CN103616080A - Portable optical fiber radiation thermodetector and measuring method thereof - Google Patents

Abstract

The invention discloses a portable optical fiber radiation thermometer and a measuring method thereof, belonging to the field of high temperature measurement. The thermometer includes high-power fiber optic coupler, energy transmission fiber, photoelectric detector, preamplifier module, AD sampling module, signal processing module, display module, keyboard input, digital-to-analog conversion and 4-20mA current loop. The high-power fiber optic coupler couples the wide-band thermal radiation energy, and transmits the optical signal to the photodetector through the energy-transmitting optical fiber to convert the optical signal into an electrical signal. The electrical signal is sampled by AD, and the signal processing module uses a curve fitting algorithm to analyze the sampled signal. , and finally the corresponding temperature value can be calculated by calibration. The structure of the portable optical fiber radiation thermometer of the invention is very suitable for measuring the thermal field of a crystal furnace, and is simple, convenient and very practical.

Description

Portable fiber optic radiation thermometer and its measuring method

technical field

The invention relates to a measuring instrument for the thermal field of a crystal furnace, in particular to a portable optical fiber type radiation thermometer for measuring the thermal field of a crystal furnace and a measuring method thereof.

Background technique

Radiation thermometers are often used in high temperature measurement in the fields of chemical industry, energy, metallurgy and scientific research. For the measurement range above 1800°C, the radiation thermometer calculates the corresponding temperature by means of non-contact measurement of the energy of infrared thermal radiation. The upper limit of measurement is not limited by the temperature resistance of the temperature sensing element, so there is no limit to the maximum measurable temperature in principle. Therefore, it has been widely used in the industrial field. Due to the advantages of high resolution, high temperature measurement accuracy and good repeatability, radiation thermometers are widely used in high temperature measurement. For example, the MS/MI series of infrared thermometers from Saiten, Germany, have a system accuracy of 0.5% of the measured value in the range of 1500°C to 2500°C, a repeatability of 0.1% of the measured temperature value + 1K, and a temperature resolution of 0.1°C. The high-precision infrared thermometer represented by this type is based on the basic law of black body radiation. It measures the corresponding relationship between the radiation energy of a specific band and the corresponding temperature, and corrects the emissivity of the corresponding material to calculate the corresponding temperature. temperature. However, these instruments require sophisticated optical lenses and complex optical signal processing devices, so it is difficult to make compact and inexpensive measuring instruments.

Traditional radiation thermometers generally have large structures, complex optical paths, are sensitive to environmental influences, and are expensive. Therefore, there is an urgent need for a simpler, more compact, and more stable temperature measurement system. In addition, most radiation thermometers are a technology based on photoelectric precision temperature measurement, so photoelectric detectors are key components in precision temperature measurement technology. The earliest photoelectric components were mostly photomultiplier tubes and phototubes. The application of such electric vacuum devices required high voltages of several hundred volts to several thousand volts, and the spectral responses were in the range of visible light to near-infrared. Later, photodetectors with light weight and small size appeared one after another. Moreover, it has been greatly improved and improved in terms of stability, sensitivity, spectral response range, and passband width, and soon occupied an irreplaceable position in engineering applications.

Contents of the invention

The object of the present invention is to provide a portable fiber optic radiation thermometer, which is a measuring instrument capable of detecting ultrahigh temperatures. Another object of the present invention is to provide a method for temperature measurement using the portable fiber optic radiation thermometer.

The technical scheme that the present invention adopts for solving its technical problem is:

The portable fiber optic radiation thermometer consists of an optical system and a circuit system. module, signal processing module, display module, key input, digital-to-analog conversion module and current loop, wherein, the photodetector, preamplifier, AD sampling module and signal processing module are connected in sequence, and the display module, key input and The digital-to-analog conversion module is respectively connected to the signal processing module, the current loop is connected to the digital-to-analog conversion module; the output end of the energy transmission optical fiber is connected to the input end of the photodetector.

Wherein, the current loop adopts a 4-20mA current loop. The photodetector is an InGaAs photodiode in a standard FC/PC package. The preamp uses a logarithmic amplifier. The AD sampling module uses a 24-bit high-precision sampling chip.

In order to utilize the above-mentioned portable optical fiber radiation thermometer to measure the temperature of the crystal furnace, the measuring method method of the present invention comprises the following steps: at first the high-power optical fiber coupler is installed on the observation hole of the crystal furnace, and the switch on the observation hole is opened, then The thermal radiation energy in the furnace is converged to the end face of the energy-transmitting optical fiber through the high-power optical fiber coupler; the energy is then transmitted to the photodetector through the energy-transmitting optical fiber, and then the radiant energy is converted into a corresponding current signal by the photodetector; The signal is I/V converted and amplified by the preamplifier module, and the obtained voltage signal is sampled with high precision by the AD sampling module; after the analog signal is converted into a digital signal, the sample is analyzed by the signal processing module through a curve fitting algorithm Finally, the corresponding temperature value is calculated by calibration and output through the display module; the digital signal can also be transferred to the computer through a 4-20mA current loop after digital-to-analog conversion and processed by the virtual instrument Labview; when testing different temperature ranges , the algorithm parameters in the signal processing module can be modified by key input, which is convenient for accurate measurement in different temperature ranges.

The invention has the following beneficial effects: (1) The high-power optical fiber coupler adopted has an ultra-wide coupling wavelength range, and has extremely high coupling efficiency in the range of 0.4 μm to 2.5 μm, and can be directly plugged in, repeatable and interchangeable (2) The energy transmission fiber with a core of 600μm is used, and the energy transmission loss is extremely low. There is a layer of metal armor inside the outer sheath of the optical fiber, which protects the inner fiber core and has the function of resisting strong pressure and stretching. Using optical fiber to transmit energy can reduce the difficulty of installing and protecting the thermometer, and make the thermometer flexible and miniaturized; (3) the photodetector of the present invention uses a standard FC/PC packaged InGaAs photodiode and sensor The optical fiber connection is very convenient, and the use of optical fiber can not be affected by electromagnetic interference, so that the photodetector is far away from high-temperature objects, ensuring the stability of long-term online work. (4) The highly integrated circuit system is very convenient to install on the console of the crystal furnace, which is convenient for the operator to observe; (5) The present invention uses a precise logarithmic amplifier to perform I/V conversion on weak signals, and a 24-bit sampling chip to perform I/V conversion. Sampling ensures the measurement performance of the entire instrument: the measurement range is 800-2200°C, the measurement accuracy is ±0.2%, the resolution is 1°C, and the response speed is less than 1ms.

Description of drawings

Fig. 1 is the system block diagram of portable optical fiber radiation thermometer of the present invention;

Fig. 2 is the structural diagram of portable optical fiber radiation thermometer of the present invention;

Fig. 3 is a flow chart of software processing of signals in the measurement method of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and implementation methods.

As shown in Figure 1, the optical system in the device of the present invention is composed of a high-power fiber coupler 1 connected to an energy-transmitting fiber 2, wherein the coupling wavelength range of the high-power fiber coupler 1 is 0.4 μm to 2.5 μm, and the diameter of its coupling lens is 25 mm. The energy-transmitting optical fiber 2 uses a quartz optical fiber with a core of 600 μm; the circuit system consists of a photodetector 3, a preamplifier 4, an AD sampling module 5, a signal processing module 6, a display module 7, key input 8, and a digital-to-analog conversion module 9 and 4-20mA current loop 10, all modules are integrated on an electronic box. The optical system and the circuit system are independent, which can completely avoid the interference of the temperature measurement site on the temperature measurement of the instrument. Wherein, the preamplifier 4 uses a logarithmic amplifier to process weak signals, which can accurately convert weak current signals into voltage signals. The AD sampling module 5 adopts a 24-bit high-precision sampling chip, which can accurately sample the obtained analog signal during work. The photodetector 3 adopts a standard FC/PC packaged InGaAs photodiode. The connection between the optical system and the circuit system is connected with the input end of the photodetector 3 through the output end of the energy transmission fiber 2; FIG. 2 is a schematic diagram of the mechanical structure of the present invention.

The implementation method of receiving radiant energy and measuring temperature by using an optical system will be described with reference to FIG. 1 and FIG. 2 . First install the high-power optical fiber coupler 1 on the observation hole of the crystal furnace, turn on the switch on the observation hole, then the heat radiation energy in the furnace will converge to the end face of the energy-transmitting optical fiber 2 through the high-power optical fiber coupler 1; It is then transmitted to the photodetector 3 through the energy-transmitting optical fiber 2, and then the radiant energy is converted into a corresponding current signal by the photodetector 3; the current signal is subjected to I/V conversion and amplification through the pre-amplification module 4, and the obtained voltage signal is obtained by The AD sampling module 5 performs high-precision sampling; after the analog signal is converted into a digital signal, the corresponding temperature value is calculated by the signal processing module 6 through a curve fitting algorithm and output through the display module 7; the digital signal can also be passed through 4-20mA The current loop 10 is transmitted to the computer for processing through the virtual instrument Labview, the 4-20mA current loop 10 can realize online temperature monitoring, and the virtual instrument Labview can draw dynamic curves and save the temperature values at each time node. . When testing different temperature ranges, the algorithm parameters in the signal processing module 6 can be modified by key input 8, so as to facilitate accurate measurement in different temperature ranges.

The signal processing flow of the signal processing module in the thermometer is described in conjunction with FIG. 3 . After the instrument is turned on, the signal processing module 6 first initializes the AD sampling module 5 and the display module 7, and then the AD sampling module 5 is in a continuous sampling working state, and the display module 7 outputs the current temperature value. After the switch of the observation window is turned on, if a change in the voltage signal is detected, the AD sampling module 5 will transmit the newly sampled digital signal to the signal processing module 6 for calculation, and output a new temperature value through the display module 7 .

If the temperature measurement system can be applied to accurately measure the temperature on site, it must be calibrated to correctly display the temperature of the measured target. The polynomial curve fitting method based on the least square method adopted in the present invention measures the temperatures of multiple points and obtains a temperature trend curve through fitting. The calibration method of the present invention is to use a standard black body furnace to replace the measured target, and to collect voltage signals at different temperatures. Directly fit the relationship between the temperature and the number of voltage sampling codes with a polynomial curve of degree 6, and then obtain a formula for the temperature and the number of sampling codes: T=a x ⁶ +b x ⁵ +c x ⁴ +d x ³ +e·x ² +f·x+g, where T is the temperature (°C), x is the number of sampling codes, and a, b, c, d, e, f, g are constants. Write the algorithm of this formula into the signal processing module 6, so that the instrument can work normally.

Claims (6)

1. portable fiber-optic Radiation Temperature Measurement Instrument, is comprised of optical system and Circuits System, it is characterized in that: described optical system connects energy-transmission optic fibre by high-power optical fiber coupled device and forms; Described Circuits System comprises photodetector, prime amplifier, AD sampling module, signal processing module, display module, key-press input, D/A converter module and electric current loop, wherein, described photodetector, prime amplifier, AD sampling module are connected successively with signal processing module, described display module, key-press input and D/A converter module are connected with described signal processing module respectively, and described electric current loop is connected with described D/A converter module; The output terminal of described energy-transmission optic fibre is connected with the input end of photodetector.

2. portable fiber-optic Radiation Temperature Measurement Instrument according to claim 1, is characterized in that, described electric current loop adopts 4-20mA electric current loop.

3. portable fiber-optic Radiation Temperature Measurement Instrument according to claim 1, is characterized in that, described photodetector adopts the InGaAs photodiode of standard FC/PC encapsulation.

4. portable fiber-optic Radiation Temperature Measurement Instrument according to claim 1, is characterized in that, described prime amplifier adopts logarithmic amplifier.

5. portable fiber-optic Radiation Temperature Measurement Instrument according to claim 1, is characterized in that, what described AD sampling module adopted is 24 high-precision sampling A/D chip.

6. utilize the measuring method of portable fiber-optic Radiation Temperature Measurement Instrument as claimed in claim 1, it is characterized in that, comprise the following steps: first high-power optical fiber coupled device is installed on the viewport of crystal oven, open the switch on viewport, the heat radiation energy in stove just converges on the end face of energy-transmission optic fibre by high-power optical fiber coupled device so; Energy is transferred on photodetector by energy-transmission optic fibre again, and then emittance converts corresponding current signal to by photodetector; Current signal carries out I/V conversion and amplification through pre-amplifying module, and the voltage signal obtaining is sampled accurately by AD sampling module; Simulating signal converts to after digital signal, and the sampled signal that the Algorithm Analysis through signal processing module by curve obtains, is finally gone out corresponding temperature value and exported by display module by calibrated and calculated; Mode by 4-20mA electric current loop after digital signal also can digital-to-analogue turns is transferred on computer to be processed by virtual instrument Labview; When test different temperatures scope, can to the algorithm parameter in signal processing module, modify by key-press input, the convenient accurate measurement that adapts to different temperatures section.

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