Thermocouple signal generating device and signal generating method

Abstract

The invention relates to the technical field of signal generation devices, and discloses a thermocouple signal generation device and a signal generation method.The thermocouple signal generation device comprises a human-computer interface, a logic processing unit and an output interface unit, selecting a test channel type according to the parameter setting instruction, and performing parameter setting on a corresponding test channel; the logic processing unit is used for performing nested multiplication according to the types of the test channels and the parameters corresponding to the test channels, and performing calculation to obtain thermocouple electromotive force of each test channel; and the output interface unit is used for providing a signal source and outputting the electromotive force of the thermocouple of each test channel. And by adopting a nested multiplication mode, the number of times of data processing calculation is greatly reduced, the rounding error brought in the calculation process is greatly reduced, and the calculation precision of the electromotive force of the thermocouple is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of signal generating devices, and in particular to a thermocouple signal generating device and a signal generating method. Background Art

[0002] Thermocouple signal generators are mainly used for calibration of thermocouple measurement channels or signal simulation. The calibration of thermocouple channels has high requirements on the accuracy and stability of thermocouple signal generators. Currently, most commonly used thermocouple signal generators use thermocouple simulation devices to simulate thermocouple signals, but the actual output of thermocouple voltage signals by these devices has poor accuracy and large errors. Summary of the invention

[0003] In view of this, the present invention provides a thermocouple signal generating device and a signal generating method to solve the problem of poor accuracy of the actual output thermocouple voltage signal in the related art.

[0004] In a first aspect, the present invention provides a thermocouple signal generating device, the device comprising: a human-machine interface, a logic processing unit and an output interface unit, wherein:

[0005] The human-machine interface is used to receive parameter setting instructions, select the test channel type according to the parameter setting instructions, and set parameters for the corresponding test channel;

[0006] The logic processing unit is used to perform nested multiplication operations according to the test channel type and the parameters corresponding to the test channel to calculate the thermocouple electromotive force of each test channel;

[0007] The output interface unit is used to provide a signal source and output the thermocouple electromotive force of each test channel.

[0008] A thermocouple signal generating device provided by the present invention adopts a nested multiplication method to greatly reduce the number of data processing calculations, greatly reduce the rounding error caused by the calculation process, and greatly improve the calculation accuracy of the thermocouple electromotive force.

[0009] In an optional implementation, the logic processing unit is further used to perform deviation correction on the thermocouple electromotive force of each test channel according to the output error of each test channel type.

[0010] The innovative use of self-written programs has been used to perform secondary corrections on existing errors, further improving the accuracy of the thermocouple electromotive force.

[0011] In an optional implementation, the nested multiplication formula is as follows:

[0012] E={…[(a n t+a n-1)t+a n-2 ]t+…+a 1}t+a 0

[0013] Where E is the thermocouple electromotive force, t is the temperature value to be simulated, and a i is the coefficient of the i-th term of the polynomial, and n is the order of the polynomial.

[0014] In an optional implementation, the calculation formula of the thermocouple electromotive force after deviation correction is as follows:

[0015]

[0016] Where u is the thermocouple electromotive force after deviation correction and δ is the offset.

[0017] In an alternative embodiment, the offset is determined based on the thermocouple type.

[0018] In an optional implementation, the signal source of the thermocouple electromotive force is a voltage generator or a thermocouple signal simulation device.

[0019] In an optional implementation, the test channel may be a single channel or multiple channels.

[0020] The multi-channel, multi-type, high-precision thermocouple signal generating device provided in the embodiment of the present invention solves the problem that thermocouples cannot be simulated in multiple channels.

[0021] In a second aspect, the present invention provides a method for generating a thermocouple signal, the method comprising:

[0022] Receive a parameter setting instruction, select a test channel type according to the parameter setting instruction, and set parameters for the corresponding test channel;

[0023] Perform nested multiplication operations according to the test channel type and the parameters corresponding to the test channel to calculate the thermocouple electromotive force of each test channel;

[0024] Output the thermocouple electromotive force of each test channel.

[0025] The invention provides a method for generating a thermocouple signal, which uses a nested multiplication method to greatly reduce the number of data processing calculations, greatly reduce the rounding error caused by the calculation process, and greatly improve the calculation accuracy of the thermocouple electromotive force. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 is a schematic diagram of a thermocouple signal generating device according to an embodiment of the present invention;

[0028] Figure 2 is a comparison diagram of an offset correction curve and an actual offset according to an embodiment of the present invention;

[0029] Figure 3 4 is a flow chart of a method for generating a thermocouple signal according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] The present invention provides a thermocouple signal generating device, such as Figure 1 As shown, it includes: a human-machine interface, a logic processing unit and an output interface unit. Among them, the human-machine interface is used to receive parameter setting instructions, select the test channel type according to the parameter setting instructions, and set parameters for the corresponding test channels. The logic processing unit is used to perform nested multiplication operations according to the test channel type and the parameters corresponding to the test channel to calculate the thermocouple electromotive force of each test channel. The output interface unit is used to provide a signal source and output the thermocouple electromotive force of each test channel.

[0035] Specifically, the human-machine interface receives the parameter setting instruction sent by the host computer, sets the number of channels to be simulated output according to the parameter setting instruction, and sets the parameters of the corresponding test channels. Among them, the specific setting parameters are as follows: setting the temperature unit, Celsius, Fahrenheit, Kelvin can be selected; setting the compensation type, fixed value compensation such as fixed compensation of 25°C, channel compensation (multiple channels can set the compensation value for each output separately); various common thermocouple types can be set, including R, S, B, J, T, E, K, N, C, A and other thermocouple types. At the same time, the temperature setting value, name, temperature range, description, etc. of a single channel or multiple channels can be set, and single-channel output or multiple channels can be set to output simultaneously. Among them, the embodiment of the present invention directly realizes the screen and logic processing functions through self-compiled programs, and transmits parameters such as setting values ​​to downstream modules through communication.

[0036] The logic processing unit receives the parameter setting values ​​sent by the human-machine interface and performs logical operations based on the set input. According to the national standard document GB / T16839.1-2018, the logic processing unit automatically calculates the electromotive force corresponding to the set temperature.

[0037] A thermocouple signal generating device provided by the present invention adopts a nested multiplication method to greatly reduce the number of data processing calculations, greatly reduce the rounding error caused by the calculation process, and greatly improve the calculation accuracy of the thermocouple electromotive force.

[0038] In an optional implementation, the nested multiplication formula is as follows:

[0039] E={…[(a n t+a n-1 )t+a n-2 ]t+…+a 1}t+a 0 (1)

[0040] Where, E is the electromotive force of the thermocouple, in microvolts (μV); t is the temperature value to be simulated, in degrees Celsius (℃); a i is the coefficient of the i-th term of the polynomial, and n is the order of the polynomial.

[0041] Specifically, the nested multiplication calculation in the formula can avoid rounding errors, that is, n t product plus a n-1 , multiply the result by t, repeat this step, and finally add a 0 After measurement, the channel accuracy of the device can reach more than 0.1%. Taking K-type thermocouple as an example, the K-type thermocouple graduation function is shown in the following table:

[0042] Table 1 K-type thermocouple graduation function

[0043]

[0044] In an optional implementation, the logic processing unit is further configured to perform deviation correction on the thermocouple electromotive force of each test channel according to the output error of each test channel type.

[0045] Specifically, after a large number of tests and verifications, the result based on the above nested multiplication calculation still has an offset, which is concentrated between 0℃ and 300℃. When a set value (temperature) is input, the electromotive force (unit, mV) calculated by the logic processing unit plus the offset δ (unit, mV) corresponding to the set value is the accurate electromotive force requirement. When the set value t is not between 0 and 300℃, the electromotive force is directly output according to formula 1.

[0046] The formula for calculating the thermocouple electromotive force after deviation correction is as follows:

[0047]

[0048] Where u is the thermocouple electromotive force after deviation correction and δ is the offset.

[0049] Furthermore, the offset is determined according to the type of thermocouple. Taking the K-type thermocouple as an example, a large amount of experimental offset data is analyzed and integrated to fit the offset curve, and then the offset correction of the thermocouple electromotive force is performed according to the fitted offset curve. After the offset correction, the accuracy of the nested multiplication calculation can be further improved, and the accuracy can reach more than 0.1%. This method can be extended to other types of thermocouples, including R, S, B, J, T, E, K, N, C, A, etc. The offset of the nested multiplication calculation result is shown in the following table:

[0050] Table 2 Nested multiplication calculation result offset

[0051] Temperature(℃) Offset δ Temperature(℃) Offset δ 0 0.02 160 0.12 10 0.02 170 0.11 20 0.04 180 0.1 30 0.04 190 0.08 40 0.05 200 0.07 50 0.06 210 0.06 60 0.06 220 0.05 70 0.07 230 0.03 80 0.08 240 0.02 90 0.09 250 0.02 100 0.1 260 0.02 110 0.1 270 0.01 120 0.11 280 0.01 130 0.11 290 0.01 140 0.11 300 0.01 150 0.12

[0052] According to Table 2, the deviation correction formula is fitted as shown below.

[0053] δ=-0.00000002t 6 +0.000002t 5 -0.00006t 4 +0.0009t 3 -0.0066t 2 +

[0054] 0.0274t-0.0063(3)

[0055] From equations (1) and (3), the corrected electromotive force u (unit, mV) corresponding to the required temperature value t, i.e., the electromotive force output by the device, can be obtained as follows:

[0056]

[0057] The comparison between the offset correction curve and the actual offset is shown in the figure below: Figure 2 As shown, the dotted line is the offset correction curve, and the solid line is the actual offset. Figure 2 It can be seen that after the offset correction, the deviation between the offset correction curve and the actual offset is negligible, which further improves the accuracy of the thermocouple electromotive force.

[0058] In an optional implementation, the signal source of the thermocouple electromotive force is a voltage generator or a thermocouple signal simulation device.

[0059] Specifically, the electromotive force calculated by nested multiplication and superimposed with the electromotive force of the error offset is sent to the output interface unit to output the electromotive force, and the accuracy level can reach more than 0.05%. The output interface unit includes an electromotive force signal source and related terminals, etc. The signal source of the required electromotive force adopts a voltage generator or a thermocouple signal simulation device. The embodiment of the present invention adopts a PXI thermocouple simulator, which can output multi-channel millivolt signals at the same time.

[0060] In an optional implementation, the test channel may be a single channel or multiple channels.

[0061] Specifically, the multi-channel, multi-type, high-precision thermocouple signal generating device provided in the embodiment of the present invention solves the problem that thermocouples cannot be simulated in multiple channels.

[0062] In an embodiment of the present invention, nested multiplication is used to calculate the thermocouple electromotive force, and then deviation correction is performed according to each type of output error, so that multi-channel, multi-type, high-precision thermocouple signal simulation output can be achieved, which is convenient for laboratory and engineering site simulation and improves efficiency.

[0063] The present invention provides a method for generating a thermocouple signal, such as Figure 3 As shown, the following steps are included:

[0064] Step S1, receiving a parameter setting instruction, selecting a test channel type according to the parameter setting instruction, and performing parameter setting on a corresponding test channel.

[0065] The human-machine interface receives the parameter setting instruction sent by the host computer, sets the number of channels to be simulated output according to the parameter setting instruction, and sets the parameters of the corresponding test channels. Among them, the test channel can select a single channel or multiple channels. Further, the specific setting parameters are as follows: set the temperature unit, and you can choose Celsius, Fahrenheit, Kelvin; set the compensation type, and you can choose fixed value compensation such as fixed compensation of 25°C, channel compensation (multiple channels can set the compensation value separately for each output); you can set various common thermocouple types, including R, S, B, J, T, E, K, N, C, A and other thermocouple types. At the same time, you can set the temperature setting value, name, temperature range, description, etc. of a single channel or multiple channels, and you can set single channel output or multiple channels to output simultaneously. Among them, the embodiment of the present invention directly realizes the screen and logic processing functions through self-compiled programs, and transmits parameters such as set values ​​to downstream modules through communication.

[0066] Step S2, performing nested multiplication operations according to the test channel type and the parameters corresponding to the test channel, and calculating the thermocouple electromotive force of each test channel.

[0067] The logic processing unit receives the parameter setting values ​​sent by the human-machine interface and performs logical operations based on the set input. According to the national standard document GB / T16839.1-2018, the logic processing unit automatically calculates the electromotive force corresponding to the set temperature.

[0068] The nested multiplication formula is as follows:

[0069] E={…[(a n t+a n-1 )t+a n-2 ]t+…+a 1}t+a 0 (1)

[0070] Where, E is the electromotive force of the thermocouple, in microvolts (μV); t is the temperature value to be simulated, in degrees Celsius (℃); a i is the coefficient of the i-th term of the polynomial, and n is the polynomial order. The nested multiplication method is used to avoid rounding errors. n t product plus a n-1 , multiply the result by t, repeat this step, and finally add a 0 .

[0071] After a lot of testing and verification, the result based on the above nested multiplication calculation still has an offset, which is concentrated between 0℃ and 300℃. When a set value (temperature) is input, the electromotive force (unit, mV) calculated by the logic processing unit plus the offset δ (unit, mV) corresponding to the set value is the accurate electromotive force requirement. When the set value t is not between 0 and 300℃, the electromotive force is directly output according to formula 1.

[0072] The formula for calculating the thermocouple electromotive force after deviation correction is as follows:

[0073]

[0074] Where u is the thermocouple electromotive force after deviation correction and δ is the offset.

[0075] The accuracy level of the electromotive force calculated by nested multiplication and superimposed with the error offset can reach above 0.05%.

[0076] Step S3, outputting the thermocouple electromotive force of each test channel.

[0077] Specifically, the output interface unit is used to provide a signal source and multi-channel signal output. The output interface unit includes an electromotive force signal source and related terminals, etc. The required electromotive force signal source uses a voltage generator or a thermocouple signal simulation device. The embodiment of the present invention uses a PXI thermocouple simulator, which can output multi-channel millivolt signals at the same time.

[0078] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A thermocouple signal generating device, characterized in that: The device comprises: a human-machine interface, a logic processing unit and an output interface unit, wherein: The human-machine interface is used to receive parameter setting instructions, select the test channel type according to the parameter setting instructions, and set parameters for the corresponding test channel; The logic processing unit is used to perform nested multiplication operations according to the test channel type and the parameters corresponding to the test channel to calculate the thermocouple electromotive force of each test channel; The output interface unit is used to provide a signal source and output the thermocouple electromotive force of each test channel.

2. The thermocouple signal generating device according to claim 1, characterized in that: The logic processing unit is also used to perform deviation correction on the thermocouple electromotive force of each test channel according to the output error of each test channel type.

3. The thermocouple signal generating device according to claim 2, characterized in that: The nested multiplication formula is as follows: E={…[(a n t+a n-1 )t+a n-2 ]t+…+a1}t+a0 Where E is the thermocouple electromotive force, t is the temperature value to be simulated, and a i is the coefficient of the i-th term of the polynomial, and n is the order of the polynomial.

4. The thermocouple signal generating device according to claim 3, characterized in that: The formula for calculating the thermocouple electromotive force after deviation correction is as follows: Where u is the thermocouple electromotive force after deviation correction and δ is the offset.

5. The thermocouple signal generating device according to claim 4, characterized in that: Determine the offset based on the thermocouple type.

6. The thermocouple signal generating device according to claim 1, characterized in that: The signal source of the thermocouple electromotive force is a voltage generator or a thermocouple signal simulation device.

7. The thermocouple signal generating device according to claim 1, characterized in that: The test channel can be a single channel or multiple channels.

8. A method for generating a thermocouple signal, characterized in that: The method comprises: Receive a parameter setting instruction, select a test channel type according to the parameter setting instruction, and set parameters for the corresponding test channel; Perform nested multiplication operations according to the test channel type and the parameters corresponding to the test channel to calculate the thermocouple electromotive force of each test channel; Output the thermocouple electromotive force of each test channel.

Images