A temperature sensing signal acquisition circuit based on a differential amplification structure

Abstract

The utility model relates to temperature collection especially relates to a temperature sensing signal collection circuit based on differential amplification structure. Including temperature sensor, reference voltage source REF1 for output direct current reference voltage, reference resistance network, differential amplification circuit, output filter circuit. One end of temperature sensor is grounded, and the other end of temperature sensor is used as measurement node. One end of reference resistance network is connected with the output end of reference voltage source REF1. Differential amplification circuit includes operational amplifier U5A, and the inverting input end of operational amplifier is connected with first node through fourth resistance R63 and is connected with operational amplifier output end through fifth resistance R64, and the noninverting input end of operational amplifier is connected with the measurement node of temperature sensor through sixth resistance R75 and is grounded through seventh resistance R76.

Description

Technical Field

[0001] This utility model relates to temperature acquisition, and more particularly to a temperature sensing signal acquisition circuit based on a differential amplification structure. Background Technology

[0002] Platinum resistance thermometers (PT100, PT1000, etc.) are a type of temperature sensor widely used in industrial, building automation, and laboratory fields. Their resistance changes approximately linearly with temperature, offering advantages such as high accuracy, good stability, and good repeatability. Among them, PT1000, due to its higher resistance than PT100 at the same temperature, produces a larger output signal amplitude, which is beneficial for improving anti-interference capabilities and measurement resolution. Therefore, it is increasingly widely used in medium- to high-precision temperature measurement applications.

[0003] In existing technologies, temperature measurement of PT1000 commonly employs methods such as constant current source driving, bridge method, and proportional method. The main problems with these existing technologies include: complex circuit structure, high cost, significant temperature drift, poor anti-interference capability, and limited measurement accuracy. Especially in industrial environments, electromagnetic interference and temperature variations can severely affect the accuracy of the measurement results. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a temperature sensing signal acquisition circuit based on a differential amplification structure.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a temperature sensing signal acquisition circuit based on a differential amplifier structure, including a temperature sensor, a reference voltage source REF1 for outputting a DC reference voltage, a reference resistor network, a differential amplifier circuit, and an output filter circuit.

[0006] One end of the temperature sensor is grounded, and the other end of the temperature sensor serves as a measurement node.

[0007] One end of the reference resistor network is connected to the output of the reference voltage source REF1, and is used to jointly determine the excitation current and reference potential with the temperature sensor. The reference resistor network includes a first resistor R67, a second resistor R68, and a third resistor R73. One end of the first resistor R67 is connected to the reference voltage source REF1, and the other end of the first resistor R67 serves as a first node. One end of the second resistor R68 is connected to the first node, and the other end is grounded. One end of the third resistor R73 is connected to the reference voltage source REF1, and the other end of the third resistor R73 is connected to the measurement node of the temperature sensor.

[0008] The differential amplifier circuit includes operational amplifier U5A. The inverting input of the operational amplifier is connected to the first node via a fourth resistor R63 and to the output of the operational amplifier via a fifth resistor R64. The non-inverting input of the operational amplifier is connected to the measurement node of the temperature sensor via a sixth resistor R75 and to ground via a seventh resistor R76. This allows the operational amplifier to differentially amplify the difference between the voltage from the reference resistor network and the voltage from the temperature sensor branch.

[0009] Furthermore, the input terminal of the output filter circuit is connected to the output terminal of the operational amplifier U5A. The output terminal of the output filter circuit serves as the analog input terminal of the analog-to-digital converter (ADC) for low-pass filtering of the amplified temperature signal. The output filter circuit includes an eighth resistor R71 connected in series, and a first capacitor C36 connected in parallel with the output terminal of the eighth resistor R71 and grounded. The power supply terminal of the operational amplifier U5A is connected to a 3.3V power supply, and a decoupling capacitor is connected between it and ground through a second capacitor C38.

[0010] Furthermore, the first resistor R67, the second resistor R68, and the third resistor R73 in the reference resistor network are all made of precision metal film resistors. The resistance tolerance of the precision metal film resistor is no higher than 0.1%, and the temperature coefficient is preferably no higher than 5ppm / ℃.

[0011] Furthermore, the temperature sensor is a resistance temperature sensor.

[0012] Furthermore, the resistance ratio of the fourth resistor R63 to the fifth resistor R64 is equal to or a fixed ratio to the resistance ratio of the sixth resistor R75 to the seventh resistor R76, in order to set the voltage gain of the differential amplifier circuit. This amplifies the millivolt-level voltage difference generated by the resistance change of the temperature sensor to a suitable input range for the ADC.

[0013] Specifically, the output filter circuit forms a first-order RC low-pass filter to suppress high-frequency noise and external interference, thereby achieving anti-aliasing filtering for the subsequent ADC.

[0014] Furthermore, the operational amplifier U5A uses one channel of the TLC2272 dual operational amplifier chip, while the other operational amplifier channel is reserved for other analog signal processing.

[0015] Furthermore, the reference voltage source REF1 employs a voltage reference chip with an output reference voltage of 2.5V, which is used to simultaneously provide a voltage reference for the reference resistor network and the external analog-to-digital converter, thereby improving the accuracy and long-term stability of temperature measurement.

[0016] Compared with the prior art, this utility model has the following advantages.

[0017] This invention introduces a precision reference resistor network composed of R67, R68, and R73 and a differential amplifier structure with a TLC2272 operational amplifier as its core, which enables the millivolt-level voltage difference between the sensor branch and the reference branch to be amplified with high common-mode rejection and high linearity. The reference voltage source REF1 provides a unified reference for both the reference resistor network and the external ADC. Combined with a single power supply and an RC low-pass filter circuit at the output, it effectively reduces the impact of temperature drift on the zero point and gain, and suppresses power frequency interference and high-frequency noise.

[0018] Compared with traditional discrete multi-stage amplification schemes such as constant current source driving and bridge measurement, this utility model simplifies the circuit structure, reduces the number of components, and lowers material costs and debugging difficulty while ensuring high measurement accuracy and long-term stability. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the following description.

[0020] Figure 1 This is a circuit diagram of a temperature sensing signal acquisition circuit based on a differential amplifier structure, as shown in the embodiment.

[0021] Figure 2 This is a schematic diagram of the differential amplifier circuit in an embodiment.

[0022] Figure 3 This is a schematic diagram of the output filter circuit in an embodiment. Detailed Implementation

[0023] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0024] The terminology used in the embodiments of this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The singular forms “a,” “the,” and “the” as used in the embodiments of this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0025] Depending on the context, words such as “if” or “suppose” used here can be interpreted as “when”, “when”, “in response to determination”, or “in response to detection”.

[0026] For ease of understanding, the embodiments of this disclosure will be described in detail first.

[0027] like Figure 1-3 As shown in Example 1, a temperature sensing signal acquisition circuit based on a differential amplifier structure: This embodiment provides a temperature sensing signal acquisition circuit based on a differential amplifier structure, including a reference voltage source REF1, a temperature sensor CH1_PT1000, a reference resistor network, a differential amplifier circuit, and an output filter circuit.

[0028] The temperature sensor can be a PT1000 resistance temperature sensor, which can be connected to terminal CN10 via a four-wire connection. Two wires are used to introduce a constant excitation current, and the other two wires are used to measure the voltage across the sensor, thus reducing the impact of wire resistance on measurement accuracy. The typical resistance values ​​of the PT1000 at −20℃, 0℃, and 20℃ are approximately 922Ω, 1000Ω, and 1078Ω, respectively. This embodiment uses the PT1000 as an example for illustration, but this invention is not limited to this model.

[0029] The reference voltage source REF1 preferably uses a precision voltage reference chip to output a stable 2.5V DC reference voltage. REF1 serves two purposes: firstly, it provides the excitation voltage to the reference resistor network; secondly, it can be used as the reference voltage for an external analog-to-digital converter (ADC) to improve the consistency and stability of the entire signal chain.

[0030] The reference resistor network includes a first resistor R67, a second resistor R68, and a third resistor R73. One end of the first resistor R67 is connected to the output of the reference voltage source REF1, and the other end forms the first node. One end of the second resistor R68 is connected to the first node, and the other end is grounded. R67 and R68 form a voltage divider network to generate a first reference potential related to the reference voltage. One end of the third resistor R73 is connected to the reference voltage source REF1, and the other end is connected to the measurement node where the temperature sensor CH1_PT1000 is located. R73, together with the sensor resistor, sets the excitation current through the sensor and forms a temperature-related voltage signal.

[0031] The differential amplifier circuit uses one operational amplifier U5A from the TLC2272 dual operational amplifier chip. The inverting input of operational amplifier U5A is connected to the first node via the fourth resistor R63, and to the output of U5A via the fifth resistor R64. The non-inverting input of operational amplifier U5A is connected to the measurement node of the temperature sensor via the sixth resistor R75, and to ground via the seventh resistor R76. R63, R64, R75, and R76 form a differential amplifier resistor network. By appropriately selecting the resistance values ​​of each resistor, the operational amplifier amplifies the difference between the voltage from the reference resistor network branch and the voltage from the temperature sensor branch, achieving multiple linear amplification of the millivolt-level differential signal. In this embodiment, the resistance ratio of R63 to R64 and the resistance ratio of R75 to R76 are preferably designed to be equal or set in a fixed ratio to ensure good common-mode rejection ratio and gain accuracy.

[0032] The operational amplifier U5A is powered by a single power supply. Its power supply terminal is connected to the 3.3V system power supply, and the power supply is decoupled from the ground through the bypass capacitor C38 to suppress power supply ripple and high-frequency interference, ensuring that the amplifier operates under low noise conditions.

[0033] The output filter circuit is connected to the output of operational amplifier U5A. Specifically, the op-amp output is connected to node T1_ADC via resistor R71 (the eighth resistor). A first capacitor C36 is connected in parallel between node T1_ADC and ground. R71 and C36 form a first-order RC low-pass filter. By setting appropriate values ​​for R71 and C36, the cutoff frequency can be designed within the range of several hundred hertz to 1 kHz, effectively filtering out power frequency noise and high-frequency interference, thus providing anti-aliasing filtering. Node T1_ADC serves as the analog output of this acquisition circuit and is connected to the input of the subsequent analog-to-digital converter.

[0034] Through the above structure, this embodiment utilizes a reference resistor network to generate a stable reference potential and sensor excitation current. A differential amplifier circuit amplifies the voltage difference between the reference branch and the sensor branch, and the amplified voltage is then output after filtering by an output filter circuit, achieving high-precision acquisition of the PT1000 temperature sensor signal. Precision metal film resistors are preferably used for each resistive element, with a resistance tolerance of no more than 0.1% and a temperature coefficient of no more than 5 ppm / ℃, to further improve measurement accuracy and long-term stability.

[0035] Example 2: Temperature measurement system based on acquisition circuit.

[0036] Based on the acquisition circuit described in Embodiment 1, this embodiment provides a temperature measurement system. The system includes a temperature sensing signal acquisition circuit, a microprocessor, and a communication interface.

[0037] The output terminal T1_ADC of the temperature sensing signal acquisition circuit is connected to the analog input channel of the microprocessor's built-in analog-to-digital converter (ADC). The microprocessor is preferably a 32-bit microcontroller based on the ARM Cortex-M3 core, with a built-in 24-bit Σ-Δ ADC. The ADC sampling rate can be configured within the range of 10–1000Hz to adapt to the sampling requirements of different application scenarios. The microprocessor acquires the analog signal from the T1_ADC terminal according to the set sampling period and performs digital processing on the sampled data.

[0038] To further improve the accuracy and stability of temperature measurement, this embodiment installs a digital temperature sensor near the reference resistor network to monitor the circuit board's ambient temperature in real time. The microprocessor, based on the ambient temperature value collected by the digital temperature sensor and combined with a temperature compensation coefficient table stored in its internal memory, performs temperature compensation on the PT1000 measurement results, correcting the temperature drift of the reference resistor and other components.

[0039] The microprocessor performs digital filtering on the raw data output by the ADC, then calculates the current temperature value based on the calibration curve or lookup table relationship between the PT1000 resistor and temperature, and can linearize and correct nonlinear errors. The compensated temperature data is stored in a register or memory for retrieval by the host computer or other control units.

[0040] To facilitate system integration, the microprocessor in this embodiment also provides various industrial communication interfaces, such as RS485, CAN bus, and Ethernet interfaces. Through corresponding communication protocols, the temperature measurement system can easily connect to industrial fieldbuses or monitoring networks to achieve remote acquisition and monitoring of temperature data. In this embodiment, the RS485 interface can use the Modbus-RTU protocol, and the CAN interface can support CANopen or a custom protocol to adapt to different industrial control systems.

[0041] Ideally, the temperature measurement system operates within a temperature range of −50℃ to +150℃. By employing a low-temperature drift reference voltage source, a precision reference resistor network, and a differential amplifier structure, along with digital temperature compensation and digital filtering algorithms, the overall temperature measurement accuracy of the system can reach ±0.05℃, and its long-term temperature stability is better than 0.01℃ / year, meeting the requirements of industrial-grade high-precision temperature measurement applications.

[0042] It should be noted that the specific values ​​of the resistors and capacitors, the ADC resolution, and the communication interface type described in the above embodiments can be adjusted or replaced according to actual application requirements. Without changing the core idea of ​​this utility model, those skilled in the art can make various equivalent modifications or substitutions, all of which should fall within the protection scope of this utility model.

[0043] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "preferred embodiment," "detailed description," or "preferred embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0044] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Therefore, these modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the scope defined by the claims of this utility model.

Claims

1. A temperature sensing signal acquisition circuit based on a differential amplification structure, characterized in that, It includes a temperature sensor, a reference voltage source REF1 for outputting a DC reference voltage, a reference resistor network, a differential amplifier circuit, and an output filter circuit; One end of the temperature sensor is grounded, and the other end of the temperature sensor serves as a measurement node. One end of the reference resistor network is connected to the output of the reference voltage source REF1, and is used together with the temperature sensor to determine the excitation current and reference potential; The reference resistor network includes a first resistor R67, a second resistor R68, and a third resistor R73. One end of the first resistor R67 is connected to the reference voltage source REF1, and the other end of the first resistor R67 serves as the first node. One end of the second resistor R68 is connected to the first node, and the other end is grounded; one end of the third resistor R73 is connected to the reference voltage source REF1, and the other end of the third resistor R73 is connected to the measurement node of the temperature sensor. The differential amplifier circuit includes an operational amplifier U5A. The inverting input terminal of the operational amplifier is connected to the first node via a fourth resistor R63 and to the output terminal of the operational amplifier via a fifth resistor R64. The non-inverting input terminal of the operational amplifier is connected to the measurement node of the temperature sensor via a sixth resistor R75 and to ground via a seventh resistor R76.

2. The temperature sensing signal acquisition circuit of claim 1, wherein, The input terminal of the output filter circuit is connected to the output terminal of the operational amplifier U5A. The output terminal of the output filter circuit serves as the analog input terminal of the analog-to-digital converter (ADC) and is used to perform low-pass filtering on the amplified temperature signal. The output filter circuit includes an eighth resistor R71 connected in series and a first capacitor C36 connected in parallel with the output terminal of the eighth resistor R71 to ground. The power supply terminal of the operational amplifier U5A is connected to a 3.3V power supply and a decoupling capacitor is connected between it and ground through a second capacitor C38.

3. The temperature sensing signal acquisition circuit of claim 1, wherein, The first resistor R67, the second resistor R68, and the third resistor R73 in the reference resistor network are all made of precision metal film resistors. The resistance tolerance of the precision metal film resistor is no higher than 0.1%, and the temperature coefficient is no higher than 5ppm / ℃.

4. The temperature sensing signal acquisition circuit of claim 1, wherein, The temperature sensor is a resistance temperature sensor.

5. The temperature sensing signal acquisition circuit according to any one of claims 1-4, wherein, The resistance ratio of the fourth resistor R63 to the fifth resistor R64 is equal to or in a fixed ratio with the resistance ratio of the sixth resistor R75 to the seventh resistor R76, so as to set the voltage gain of the differential amplifier circuit.

6. The temperature sensing signal acquisition circuit of claim 1, wherein, The operational amplifier U5A uses one channel of the TLC2272 dual operational amplifier chip, while the other operational amplifier channel is reserved for other analog signal processing.

7. The temperature sensing signal acquisition circuit according to claim 1, characterized in that, The reference voltage source REF1 uses a voltage reference chip with an output reference voltage of 2.5V. This chip provides a voltage reference for both the reference resistor network and the external analog-to-digital converter, thereby improving the accuracy and long-term stability of temperature measurement.

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