CN211717657U - Calibration-free thermocouple cold end temperature measurement circuit - Google Patents
Calibration-free thermocouple cold end temperature measurement circuit Download PDFInfo
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- CN211717657U CN211717657U CN202020597971.XU CN202020597971U CN211717657U CN 211717657 U CN211717657 U CN 211717657U CN 202020597971 U CN202020597971 U CN 202020597971U CN 211717657 U CN211717657 U CN 211717657U
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- end temperature
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Abstract
The utility model relates to a thermocouple temperature measurement technical field especially relates to an exempt from calibration thermocouple cold junction temperature measurement circuit, including thermocouple cold junction temperature sensor RT1, stabiliser U1, reference resistance R2 and analog to digital converter U2, stabiliser U1 and reference resistance R2 produce the excitation source as thermocouple cold junction temperature sensor RT 1's excitation source, and analog to digital converter U2 is used for gathering the voltage difference at thermocouple cold junction temperature sensor RT1 both ends, and analog to digital converter U2's the anodal reference end that links to each other with stabiliser U1 of reference input. The utility model discloses need not plus standard resistance to calibrate the circuit alright calculate thermocouple cold junction temperature sensor RT 1's resistance value, possess higher measuring accuracy, the cost is reduced has improved production efficiency simultaneously.
Description
Technical Field
The utility model relates to a thermocouple temperature measurement technical field especially relates to an exempt from calibration thermocouple cold junction temperature measurement circuit.
Background
The thermocouple sensor is used for measuring the temperature by connecting two conductors made of different materials together to generate thermoelectric voltage. The thermocouple is provided with a hot end and a cold end, according to the basic principle of thermocouple temperature measurement, as long as the temperature of the cold end is kept unchanged, the thermoelectric potential output by the thermocouple is a single-value function of the temperature measured by the hot 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 in a grading way. 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.
The existing measuring circuit usually needs to be calibrated by additionally adding a standard resistance signal to ensure the measuring accuracy due to the non-ideal consistency of devices or the reason of circuit design, and has great workload for the batch manufacturing of thermocouple temperature measurement products, thereby increasing the error probability while influencing the production efficiency.
SUMMERY OF THE UTILITY MODEL
The utility model provides an exempt from calibration thermocouple cold junction temperature measurement circuit for thermocouple cold junction temperature measurement circuit need not the calibration and can obtain higher measuring accuracy.
In order to realize the utility model discloses an aim, the technical scheme who adopts is: a calibration-free thermocouple cold-end temperature measuring circuit comprises a thermocouple cold-end temperature sensor RT1, a voltage stabilizer U1, a reference resistor R2 and an analog-to-digital converter U2, wherein an excitation source is generated by the voltage stabilizer U1 and the reference resistor R2 and serves as an excitation source of the thermocouple cold-end temperature sensor RT1, the analog-to-digital converter U2 is used for acquiring voltage difference between two ends of the thermocouple cold-end temperature sensor RT1, and the anode of a reference input end of the analog-to-digital converter U2 is connected with a reference end of the voltage stabilizer U1.
As the optimization scheme of the utility model, thermocouple cold junction temperature sensor RT1 is Pt100 thermal resistance or Pt1000 thermal resistance.
As the utility model discloses an optimization scheme, thermocouple cold junction temperature sensor RT1 arranges by the thermocouple wiring end.
As the optimization scheme of the utility model, the precision of reference resistance R2 is 0.1% -0.5%.
The utility model discloses has positive effect: the utility model discloses need not plus standard resistance to calibrate the circuit alright calculate thermocouple cold junction temperature sensor RT 1's resistance value, possess higher measuring accuracy, the cost is reduced has improved production efficiency simultaneously.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a schematic diagram of the circuit connection of the present invention.
Detailed Description
As shown in fig. 1, the utility model discloses an exempt from calibration thermocouple cold junction temperature measurement circuit, including thermocouple cold junction temperature sensor RT1, stabiliser U1, reference resistance R2 and analog to digital converter U2, stabiliser U1 and reference resistance R2 produce the excitation source as thermocouple cold junction temperature sensor RT 1's excitation source, and analog to digital converter U2 is used for gathering the voltage difference at thermocouple cold junction temperature sensor RT1 both ends, and analog to digital converter U2's the anodal reference terminal with stabiliser U1 links to each other. The proportional value P between the resistance value of the thermocouple cold-end temperature sensor RT1 and the reference resistor R2 can be obtained through a calibration-free thermocouple cold-end temperature measuring circuit, and the proportional value P is RT 1/R2. The resistance value of the thermocouple cold end temperature sensor RT1 can be calculated by using the proportional value P and the resistance value of the reference resistor R2. The precision of the reference resistor R2 is 0.1% -0.5%, and the accuracy of the measurement result is guaranteed.
Thermocouple cold end temperature sensor RT1 is a Pt100 thermal resistor or a Pt1000 thermal resistor. The thermocouple cold end temperature sensor RT1 is arranged beside the thermocouple terminal, so that the measured cold end temperature is consistent with the actual cold end temperature, and the accuracy of thermocouple temperature measurement is ensured.
The calibration-free thermocouple cold end temperature measurement circuit is usually connected with an operation processing unit for cold end temperature measurement, the operation processing unit is configured with the conversion rate of an analog-to-digital converter U2, voltages V1-V2 at two ends of a thermocouple cold end temperature sensor RT1 are collected at regular time, a corresponding AD value AD _ Val is obtained, V2 is a reference voltage of the analog-to-digital converter U2, and the formula is as follows:
P-V (V1-V2)/V2-AD _ Val/65535 formula 1
Wherein: p is the proportional value between the resistance value of the thermocouple cold end temperature sensor RT1 and the reference resistor R2, and 65535 is the AD value corresponding to the full scale of the analog-to-digital converter U2.
Voltage regulator U1 may alternatively be AZ432 or a similar device, I thereofrefNegligible, the medium current flowing through reference resistor R2 is equal to the current in thermocouple cold end temperature sensor RT1, and the following can be derived in conjunction with equation 1:
RT 1-R2 × P-R2 × AD _ Val/65535 formula 2
The known value R2 is used for obtaining a fixed proportional relation between RT1 and the AD _ Val value, the method can calculate the resistance value of the thermocouple cold end temperature sensor RT1 without calibrating a circuit, and software table look-up operation is carried out in an operation processing unit by using the resistance value to obtain a corresponding temperature value.
In practical use, the temperature of the industrial site environment where the thermocouple temperature measurement product is located is generally within the range of-40 to +85 ℃, the temperature of the cold end is measured by taking PT100 as an example, and the corresponding theoretical resistance value of the PT100 at 85 ℃ is 132.8 omega. When the reference resistor R2 is a resistor with the precision of 0.1%, the maximum deviation of the actual PT100 measurement value caused by the resistance deviation of R2 is as follows: when 132.8 Ω × 0.1% ═ 0.1328 Ω, the corresponding deviation of the temperature point is: 0.1328 omega/(0.38 omega/° C) is approximately equal to 0.35 ℃, wherein 0.38 omega/° C is the resistance value of the thermocouple cold end temperature sensor RT1 per degree centigrade change, the error is the maximum error of the circuit design, and the value of the error is far less than the +/-1 ℃ cold end compensation error usually required by thermocouple temperature measurement products.
The above-mentioned embodiments, further detailed description of the objects, technical solutions and advantages of the present invention, it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (4)
1. The utility model provides a exempt from to calibrate thermocouple cold junction temperature measurement circuit which characterized in that: the cold-end temperature sensor comprises a thermocouple cold-end temperature sensor RT1, a voltage stabilizer U1, a reference resistor R2 and an analog-to-digital converter U2, wherein an excitation source generated by the voltage stabilizer U1 and the reference resistor R2 is used as an excitation source of the thermocouple cold-end temperature sensor RT1, the analog-to-digital converter U2 is used for collecting voltage differences at two ends of the thermocouple cold-end temperature sensor RT1, and the anode of a reference input end of the analog-to-digital converter U2 is connected with the reference end of the voltage stabilizer U1.
2. The calibration-free thermocouple cold end temperature measurement circuit of claim 1, wherein: thermocouple cold end temperature sensor RT1 is a Pt100 thermal resistor or a Pt1000 thermal resistor.
3. A calibration-free thermocouple cold end temperature measurement circuit according to claim 1 or 2, wherein: a thermocouple cold end temperature sensor RT1 is disposed adjacent the thermocouple terminal.
4. The calibration-free thermocouple cold end temperature measurement circuit of claim 3, wherein: the accuracy of the reference resistor R2 is 0.1% -0.5%.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202020597971.XU CN211717657U (en) | 2020-04-21 | 2020-04-21 | Calibration-free thermocouple cold end temperature measurement circuit |
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| CN202020597971.XU CN211717657U (en) | 2020-04-21 | 2020-04-21 | Calibration-free thermocouple cold end temperature measurement circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115452179A (en) * | 2022-11-07 | 2022-12-09 | 四川天利科技有限责任公司 | Multi-channel real-time self-calibration thermocouple cold end temperature measurement method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115452179A (en) * | 2022-11-07 | 2022-12-09 | 四川天利科技有限责任公司 | Multi-channel real-time self-calibration thermocouple cold end temperature measurement method |
| CN115452179B (en) * | 2022-11-07 | 2023-02-14 | 四川天利科技有限责任公司 | Multi-channel real-time self-calibration thermocouple cold end temperature measurement method |
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Effective date of registration: 20211008 Address after: 211100 No. 19, Jinxin Middle Road, Jiangning District, Nanjing, Jiangsu Province (Jiangning Development Zone) Patentee after: Nanjing youbei Electric Technology Co.,Ltd. Address before: 211112 puliu Road, Liuhe Economic Development Zone, Nanjing, Jiangsu Patentee before: NANJING NEW POWER ELECTRIC Co.,Ltd. |