High-precision calibration-free PT1000 measurement method, device and system

Abstract

The invention relates to the technical field of temperature measurement, and discloses a high-precision calibration-free PT1000 measurement method, device and system. According to the method, a voltage signal and a reference voltage signal of the PT1000 are respectively obtained through a voltage division branch and a reference voltage branch which are formed by a high-precision reference source and a precision resistor, and after differential amplification and analog-to-digital conversion, the real-time resistance value of the PT1000 is calculated by a processing unit. And finally, inquiring a pre-stored PT1000 standard indexing table and adopting an interpolation algorithm to obtain a high-resolution temperature measurement value. According to the scheme, through high-stability hardware design and a standard table look-up algorithm, a complex field calibration process is avoided, and high-precision and high-stability temperature measurement in a wide temperature range is realized.

Description

Technical Field

[0001] This invention relates to the field of temperature measurement technology, specifically to a high-precision, calibration-free PT1000 measurement method, apparatus, and system. Background Technology

[0002] In the field of industrial temperature measurement, platinum resistance thermometers (such as PT100 and PT1000) are widely used due to their good stability and high accuracy. For example, PT1000 is commonly used for temperature measurement in charging piles, and some standards require that the temperature difference between the positive and negative electrodes inside the charging head should be less than 5°C. Although the temperature-resistance relationship of PT1000 follows the Callendar-Van Dusen equation defined by the IEC 60751 standard, this formula is complex to calculate. This invention constructs an "ideal" measurement hardware system with negligible error by using an ultra-high precision, low-temperature drift reference source, operational amplifier, and resistors. This system directly measures the precise resistance value of the platinum resistance thermometer and obtains the temperature value by consulting the IEC standard calibration table, which is completely consistent with the formula, combined with an interpolation algorithm. This method avoids real-time calculation of complex formulas and eliminates the tedious process of on-site temperature point calibration of the entire system, achieving a unity of high precision and calibration-free operation in principle.

[0003] To accurately deduce the temperature value from the measured resistance value, current techniques mainly rely on a calibration process: 1. Two-point calibration method: Measure the resistance of the platinum resistance thermometer at two known temperature points (e.g., 0°C for an ice-water mixture and 100°C for boiling water) and establish a linear equation. This method ignores the nonlinearity of the platinum resistance thermometer's characteristics and introduces significant errors over a wide temperature range. Calibration is essentially compensation for the overall system error of the sensor and measurement circuit.

[0004] 2. Multi-point calibration method: Measurements are taken at multiple temperature points, and the true characteristics are approximated through piecewise linear fitting or high-order curve fitting. This method has high accuracy, but requires a complex calibration process and more calibration time, leading to increased production costs and reduced production efficiency.

[0005] Regardless of the method used, physical temperature point calibration is required at the production or usage site, a cumbersome process, and the calibration accuracy is affected by the calibration equipment and environment. Therefore, the industry urgently needs a technical solution that can achieve high-precision measurement over a wide temperature range without requiring complex on-site calibration. Summary of the Invention

[0006] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a high-precision, calibration-free PT1000 measurement method, device, and system, thereby solving the problems of limited accuracy, low efficiency, and high cost caused by the reliance on on-site physical calibration procedures in traditional PT1000 temperature measurement technology.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: In a first aspect, the present invention provides a high-precision, calibration-free PT1000 measurement method, comprising: The first voltage signal at the upper end of the PT1000 platinum resistance sensor is obtained through a voltage divider branch formed by the first reference voltage source, the first voltage divider resistor and the PT1000 platinum resistance sensor connected in series. The reference voltage signal is obtained through the reference voltage branch formed by the first reference voltage source, the second voltage divider resistor and the reference resistor connected in series; The difference between the first voltage signal and the reference voltage signal is amplified by a differential amplifier circuit to obtain a conditioned second voltage signal; The second voltage signal is converted into a digital signal using an analog-to-digital converter with a second reference voltage source as a reference. Calculate the real-time resistance value of the PT1000 platinum resistance sensor based on digital signals and circuit parameters; The calculated real-time resistance value is compared with the pre-stored PT1000 standard calibration table. When the real-time resistance value is equal to the standard resistance value in the PT1000 standard calibration table, the corresponding temperature measurement value is directly output. When the real-time resistance value is not equal to the standard resistance value in the PT1000 standard calibration table, the temperature measurement value is obtained by interpolation.

[0008] Preferably, in one possible implementation of the first aspect, the reference voltage signal is the voltage at the voltage divider point of the first reference voltage source in the series branch of the second voltage divider resistor and the reference resistor.

[0009] Preferably, in one possible implementation of the first aspect, the reference voltage signal is buffered by a voltage buffer and then input to the inverting input terminal of the differential amplifier circuit.

[0010] Preferably, in one possible implementation of the first aspect, the circuit parameters include the voltage value of the first reference voltage source, the voltage value of the second reference voltage source, the resistance value of the first voltage divider resistor, the resistance value of the reference resistor, and the amplification factor of the differential amplifier circuit.

[0011] Preferably, in one possible implementation of the first aspect, the pre-stored PT1000 standard calibration table is a temperature-resistance correspondence table generated according to the IEC60751 standard with intervals of 0.1°C.

[0012] Preferably, in one possible implementation of the first aspect, the interpolation calculation to obtain the temperature measurement value includes: When the real-time resistance value is between the first and second standard resistance values ​​corresponding to adjacent first and second standard temperature points in the standard calibration table, the temperature measurement value is calculated using a linear interpolation formula based on the first and second standard temperature points.

[0013] Preferably, in one possible implementation of the first aspect, the linear interpolation formula is:

[0014] in, This is a temperature measurement value. , The first standard temperature point and the second standard temperature point, , These are the first standard resistance values ​​and the second standard resistance values ​​corresponding to the first standard temperature point and the second standard temperature point, respectively. This is the real-time resistance value.

[0015] In a second aspect, the present invention provides a high-precision, calibration-free PT1000 measuring device, the device being used to implement a high-precision, calibration-free PT1000 measuring method as described in the first aspect, comprising: The voltage divider and excitation unit includes a first reference voltage source, which is connected in series with a PT1000 platinum resistance sensor through a first voltage divider resistor to form a voltage divider branch. The signal conditioning unit includes a reference voltage generation branch and a differential amplifier circuit. The reference voltage generation branch is composed of a first reference voltage source, a second voltage divider resistor, and a reference resistor connected in series. The differential amplifier circuit is used to amplify the difference between the voltage at the upper end of the PT1000 platinum resistance sensor in the voltage divider branch and the voltage at the voltage divider point of the reference voltage generation branch. The analog-to-digital conversion unit has its input terminal connected to the output terminal of the signal conditioning unit, and its reference voltage is provided by a second reference voltage source. The intelligent computing processing unit, connected to the analog-to-digital conversion unit, is used to calculate the real-time resistance value of the PT1000 platinum resistance sensor based on the digital signal and circuit parameters output by the analog-to-digital conversion unit, and to obtain the temperature measurement value through interpolation based on the pre-stored PT1000 standard calibration table.

[0016] Thirdly, the present invention provides a high-precision calibration-free PT1000 measurement system, including a high-precision calibration-free PT1000 measurement device as described in the second aspect, and a host computer or management system communicatively connected to the measurement device.

[0017] The beneficial effects of this invention are: by combining a highly stable hardware and software lookup table algorithm, a balance between high precision and no on-site calibration is achieved.

[0018] The hardware employs an independent high-precision reference source and low-temperature drift precision components to keep the overall error and temperature drift of the measurement link at a low level, ensuring excellent measurement accuracy and repeatability over a wide temperature range.

[0019] The circuit design uses a large-value resistor to limit the sensor's operating current and eliminate self-heating error; the added voltage buffer ensures the long-term stability of the reference voltage.

[0020] The software abandons complex formula calculations and directly queries the international standard calibration table and combines it with interpolation algorithms, so that the measurement results can be directly traced to international standards and obtain high-resolution temperature output.

[0021] This solution enables the device to have reliable high-precision measurement capabilities right after leaving the factory, without any on-site calibration, which greatly simplifies the production and application process and achieves long-term maintenance-free and highly stable operation. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This application provides a flowchart of a high-precision, calibration-free PT1000 measurement method.

[0024] Figure 2 This application provides a principle block diagram of a high-precision, calibration-free PT1000 measuring device.

[0025] Figure 3 This application provides a circuit diagram of a high-precision, calibration-free PT1000 measuring device.

[0026] Figure 4 This application provides a schematic diagram of a reference voltage buffer circuit for a high-precision, calibration-free PT1000 measuring device. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1: As Figure 1As shown, the present invention provides a high-precision, calibration-free PT1000 measurement method, which realizes high-precision, calibration-free measurement of the temperature of PT1000 platinum resistance sensor based on a high-precision, calibration-free PT1000 measurement device.

[0029] The first step is signal acquisition and conditioning. This step is performed in a hardware circuit environment that includes a high-precision reference source and precision resistors. The block diagram is as follows: Figure 2 As shown, through the first reference voltage source First voltage divider resistor The voltage divider branch, connected in series with the PT1000 platinum resistance sensor, acquires the first voltage signal from the upper end of the PT1000. The value of this voltage signal is determined by the real-time resistance value of the PT1000. The decision, their relationship is .

[0030] Through the first reference voltage source Second voltage divider resistor With precision reference resistor A reference voltage branch formed by series connection is used to obtain a fixed reference voltage signal. The reference voltage signal is the voltage divided by the first reference voltage source across the second voltage divider resistor and the precision reference resistor, and its value is... .

[0031] In this embodiment, the reference voltage signal Before subsequent processing, it is buffered by a voltage buffer to eliminate the load effect and ensure its stability.

[0032] Subsequently, the first voltage signal was processed using a differential amplifier circuit. With reference voltage signal The difference is amplified. Let the amplification factor of the differential amplifier circuit be... Then its output is a conditioned second voltage signal. for The small differential signal reflecting the resistance change of the PT1000 was extracted, and common-mode interference was suppressed.

[0033] Next, the analog-to-digital conversion step is performed. This is done using a separate second reference voltage source. The analog-to-digital converter, acting as a reference voltage, converts the second voltage signal into analog form. Convert to digital signal For a resolution of A bit-level analog-to-digital converter, whose conversion relationship is expressed as: Second reference voltage source Independent of the first reference voltage source This ensures the stability of the analog-to-digital conversion reference and isolates power supply noise.

[0034] Then, the resistance value calculation step is performed. This step is completed by the intelligent computing processing unit (a microcontroller in this embodiment). Digital signals are received. Based on the known circuit parameters, the real-time resistance value of the PT1000 platinum resistance sensor was calculated in reverse. The circuit parameters include: the voltage value of the first reference voltage source. The voltage value of the second reference voltage source The resistance value of the first voltage divider resistor The resistance value of the reference resistor and the amplification factor of the differential amplifier circuit The calculation process is as follows: First, from the digital signal... The amplified voltage value is derived by inverting the reference voltage of the analog-to-digital converter, i.e. Then, based on the magnification factor... To obtain the input voltage difference of the differential amplifier circuit, i.e. Due to the reference voltage signal The actual value of the first voltage signal at the upper end of the PT1000 is obtained by calculating fixed known values ​​from circuit parameters. Finally, based on the relationship between voltage and resistance in the voltage divider branch, the real-time resistance value of the PT1000 is calculated. The calculation formula is: .

[0035] Finally, the temperature calculation step is performed, converting the resistance value into a temperature value through table lookup and interpolation. The intelligent computing unit pre-stores a PT1000 temperature-resistance standard calibration table generated according to the IEC60751 standard. This calibration table stores a series of standard temperature points in 0.1℃ intervals. and the corresponding standard resistance value The mapping relationship is established. Real-time resistance values ​​are obtained. Then, it is compared and calculated with the standard calibration table. The calculation follows a defined logic: if the calculated real-time resistance value... It is exactly equal to a certain standard resistance value in the standard calibration table. Then the corresponding standard temperature value will be output directly. As the final temperature measurement result. In most cases, the real-time resistance value. It is not directly equal to any standard value in the calibration table, but rather lies between two adjacent standard temperature points in the calibration table. and Between the corresponding standard resistance values, among which At this point, the final temperature measurement value is calculated using a linear interpolation formula. The linear interpolation formula is: .in, and for , The corresponding standard resistance values, This is the calculated real-time resistance value. The algorithm is based on the principle that platinum resistance thermometers exhibit good linearity within a small temperature range. It resolves discrete standard calibration tables into continuous, high-resolution temperature outputs, achieving a temperature measurement resolution higher than the calibration table intervals.

[0036] Example 2: The present invention provides a lookup interpolation algorithm based on a standard gradation table. This is only an example to illustrate the specific implementation of the method and does not constitute a limitation on the scope of protection of the present invention.

[0037] The microcontroller stores the IEC 60751 standard PT1000 calibration table (0.1℃ interval), and then obtains the precise resistance value of the PT1000 through hardware measurement. Calculations yielded By consulting the PT1000 calibration table with 0.1℃ intervals generated according to the IEC60751 standard stored in the MCU's Flash memory, it was found that 0.1℃ corresponds to the resistance... Resistance at 0℃ .because Temperature was calculated using linear interpolation.

[0038] This yields the output temperature measurement value.

[0039] Example 3: Figure 3 As shown, this invention provides a differential amplifier circuit, and this embodiment uses... The TI REF5030IDGKR (3.0V, ±0.05%, temperature drift 3ppm / ℃) was selected. (Accuracy 0.1%, temperature drift 5ppm / ℃) The external resistors of differential op-amp U1 , Magnification The operational amplifier selected is the ADI ADA4528-1, whose typical input offset voltage is... Temperature drift .

[0040] The working principle of a differential amplifier circuit is as follows: Reference voltage PT1000 upper voltage Op-amp output MCU read The result was obtained by reverse calculation. Current ,final This embodiment effectively extracts small signals through differential amplification and limits the sensor's operating current.

[0041] Example 4: Figure 4 As shown, this invention provides an optimized hardware solution with a reference voltage buffer. This embodiment, based on embodiment three, optimizes for potential load effects. A voltage follower U1B is added between the voltage divider point of the reference branch and the inverting input of the differential operational amplifier U1. The voltage follower U1B has extremely high input impedance, completely isolating the voltage divider network from subsequent circuitry. and The influence of ) ensures the reference voltage Its precision and stability.

[0042] Example 5: This invention provides a high-precision, calibration-free PT1000 measuring device, comprising: The voltage divider and excitation unit includes a first reference voltage source, which is connected in series with a PT1000 platinum resistance sensor through a first voltage divider resistor to form a voltage divider branch. The signal conditioning unit includes a reference voltage generation branch and a differential amplifier circuit. The reference voltage generation branch is composed of a first reference voltage source, a second voltage divider resistor, and a reference resistor connected in series. The differential amplifier circuit is used to amplify the difference between the voltage at the upper end of the PT1000 platinum resistance sensor in the voltage divider branch and the voltage at the voltage divider point of the reference voltage generation branch. The analog-to-digital conversion unit has its input terminal connected to the output terminal of the signal conditioning unit, and its reference voltage is provided by a second reference voltage source. The intelligent computing processing unit, connected to the analog-to-digital conversion unit, is used to calculate the real-time resistance value of the PT1000 platinum resistance sensor based on the digital signal and circuit parameters output by the analog-to-digital conversion unit, and to obtain the temperature measurement value through interpolation based on the pre-stored PT1000 standard calibration table.

[0043] Example 6: The present invention provides a high-precision calibration-free PT1000 measurement system, including a high-precision calibration-free PT1000 measurement device as described in Example 5, and a host computer or management system that is communicatively connected to the measurement device.

[0044] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high-precision, calibration-free PT1000 measurement method, characterized in that, include: The first voltage signal at the upper end of the PT1000 platinum resistance sensor is obtained through a voltage divider branch formed by the first reference voltage source, the first voltage divider resistor and the PT1000 platinum resistance sensor connected in series. The reference voltage signal is obtained through the reference voltage branch formed by the first reference voltage source, the second voltage divider resistor and the reference resistor connected in series; The difference between the first voltage signal and the reference voltage signal is amplified by a differential amplifier circuit to obtain a conditioned second voltage signal; The second voltage signal is converted into a digital signal using an analog-to-digital converter with a second reference voltage source as a reference. Calculate the real-time resistance value of the PT1000 platinum resistance sensor based on digital signals and circuit parameters; The calculated real-time resistance value is compared with the pre-stored PT1000 standard calibration table. When the real-time resistance value is equal to the standard resistance value in the PT1000 standard calibration table, the corresponding temperature measurement value is directly output. When the real-time resistance value is not equal to the standard resistance value in the PT1000 standard calibration table, the temperature measurement value is obtained by interpolation.

2. The high-precision, calibration-free PT1000 measurement method as described in claim 1, characterized in that, The reference voltage signal is the voltage at the voltage divider point of the first reference voltage source on the series branch of the second voltage divider resistor and the reference resistor.

3. The high-precision, calibration-free PT1000 measurement method as described in claim 2, characterized in that, The reference voltage signal is buffered by a voltage buffer and then input to the inverting input of the differential amplifier circuit.

4. The high-precision, calibration-free PT1000 measurement method as described in claim 1, characterized in that, The circuit parameters include the voltage value of the first reference voltage source, the voltage value of the second reference voltage source, the resistance value of the first voltage divider resistor, the resistance value of the reference resistor, and the amplification factor of the differential amplifier circuit.

5. The high-precision, calibration-free PT1000 measurement method as described in claim 4, characterized in that, The pre-stored PT1000 standard calibration table is a temperature-resistance correspondence table generated according to the IEC60751 standard, with intervals of 0.1℃.

6. The high-precision, calibration-free PT1000 measurement method as described in claim 5, characterized in that, The interpolated temperature measurements include: When the real-time resistance value is between the first and second standard resistance values ​​corresponding to adjacent first and second standard temperature points in the standard calibration table, the temperature measurement value is calculated using a linear interpolation formula based on the first and second standard temperature points.

7. The high-precision, calibration-free PT1000 measurement method as described in claim 6, characterized in that, The linear interpolation formula is as follows: in, This is a temperature measurement value. , The first standard temperature point and the second standard temperature point, , These are the first standard resistance values ​​and the second standard resistance values ​​corresponding to the first standard temperature point and the second standard temperature point, respectively. This is the real-time resistance value.

8. A high-precision, calibration-free PT1000 measuring device, characterized in that, The apparatus is used to implement a high-precision, calibration-free PT1000 measurement method as described in any one of claims 1 to 7, comprising: The voltage divider and excitation unit includes a first reference voltage source, which is connected in series with a PT1000 platinum resistance sensor through a first voltage divider resistor to form a voltage divider branch. The signal conditioning unit includes a reference voltage generation branch and a differential amplifier circuit. The reference voltage generation branch is composed of a first reference voltage source, a second voltage divider resistor, and a reference resistor connected in series. The differential amplifier circuit is used to amplify the difference between the voltage at the upper end of the PT1000 platinum resistance sensor in the voltage divider branch and the voltage at the voltage divider point of the reference voltage generation branch. The analog-to-digital conversion unit has its input terminal connected to the output terminal of the signal conditioning unit, and its reference voltage is provided by a second reference voltage source. The intelligent computing processing unit, connected to the analog-to-digital conversion unit, is used to calculate the real-time resistance value of the PT1000 platinum resistance sensor based on the digital signal and circuit parameters output by the analog-to-digital conversion unit, and to obtain the temperature measurement value through interpolation based on the pre-stored PT1000 standard calibration table.

9. A high-precision, calibration-free PT1000 measurement system, characterized in that, The system includes a high-precision, calibration-free PT1000 measuring device as described in claim 8, and a host computer or management system that is communicatively connected to the measuring device.

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