Traceable temperature measurement probe structure and traceable calibration method thereof

Abstract

The application discloses a traceable temperature measuring probe structure and a traceable calibration method thereof, and the structure is composed of a probe mechanical structure, a phase change material, a flexible heating sheet and a platinum resistance; the phase change material is encapsulated in a hollow cylinder on the probe mechanical structure; the flexible heating sheet is attached to the outer surface of the hollow cylinder on the probe mechanical structure, and the flexible heating sheet is connected to a power supply through two wires to perform heating operation; the platinum resistance is arranged in a groove directly below the hollow cylinder on the probe mechanical structure, and four-wire method is adopted to perform temperature measurement operation. The temperature measuring probe structure is suitable for long-term and high-precision application occasions, and has the advantages that the measurement result can be calibrated according to the definition of international temperature scale, the temperature measuring probe structure does not need to be disassembled, and the drift of the temperature measurement result caused by the performance change of the platinum resistance and the temperature measurement electronics part is weakened.

Description

Technical fields:

[0001] This invention relates to high-resolution temperature measurement technology, long-term high-accuracy temperature measurement technology, and temperature traceability technology, specifically to a traceable temperature measurement probe structure, which can be widely used in temperature measurement fields with long service life and high accuracy requirements. Background technology:

[0002] Achieving long-term, high-accuracy temperature measurement is of significant practical importance for scientific research and industrial control. However, due to the aging and drift of components on platinum resistance thermometers and analog signal acquisition circuit boards, temperature measurement results often exhibit significant deviations, necessitating periodic calibration. However, in applications such as tunnels, mines, deep seas, and satellites, disassembling and calibrating temperature sensing elements is difficult, or even impossible. For example, when measuring the temperature of deep-sea structural components, the performance of the platinum resistance thermometers on these components changes due to aging after long-term use, resulting in inaccurate measurement results. Unless the deep-sea structural components are recovered and the platinum resistance thermometers are disassembled and replaced, calibration is difficult, costly, and challenging. Currently, no technology similar to this invention has been found in publicly available literature. Summary of the Invention:

[0003] The main purpose of this invention is to solve the problems of temperature measurement drift and low accuracy under long service life. By using a four-wire platinum resistance thermometer connection method, the influence of wire resistance and thermoelectric potential on the measurement results is eliminated. Utilizing the international temperature scale definition and the characteristic that the temperature of phase change materials remains basically constant during phase change, the temperature measurement results of platinum resistance thermometers are traced and calibrated without disassembling the device. This eliminates the drift of temperature measurement results caused by performance changes due to aging, thereby realizing temperature measurement that can be applied to scenarios with long service life, high resolution, and high accuracy.

[0004] The entire traceable temperature measurement probe structure comprises a probe mechanical structure, a phase change material, a flexible heating element, and a platinum resistance thermometer. The phase change material is encapsulated within a hollow cylinder on the probe mechanical structure. The flexible heating element is attached to the outer surface of the hollow cylinder on the probe mechanical structure and is connected to a power source via two wires for heating. The platinum resistance thermometer is placed in a groove directly below the hollow cylinder on the probe mechanical structure, employing a four-wire method for temperature measurement. A schematic diagram of the probe mechanical structure of this invention is shown below. Figure 2 As shown.

[0005] When this temperature measurement probe structure is calibrated for temperature traceability, its circuit structure model is as follows: Figure 3 As shown in Figure 4. Where r and E are the wire resistance and thermoelectric potential due to temperature difference on the long wire, respectively, and I... S To excite the constant current source of the platinum resistance thermometer, U RU is the voltage across the platinum resistance thermometer, and U is the constant voltage drive on the flexible heating element. The flexible heating element is simplified to have a resistance of R. C Pure resistance.

[0006] The method of using this invention is as follows:

[0007] 1. Before the temperature measurement probe structure is installed and used, select the phase change material that is closest to the definition of the international temperature scale according to the actual temperature measurement range of the application, and encapsulate it in the hollow cylinder of the probe's mechanical structure;

[0008] 2. Constant current source I S The platinum resistance is excited by applying a voltage U across its terminals using another set of wires on the platinum resistance. R Perform measurements, calculate the platinum resistance value R, and convert it to the current measured temperature value t.

[0009] 3. A constant voltage U is provided to the flexible heating element to heat the phase change material. The temperature data collected by the platinum resistance thermometer shows a sudden and gradual slowdown in the heating rate. Figure 4 As shown, the measured temperature t at this time is calibrated as the phase transition temperature T0 of the phase change material, thus completing the temperature traceability calibration of the platinum resistance thermometer and subsequent temperature measurement electronics system.

[0010] Since the voltage acquisition device across a platinum resistance thermometer is typically an instrumentation amplifier with extremely high input impedance, and the thermoelectric potential across different conductors is almost equal, the conductor resistance r and the thermoelectric potential E can be ignored. The formula for calculating the resistance of a platinum resistance thermometer is as follows:

[0011]

[0012] The formula for converting the resistance value R of a platinum resistance thermometer is:

[0013] R = R Pt0 (1+Tt)

[0014] Where R Pt0 The value of the platinum resistance is t at 0℃, and T is the temperature coefficient of the platinum resistance, which is given by the manufacturer and is 3850ppm / ℃. Substituting these values ​​into the platinum resistance conversion formula will give you the measured temperature value t.

[0015] The beneficial effects of this invention are that it has the calibration and traceability function of platinum resistance thermometer and subsequent analog signal acquisition circuit board, without the need to disassemble the components, eliminating the drift of temperature measurement results caused by performance changes due to aging, adopting the four-wire connection method of platinum resistance thermometer, supporting the constant current source excitation temperature measurement method, which can eliminate the influence of wire resistance and thermoelectric potential on the measurement results, thereby realizing temperature measurement that can be applied to long service life, high resolution, and high accuracy scenarios. Attached image description:

[0016] Figure 1 This is a schematic diagram of the longitudinal section of the mechanical structure of a traceable temperature measurement probe.

[0017] Figure 2 This is a schematic diagram of the temperature measurement circuit structure when using this invention for temperature calibration and traceability.

[0018] Figure 3 This is a circuit structure model diagram of the flexible heating element used for temperature calibration and traceability in accordance with the present invention.

[0019] Figure 4 This diagram illustrates the phase transition characteristics observed in temperature data collected by a platinum resistance thermometer. Detailed implementation method:

[0020] According to the traceable temperature measurement probe structure described in the instruction manual, the structure consists of a probe mechanical structure, a phase change material, a flexible heating element, and a platinum resistance thermometer. The phase change material is encapsulated in a hollow cylinder on the probe mechanical structure. The flexible heating element is attached to the outer surface of the hollow cylinder on the probe mechanical structure and is connected to a power source for heating via two wires. The platinum resistance thermometer is placed in a groove directly below the hollow cylinder on the probe mechanical structure and uses a four-wire method for temperature measurement.

[0021] The phase change material is selected based on the actual temperature measurement range required. For example, if the design is to measure the temperature of a system with a temperature range of 10℃ to 28℃, then according to the fixed point definition in the International Temperature Scale ITS-90, gallium is selected as the phase change material encapsulated in this temperature measurement probe, with a phase change temperature of 29.76℃. When using this invention for normal temperature measurement, the phase change temperature of the phase change material is slightly higher than the temperature range of the measured system, but the measurement results are not affected. When using this invention for temperature traceability calibration, the phase change material is heated by a constant voltage across the heating element. The temperature data collected by the platinum resistance thermometer exhibits phase change characteristics, and the temperature measured at this time is calibrated as the phase change temperature of the phase change material. This achieves calibration of the platinum resistance thermometer and the subsequent analog signal acquisition circuit without disassembling the components.

Claims

1. A method for temperature traceability calibration of a traceable temperature measurement probe structure, wherein the traceable temperature measurement probe structure comprises a probe mechanical structure, a phase change material, a flexible heating element, and a platinum resistance thermometer; characterized in that: The phase change material is encapsulated in a hollow cylinder on the probe's mechanical structure; a flexible heating element is attached to the outer surface of the hollow cylinder on the probe's mechanical structure, and the flexible heating element is connected to a power source through two wires for heating; a platinum resistance thermometer is placed in a groove directly below the hollow cylinder on the probe's mechanical structure, and a four-wire method is used for temperature measurement. The steps are as follows: First, a phase change material closest to the actual temperature measurement range is selected from the definition of the international temperature scale and encapsulated within a hollow cylinder on the probe's mechanical structure. Then, using a four-wire platinum resistance thermometer method, a constant current excitation I is applied to the platinum resistance thermometer through a set of wires. S The voltage U across the platinum resistance thermometer is measured using another set of wires. R Then, a constant voltage U is provided to the flexible heating element to heat the phase change material; finally, the temperature value t is calculated based on the voltage data collected across the platinum resistance thermometer, and the temperature measurement value is calibrated using the phase change characteristics of the phase change material; the specific temperature traceability calibration method is as follows: Before installing and using this temperature measurement probe, the phase change material closest to the definition of the international temperature scale should be selected according to the actual temperature measurement range of the application, and it should be encapsulated in the hollow cylinder of the probe's mechanical structure. Constant current source I S The platinum resistance is excited by applying a voltage U across its terminals using another set of wires on the platinum resistance. R The formula for calculating the resistance value of a platinum resistance thermometer is as follows: The formula for converting the resistance value R of a platinum resistance thermometer is: R=R Pt0 (1+Tt) Where R Pt0 Let T be the resistance value of the platinum resistance at 0℃, and T be the temperature coefficient of the platinum resistance. Substituting these values ​​into the platinum resistance conversion formula will yield the measured temperature value t. A constant voltage U is provided to the flexible heating element to heat the phase change material. When the temperature data collected by the platinum resistance thermometer shows a sudden slowdown in the heating rate, the measured temperature t at this time is calibrated as the phase change temperature T0, thus completing the temperature traceability calibration of the platinum resistance thermometer and subsequent temperature measurement electronics system.

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