CN102539019A - Temperature measurement and calibration platform in space vacuum environment - Google Patents

Abstract

The temperature measurement and calibration platform in the space vacuum environment is conducive to the simultaneous calibration of contact temperature measurement and non-contact temperature measurement, so as to serve the thermal vacuum and thermal balance tests of spacecraft such as satellites and spacecraft, including constant temperature tanks. A twin vacuum chamber is arranged in the groove, and the twin vacuum chamber includes a first vacuum chamber and a second vacuum chamber, and the first vacuum chamber and the second vacuum chamber are connected to the vacuum extraction device through a tee, and the first vacuum chamber is connected to the vacuum extraction device. 1. A standard thermometer sensor is arranged on the outer wall of the vacuum chamber and the outer wall of the second vacuum chamber, and the standard thermometer sensor is connected to a temperature secondary instrument; a laser is arranged in the vacuum chamber of the first vacuum chamber. The optical path reflection device is used to calibrate the non-contact temperature measurement system based on tunable diode laser absorption spectroscopy technology; the vacuum chamber of the second vacuum chamber is used to accommodate the temperature sensor to calibrate the contact measurement system using the temperature sensor. temperature system.

Description

Temperature measurement and calibration platform in space vacuum environment

technical field

The invention relates to a temperature measurement and calibration technology in a vacuum environment, in particular to a temperature measurement and calibration platform in a space vacuum environment. The use of the platform is conducive to solving the traceability problem of temperature measurement in vacuum, and realizes the simultaneous calibration of contact temperature measurement and non-contact temperature measurement, thereby serving the thermal vacuum and thermal balance tests of spacecraft such as satellites and spaceships.

Background technique

In order to verify the correctness of satellite thermal design and ensure the reliable operation of satellites in space orbit, space thermal environment simulation experiments must be carried out in the process of satellite development. The simulated space thermal environment on the ground is the basic condition for realizing the thermal test. In the thermal vacuum test, the temperature of relevant parts is one of the core parameters that need to be accurately measured. According to the location of the temperature measuring point, it can be divided into two parts: spacecraft temperature and experimental equipment temperature. At present, the temperature measurement of these parts is mainly the T-type copper-constantan thermocouple system, which is compared with platinum resistance and thermistor. In order to ensure the accuracy and traceability of temperature measurement, it is necessary to regularly calibrate the temperature measurement equipment. At present, temperature calibration is mainly carried out under normal pressure. With the development of aerospace technology and aircraft technology, the vacuum environment experiment, especially the spacecraft vacuum heat test, has become a very important experimental verification work, and the measurement of some basic parameters in the vacuum environment, especially the temperature measurement, has become the focus of the above research. key testing techniques. But so far, the temperature measurement in the spacecraft vacuum thermal test basically adopts the traditional contact temperature measurement technology, in which the thermocouple temperature measurement system is widely used, but with the development of aerospace science and technology, the traditional thermocouple measurement Temperature technology is increasingly unable to meet the needs of spacecraft vacuum thermal tests. For example, the thermoelectric potential signal is very small. When the signal acquisition and processing unit is installed outside the vacuum chamber, and the thermocouple cable connecting the measurement point and the signal processing unit is relatively long, the noise will be reduced. It will have an adverse effect on high-precision measurement. At the same time, because the temperature field of the vacuum thermal test is relatively complex, if the materials and processes of the measurement circuit are not properly processed, there will be interference from additional thermoelectric potentials; secondly, the vacuum thermal test of the spacecraft The number of thermocouples required in the test is very large, which not only brings difficulties to the experiment, but also reduces the accuracy of temperature measurement due to the heat loss of the thermocouple wires; again, from a physical point of view, thermocouples are used to measure temperature in a high vacuum environment. There are many problems with temperature. For example, in the case of high pressure, there are three main heat transfer methods: convection, heat conduction and radiation. However, when the pressure is close to the vacuum state, the effects of convection and heat conduction basically do not exist. At this time, the main effect of heating the workpiece and thermocouple is radiation, which reflects molecular rotation (corresponding to the rotation temperature) and vibration (corresponding to the vibration temperature). The thermal motion of the thermocouple, and the calibration of the thermocouple is generally carried out under normal pressure, so the calibrated temperature is the translational temperature of the molecule’s thermal motion, that is, the classical thermodynamic temperature. However, the above phenomenon shows that there is an unpredictable problem when using a thermocouple calibrated under normal pressure to measure the temperature of the vacuum environment. Therefore, the development of advanced, accurate, and effective temperature measurement technology has a clear, long-term, and significant civilian and military application background, which can provide effective technical approaches and engineering data for solving spacecraft vacuum thermal tests. In the ground-simulated space thermal environment test, the location of the temperature measuring points of the relevant parts can be divided into two parts: the temperature of the spacecraft and the temperature of the experimental equipment. At present, the temperature measurement of these parts is mainly carried out by temperature sensors, and the T-type copper-constantan thermocouple system is mainly used, and platinum resistance and thermistor are used for comparison. In the space thermal environment simulation experiment, thermocouples, platinum resistors and thermistors are mainly used as sensors for temperature measurement, and their calibration and traceability are all realized under normal pressure. However, in a vacuum environment, the material properties of the temperature sensor and the heat transfer process change, and the temperature field distribution of the thermal vacuum test is very complicated. Therefore, in order to ensure the accuracy of temperature measurement, the space temperature measurement and calibration technology needs further research. TDLAS technology (Tunable Diode Laser Absorption Spectroscopy, tunable diode laser absorption spectroscopy technology) is a kind of spectroscopy remote sensing technology, mainly used to measure the temperature and concentration of gases, and is the development of the current online detection technology of trace gases and polluting gases Direction and technical mainstream. TDLAS technology has the advantages of strong selectivity, high sensitivity, high spectral resolution, and system versatility, and can realize high-precision online measurement of gas temperature and concentration. Although TDLAS technology has made significant progress in the measurement of gas temperature and concentration, and realized high-precision online measurement of gas temperature and concentration in various environments, it is regrettable that the current research on TDLAS technology is mainly aimed at specific engineering applications. The pressure range of its research is generally concentrated in the range of 0.1kPa to 1000kPa. Few researchers try to measure the temperature and concentration of gas in a high vacuum environment. The main reasons for this are the following two points: First, the current TDLAS technology is mainly For specific engineering applications, and engineering applications generally rarely involve extremely low pressure conditions; second, TDLAS technology obtains the temperature and concentration of the gas by analyzing the absorption of the gas to the laser, but in a vacuum environment, the gas per unit volume The number of molecules is so small that the absorption signal is very weak and unfavorable for experimental measurement. However, in recent years, with the advancement of the experimental level, especially the application of optical resonant cavity technology, it has become possible to measure the temperature and concentration of gases under extremely low pressure conditions.

Contents of the invention

Aiming at the defects or deficiencies in the prior art, the invention provides a temperature measurement and calibration platform in a space vacuum environment. The use of the platform is conducive to solving the traceability problem of temperature measurement in vacuum, and realizes the simultaneous calibration of contact temperature measurement and non-contact temperature measurement, thereby serving the thermal vacuum and thermal balance tests of spacecraft such as satellites and spaceships.

Technical scheme of the present invention is as follows:

The temperature measurement and calibration platform under the space vacuum environment is characterized in that it includes a constant temperature tank, and the twin vacuum chambers are arranged in the constant temperature tank, and the twin vacuum chambers include a first vacuum chamber and a second vacuum chamber. The first vacuum chamber and the second vacuum chamber are connected to the vacuum extraction device through a tee, and a standard thermometer sensor is arranged on the outer wall of the first vacuum chamber and the outer wall of the second vacuum chamber. The thermometer sensor is connected to the temperature secondary instrument; the vacuum chamber of the first vacuum chamber is provided with a laser light path reflection device for calibrating a non-contact temperature measurement system based on tunable diode laser absorption spectroscopy technology; the second vacuum The vacuum cavity of the cavity is used to accommodate the temperature sensor to calibrate the contact temperature measurement system using the temperature sensor.

The laser light path reflection device includes a mirror surface located at the upper end of the cavity of the first vacuum chamber and a mirror surface located at the lower end of the cavity of the first vacuum cavity, and the upper end of the cavity of the first vacuum cavity is provided with an optical fiber entrance for laser input And the fiber exit of the laser output after a certain number of reflections.

The temperature sensor is installed on the inner wall of the second vacuum cavity, and the temperature sensor is connected with a temperature secondary instrument.

The constant temperature tank adopts liquid nitrogen tank, alcohol tank, water tank or oil tank.

The vacuum extraction device includes a mechanical pump, a molecular pump, a gate valve and a solenoid valve, the mechanical pump, the molecular pump and the gate valve are connected in sequence, the gate valve is connected to the twin vacuum chambers through a tee, and the The solenoid valve is connected in parallel with the molecular pump and the gate valve.

Both the first vacuum chamber and the second vacuum chamber are made of red copper.

An annular space is provided on the outer wall of the first vacuum chamber and the outer wall of the second vacuum chamber, the bottom of the annular space is connected to the outer wall, the upper part of the annular space communicates with the atmosphere, the A standard thermometer sensor is located within the annular space.

The outlet of the optical fiber is connected to a photodetector, and the photodetector is connected to a data acquisition and processing device; the inlet of the optical fiber is connected to a laser, and the laser is connected to a laser control unit, and the laser control unit receives a combination of a signal generator and a lock-in amplifier. Signal.

Technical effect of the present invention is as follows:

The invention relates to temperature measurement and calibration technology in a vacuum environment, can solve the problem of traceability of temperature measurement in vacuum, and realize simultaneous calibration of contact temperature measurement and non-contact temperature measurement. The inventor has carried out the research on temperature measurement and calibration technology of temperature sensor technology in vacuum, studied the heat transfer mechanism in vacuum environment, and established a set of temperature calibration platform in vacuum environment, which provides for the development, test and calibration of space temperature measurement devices. Assure. At the same time, based on Tunable Diode Laser Absorption Spectroscopy (TDLAS), the temperature of trace gases (air or specific gases, such as CO ₂ ) in a vacuum environment is measured by TDLAS technology to verify the reliability and reliability of traditional temperature sensor measurement technology. Accuracy, and on this basis, develop a new, high-precision, vacuum environment temperature measurement technology based on TDLAS technology, so that the two methods can be compared and complemented. The completion of this project intends to solve the problem of the large difference between the measurement results of the temperature sensor under normal pressure and vacuum, and directly serve the thermal vacuum and thermal balance tests of satellites, spacecraft and other spacecraft.

In the ground-simulated space thermal environment test, the location of the temperature measuring points of the relevant parts can be divided into two parts: the temperature of the spacecraft and the temperature of the experimental equipment. At present, the temperature measurement of these parts is mainly carried out by temperature sensors, and the T-type copper-constantan thermocouple system is mainly used, and the platinum resistance and thermistor are used for comparison. TDLAS technology (Tunable Diode Laser Absorption Spectroscopy) has the advantages of strong selectivity, high sensitivity, high spectral resolution, and system versatility. It can realize high-precision online measurement of gas temperature and concentration, and belongs to non-contact temperature measurement. These two methods are widely used due to their unique advantages, but there are also traceability problems in vacuum applications. In order to solve the problem of traceability of these two methods in vacuum, and at the same time ensure that various environmental factors are consistent during the calibration process and do not interfere with each other. A twin vacuum chamber structure is designed to solve this problem. The twin vacuum chambers can not only work together, but also can be disassembled to work separately. Through this vacuum structure, the same calibration environment can be provided without interfering with each other. TDLAS technology (Tunable Diode Laser Absorption Spectroscopy) is a kind of spectroscopic remote sensing technology, which is mainly used to measure the temperature and concentration of gas. TDLAS technology has the advantages of strong selectivity, high sensitivity, high spectral resolution, and system versatility. , can realize high-precision online measurement of gas temperature and concentration. The temperature sensor is easy to change its material properties in a vacuum environment, which affects its measurement. The TDLAS temperature measurement method uses optical means, which does not have this problem. Field distribution measurement.

Description of drawings

Fig. 1 is a structural schematic diagram of a temperature measurement and calibration platform for implementing the present invention in a space vacuum environment.

The markers in the figure are listed as follows:

10-signal generator; 11-lock-in amplifier; 12-laser control unit; 13-data acquisition and processing device; 14-temperature secondary instrument; 15-photoelectric detector; 16-laser; 17-constant temperature bath; 18-ring Space; 19-the vacuum chamber of the second vacuum chamber; 20-the vacuum chamber of the first vacuum chamber; 21-the laser light path; 22-the reflection mirror at the lower end of the first vacuum chamber; 23-the first vacuum chamber Reflecting mirror at the upper end of the cavity; 24-fiber optic inlet; 25-fiber optic outlet; 26-tee; 27-gate valve; 28-molecular pump; 29-mechanical pump; 30-solenoid valve; - the first vacuum chamber; 33 - the second vacuum chamber; 34 - the temperature sensor.

Detailed ways

Below in conjunction with accompanying drawing (Fig. 1) the present invention is described.

Fig. 1 is a structural schematic diagram of a temperature measurement and calibration platform for implementing the present invention in a space vacuum environment. As shown in Figure 1, the temperature measurement and calibration platform under the space vacuum environment includes a constant temperature tank 17, and the twin vacuum chambers (i.e., the vacuum chambers of the first vacuum chamber bodies connected by a tee 26) are arranged in the said constant temperature tank. 20 and the vacuum chamber 19 of the second vacuum chamber), the twin vacuum chambers include the first vacuum chamber 32 and the second vacuum chamber 33, and the first vacuum chamber 32 and the second vacuum chamber 33 pass through three A vacuum extraction device is connected through 26, and a standard thermometer sensor 31 is arranged on the outer wall of the first vacuum chamber 32 and the outer wall of the second vacuum chamber 33, and the standard thermometer sensor 31 is connected to the temperature secondary instrument 14 ; The vacuum cavity 20 of the first vacuum cavity is provided with a laser light path reflection device for calibrating a non-contact temperature measurement system based on tunable diode laser absorption spectroscopy technology; the vacuum cavity 19 of the second vacuum cavity It is used to accommodate the temperature sensor 34 to calibrate the contact temperature measurement system using the temperature sensor 34 . The temperature sensor 34 is also called a temperature sensor to be tested or a thermometer to be tested. The laser light path reflection device includes a mirror surface 23 positioned at the upper end of the first vacuum chamber cavity and a mirror surface 22 positioned at the lower end of the first vacuum chamber cavity, the upper end of the first vacuum chamber cavity is provided with a laser input An optical fiber entrance 24 and an optical fiber exit 25 for outputting laser light after a certain number of reflections. The temperature sensor 34 is installed on the inner wall of the second vacuum cavity 33 , and the temperature sensor 34 is connected to the temperature secondary instrument 14 . Described constant temperature tank 17 adopts liquid nitrogen tank, alcohol tank, water tank or oil tank. The vacuum extraction device includes a mechanical pump 29, a molecular pump 28, a gate valve 27 and a solenoid valve 30, the mechanical pump 29, the molecular pump 28 and the gate valve 27 are connected in sequence, and the gate valve 27 is connected through a tee 26 The twin vacuum chambers are connected, and the solenoid valve 30 is connected in parallel with the molecular pump 28 and the gate valve 27 . Both the first vacuum chamber 32 and the second vacuum chamber 33 are made of red copper. An annular space 18 is provided on the outer wall of the first vacuum chamber and the outer wall of the second vacuum chamber, the bottom of the annular space 18 is connected to the outer wall, and the upper part of the annular space 18 communicates with the atmosphere , the standard thermometer sensor 31 is located in the annular space 18 . The optical fiber outlet 25 is connected to the photodetector 15, and the photodetector 15 is connected to the data acquisition and processing device 13; the optical fiber inlet 24 is connected to the laser 16, and the laser 16 is connected to the laser control unit 12, and the laser control unit 12 receives Mixed signal of signal generator 10 and lock-in amplifier 11.

With the development of science and technology, the production and manufacture of various precision products and special scientific experiments require a specific working environment. The prerequisite for thermal sensor verification is that the constant temperature field must meet the requirements, so the level of constant temperature control accuracy has become the actual verification. one of the indispensable conditions. The constant temperature bath is the ambient temperature test equipment that must be used in temperature testing and temperature control, especially in the verification of temperature instruments and meters. It is used to provide a constant temperature field under different temperature conditions. The constant temperature bath has been widely used in the temperature measurement and calibration work, and the technical performance of the constant temperature bath determines the quality of the measurement and calibration work. According to the requirements of the technical performance test specifications of the constant temperature bath, the main technical indicators of the general constant temperature bath are temperature fluctuation, temperature uniformity and indication deviation. At present, the constant temperature tanks used for verification mainly include: alcohol low temperature tank, water constant temperature tank, and oil constant temperature tank. They are named after different constant temperature media. Among them, the alcohol low-temperature tank is used to provide a temperature field of -100°C to 5°C; the water constant temperature tank is used to provide a temperature field of 5°C to 95°C; the oil constant temperature tank is used to provide a temperature field of 95°C to 300°C . The medium of the oil constant temperature bath is usually edible oil, cylinder oil, silicone oil, etc. For the temperature below -100°C, liquid nitrogen or liquid helium is usually used as the medium. In our study, the design of the thermostatic bath system includes the selection of a suitable range of thermostatic baths, the design of the thermostatic bath cover and the fixing mechanism of the vacuum system. According to "JJG 229-1998 Industrial Platinum and Copper Thermal Resistance Verification Regulations", industrial platinum resistors only need to verify the 0°C and 100°C points, according to "JJG 368-2000 Working Copper-Cu-Nickel Thermocouple Verification Regulations", thermocouples need verification liquid Nitrogen temperature point, -79°C, 100°C, 200°C, 300°C, the calibration of the thermistor is calibrated according to its range every 10°C as an interval, the general range is -50°C to 200°C.

The principle of TDLAS technology measurement is that when a monochromatic laser beam passes through a gas medium, the laser intensity changes due to gas absorption. The laser intensity variation follows the Beer-Lambert law. Due to the extremely low pressure of the TDLAS temperature measurement technology in a vacuum environment, in order to improve the accuracy and sensitivity of temperature measurement, the wavelength modulation technology is used for temperature measurement in the experiment. After the low-frequency sawtooth wave scanning signal is mixed with the high-frequency sinusoidal modulation signal, it is loaded on the input end of the tunable laser, and the wavelength of the driving laser is scanned and modulated near the absorption line. The output laser is collimated by the lens and enters the gas medium through the optical fiber ( Vacuum chamber), the transmitted laser signal is sent out of the vacuum chamber by the optical fiber and converted into an electrical signal by the photodetector, one way is input into the lock-in amplifier for harmonic detection, and one way is input into the data acquisition card to monitor the change of laser intensity during the measurement process .

In the ground-simulated space thermal environment test, the location of the temperature measuring points of the relevant parts can be divided into two parts: the temperature of the spacecraft and the temperature of the experimental equipment. At present, the temperature measurement of these parts is mainly carried out by temperature sensors, and the T-type copper-constantan thermocouple system is mainly used, and the platinum resistance and thermistor are used for comparison. In the space thermal environment simulation experiment, thermocouples, platinum resistors and thermistors are mainly used as sensors for temperature measurement, all of which belong to contact temperature measurement. DLAS technology (TunableDiode Laser Absorption Spectroscopy) has the advantages of strong selectivity, high sensitivity, high spectral resolution, and system versatility. It can realize high-precision online measurement of gas temperature and concentration, and belongs to non-contact temperature measurement. These two methods are widely used due to their unique advantages, but there are also traceability problems in vacuum applications. In order to solve the problem of traceability of these two methods in vacuum, and at the same time ensure that various environmental factors are consistent during the calibration process and do not interfere with each other. A twin vacuum chamber structure is designed to solve this problem. The twin vacuum chambers can not only work together, but also can be disassembled to work separately. Through this vacuum structure, the same calibration environment can be provided without interfering with each other.

It is pointed out here that the above description is helpful for those skilled in the art to understand the present invention, but does not limit the protection scope of the present invention. Any equivalent replacement, modification and improvement and/or simplified implementation of the above descriptions without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims (8)

1. The temperature measurement and calibration platform under the space vacuum environment is characterized in that it comprises a constant temperature tank, and the twin vacuum chambers are arranged in the constant temperature tank, and the twin vacuum chambers include the first vacuum chamber and the second vacuum chamber, The first vacuum chamber and the second vacuum chamber are connected to the vacuum extraction device through a tee, and standard thermometer sensors are arranged on the outer wall of the first vacuum chamber and the outer wall of the second vacuum chamber, so The standard thermometer sensor is connected to the temperature secondary instrument; the vacuum cavity of the first vacuum cavity is provided with a laser optical path reflection device, which is used to calibrate the non-contact temperature measurement system based on tunable diode laser absorption spectroscopy technology; the first vacuum cavity 2. The vacuum chamber of the vacuum chamber is used to accommodate the temperature sensor to calibrate the contact temperature measurement system using the temperature sensor. 2. The temperature measurement and calibration platform under the space vacuum environment according to claim 1, characterized in that, the laser optical path reflection device comprises a reflector at the upper end of the first vacuum cavity and a reflector at the upper end of the first vacuum cavity. The reflective mirror surface at the lower end of the cavity, the upper end of the cavity of the first vacuum cavity is provided with an optical fiber inlet for laser input and an optical fiber output for laser output after a certain number of reflections. 3. The temperature measurement and calibration platform under a space vacuum environment according to claim 1, wherein the temperature sensor is installed on the inner wall of the second vacuum cavity, and the temperature sensor is connected to a temperature secondary instrument. 4. The temperature measurement and calibration platform under the space vacuum environment according to claim 1, characterized in that, the constant temperature tank adopts liquid nitrogen tank, alcohol tank, water tank or oil tank. 5. the temperature measurement and calibration platform under the vacuum environment of space according to claim 1, is characterized in that, described vacuum pumping device comprises mechanical pump, molecular pump, gate valve and solenoid valve, and described mechanical pump, molecular pump It is sequentially connected with the gate valve, the gate valve is connected with the twin vacuum chambers through a tee, and the electromagnetic valve is connected in parallel with the molecular pump and gate valve. 6. The temperature measurement and calibration platform under a space vacuum environment according to claim 1, characterized in that, both the first vacuum chamber and the second vacuum chamber are made of red copper. 7. The temperature measurement and calibration platform under the vacuum environment of space according to claim 1, wherein an annular space is arranged on the outer wall of the first vacuum chamber and the outer wall of the second vacuum chamber , the bottom of the annular space is connected to the outer wall, the upper part of the annular space is connected to the atmosphere, and the standard thermometer sensor is located in the annular space. 8. The temperature measurement and calibration platform under a space vacuum environment according to claim 2, wherein the optical fiber outlet is connected to a photodetector, and the photodetector is connected to a data acquisition and processing device; the optical fiber inlet is connected to a laser , the laser is connected to a laser control unit, and the laser control unit receives a mixed signal from a signal generator and a lock-in amplifier.

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