High-precision temperature measurement module
By designing a multi-channel high-precision temperature measurement module, using thermistor and high-precision reference resistor to share a constant current source, combined with the four-wire connection of the ADC module, the problem that traditional temperature detection solutions cannot accurately detect multiple channels at the same time is solved. , achieving low-cost and high-precision temperature detection effect.
Patent Information
- Application Number
- CN202323475779.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-20
- Publication Date
- 2025-01-07
- Estimated Expiration
- 2033-12-20
AI Technical Summary
Traditional temperature detection solutions cannot accurately detect multiple channels at the same time, and are costly, making it difficult to meet the stable and low-cost temperature detection requirements of smart devices in functional testing.
A high-precision temperature measurement module including processing unit, power supply unit, communication unit and multiple collection units is designed. Thermistor and high-precision reference resistor share a constant current source, and four-wire connections are made through the ADC module to eliminate the conductors. The resistance value affects multi-channel temperature detection.
The high accuracy and low cost of multi-channel temperature detection are achieved, eliminating the impact of excitation current accuracy and temperature drift on the measured value, improving detection accuracy, and reducing equipment costs.
Smart Images
Figure CN222318254U_ABST
Abstract
Description
Technical Field
[0001] The utility model is applied to the technical field of temperature detection, and particularly relates to a high-precision temperature measurement module. Background Art
[0002] With the advancement of technology, smart products such as mobile phones, tablets, and smart wearable devices have become more and more popular in people's lives. The working temperature and working environment of mobile phones and tablets, as well as the ambient temperature detection and body temperature detection functions of smart wearable devices, require a stable and accurate temperature for functional testing, so it is necessary to accurately detect the temperature of the test environment. For example, when smart wearable devices perform body temperature function tests, temperature simulation is usually performed through a constant temperature water tank, and then a stable and basically the same test environment is provided during batch testing. The traditional solution for water tank temperature detection is usually to perform temperature detection through Fluke's 1524 thermometer. However, the thermometer is expensive and cannot perform temperature detection on multiple channels at the same time. If a temperature measurement module that can perform multi-channel temperature detection with high detection accuracy and low cost can be provided, the above problems can be well solved. Utility Model Content
[0003] The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide a high-precision temperature measurement module capable of multi-channel temperature detection and with low cost.
[0004] The technical solution adopted by the utility model is: the utility model includes a processing unit, a power supply unit, a communication unit and several groups of acquisition units, the power supply unit is connected to the processing unit, the communication unit and several groups of acquisition units for power supply, the processing unit communicates with an external host computer through the communication unit, several of the acquisition units are connected to the communication port of the processing unit, the acquisition unit includes a thermistor, an ADC module and a high-precision reference resistor, the acquisition port of the ADC module is connected to the thermistor with four wires, one end of the high-precision reference resistor is connected to the thermistor, and the other end of the high-precision reference resistor is connected to the reference end of the ADC module.
[0005] It can be seen from the above scheme that multi-channel testing is achieved by connecting multiple groups of the acquisition units through the processing unit. The acquisition port of the ADC module is connected to the thermistor through a four-wire connection, thereby eliminating the influence of the wire resistance on the test, which can improve the test accuracy. By adopting a connection method in which the thermistor and the high-precision reference resistor share a constant current source, the absolute accuracy and temperature drift of the excitation current will not affect the measured value. In the absence of leakage current, the measured value of the measurement module only depends on the resistance of the thermistor and the high-precision reference resistor.
[0006] A preferred solution is that the thermistor is a resistor device of model PT1000, the accuracy of the high-precision reference resistor is one ten-thousandth and the temperature drift coefficient is less than 10ppm / °C.
[0007] A preferred solution is that the ADC module is an analog-to-digital converter of model ADS124S08, the AIN0 port and AIN1 port of the analog-to-digital converter are connected to one end of the thermistor, the AIN2 port, REFP0 port of the analog-to-digital converter, and one end of the high-precision reference resistor are all connected to the other end of the thermistor, and the other end of the high-precision reference resistor is connected to the EEFN0 port of the analog-to-digital converter.
[0008] A preferred solution is that the AIN0 port of the analog-to-digital converter is connected to an internal programmable constant current source and outputs current to the thermistor and the high-precision reference resistor, the AIN1 port and AIN2 port of the analog-to-digital converter are connected to the positive and negative input terminals of the internal amplifier, and the REFP0 port and REFN0 port of the analog-to-digital converter are both connected to the reference terminal of the internal amplifier. BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 It is a connection schematic diagram of the utility model;
[0010] Figure 2 is a circuit schematic diagram of the acquisition unit;
[0011] Figure 3 is a simplified diagram of the collection principle of the collection unit;
[0012] Figure 4 is a simplified diagram of the filtering principle of the acquisition unit;
[0013] Figure 5 is a circuit schematic diagram of the memory. DETAILED DESCRIPTION
[0014] like Figure 1As shown, in this embodiment, the utility model includes a processing unit 1, a power supply unit 2, a communication unit 3 and several groups of acquisition units 4, the power supply unit 2 is connected to the processing unit 1, the communication unit 3 and several of the acquisition units 4 for power supply, the processing unit 1 communicates with an external host computer 5 through the communication unit 3, and several of the acquisition units 4 are connected to the communication port of the processing unit 1, the acquisition unit 4 includes a thermistor RPT1000, an ADC module 6 and a high-precision reference resistor RREF, the acquisition port of the ADC module 6 is four-wire connected to the thermistor RPT1000, one end of the high-precision reference resistor RREF is connected to the thermistor RPT1000, and the other end of the high-precision reference resistor RREF is connected to the reference end of the ADC module 6.
[0015] In this embodiment, the thermistor RPT1000 is a resistor device of model PT1000, and the accuracy of the high-precision reference resistor RREF is one ten-thousandth and the temperature drift coefficient is less than 10ppm / °C.
[0016] like Figure 1 and Figure 5 As shown, in this embodiment, the utility model further includes a memory 7, the memory 7 is a memory chip U703 of model CAT24C32YI-GT3, and the memory chip U703 is compatible with I2C communication; Figure 5 As shown, resistors R718 and R719 are pull-up resistors of I2C, and ports A0, A1 and A2 are address selection pins of the chip. This circuit is used to record the calibration parameters and related data of the thermistor RPT1000.
[0017] In this embodiment, the processing unit 1 is a microprocessor of the STM32 series, the power supply unit 2 includes a linear regulator of model LT3045EMSE, the communication unit 3 includes an embedded Ethernet controller of model W5500 and an interface conversion chip of model FT232RL, and the processing unit 1 communicates with an external computer through the embedded Ethernet controller or the interface conversion chip.
[0018] like Figure 2As shown, in this embodiment, the ADC module 6 is an analog-to-digital converter of model ADS124S08, the AIN0 port and AIN1 port of the analog-to-digital converter are connected to one end of the thermistor RPT1000, the AIN2 port, REFP0 port of the analog-to-digital converter, and one end of the high-precision reference resistor RREF are all connected to the other end of the thermistor RPT1000, and the other end of the high-precision reference resistor RREF is connected to the EEFN0 port of the analog-to-digital converter. The AIN0 port of the analog-to-digital converter is connected to an internal programmable constant current source and outputs current to the thermistor RPT1000 and the high-precision reference resistor RREF, the AIN1 port and AIN2 port of the analog-to-digital converter are connected to the positive and negative input terminals of the internal amplifier, and the REFP0 port and REFN0 port of the analog-to-digital converter are both connected to the reference terminal of the internal amplifier.
[0019] ADS124S08 is a 24-bit high-precision analog-to-digital converter with 12 inputs, which can provide low-latency conversion results and 50Hz or 60Hz noise suppression in noisy industrial environments; and has a programmable gain amplifier (PGA) with low noise characteristics, and can provide a gain of 1 to 128, which can amplify large-value signals for resistor bridges, and has two programmable excitation current sources (IDACs) to provide accurate resistance temperature detector (RTD) bias. The analog-to-digital converter is compatible with SPI communication, with the CS port as the chip select pin, the SCLK port as the data clock pin, the DIN port as the data input pin, and the DOUT / DRDY port as the data output pin. The AVDD port and DVDD port of the analog-to-digital converter are both powered by 3V3, the AIN0 pin is set to 0.1ma current output, the connector J701 is used for four-wire connection of the thermistor RPT1000, the AIN1 pin and the AIN2 pin are used as the voltage input of the thermistor RPT1000, according to U=R*I, the voltage value is between 80 and 200mv, and the resistor R727 is the high-precision reference resistor RREF that cooperates with the thermistor RPT1000, so the proportional measurement method has no requirements for the accuracy of the constant current source, but it is closely related to the high-precision reference resistor RREF, and a slight deviation can cause a large measurement error, so the high-precision reference resistor RREF selects a chip resistor with a resistance value of 10k, an accuracy of ±0.01%, and a temperature coefficient of ±0.2ppm / °C. The REFN0 port and the REFP0 port of the analog-to-digital converter are used as the voltage measurement input of the reference resistor, and the voltage value is 1V.
[0020] like Figure 3As shown in the figure, Leadx represents the line resistance connected to the thermistor RPT1000. The resistance range of the thermistor RPT1000 is between 800 and 2120. Therefore, under the action of a 0.1ma constant current source, according to the calculation formula V=RI, the voltage variation range of the thermistor RPT1000 is between 80 and 210mv. The AIN1 port and the AIN2 port serve as the voltage input terminals of the thermistor RPT1000. The signal is amplified 8 times by the internal operational amplifier and then connected to the analog-to-digital conversion part inside the ADC module 6. The high-precision reference resistor RREF serves as the reference resistor of the thermistor RPT1000. Under the action of a 0.1ma constant current source, the voltage of 10k resistance is 1V.
[0021] In this embodiment, the ratio measurement method can be used to obtain:
[0022] R PT1000 / R REF =U PT1000 / U REF , U PT1000 =I IDAC1 *R PT1000 , U REF =I IDAC2 *R REF ;
[0023] Because the high-precision reference resistor RREF and the thermistor RPT1000 use the same constant current source, the current I IDAC1 =I IDAC2 , while R PT1000 =U PT1000 *R REF / U REF Therefore, the measured value of the ADC module 6 depends on the resistance values of the thermistor RPT1000 and the high-precision reference resistor RREF, but not on the IDAC current value. Therefore, the absolute accuracy and temperature drift of the excitation current are irrelevant.
[0024] In ratiometric measurement, as long as the IDAC has no leakage current outside the circuit, the measurement value of the ADC module 6 depends only on the values of the thermistor RPT1000 and the high-precision reference resistor RREF, and the ADC module 6 does not need to convert into voltage.
[0025] An RC filter circuit is provided between the ADC module 6, the thermistor RPT1000, and the high-precision reference resistor RREF. Through input filtering, the differential signal is attenuated at a lower frequency than the common-mode signal, and is thus significantly suppressed by the PGA of the device. The bandwidth of the differential signal is low, which reduces the impact of input common-mode capacitance mismatch. The input filter of the ADC module 6 input and the reference input is designed to have the same bandwidth.
[0026] f IN_DIFF =1 / [2•π•C IN_DIFF (R PT1000 +2•R IN )];
[0027] f REF = 1 / [2 •π•C REF •(R REF +R IN_REF )];
[0028] like Figure 4 From the schematic diagram and the above formula, it can be obtained that the differential input bandwidth of the thermistor RPT1000 and the high-precision reference resistor RREF are both close to 240HZ. Keeping the bandwidth close can reduce noise in the measurement, where C is the capacitance and f is the bandwidth frequency.
[0029] Although the embodiments of the present invention are described with practical solutions, they do not constitute limitations on the meaning of the present invention. For those skilled in the art, it is obvious to modify the implementation scheme and combine it with other solutions based on this description.
Claims
1. A high-precision temperature measurement module, characterized in that: It comprises a processing unit (1), a power supply unit (2), a communication unit (3) and a plurality of acquisition units (4); the power supply unit (2) is connected to the processing unit (1), the communication unit (3) and a plurality of acquisition units (4) for power supply; the processing unit (1) communicates with an external host computer (5) via the communication unit (3); a plurality of acquisition units (4) are connected to a communication port of the processing unit (1); the acquisition unit (4) comprises a thermistor (RPT1000), an ADC module (6) and a high-precision reference resistor RREF; a four-wire acquisition port of the ADC module (6) is connected to the thermistor (RPT1000); one end of the high-precision reference resistor RREF is connected to the thermistor (RPT1000); and the other end of the high-precision reference resistor RREF is connected to a reference end of the ADC module (6).
2. A high-precision temperature measurement module according to claim 1, characterized in that: The thermistor (RPT1000) is a resistor device of model PT1000, and the accuracy of the high-precision reference resistor RREF is one ten-thousandth and the temperature drift coefficient is less than 10ppm / °C.
3. A high-precision temperature measurement module according to claim 1, characterized in that: The ADC module (6) is an analog-to-digital converter of model ADS124S08, the AIN0 port and AIN1 port of the analog-to-digital converter are connected to one end of the thermistor (RPT1000), the AIN2 port and REFP0 port of the analog-to-digital converter, and one end of the high-precision reference resistor RREF are all connected to the other end of the thermistor (RPT1000), and the other end of the high-precision reference resistor RREF is connected to the EEFN0 port of the analog-to-digital converter.
4. A high-precision temperature measurement module according to claim 3, characterized in that: The AIN0 port of the analog-to-digital converter is connected to an internal programmable constant current source and outputs current to the thermistor (RPT1000) and the high-precision reference resistor RREF, the AIN1 port and AIN2 port of the analog-to-digital converter are connected to the positive and negative input terminals of the internal amplifier, and the REFP0 port and REFN0 port of the analog-to-digital converter are both connected to the reference terminal of the internal amplifier.