CN115452179B - Multi-channel real-time self-calibration thermocouple cold end temperature measurement method - Google Patents

Multi-channel real-time self-calibration thermocouple cold end temperature measurement method Download PDF

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CN115452179B
CN115452179B CN202211387404.1A CN202211387404A CN115452179B CN 115452179 B CN115452179 B CN 115452179B CN 202211387404 A CN202211387404 A CN 202211387404A CN 115452179 B CN115452179 B CN 115452179B
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resistance value
resistor
temperature sensor
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CN115452179A (en
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田青林
李海勇
李仙丽
闫文吉
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Sichuan Tianli Technology Co ltd
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    • G01MEASURING; TESTING
    • G01KMEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/02Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
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    • G01KMEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
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Abstract

The invention belongs to the technical field of temperature measurement, and discloses a multi-channel real-time self-calibration thermocouple cold end temperature measurement method, which utilizes a multi-channel real-time self-calibration cold end temperature measurement circuit to carry out measurement and comprises the following steps: s100, measuring the resistance values of the resistance type temperature sensors; s200, measuring the resistance value of the calibration resistor; s300, calibrating the resistance values of the resistance type temperature sensors by using the obtained resistance values of the calibration resistors to obtain calibrated resistance values; and S400, calculating the cold end temperature of each channel at the current temperature according to the corresponding relation between the resistance value and the temperature of each calibrated resistance type temperature sensor. The invention can improve the acquisition precision and speed, and is suitable for multi-channel cold end temperature acquisition in a multi-channel thermocouple acquisition system.

Description

Multi-channel real-time self-calibration thermocouple cold end temperature measurement method
Technical Field
The invention belongs to the technical field of temperature acquisition, and particularly relates to a multi-channel real-time self-calibration thermocouple cold end temperature measurement method.
Background
Temperature measurement is an essential content in production and life, and a temperature parameter belongs to a physical quantity which cannot be directly measured and can only be indirectly obtained by measuring certain characteristic values of a substance. The temperature measurement by a thermocouple is a more common method. The thermocouple is formed by joining two conductors of different compositions into a loop, and when the temperatures of the two joints are different, electromotive force is generated in the loop, which is called thermoelectric effect, and is called thermoelectric force. Thermocouples are used for temperature measurement using this principle, wherein one end directly used for measuring the temperature of the medium is called the working end and the other end is called the cold end.
The thermoelectric voltage output by the thermocouple is a single-value function of the temperature measured by the working end, and the corresponding measured temperature can be calculated through a table look-up method or a fitting formula. The table look-up method is more common, and the cold end temperature is 0 ℃ when the table is made by a graduation table. In engineering temperature measurement, the cold end temperature changes along with the temperature of the working environment, measurement errors are introduced, and therefore cold end compensation is required to obtain an accurate temperature measurement value. At present, a plurality of cold end compensation methods are used, a common method is a thermoelectric potential correction method, the cold end temperature in the actual working condition environment is measured through a temperature sensor, then a thermoelectric potential corresponding to the temperature is obtained by an operation processing unit through a table look-up method and is used as a correction value, and the measured thermocouple potential and the correction value are added to obtain the thermoelectric potential corresponding to the measured temperature.
When the thermocouple is used for measuring temperature, the temperature of the cold end needs to be measured simultaneously, and the measurement precision of the cold end also determines the overall precision of the temperature measuring system. For the cold end temperature measurement in a multi-channel thermocouple temperature measurement system with more than four channels, the currently common scheme is to directly acquire a temperature value by using a digital temperature sensor and a processor. The digital temperature sensor generally has the precision of +/-0.5 ℃, and is not suitable for a high-precision temperature measurement system; the sensor is used for testing absolute temperature, the accuracy is determined by factory delivery, and recalibration is difficult to realize during use; when in use, the peripheral circuit is not easy to integrate with the wiring terminal.
Disclosure of Invention
In order to solve the problems, the invention provides a multi-channel real-time self-calibration thermocouple cold end temperature measurement method which can improve the acquisition precision and speed and is suitable for multi-channel cold end temperature acquisition in a multi-channel thermocouple acquisition system.
In order to achieve the purpose, the invention adopts the technical scheme that: a multi-channel real-time self-calibration thermocouple cold end temperature measurement method utilizes a multi-channel real-time self-calibration cold end temperature measurement circuit to carry out measurement, and comprises the following steps: the resistance-type temperature sensors correspond to thermocouple wiring terminals of the multi-channel thermocouple acquisition system and are used for sensing the temperature of the wiring terminals; each resistance-type temperature sensor is connected with an electronic switch matrix, the electronic switch matrix is connected to a signal conditioning circuit, and the signal conditioning circuit is connected to an analog-to-digital converter; the constant current source is connected to the resistance type temperature sensor group and the calibration resistor through a switch in the electronic switch matrix; calibrating a resistor, and connecting the resistor into an electronic switch matrix; the reference resistor is connected to the reference end of the analog-to-digital converter; the method comprises the following steps:
s100, measuring the resistance values of the resistance type temperature sensors;
s200, measuring the resistance value of the calibration resistor;
s300, calibrating the resistance values of the resistance type temperature sensors by using the obtained actual resistance values of the calibration resistors to obtain calibrated resistance values;
and S400, calculating the corresponding relation between the actual resistance values of the calibrated resistance temperature sensors and the temperature, and calculating the cold end temperature of each channel at the current temperature.
Further, in the step S100, measuring a resistance signal of each resistance temperature sensor includes:
s101, controlling an electronic switch matrix to enable a constant current source to flow through a plurality of resistance type temperature sensors and a reference resistor and then flow to the ground;
s102, keeping the current flow direction unchanged, simultaneously controlling an electronic switch matrix to realize that leads at two ends of a single resistance-type temperature sensor are connected to a signal conditioning circuit, and transmitting collected signals communicated with the resistance-type temperature sensor to the signal conditioning circuit;
s103, the acquired signal is filtered and amplified by a signal conditioning circuit and then is connected to an analog-to-digital converter through a lead;
s104, the analog-to-digital converter takes the voltage at two ends of the reference resistor as a reference voltage, the lead access voltage is measured in a proportional measurement mode, and the processor acquires data from the analog-to-digital converter and calculates the resistance value of the access resistance type temperature sensor;
and S105, controlling the electronic switch matrix to sequentially realize the access of the resistance-type temperature sensors, and repeatedly executing S102-S104 according to the number of the resistance-type temperature sensors to sequentially obtain the resistance values of the resistance-type temperature sensors.
Further, the plurality of resistance type temperature sensors are divided into a plurality of groups, and the resistance type temperature sensors in each group are mutually connected in series;
in step S105, the electronic switch matrix is controlled to sequentially realize the access of all resistance type temperature sensors in the current group, and S102-S104 are repeatedly executed according to the number of all resistance type temperature sensors in the current group to sequentially obtain the resistance values of the resistance type temperature sensors in the group;
and repeatedly executing S102-S105 according to the group number to sequentially obtain the resistance values of all the resistance type temperature sensors.
Further, in the step S200, measuring the resistance value of the calibration resistor includes the steps of:
s201, controlling an electronic switch matrix to enable a constant current source to flow through a calibration resistor and a reference resistor and then flow to the ground;
s202, keeping the current flow direction unchanged, and simultaneously realizing that leads at two ends of a single calibration resistor are connected to a signal conditioning circuit by controlling an electronic switch matrix;
s203, the signal is filtered and amplified by the signal conditioning circuit and then is connected to the analog-to-digital converter through a lead;
s204, the analog-to-digital converter takes the voltage at two ends of the reference resistor as a reference voltage, the lead access voltage is measured in a proportional measurement mode, and the processor acquires data from the analog-to-digital converter and calculates the resistance value of the access calibration resistor;
and S205, controlling the electronic switch matrix to sequentially realize the access of the first calibration resistor and the second calibration resistor, and sequentially obtaining the resistance values of the first calibration resistor and the second calibration resistor by repeatedly executing the actions of S202-S204.
Further, in the step S300, the resistance values of the resistance temperature sensors are calibrated by obtaining the resistance values of the calibration resistors, and the obtained calibrated resistance values are obtained, including the steps of:
s301, recording the resistance value of each resistance type temperature sensor measured in the step S100
Figure 649050DEST_PATH_IMAGE001
~
Figure 136663DEST_PATH_IMAGE002
N is the number of the resistance temperature sensors, and the resistance value of the calibration resistor measured in step S200 is recorded as
Figure 814769DEST_PATH_IMAGE003
And
Figure 46030DEST_PATH_IMAGE004
(ii) a The actual resistance value of each resistance type temperature sensor after calibration is recorded as R 1 Rn, the preset actual value of the calibration resistance is
Figure 493192DEST_PATH_IMAGE005
And
Figure 902439DEST_PATH_IMAGE006
s302, from known
Figure 802262DEST_PATH_IMAGE007
And
Figure 571635DEST_PATH_IMAGE008
two points, confirming the resistance value measured by the acquisition circuit through linear fitting
Figure 138882DEST_PATH_IMAGE009
And actual resistance value
Figure 968298DEST_PATH_IMAGE010
The corresponding relation of (2) is as follows:
Figure 89838DEST_PATH_IMAGE011
will measure the resistance value
Figure 725219DEST_PATH_IMAGE001
~
Figure 84656DEST_PATH_IMAGE002
The actual resistance value R can be obtained by substituting the above formula in sequence 1 Rn; after being calibratedAnd obtaining the calibrated resistance values of all the resistance temperature sensors.
The beneficial effects of the technical scheme are as follows:
the invention realizes high-precision cold end temperature measurement and is convenient for integrated installation in the system; the resistance type temperature sensors are grouped and connected in series and are matched with an electronic switch matrix to realize multi-channel simultaneous measurement; the high-precision calibration resistor is permanently connected to the electronic switch matrix to form a self-calibration circuit, resistance value acquisition of the resistance temperature sensor, resistance value acquisition of the calibration resistor, real-time resistance value calibration and temperature calculation are completed in a timed and circulating mode, a real-time self-calibration function is achieved, and acquisition precision is further improved. The invention is especially suitable for multi-channel cold end temperature measurement in a multi-channel thermocouple acquisition system, and is also suitable for a common multi-channel resistance acquisition system or device.
The invention eliminates the line resistance introduced error and realizes the high-precision cold end temperature measurement; the high-precision calibration resistor is permanently connected to the electronic switch matrix and the implementation method is used for completing real-time self calibration, eliminating circuit errors and further improving the acquisition precision to be +/-0.15 ℃.
The invention is not limited by the length of wiring and is convenient to integrate with a thermocouple test terminal.
Drawings
FIG. 1 is a schematic flow chart of a multi-channel real-time self-calibrated thermocouple cold end temperature measurement method of the present invention;
fig. 2 is a schematic structural diagram of a multi-channel real-time self-calibration cold end temperature measurement circuit in the embodiment of the invention.
Wherein: the circuit comprises a processor 1, an analog-to-digital converter 2, a signal conditioning circuit 3, a constant current source 4, an electronic switch matrix 5, a resistance temperature sensor 6, a first calibration resistor 7, a second calibration resistor 8 and a reference resistor 9.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described with reference to the accompanying drawings.
In this embodiment, referring to fig. 2, the measurement is performed by using a multi-channel real-time self-calibration cold-end temperature measurement circuit, which includes: the resistance temperature sensors 6 correspond to thermocouple wiring terminals of the multi-channel thermocouple acquisition system and are used for sensing the temperature of the wiring terminals; each resistance-type temperature sensor 6 is connected to an electronic switch matrix 5, the electronic switch matrix 5 is connected to a signal conditioning circuit 3, and the signal conditioning circuit 3 is connected to an analog-to-digital converter 2; the constant current source 4 is connected to the group of resistance type temperature sensors 6 and the calibration resistor through the switches in the electronic switch matrix 5; calibrating the resistor, and connecting the electronic switch matrix 5; and a reference resistor 9 connected to the reference terminal of the analog-to-digital converter 2.
As shown in FIG. 1, the invention provides a multi-channel real-time self-calibration thermocouple cold end temperature measurement method, which comprises the following steps:
s100, measuring the resistance values of the resistance type temperature sensors 6;
s200, measuring the resistance value of the calibration resistor;
s300, calibrating the resistance value of each resistance type temperature sensor 6 by using the obtained resistance value of the calibration resistor, and obtaining the calibrated resistance value;
and S400, calculating the current cold end temperature of each channel according to the corresponding relation between the resistance value and the temperature of each calibrated resistance temperature sensor 6.
As an optimization solution of the above embodiment, in the step S100, measuring the resistance value signal of each resistance temperature sensor 6 includes the steps of:
s101, controlling the electronic switch matrix 5 to enable the constant current source 4 to flow through the plurality of resistance-type temperature sensors 6 and the reference resistor 9 and then flow to the ground;
s102, keeping the current flow direction unchanged, simultaneously controlling the electronic switch matrix 5 to realize that leads at two ends of a single resistance-type temperature sensor 6 are connected to the signal conditioning circuit 3, and transmitting the collected signals communicated with the resistance-type temperature sensor 6 to the signal conditioning circuit 3;
s103, the collected signal is filtered and amplified by the signal conditioning circuit 3 and then is connected to the analog-to-digital converter 2 through a lead;
s104, the analog-to-digital converter 2 measures the lead access voltage in a proportional measurement mode by taking the voltage at two ends of the reference resistor 9 as a reference voltage, and the processor 1 acquires data from the analog-to-digital converter 2 and calculates the resistance value of the access resistance type temperature sensor 6;
and S105, controlling the electronic switch matrix 5 to sequentially realize the access of the resistance-type temperature sensors 6, and repeatedly executing S102-S104 according to the number of the resistance-type temperature sensors 6 to sequentially obtain the resistance values of the resistance-type temperature sensors 6.
As an optimization scheme of the above embodiment, the plurality of resistance temperature sensors 6 are divided into a plurality of groups, and the resistance temperature sensors 6 in each group are connected in series. R1, R2, R3, R4 are shown as one group in FIG. 2
S101, controlling the electronic switch matrix 5 to enable the constant current source 4 to flow through the connection line, for example: AN0, a plurality of resistive temperature sensors 6, e.g., R1, R2, R3, R4, reference resistor 9
Figure 881710DEST_PATH_IMAGE012
Then to ground;
s102, keeping the current flow direction unchanged, and simultaneously controlling the electronic switch matrix 5 to realize the lead wires at two ends of the single resistance-type temperature sensor 6, such as: AN1 and AN2 are connected to the signal conditioning circuit 3, and transmit the collected signal communicated with the resistance-type temperature sensor 6 to the signal conditioning circuit 3;
s103, the acquired signal is filtered and amplified by the signal conditioning circuit 3 and then is connected to the analog-to-digital converter 2 through a lead;
s104, the analog-to-digital converter 2 uses the reference resistor 9
Figure 756126DEST_PATH_IMAGE012
The voltages at the two ends are reference voltages, the lead access voltage is measured in a proportional measurement mode, and the processor 1 acquires data from the analog-to-digital converter 2 and calculates the resistance value of the access resistance type temperature sensor 6;
and S105, controlling the electronic switch matrix 5 to sequentially realize the access of the resistance temperature sensors 6R1, R2, R3 and R4 in the group, and repeatedly executing S102-S104 according to the number of the resistance temperature sensors 6 to sequentially obtain the resistance values of the resistance temperature sensors 6R1, R2, R3 and R4.
Control ofThe electronic switch matrix 5 enables the constant current source 4 to flow through the connection lines, for example: AN6, resistance temperature sensor 6 are grouped, for example: r5, R6, R7, R8, reference resistance 9
Figure 116569DEST_PATH_IMAGE012
And then to ground. The resistances of R5, R6, R7 and R8 can be obtained by repeatedly executing S102 to S104.
As an optimized solution of the above embodiment, in the step S200, measuring the resistance value of the calibration resistor includes the steps of:
s201, controlling the electronic switch matrix 5 to enable the constant current source 4 to flow through the connection line, for example: AN12, calibration resistance
Figure 392829DEST_PATH_IMAGE013
Figure 360785DEST_PATH_IMAGE014
Reference resistor 9
Figure 660179DEST_PATH_IMAGE012
Then to ground;
s202, keeping the current flow direction unchanged, and simultaneously realizing that leads at two ends of a single calibration resistor are connected to the signal conditioning circuit 3 by controlling the electronic switch matrix 5;
s203, the signal is filtered and amplified by the signal conditioning circuit 3 and then is connected to the analog-to-digital converter 2 through a lead;
s204, the analog-to-digital converter 2 uses the reference resistor 9
Figure 637363DEST_PATH_IMAGE012
The voltages at the two ends are reference voltages, the lead access voltage is measured in a proportional measurement mode, and the processor 1 acquires data from the analog-to-digital converter 2 and calculates the resistance value of the access calibration resistor;
s205, controlling the electronic switch matrix 5 to sequentially realize the first calibration resistor 7
Figure 502551DEST_PATH_IMAGE015
A second calibration resistor 8
Figure 844670DEST_PATH_IMAGE016
Accessing, and repeatedly executing the actions S202-S204 to obtain the first calibration resistor 7
Figure 693677DEST_PATH_IMAGE015
And a second calibration resistor 8
Figure 208972DEST_PATH_IMAGE016
Is measured.
As an optimized solution of the above embodiment, in the step S300, the resistance values of the resistance temperature sensors 6 are calibrated by obtaining the resistance values of the calibration resistors, and the step of obtaining the calibrated resistance values includes the steps of:
s301, the resistance values of the respective resistance temperature sensors 6 measured in step S100 are recorded as
Figure 131929DEST_PATH_IMAGE017
N is the number of each resistance temperature sensor 6, and the resistance value of the calibration resistor measured in step S200 is recorded as
Figure 441688DEST_PATH_IMAGE003
And
Figure 777991DEST_PATH_IMAGE004
(ii) a The actual resistance values of the respective resistance temperature sensors 6 after calibration are recorded as R 1 Rn, the preset actual value of the calibration resistor is
Figure 785393DEST_PATH_IMAGE015
And
Figure 890752DEST_PATH_IMAGE016
the first calibration resistor 7 is a high-precision resistor for calibrating a full range
Figure 574674DEST_PATH_IMAGE015
=2k Ω, the second calibration resistor 8 being a high-precision resistor for calibrating the zero point
Figure 398274DEST_PATH_IMAGE016
=1kΩ。
S302, from known
Figure 989792DEST_PATH_IMAGE018
And
Figure 887341DEST_PATH_IMAGE019
two points, confirming the resistance value measured by the acquisition circuit through linear fitting
Figure 70060DEST_PATH_IMAGE020
The corresponding relation with the actual resistance R is as follows:
Figure 53060DEST_PATH_IMAGE011
will measure the resistance value
Figure 448269DEST_PATH_IMAGE017
The actual resistance value R can be obtained by substituting the above formula in sequence 1 ~R n (ii) a And obtaining the calibrated resistance values of all the resistance type temperature sensors 6 after calibration.
As an optimization solution of the above embodiment, in step S400, the processor 1 calculates the current cold end temperature of the 8 channels by using the corresponding relationship between the resistance value and the temperature of the type-selecting resistance temperature sensor 6, for example, 1.097347k Ω corresponds to 25 ℃.
And circularly executing the steps S100 to S400 at the fixed time of 1 second, and realizing the 8-channel real-time self-calibration cold end temperature acquisition.
The invention realizes high-precision cold end temperature measurement and is convenient for integrated installation in the system; RTD groups are connected in series and are matched with an electronic switch matrix 5 to realize multi-channel simultaneous measurement; the high-precision calibration resistor is permanently connected to the electronic switch matrix 5 to form a self-calibration circuit, RTD resistance value acquisition, calibration resistor resistance value acquisition, resistance value real-time calibration and temperature calculation are completed in a timed and circulating mode, a real-time self-calibration function is achieved, and acquisition precision is further improved. The invention is particularly suitable for multi-channel cold end temperature measurement in a multi-channel thermocouple acquisition system, and is also suitable for a common multi-channel resistance acquisition system or device.
The foregoing shows and describes the general principles and features of the present invention, together with the advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are given by way of illustration of the principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, and such changes and modifications are within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (4)

1. A multi-channel real-time self-calibration thermocouple cold end temperature measurement method is characterized in that a multi-channel real-time self-calibration cold end temperature measurement circuit is used for measurement, and the method comprises the following steps: the resistance temperature sensors (6) correspond to thermocouple wiring terminals of the multi-channel thermocouple acquisition system and are used for sensing the temperature of the wiring terminals; each resistance-type temperature sensor (6) is connected with an electronic switch matrix (5), the electronic switch matrix (5) is connected to a signal conditioning circuit (3), and the signal conditioning circuit (3) is connected to an analog-to-digital converter (2); the constant current source (4) is connected to the resistor type temperature sensor (6) group and calibration resistor after passing through the switch in the electronic switch matrix (5); calibrating a resistor, and connecting an electronic switch matrix (5); and a reference resistor (9) connected to the reference end of the analog-to-digital converter (2); the method comprises the following steps:
s100, measuring the resistance value of each resistance type temperature sensor (6);
s200, measuring the resistance value of the calibration resistor, comprising the following steps:
s201, controlling an electronic switch matrix (5) to enable a constant current source (4) to flow through a calibration resistor and a reference resistor (9) and then flow to the ground;
s202, keeping the current flow direction unchanged, and simultaneously realizing that leads at two ends of a single calibration resistor are connected to a signal conditioning circuit (3) by controlling an electronic switch matrix (5);
s203, the signal is filtered and amplified by the signal conditioning circuit (3) and then is connected to the analog-to-digital converter (2) through a lead;
s204, the analog-to-digital converter (2) takes voltages at two ends of the reference resistor (9) as reference voltages, the lead access voltage is measured in a proportional measurement mode, and the processor (1) acquires data from the analog-to-digital converter (2) and calculates the resistance value of the access calibration resistor;
s205, controlling the electronic switch matrix (5) to sequentially realize the access of the first calibration resistor (7) and the second calibration resistor (8), and sequentially obtaining the resistance values of the first calibration resistor (7) and the second calibration resistor (8) by repeatedly executing the actions of S202-S204;
s300, calibrating the resistance value of each resistance type temperature sensor (6) by using the obtained calibration resistance value to obtain a calibrated actual resistance value;
and S400, calculating the cold end temperature of each channel at the current temperature according to the corresponding relation between the actual resistance value and the temperature of each calibrated resistance type temperature sensor (6).
2. The method for measuring the cold end temperature of the thermocouple through multi-channel real-time self-calibration according to claim 1, wherein in the step S100, the resistance value signal of each resistance temperature sensor (6) is measured, and the method comprises the following steps:
s101, controlling an electronic switch matrix (5) to enable a constant current source (4) to flow through a plurality of resistance type temperature sensors (6) and a reference resistor (9) and then flow to the ground;
s102, keeping the current flow direction unchanged, simultaneously controlling an electronic switch matrix (5) to realize that leads at two ends of a single resistance-type temperature sensor (6) are connected to a signal conditioning circuit (3), and transmitting collected signals communicated with the resistance-type temperature sensor (6) to the signal conditioning circuit (3);
s103, the collected signals are filtered and amplified by the signal conditioning circuit (3) and then are connected to the analog-to-digital converter (2) through a lead;
s104, the analog-to-digital converter (2) takes voltages at two ends of the reference resistor (9) as reference voltages, the lead access voltage is measured in a proportional measurement mode, and the processor (1) acquires data from the analog-to-digital converter (2) and calculates the resistance value of the access resistance type temperature sensor (6);
and S105, controlling the electronic switch matrix (5) to sequentially realize the access of the resistance temperature sensors (6), and repeatedly executing S102-S104 according to the number of the resistance temperature sensors (6) to sequentially obtain the resistance values of the resistance temperature sensors (6).
3. The method for measuring the cold end temperature of the thermocouple through multi-channel real-time self-calibration according to claim 2, characterized in that the plurality of resistance temperature sensors (6) are divided into a plurality of groups, and the resistance temperature sensors (6) in each group are connected in series; in step S105, the electronic switch matrix (5) is controlled to sequentially realize the access of each resistance type temperature sensor (6) in the current group, and S102-S104 are repeatedly executed according to the number of each resistance type temperature sensor (6) in the current group to sequentially obtain the resistance value of the resistance type temperature sensor (6) in the group;
and (5) repeatedly executing S102-S105 according to the number of the groups to sequentially obtain the resistance values of all the resistance type temperature sensors (6).
4. The multi-channel real-time self-calibration thermocouple cold junction temperature measuring method according to any one of claims 1 to 3, wherein in the step S300, the actual resistance value of each resistance temperature sensor (6) is calibrated by obtaining the actual resistance value of the calibration resistor, and the obtained calibrated resistance value comprises the steps of:
s301, the resistance value of each resistance type temperature sensor (6) measured in the step S100 is recorded as R' 1 ~R′ n N is the number of the resistance type temperature sensors (6), and the resistance value of the calibration resistor measured in the step S200 is recorded as R' F And R' Z (ii) a The actual resistance value of each resistance type temperature sensor (6) after calibration is recorded as R 1 Rn, the preset actual value of the calibration resistor is R F And R Z
S302, from known (R' Z ,R Z ) And (R' F ,R F ) Two points, the corresponding relation between the resistance value R' measured by the acquisition circuit and the actual resistance value R is confirmed through linear fitting as follows:
Figure FDA0004009902520000021
will measure the resistance value R' 1 ~R′ n The actual resistance value R can be obtained by substituting the above formula in sequence 1 -Rn; and obtaining the calibrated resistance values of all the resistance-type temperature sensors (6) after calibration.
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