CN220170383U - High-precision sampling processing circuit of three-wire system thermal resistor - Google Patents
High-precision sampling processing circuit of three-wire system thermal resistor Download PDFInfo
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- CN220170383U CN220170383U CN202321534892.4U CN202321534892U CN220170383U CN 220170383 U CN220170383 U CN 220170383U CN 202321534892 U CN202321534892 U CN 202321534892U CN 220170383 U CN220170383 U CN 220170383U
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- 238000005070 sampling Methods 0.000 title claims abstract description 61
- 238000006243 chemical reaction Methods 0.000 claims abstract description 80
- 238000010438 heat treatment Methods 0.000 claims abstract description 21
- 239000003990 capacitor Substances 0.000 claims description 9
- 238000000034 method Methods 0.000 claims 1
- 239000002699 waste material Substances 0.000 abstract description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
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Abstract
The utility model relates to a high-precision sampling processing circuit of a three-wire heating resistor, which comprises a reference circuit, a sampling circuit, a first analog-to-digital conversion chip, a second analog-to-digital conversion chip and an MCU (micro control unit) singlechip, wherein the reference circuit is respectively connected with the first analog-to-digital conversion chip and the second analog-to-digital conversion chip, the sampling circuit is respectively connected with the first analog-to-digital conversion chip and the second analog-to-digital conversion chip, and the reference circuit is also connected with the sampling circuit, and the first analog-to-digital conversion chip and the second analog-to-digital conversion chip are respectively connected with the MCU singlechip; the reference circuit comprises a power reference chip U3, and the reference voltage output by the power reference chip U3 provides reference for the two analog conversion chips U1 and U2 and provides an accurate voltage source for the sampling circuit for thermal resistance sampling. The utility model realizes full-range high precision, realizes the compatibility of a three-wire system and a two-wire system of the thermal resistor, and avoids the resource waste.
Description
Technical Field
The utility model relates to the technical field of temperature measurement and acquisition, in particular to a high-precision sampling processing circuit of a three-wire heating resistor.
Background
The temperature is one of the most used physical quantities in industrial occasions, and the thermal resistor is a commonly used temperature sensor, and is characterized in that: high accuracy, good linearity and stable performance. Dividing according to the wiring mode, the thermal resistor has the following three types: two-wire heating resistor, three-wire heating resistor and four-wire heating resistor. Because the measurement accuracy of the two-wire system thermal resistor is greatly influenced by the wire resistance, the three-wire system thermal resistor or the four-wire system thermal resistor is often adopted in practical application. The three-wire heating resistor has lower cost and more convenient wiring, and is the most common mode at present.
The sampling processing circuit of the three-wire heating resistor in the prior art has the following defects:
(1) Most sampling processing circuits of three-wire heating resistors adopt built-in ADC (analog to digital converter) acquisition processing of a main control chip MCU (micro control unit), the built-in ADC sampling processing is not very high in linear precision in the whole range, for example, for the heating resistor Pt100, the scheme cannot achieve consistency precision in the whole temperature range.
(2) The sampling processing circuit of part of three-wire system thermal resistors adopts external ADC to sample, the ADC is mostly of high-precision double-channel type, and for the type of compatible thermal resistor two-wire system sampling, one path of ADC can only be idle processing, which is waste of resources.
Disclosure of Invention
The utility model aims to overcome the defects, and provides a high-precision sampling processing circuit for a three-wire system thermal resistor, which realizes full-range high precision, realizes compatibility of the three-wire system and the two-wire system of the thermal resistor, and avoids resource waste.
The purpose of the utility model is realized in the following way:
the high-precision sampling processing circuit of the three-wire heating resistor comprises a reference circuit, a sampling circuit, a first analog-to-digital conversion chip, a second analog-to-digital conversion chip and an MCU (micro control unit) singlechip, wherein the reference circuit is respectively connected with the first analog-to-digital conversion chip and the second analog-to-digital conversion chip, the sampling circuit is respectively connected with the first analog-to-digital conversion chip and the second analog-to-digital conversion chip, the reference circuit is also connected with the sampling circuit, and the first analog-to-digital conversion chip and the second analog-to-digital conversion chip are respectively connected with the MCU singlechip; the reference circuit comprises a power supply reference chip U3, wherein reference voltage output by the power supply reference chip U3 provides reference for two analog conversion chips U1 and U2, and provides an accurate voltage source for the sampling circuit for thermal resistance sampling;
the sampling circuit comprises a resistor R3, a resistor R5 and a resistor R7 which are connected in parallel, and a loop is formed by the resistor R2, the thermal resistor TR and the resistor R8; the line resistor with the line length of the thermal resistor TR is a line resistor R, and the thermal resistor TR is respectively connected with a resistor R3, a resistor R5 and a resistor R7; the junction between the thermal resistor TR and the resistor R3 is Vth1, the junction between the thermal resistor R5 and the resistor R7 is Vth2, and the junctions between the thermal resistor TR and the resistor R7 are Vth3, wherein Vth1, vth2 and Vth3 represent voltages of three junctions of the thermal resistor and the sampling circuit to the ground; the first analog-to-digital conversion chip is an analog-to-digital conversion chip U1, and the junction voltages Vth1 and Vth2 are connected to the analog-to-digital conversion chip U1 after being filtered by a dielectric RC; the second analog-to-digital conversion chip is an analog-to-digital conversion chip U2, and the junction voltages Vth2 and Vth3 are connected to the analog-to-digital conversion chip U2 after being filtered by a dielectric RC.
Further, a capacitor C4 is connected between the resistor R3 and the resistor R5, a capacitor C7 is connected between the resistor R5 and the resistor R7, and the resistor R7 is connected with a capacitor C9.
Further, the analog-to-digital conversion chip U1 is a 32-bit analog-to-digital conversion chip for high-precision sampling of the thermal resistor, and the analog-to-digital conversion chip U1 belongs to a differential input type, so that the result obtained after the processing of the analog-to-digital conversion chip U1 is the voltage of the thermal resistor TR and the line resistor r of one thermal resistor, that is, Δu1=vth1-Vth 2.
Further, the analog-to-digital conversion chip U2 is a 24-bit analog-to-digital conversion chip for measuring the line resistance of the thermal resistor, and the analog-to-digital conversion chip U2 belongs to a differential input type, and the voltage of the line resistance r of the thermal resistor TR, that is, Δu2=vth2-Vth 3 is obtained after the processing of the analog-to-digital conversion chip U2.
Further, the voltage Δu1=vth1-Vth 2 of the thermal resistor TR and the line resistor r of one thermal resistor, the voltage Δu2=vth2-Vth 3 of the line resistor r of one thermal resistor TR, and the voltage=Δu1- Δu2 of the thermal resistor TR.
Further, the analog conversion chip U1 is connected to the inductor L1 and the inductor L2, respectively, so as to isolate the power supply from the ground.
Compared with the prior art, the utility model has the beneficial effects that:
(1) The utility model provides a high-precision sampling processing circuit of a three-wire thermal resistor, which realizes full-range high precision, such as a temperature range of-200 ℃ to 850 ℃ of a thermal resistor Pt100 full-range, and can realize conversion precision of 0.2 ℃ in the full range.
(2) The utility model provides a high-precision sampling processing circuit for a three-wire system thermal resistor, which can realize the compatibility of the three-wire system and the two-wire system of the thermal resistor by using two analog-to-digital conversion chips, and can select and paste one of the analog-to-digital conversion chips for use, thereby avoiding the waste of resources.
Drawings
Fig. 1 is a schematic circuit diagram of the present utility model.
Fig. 2 is a block diagram of the circuitry of the present utility model.
Wherein:
a reference circuit 1, a sampling circuit 2, a first analog-to-digital conversion chip 3 and a second analog-to-digital conversion chip 4.
Description of the embodiments
In order to better understand the technical solution of the present utility model, the following detailed description will be made with reference to the accompanying drawings. It should be understood that the following embodiments are not intended to limit the embodiments of the present utility model, but are merely examples of embodiments that may be employed by the present utility model. It should be noted that, the description herein of the positional relationship of the components, such as the component a being located above the component B, is based on the description of the relative positions of the components in the drawings, and is not intended to limit the actual positional relationship of the components.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
In the above description of the present utility model, it should be noted that the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and are not to be construed as indicating or implying relative importance.
Example 1
Referring to fig. 1-2, fig. 1 depicts a schematic circuit diagram of a high precision sampling processing circuit for a three-wire heating resistor. As shown in the figure, the high-precision sampling processing circuit of the three-wire heating resistor comprises a reference circuit 1, a sampling circuit 2, a first analog-to-digital conversion chip 3, a second analog-to-digital conversion chip 4 and an MCU singlechip, wherein the reference circuit 1 is respectively connected with the first analog-to-digital conversion chip 3 and the second analog-to-digital conversion chip 4, the sampling circuit 2 is respectively connected with the first analog-to-digital conversion chip 3 and the second analog-to-digital conversion chip 4, the reference circuit 1 is also connected with the sampling circuit 2, and the first analog-to-digital conversion chip 3 and the second analog-to-digital conversion chip 4 are respectively connected with the MCU singlechip.
The reference circuit 1 comprises a power supply reference chip U3, and a reference voltage Vref output by the power supply reference chip U3 provides reference for the two analog conversion chips U1 and U2 and provides an accurate voltage source for the sampling circuit for thermal resistance sampling.
The sampling circuit 2 comprises a resistor R3, a resistor R5 and a resistor R7 which are connected in parallel, and a loop is formed by the resistor R2, the thermal resistor TR and the resistor R8; the length of the thermal resistor TR is actually provided with a certain line resistance, which is expressed as a line resistance r, and the thermal resistor TR can remove the influence of the line resistance r on the conversion precision in a three-line sampling mode; the sampling mode is that the resistor is divided by resistors, the thermal resistor TR is respectively connected with a resistor R3, a resistor R5 and a resistor R7, a capacitor C4 is connected between the resistor R3 and the resistor R5, a capacitor C7 is connected between the resistor R5 and the resistor R7, and the resistor R7 is connected with a capacitor C9;
the junction between the thermal resistor TR and the resistor R3 is Vth1, the junction between the thermal resistor R5 and the resistor R7 is Vth2, and the junctions between the thermal resistor TR and the resistor R7 are Vth3, where Vth1, vth2 and Vth3 represent voltages of the three junctions of the thermal resistor and the sampling circuit to ground.
The first adc 3 is an adc U1, the junction voltages Vth1 and Vth2 are filtered by a dielectric RC and then connected to the adc U1, the adc U1 is a 32-bit adc for high-precision sampling of the thermal resistor, and the adc U1 is of a differential input type, so that the result obtained after the processing of the adc U1 is the voltages of the thermal resistor TR and the line resistor r of a thermal resistor, i.e. Δu1=vth1-Vth 2;
the second adc chip 4 is an adc chip U2, the junction voltages Vth2 and Vth3 are filtered by a dielectric RC and then connected to the adc chip U2, the adc chip U2 is a 24-bit adc chip for measuring the line resistance of the thermal resistor, and the adc chip U2 is of a differential input type, and the voltage of the line resistance r of the thermal resistor TR is obtained after the processing of the adc chip U2, that is, Δu2=vth2-Vth 3;
the two analog conversion chips U1 and U2 transmit the sampling result to the MCU for processing, and the voltage=DeltaU1-DeltaU2 of the thermal resistor TR can be obtained.
The analog conversion chip U1 is respectively connected with the inductor L1 and the inductor L2 to isolate a power supply from the ground; because the analog conversion chip needs to perform isolation processing on analog and digital, it is very necessary to ensure the cleanliness of the analog circuit ground, which is essential for realizing high precision.
Working principle:
the utility model relates to a high-precision sampling processing circuit for a three-wire heating resistor, which is mainly based on two analog-to-digital conversion chips for respectively sampling the heating resistor and the wire resistor of the heating resistor. The circuit comprises a thermal resistance sampling circuit, an analog-to-digital conversion chip processing circuit and a reference circuit. The reference circuit generates Vref which is mainly used for providing reliable reference for two analog-digital conversion chips and simultaneously providing stable sampling voltage source for the sampling circuit; the first analog-to-digital conversion chip U1 is mainly used for collecting and processing thermal resistors and the wire resistors of the thermal resistors; the second analog-to-digital conversion chip U2 is mainly used for collecting and processing the line resistance of the thermal resistor; the sampling circuit is mainly used for sampling thermal resistors and the thermal resistors in a resistor voltage division mode.
The foregoing is merely a specific application example of the present utility model, and the protection scope of the present utility model is not limited in any way. All technical schemes formed by equivalent transformation or equivalent substitution fall within the protection scope of the utility model.
Claims (6)
1. A high-precision sampling processing circuit of a three-wire heating resistor is characterized in that: the device comprises a reference circuit (1), a sampling circuit (2), a first analog-to-digital conversion chip (3), a second analog-to-digital conversion chip (4) and an MCU (micro control unit) singlechip, wherein the reference circuit (1) is respectively connected with the first analog-to-digital conversion chip (3) and the second analog-to-digital conversion chip (4), the sampling circuit (2) is respectively connected with the first analog-to-digital conversion chip (3) and the second analog-to-digital conversion chip (4), the reference circuit (1) is also connected with the sampling circuit (2), and the first analog-to-digital conversion chip (3) and the second analog-to-digital conversion chip (4) are respectively connected with the MCU singlechip; the reference circuit (1) comprises a power supply reference chip U3, wherein reference voltage output by the power supply reference chip U3 provides reference for two analog conversion chips U1 and U2, and provides an accurate voltage source for the sampling circuit for thermal resistance sampling;
the sampling circuit (2) comprises a resistor R3, a resistor R5 and a resistor R7 which are connected in parallel, and a loop is formed by the resistor R2, the thermal resistor TR and the resistor R8; the line resistor with the line length of the thermal resistor TR is a line resistor R, and the thermal resistor TR is respectively connected with a resistor R3, a resistor R5 and a resistor R7; the junction between the thermal resistor TR and the resistor R3 is Vth1, the junction between the thermal resistor R5 and the resistor R7 is Vth2, and the junctions between the thermal resistor TR and the resistor R7 are Vth3, wherein Vth1, vth2 and Vth3 represent voltages of three junctions of the thermal resistor and the sampling circuit to the ground; the first analog-to-digital conversion chip (3) is an analog-to-digital conversion chip U1, and the junction voltages Vth1 and Vth2 are connected to the analog-to-digital conversion chip U1 after being filtered by a dielectric RC; the second analog-digital conversion chip (4) is an analog-digital conversion chip U2, and the junction voltages Vth2 and Vth3 are connected to the analog-digital conversion chip U2 after being filtered by a dielectric RC.
2. The high-precision sampling processing circuit of a three-wire heating resistor according to claim 1, wherein: a capacitor C4 is connected between the resistor R3 and the resistor R5, a capacitor C7 is connected between the resistor R5 and the resistor R7, and the resistor R7 is connected with a capacitor C9.
3. The high-precision sampling processing circuit of a three-wire heating resistor according to claim 1, wherein: the analog-to-digital conversion chip U1 is a 32-bit analog-to-digital conversion chip and is used for high-precision sampling processing of the thermal resistor, the analog-to-digital conversion chip U1 belongs to a differential input type, and the result obtained after the processing of the analog-to-digital conversion chip U1 is the voltage of the thermal resistor TR and the line resistor r of one thermal resistor, namely delta U1 = Vth 1-Vth 2.
4. The high-precision sampling processing circuit of a three-wire heating resistor according to claim 1, wherein: the analog-to-digital conversion chip U2 is a 24-bit analog-to-digital conversion chip and is used for measuring the line resistance of the thermal resistor, and the analog-to-digital conversion chip U2 belongs to a differential input type, so that the voltage of the line resistance r of the thermal resistor TR, namely DeltaU2=Vt2-Vt3, is obtained after the analog-to-digital conversion chip U2 processes.
5. The high-precision sampling processing circuit of a three-wire heating resistor according to claim 1, wherein: the voltage Δu1=vth1-Vth 2 of the thermal resistor TR and the line resistor r of one thermal resistor, the voltage Δu2=vth2-Vth 3 of the line resistor r of one thermal resistor TR, and the voltage=Δu1- Δu2 of the thermal resistor TR.
6. The high-precision sampling processing circuit of a three-wire heating resistor according to claim 1, wherein: the analog conversion chip U1 is respectively connected with the inductor L1 and the inductor L2 to isolate a power supply from the ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202321534892.4U CN220170383U (en) | 2023-06-16 | 2023-06-16 | High-precision sampling processing circuit of three-wire system thermal resistor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202321534892.4U CN220170383U (en) | 2023-06-16 | 2023-06-16 | High-precision sampling processing circuit of three-wire system thermal resistor |
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| CN220170383U true CN220170383U (en) | 2023-12-12 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202321534892.4U Active CN220170383U (en) | 2023-06-16 | 2023-06-16 | High-precision sampling processing circuit of three-wire system thermal resistor |
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| CN (1) | CN220170383U (en) |
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- 2023-06-16 CN CN202321534892.4U patent/CN220170383U/en active Active
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