Multi-channel Thermocouple Measuring Apparatus for Performing Cold Junction Compensation and Method Thereof

Abstract

The present invention relates to a multi-channel thermocouple measuring device and method for performing cold junction compensation, comprising a thermocouple and a resistance thermometer pair, a temperature sensor, a detection unit including an analog-to-digital converter that converts an analog signal input from the thermocouple and resistance thermometer pair and an analog signal measured by the temperature sensor into a digital signal, and a control unit that receives the digital signal from the detection unit and performs cold junction compensation, and may be applied to other embodiments.

Description

Technology Field

[0001] The present invention relates to a multi-channel thermocouple measuring device and a method for performing cold junction compensation. Background Technology

[0002] A thermocouple is a sensor designed to measure a wide temperature range using the Seebeck effect, and due to its excellent durability, it is primarily used in extreme environments such as power plants and steel mills. A thermocouple measuring device is a device that measures temperature using the electromotive force generated by the thermocouple, and the temperature measured by the thermocouple measuring device is a value measured relative to the reference junction temperature. Therefore, the temperature near where the actual thermocouple sensor is connected to the measuring device is measured and added to the measured value to provide compensation; this compensation is called reference junction compensation or cold junction compensation. Such a thermocouple measuring device will be explained in more detail using Figure 1 below. Figure 1 is a diagram showing the configuration of a conventional thermocouple measuring device.

[0003] Referring to FIG. 1, a conventional multi-channel thermocouple measuring device has a detachable terminal block (110), and the detachable terminal block (110) includes a plurality of contacts to which a thermocouple (100) and a thermoresistor (101) are connected. A plurality of thermocouples (100) are connected to contacts (111-0 to 111-3) included in the terminal block (110). The thermoresistor (101) is connected to a reference contact (112) of the terminal block (110). The temperature of the reference contact (112) serves as a reference point for the cold junction of the thermocouple (100). The temperature of the reference contact (112) is detected by a detection unit (120) using the thermoresistor (101), and the detected temperature is transmitted to a control unit (150). The control unit (150) performs cold junction compensation for the thermocouple (100). The control unit (150) may include a memory (151) for storing data, a compensation unit (152) for performing cold junction compensation, and an interface (153) for communicating with an external device, such as a PLC (160).

[0004] The detection unit (120) is designed with a multi-channel structure to measure temperature through a plurality of thermocouples (100), and the detection unit (120) includes an A / D converter (121) that converts a current value detected through a plurality of contacts (111-0 to 111-3) to which the thermocouples (100) are connected and a reference contact (112) to which the thermistor (101) is connected into a digital signal, and is connected to an insulation unit (140) that insulates the output of the A / D converter (121) and provides it to the control unit (150). In addition, the A / D converter (121) includes a reference voltage (Vref) used to ensure accurate signal conversion.

[0005] As shown in Fig. 1, in a multi-channel thermocouple measuring device, the thermoresist (101) for cold junction compensation is located outside the detection unit (120), so a problem arises in that cold junction compensation is not properly performed due to changes in the surrounding environment. The problem to be solved

[0006] Embodiments of the present invention for solving these conventional problems provide a multi-channel thermocouple measuring device and a method for performing cold junction compensation that can improve the accuracy of thermocouple measurement and realize stable temperature compensation by minimizing the error in cold junction compensation caused by the difference between the internal temperature and the external temperature of the thermocouple measuring device.

[0007] In addition, embodiments of the present invention provide a multi-channel thermocouple measuring device and a method thereof that perform cold junction compensation capable of minimizing the error in cold junction compensation by adding a thermoresistor to the external terminal contact of the thermocouple measuring device for each channel to measure the external temperature of each channel and measuring the internal temperature of the thermocouple measuring device using a temperature sensor embedded in an analog-to-digital converter. means of solving the problem

[0008] A multi-channel thermocouple measuring device for performing cold junction compensation according to an embodiment of the present invention is characterized by comprising: a thermocouple and a resistance thermometer pair; a temperature sensor; a detection unit including an analog-to-digital converter that converts an analog signal input from the thermocouple and resistance thermometer pair and an analog signal measured by the temperature sensor into a digital signal; and a control unit that receives the digital signal from the detection unit and performs cold junction compensation.

[0009] In addition, the detection unit is provided in multiple units, and the multiple detection units are each separated.

[0010] In addition, the plurality of detectors are characterized by being spaced apart by the same distance from each other.

[0011] In addition, it is characterized by the distance between the thermistor and the analog-to-digital converter being equally spaced.

[0012] In addition, it is characterized by the distance between the contact point to which the thermocouple is connected and the above-mentioned resistance thermometer being equally spaced.

[0013] In addition, the control unit is characterized by performing thermal conduction modeling using thermal resistance and thermal capacitance.

[0014] In addition, the control unit is characterized by generating a heat conduction time constant model and a linear model from the heat conduction modeling.

[0015] In addition, the control unit is characterized by calculating dynamic weights to be applied to the thermal conduction time constant model and the linear model to calculate the cold junction temperature to be compensated for each channel.

[0016] In addition, the temperature sensor is characterized as being an internal temperature sensor provided inside the detection unit.

[0017] In addition, a multi-channel thermocouple measurement method for performing cold junction compensation according to an embodiment of the present invention is characterized by comprising the steps of: receiving an analog signal from a pair of thermocouples and a thermoresistor in a multi-channel thermocouple measurement device; converting the input analog signal and the analog signal measured by a temperature sensor into a digital signal in the multi-channel thermocouple measurement device; and performing cold junction compensation based on the digital signal in the multi-channel thermocouple measurement device.

[0018] In addition, the step of performing cold junction compensation is characterized by including the step of performing thermal conduction modeling using thermal resistance and thermal capacitance in the multi-channel thermocouple measuring device, the step of generating a thermal conduction time constant model and a linear model from the thermal conduction modeling, the step of calculating dynamic weights to be applied to the thermal conduction time constant model and the linear model, and the step of calculating the cold junction temperature to be compensated for each channel based on the calculated dynamic weights. Effects of the invention

[0019] As described above, the multi-channel thermocouple measuring device and method for performing cold junction compensation according to the present invention has the effect of improving the accuracy of thermocouple measurement and realizing stable temperature compensation by minimizing the error in cold junction compensation caused by the difference between the internal temperature and the external temperature of the thermocouple measuring device.

[0020] In addition, the multi-channel thermocouple measuring device and method for performing cold junction compensation according to the present invention has the effect of minimizing the error in cold junction compensation by adding a thermoresistor to the external terminal contact of the thermocouple measuring device for each channel to measure the external temperature of each channel, and measuring the internal temperature of the thermocouple measuring device using a temperature sensor embedded in an analog-to-digital converter. Brief explanation of the drawing

[0021] Figure 1 is a diagram showing the configuration of a conventional thermocouple measuring device. FIG. 2 is a diagram showing the configuration of a multi-channel thermocouple measuring device that performs cold junction compensation according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing a multi-channel thermocouple measuring device according to an embodiment of the present invention. FIG. 4 is a flowchart illustrating a method for performing cold junction compensation in a multi-channel thermocouple measuring device according to an embodiment of the present invention. FIG. 5 is a detailed flowchart for explaining a cold junction compensation application method according to an embodiment of the present invention. FIG. 6 is a diagram showing a thermal conduction model of a multi-channel thermocouple measuring device according to an embodiment of the present invention. Specific details for implementing the invention

[0022] Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. The detailed description disclosed below, together with the accompanying drawings, is intended to describe exemplary embodiments of the present invention and is not intended to represent the only embodiment in which the present invention can be practiced. In order to clearly explain the present invention in the drawings, parts unrelated to the description may be omitted, and the same reference numerals may be used for identical or similar components throughout the specification.

[0023] FIG. 2 is a diagram showing the configuration of a multi-channel thermocouple measuring device that performs cold junction compensation according to an embodiment of the present invention. FIG. 3 is a diagram schematically showing a multi-channel thermocouple measuring device according to an embodiment of the present invention.

[0024] Referring to FIGS. 2 and 3, a multi-channel thermocouple measuring device according to the present invention has a separable terminal block (210), and the separable terminal block (210) includes a plurality of contacts to which thermocouples (200-0, 200-1, 200-2, 200-3) and resistance thermometers (201-0, 201-1, 201-2, 201-3) are connected. The multi-channel thermocouple measuring device is configured to include first to fourth detection units (220-0, 220-1, 220-2, 220-3) that detect the temperatures of thermocouples (200-0, 200-1, 200-2, 200-3) and resistance thermometers (201-0, 201-1, 201-2, 201-3) and convert them into digital signals, and a control unit (250) that compensates for the cold junction temperature of the thermocouple detection temperatures of the first to fourth detection units (220-0, 220-1, 220-2, 220-3) and provides it to a PLC (260). The characteristic configuration and operation of such a multi-channel thermocouple measuring device will be explained in more detail below.

[0025] The present invention divides the configuration of the detector (220) by channel to configure the first to fourth detectors (220-0, 220-1, 220-2, 220-3) for four channels. These first to fourth detectors (220-0, 220-1, 220-2, 220-3) can be isolated by insulation using a PCB. By separating the first to fourth detectors (220-0, 220-1, 220-2, 220-3), electromagnetic interference (EMI) or other electrical interference can be reduced, thereby improving the reliability and stability of the measuring equipment. Additionally, by maintaining the distance between the detectors, thermal interference between adjacent detectors can be minimized, ensuring precise temperature measurement between the thermocouple and the resistance thermometer. In addition, by separating the first to fourth detection units (220-0, 220-1, 220-2, 220-3), it is possible to inspect or replace parts of only the corresponding detection unit without affecting the entire system when a problem occurs in a specific channel.

[0026] In addition, the first to fourth detector units (220-0, 220-1, 220-2, 220-3) can each be configured to be spaced apart by the same distance. Through this, first, each detector unit is exposed to the same thermal environment to maintain constant thermal conductivity characteristics, thereby minimizing thermal imbalance or interference and ensuring consistent temperature measurement. Second, the thermocouples (200-0, 200-1, 200-2, 200-3) operate under the same conditions, thereby improving the reliability of cold junction compensation. Third, the distribution of heat generated within the multi-channel thermocouple measuring device is maintained in a regular and predictable manner, thereby improving the accuracy of temperature measurement. Fourth, the hardware design can be simplified, making the placement of electronic circuits, wiring, and mechanical parts simpler. Furthermore, since only the distance between detector units needs to be considered when adding detector units, system modularization is possible and the manufacturing process can be standardized, thereby minimizing the time and cost consumed during manufacturing.

[0027] In the embodiments of the present invention, for convenience of explanation, a multi-channel thermocouple measuring device is described as having four channels, but it is not necessarily limited thereto, and the number of channels can be increased or decreased.

[0028] The detailed configurations of the first to fourth detection units (220-0, 220-1, 220-2, 220-3) can all be configured identically. Therefore, in the description of the present invention, only the first detection unit (220-0) may be described as necessary, and even without a separate description of the second to fourth detection units (220-1, 220-2, 220-3), they can be understood to function identically to the first detection unit (220-0). In each of the first to fourth detection units (220-0, 220-1, 220-2, 220-3), one thermocouple (200-0, 200-1, 200-2, 200-3) is connected to a contact (211-0, 211-1, 211-2, 211-3), and a thermoresist (201-0, 201-1, 201-2, 201-3) is connected to a reference contact (212-0, 212-1, 212-2, 212-3).

[0029] More specifically, for each of the first to fourth detection units (220-0, 220-1, 220-2, 220-3), a thermocouple (200-0, 200-1, 200-2, 200-3) is connected to each contact point (211-0, 211-1, 211-2, 211-3), and a resistance thermometer (201-0, 201-1, 201-2, 201-3) is connected to the reference contact point (212-0, 212-1, 212-2, 212-3). At this time, the distance between the contact point (211-0, 211-1, 211-2, 211-3) and the resistance thermometer (201-0, 201-1, 201-2, 201-3) is, respectively It is desirable that all be set identically.

[0030] In this way, by setting the distance between the contacts (211-0, 211-1, 211-2, 211-3) and the thermistors (201-0, 201-1, 201-2, 201-3) to be the same, the temperature difference between the thermocouples (200-0, 200-1, 200-2, 200-3) and thermistors (201-0, 201-1, 201-2, 201-3) can be minimized, and the temperature compensation conditions of each channel can be consistently maintained, thereby improving the accuracy and reliability of cold junction temperature compensation. In addition, all channels can operate under the same thermal conditions, and thermal interference between adjacent thermocouples (200-0, 200-1, 200-2, 200-3) and resistance thermometers (201-0, 201-1, 201-2, 201-3) can be minimized, thereby improving the accuracy of temperature measurement and the reliability of modeling results. Furthermore, the equal distance between the contacts (211-0, 211-1, 211-2, 211-3) and the resistance thermometers (201-0, 201-1, 201-2, 201-3) enables the modularization of the system, which has the advantage of making system maintenance easy and facilitating system expansion and reconfiguration, and allows the manufacturing process to be standardized, thereby minimizing the time and cost consumed during manufacturing.

[0031] The detection unit (220-0, 220-1, 220-2, 220-3) is designed with a multi-channel structure to measure temperature through a plurality of thermocouples (200-0, 200-1, 200-2, 200-3), and the detection unit (220-0, 220-1, 220-2, 220-3) converts the current value detected through a plurality of contacts (211-0, 211-1, 211-2, 211-3) to which the thermocouples (200-0, 200-1, 200-2, 200-3) are connected and a reference contact (212-0, 212-1, 212-2, 212-3) to which the resistance thermometers (201-0, 201-1, 201-2, 201-3) are connected into a digital signal. It includes a converting A / D converter (230-0, 230-1, 230-2, 230-3). The detection unit (220-0, 220-1, 220-2, 220-3) is connected to an isolation unit (240-0, 240-1, 240-2, 240-3) that isolates the output of the A / D converter (230-0, 230-1, 230-2, 230-3) and provides it to a control unit (250).

[0032] Additionally, the A / D converter (230-0, 230-1, 230-2, 230-3) includes a reference voltage (Vref) used to ensure accurate signal conversion, and includes an internal temperature sensor (231-0, 231-1, 231-2, 231-3) and a reference resistor (221-0, 221-1, 221-2, 221-3) for measuring the temperature inside the A / D converter (230-0, 230-1, 230-2, 230-3). Although not illustrated, the detector (220-0, 220-1, 220-2, 220-3) may include a signal amplifier, an excitation current generator, a multiplexer, etc.

[0033] The first to fourth detection units (220-0, 220-1, 220-2, 220-3) each provide temperature information detected from the connected thermocouples (200-0, 200-1, 200-2, 200-3) and temperature information of the reference junction (212-0, 212-1, 212-2, 212-3) detected from the resistance thermometers (201-0, 201-1, 201-2, 201-3) to the control unit (250). The control unit (250) may include a memory (251) for storing data, a compensation unit (252) for performing cold junction compensation according to a given program, and an interface unit (253) for communication with the PLC (260).

[0034] Specifically, parameters of the PLC (260) can be received through the interface unit (253) and stored in the memory (251), and the compensation unit (252) performs cold junction compensation, determines the signals of the first to fourth detection units (220-0, 220-1, 220-2, 220-3) according to the parameters, and can perform control such as changing the reference value of the A / D converter (230-0, 230-1, 230-2, 230-3).

[0035] Additionally, the PCB shown in FIG. 3 refers to a main circuit board equipped with components of a multi-channel thermocouple measuring device, and can be designed so that the PCB and the terminal block (210) can be separated. At this time, the components fixed to the PCB may include an A / D converter (230), an insulating part (240), and a power supply (245).

[0036] The PLC backplane connector (255) refers to a connector for connecting a multi-channel thermocouple measuring device to a PLC backplane that is part of the PLC (260), and the power supply (245) supplies power to the components of the multi-channel thermocouple measuring device.

[0037] As shown in FIG. 3, the distance between the A / D converters (230-0, 230-1, 230-2, 230-3) of each channel ( , distance between the thermistor (201-0, 201-1, 201-2, 201-3) and the A / D converter (230-0, 230-1, 230-2, 230-3) ) can be set identically. This ensures consistent heat flow across the entire channel.

[0038] More specifically, by setting the distance between the thermistors (201-0, 201-1, 201-2, 201-3) and the A / D converters (230-0, 230-1, 230-2, 230-3) to be the same, the temperature compensation conditions of each channel can be consistently maintained, thereby improving the accuracy and reliability of cold junction temperature compensation. Additionally, since the signal path transmitted from the thermistors (201-0, 201-1, 201-2, 201-3) to the A / D converters (230-0, 230-1, 230-2, 230-3) becomes identical, delays or signal attenuation that may occur during signal transmission can be minimized, thereby ensuring data consistency. Furthermore, by maintaining thermal balance between channels, performance degradation due to temperature changes can be prevented. In addition, the equal distance between the thermistor (201-0, 201-1, 201-2, 201-3) and the A / D converter (230-0, 230-1, 230-2, 230-3) allows for the modularization of the system, which has the advantage of making system maintenance easy and facilitating system expansion and reconfiguration, and allows the manufacturing process to be standardized, thereby minimizing the time and cost consumed during manufacturing.

[0039] FIG. 4 is a flowchart illustrating a method for performing cold junction compensation in a multi-channel thermocouple measuring device according to an embodiment of the present invention. FIG. 5 is a detailed flowchart illustrating a method for applying cold junction compensation according to an embodiment of the present invention.

[0040] Referring to FIGS. 4 and 5, in step 401, the voltage detected at the contact (211) to which the thermocouple (200) is connected is converted into a digital signal by an A / D converter (230). The converted digital signal is transmitted to the compensation unit (252) via the insulation unit (240). At this time, the converted digital signal is recorded in the memory (251) as an AD value (AD_VAL_TC_preRJC[n]) without compensating for the thermocouple cold junction. The compensation unit (252) checks the temperature corresponding to the measured voltage using a temperature conversion table according to the thermocouple type based on the voltage measured as the AD value, and stores the confirmed temperature (T_TC_preRJC[n]) in the memory (251). At this time, [n] represents the channel number. At this time, the temperature conversion table according to the thermocouple type may be received from a manufacturer producing the thermocouple according to the type of thermocouple configured and stored in the memory (251).

[0041] In step 403, the current sent from the excitation current generator (not shown) included in the detection unit (220) passes through the thermistor (201) and then through the reference resistor (221). At this time, the voltage across the reference resistor (221) is selected as the reference voltage in the A / D converter (230). The reference voltage (ADC_RT_VAL) converted by the A / D converter (230) is transmitted to the compensation unit (252) via the insulation unit (240). The compensation unit (252) uses the following mathematical formulas 1 and 2 to [calculate] the resistance of the thermistor (201) ) can be produced.

[0042]

[0043]

[0044] At this time, ADC_MAX_LVL is the maximum level determined by the resolution of the A / D converter (230). For example, if the A / D converter (230) is 16 bits, the maximum level can be 65,656. represents the known resistance of the reference resistance (221). In addition, the compensation unit (252) checks the external temperature corresponding to the measured resistance according to the temperature conversion table related to the resistance measuring element (201) received from the producer of the resistance measuring element (201) based on the resistance of the calculated resistance measuring element (201), and the checked external temperature ( It can be stored in memory (251) as ). Here, [n] means channel number.

[0045] In step 405, the A / D converter (230) obtains sensing data from the built-in internal temperature sensor (231) as a digital signal, which is the internal temperature ( It is converted into ) and transmitted to the compensation unit (252) via the insulation unit (240), and this is stored in the memory (251). In this way, by using the internal temperature sensor (231), there is no need to additionally provide an external temperature sensor, so the system design can be simplified, and the effect of reducing component costs, installation space, and maintenance costs can be achieved. In addition, since the internal temperature sensor (231) monitors the temperature of the A / D converter (230) itself, data delay problems caused by overheating or sudden temperature changes can be minimized, and damage to the multi-channel thermocouple measuring device including the detection unit (220) can be prevented.

[0046] In step 407, the compensation unit (252) calculates a cold junction compensation coefficient and performs cold junction compensation. This will be explained in more detail using FIG. 5 below. The compensation unit (252) calculates the external temperature ( ) and internal temperature( The cold junction temperature suitable for each channel is calculated by comparing the values. The cold junction temperature is converted into a corresponding voltage (AD_VAL_TC_RJC[n]) using a temperature conversion table according to the thermocouple type. The compensation unit (252) calculates a final voltage (AD_VAL_FINAL[n]) by adding AD_VAL_TC_RJC[n] and AD_VAL_TC_preRJC[n], and can calculate a compensation coefficient for cold junction compensation by checking the temperature corresponding to the final voltage calculated from the temperature conversion table according to the thermocouple type.

[0047] More specifically, referring to FIG. 5, in step 501, the compensation unit (252) stores reference data in memory (251). Reference data refers to data obtained by introducing a multi-channel thermocouple measuring device into a chamber and changing the operating temperature range of the multi-channel thermocouple measuring device and the degree of airflow that may affect the multi-channel thermocouple measuring device. To this end, thermocouples (200) of the same type are connected to each channel of the multi-channel thermocouple measuring device. Inside the chamber, the measurement point of the thermocouple is at a constant temperature ( It is maintained at ), and the temperature around the multi-channel thermocouple measuring device is changed and applied within the range of 0℃ to 55℃. And when the ambient temperature is changed, reference data is stored in memory (251) at regular intervals. At this time, the reference data is T_TC_preRJC[n] when there is air flow in the chamber and when there is no air flow, , It may refer to the raw temperature measured by the thermocouple before cold junction compensation, the temperature measured by the thermistor (201) connected to each channel, and the temperature measured by the built-in temperature sensor (231) embedded in the A / D converter (230) of each channel, respectively. Since the rate of temperature change of the multi-channel thermocouple measuring device changes according to the airflow within the chamber, the cold junction temperature ( ) can be calculated using the following mathematical formula 3.

[0048]

[0049] In step 503, the compensation unit (252) performs a thermal conduction modeling that reflects thermal conduction characteristics using the thermal resistance and thermal capacitance of the multi-channel thermocouple measuring device, and generates a thermal conduction time constant model and a linear model from the thermal conduction modeling. At this time, the thermal conduction model generated by performing the thermal conduction modeling is as shown in FIG. 6 below. FIG. 6 is a diagram showing a thermal conduction modeling of a multi-channel thermocouple measuring device according to an embodiment of the present invention.

[0050] Referring to FIG. 6, the combination of thermal resistance and thermal capacitance is thermal impedance ( It can be expressed as ), and the thermal impedance can be calculated as shown in Equation 4 below.

[0051]

[0052] At this time, is thermal resistance, ε represents thermal capacitance, and s represents the Laplace variable. Thermal resistance indicates the resistance to heat flow in a multichannel thermocouple measuring device, and thermal capacitance indicates how the temperature of the multichannel thermocouple measuring device changes over time in response to thermal energy.

[0053] In addition, in the heat conduction model shown in Fig. 6 is the thermal impedance of the PCB, is the thermal impedance of the terminal block, is the thermal impedance of the external environment, is heat flow due to external temperature change, is heat flow due to internal heat generation, is the temperature of the thermistor (201) corresponding to channel n, is the temperature of the internal temperature sensor (231) equipped in the A / D converter (230) corresponding to channel n, represents the cold junction temperature corresponding to channel n.

[0054] The compensation unit (252) solves the heat conduction model shown in FIG. 6 into an electrical circuit form so that when there is no airflow around the multi-channel thermocouple measuring device , , Regarding the relationship, a heat conduction time constant model can be generated as a first-order differential equation as shown in Equation 5 below.

[0055]

[0056] At this time, is the thermal conductivity time constant of the PCB, represents the thermal conduction time constant of the terminal block. This mathematical equation 5 indicates how the cold junction temperature changes over time based on internal and external temperature changes.

[0057] Additionally, the compensation unit (252) can generate a linear model such as the following mathematical formula 6 when air flow is present around the multi-channel thermocouple measuring device.

[0058]

[0059] At this time, It can be a linear coefficient, which is a constant value calculated based on reference data.

[0060] In step 505, the compensation unit (252) uses a heat conduction time constant model and a linear model as shown in mathematical formula 7 below to determine the final cold junction temperature. Calculates.

[0061]

[0062] At this time, is the cold junction temperature calculated using the thermal conduction time constant model, can refer to the cold junction temperature calculated using a linear model. can be a dynamic weight that varies between 0 and 1, and the dynamic weight can be calculated using the following mathematical formula 8. The dynamic weight can be calculated based on the internal and external temperature difference of the multichannel thermocouple measuring device across various channels, with a focus on the outermost channel.

[0063]

[0064] In this case, N and 0 represent the outermost channels in the multi-channel thermocouple measuring device, and , represents the internal temperature of the outermost channel at time (t), and , represents the external temperature of the outermost channel at time (t).

[0065] The normalization factor is calculated based on reference data acquired when the ambient temperature changes within the operating range of the multichannel thermocouple measuring device, and is determined by the maximum product of the internal and external temperature differences of the outermost channel when testing the multichannel thermocouple measuring device under various conditions, such as the presence or absence of airflow.

[0066] In step 507, the compensation unit (252) is the final cold junction temperature calculated through mathematical formula 7. Based on this, cold junction compensation can be applied, and the process can be terminated by returning to Fig. 4. For example, if the temperature difference between the internal and external temperatures of the outermost channel is large, it indicates poor thermal circulation, and in this case, the thermal conduction time constant model can be trusted more. Also, if the temperature difference is small, it indicates good thermal circulation, and in this case, the linear model can be trusted more. As such, the present invention has the effect of enabling more accurate cold junction compensation according to real-time environmental conditions around a multi-channel thermocouple measuring device.

[0067] In addition, in the embodiments of the present invention, step 501 is described as being performed after step 405, but it is not necessarily limited thereto, and step 501 may be performed when the process of FIG. 4 begins.

[0068] Generally, since heat has the property of rising, the path of heat movement within a multi-channel thermocouple measuring device varies depending on the installation direction of the multi-channel thermocouple measuring device. In particular, in a situation where the multi-channel thermocouple measuring device is installed in a direction such as that shown in Fig. 3, heat moves upward in the direction of the multi-channel thermocouple measuring device, so a deviation in internal temperature occurs between the two end channels, and thus the cold junction temperature may not be calculated accurately.

[0069] To resolve this, reference data is re-acquired according to the installation direction of the multi-channel thermocouple measuring device, and the linear coefficient It can be recalculated. Through this, the linear coefficient can be adjusted in real time according to the installation direction of the multi-channel thermocouple measuring device to ensure cold junction compensation and internal temperature measurement accuracy.

[0070] The embodiments of the invention disclosed in this specification and drawings are provided merely as specific examples to facilitate the explanation of the technical content of the invention and to aid in understanding the invention, and are not intended to limit the scope of the invention. Accordingly, the scope of the invention should be interpreted to include all modifications or variations derived based on the technical concept of the invention, in addition to the embodiments disclosed herein. Explanation of the symbols

[0071] 200: Heat Squadron 201: Resistance thermometer 210: Terminal block 211: Contact 212: Reference contact 220: Detector 221: Reference resistor 230: A / D converter 240: Insulation part 245: Power supply 255: PLC Backplane Connector 260: PLC

Claims

Claim 1 A multi-channel thermocouple measuring device characterized by comprising: a thermocouple and a resistance thermometer pair; a temperature sensor; a detection unit including an analog-to-digital converter that converts an analog signal input from the thermocouple and resistance thermometer pair and an analog signal measured by the temperature sensor into a digital signal; and a control unit that receives the digital signal from the detection unit and performs cold junction compensation. Claim 2 A multi-channel thermocouple measuring device according to claim 1, wherein the detector is provided in a plurality and the plurality of detectors are each separated. Claim 3 A multi-channel thermocouple measuring device according to paragraph 2, characterized in that the plurality of detectors are spaced apart from each other by the same distance. Claim 4 A multi-channel thermocouple measuring device according to claim 3, characterized in that the distance between the thermoresist and the analog-to-digital converter is equally spaced. Claim 5 A multi-channel thermocouple measuring device according to claim 4, characterized in that the distance between the contact point to which the thermocouple is connected and the thermistor is equally spaced. Claim 6 A multi-channel thermocouple measuring device according to claim 5, wherein the control unit performs thermal conduction modeling using thermal resistance and thermal capacitance. Claim 7 A multi-channel thermocouple measuring device according to claim 6, wherein the control unit generates a heat conduction time constant model and a linear model from the heat conduction modeling. Claim 8 A multi-channel thermocouple measuring device according to claim 7, wherein the control unit calculates dynamic weights to be applied to the thermal conduction time constant model and the linear model to calculate the cold junction temperature to be compensated for each channel. Claim 9 A multi-channel thermocouple measuring device according to claim 1, characterized in that the temperature sensor is an internal temperature sensor provided inside the detection unit. Claim 10 A method for performing cold junction compensation, characterized by comprising: a step in which a multi-channel thermocouple measuring device receives an analog signal from a pair of thermocouples and a thermoresistor; a step in which the multi-channel thermocouple measuring device converts the input analog signal and the analog signal measured by a temperature sensor into a digital signal; and a step in which the multi-channel thermocouple measuring device performs cold junction compensation based on the digital signal. Claim 11 A method for performing cold junction compensation according to claim 10, wherein the step of performing cold junction compensation comprises: a step of performing thermal conduction modeling using thermal resistance and thermal capacitance in the multi-channel thermocouple measuring device; a step of generating a thermal conduction time constant model and a linear model from the thermal conduction modeling; a step of calculating dynamic weights to be applied to the thermal conduction time constant model and the linear model; and a step of calculating the cold junction temperature to be compensated for per channel based on the calculated dynamic weights.

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