Three-wire platinum resistor temperature measurement circuit

Abstract

The embodiment of the utility model discloses a three-wire platinum resistor temperature measurement circuit, which comprises a driving circuit, a first conversion circuit and a second conversion circuit, and is characterized in that the first conversion circuit comprises a platinum resistor; the output end of the driving circuit is connected with the input end of the first conversion circuit, and the driving circuit is used for providing driving current for the first conversion circuit; the resistance value of the platinum resistor in the first conversion circuit changes according to the temperature to be measured, and the platinum resistor outputs the voltage to be measured in combination with the driving current; and the second conversion circuit is connected with the first conversion circuit and is used for converting the voltage to be measured from the analog quantity to the digital quantity. The temperature value measured by the three-wire platinum resistor temperature measurement circuit is not influenced by the resistance of a platinum resistor lead, and compensation of all measurement points in a full-scale range is realized by the characteristics of simple circuit structure, low cost and high power consumption, so that the measurement precision is improved.

Description

Technical Field

[0001] The present application relates to the technical field of electronic equipment, and in particular to a three-wire platinum resistance temperature measurement circuit. Background Art

[0002] Temperature measurement is a very important link in the fields of industrial automation and scientific research. With the continuous development of science and technology, the requirements for the accuracy and stability of temperature measurement are also constantly increasing.

[0003] At present, in temperature measurement equipment, platinum resistors are usually used as temperature sensors to form platinum resistor temperature measurement equipment because the resistance value of platinum resistors can change with temperature and have advantages such as high precision and good stability. For platinum resistor temperature measurement equipment, different measurement precision and accuracy can be obtained by using different circuit wiring methods. The following will introduce three commonly used circuit wiring methods in the prior art.

[0004] In the related art, when a two-wire connection method is used, the existence of wire resistance will affect the final measurement result, so that the measurement accuracy is greatly reduced; in order to eliminate the influence of wire resistance on the measurement result, a three-wire connection method can be used to compensate the measurement result in the measurement circuit to improve the measurement accuracy, but only a certain measurement point within the full range can be compensated, while the compensation accuracy of other measurement points is poor; in order to achieve compensation for all measurement points within the full range, a four-wire connection method can be used, but its circuit structure is more complex and costly, and it is also accompanied by disadvantages such as high power consumption. Utility Model Content

[0005] In order to solve the above technical problem or at least partially solve the above technical problem, the present application provides a three-wire platinum resistance temperature measurement circuit.

[0006] In a first aspect, the present application provides a three-wire platinum resistance temperature measurement circuit, the circuit comprising: a drive circuit, a first conversion circuit and a second conversion circuit, the first conversion circuit comprising a platinum resistor;

[0007] The output end of the driving circuit is connected to the input end of the first conversion circuit, and is used to provide a driving current to the first conversion circuit;

[0008] The platinum resistor in the first conversion circuit changes resistance according to the temperature to be measured, and outputs a voltage to be measured in combination with the driving current;

[0009] The second conversion circuit is connected to the first conversion circuit and is used to convert the voltage to be measured from an analog quantity to a digital quantity.

[0010] Compared with the prior art, the technical solution provided by this application has the following advantages:

[0011] In the three-wire platinum resistance temperature measurement circuit provided by the present application, a driving current is first provided to the first conversion circuit through a driving circuit, and then the resistance of the platinum resistance of the first conversion circuit changes according to the temperature to be measured, so as to output the voltage to be measured in combination with the driving current, and finally the voltage to be measured is converted from an analog quantity to a digital quantity through a second conversion circuit. Therefore, the temperature value measured by the three-wire platinum resistance temperature measurement circuit of the present scheme is not affected by the resistance of the platinum resistance wire, and with the characteristics of simple circuit structure, low cost and high power consumption, all measurement points in the full range are compensated, thereby improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0014] Figure 1 A schematic diagram of the structure of a three-wire platinum resistance temperature measurement circuit provided in an embodiment of the present application;

[0015] Figure 2 A schematic diagram of a three-wire platinum resistance temperature measurement circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0016] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the scheme of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0017] In the following description, many specific details are set forth to facilitate a full understanding of the present application, but the present application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only part of the embodiments of the present application, rather than all of the embodiments.

[0018] Before introducing the three-wire platinum resistance temperature measurement circuit proposed in this scheme, the problems existing in the current platinum resistance temperature measurement circuit and the solutions of the prior art are first introduced, so that it is easier to understand this scheme later.

[0019] At present, platinum resistance temperature measurement circuits usually use different circuit wiring methods to improve measurement precision and accuracy. When using the two-wire connection method, the existence of wire resistance will affect the final measurement results, which greatly reduces the measurement accuracy; in order to eliminate the influence of wire resistance on the measurement results, the three-wire connection method can be used to compensate the measurement results in the measurement circuit to improve the measurement accuracy, but only a certain measurement point within the full range can be compensated, while the compensation accuracy of other measurement points is poor; in order to achieve compensation for all measurement points within the full range, the three-wire connection method can be used, but its circuit structure is more complex and costly, and it is also accompanied by disadvantages such as high power consumption.

[0020] In order to solve the problems in the prior art that the platinum resistance temperature measurement circuit can only compensate for a certain measurement point within the full range, and has low measurement accuracy, complex circuit structure, high cost, and high power consumption, this solution provides a three-wire platinum resistance temperature measurement circuit that can effectively solve the problems in the prior art. The following article first introduces the three-wire platinum resistance temperature measurement circuit provided by this solution.

[0021] For example, Figure 1 The following is a schematic diagram of a three-wire platinum resistance temperature measurement circuit structure provided in the embodiment of the present application. Figure 1 As shown, the embodiment of the present application provides a three-wire platinum resistance temperature measurement circuit structure including a drive circuit 101, a first conversion circuit 102 and a second conversion circuit 103.

[0022] The output end of the driving circuit 101 is connected to the input end of the first conversion circuit 102 for providing a driving current to the first conversion circuit 102 .

[0023] The first conversion circuit 102 includes a platinum resistor. The platinum resistor in the first conversion circuit 102 changes resistance according to the temperature to be measured, so as to output a voltage to be measured in combination with a driving current.

[0024] The second conversion circuit 103 is connected to the first conversion circuit 102 and is used to convert the voltage to be measured from an analog quantity to a digital quantity.

[0025] Specifically, the platinum resistor at least includes a first pin, a second pin and a third pin. The first pin and the second pin of the platinum resistor are connected to the first conversion circuit 102 respectively, and the third pin of the platinum resistor is connected to the second conversion circuit 103 .

[0026] A three-wire platinum resistance temperature measurement circuit provided in an embodiment of the present application first provides a driving current to a first conversion circuit through a driving circuit, and then the platinum resistor of the first conversion circuit changes its resistance according to the temperature to be measured, so as to output a voltage to be measured in combination with the driving current, and finally the voltage to be measured is converted from an analog quantity to a digital quantity through a second conversion circuit, and then according to the characteristics of the platinum resistor, the measured temperature value can be determined by the converted voltage to be measured.

[0027] Therefore, the temperature value measured by the three-wire platinum resistance temperature measurement circuit of this scheme is not affected by the resistance of the platinum resistance wire, and with the characteristics of simple circuit structure, low cost and high power consumption, it can compensate for all measurement points in the full range, thereby improving the measurement accuracy.

[0028] The following will introduce the specific circuit structure of a three-wire platinum resistance temperature measurement circuit provided by this solution, which specifically includes a drive circuit, a first conversion circuit and a second conversion circuit.

[0029] For example, Figure 2 A schematic diagram of a three-wire platinum resistance temperature measurement circuit provided in an embodiment of the present application. Figure 2 As shown, the embodiment of the present application provides a three-wire platinum resistance temperature measurement circuit including a constant current source 201, a platinum resistor 202, an analog-to-digital converter 203, a first operational amplifier A1, a second operational amplifier A2, a first resistor R1, a second resistor R2 and a third resistor R3.

[0030] Specifically, the driving circuit includes a constant current source 201, a first operational amplifier A1 and a first resistor R1; the platinum resistor 202 includes at least a first pin and a second pin; one end of the first resistor R1 is connected to the constant current source 201, and the other end is connected to the positive input terminal of the first operational amplifier A1 and connected to the first pin of the platinum resistor 202; the negative input terminal of the first operational amplifier A1 is grounded, and the output terminal of the first operational amplifier A1 is connected to the second pin of the platinum resistor 202; the driving current passes through the first pin of the platinum resistor 202 and all flows out from the second pin.

[0031] Therefore, the driving circuit can provide a driving current to the first conversion circuit.

[0032] In some embodiments, when the output current of the constant current source is too large, the self-heating effect of the platinum resistance sensor will become very obvious, thereby reducing the measurement accuracy; at the same time, if the output current of the constant current source is too small, the sensitivity of the platinum resistance sensor cannot be guaranteed, which may lead to the inability to accurately measure the required physical quantity. Therefore, the constant current source can adopt a 1mA constant current source circuit designed based on the constant current source chip of LM334MX / NOPB, so the output current of the constant current source is 1mA. In practical applications, the output current value of the constant current source can be adjusted accordingly according to the specific situation. This solution does not limit the output current value of the constant current source.

[0033] The first conversion circuit also includes a second resistor R2, a third resistor R3, and a second operational amplifier A2; the platinum resistor 202 also includes a third pin;

[0034] The third pin of the platinum resistor 202 is connected to the positive input terminal of the second operational amplifier A2; one end of the second resistor R2 is connected to the second pin of the platinum resistor 202, and the other end is connected to the negative input terminal of the second operational amplifier A2; one end of the third resistor R3 is connected to the negative input terminal of the second operational amplifier A2, and the other end is connected to the output terminal of the second operational amplifier A2, and serves as the output terminal of the first conversion circuit.

[0035] Therefore, the platinum resistor in the first conversion circuit changes its resistance according to the temperature to be measured, so as to output the voltage to be measured in combination with the driving current.

[0036] In some embodiments, in order to accurately capture the measurement data, the resistance values ​​of the second resistor R2 and the third resistor R3 in the first conversion circuit need to be limited. Because when the temperature changes and the resistance value of the platinum resistor changes, the resistance values ​​of the second resistor R2 and the third resistor R3 are equal, and the voltage output to the analog-to-digital converter changes linearly, the resistance value of the second resistor R2 is equal to the resistance value of the third resistor R3.

[0037] In some embodiments, in order to accurately capture the measurement data, when the temperature changes and the resistance of the platinum resistor changes, not only the resistance of the second resistor R2 and the third resistor R3 must be equal, and the voltage output to the analog-to-digital converter changes linearly, but also the accuracy and sensitivity of the analog-to-digital converter must be taken into account, so the resistance value of the second resistor R2 is 1kΩ; the resistance value of the third resistor R3 is 1kΩ. In practical applications, the resistance values ​​of the second resistor R2 and the third resistor R3 can be adjusted accordingly according to specific circumstances. This solution does not limit the resistance values ​​of the second resistor R2 and the third resistor R3.

[0038] In some embodiments, in order to adjust the resistance values ​​of the first resistor R1 , the second resistor R2 , and the third resistor R3 according to specific circumstances, the first resistor R1 , the second resistor R2 , and the third resistor R3 may be configured as resistors with continuously adjustable resistance values.

[0039] In some embodiments, in order to make the second operational amplifier A2 in the first conversion circuit output a stable driving current, a current source VCC of positive and negative 5V may be applied to the second operational amplifier A2. In practical applications, the voltage of the current source VCC may be adjusted accordingly according to specific circumstances, and this solution does not limit the voltage of the current source VCC.

[0040] The second conversion circuit includes an analog-to-digital converter 203; the input end of the analog-to-digital converter 203 is used as the input end of the second conversion circuit, and the output end of the analog-to-digital converter 203 is used as the output end of the second conversion circuit. The first end of the analog-to-digital converter 203 is connected to the output end of the second operational amplifier A2, and the second end of the analog-to-digital converter 203 is grounded.

[0041] The second conversion circuit is connected to the first conversion circuit, and can collect the voltage to be measured at the current temperature and convert the voltage to be measured from an analog quantity to a digital quantity.

[0042] The following will introduce the temperature measurement principle of a three-wire platinum resistance temperature measurement circuit provided by this scheme.

[0043] The calculation formula of the temperature to be measured T is: T = (R pt -R0) / △R;

[0044] Among them, R pt represents the measured resistance of the platinum resistor, R0 represents the reference resistance of the platinum resistor at 0°C, and △R represents the resistance change of the platinum resistor in response to a 1°C increase in the measured temperature.

[0045] In some embodiments, the type of platinum resistor can be a Pt100 type platinum resistor, because the resistance of the Pt100 platinum resistor is 100Ω at 0°C. In the range of 0 to 200°C, the resistance of the Pt100 increases by 0.385Ω for every 1°C increase in temperature. Therefore, the calculation formula for the measured temperature T is: T = (R pt -100) / 0.385. In practical applications, other types of platinum resistors can also be used according to different requirements. This solution does not specifically limit the type of platinum resistor.

[0046] Therefore, in order to obtain the measured temperature T, it is necessary to calculate the measured resistance value R of the platinum resistor at the current temperature. pt Platinum resistance measurement resistance R pt It can be calculated by formula (1), formula (2), formula (3) and formula (4):

[0047] V0 = -I1 (R w + R pt ) Formula (1)

[0048] V1 = -I1(2R w + R pt ) Formula (2)

[0049] I2=(V0-V1) / R2=I1R w / R2 formula (3)

[0050] V=V0+I2R2=-I1R pt Formula (4)

[0051] Where V0 represents the output voltage of the first operational amplifier, I1 represents the output current of the constant current source, and R wrepresents the resistance of the platinum resistance wire, V1 represents the negative input voltage of the second operational amplifier, R2 represents the resistance value of the second resistor, I2 represents the current value flowing through the second resistor, and V represents the output voltage of the second operational amplifier.

[0052] Specifically, according to Ohm's law, the output voltage V0 of the first operational amplifier is obtained, and the output current I1 of the constant current source is multiplied by the resistance value R of the platinum resistor. pt The resistance R of the platinum resistance wire w The specific formula is shown in formula (1): V0 = -I1(R w +R pt ).

[0053] According to Ohm's law, the negative input voltage V1 of the second operational amplifier is obtained, and the output current I1 of the constant current source is multiplied by the resistance value R of the platinum resistor. pt The resistance R of the platinum resistance wire is twice w The specific formula is shown in formula (2): V1 = -I1(2R w +R pt ).

[0054] According to Ohm's law, the current value flowing through the second resistor is I2, which is obtained by dividing the difference between the output voltage V0 of the first operational amplifier and the negative input voltage V1 of the second operational amplifier by the resistance value R2 of the second resistor.

[0055] The specific formula is shown in formula (3): I2 = (V0-V1) / R2 = I1R w / R2.

[0056] According to the voltage-dividing characteristics of the operational amplifier, the output voltage V of the second operational amplifier and the resistance value R of the platinum resistor are finally obtained. pt The output voltage V of the second operational amplifier is equal to the output voltage V0 of the first operational amplifier plus the product of the current value I2 flowing through the second resistor and the resistance value R2 of the second resistor. The specific formula is shown in formula (4): V = V0 + I2R2 = -I1R pt .

[0057] The voltage V at the output of the second operational amplifier collected by the analog-to-digital conversion circuit can be calculated using formula (4) to obtain the current resistance value R of the platinum resistor. pt , and calculate the current temperature based on the characteristic that the resistance of the platinum resistor changes with temperature.

[0058] Therefore, in the three-wire platinum resistance temperature measurement circuit provided in the embodiment of the present application, the platinum resistance value R ptThe change is only related to the output voltage V of the second operational amplifier and the output current I1 of the constant current source, but has nothing to do with the resistance of the connected platinum resistor wire, so that the change of the platinum resistor resistance is converted into a linear voltage value change, so that all measurement points in the full range can be compensated, the measurement accuracy is improved, and the circuit structure is simple, the cost is low and the power consumption is high.

[0059] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0060] The above is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features applied for herein.

Claims

1. A three-wire platinum resistance temperature measurement circuit, characterized in that: include: A driving circuit, a first conversion circuit and a second conversion circuit, wherein the first conversion circuit includes a platinum resistor; The output end of the driving circuit is connected to the input end of the first conversion circuit, and is used to provide a driving current to the first conversion circuit; The platinum resistor in the first conversion circuit changes resistance according to the temperature to be measured, and outputs a voltage to be measured in combination with the driving current; The second conversion circuit is connected to the first conversion circuit and is used to convert the voltage to be measured from an analog quantity to a digital quantity; The driving circuit includes a constant current source, a first operational amplifier and a first resistor; the platinum resistor includes at least a first pin and a second pin; One end of the first resistor is connected to the constant current source, and the other end is connected to the positive input end of the first operational amplifier and connected to the first pin of the platinum resistor; the negative input end of the first operational amplifier is grounded, and the output end of the first operational amplifier is connected to the second pin of the platinum resistor; The driving current passes through the first pin of the platinum resistor and all flows out from the second pin.

2. The three-wire platinum resistance temperature measurement circuit according to claim 1, characterized in that: The output current of the constant current source is 1 mA.

3. The three-wire platinum resistance temperature measurement circuit according to claim 1, characterized in that: The first conversion circuit further includes a second resistor, a third resistor and a second operational amplifier; the platinum resistor further includes a third pin; The third pin of the platinum resistor is connected to the positive input terminal of the second operational amplifier; one end of the second resistor is connected to the second pin of the platinum resistor, and the other end is connected to the negative input terminal of the second operational amplifier; one end of the third resistor is connected to the negative input terminal of the second operational amplifier, and the other end is connected to the output terminal of the second operational amplifier, and serves as the output terminal of the first conversion circuit.

4. The three-wire platinum resistance temperature measurement circuit according to claim 3 is characterized in that: The resistance value of the second resistor is equal to the resistance value of the third resistor.

5. The three-wire platinum resistance temperature measurement circuit according to claim 3, characterized in that: The resistance value of the second resistor is 1 kΩ; the resistance value of the third resistor is 1 kΩ.

6. The three-wire platinum resistance temperature measurement circuit according to claim 3, characterized in that: The first resistor, the second resistor and the third resistor are resistors with continuously adjustable resistance values.

7. The three-wire platinum resistance temperature measurement circuit according to claim 3, characterized in that: The second conversion circuit includes an analog-to-digital converter; The input end of the analog-to-digital converter serves as the input end of the second conversion circuit, and the output end of the analog-to-digital converter serves as the output end of the second conversion circuit.

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