor.

[0012] Further, the CPU includes:

[0013] A data sampling module, including an A / D converter, is used to sample the thermoelectromotive force and voltage value transmitted by the filtering module, and send the sampled data to the data processing module;

[0014] A data processing module is used to obtain the sensitivity calibration parameter and the fixed resistor calibration parameter of the temperature sensor based on the received sampled data, fixed voltage value, fixed resistor resistance value, constant temperature water bath temperature value, R-T table of the thermistor, and thermocouple graduation table of the temperature sensor, and send the sensitivity calibration parameter and the fixed resistor calibration parameter to the judgment module;

[0015] A judgment module is used to judge the received sensitivity calibration parameter. If the difference between the sensitivity calibration parameter and the previous round is less than the threshold, the fixed resistor calibration parameter and the sensitivity calibration parameter obtained in this round are used as the final fixed resistor calibration parameter and sensitivity calibration parameter; otherwise, an updated fixed resistor resistance value is obtained based on the fixed resistor calibration parameter, and the updated fixed resistor resistance value is sent to the data processing module, and the next round of testing is carried out.

[0016] Further, when measuring the temperature of the object to be measured, the data processing module is also used to obtain the temperature of the working end of the temperature sensor, that is, the temperature of the object to be measured, based on the final fixed resistor calibration parameter, sensitivity calibration parameter, and the sampled data of the object to be measured received.

[0017] Further, the sensitivity calibration parameter is obtained by the following method:

[0018] Measure the first thermoelectromotive force of the working end of the temperature sensor at the first temperature, the first voltage value of the thermistor, the second thermoelectromotive force of its working end at the second temperature, and the second voltage value of the thermistor;

[0019] Based on the R-T table of the thermistor, fixed voltage, fixed resistor resistance value, temperature sensor sensitivity, first temperature, first thermoelectromotive force, first voltage value, second temperature, second thermoelectromotive force, and second voltage value, respectively obtain the first calculated thermoelectromotive force and first ideal thermoelectromotive force corresponding to the reference end and the first temperature, and the second calculated thermoelectromotive force and second ideal thermoelectromotive force corresponding to the second temperature;

[0020] The sensitivity calibration parameter is obtained based on the first calculated thermal electromotive force, the first ideal thermal electromotive force, the second calculated thermal electromotive force, and the second ideal thermal electromotive force.

[0021] Furthermore, the rated resistance calibration parameter is obtained by the following method:

[0022] Measure the first thermal electromotive force of the working end of the temperature sensor at the first temperature, the first voltage value of the thermistor, the second thermal electromotive force of its working end at the second temperature, and the second voltage value of the thermistor;

[0023] Based on the R-T table of the thermistor, the fixed voltage, the rated resistance value, the temperature sensor sensitivity, the first temperature, the first thermal electromotive force, the first voltage value, the second temperature, the second thermal electromotive force, and the second voltage value, respectively obtain the first calculated thermal electromotive force and the first ideal thermal electromotive force corresponding to the reference end at the first temperature, and the second calculated thermal electromotive force and the second ideal thermal electromotive force corresponding to the second temperature;

[0024] Based on the R-T table of the thermistor, the fixed voltage, the rated resistance value, the first voltage value, the second voltage value, the first temperature, the second temperature, the first calculated thermal electromotive force, and the second calculated thermal electromotive force, obtain the rated resistance calibration parameter.

[0025] Furthermore, the first and second calculated thermal electromotive forces of the reference end are obtained by the following method:

[0026] Based on the fixed voltage, the rated resistance value, the first voltage value, and the second voltage value, respectively obtain the first resistance value and the second resistance value of the thermistor;

[0027] Respectively obtain the temperatures corresponding to the first resistance value and the second resistance value of the reference end by querying the R-T table of the thermistor; based on the first temperature, the second temperature, the temperatures corresponding to the first resistance value and the second resistance value of the reference end, respectively obtain the first conversion temperature and the second conversion temperature of the working end when the reference end is at the first temperature;

[0028] Based on the first temperature, the temperature corresponding to the first resistance value of the reference end, the first thermal electromotive force, the first conversion temperature, the second temperature, the temperature corresponding to the second resistance value of the reference end, the second thermal electromotive force, and the second conversion temperature, respectively obtain the first and second calculated thermal electromotive forces of the reference end.

[0029] Furthermore, the first and second calculated thermal electromotive forces of the reference end are obtained by the following formula:

[0030]

[0031]

[0032] where V C1 is the first calculated thermal electromotive force, T'R1 is the first conversion temperature, T 1 is the first temperature, T R1 is the temperature corresponding to the reference end and the first resistance value, V C2 is the second calculated thermoelectromotive force, T' R2 is the second conversion temperature, T 2 is the second temperature, T R2 is the temperature corresponding to the reference end and the second resistance value.

[0033] Furthermore, the sensitivity calibration parameter is obtained through the following formula:

[0034]

[0035] where Q is the sensitivity calibration parameter, V T1 is the first ideal thermoelectromotive force, V T2 is the second ideal thermoelectromotive force.

[0036] Furthermore, the rated resistance calibration parameter is obtained through the following formula:

[0037]

[0038] P' n = P 1 * P 2 *......P n ,

[0039] where P' n is the final rated resistance calibration parameter for the nth round of testing, P n is the rated resistance calibration parameter obtained from the nth round of testing, Ω 1 is the resistance value of the thermistor corresponding to the reference end temperature being the calculated temperature, Ω 2 is the resistance value of the thermistor corresponding to the reference end temperature being the first temperature.

[0040] Furthermore, according to the thermocouple graduation table of the temperature sensor, the sensitivities of the temperature sensor at various temperatures are obtained, and the arithmetic mean of the sensitivities of the temperature sensor at various temperatures is taken to obtain the sensitivity of the temperature sensor.

[0041] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0042] 1. By considering the error between the measured thermoelectromotive force and the ideal thermoelectromotive force corresponding to the thermocouple graduation table of the temperature sensor through the sensitivity calibration parameter, the present invention does not require fixing the temperature of the reference end for calibration, reduces the cost of the calibration system, improves the calibration accuracy, and is easy to operate, making it suitable for popularization and application in production and manufacturing.

[0043] 2. The present invention takes into account the error introduced by inaccurate fixed resistor values through the fixed resistor calibration parameter, so there is no need for a high-precision fixed resistor, reducing the cost of the calibration equipment and improving the calibration accuracy.

[0044] 3. The present invention determines whether to enter the next round of testing by judging whether the sensitivity calibration parameter is the same as that in the previous round. The final fixed resistor calibration parameter and sensitivity calibration parameter are obtained through n rounds of testing. Therefore, accurate calibration parameters are obtained through iterative cycles, improving the calibration accuracy.

[0045] 4. The present invention realizes the automatic calibration of the temperature sensor through software, greatly reducing the calibration time and thus improving the calibration efficiency.

[0046] 5. When measuring the temperature of the object to be measured, the accurate temperature of the working end of the temperature sensor, that is, the accurate temperature of the object to be measured, can be obtained through the final fixed resistor calibration parameter, sensitivity calibration parameter, and the sampled data of the object to be measured received.

[0047] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages will be obvious from the description or can be understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained through the content specifically pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings are only for the purpose of showing specific embodiments and are not considered to be a limitation of the present invention. Throughout the drawings, the same reference signs represent the same components.

[0049] Figure 1 It is a block diagram of a temperature sensor calibration system with a variable reference end temperature according to an embodiment of the present invention;

[0050] Figure 2 It is a schematic circuit diagram of temperature sensor calibration according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] The preferred embodiments of the present invention will be specifically described below with reference to the drawings. The drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, not to limit the scope of the present invention.

[0052] A specific embodiment of the present invention discloses a temperature sensor calibration system with a variable reference end temperature. As Figure 1 shown, the system includes:

[0053] A temperature sensor, including pins 1 to 4. Pins 1 and 3 are used to output thermoelectromotive force, and a thermistor is connected in series between pins 2 and 4 to output a voltage value;

[0054] A filtering module, used to filter the thermoelectromotive force output by pins 1 and 3 of the temperature sensor and the voltage value output by pins 2 and 4 and transmit them to the CPU;

[0055] A CPU, used to sample the thermoelectromotive force and voltage value transmitted by the filtering module, obtain the sensitivity calibration parameter and the rated resistance calibration parameter of the temperature sensor based on the sampled data, and judge whether to perform the next round of testing based on the sensitivity calibration parameter;

[0056] A constant voltage power supply, used to apply a fixed voltage between pin 2 of the temperature sensor and the ground;

[0057] A rated resistance, connected in series between pin 4 of the temperature sensor and the ground, used to form a voltage dividing circuit with the thermistor;

[0058] A constant temperature water bath, including a first constant temperature water bath and a second constant temperature water bath, used to provide a constant temperature source for the working end of the temperature sensor.

[0059] Specifically, as Figure 2 shown, the temperature sensor is a non-contact temperature sensor. The voltage between pins 1 and 3 is the thermoelectromotive force generated by the temperature difference between the reference end and the working end of the temperature sensor, and the voltage between pins 2 and 4 is the voltage across the thermistor.

[0060] The filtering module eliminates signal noise through inductors and capacitors. It can be understood that the ground is connected to the negative pole of the constant voltage power supply. Factors such as constant voltage power supply fluctuations, ambient temperature changes, and electromagnetic interference can cause noise, and filtering can effectively suppress these noise interferences and improve the measurement accuracy and stability of the temperature sensor.

[0061] The rated resistance can also be connected in series between pin 2 and the ground, or between pin 2 and the positive pole of the constant voltage power supply, or between pin 4 and the positive pole of the constant voltage power supply.

[0062] The constant temperature water bath has an opening, and the working end of the temperature sensor is aligned with the opening of the constant temperature water bath to obtain its temperature. The temperatures of the first constant temperature water bath and the second constant temperature water bath are not equal, and the temperature difference between the two can cover the temperature measurement range.

[0063] Furthermore, the CPU includes:

[0064] A data sampling module, including an A / D converter, used to sample the thermoelectromotive force and voltage value transmitted by the filtering module and send the sampled data to the data processing module;

[0065] A data processing module, which is used to obtain the sensitivity calibration parameter and the rated resistance calibration parameter of the temperature sensor based on the received sampling data, fixed voltage value, rated resistance value, constant temperature water bath temperature value, R-T table of the thermistor, and thermocouple graduation table of the temperature sensor, and send the sensitivity calibration parameter and the rated resistance calibration parameter to the judgment module;

[0066] A judgment module, which is used to judge the received sensitivity calibration parameter. If the difference between the sensitivity calibration parameter and the previous round is less than the threshold, the rated resistance calibration parameter and the sensitivity calibration parameter obtained in this round are used as the final rated resistance calibration parameter and sensitivity calibration parameter; otherwise, an updated rated resistance value is obtained based on the rated resistance calibration parameter, the updated rated resistance value is sent to the data processing module, and the next round of testing is carried out.

[0067] Specifically, the data sampling module sets the sampling rate and sampling accuracy of the A / D converter, and converts the analog quantity into a digital quantity.

[0068] Furthermore, the sensitivity calibration parameter is obtained by the following method:

[0069] Measure the first thermal electromotive force of the working end of the temperature sensor at the first temperature, the first voltage value of the thermistor, the second thermal electromotive force of the working end at the second temperature, and the second voltage value of the thermistor;

[0070] Based on the R-T table of the thermistor, fixed voltage, rated resistance value, temperature sensor sensitivity, first temperature, first thermal electromotive force, first voltage value, second temperature, second thermal electromotive force, and second voltage value, respectively obtain the first calculated thermal electromotive force and the first ideal thermal electromotive force corresponding to the reference end and the first temperature, and the second calculated thermal electromotive force and the second ideal thermal electromotive force corresponding to the second temperature;

[0071] Obtain the sensitivity calibration parameter based on the first calculated thermal electromotive force, the first ideal thermal electromotive force, the second calculated thermal electromotive force, and the second ideal thermal electromotive force.

[0072] Specifically, during each round of testing, align the working end of the temperature sensor with the opening of the first temperature constant temperature water bath. The data sampling module measures the voltage between pins 1 and 3 of the temperature sensor, which is the first thermal electromotive force, and the voltage between pins 2 and 4, which is the first voltage value of the thermistor. Similarly, align the working end of the temperature sensor with the opening of the second temperature constant temperature water bath, and the data sampling module measures the second thermal electromotive force and the second voltage value of the thermistor.

[0073] It is understandable that when two different conductors or semiconductors are connected to each other at both ends to form a loop, one end is the working end and the other end is the reference end, and the loop is a thermocouple. As long as the temperatures of the working end and the reference end are different, a thermal electromotive force will be generated in the loop. The magnitude of this thermal electromotive force is related to the materials of the conductor or semiconductor and the temperatures of the working end and the reference end, and is independent of the shape and size of the loop. According to the functional relationship between the thermal electromotive force and the temperatures of the working end and the reference end, a thermocouple graduation table for a temperature sensor can be made. When the material of the thermocouple is fixed, the thermal electromotive force is the functional difference between the temperature of the working end and the temperature of the reference end. When measuring with a non-contact temperature sensor, the surface temperature of an object is measured by measuring the amount of infrared radiation emitted by the surface of the object. Therefore, the temperature at the entrance of the infrared rays into the temperature sensor is its working end temperature, and the ambient temperature inside it is its reference end temperature.

[0074] Preferably, the first constant temperature water bath is set at 25 degrees, the second constant temperature water bath is set at 37 degrees, the resistance value of the fixed resistor is 102 kΩ, and the fixed voltage is 2.45 volts.

[0075] Further, the first and second calculated thermal electromotive forces of the reference end are obtained by the following method:

[0076] Based on the fixed voltage, the resistance value of the fixed resistor, the first voltage value, and the second voltage value, the first resistance value and the second resistance value of the thermistor are obtained respectively;

[0077] By querying the R-T table of the thermistor, the temperatures corresponding to the reference end and the first resistance value and the second resistance value are obtained respectively; based on the first temperature, the second temperature, the temperatures corresponding to the reference end and the first resistance value and the second resistance value, the first conversion temperature and the second conversion temperature of the working end when the reference end is at the first temperature are obtained respectively;

[0078] Based on the first temperature, the temperature corresponding to the reference end and the first resistance value, the first thermal electromotive force, the first conversion temperature, the second temperature, the temperature corresponding to the reference end and the second resistance value, the second thermal electromotive force, and the second conversion temperature, the first and second calculated thermal electromotive forces of the reference end are obtained respectively.

[0079] Specifically, the first resistance value and the second resistance value of the thermistor are obtained by the following formula:

[0080]

[0081]

[0082] where, V 1 is the first voltage value, VS is the fixed voltage, R 1 is the first resistance value, R is the resistance value of the fixed resistor, V 2 is the second voltage value, R 2is the second resistance value.

[0083] Exemplarily, a constant temperature water bath of model RTS-0520 is selected. This type of water bath uses water bath type black body radiation, and the temperature accuracy is ±0.005 degrees. Set the first temperature of the constant temperature water bath to 25 degrees, the second temperature of the constant temperature water bath to 37 degrees, the resistance value of the rated resistor to 102 kΩ, and the fixed voltage to 2.45 volts. Assume that the accuracy of the rated resistor is low, and the actual resistance value is only 51 kΩ; moreover, the sensor sensitivity is not high, and the thermoelectromotive force measured at the same reference end temperature and working end temperature is only 1 / 5 of the thermoelectromotive force in the thermocouple graduation table of the temperature sensor.

[0084] Measure the constant temperature water bath at 25 degrees, and the first thermoelectromotive force between the working end and the reference end (temperature sensor pins 1 and 3) is -0.253771 mV, and the first voltage value across the thermistor is 1.250403 volts. Since the rated resistor and the thermistor are in series, it can be known from the equality of currents in the series circuit that:

[0085]

[0086] The first resistance value is calculated to be 106.319961 kΩ.

[0087] Measure the constant temperature water bath at 37 degrees, and the second thermoelectromotive force between the working end and the reference end is 0.276516 mV, and the second voltage value across the thermistor is 1.739209 volts. Similarly, it can be known that:

[0088]

[0089] The second resistance value is calculated to be 249.580141 kΩ.

[0090] The R-T table of the thermistor provided by the temperature sensor manufacturer is shown in Table 1. By querying Table 1 and using the linear interpolation method, the temperatures corresponding to the reference end and the first resistance value and the second resistance value are obtained as 23.61 degrees and 5.20 degrees respectively. That is, when the reference end temperature is 23.61 degrees, measuring the constant temperature water bath at 25 degrees, the first thermoelectromotive force obtained is -0.253771 mV; when the reference end temperature is 5.20 degrees, measuring the constant temperature water bath at 37 degrees, the second thermoelectromotive force obtained is 0.276516 mV.

[0091] Table 1 R-T table of the thermistor

[0092]

[0093] Based on the first temperature of 25 degrees and the temperature corresponding to the reference end and the first resistance value of 23.61 degrees, the difference between them is 1.39 degrees. Using 25 + 1.39, the first conversion temperature of the working end when the reference end is 25 degrees is obtained as 26.39 degrees; based on the second temperature of 37 degrees and the temperature corresponding to the reference end and the second resistance value of 5.20 degrees, the difference between them is 31.8 degrees. Using 25 + 31.8, the second conversion temperature of the working end when the reference end is 25 degrees is obtained as 56.8 degrees.

[0094] The thermocouple graduation table of the temperature sensor provided by the temperature sensor manufacturer is shown in Table 2.

[0095] Table 2 Thermocouple Graduation Table of Temperature Sensor

[0096]

[0097] It can be understood that in an ideal situation, the resistance value of the fixed resistor is accurate, and the sensitivity of the temperature sensor is consistent with that in Table 2. Then, the thermal electromotive force obtained by testing the fixed working end temperature at the corresponding reference end temperature is consistent with that in Table 2. In an actual situation, due to the inaccurate resistance value of the fixed resistor, the calculated first resistance value and second resistance value are inaccurate, resulting in inaccurate temperatures obtained by querying Table 1; moreover, since the distance between the working end and the reference end is very close, the temperature of the reference end is easily affected by the temperature of the working end, resulting in a change in the temperature of the reference end, thereby introducing a measurement error.

[0098] Furthermore, the first and second calculated thermal electromotive forces of the reference end are obtained through the following formula:

[0099]

[0100]

[0101] where, V C1 is the first calculated thermal electromotive force, T' R1 is the first conversion temperature, T 1 is the first temperature, T R1 is the temperature corresponding to the reference end and the first resistance value, V C2 is the second calculated thermal electromotive force, T' R2 is the second conversion temperature, T 2 is the second temperature, T R2 is the temperature corresponding to the reference end and the second resistance value.

[0102] Exemplarily, substituting the first voltage value, the first conversion temperature, the first temperature, and the temperature corresponding to the reference end and the first resistance value obtained above into the formula for the first calculated thermal electromotive force of the reference end, we can get: The calculated first calculated thermoelectromotive force is -0.257344 mV. That is, when the reference junction temperature is 25 degrees, for a constant temperature water bath with a measured temperature of 26.39 degrees, the obtained thermoelectromotive force is -0.257344 mV. Substituting the obtained second voltage value, second conversion temperature, second temperature, and the temperature corresponding to the reference junction and the second resistance value into the second calculated thermoelectromotive force formula for the reference junction, we can get: The calculated second calculated thermoelectromotive force is 0.336060 mV. That is, when the reference junction temperature is 25 degrees, for a constant temperature water bath with a measured temperature of 56.8 degrees, the obtained thermoelectromotive force is 0.336060 mV.

[0103] Furthermore, according to the thermocouple graduation table of the temperature sensor, the sensitivities of the temperature sensor at various temperatures are obtained, and the arithmetic mean of the sensitivities of the temperature sensor at various temperatures is taken to obtain the temperature sensor sensitivity.

[0104] Specifically, for a non-contact temperature sensor, applying the Stefan-Boltzmann law, the thermoelectromotive force between the working junction and the reference junction can be obtained through the following formula:

[0105] V out =K*[(T t +273.15) 4 -(T a +273.15) 4

[0106] Where K is the temperature sensor sensitivity, T t is the working junction temperature, and T a is the reference junction temperature.

[0107] According to Table 2, substituting the corresponding working junction temperature, reference junction temperature, and thermoelectromotive force into the above formula, the corresponding temperature sensor sensitivity can be obtained. Taking the arithmetic mean of the temperature sensor sensitivities at various temperatures, the temperature sensor sensitivity is 7.40161214290348E-10.

[0108] Specifically, the first and second ideal thermoelectromotive forces of the reference junction are obtained through the following formula:

[0109] V T1 =K*[(T' R1 +273.15) 4 -(T 1 +273.15) 4

[0110] V T2 =K*[(T' R2 +273.15) 4 -(T 1 +273.15)​​4 ,

[0111] wherein, V T1 is the first ideal thermal electromotive force, K is the sensitivity of the temperature sensor, and V T2 is the second ideal thermal electromotive force.

[0112] Exemplarily, substituting the sensitivity of the temperature sensor, the first temperature, and the first conversion temperature obtained above into the above formula, we can get:

[0113] V T1 = 7.40161214290348E-10 * [(26.39 + 273.15) 4 - (25 + 273.15) 4 , and calculating to obtain

[0114] the first ideal thermal electromotive force is 0.110631 mV; substituting the sensitivity of the temperature sensor, the second temperature, and the second conversion temperature obtained above into the above formula, we can get:

[0115] Calculating to obtain the second ideal thermal electromotive force is 2.923625 mV.

[0116] Furthermore, the sensitivity calibration parameter is obtained through the following formula:

[0117]

[0118] wherein, Q is the sensitivity calibration parameter, V T1 is the first ideal thermal electromotive force, and V T2 is the second ideal thermal electromotive force.

[0119] Exemplarily, in the first round of testing, substituting the first calculated thermal electromotive force, the first ideal thermal electromotive force, the second calculated thermal electromotive force, and the second ideal thermal electromotive force obtained above into the above formula, we can get: Calculating to obtain the sensitivity calibration parameter is 4.740437.

[0120] It can be understood that in the calibration model, it is considered that the calibration error changes linearly. Therefore, the linear error formula is used to obtain the sensitivity calibration parameter. The sensitivity calibration parameter is used to calibrate the error between the measured thermal electromotive force and the thermocouple graduation table of the temperature sensor. The present invention takes into account the error between the measured thermal electromotive force and the ideal thermal electromotive force corresponding to the thermocouple graduation table of the temperature sensor through the sensitivity calibration parameter. Therefore, it is not necessary to fix the temperature of the reference end for calibration, reducing the cost of calibration equipment, improving the calibration accuracy, and being easy to operate, which is suitable for popularization and application in production and manufacturing.

[0121] Furthermore, the fixed resistance calibration parameter is obtained through the following method:

[0122] Measure the first thermal electromotive force of the working end of the temperature sensor at the first temperature, the first voltage value of the thermistor, the second thermal electromotive force of its working end at the second temperature, and the second voltage value of the thermistor;

[0123] Based on the R-T table of the thermistor, the fixed voltage, the rated resistance value, the sensitivity of the temperature sensor, the first temperature, the first thermal electromotive force, the first voltage value, the second temperature, the second thermal electromotive force, and the second voltage value, respectively obtain the first calculated thermal electromotive force and the first ideal thermal electromotive force corresponding to the reference end and the first temperature, and the second calculated thermal electromotive force and the second ideal thermal electromotive force corresponding to the second temperature;

[0124] Based on the R-T table of the thermistor, the fixed voltage, the rated resistance value, the first voltage value, the second voltage value, the first temperature, the second temperature, the first calculated thermal electromotive force, and the second calculated thermal electromotive force, obtain the rated resistance calibration parameter.

[0125] Specifically, the methods for obtaining the first thermal electromotive force, the first voltage value, the second thermal electromotive force, and the second voltage value in the above steps are the same as those for the sensitivity calibration parameter, and will not be elaborated here.

[0126] Specifically, based on the fixed voltage, the rated resistance value, the first voltage value, and the second voltage value, respectively obtain the first resistance value and the second resistance value of the thermistor;

[0127] By querying the R-T table of the thermistor, respectively obtain the temperatures corresponding to the reference end and the first resistance value and the second resistance value; based on the first temperature, the second temperature, the temperatures corresponding to the reference end and the first resistance value and the second resistance value, respectively obtain the first conversion temperature and the second conversion temperature of the working end when the reference end is at the first temperature;

[0128] Based on the first calculated thermal electromotive force, the second calculated thermal electromotive force, the first conversion temperature, and the second conversion temperature, obtain the calculated temperature of the reference end;

[0129] By querying the R-T table of the thermistor, obtain the resistance value of the thermistor corresponding to the calculated temperature of the reference end and the resistance value of the thermistor corresponding to the first temperature of the reference end, and obtain the rated resistance calibration parameter through the ratio of the resistance values of the thermistor.

[0130] Specifically, the methods for obtaining the first resistance value and the second resistance value of the thermistor in the above steps, and the methods for obtaining the first conversion temperature and the second conversion temperature of the working end when the reference end is at the first temperature are the same as those for the sensitivity calibration parameter, and will not be elaborated here.

[0131] Specifically, the calculated temperature of the reference end is obtained through the following formula:

[0132]

[0133] Among them, T A is the calculated temperature of the reference end.

[0134] Exemplarily, substituting the first calculated thermoelectromotive force, the second calculated thermoelectromotive force, the first conversion temperature, and the second conversion temperature obtained above into the above formula, we can get: The calculated temperature of the reference end is calculated to be 40.672677.

[0135] It can be understood that the ideal value of T A should be 25 degrees, and the deviation between the actually obtained value and the ideal value is caused by the inaccurate resistance value of the fixed resistor.

[0136] Furthermore, the fixed resistor calibration parameter is obtained through the following formula:

[0137]

[0138] P' n = P 1 * P 2 *......P n ,

[0139] Among them, P' n is the final fixed resistor calibration parameter for the nth round of testing, P n is the fixed resistor calibration parameter obtained in the nth round of testing, Ω 1 is the resistance value of the thermistor corresponding to the reference end temperature being the calculated temperature, Ω 2 is the resistance value of the thermistor corresponding to the reference end temperature being the first temperature.

[0140] Exemplarily, in the first round of testing, by querying Table 1 and using the linear interpolation method, the resistance value of the thermistor corresponding to the reference end temperature being the calculated temperature of 40.672677 is 51.740654 kΩ, and the resistance value of the thermistor corresponding to the reference end temperature being the first temperature of 25 is 100 kΩ. Substituting 51.740654 and 100 into the above formula, we can get: The calculated fixed resistor calibration parameter is 0.517407.

[0141] In the nth round of testing, by multiplying the fixed resistor calibration parameters obtained from the first round to the nth round of testing, the final fixed resistor calibration parameter for the nth round of testing is obtained.

[0142] It can be understood that the fixed resistor calibration parameter is used to calibrate the error caused by the inaccurate resistance value of the fixed resistor. The present invention takes into account the error introduced by the inaccurate resistance value of the fixed resistor through the fixed resistor calibration parameter. Therefore, a high-precision fixed resistor is not required, the cost of the calibration equipment is reduced, and the calibration accuracy is improved.

[0143] Specifically, if the difference between the sensitivity calibration parameter and the previous round is less than the threshold value, the fixed resistor calibration parameter and the sensitivity calibration parameter obtained in this round are used as the final fixed resistor calibration parameter and sensitivity calibration parameter; otherwise, the fixed resistor value is multiplied by the final fixed resistor calibration parameter of this round of testing to obtain an updated fixed resistor value, i.e., R n = R * P 1 * P 2 *......P n , and the above method is repeated for the next round of testing based on the updated fixed resistor value. Preferably, the threshold value is set to 0.000001.

[0144] Exemplarily, after several rounds of testing, the final fixed resistor calibration parameter is 0.5 and the sensitivity calibration parameter is 5.

[0145] It can be understood that the present invention determines whether to enter the next round of testing by judging whether the sensitivity calibration parameter is the same as the previous round, and obtains the final fixed resistor calibration parameter and sensitivity calibration parameter through n rounds of testing. Therefore, accurate calibration parameters are obtained through cyclic iteration, improving the calibration accuracy. Moreover, the data acquisition and calculation processes in the present invention are all implemented by software, so the calibration of the temperature sensor is automated, greatly reducing the calibration time and thus improving the calibration efficiency.

[0146] Furthermore, the data processing module is also used to obtain the temperature of the working end of the temperature sensor, i.e., the temperature of the object to be measured, based on the final fixed resistor calibration parameter, the sensitivity calibration parameter, and the sampled data of the object to be measured received when measuring the temperature of the object to be measured.

[0147] Specifically, the thermal electromotive force of the temperature sensor and the resistance value of the fixed resistor are obtained through the following formula:

[0148]

[0149] Among them, V' is the adjusted thermal electromotive force, V is the measured thermal electromotive force, Q is the final sensitivity calibration parameter, R' is the adjusted fixed resistor value, R is the fixed resistor value, and P is the final fixed resistor calibration parameter.

[0150] Exemplarily, a constant temperature water bath at 25 degrees is used as the object to be measured for temperature measurement, and the thermal electromotive force between pins 1 and 3 of the temperature sensor is obtained as -0.253771 millivolts, and the voltage value between pins 2 and 4 is 1.250403 volts. Based on the final fixed resistor calibration parameter 0.5, sensitivity calibration parameter 5, fixed resistor value 102 kΩ, and fixed voltage 2.45 V obtained above, the adjusted thermal electromotive force is -1.268855 millivolts, and the adjusted fixed resistor value is 51 kΩ.

[0151] It can be known from the equality of the current in the series circuit that:

[0152]

[0153] Among them, R c is the resistance value of the adjusted thermistor. From the above formula, it can be obtained that R c is 53.16 kΩ. By querying the R-T table of the thermistor, it can be obtained that the temperature corresponding to 53.16 kΩ is 40 degrees, that is, the reference end temperature is 40 degrees.

[0154] Based on the temperature sensor sensitivity 7.40161214290348E-10 and the Stefan-Boltzmann law obtained from Table 2, the working end temperature T t is 25.00 degrees:

[0155]

[0156] It can be understood that when measuring the temperature of the object to be measured, the present invention can obtain the accurate temperature of the working end of the temperature sensor, that is, the accurate temperature of the object to be measured, through the final fixed resistance calibration parameter, the sensitivity calibration parameter, and the sampled data of the object to be measured received.

[0157] Compared with the prior art, the beneficial effects of the temperature sensor calibration system with variable reference end temperature provided by the present invention are as follows:

[0158] 1. The present invention takes into account the error between the measured thermoelectromotive force and the ideal thermoelectromotive force corresponding to the thermocouple graduation table of the temperature sensor through the sensitivity calibration parameter. Therefore, it is not necessary to calibrate by fixing the temperature of the reference end, which reduces the cost of the calibration system, improves the calibration accuracy, and is easy to operate, making it suitable for popularization and application in production and manufacturing.

[0159] 2. The present invention takes into account the error introduced by the inaccurate fixed resistance value through the fixed resistance calibration parameter. Therefore, it is not necessary to use a high-precision fixed resistance, which reduces the cost of the calibration equipment and improves the calibration accuracy.

[0160] 3. The present invention determines whether to enter the next round of testing by judging whether the sensitivity calibration parameter is the same as that in the previous round, and obtains the final fixed resistance calibration parameter and sensitivity calibration parameter through n rounds of testing. Therefore, accurate calibration parameters are obtained through cyclic iteration, which improves the calibration accuracy.

[0161] 4. The present invention realizes the automatic calibration of the temperature sensor through software, which greatly reduces the calibration time and thus improves the calibration efficiency.

[0162] 5. When measuring the temperature of the object to be measured, the present invention can obtain the accurate temperature of the working end of the temperature sensor, that is, the accurate temperature of the object to be measured, through the final fixed resistance calibration parameter, the sensitivity calibration parameter, and the sampled data of the object to be measured received.

[0163] Those skilled in the art can understand that all or part of the processes of implementing the methods of the above embodiments can be completed by instructing relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium. Among them, the computer-readable storage medium is a magnetic disk, an optical disk, a read-only memory, or a random access memory, etc.

[0164] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A temperature sensor calibration system with a variable reference - end temperature, characterized in that, the system includes: A temperature sensor, including pins 1 to 4. Pins 1 and 3 are used to output thermoelectromotive force, and a thermistor is connected in series between pins 2 and 4 to output a voltage value; A filtering module, used to filter the thermoelectromotive force output by pins 1 and 3 of the temperature sensor and the voltage value output by pins 2 and 4 and transmit them to the CPU; A CPU, used to sample the thermoelectromotive force and voltage value transmitted by the filtering module, obtain the sensitivity calibration parameter and the fixed - resistance calibration parameter of the temperature sensor based on the sampled data, and judge whether to perform the next round of testing based on the sensitivity calibration parameter; A constant - voltage power supply, used to apply a fixed voltage between pin 2 of the temperature sensor and the ground; A fixed resistor, connected in series between pin 4 of the temperature sensor and the ground, used to form a voltage - dividing circuit with the thermistor; A constant - temperature water bath, including a first constant - temperature water bath and a second constant - temperature water bath, used to provide a constant - temperature source for the working end of the temperature sensor.

2. The temperature sensor calibration system with a variable reference - end temperature according to claim 1, characterized in that, the CPU includes: A data sampling module, including an A / D converter, used to sample the thermoelectromotive force and voltage value transmitted by the filtering module and send the sampled data to the data processing module; A data processing module, used to obtain the sensitivity calibration parameter and the fixed - resistance calibration parameter of the temperature sensor based on the received sampled data, the fixed voltage value, the fixed - resistor resistance value, the constant - temperature water - bath temperature value, the R - T table of the thermistor, and the thermocouple graduation table of the temperature sensor, and send the sensitivity calibration parameter and the fixed - resistance calibration parameter to the judgment module; A judgment module, used to judge the received sensitivity calibration parameter. If the difference between the sensitivity calibration parameter and that of the previous round is less than the threshold value, then take the fixed - resistance calibration parameter and the sensitivity calibration parameter obtained in this round as the final fixed - resistance calibration parameter and sensitivity calibration parameter; otherwise, obtain an updated fixed - resistor resistance value based on the fixed - resistance calibration parameter, send the updated fixed - resistor resistance value to the data processing module, and perform the next round of testing.

3. The temperature sensor calibration system with a variable reference - end temperature according to claim 2, characterized in that, The data processing module is also used to obtain the temperature of the working end of the temperature sensor, i.e., the temperature of the object to be measured, based on the final fixed - resistance calibration parameter, the sensitivity calibration parameter, and the sampled data of the object to be measured when measuring the temperature of the object to be measured.

4. The temperature sensor calibration system with a variable reference - end temperature according to claim 2, characterized in that, The sensitivity calibration parameter is obtained by the following method: Measure the first thermoelectromotive force of the working end of the temperature sensor at the first temperature, the first voltage value of the thermistor, the second thermoelectromotive force of its working end at the second temperature, and the second voltage value of the thermistor; Based on the R-T table of the thermistor, the fixed voltage, the rated resistance value, the sensitivity of the temperature sensor, the first temperature, the first thermal electromotive force, the first voltage value, the second temperature, the second thermal electromotive force, and the second voltage value, the first calculated thermal electromotive force and the first ideal thermal electromotive force corresponding to the reference end and the first temperature, and the second calculated thermal electromotive force and the second ideal thermal electromotive force corresponding to the second temperature are obtained respectively; Based on the first calculated thermal electromotive force, the first ideal thermal electromotive force, the second calculated thermal electromotive force, and the second ideal thermal electromotive force, the sensitivity calibration parameter is obtained.

5. The temperature sensor calibration system with a variable reference end temperature according to claim 2, characterized in that, the rated resistance calibration parameter is obtained by the following method: The first thermal electromotive force of the working end of the temperature sensor at the first temperature, the first voltage value of the thermistor, the second thermal electromotive force of the working end at the second temperature, and the second voltage value of the thermistor are measured; Based on the R-T table of the thermistor, the fixed voltage, the rated resistance value, the sensitivity of the temperature sensor, the first temperature, the first thermal electromotive force, the first voltage value, the second temperature, the second thermal electromotive force, and the second voltage value, the first calculated thermal electromotive force and the first ideal thermal electromotive force corresponding to the reference end and the first temperature, and the second calculated thermal electromotive force and the second ideal thermal electromotive force corresponding to the second temperature are obtained respectively; Based on the R-T table of the thermistor, the fixed voltage, the rated resistance value, the first voltage value, the second voltage value, the first temperature, the second temperature, the first calculated thermal electromotive force, and the second calculated thermal electromotive force, the rated resistance calibration parameter is obtained.

6. The temperature sensor calibration system with a variable reference end temperature according to claim 4, characterized in that, the first and second calculated thermal electromotive forces of the reference end are obtained by the following method: Based on the fixed voltage, the rated resistance value, the first voltage value, and the second voltage value, the first resistance value and the second resistance value of the thermistor are obtained respectively; The temperatures corresponding to the reference end and the first resistance value and the second resistance value are obtained by querying the R-T table of the thermistor; Based on the first temperature, the second temperature, the temperatures corresponding to the reference end and the first resistance value and the second resistance value, the first conversion temperature and the second conversion temperature of the working end when the reference end is at the first temperature are obtained respectively; Based on the first temperature, the temperature corresponding to the reference end and the first resistance value, the first thermal electromotive force, the first conversion temperature, the second temperature, the temperature corresponding to the reference end and the second resistance value, the second thermal electromotive force, and the second conversion temperature, the first and second calculated thermal electromotive forces of the reference end are obtained respectively.

7. The temperature sensor calibration system with a variable reference end temperature according to claim 4, characterized in that, the first and second calculated thermal electromotive forces of the reference end are obtained by the following formula: Among them, V C1 is the first calculated thermoelectromotive force, T' R1 is the first conversion temperature, T 1 is the first temperature, T R1 is the temperature corresponding to the reference end and the first resistance value, V C2 is the second calculated thermoelectromotive force, T' R2 is the second conversion temperature, T 2 is the second temperature, T R2 is the temperature corresponding to the reference end and the second resistance value.

8. The temperature sensor calibration system with a variable reference end temperature according to claim 4, characterized in that, the sensitivity calibration parameter is obtained by the following formula: where Q is the sensitivity calibration parameter, V T1 is the first ideal thermoelectromotive force, V T2 is the second ideal thermoelectromotive force.

9. The temperature sensor calibration system with a variable reference end temperature according to claim 5, characterized in that, the rated resistance calibration parameter is obtained by the following formula: P' n = P 1 * P 2 *......P n , Among them, P' n is the final fixed-resistance calibration parameter for the nth round of testing, and P n is the fixed-resistance calibration parameter obtained from the nth round of testing, Ω 1 is the resistance value of the thermistor corresponding to the reference-end temperature being the calculated temperature, Ω 2 is the resistance value of the thermistor corresponding to the reference-end temperature being the first temperature.

10. The temperature sensor calibration system with a variable reference end temperature according to claim 4, characterized in that, The temperature sensor sensitivities at various temperatures are obtained according to the thermocouple graduation table of the temperature sensor, and the arithmetic mean of the temperature sensor sensitivities at various temperatures is taken to obtain the temperature sensor sensitivity.

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