Thermocouple measuring device

Abstract

The utility model discloses a thermocouple measuring device, comprising a TC input module used for collecting thermocouple voltage and successively carrying out bias processing and signal filtering conditioning; the cold end compensation module is used for acquiring the RTD voltage of the cold end of the thermocouple on the field side; the ADC module is used for sending the RTD voltage and the thermocouple voltage to the MCU control unit; the MCU control unit is used for calculating the real voltage of the thermocouple and obtaining the actual temperature value of the thermocouple according to the real voltage; the isolation module is used for isolating signals of the field side and the control side; and the power supply module is used for supplying power to each module. According to the utility model, the isolation module and the TC input module are added, signals of a field end and a control end can be effectively isolated, the influence of ESD, surge and pulse on the device is effectively reduced, the design of an analog filter circuit, independent cold end measurement and the like is added, the external interference of the system is reduced, and the design of bias voltage is added to realize thermocouple short-line self-diagnosis. Through the design, the reliability and the measurement precision are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of thermocouple temperature measurement, in particular to a thermocouple measuring device. Background Art

[0002] Thermocouple (TC) is a commonly used temperature measuring element in temperature measuring instruments. It directly measures temperature and converts the temperature signal into a thermoelectric potential signal, which is then converted into the temperature of the measured medium through an electrical instrument (secondary instrument).

[0003] Thermocouple measurements are divided into hot end measurements and cold end measurements. During testing, the hot end is placed on the heat source side as the test end to measure the temperature difference between the hot end and the cold end. The cold end is usually placed at room temperature or near the thermocouple measurement device, and the temperature of the cold end is measured. The accurate measurement temperature of the heat source is the temperature difference between the hot end and the cold end plus the temperature of the cold end.

[0004] In order to improve the measurement accuracy of thermocouples, the patent document with announcement number CN215865540U discloses a thermocouple cold end compensation circuit and a thermocouple temperature measurement system, the circuit includes a differential operational amplifier and a bridge voltage divider circuit; the bridge voltage divider circuit is connected to the power supply and the differential operational amplifier, and the output voltage of the differential operational amplifier is used as the cold end compensation voltage of the thermocouple. One bridge arm in the bridge voltage divider circuit includes a resistive device whose resistance value is adjustable with temperature, and the other bridge arms include resistors with fixed resistance values; the resistive device whose resistance value is adjustable with temperature and the cold end of the thermocouple are in the same temperature environment. When the cold end of the thermocouple is in a different temperature environment, the resistance value of the resistive device also changes with the temperature, so that the compensation voltage of the compensation circuit also changes, thereby realizing dynamic compensation of the cold end. However, after careful analysis by the applicant, it was found that, on the one hand, the circuit lacked an isolation module, which resulted in the inability to effectively isolate the signals between the field end and the control end. Accordingly, the circuit was also susceptible to ESD (Electro-Static discharge), surges and pulses, which not only affected the reliability of the system, but also easily affected the measurement accuracy. Utility Model Content

[0005] The purpose of the utility model is to overcome the above-mentioned problems existing in the prior art and provide a thermocouple measuring device. The utility model adds an isolation module and a TC input module, which can effectively isolate the signals of the field end and the control end, effectively reduce the influence of ESD, surge and pulse on the device, increase the analog filter circuit, independent cold end measurement and other designs to reduce the external interference of the system, increase the bias voltage design to realize the self-diagnosis of thermocouple breakage, and improve the reliability and measurement accuracy of the device through the above design.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0007] A thermocouple measuring device, comprising:

[0008] A TC input module, which is connected to a thermocouple and is used to collect the thermocouple voltage and perform bias processing and signal filtering conditioning on the thermocouple voltage in turn;

[0009] A cold-end compensation module, which is used to collect the RTD voltage of the cold end of the thermocouple on the field side;

[0010] An ADC module, which is connected to the TC input module, the cold end compensation module and the MCU control unit respectively, and is used to collect the RTD voltage and the thermocouple voltage after signal filtering and conditioning, and send the RTD voltage and the thermocouple voltage to the MCU control unit;

[0011] The MCU control unit is used to calculate the real voltage of the thermocouple according to the received RTD voltage and the thermocouple voltage, and obtain the actual temperature value of the thermocouple according to the real voltage;

[0012] An isolation module is provided between the ADC module and the MCU control unit to isolate signals on the field side and on the control side;

[0013] The power supply module is used to supply power to the MCU control unit, ADC module, isolation module, TC input module and cold end compensation module.

[0014] The cold-end compensation module is an internal cold-end compensation module, which includes a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a one-hundred-and-first resistor and a first thermistor. The two ends of the thirteenth resistor are respectively connected to the excitation current source output end and the second voltage sampling positive end of the ADC module. One end of the fourteenth resistor is connected to the excitation current source output end of the ADC module through the first thermistor, and the other end is connected to the second voltage sampling negative end of the ADC module; one end of the fifteenth resistor is connected between the first thermistor and the fourteenth resistor, and the other end is connected to the third voltage sampling positive end of the ADC module; one end of the sixteenth resistor is connected to the fifteenth resistor through the one-hundred-and-first resistor, and the other end is connected to the third voltage sampling negative end of the ADC module.

[0015] The internal cold-end compensation module also includes a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor and a twentieth capacitor, one end of the fifteenth capacitor is connected to the second voltage sampling positive terminal of the ADC module, and the other end is grounded; one end of the sixteenth capacitor and one end of the seventeenth capacitor are both connected to the second voltage sampling negative terminal of the ADC module, and the other end of the sixteenth capacitor and the other end of the seventeenth capacitor are both grounded; one end of the twentieth capacitor is connected to the third voltage sampling positive terminal of the ADC module, and the other end is grounded.

[0016] The cold-end compensation module is an external cold-end compensation module, and the external cold-end compensation module includes an external PT100 thermistor, a ninety-seventh resistor, a ninety-eighth resistor, a ninety-ninth resistor, a one-hundredth resistor, a one-hundredth resistor, a seventeenth transient suppression diode, an eighteenth transient suppression diode, and a nineteenth transient suppression diode, wherein both ends of the ninety-seventh resistor are respectively connected to the second voltage sampling positive terminal of the ADC module and the signal positive input terminal of the external PT100 thermistor, and both ends of the ninety-eighth resistor are respectively connected to the second voltage sampling negative terminal of the ADC module and the signal negative input terminal of the external PT100 thermistor, and both ends of the ninety-ninth resistor are respectively connected to the third voltage sampling positive terminal of the ADC module and the external PT10 0 thermistor, one end of the one hundred and second resistor is connected between the ninety-ninth resistor and the reference voltage end of the external PT100 thermistor, and the other end of the one hundredth resistor is connected to the third voltage sampling negative end of the ADC module through the one hundredth resistor; one end of the seventeenth transient suppression diode is connected between the ninety-seventh resistor and the signal positive input end of the external PT100 thermistor, and the other end is grounded; one end of the eighteenth transient suppression diode is connected between the ninety-eighth resistor and the signal negative input end of the external PT100 thermistor, and the other end is grounded; one end of the nineteenth transient suppression diode is connected between the ninety-ninth resistor and the reference voltage end of the external PT100 thermistor, and the other end is grounded.

[0017] The external cold-end compensation module also includes a 134th capacitor, a 135th capacitor, a 136th capacitor and a 139th capacitor. One end of the 134th capacitor is connected to the second voltage sampling positive terminal of the ADC module, and the other end is grounded; one end of the 135th capacitor and the 136th capacitor are both connected to the second voltage sampling negative terminal of the ADC module, and the other ends of the 135th capacitor and the 136th capacitor are both grounded; one end of the 139th capacitor is connected to the third voltage sampling positive terminal of the ADC module, and the other end is grounded.

[0018] The TC input module includes a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a first transient suppression diode, a second transient suppression diode and a ninth capacitor, wherein the input end and the output end of the tenth resistor are respectively connected to the first voltage sampling positive end of the ADC module and the positive end of the thermocouple, the input end and the output end of the eleventh resistor are respectively connected to the first voltage sampling negative end of the ADC module and the negative end of the thermocouple, the two ends of the ninth resistor are respectively connected to the reference voltage end of the thermocouple and the input end of the tenth resistor, one end of the first transient suppression diode is grounded, and the other end is connected to the input end of the tenth resistor; one end of the twelfth resistor is grounded, and the other end is connected to the input end of the eleventh resistor, the second transient suppression diode is connected in parallel to one side of the twelfth resistor, and the ninth capacitor is connected between the output end of the tenth resistor and the output end of the eleventh resistor.

[0019] The thermocouple measuring device also includes a filter circuit of a bias voltage connected to one side of the ninth resistor, the filter circuit includes a voltage stabilizer, a seventeenth resistor, an eighteenth resistor, a twentieth resistor, a twenty-first capacitor, a twenty-second capacitor and a twenty-third capacitor, one end of the seventeenth resistor is connected to the power supply module, and the other end is connected in three ways, the first way is connected in series with the eighteenth resistor and the twentieth resistor in sequence and then grounded, the second way is grounded through the twenty-first capacitor, the twenty-second capacitor and the twenty-third capacitor respectively, and the third way is connected to the ninth resistor; the cathode of the voltage stabilizer is connected between the seventeenth resistor and the eighteenth resistor, the anode is grounded, and the adjustable third end is connected between the eighteenth resistor and the twentieth resistor.

[0020] The isolation module includes a digital isolation chip, an eighteenth capacitor and a nineteenth capacitor. The digital isolation chip includes a control side signal terminal, a control side isolation terminal, a field side signal terminal and a field side isolation terminal. The control side signal terminal and the field side signal terminal are respectively connected to the MCU control unit and the ADC module. The field side isolation terminal is grounded through the eighteenth capacitor, and the control side isolation terminal is grounded through the nineteenth capacitor.

[0021] The power supply module includes a DC-DC power converter chip, a twenty-fourth capacitor, a twenty-fifth capacitor and a nineteenth resistor. The VCC terminal and the GND terminal of the DC-DC power converter chip are respectively connected to the power supply and the ground. The twenty-fourth capacitor is connected between the VCC terminal and the GND terminal. The voltage output positive terminal of the DC-DC power converter chip is respectively connected to the ADC module and the isolation module, and the voltage output positive terminal is grounded through the nineteenth resistor and the twenty-fifth capacitor.

[0022] An interference suppression module is provided between the ADC module and the power supply module, and the interference suppression module includes a magnetic bead, an eleventh capacitor and a fourteenth capacitor. The magnetic bead is connected between the voltage output positive terminal of the DC-DC power converter chip of the ADC module and the power supply module, and one end of the eleventh capacitor and the fourteenth capacitor connected in parallel is connected between the magnetic bead and the ADC module, and the other end is grounded.

[0023] By adopting the above technical solution, the beneficial technical effects of the utility model are:

[0024] 1. The utility model adds an isolation module and a TC input module, which can effectively isolate the signals of the field end and the control end, and can effectively reduce the impact of ESD, surge and pulse on the device, and effectively improve the reliability of the device. The internal cold end compensation module or the external cold end compensation module can perform internal cold end compensation or external cold end compensation of the thermocouple. The MCU control unit can choose to use internal cold end compensation or external cold end compensation according to the data collected by the TC input module to obtain the actual temperature measurement value, thereby improving the temperature measurement accuracy.

[0025] 2. The utility model can form an analog anti-aliasing filter through the tenth resistor, the eleventh resistor and the ninth capacitor, which is beneficial to reducing the aliasing noise problem that cannot be solved by the digital filter and further improves the measurement accuracy of the thermocouple.

[0026] 3. The cold-end RTD compensation measurement of the utility model adopts a three-wire structure, which eliminates the influence of RTD line resistance on the measurement accuracy and improves the measurement accuracy of the cold-end temperature.

[0027] 4. The thermocouple measurement and cold end compensation of the utility model adopt different AI channel sampling, so that the interference on site is not easy to affect the measurement of cold end compensation, which effectively improves the accuracy of thermocouple measurement.

[0028] 5. The utility model adopts an internal cold-end compensation module with a specific structure, which can collect the thermistor voltage through the second voltage sampling channel of the ADC module when the excitation current flows through the thermistor. The 101st resistor can be a 1 / 1000 precision resistor, and the voltage on the resistor can be measured by the third voltage sampling of the ADC module to calculate the actual value of the excitation current, which is then used to correct the excitation current fluctuation caused by temperature drift and improve the measurement accuracy of the internal cold-end compensation.

[0029] 6. The utility model can suppress the common-mode and differential-mode interference signals of the internal cold-end compensation module through the cooperation of the fifteenth capacitor, the sixteenth capacitor, the seventeenth capacitor and the twentieth capacitor, which is beneficial to improving the measurement accuracy of the cold-end temperature.

[0030] 7. The present invention adopts an external cold-end compensation module with a specific structure, in which the use of transient suppression diodes reduces the damage to the external cold-end compensation circuit caused by electrostatic discharge, lightning strikes and contactor switching, thereby improving the reliability of the device. The 102nd resistor can be a 1 / 1000 precision resistor, and the voltage on the resistor can be measured by the third voltage sampling of the ADC module to calculate the actual value of the excitation current, which is then used to correct the excitation current fluctuation caused by temperature drift, which is conducive to improving the measurement accuracy of the external cold-end compensation.

[0031] 8. The utility model can suppress the common-mode and differential-mode interference signals of the external cold-end compensation module through the 134th capacitor, the 135th capacitor, the 136th capacitor and the 139th capacitor, which is beneficial to improving the measurement accuracy of the cold-end temperature.

[0032] 9. The utility model also adds a bias voltage, which can make the measured voltage work better in the working area of ​​the operational amplifier to improve linearity and thus improve measurement accuracy. It also realizes the disconnection detection function (when the cable is normal, the voltage difference between the two ends of the TC input module is small. If the line is broken, its input voltage is stable at 1.65V). It can determine whether the thermocouple is disconnected by collecting TC voltage and bias voltage, and provide fault self-diagnosis function. The utility model also effectively smoothes the bias voltage through the filter circuit, which is conducive to improving the accuracy of thermocouple measurement.

[0033] 10. The utility model adopts a power supply module with a specific structure, which is beneficial to power supply filtering, reduces the influence of voltage fluctuation and power supply ripple, and improves system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a principle block diagram of the utility model;

[0035] Figure 2 This is a schematic diagram of the circuit structure when the utility model adopts an internal cold end compensation module;

[0036] Figure 3 This is a schematic diagram of the circuit structure when the utility model adopts an external cold end compensation module;

[0037] Figure 4 It is a schematic diagram of the circuit structure of the power module in the utility model;

[0038] Figure 5 It is a circuit structure schematic diagram of the filter circuit in the utility model. DETAILED DESCRIPTION

[0039] The utility model provides a thermocouple measuring device, such as Figure 1 As shown, it includes:

[0040] The TC input module is connected to the thermocouple and is used to collect the thermocouple voltage and perform bias processing and signal filtering conditioning on the thermocouple voltage in turn.

[0041] The cold-end compensation module is used to collect the RTD voltage of the cold end of the thermocouple on the field side.

[0042] The ADC module is connected to the TC input module, the cold end compensation module and the MCU control unit respectively, and is used to collect the RTD voltage and the thermocouple voltage after signal filtering and conditioning, and send the RTD voltage and the thermocouple voltage to the MCU control unit.

[0043] The MCU control unit is used to calculate the real voltage of the thermocouple according to the received RTD voltage and the thermocouple voltage, and obtain the actual temperature value of the thermocouple according to the real voltage.

[0044] The isolation module is arranged between the ADC module and the MCU control unit and is used to isolate the signals on the field side and the control side.

[0045] The power supply module is used to supply power to the MCU control unit, ADC module, isolation module, TC input module and cold end compensation module.

[0046] The above-mentioned cold end compensation module includes two structures, an internal cold end compensation module or an external cold end compensation module. In practical applications, the internal cold end compensation module or the external cold end compensation module can be set according to actual needs. Of course, according to certain special working conditions, the internal cold end compensation module and the external cold end compensation module can also be set at the same time. When the internal cold end compensation module and the external cold end compensation module are set at the same time, the above-mentioned ADC module, TC input module and isolation module are all set to at least two sets, and the two sets of modules can be connected to the MCU control unit through the internal cold end compensation module and the external cold end compensation module respectively to form a two-way thermocouple measurement device.

[0047] It should be noted that the ADC module in the present device includes a measurement chip U1, which has various functional pins, such as Figure 2 , 3 As shown, the 5th pin AIN1 (+) represents the positive terminal of the first voltage sampling, the 6th pin AIN1 (-) represents the negative terminal of the first voltage sampling, the 7th pin AIN2 (+) represents the positive terminal of the second voltage sampling, the 8th pin AIN2 (-) represents the negative terminal of the second voltage sampling, the 9th pin AIN3 (+) represents the positive terminal of the third voltage sampling, the 10th pin AIN3 (-) represents the negative terminal of the third voltage sampling, the 11th pin IOUT2 ​​represents the output terminal of the excitation current source, etc. In addition, Figure 2 , 3 In the figure, TC1_P indicates the positive terminal of the thermocouple, TC1_N indicates the negative terminal of the thermocouple, and REF1_1V65 indicates the reference voltage terminal of the thermocouple. RTD_P indicates the positive input terminal of the external PT100 thermistor, RTD_N indicates the negative input terminal of the external PT100 thermistor, and RTD_REF indicates the reference voltage terminal of the external PT100 thermistor.

[0048] Figure 2 The circuit structure diagram of the internal cold end compensation module according to one embodiment of the utility model is schematically shown. Figure 2As shown, the internal cold-end compensation module includes a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a one-hundred-and-first resistor R101 and a first thermistor RT1 / a second thermistor RT2, two ends of the thirteenth resistor R13 are respectively connected to the excitation current source output end of the 11th foot of the measuring chip U1 and the second voltage sampling positive end of the 7th foot, one end of the fourteenth resistor R14 is connected to the excitation current source output end of the 11th foot of the measuring chip U1 through the first thermistor RT1, and the other end of the fourteenth resistor R14 is connected to the measuring chip U1 through the first thermistor RT1. The second voltage sampling negative terminal of the 8th pin of the measuring chip U1 is connected; one end of the second thermistor RT2 and one end of the fifteenth resistor R15 are both connected between the first thermistor RT1 and the fourteenth resistor R14, and the other end of the second thermistor RT2 and the other end of the fifteenth resistor R15 are respectively connected to the excitation current source output end of the 11th pin of the measuring chip U1 and the third voltage sampling positive terminal of the 9th pin; one end of the sixteenth resistor R16 is connected to the fifteenth resistor R15 through the one hundred and first resistor R101, and the other end is connected to the third voltage sampling negative terminal of the 10th pin of the measuring chip U1.

[0049] It should be noted that the first thermistor RT1 and the second thermistor RT2 are two different packages. In actual use, only one thermistor needs to be welded, which is convenient for material selection. In actual application, the excitation current of the measurement chip U1 flows through the first thermistor RT1 or the second thermistor RT2, and the measurement chip U1 collects the voltage of the first thermistor RT1 or the second thermistor RT2 through the second voltage sampling channel formed by the second voltage sampling positive terminal and the second voltage sampling negative terminal.

[0050] According to one embodiment of the utility model, the internal cold end compensation module further includes a fifteenth capacitor C15, a sixteenth capacitor C16, a seventeenth capacitor C17 and a twentieth capacitor C20, one end of the fifteenth capacitor C15 is connected to the second voltage sampling positive end of the seventh foot of the measuring chip U1, and the other end is grounded; one end of the sixteenth capacitor C16 and one end of the seventeenth capacitor C17 are both connected to the second voltage sampling negative end of the eighth foot of the measuring chip U1, and the other end of the sixteenth capacitor C16 and the other end of the seventeenth capacitor C17 are both grounded; one end of the twentieth capacitor C20 is connected to the third voltage sampling positive end of the ninth foot of the measuring chip U1, and the other end is grounded. The utility model can suppress the common mode and differential mode interference signals of the internal cold end compensation module through the cooperation of the fifteenth capacitor C15, the sixteenth capacitor C16, the seventeenth capacitor C17 and the twenty-third capacitor C20, and improve the measurement accuracy of the cold end temperature.

[0051] Figure 3 The schematic diagram shows the circuit structure of an external cold end compensation module according to an embodiment of the present utility model. Figure 3As shown, the external cold-end compensation module includes an external PT100 thermistor, a ninety-seventh resistor R97, a ninety-eighth resistor R98, a ninety-ninth resistor R99, a one-hundredth resistor R100, a one-hundredth resistor R102, a seventeenth transient suppression diode TVS17, an eighteenth transient suppression diode TVS18 and a nineteenth transient suppression diode TVS19, the two ends of the ninety-seventh resistor R97 are respectively connected to the second voltage sampling positive terminal of the seventh foot of the measuring chip U1 and the signal positive input terminal RTD_P of the external PT100 thermistor, the two ends of the ninety-eighth resistor R98 are respectively connected to the second voltage sampling negative terminal of the eighth foot of the measuring chip U1 and the signal negative input terminal RTD_N of the external PT100 thermistor, and the two ends of the ninety-ninth resistor R99 are respectively connected to the third voltage sampling positive terminal of the ninth foot of the measuring chip U1 and the reference voltage terminal RTD_P of the external PT100 thermistor. _REF is connected, one end of the one-hundred-second resistor R102 is connected between the ninety-ninth resistor R99 and the reference voltage terminal RTD_REF of the external PT100 thermistor, and the other end of the one-hundred-second resistor R102 is connected to the third voltage sampling negative terminal of the 10th pin of the measuring chip U1 through the one-hundredth resistor R100; one end of the seventeenth transient suppression diode TVS17 is connected between the ninety-seventh resistor R97 and the signal positive input terminal RTD_P of the external PT100 thermistor, and the other end is grounded; one end of the eighteenth transient suppression diode TVS18 is connected between the ninety-eighth resistor R98 and the signal negative input terminal RTD_N of the external PT100 thermistor, and the other end is grounded; one end of the nineteenth transient suppression diode TVS19 is connected between the ninety-ninth resistor R99 and the reference voltage terminal RTD_REF of the external PT100 thermistor, and the other end is grounded.

[0052] According to an embodiment of the utility model, the above-mentioned external cold end compensation module also includes a 134th capacitor C134, a 135th capacitor C135, a 136th capacitor C136 and a 139th capacitor C139, one end of the 134th capacitor C134 is connected to the second voltage sampling positive end of the 7th pin of the measuring chip U1, and the other end is grounded; one end of the 135th capacitor C135 and the 136th capacitor C136 are both connected to the second voltage sampling negative end of the 8th pin of the measuring chip U1, and the other ends of the 135th capacitor C135 and the 136th capacitor C136 are both grounded; one end of the 139th capacitor C139 is connected to the third voltage sampling positive end of the 9th pin of the measuring chip U1, and the other end is grounded. The utility model can suppress the common mode and differential mode interference signals of the external cold end compensation module through the cooperation of the 134th capacitor C134, the 135th capacitor C135, the 136th capacitor C136 and the 139th capacitor C139, and improve the measurement accuracy of the cold end temperature.

[0053] Figure 2 , 3 The circuit structure diagram of the TC input module according to one embodiment of the utility model is schematically shown. Figure 2 , 3 As shown, the TC input module includes a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a first transient suppression diode TVS1, a second transient suppression diode TVS2 and a ninth capacitor C9, the input end and the output end of the tenth resistor R10 are respectively connected to the first voltage sampling positive end of the fifth foot of the measuring chip U1 and the positive end TC1_P of the thermocouple, the input end and the output end of the eleventh resistor R11 are respectively connected to the first voltage sampling negative end of the sixth foot of the measuring chip U1 and the negative end TC1_N of the thermocouple. The ninth resistor R9 is connected in parallel to the reference voltage terminal REF1_1V65 of the thermocouple and the input terminal of the tenth resistor R10, respectively; one end of the first transient suppression diode TVS1 is grounded, and the other end is connected to the input terminal of the tenth resistor R10; one end of the twelfth resistor R12 is grounded, and the other end is connected to the input terminal of the eleventh resistor R11; the second transient suppression diode TVS2 is connected in parallel to one side of the twelfth resistor R12; and the ninth capacitor C9 is connected between the output terminal of the tenth resistor R10 and the output terminal of the eleventh resistor R11.

[0054] Figure 2 , 3 The circuit structure diagram of the isolation module according to one embodiment of the utility model is schematically shown. Figure 2 , 3 As shown, the isolation module includes a digital isolation chip U2, an eighteenth capacitor C18 and a nineteenth capacitor C19. The digital isolation chip U2 includes pins 3, 4, 5, and 6 of the control side signal terminal, pins 1 and 7 of the control side isolation terminal, pins 11, 12, 13, and 14 of the field side signal terminal, and pins 10 and 16 of the field side isolation terminal. Pins 3, 4, 5, and 6 of the control side signal terminal and pins 11, 12, 13, and 14 of the field side signal terminal are respectively connected to pins 1, 3, 15, and 16 of the MCU control unit and the measurement chip U1. Pins 10 and 16 of the field side isolation terminal are grounded through the eighteenth capacitor C18, and pins 1 and 7 of the control side isolation terminal are grounded through the nineteenth capacitor C19.

[0055] Figure 4 The circuit structure diagram of the power supply module according to one embodiment of the utility model is schematically shown. Figure 4As shown, the power supply module includes a DC-DC power converter chip DC1 of model B0505S-1WR3, a 24th capacitor C24, a 25th capacitor C25 and a 19th resistor R19, the VCC end of the 2nd foot and the GND end of the 1st foot of the DC-DC power converter chip DC1 are connected to the power supply VCC_5V and the ground respectively, and the 24th capacitor C24 is connected between the VCC end and the GND end. In addition, the voltage output negative end of the 3rd foot of the DC-DC power converter chip DC1 is grounded, and the voltage output positive end of the 4th foot of the DC-DC power converter chip DC1 is connected to the ADC module and the isolation module respectively, and the voltage output positive end of the 4th foot is grounded through the 19th resistor R19 and the 25th capacitor C25 respectively.

[0056] According to a preferred embodiment of the present invention, an interference suppression module is further provided between the ADC module and the power supply module. Figure 2 , 3 As shown, the interference suppression module includes a magnetic bead FB1, an eleventh capacitor C11 and a fourteenth capacitor C14. The magnetic bead FB1 is connected between the 13th and 14th pins of the measuring chip U1 and the voltage output positive terminal of the DC-DC power converter chip DC1 of the power supply module. One end of the eleventh capacitor C11 and the fourteenth capacitor C14 connected in parallel is connected between the magnetic bead FB1 and the measuring chip U1, and the other end is grounded.

[0057] According to a preferred embodiment of the present invention, the present invention further comprises a bias voltage filtering circuit connected to one side of the ninth resistor. Figure 5 As shown, the filtering circuit includes a voltage stabilizer U3, a seventeenth resistor R17, an eighteenth resistor R18, a twentieth resistor R20, a twenty-first capacitor C21, a twenty-second capacitor C22 and a twenty-third capacitor C23. One end of the seventeenth resistor R17 is connected to the DC-DC power converter chip DC1 of the power supply module, and the other end is connected in three ways. The first way is connected in series with the eighteenth resistor R18 and the twentieth resistor R20 and then grounded. The second way is grounded through the twenty-first capacitor C21, the twenty-second capacitor C22 and the twenty-third capacitor C23 respectively, and the third way is connected to the ninth resistor R9; the cathode of the voltage stabilizer U3 is connected between the seventeenth resistor R17 and the eighteenth resistor R18, the anode of the voltage stabilizer U3 is grounded, and the adjustable third end of the voltage stabilizer U3 is connected between the eighteenth resistor R18 and the twentieth resistor R20.

[0058] In actual application, the utility model can isolate the power supply and signal of the field side and the control side through the isolation module.

[0059] The isolation power supply module isolates the power supply on the field side and the system side, the signal isolation module isolates the signals on the field side and the system side, the TC input signal is processed through the front-end interface and connected to the ADC module, the internal cold-end compensation thermistor signal is input to the ADC module, the external cold-end compensation thermistor signal is processed and input to the ADC module through the interface, and the ADC module is connected to the MCU control unit through the isolation module using the SPI communication interface; the MCU control unit collects TC data and chooses to use internal cold-end compensation or external cold-end compensation to obtain the actual temperature measurement value, and the MCU control unit can determine whether the TC input module interface is disconnected by judging whether the collected value is equal to the bias voltage value.

[0060] Furthermore, the specific process of the utility model is:

[0061] 1. The measuring chip U1 periodically samples the voltage inputs of pins 5-8 AIN1(+), AIN1(-), AIN2(+) and AIN2(-), reads the thermocouple input voltage and the voltage on the RTD, divides the voltage on the RTD by the excitation current to obtain the RTD resistance, and calculates the RTD temperature, i.e. the cold end temperature, by using the RTD resistance and temperature correspondence table.

[0062] 2. Each measurement cycle produces two results: thermocouple voltage V TC , and the cold junction RTD temperature T CJC .

[0063] 3. The cold end temperature measured by RTD is converted into a voltage related to the thermocouple through the thermocouple voltage and temperature correspondence table to generate V CJC .

[0064] 4. Add the two voltages and generate the thermocouple compensation voltage V 实际值 , where V CJC + V TC = V 实际值 .

[0065] 5. Finally, through the thermocouple voltage and temperature correspondence table, V 实际值 Convert to temperature and generate the temperature value of the thermocouple measuring point, that is, T 实际值 .

[0066] The above description is only a specific implementation mode of the present utility model. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all disclosed features, or all methods or steps in the process, except for mutually exclusive features or steps, can be combined in any way.

Claims

1. A thermocouple measuring device, characterized in that include: A TC input module, which is connected to a thermocouple and is used to collect the thermocouple voltage and perform bias processing and signal filtering conditioning on the thermocouple voltage in turn; A cold-end compensation module, which is used to collect the RTD voltage of the cold end of the thermocouple on the field side; An ADC module, which is connected to the TC input module, the cold end compensation module and the MCU control unit respectively, and is used to collect the RTD voltage and the thermocouple voltage after signal filtering and conditioning, and send the RTD voltage and the thermocouple voltage to the MCU control unit; The MCU control unit is used to calculate the real voltage of the thermocouple according to the received RTD voltage and the thermocouple voltage, and obtain the actual temperature value of the thermocouple according to the real voltage; An isolation module is provided between the ADC module and the MCU control unit to isolate signals on the field side and on the control side; The power supply module is used to supply power to the MCU control unit, ADC module, isolation module, TC input module and cold end compensation module.

2. A thermocouple measuring device according to claim 1, characterized in that: The cold-end compensation module is an internal cold-end compensation module, which includes a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a one-hundred-and-first resistor and a first thermistor. The two ends of the thirteenth resistor are respectively connected to the excitation current source output end and the second voltage sampling positive end of the ADC module. One end of the fourteenth resistor is connected to the excitation current source output end of the ADC module through the first thermistor, and the other end is connected to the second voltage sampling negative end of the ADC module; one end of the fifteenth resistor is connected between the first thermistor and the fourteenth resistor, and the other end is connected to the third voltage sampling positive end of the ADC module; one end of the sixteenth resistor is connected to the fifteenth resistor through the one-hundred-and-first resistor, and the other end is connected to the third voltage sampling negative end of the ADC module.

3. A thermocouple measuring device according to claim 2, characterized in that: The internal cold-end compensation module also includes a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor and a twentieth capacitor, one end of the fifteenth capacitor is connected to the second voltage sampling positive terminal of the ADC module, and the other end is grounded; one end of the sixteenth capacitor and one end of the seventeenth capacitor are both connected to the second voltage sampling negative terminal of the ADC module, and the other end of the sixteenth capacitor and the other end of the seventeenth capacitor are both grounded; one end of the twentieth capacitor is connected to the third voltage sampling positive terminal of the ADC module, and the other end is grounded.

4. A thermocouple measuring device according to claim 1, characterized in that: The cold-end compensation module is an external cold-end compensation module, and the external cold-end compensation module includes an external PT100 thermistor, a ninety-seventh resistor, a ninety-eighth resistor, a ninety-ninth resistor, a one-hundredth resistor, a one-hundredth resistor, a seventeenth transient suppression diode, an eighteenth transient suppression diode, and a nineteenth transient suppression diode, wherein both ends of the ninety-seventh resistor are respectively connected to the second voltage sampling positive terminal of the ADC module and the signal positive input terminal of the external PT100 thermistor, and both ends of the ninety-eighth resistor are respectively connected to the second voltage sampling negative terminal of the ADC module and the signal negative input terminal of the external PT100 thermistor, and both ends of the ninety-ninth resistor are respectively connected to the third voltage sampling positive terminal of the ADC module and the external PT10 0 thermistor, one end of the one hundred and second resistor is connected between the ninety-ninth resistor and the reference voltage end of the external PT100 thermistor, and the other end of the one hundredth resistor is connected to the third voltage sampling negative end of the ADC module through the one hundredth resistor; one end of the seventeenth transient suppression diode is connected between the ninety-seventh resistor and the signal positive input end of the external PT100 thermistor, and the other end is grounded; one end of the eighteenth transient suppression diode is connected between the ninety-eighth resistor and the signal negative input end of the external PT100 thermistor, and the other end is grounded; one end of the nineteenth transient suppression diode is connected between the ninety-ninth resistor and the reference voltage end of the external PT100 thermistor, and the other end is grounded.

5. A thermocouple measuring device according to claim 4, characterized in that: The external cold-end compensation module also includes a 134th capacitor, a 135th capacitor, a 136th capacitor and a 139th capacitor. One end of the 134th capacitor is connected to the second voltage sampling positive terminal of the ADC module, and the other end is grounded; one end of the 135th capacitor and the 136th capacitor are both connected to the second voltage sampling negative terminal of the ADC module, and the other ends of the 135th capacitor and the 136th capacitor are both grounded; one end of the 139th capacitor is connected to the third voltage sampling positive terminal of the ADC module, and the other end is grounded.

6. A thermocouple measuring device according to any one of claims 1 to 5, characterized in that: The TC input module includes a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a first transient suppression diode, a second transient suppression diode and a ninth capacitor, wherein the input end and the output end of the tenth resistor are respectively connected to the first voltage sampling positive end of the ADC module and the positive end of the thermocouple, the input end and the output end of the eleventh resistor are respectively connected to the first voltage sampling negative end of the ADC module and the negative end of the thermocouple, the two ends of the ninth resistor are respectively connected to the reference voltage end of the thermocouple and the input end of the tenth resistor, one end of the first transient suppression diode is grounded, and the other end is connected to the input end of the tenth resistor; one end of the twelfth resistor is grounded, and the other end is connected to the input end of the eleventh resistor, the second transient suppression diode is connected in parallel to one side of the twelfth resistor, and the ninth capacitor is connected between the output end of the tenth resistor and the output end of the eleventh resistor.

7. A thermocouple measuring device according to claim 6, characterized in that: It also includes a filter circuit of a bias voltage connected to one side of the ninth resistor, the filter circuit includes a voltage stabilizer, a seventeenth resistor, an eighteenth resistor, a twentieth resistor, a twenty-first capacitor, a twenty-second capacitor and a twenty-third capacitor, one end of the seventeenth resistor is connected to the power supply module, and the other end is connected in three ways, the first way is connected in series with the eighteenth resistor and the twentieth resistor in sequence and then grounded, the second way is grounded through the twenty-first capacitor, the twenty-second capacitor and the twenty-third capacitor respectively, and the third way is connected to the ninth resistor; the cathode of the voltage stabilizer is connected between the seventeenth resistor and the eighteenth resistor, the anode is grounded, and the adjustable third end is connected between the eighteenth resistor and the twentieth resistor.

8. A thermocouple measuring device according to any one of claims 1 to 5, characterized in that: The isolation module includes a digital isolation chip, an eighteenth capacitor and a nineteenth capacitor. The digital isolation chip includes a control side signal terminal, a control side isolation terminal, a field side signal terminal and a field side isolation terminal. The control side signal terminal and the field side signal terminal are respectively connected to the MCU control unit and the ADC module. The field side isolation terminal is grounded through the eighteenth capacitor, and the control side isolation terminal is grounded through the nineteenth capacitor.

9. A thermocouple measuring device according to claim 1, characterized in that: The power supply module includes a DC-DC power converter chip, a twenty-fourth capacitor, a twenty-fifth capacitor and a nineteenth resistor. The VCC terminal and the GND terminal of the DC-DC power converter chip are respectively connected to the power supply and the ground. The twenty-fourth capacitor is connected between the VCC terminal and the GND terminal. The voltage output positive terminal of the DC-DC power converter chip is respectively connected to the ADC module and the isolation module, and the voltage output positive terminal is grounded through the nineteenth resistor and the twenty-fifth capacitor.

10. A thermocouple measuring device according to any one of claims 1-5 and 9, characterized in that: An interference suppression module is provided between the ADC module and the power supply module, and the interference suppression module includes a magnetic bead, an eleventh capacitor and a fourteenth capacitor. The magnetic bead is connected between the ADC module and the voltage output positive terminal of the power supply module, and one end of the eleventh capacitor and the fourteenth capacitor connected in parallel is connected between the magnetic bead and the ADC module, and the other end is grounded.

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