Multichannel thermocouple measurement device and method therefor

Abstract

The present invention relates to a multichannel thermocouple measurement device that performs a cold junction compensation, and a method therefor, the device comprising: a thermocouple-resistance temperature detector pair; a temperature sensor; a detection unit including an analog-digital converter that converts an analog signal input from the thermocouple-resistance temperature detector pair and an analog signal measured from the temperature sensor into digital signals; and a control unit that receives the digital signals from the detection unit to perform a cold junction compensation. The present invention can also be applied to other embodiments.

Description

Multichannel thermocouple measuring device and method

[0001] The present invention relates to a multi-channel thermocouple measuring device and a method thereof.

[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 measures temperature using the electromotive force generated by the thermocouple and controls the temperature of an external device based on the measured temperature; the temperature measured by the thermocouple is a value measured relative to the reference junction temperature. Therefore, compensation is provided by measuring the temperature near where the actual thermocouple sensor is connected to the measuring device and adding it to the measured value; this compensation is called reference junction compensation or cold junction compensation.

[0003] Furthermore, the Proportional-Integral-Derivative (PID) controller measures the output value (PV; process value) of the target to be controlled and calculates the error value (EV; error value) by comparing it with the desired set value (SV; set value). The PID controller is a controller that calculates the control value (MV; manipulated value) required for control through PID operations based on the calculated error value.

[0004] Recently, multi-channel thermocouple measuring devices that perform temperature control of external devices using such thermocouples and PID control have become common. Such thermocouple measuring devices will be explained in more detail using Figure 1 below. Figure 1 is a diagram showing the configuration of a conventional thermocouple measuring device.

[0005] 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, a PID calculation unit (154) for calculating a control value (MV), and an interface (153) for communicating with an external device, such as a PLC (160).

[0006] 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.

[0007] The PID calculation unit (154) included in the control unit (150) performs PID control with the measured temperature value (PV) to reach a target temperature (SV) pre-set by the user, and calculates a control value (MV). The control unit (150) transmits the calculated control value (MV) to the output unit (130) through the insulation unit (141). The output unit (130) may include an output signal generation unit (131) for generating an output signal according to the control value (MV) and transmitting the output to each contact (113-0 to 113-3). The output signal generation unit (131) converts the control value (MV) into PWM (Pulse with Modulation) or analog current. The output signal may be in the form of voltage PWM (Pulse with Modulation) or analog current (4~20mA, 0~20mA, etc.). At this time, the output is connected to an actuator (not shown) for controlling a heating or cooling element. To this end, the detachable terminal block (110) may include output contacts (113-0 to 113-3) for providing an interface between the output unit (130) and the actuator, and may include an external power source (102) for supplying power to the output unit (130). Pulse with Modulation (PWM) or analog current is used to supply power to an external device, such as a heating device or a cooling device, which is the target of control, through the output contacts (113-0 to 113-3), and the power to be provided to the external device is determined according to the duty cycle (0 to 100%).

[0008] 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.

[0009] In addition, a multi-channel thermocouple measuring device having a separate terminal block (110) has a problem in that it is difficult to accurately measure the thermocouple cold junction temperature because the positions of the reference junction (112) and the junctions (111-0 to 111-3) to which the thermocouple is connected are different for cold junction compensation. Also, since the temperature change of the junctions (111-0 to 111-3) is applied differently for each channel, a temperature deviation between channels occurs when ambient temperature changes, making it difficult to maintain the temperature of the external device at the set value (SV), which can negatively affect the accuracy of temperature control. Furthermore, since the accuracy of temperature control decreases when the internal temperature and the external temperature of the multi-channel thermocouple measuring device have not reached thermal equilibrium, a problem arises in that one must wait until the internal temperature and the external temperature reach thermal equilibrium.

[0010] 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.

[0011] 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.

[0012] Furthermore, embodiments of the present invention provide a multi-channel thermocouple measuring device and a method using thermocouple cold junction compensation that can minimize the limitations caused by the preheating time of the multi-channel thermocouple measuring device through cold junction compensation, even when the internal temperature and external temperature of the multi-channel thermocouple measuring device have not reached thermal equilibrium.

[0013] 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.

[0014] In addition, the detection unit is provided in multiple units, and the multiple detection units are each separated.

[0015] In addition, the plurality of detectors are characterized by being spaced apart by the same distance from each other.

[0016] In addition, it is characterized by the distance between the thermistor and the analog-to-digital converter being equally spaced.

[0017] 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.

[0018] In addition, the control unit is characterized by performing thermal conduction modeling using thermal resistance and thermal capacitance.

[0019] In addition, the control unit is characterized by generating a heat conduction time constant model and a linear model from the heat conduction modeling.

[0020] 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.

[0021] In addition, the temperature sensor is characterized as being an internal temperature sensor provided inside the detection unit.

[0022] 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.

[0023] 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.

[0024] A multi-channel thermocouple measuring device using thermocouple cold junction compensation according to an embodiment of the present invention comprises a plurality of thermocouples, at least one thermistor, and an internal temperature sensor, and is characterized by comprising: a detection unit including an analog-to-digital converter that converts an analog signal input from the thermocouple and the thermistor and an analog signal measured by the internal temperature sensor into a digital signal; a control unit that receives the digital signal from the detection unit, performs cold junction compensation, and calculates a control value to control the temperature of at least one external device; and an output unit that generates an output signal based on the control value received from the control unit and outputs it to the at least one external device.

[0025] In addition, the control unit is characterized by calculating the control value through proportional-integral-derivative (PID) operations.

[0026] In addition, the detection unit is provided in multiple units, and the multiple detection units are each separated.

[0027] In addition, the thermistor is characterized by being provided in each of the channels at both ends among the plurality of channels.

[0028] In addition, the control unit is characterized by performing thermal conduction modeling using thermal resistance and thermal capacitance.

[0029] In addition, the control unit is characterized by generating a thermal conduction time constant model and a linear model for calculating the cold junction temperature of the channel connected to the thermoresistor from the thermal conduction modeling.

[0030] In addition, the control unit is characterized by supplementing the generated heat conduction time constant model and the linear model using the calculated cold junction temperature.

[0031] 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.

[0032] In addition, the temperature sensor is characterized as being an internal temperature sensor provided inside the detection unit.

[0033] In addition, a temperature control method using thermocouple cold junction compensation according to an embodiment of the present invention is characterized by comprising the steps of: a temperature control device receiving an analog signal from a thermocouple and a resistance thermometer; a multi-channel thermocouple measuring device converting the input analog signal and the analog signal measured by a temperature sensor into a digital signal; a multi-channel thermocouple measuring device performing cold junction compensation based on the digital signal; a multi-channel thermocouple measuring device calculating a control value to control the temperature of at least one external device based on the cold junction compensation and generating an output signal; and a multi-channel thermocouple measuring device outputting the output signal to the at least one external device.

[0034] In addition, the step of performing cold junction compensation is characterized by including: 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 for calculating the cold junction temperature of the channel connected to the thermistor 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 each channel based on the calculated dynamic weights.

[0035] 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.

[0036] 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.

[0037] In addition, the multi-channel thermocouple measuring device and method using thermocouple cold junction compensation according to the present invention have the effect of minimizing the limitations caused by the preheating time of the multi-channel thermocouple measuring device through cold junction compensation, even when the internal temperature and external temperature of the multi-channel thermocouple measuring device have not reached thermal equilibrium.

[0038] Figure 1 is a diagram showing the configuration of a conventional thermocouple measuring device.

[0039] FIG. 2 is a diagram showing the configuration of a multi-channel thermocouple measuring device according to the first embodiment of the present invention.

[0040] FIG. 3 is a schematic diagram showing a multi-channel thermocouple measuring device according to the first embodiment of the present invention.

[0041] FIG. 4 is a flowchart for explaining the operation of a multi-channel thermocouple measuring device according to a first embodiment of the present invention.

[0042] FIG. 5 is a detailed flowchart for explaining a cold junction compensation application method according to a first embodiment of the present invention.

[0043] FIG. 6 is a diagram showing a thermal conduction model of a multi-channel thermocouple measuring device according to the first embodiment of the present invention.

[0044] FIG. 7 is a diagram showing the configuration of a multi-channel thermocouple measuring device according to a second embodiment of the present invention.

[0045] FIG. 8 is a schematic diagram showing a multi-channel thermocouple measuring device according to a second embodiment of the present invention.

[0046] FIG. 9 is a flowchart for explaining the operation of a multi-channel thermocouple measuring device according to a second embodiment of the present invention.

[0047] FIG. 10 is a diagram showing a thermal conduction model of a multi-channel thermocouple measuring device according to a second embodiment of the present invention.

[0048] 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.

[0049] FIG. 2 is a diagram showing the configuration of a multi-channel thermocouple measuring device according to a first embodiment of the present invention. FIG. 3 is a diagram schematically showing a multi-channel thermocouple measuring device according to a first embodiment of the present invention.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] In the embodiments of the present invention, for convenience of explanation, a multi-channel thermocouple measuring device is described as being composed of four channels, but it is not necessarily limited thereto, and the number of channels can be increased or decreased. In addition, in the embodiments of the present invention, a resistance thermometer is described as being connected to each channel, but it is not necessarily limited thereto, and the resistance thermometer may be selectively connected to some channels.

[0054] 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).

[0055] More specifically, in 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 (211-0, 211-1, 211-2, 211-3), and a thermoresist (201-0, 201-1, 201-2, 201-3) is connected to the reference contact (212-0, 212-1, 212-2, 212-3). At this time, it is preferable that the distances between the contacts (211-0, 211-1, 211-2, 211-3) and the thermistors (201-0, 201-1, 201-2, 201-3) are all set to be the same as A0, A1, A2, and A3, respectively.

[0056] 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.

[0057] 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 the control unit (250).

[0058] 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.

[0059] 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).

[0060] 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).

[0061] 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).

[0062] 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.

[0063] As shown in FIG. 3, the distance (Y) between the A / D converters (230-0, 230-1, 230-2, 230-3) of each channel 0-1 , Y 1-2 , Y 2-3The distances (X0, X1, X2, X3) between the thermistors (201-0, 201-1, 201-2, 201-3) and the A / D converters (230-0, 230-1, 230-2, 230-3) can be set equally. This ensures consistent heat flow throughout the entire channel.

[0064] 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.

[0065] FIG. 4 is a flowchart illustrating a method for performing cold junction compensation in a multi-channel thermocouple measuring device according to a first embodiment of the present invention. FIG. 5 is a detailed flowchart illustrating a method for applying cold junction compensation according to a first embodiment of the present invention.

[0066] 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).

[0067] 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 (R) of the thermistor (201). RT ) can be produced.

[0068]

[0069]

[0070] 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-bit, the maximum level can be 65,656. R Refrepresents 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 calculated resistance of the resistance measuring element (201), and the checked external temperature (Ext_T n It can be stored in memory (251) as ). Here, [n] means channel number.

[0071] In step 405, the A / D converter (230) converts the sensing data obtained from the built-in internal temperature sensor (231) into a digital signal, which is the internal temperature (Int_T n 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.

[0072] 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 (Ext_T n ) and internal temperature(Int_T nThe 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.

[0073] 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 (T_TC_HOT const It is maintained as ), 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], Ext_T when there is air flow in the chamber and when there is no air flow. n , Int_T n 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 (RJC_T n ) can be calculated using the following mathematical formula 3.

[0074]

[0075] In step 503, the compensation unit (252) performs 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 model in which a multi-channel thermocouple measuring device according to an embodiment of the present invention is thermally modeled.

[0076] Referring to FIG. 6, the combination of thermal resistance and thermal capacitance is thermal impedance (Z t It can be expressed as ), and the thermal impedance can be calculated as shown in Equation 4 below.

[0077]

[0078] At this time, R t is thermal resistance, C t 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.

[0079] 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, I t Ext is the heat flow due to external temperature changes, I t Int is heat flow due to internal heat generation, Ext_T n is the temperature of the thermistor (201) corresponding to channel n, Int_T n is the temperature of the internal temperature sensor (231) equipped in the A / D converter (230) corresponding to channel n, RJC_Tn represents the cold junction temperature corresponding to channel n.

[0080] 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 Ext_T n , Int_T n , RJC_T n Regarding the relationship, a heat conduction time constant model can be generated as a first-order differential equation as shown in Equation 5 below.

[0081]

[0082] At this time, τ PCB τ is the thermal conduction time constant of the PCB. TB 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.

[0083] 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.

[0084]

[0085] At this time, a L , b L , c L It can be a linear coefficient, which is a constant value calculated based on reference data.

[0086] 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, RJC_T n Calculate (t).

[0087]

[0088] At this time, Mdl_T_RJC_T n (t) is the cold junction temperature calculated using the heat conduction time constant model, Mdl_L_RJC_T n(t) may represent the cold junction temperature calculated using a linear model. α may be a dynamic weight that varies between 0 and 1, and the dynamic weight can be calculated using the following Equation 8. The dynamic weight can be calculated based on the internal and external temperature differences of the multichannel thermocouple measuring device across various channels, focusing on the outermost channel.

[0089]

[0090] Here, N and 0 represent the outermost channel in the multichannel thermocouple measuring device, and Int_T N (t), Int_T o (t) represents the internal temperature of the outermost channel at time (t), Ext_T N (t), Ext_T o (t) represents the external temperature of the outermost channel at time (t).

[0091] 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.

[0092] In step 507, the compensation unit (252) is the final cold junction temperature RJC_T calculated through mathematical formula 7. nCold junction compensation can be applied based on (t), 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.

[0093] 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 starts.

[0094] 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.

[0095] To resolve this, reference data is re-acquired according to the installation direction of the multi-channel thermocouple measuring device, and the linear coefficient a L , b L , c L 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.

[0096] FIG. 7 is a diagram showing the configuration of a multi-channel thermocouple measuring device according to a second embodiment of the present invention. FIG. 8 is a diagram schematically showing a multi-channel thermocouple measuring device according to a second embodiment of the present invention.

[0097] Compared to the multi-channel thermocouple measuring device of Fig. 2, the multi-channel thermocouple measuring device of Fig. 7 additionally includes a PID calculation unit (254), an insulation unit (241), and an output unit (270), and two thermoresistors (201-0, 201-3) are connected, so the above description is used for the overlapping configuration.

[0098] First, the control unit (250) may further 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 a PLC (260), and a PID calculation unit (254) for generating a temperature control signal for controlling the temperature of an external device, such as a heating device or a cooling device, through PID calculation.

[0099] The PID operation unit (254) generates a temperature control signal for controlling the temperature of an external device through PID (Proportional-Integral-Derivative) operations and transmits it to the external device. More specifically, the PID operation unit (254) measures the output value (PV; process value) of the external device and checks the target temperature (SV; set value) of the external device that is preset by the user. The PID operation unit (254) calculates an error value (EV; error value) by comparing the output value (PV) and the target temperature (SV). Based on the calculated error value (EV), the PID operation unit (254) calculates a control value (MV; manipulated value) required for controlling the external device through PID operations.

[0100] The PID calculation unit (254) transmits the calculated control value (MV) to the output unit (270) through the isolation unit (241). An output signal generation unit (not shown) included in the output unit (270) generates a temperature control signal, such as a PWM signal or analog current, based on the control value (MV) and transmits it to an external device. The temperature control signal is used to supply power to an external device that is the target of control through output contacts (214-0, 241-1, 214-2, 214-3) to provide an interface between the output unit (270) and the actuator, and is a signal that determines the power to be supplied to the external device with a duty cycle (0~100%). Additionally, the terminal block (210) may include an external power source (203) for supplying power to the output unit (270).

[0101] Additionally, the PCB shown in FIG. 8 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, 241), and a power supply (245).

[0102] 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.

[0103] As shown in FIG. 8, the distance (Y) between the A / D converters (230-0, 230-1, 230-2, 230-3) of each channel 0-1 , Y 1-2 , Y 2-3 ) can be set identically. This ensures consistent heat flow across the entire channel.

[0104] More specifically, by setting the distance between 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. In addition, the equal distance between the A / D converters (230-0, 230-1, 230-2, 230-3) enables the modularization of the system, which has the advantages of easy system maintenance and easy system expansion and reconfiguration, and allows the manufacturing process to be standardized, thereby minimizing the time and cost consumed during manufacturing.

[0105] FIG. 9 is a flowchart for explaining the operation of a multi-channel thermocouple measuring device according to a second embodiment of the present invention. Likewise, regarding the operations (401, 403, 405, and 407) that overlap with the operation of the multi-channel thermocouple measuring device of FIG. 9 and the specific operations (501, 503, 505, 507) of the cold junction compensation application step, the content described above with reference to FIG. 4 and FIG. 5 is adopted.

[0106] Meanwhile, in step 503, the compensation unit (252) performs 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. 10.

[0107] FIG. 10 is a diagram showing a thermal conduction model of a multi-channel thermocouple measuring device according to an embodiment of the present invention.

[0108] In the heat conduction model shown in Fig. 10 is the thermal impedance of the PCB in the y-direction, is the thermal impedance in the X direction of the PCB and the terminal block (210), is the thermal impedance in the Y direction of the terminal block (210), is the thermal impedance of the external environment, I tExt is the heat flow due to external temperature changes, I t Int is heat flow due to internal heat generation, Ext_T n is the temperature of the thermistor (201) corresponding to channel n, Int_T n is the temperature of the internal temperature sensor (231) equipped in the A / D converter (230) corresponding to channel n, RJC_T n represents the cold junction temperature corresponding to channel n. Since the thermistor (201) is installed in channels 0 and 3 as shown in FIG. 7, Ext_T n Only Ext_T0 and Ext_T3 exist.

[0109] In this way, by using fewer thermistors (201) than thermocouples (200), costs can be reduced when implementing a multi-channel thermocouple measuring device, and by reducing the number of sensors when implementing a multi-channel thermocouple measuring device, the complexity of design and operation is reduced and maintenance becomes easier. In addition, by using thermistors only at locations where high-precision temperature measurement is required, high-precision temperature measurement and cold junction compensation can be performed as needed. By minimizing the use of thermistors, power consumption in the multi-channel thermocouple measuring device can be reduced, and energy efficiency can be improved accordingly.

[0110] The compensation unit (252) solves the heat conduction model shown in FIG. 10 into an electrical circuit form so that when there is no airflow around the multi-channel thermocouple measuring device Ext_T 0, Ext_T 3, Int_T n, RJC_T n Regarding the relationship, a heat conduction time constant model can be generated as a first-order differential equation such as Equation 9 and Equation 10 below. In this case, Equation 9 and Equation 10 represent a model for calculating the cold junction temperature in channel 0 and channel 3, where the thermistors (201-0, 201-3) are connected, respectively.

[0111]

[0112]

[0113] At this time, τ PCB TBX is the thermal conduction time constant in the X direction of the PCB and terminal block (210), τ TBY represents the time constant of heat conduction in the Y direction of the terminal block (210). These mathematical equations 9 and 10 indicate how the cold junction temperature changes over time based on internal and external temperature changes.

[0114] After generating mathematical formulas 9 and 10, the compensation unit (252) can generate a model for predicting the cold junction temperature in channel 1 and channel 2, where the thermoresist (201-0, 201-3) is not connected, as shown in mathematical formulas 11 and 12 below.

[0115]

[0116]

[0117] Additionally, the compensation unit (252) can generate linear models such as the following Equations 13 to 16 when there is airflow around the multi-channel thermocouple measuring device. Equations 13 and 14 are models for calculating the cold junction temperature in channel 0 and channel 3, respectively, where the thermistors (201-0, 201-3) are connected, and Equations 15 and 16 are models for predicting the cold junction temperature in channel 1 and channel 2, where the thermistors (201-0, 201-3) are not connected.

[0118]

[0119]

[0120]

[0121]

[0122] At this time, a n , b n , c nIt can be a linear coefficient, which is a constant value calculated based on reference data.

[0123] In step 505, the compensation unit (252) uses a heat conduction time constant model and a linear model as shown in mathematical formula 17 below to determine the final cold junction temperature, RJC_T n Calculate (t).

[0124]

[0125] At this time, Mdl_T_RJC_T n (t) is the cold junction temperature calculated using the heat conduction time constant model, Mdl_L_RJC_T n (t) may represent the cold junction temperature calculated using a linear model. α may be a dynamic weight that varies between 0 and 1, and the dynamic weight can be calculated using the following Equation 18. The dynamic weight can be calculated based on the internal and external temperature differences of the multichannel thermocouple measuring device across various channels, focusing on the outermost channel.

[0126]

[0127] Here, 0 and N represent the outermost channels, e.g., Channel 0 and Channel 3, in a multi-channel thermocouple measuring device, and Int_T0(t), Int_T N (t) represents the internal temperature of the outermost channel at time (t), Ext_T0(t), Ext_T N (t) represents the external temperature of the outermost channel at time (t).

[0128] 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.

[0129] In step 507, the compensation unit (252) is the final cold junction temperature RJC_T calculated through mathematical formula 17. n Cold junction compensation is applied based on (t), and the process returns to Fig. 9. 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 is more reliable. Also, if the temperature difference is small, it indicates good thermal circulation, and in this case, the linear model is more reliable. Thus, 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.

[0130] 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 starts.

[0131] In step 409, the PID operation unit (254) included in the control unit (250) generates a temperature control signal for controlling the temperature of an external device, such as a heating device or a cooling device, through PID operation and transmits it to the external device. More specifically, the PID operation unit (254) measures the output value (PV; process value) of the external device and checks the target temperature (SV; set value) of the external device that has been preset by the user. The PID operation unit (254) calculates an error value (EV; error value) by comparing the output value (PV) and the target temperature (SV). Based on the calculated error value (EV), the PID operation unit (254) calculates a control value (MV; manipulated value) required for controlling the external device through PID operation.

[0132] The control unit (250) transmits the calculated control value (MV) to the output unit (270) through the insulation unit (241). An output signal generation unit (not shown) included in the output unit (270) generates a temperature control signal, such as a PWM signal or an analog current, based on the control value (MV) and transmits it to an external device. The temperature control signal is used to supply power to the external device that is the target of control through the output contacts (214-0 to 214-3), and the power to be provided to the external device is determined according to the duty cycle (0 to 100%) of the temperature control signal.

[0133] 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.

Claims

1. Multiple heat squadrons; At least one resistance thermometer; Temperature sensor; A detection unit comprising an analog-to-digital converter that converts an analog signal input from the thermocouple and the resistance thermometer and an analog signal measured by the temperature sensor into a digital signal; and A control unit that receives a digital signal from the detection unit and performs cold junction compensation; A multi-channel thermocouple measuring device characterized by including 2. In Paragraph 1, The above detection unit is, A multi-channel thermocouple measuring device characterized by being provided in multiple units, wherein each of the multiple detectors is separated.

3. In Paragraph 2, A multi-channel thermocouple measuring device characterized by the plurality of detection units being spaced apart from each other by the same distance.

4. In Paragraph 3, A multi-channel thermocouple measuring device characterized by the distance between the above-mentioned resistance thermometer and the above-mentioned analog-to-digital converter being equally spaced.

5. In Paragraph 4, A multi-channel thermocouple measuring device characterized by the distance between the contact point to which the thermocouple is connected and the resistance measuring element being equally spaced.

6. In Paragraph 5, The above control unit is, A multi-channel thermocouple measuring device characterized by performing thermal conduction modeling using thermal resistance and thermal capacitance.

7. In Paragraph 6, The above control unit is, A multi-channel thermocouple measuring device characterized by generating a heat conduction time constant model and a linear model from the above heat conduction modeling.

8. In Paragraph 7, The above control unit is, A multi-channel thermocouple measuring device characterized by supplementing the generated thermal conduction time constant model and the linear model using the cold junction temperature calculated above.

9. In Paragraph 8, The above control unit is, A multi-channel thermocouple measuring device characterized by calculating a dynamic weight to be applied to the above-mentioned thermal conduction time constant model and the above-mentioned linear model to calculate the cold junction temperature to be compensated for per channel.

10. In Paragraph 1, The above temperature sensor is, A multi-channel thermocouple measuring device characterized by having an internal temperature sensor provided inside the above-mentioned detection unit.

11. In Paragraph 1, The above control unit is, A multi-channel thermocouple measuring device characterized by calculating a control value to control the temperature of at least one external device.

12. In Paragraph 11, An output unit that generates an output signal based on the control value received from the control unit and outputs it to at least one external device; A multi-channel thermocouple measuring device characterized by further including 13. In Paragraph 11, The above control unit is, A multi-channel thermocouple measuring device characterized by calculating the control value through proportional-integral-derivative (PID) operations.

14. In Paragraph 1, The above control unit is, A multi-channel thermocouple measuring device characterized by having each channel at both ends among a plurality of channels.

15. A multi-channel thermocouple measuring device receiving analog signals from a thermocouple and a resistance thermometer; The multi-channel thermocouple measuring device converts the input analog signal and the analog signal measured by the 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; A multi-channel thermocouple measurement method characterized by including 16. In Paragraph 15, The step of performing the above cold junction compensation is, A step of performing thermal conduction modeling using thermal resistance and thermal capacitance in the above-described multi-channel thermocouple measuring device; A step of generating a heat conduction time constant model and a linear model from the above heat conduction modeling; A step of calculating dynamic weights to be applied to the above-mentioned thermal conduction time constant model and the above-mentioned linear model; and A step of calculating the cold junction temperature to be compensated for each channel based on the dynamic weights calculated above; A multi-channel thermocouple measurement method characterized by including 17. In Paragraph 15, After the step of performing the above cold junction compensation, The multi-channel thermocouple measuring device calculates a control value to control the temperature of at least one external device based on the cold junction compensation and generates an output signal; and The step of the multi-channel thermocouple measuring device outputting the output signal to the at least one external device; A multi-channel thermocouple measurement method characterized by further including

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