CN117433650A - Temperature detection circuit and device based on thermocouple - Google Patents
Temperature detection circuit and device based on thermocouple Download PDFInfo
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- CN117433650A CN117433650A CN202311393514.3A CN202311393514A CN117433650A CN 117433650 A CN117433650 A CN 117433650A CN 202311393514 A CN202311393514 A CN 202311393514A CN 117433650 A CN117433650 A CN 117433650A
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- G—PHYSICS
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- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
- G01K7/021—Particular circuit arrangements
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- G—PHYSICS
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- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
- G01K7/10—Arrangements for compensating for auxiliary variables, e.g. length of lead
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Abstract
The invention discloses a temperature detection circuit and a device based on a thermocouple, which relate to the detection field, wherein a compensation resistor is arranged close to the cold end of the thermocouple, and the resistance value of the compensation resistor is linearly related to the temperature, so that a processing module can determine the temperature of the cold end of the thermocouple through the voltage at two ends of the compensation resistor and the voltage at two ends of a reference resistor, and then the temperature detection process of a detected unit is realized according to the determined temperature of the cold end of the thermocouple and the pressure difference between the hot end and the cold end of the thermocouple; the temperature condition of the current thermocouple cold end is firstly determined through the compensation resistor, the actual cold end temperature is acquired in real time, and when the temperature of the measured unit is determined, the determined temperature of the current thermocouple cold end is used as a basis to determine the temperature of the measured unit, so that the problem that the acquisition accuracy of the thermocouple cold end is greatly influenced by the environmental temperature is avoided, the final temperature detection result is improved, and the accuracy and the reliability of the whole temperature detection circuit are ensured.
Description
Technical Field
The invention relates to the field of detection, in particular to a thermocouple-based temperature detection circuit and device.
Background
In fields such as industrial production, intelligent processing and wearable electronic equipment, the demand for temperature detection is increasing. The thermocouple is a temperature sensor which is commonly used in temperature measurement, has the main advantages of wider detection range, adaptation to various atmospheric environments, firmness, low price, no power supply and low cost. However, the magnitude of the thermoelectric voltage generated by the thermocouple is related to the temperature of the hot end of the thermocouple and the temperature of the cold end of the thermocouple, and the generated thermoelectric voltage can accurately reflect the temperature of the hot end only under the condition that the temperature of the cold end is constant. Because the distance between the cold end and the hot end of the thermocouple is relatively short, the temperature of the cold end is also greatly influenced by the temperature of a unit to be measured or the ambient temperature, so that the temperature of the cold end cannot be constant, and when the thermocouple is used for detecting the temperature, the influence of the temperature change of the cold end on a measurement result needs to be eliminated. How to avoid the influence of the temperature change of the cold end of the thermocouple on the detection result is a current urgent problem to be solved, and no effective means for solving the problem exists in the prior art.
Disclosure of Invention
The invention aims to provide a thermocouple-based temperature detection circuit and device, which are characterized in that the temperature condition of the current thermocouple cold end is firstly determined through a compensation resistor, the actual cold end temperature is acquired in real time, and the determined temperature of the current thermocouple cold end is used as a basis to determine the temperature of a unit to be detected when the temperature of the unit to be detected is determined, so that the problem that the acquisition accuracy of the thermocouple cold end is greatly influenced by the environmental temperature is avoided, the final temperature detection result is improved, and the accuracy and the reliability of the whole temperature detection circuit are ensured.
In order to solve the technical problems, the invention provides a thermocouple-based temperature detection circuit, which comprises a circuit board, a compensation resistor, a reference resistor and a processing module, wherein the compensation resistor, the reference resistor and the processing module are integrated on the circuit board;
the first input end of the processing module is connected with the cold end of the thermocouple, the second input end of the processing module is connected with the first end of the compensation resistor, the third input end of the processing module is respectively connected with the second end of the compensation resistor and the first end of the reference resistor, the second end of the reference resistor is grounded and is connected with the fourth input end of the processing module, the compensation resistor is arranged close to the cold end of the thermocouple, the first end of the compensation resistor is also connected with a power supply, and the resistance value of the compensation resistor is linearly related to the temperature;
the processing module is used for determining the temperature of the cold end of the thermocouple based on the voltage of the two ends of the compensation resistor and the voltage of the two ends of the reference resistor, determining the pressure difference between the hot end and the cold end of the thermocouple based on the cold end of the thermocouple, and determining the temperature of the unit to be measured based on the temperature of the cold end of the thermocouple and the pressure difference between the hot end and the cold end of the thermocouple.
Optionally, the thermocouple-based temperature detection circuit further comprises a first resistor, wherein a first end of the first resistor is connected with the power supply, and a second end of the first resistor is connected with the first end of the compensation resistor and a second input end of the processing module respectively.
Optionally, the thermocouple-based temperature detection circuit further comprises a second resistor, wherein a first end of the second resistor is connected with a second end of the reference resistor and a fourth input end of the processing module respectively, and a second end of the second resistor is grounded.
Optionally, the determining the temperature of the cold end of the thermocouple based on the voltage across the compensation resistor and the voltage across the reference resistor includes:
and determining the current resistance value of the compensation resistor based on the voltage at two ends of the compensation resistor and the voltage at two ends of the reference resistor, and determining the temperature corresponding to the current resistance value of the compensation resistor based on a resistance-temperature table of the compensation resistor, so as to take the temperature corresponding to the current resistance value of the compensation resistor as the temperature of the cold end of the thermocouple.
Optionally, the processing module includes an analog-to-digital conversion module and a processor, where a first analog input end of the analog-to-digital conversion module is used as a first input end of the processing module, a second analog input end is used as a second input end of the processing module, a third analog input end is used as a third input end of the processing module, a fourth analog input end is used as a fourth input end of the processing module, and an output end is connected with an input end of the processor.
Optionally, the processing module further includes a reference voltage source, where the reference voltage source is connected to a reference voltage port of the analog-to-digital conversion module, and the reference voltage port of the analog-to-digital conversion module is further connected to the first end of the compensation resistor.
Optionally, the thermocouple-based temperature detection circuit further includes a hollowed-out heat insulation belt disposed on the circuit board, and the hollowed-out heat insulation belt is used for separating the compensation resistor from other components on the circuit board.
In order to solve the technical problem, the invention also provides a thermocouple-based temperature detection device which comprises a thermocouple, a wiring terminal and the thermocouple-based temperature detection circuit, wherein the hot end of the thermocouple is connected with a unit to be detected through a detection probe, and the wiring of the cold end of the thermocouple is connected with the thermocouple-based temperature detection circuit through the wiring terminal.
Optionally, the temperature detection device further comprises a compensation wire, and the connection wire of the cold end of the thermocouple is connected with the connection terminal through the compensation wire.
Optionally, the compensation wire is the same type of wire as the connection of the cold end of the thermocouple.
The invention provides a temperature detection circuit based on a thermocouple, which comprises a circuit board, a compensation resistor, a reference resistor and a processing module, wherein the compensation resistor, the reference resistor and the processing module are integrated on the circuit board, the compensation resistor is arranged close to the cold end of the thermocouple, and the resistance value of the compensation resistor is linearly related to the temperature, so that the processing module can determine the temperature of the cold end of the thermocouple through the voltage at two ends of the compensation resistor and the voltage at two ends of the reference resistor, and then the temperature detection process of a detected unit is realized according to the determined temperature of the cold end of the thermocouple and the pressure difference between the hot end and the cold end of the thermocouple; the temperature condition of the current thermocouple cold end is firstly determined through the compensation resistor, the actual cold end temperature is acquired in real time, and when the temperature of the measured unit is determined, the determined temperature of the current thermocouple cold end is used as a basis to determine the temperature of the measured unit, so that the problem that the acquisition accuracy of the thermocouple cold end is greatly influenced by the environmental temperature is avoided, the final temperature detection result is improved, and the accuracy and the reliability of the whole temperature detection circuit are ensured.
The invention also provides a thermocouple-based temperature detection device, which has the same beneficial effects as the thermocouple-based temperature detection circuit.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the prior art and the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a thermocouple-based temperature detection circuit according to the present invention;
FIG. 2 is a schematic diagram of another thermocouple-based temperature sensing circuit according to the present invention;
fig. 3 is a schematic structural diagram of a thermocouple-based temperature detecting device according to the present invention.
Detailed Description
The invention has the core of providing a thermocouple-based temperature detection circuit and device, which firstly determines the temperature condition of the current thermocouple cold end through a compensation resistor, acquires the actual cold end temperature in real time, and uses the determined temperature of the current thermocouple cold end as a basis to determine the temperature of a unit to be detected when determining the temperature of the unit to be detected, thereby avoiding the problem that the acquisition accuracy of the thermocouple cold end is greatly influenced by the environmental temperature, improving the final temperature detection result and ensuring the accuracy and reliability of the whole temperature detection circuit.
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a thermocouple-based temperature detection circuit according to the present invention; referring to fig. 2, fig. 2 is a schematic structural diagram of another thermocouple-based temperature detection circuit according to the present invention; in order to solve the technical problems, the invention provides a temperature detection circuit based on a thermocouple 1, which comprises a circuit board 2, a compensation resistor R1, a reference resistor R2 and a processing module 21, wherein the compensation resistor R1, the reference resistor R2 and the processing module 21 are integrated on the circuit board 2;
the first input end of the processing module 21 is connected with the cold end of the thermocouple 1, the second input end of the processing module is connected with the first end of the compensation resistor R1, the third input end of the processing module is respectively connected with the second end of the compensation resistor R1 and the first end of the reference resistor R2, the second end of the reference resistor R2 is grounded and is connected with the fourth input end of the processing module 21, the compensation resistor R1 is arranged close to the cold end of the thermocouple 1, the first end of the compensation resistor R1 is also connected with a power supply, and the resistance value of the compensation resistor R1 is linearly related to the temperature;
the processing module 21 is configured to determine a temperature of the cold end of the thermocouple 1 based on the voltage across the compensation resistor R1 and the voltage across the reference resistor R2, determine a pressure difference between the hot end and the cold end of the thermocouple 1 based on the cold end of the thermocouple 1, and determine a temperature of the unit under test based on the temperature of the cold end of the thermocouple 1 and the pressure difference between the hot end and the cold end of the thermocouple 1.
It should be noted that, the thermocouple 1 is a closed loop formed by two different conductive materials or semiconductor materials a and B, where the thermocouple 1 has two ends, one end is at a temperature T1, referred to as a working end or a hot end, the other end is at a temperature T0, referred to as a free end, a reference end or a cold end, when the two ends are connected to each other, an electromotive force is generated in the loop as long as the temperatures at the connection points are different, the direction and the magnitude of the electromotive force are only related to the material of the conductors and the temperature at the two connection points, this phenomenon is called a thermoelectric effect, and the loop formed by two conductors or semiconductors is called a thermocouple 1, and the electromotive force generated by the two conductors or semiconductors is called a thermoelement. In the practical use process, the hot end is used as a testing end and is arranged at the tested unit, usually in a heat source, and the cold end is usually arranged at room temperature, but the room temperature is usually different to a certain extent under the influence of the use environment and the region, so that the cold end of the thermocouple 1 can be normally used only by corresponding compensation. The temperature detection circuit based on the thermocouple 1 provided by the invention can compensate the cold end of the thermocouple 1 in the temperature detection process, has a simple structure and high compensation precision, can collect the cold end temperature in real time, and is suitable for application in multiple scenes.
Specifically, in the process of using the thermocouple 1 to detect the temperature, the current temperature of the cold end of the thermocouple 1 is determined according to the voltage at both ends of the compensation resistor R1 and the voltage at both ends of the reference resistor R2, the reference resistor R2 is usually a fixed resistor, the compensation resistor R1 is a component such as a thermistor, the resistance value of which changes along with the change of the ambient temperature, so when the external temperature changes, the ratio of the voltage at both ends of the compensation resistor R1 to the voltage at both ends of the reference resistor R2 also changes, at this time, the ambient temperature around the compensation resistor R1 can be determined according to the voltage at both ends of the compensation resistor R1 and the voltage at both ends of the reference resistor R2, and meanwhile, since the compensation resistor R1 is set near the cold end of the thermocouple 1, that is, the ambient temperature around the compensation resistor R1 can represent the temperature T0 of the cold end of the thermocouple 1, thereby realizing real-time acquisition of the temperature of the cold end of the thermocouple 1, after the current temperature T0 of the cold end of the thermocouple 1 is determined, the temperature of the thermocouple 1 is acquired through the cold end of the thermocouple 1 and the voltage difference generated between the cold end of the thermocouple 1 and the thermocouple 1.
It will be understood that, according to the operating principle of thermocouple 1, absolute voltage E (t, 0) at the hot end, differential pressure E (t, t 0) between the hot end and the cold end, and absolute voltage E (t 0, 0) at the cold end have the following relationship:
E(t,0)＝E(t,t0)+E(t0,0)；
the pressure difference between the hot end and the cold end, that is, the pressure difference obtained by the processing module 21 through the cold end of the connected thermocouple 1, the absolute voltage of the cold end can be obtained according to the temperature T0 of the cold end and the voltage-temperature meter of the thermocouple 1, and the absolute voltage of the hot end can be obtained by calculation through the relationship, and at the moment, the temperature of the hot end, that is, the temperature of the detected unit is obtained through the voltage-temperature meter of the thermocouple 1.
It can be understood that a filtering module can be additionally arranged at the front side of each input end of the processing module 21, so that signals collected by the thermocouple 1, signals such as voltages at two ends of the compensation resistor R1 and voltages at two ends of the reference resistor R2 are filtered and then output to the processing module 21, the accuracy of the signals is further improved, and the accuracy and reliability of a final detection result are ensured; the specific types and implementations of the compensation resistor R1, the reference resistor R2, and the processing module 21 are not particularly limited herein, and the compensation resistor R1 is typically implemented by a thermistor or other type of thermistor, and the reference resistor R2 is typically implemented by a fixed resistor. The specific implementation manner, packaging manner, etc. of the circuit board 2 are not particularly limited herein, and may be adjusted and set according to actual application conditions. In practical application, the closer the compensation resistor R1 is to the setting position of the cold end of the thermocouple 1, the closer the temperature of the cold end of the thermocouple 1 determined by using the compensation resistor R1 is to the actual temperature of the cold end of the thermocouple 1, the more the accuracy and reliability of the finally detected temperature can be ensured, and the position of the compensation resistor R1 can be set as close to the cold end of the thermocouple 1 as possible according to the practical application situation.
Specifically, the cold end of the thermocouple 1 is connected to the first input end of the processing module 21, and the signal collected by the thermocouple 1 is output to the processing module 21 through the first input end, taking fig. 2 as an example, TC in fig. 2 is a sensor of the thermocouple 1, and mainly collects a temperature signal of the hot end, and can convert the temperature signal into a voltage small signal so as to enter an ADC (Analog-to-Digital Converter) channel for conversion. The signals collected by the thermocouple 1 directly enter analog channels AIN0 and AIN1 of an ADC in the processing module 21, and are subjected to ADC conversion after internal gain amplification, so that a pressure difference E (t, t 0) between the hot end and the cold end is obtained; at the same time, the high-precision reference resistor consists of an external reference voltage source U, a first resistor R3, a second resistor R4, a compensation resistor R1 and a high-precision reference resistor R2The cold end compensation circuit of the thermocouple (1) can acquire the temperature of the cold end of the thermocouple in real time; the four resistors of the first resistor R3, the second resistor R4, the compensating resistor R1 and the reference resistor R2 are connected in series, the reference voltage source U is used as a power supply, the four resistors are used for dividing voltage, the voltage V1 at two ends of the compensating resistor R1 is collected through the channels AIN2 and AIN3 of the ADC, the voltage V2 at two ends of the reference resistor R2 is collected through AIN3 and AIN4, and the resistance value of the compensating resistor R1 is set to be R X The resistance value of the reference resistor R2 is R 2 Then:from this, R can be calculated X Is the value of (1): />The temperature T0 of the cold end at the moment can be obtained by searching the resistor-thermometer corresponding to the compensation resistor R1, then the voltage-thermometer of the thermocouple 1 is searched, the absolute voltage E (T0, 0) of the cold end can be obtained, at the moment, the absolute voltage E (T, 0) of the hot end can be calculated through the method, and the voltage-thermometer of the thermocouple 1 is searched again, so that the final temperature T1 of the hot end can be obtained.
It can be understood that the cold end compensation scheme of the thermocouple 1 solves the problem that the cold end acquisition precision is greatly influenced by the ambient temperature in the prior art, the compensation resistor R1 and the cold end of the thermocouple 1 are positioned in the same temperature environment, and the actual cold end temperature can be acquired in real time through the compensation resistor R1; the whole circuit has simple structure and high compensation precision, and can carry out independent and accurate compensation on each acquisition channel; the process of collecting and converting the channel of the thermoelectromotive force generated by the thermocouple 1 and the process of carrying out cold end compensation by utilizing the compensation resistor R1 can adopt the same processing module and even the same ADC, thereby realizing the real-time collection of the cold end temperature, and the whole sensor has small packaging volume of the adopted element, is convenient for layout and has low cost.
Specifically, taking fig. 2 as an example, the compensation resistor R1 may be PT1000, where the temperature coefficient of PT1000 is relatively large and is 3.85 Ω/°c, so that an acquisition error of the compensation resistor R1 caused by the trace impedance inside the PCB (Printed Circui t Board ) may be reduced; the compensation resistor R1 can be packaged by adopting the SMD1206, and the self-heating coefficient of the compensation resistor R1 is smaller, so that the influence of self-heating on the acquisition precision can be reduced. The reference resistor R2 is usually a high-precision low-temperature-drift precision resistor, and can be realized by selecting a temperature-drift resistor with the precision of one ten thousandth and 5 ppm. The smaller the temperature drift of the reference resistor R2, the smaller the influence of the temperature on the reference resistor R2, and the higher the accuracy of the temperature of the cold end of the thermocouple 1 obtained based on the compensation resistor R1, so that the resistor with smaller temperature drift can be selected as the reference resistor R2 according to the actual application situation.
The invention provides a temperature detection circuit based on a thermocouple 1, which comprises a circuit board 2, a compensation resistor R1, a reference resistor R2 and a processing module 21, wherein the compensation resistor R1, the reference resistor R2 and the processing module 21 are integrated on the circuit board 2, the compensation resistor R1 and the cold end of the thermocouple 1 are arranged close to each other, and the resistance value of the compensation resistor R1 is in linear correlation with the temperature, so that the processing module 21 can determine the temperature of the cold end of the thermocouple 1 through the voltage of the two ends of the compensation resistor R1 and the voltage of the two ends of the reference resistor R2, and then realize the temperature detection process of a detected unit according to the determined temperature of the cold end of the thermocouple 1 and the pressure difference between the hot end and the cold end of the thermocouple 1; the temperature condition of the cold end of the current thermocouple 1 is firstly determined through the compensation resistor R1, the actual cold end temperature is acquired in real time, and when the temperature of a unit to be detected is determined, the determined temperature of the cold end of the current thermocouple 1 is used as a basis to determine the temperature of the unit to be detected, so that the problem that the acquisition accuracy of the cold end of the thermocouple 1 is greatly influenced by the environmental temperature is avoided, the final temperature detection result is improved, and the accuracy and the reliability of the whole temperature detection circuit are ensured.
Based on the above embodiments: referring to fig. 3, fig. 3 is a schematic structural diagram of a thermocouple-based temperature detecting device according to the present invention.
As an alternative embodiment, the temperature detection circuit based on thermocouple 1 further comprises a first resistor R3, a first end of the first resistor R3 being connected to the power supply, and a second end being connected to the first end of the compensation resistor R1 and to the second input of the processing module 21, respectively.
It is easy to understand that a first resistor R3 connected between the power supply and the compensation resistor R1 can be added in the circuit, the first resistor R3 is connected in series in the circuit to play roles of current limiting and voltage dividing, the magnitude of current on the series circuit can be further limited, and the influence of self-heating of the compensation resistor R1 on the cold end temperature acquisition precision can be further reduced by reducing the current. Meanwhile, the first resistor R3 can also avoid direct impact of large voltage possibly existing in the power supply on the compensation resistor R1, so that the circuit is further protected. The specific type and implementation of the first resistor R3 are not particularly limited herein, and a fixed resistor with ordinary precision may be generally used.
Specifically, the current flowing through the compensation resistor R1 can be further reduced by further increasing the first resistor R3 connected in series in the circuit where the compensation resistor R1 is located, so that the influence of the self-heating of the compensation resistor R1 on the determined temperature of the cold end is further avoided, the accuracy and the reliability of the detection result of the whole temperature detection circuit are further improved, and the adopted components are simple in structure, easy to realize, low in cost and small in size, and are beneficial to the simple and convenient realization of the whole temperature detection circuit.
As an alternative embodiment, the temperature detection circuit based on thermocouple 1 further comprises a second resistor R4, the first end of the second resistor R4 being connected to the second end of the reference resistor R2 and the fourth input of the processing module 21, respectively, and the second end being grounded.
It is to be understood that a second resistor R4 connected between the reference resistor R2 and the ground can be added in the circuit, the second resistor R4 is connected in series in the circuit, and plays roles of current limiting and voltage dividing, the magnitude of current on the series circuit can be further limited, the influence of self-heating of the compensation resistor R1 on the cold end temperature acquisition precision can be further reduced by reducing the current, the working current of the compensation resistor R1 is satisfied by the current flowing through the compensation resistor R1, and the smaller the better. Meanwhile, the second resistor R4 can also divide voltage to further protect the circuit. The specific type and implementation of the second resistor R4 are not particularly limited herein, and a fixed resistor with ordinary precision may be generally used.
Specifically, the current flowing through the compensation resistor R1 can be further reduced by further increasing the second resistor R4 connected in series in the circuit where the compensation resistor R1 is located, so that the influence of the self-heating of the compensation resistor R1 on the determined temperature of the cold end is further avoided, the accuracy and the reliability of the detection result of the whole temperature detection circuit are further improved, and the adopted components are simple in structure, easy to realize, low in cost and small in size, and are beneficial to the simple and convenient realization of the whole temperature detection circuit.
As an alternative embodiment, determining the temperature of the cold end of thermocouple 1 based on the voltage across compensation resistor R1 and the voltage across reference resistor R2, comprises:
the current resistance of the compensation resistor R1 is determined based on the voltage at two ends of the compensation resistor R1 and the voltage at two ends of the reference resistor R2, and the temperature corresponding to the current resistance of the compensation resistor R1 is determined based on a resistance-temperature table of the compensation resistor R1, so that the temperature corresponding to the current resistance of the compensation resistor R1 is used as the temperature of the cold end of the thermocouple 1.
It will be understood that after the voltage at both ends of the compensation resistor R1 and the voltage at both ends of the reference resistor R2 are obtained, the processing module 21 may determine the current resistance value of the compensation resistor R1 according to the current two voltage conditions and the fixed resistance value of the reference resistor R2, where the resistance value of the compensation resistor R1 may change along with the change of the temperature of the environment where the compensation resistor R1 is located, so that the processing module 21 may obtain the current temperature of the environment where the compensation resistor R1 is located by using the resistance-temperature table of the compensation resistor R1, thereby obtaining the current temperature of the cold end of the thermocouple 1. The resistance-thermometer of the compensation resistor R1 can be determined according to the specific type of the compensation resistor R1 adopted in practical application, the closer the compensation resistor R1 is to the setting position of the cold end of the thermocouple 1, the closer the temperature of the cold end of the thermocouple 1 determined by using the compensation resistor R1 is to the actual temperature of the cold end of the thermocouple 1, the more the accuracy and reliability of the finally detected temperature can be ensured, and the position of the compensation resistor R1 can be set as close to the cold end of the thermocouple 1 as possible according to practical application conditions.
Specifically, the characteristic that the resistance of the compensation resistor R1 changes along with the temperature is utilized, so that the temperature of the cold end of the thermocouple 1 is represented through the resistance of the compensation resistor R1, the real-time acquisition of the temperature of the cold end of the thermocouple 1 is realized, the accuracy and the reliability of the temperature of a unit to be detected by the thermocouple 1 are ensured, and the accuracy of the application process of the thermocouple 1 is ensured.
As an alternative embodiment, the processing module 21 comprises an analog-to-digital conversion module and a processor, wherein a first analog input of the analog-to-digital conversion module is used as a first input of the processing module 21, a second analog input is used as a second input of the processing module 21, a third analog input is used as a third input of the processing module 21, a fourth analog input is used as a fourth input of the processing module 21, and an output is connected to an input of the processor.
It is to be understood that the thermoelectromotive force output by the thermocouple 1 and the voltage signals at two ends of the compensation resistor R1 and the reference resistor R2 are analog signals, so that an analog-to-digital conversion module is required to be set in the processing module 21 to perform an analog-to-digital conversion process, and after the analog signals are converted into digital signals by the ADC, the converted digital signals are reported to the MCU (Micro Control ler Unit, micro control unit) or other types of processors through the SPI (Serial Peripheral interface) bus or other communication modes, and the MCU performs a series of operations such as table look-up, calculation and the like on the converted digital signals to obtain the temperature value of the final measured unit. The specific types and implementation modes of the analog-to-digital conversion module and the processor are not particularly limited, the sigma-delta type ADC is more accurate when measuring the analog quantity of the temperature, the effective bit number of the type of ADC is higher, the sampling rate is lower, and the analog quantity measuring device is suitable for measuring the temperature; the analog-to-digital conversion module may therefore employ a sigma-delta ADC to collect the TC-channel side voltage and the cold-side compensation channel voltage.
Specifically, considering that the signal received by the processing module 21 is generally an analog signal, the processing module 21 is provided with an analog-to-digital conversion module to perform the analog-to-digital conversion process, and the processor is used to implement operations such as calculating the converted digital signal, so that the structure of the processing module 21 is further clarified, which is beneficial to setting and application of the whole temperature detection device.
As an alternative embodiment, the processing module 21 further comprises a reference voltage source U connected to a reference voltage port of the analog-to-digital conversion module, which is further connected to the first end of the compensation resistor R1.
It is easy to understand that the reference voltage port of the analog-to-digital conversion module is usually externally connected with an external high-precision reference voltage source U, so that the reference voltage source U provides precise reference voltage for the ADC, and the acquisition accuracy is ensured; therefore, the power supply connected with the compensation resistor R1 can also be directly realized by using the reference voltage source U, the first end of the compensation resistor R1 can be directly connected with the reference voltage port of the analog-digital conversion module, and the power supply is realized by adopting the reference voltage source U of the analog-digital conversion module. The specific type and implementation of the reference voltage source U are not particularly limited herein, and the value of the power supply voltage can be selected and adjusted according to the actual application situation. As shown in fig. 2, AIN0 and AIN1 are the first analog input terminals of the analog-to-digital conversion module, AIN2 is the second analog input terminal of the analog-to-digital conversion module, AIN3 is the third analog input terminal of the analog-to-digital conversion module, AIN4 is the fourth analog input terminal of the analog-to-digital conversion module, and ref+ and REF-are the reference voltage ports of the analog-to-digital conversion module.
Specifically, the power supply required by the compensation resistor R1 can be realized by directly multiplexing the reference voltage source U of the analog-to-digital conversion module, so that the cost required by the whole temperature detection circuit is further saved, the volume of the whole temperature detection circuit is reduced, and the packaging of the circuit board 2 and the simple and convenient realization of the whole temperature detection circuit are facilitated.
As an alternative embodiment, the temperature detection circuit based on the thermocouple 1 further comprises a hollowed-out heat insulation belt 11 arranged on the circuit board 2, and the hollowed-out heat insulation belt 11 is used for separating the compensation resistor R1 from other components on the circuit board 2.
It will be understood that in the aspect of the layout of the PCB, as shown in fig. 3, in order to ensure the accuracy of the collected actual cold end temperature, to further reduce the collection error, a hollowed-out processing may be performed on the PCB to form a hollowed-out heat insulation belt 11, to separate the compensation resistor R1 from other components in the PCB, and meanwhile, the projection of the PCB below the compensation resistor R1 may not be subjected to copper plating processing, so as to reduce the influence of the temperature rise of the PCB on the cold end temperature to the greatest extent. The specific arrangement mode of the hollowed-out heat insulation tape 11 is not particularly limited herein, and may be set according to the circuit layout on the circuit board 2 in practical application.
Specifically, the hollowed-out heat insulation belt 11 for separating the compensation resistor R1 from other components in the board can be additionally arranged, so that the influence of the temperature change of the circuit board 2 on the temperature of the environment where the compensation resistor R1 is located is reduced as much as possible, the accuracy of the temperature of the cold end acquired by the compensation resistor R1 is further improved, and the accuracy and reliability of the temperature of the finally obtained measured unit are ensured.
In order to solve the technical problems, the invention also provides a temperature detection device based on the thermocouple 1, which comprises the thermocouple 1, a wiring terminal 12 and the temperature detection circuit based on the thermocouple 1, wherein the hot end of the thermocouple 1 is connected with a unit to be detected through a detection probe, and the wiring of the cold end of the thermocouple 1 is connected with the temperature detection circuit based on the thermocouple 1 through the wiring terminal 12.
It will be understood that connection between the thermocouple 1 and the circuit board 2 in the temperature detection circuit based on the thermocouple 1 needs to be achieved through the connection terminal 12, at this time, the connection of the cold end of the thermocouple 1 is connected with the circuit board 2 through the connection terminal 12, and the actual position of the cold end of the thermocouple 1 is at the terminal of the connection of the cold end of the thermocouple 1, so in the temperature detection device, the actual position of the cold end is the corresponding metal shrapnel inside the connection terminal 12, at this time, the compensation resistor R1 can be arranged at the welding pin close to the connection terminal 12 of the circuit board 2, so that the compensation resistor R1 and the connection terminal 12 are in the same temperature environment, the actual cold end temperature can be acquired in real time, and the accuracy of the temperature of the cold end acquired by the compensation resistor R1 is further ensured. The specific type and implementation of the connection terminal 12 and the thermocouple 1 are not particularly limited herein, and may be selected and adjusted according to practical application.
For the description of the temperature detecting device based on the thermocouple 1 provided by the present invention, please refer to the embodiment of the temperature detecting circuit based on the thermocouple 1, and the description of the present invention is omitted herein.
As an alternative embodiment, the temperature detection device further comprises a compensation wire 13, the connection of the cold end of the thermocouple 1 being connected to the connection terminal 12 via the compensation wire 13.
Considering that the connection of the cold end of the thermocouple 1 may have a length limitation, the connection of the cold end of the thermocouple 1 may be further lengthened by the compensation wire 13, at this time, the real cold end position is at the end of the compensation wire 13, and in the whole device, the real cold end position is still at the metal elastic sheet inside the connection terminal 12, so that the compensation resistor R1 is close to the pin of the connection terminal 12, and the temperature of the cold end can be accurately collected. The specific type and implementation of the compensation wire 13 is not particularly limited herein.
Specifically, the wiring of the cold end of the thermocouple 1 can be lengthened through the compensation lead 13, so that the limitation of the wiring of the cold end of the thermocouple 1 to the applicable scene of the whole temperature detection device is avoided, the flexibility of the temperature detection device based on the thermocouple 1 is higher, and the application range is wider.
As an alternative embodiment, the compensation wire 13 is of the same type as the wire of the cold end of the thermocouple 1.
Considering that the material of the compensation wire 13 will have a certain influence on the thermoelectromotive force output by the thermocouple 1, when the compensation wire 13 is used to lengthen the connection of the cold end of the thermocouple 1, it is preferable to use the same type of wire as the connection of the cold end of the thermocouple 1, so as to further avoid the influence of the material of the compensation wire 13 or other aspects on the final detection result.
Specifically, by adopting the wire which is of the same type as the wire of the cold end of the thermocouple 1 as the compensation wire 13, the influence of the compensation wire 13 on the detection result is avoided, the accuracy of the pressure difference between the hot end and the cold end of the thermocouple 1 received by the processing module 21 is further improved, and the accuracy and the reliability of the temperature of the finally obtained measured unit are ensured.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
It should also be noted that in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. The temperature detection circuit based on the thermocouple is characterized by comprising a circuit board, a compensation resistor, a reference resistor and a processing module, wherein the compensation resistor, the reference resistor and the processing module are integrated on the circuit board;
the first input end of the processing module is connected with the cold end of the thermocouple, the second input end of the processing module is connected with the first end of the compensation resistor, the third input end of the processing module is respectively connected with the second end of the compensation resistor and the first end of the reference resistor, the second end of the reference resistor is grounded and is connected with the fourth input end of the processing module, the compensation resistor is arranged close to the cold end of the thermocouple, the first end of the compensation resistor is also connected with a power supply, and the resistance value of the compensation resistor is linearly related to the temperature;
the processing module is used for determining the temperature of the cold end of the thermocouple based on the voltage of the two ends of the compensation resistor and the voltage of the two ends of the reference resistor, determining the pressure difference between the hot end and the cold end of the thermocouple based on the cold end of the thermocouple, and determining the temperature of the unit to be measured based on the temperature of the cold end of the thermocouple and the pressure difference between the hot end and the cold end of the thermocouple.
2. The thermocouple-based temperature detection circuit according to claim 1, further comprising a first resistor having a first end connected to the power supply and a second end connected to the first end of the compensation resistor and the second input of the processing module, respectively.
3. The thermocouple-based temperature detection circuit according to claim 2, further comprising a second resistor having a first end connected to the second end of the reference resistor and a fourth input of the processing module, respectively, and a second end connected to ground.
4. The thermocouple-based temperature detection circuit of claim 1, wherein said determining the temperature of the cold end of the thermocouple based on the voltage across the compensation resistor and the voltage across the reference resistor comprises:
and determining the current resistance value of the compensation resistor based on the voltage at two ends of the compensation resistor and the voltage at two ends of the reference resistor, and determining the temperature corresponding to the current resistance value of the compensation resistor based on a resistance-temperature table of the compensation resistor, so as to take the temperature corresponding to the current resistance value of the compensation resistor as the temperature of the cold end of the thermocouple.
5. The thermocouple-based temperature detection circuit of claim 1, wherein the processing module comprises an analog-to-digital conversion module and a processor, wherein a first analog input of the analog-to-digital conversion module is used as a first input of the processing module, a second analog input is used as a second input of the processing module, a third analog input is used as a third input of the processing module, a fourth analog input is used as a fourth input of the processing module, and an output is connected to an input of the processor.
6. The thermocouple-based temperature detection circuit of claim 5, wherein the processing module further comprises a reference voltage source connected to a reference voltage port of the analog-to-digital conversion module, the reference voltage port of the analog-to-digital conversion module further connected to the first end of the compensation resistor.
7. The thermocouple-based temperature detection circuit according to any one of claims 1 to 6, further comprising a hollowed out thermal insulation tape disposed on said circuit board for separating said compensation resistor from other components on said circuit board.
8. A thermocouple-based temperature detection device, comprising a thermocouple, a connection terminal and a thermocouple-based temperature detection circuit according to any one of claims 1 to 7, wherein the hot end of the thermocouple is connected with a unit to be detected through a detection probe, and the connection of the cold end of the thermocouple is connected with the thermocouple-based temperature detection circuit through the connection terminal.
9. The thermocouple-based temperature detection device of claim 8, further comprising a compensation wire through which a connection at the cold end of the thermocouple is connected to the connection terminal.
10. The thermocouple-based temperature detection device of claim 9, wherein the compensation wire is the same type of wire as the wire at the cold end of the thermocouple.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311393514.3A CN117433650A (en) | 2023-10-25 | 2023-10-25 | Temperature detection circuit and device based on thermocouple |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311393514.3A CN117433650A (en) | 2023-10-25 | 2023-10-25 | Temperature detection circuit and device based on thermocouple |
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| CN117433650A true CN117433650A (en) | 2024-01-23 |
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| CN202311393514.3A Pending CN117433650A (en) | 2023-10-25 | 2023-10-25 | Temperature detection circuit and device based on thermocouple |
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