RU2403539C1 - Device for determining spectral emissivity of hot objects - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: in the device the number of spectral bands N is greater than 6. The device includes N independent radiation receivers, N analogue-to-digital converters (ADC), N memory units, N dividers, a synchroniser, as well as a channel for determining temperature of the measured object. The optical input of the radiation receiver in each channel is connected to a beam splitter and the electrical output is connected to the input of the corresponding ADC, whose first output is connected to the first input of the corresponding divider, the second output of the ADC is connected to the input of the corresponding memory unit whose output is connected to the second input of the divider, outputs of the dividers are connected to inputs of a recording device. ^ EFFECT: higher accuracy of measuring spectral emissivity of hot objects. ^ 1 dwg, 2 ex

Description

The invention relates to measuring technique in terms of creating meters of the spectral emissivity of heated bodies and can be used as a device for the operational measurement of the spectral emissivity of metals directly in the workshop during their smelting and subsequent heat treatment.

A device [1] is known that contains an optical system located along the radiation of the object under study, a beam splitter device, three radiation receivers optically coupled to it at three different wavelengths, according to the signals in which the temperature of the object is determined in the device. The device is designed to operate as a pyrometer - a temperature meter and a sensor in an automatic temperature control system of an object.

The advantage of this device using a three-channel radiation registration system for the object under study is that during the measurement process there is no need to make corrections for the emissivity of the measured object, since its processing unit, using the a priori information previously stored in the memory, independently determines the emissivity values in each from spectral channels.

The disadvantage of this device is the small number of spectral channels, as well as the fact that it is designed to operate in the pyrometer mode and does not display the values of spectral emissivity in each channel determined during the measurement process.

A device [2] is known that is closest to the described one, containing two sources of radiation - a “blackbody model”, an optical system, a monochromator, a radiation receiver at the output of a monochromator, a system for amplifying and recording the signal of the receiver, and a channel for determining the integral emissivity of the measured object.

An advantage of the device is the ability to measure spectral emissivity with a minimum step on a wavelength scale determined by the design features of modern monochromators (less than 1 nm).

The disadvantages of such a device include, in addition to large dimensions and weight, a large measurement duration in the range from the minimum (0.3 ... 0.4 μm) to the maximum (1 ... 2 μm) wavelength. This is explained by the fact that the device uses one recording radiation receiver, and the measurement process consists in sequentially projecting onto the receiver a scanning system of the entire studied spectral range from minimum to maximum light wavelength. Such a drawback requires that the temperature of the measured object remains unchanged throughout the entire measurement time, which can be tens of seconds, depending on the speed of the monochromator. Therefore, this device is practically not applicable in workshop conditions, where during casting or when moving an object around the mill, the temperature can noticeably change even in 1 s. At the same time, attempts to carry out such measurements in laboratory conditions, where the temperature of the measured object can be kept constant, are usually accompanied by very large errors, since the emissivity strongly depends not only on the composition, but also on the technology for obtaining the material, heat treatment parameters, heating, etc. etc., and the conditions for preparing the material for measurements in the workshop and in the laboratory are different.

The aim of the invention is to improve the accuracy of measuring the spectral emissivity of heated objects by simultaneously recording radiation from the object in a large number of independent different spectral ranges.

This goal is achieved by the fact that in the device for determining the spectral emissivity of heated objects, containing an optical system located along the radiation of the object under study, a beam splitting device that emits N narrow spectral bands in the radiation spectrum of the object uniformly located over the entire spectral range of the device, the number of spectral ranges N is chosen to be large 6, N independent radiation receivers, N analog-to-digital converters (ADCs), N memory blocks, N are introduced dividing devices, a recording device, a synchronizer, as well as a channel for determining the temperature of the measured object, while the optical input of the radiation receiver in each channel is connected to a beam splitting device, and the electrical output to the input of the corresponding ADC, the first output of which is connected to the first input of the corresponding dividing device , the second output of the ADC is connected to the input of the corresponding memory block, the output of which is connected to the second input of the dividing device, the outputs of the dividing devices are connected s registration to the inputs of the device for determining the temperature sensor channel measured object is in contact with the object, determining the temperature channel output connected to an input of the registration unit, all clock inputs and ADC input channel synchronization detecting the temperature of the measured object connected to the output of the synchronization device.

The block diagram of the device shown in the drawing.

A device for determining the spectral emissivity of heated objects contains an optical system 2 located along the radiation of the studied object 1, a beam splitter 3, N independent radiation receivers PR ₁ -PR _N , represented in the figure by elements 7.1-7.N, N of analog-to-digital ADC converters _1- ADC _N , represented by elements 8.1-8.N, N of the memory blocks of RAM _1- RAM _N , represented by elements 9.1-9.N, N of the dividing devices D ₁ -D _N , represented by elements 10.1-10 in the drawing .N regis device 4, synchronizer 5, as well as a channel for determining the temperature of the measured object 6, while the optical input of the radiation receiver PR _i , where i takes a value from 1 to N, is connected in each channel to a beam splitting device, and the electrical output to the input of the corresponding ADC _i, the first output of which is connected to a first input of a respective divider D _{i, i} of the second ADC output connected to the input of the corresponding RAM memory block _i, the output of which is connected to the second input of divider D _i, outputs fission mouth oystv connected to the inputs of device registration 4, the sensor channel determining the temperature measurement object 6 is in contact with the object 1, the output channel temperature detection connected to the input device registration 4, all clock inputs of ADC _i and the channel clock input detecting the temperature measurement object 6 connected to the outlet sync devices 5.

The drawing does not show the power supply of the elements used. Variants of the standard elements used in the device that make up the block diagram are given in examples of the device.

The device operates as follows. The radiation of object 1, whose energy is determined by the nonlinear characteristics of the emissivity ε (λ) of the object, depending on the wavelength, is perceived by the optical system 2 of the device and is divided by a beam splitter 3 into N streams with wavelengths: λ ₁ - in the first channel for determining the emissivity ε ( λ ₁ ), λ ₂ - in the second channel for determining the emissivity ε (λ ₂ ), λ _N - in the N-th channel for determining the emissivity ε (λ _N ). In each of these channels, the corresponding radiation receiver PR _i (i = 1, 2, 3, ..., N) converts the energy of these radiation streams into a proportional electric signal U (λ _i ). In each channel, the corresponding output signal of the receiver is fed to the input of the analog-to-digital converter of the ADC _i to convert it to a digital code. Next, the output signal of the ADC converter _i goes to one of the inputs of the divider Д _i , the second input of which receives a signal from the RAM _i memory block, where the information from the ADC _i converter about the signal value in this spectral channel from the radiation source - "blackbody model" is preliminarily recorded " The divider D _i finds the ratio of the current signal from the ADC _i converter to the signal from the RAM memory block _i , and then enters the result into the recording device 4.

Conversion to digital code by all ADC _i converters is carried out simultaneously, according to the signal generated by the synchronizer 5. Also, this signal is used to measure the temperature of the object by the channel for determining the temperature of the measured object 6. The result is also recorded in the recording device for subsequent correction if the temperature of the measured object and the temperature of the radiation source - the "black body model", information about which is stored in RAM _i , are not equal to each other.

The output signal of the synchronizer 5, which starts the ADC _i converters and the channel for determining the temperature of the measured object 6, is generated by the operator’s command.

Examples of device implementation.

General data for various implementations of the device:

- range of wavelengths used: λ _min = 0.3 μm, λ _max = 1.15 μm;

- the optical system of the device contains a lens, an eyepiece, a field diaphragm;

- the relative aperture of the lens 1/22;

- focal length of the lens 210 mm;

- the device’s sighting rate is more than 100: 1;

- sighting system - non-parallax;

- a dark point is visible in the field of view of the eyepiece - the hole of the field diaphragm and the region of the measured object around it, which allows you to navigate which part of the surface is measured;

- to minimize the effect of defocusing, the lens allows focusing on the subject;

- the range of working distances from the device to the object 0.6 ... 3 m;

- the design of the eyepiece allows replacing it with a miniature video camera with its own lens (for the convenience of documenting the behavior of the recorded surface in the measurement process);

- device performance is not worse than 20 ms;

- device power supply voltage - 220 V;

- frequency of 50 Hz;

- power consumption less than 50 VA.

Example 1

Elements used:

- optical system - Industar-51 lens;

- a beam splitting device in the form of a diffraction grating of 500 lines / mm;

- 9 FD-24K type radiation receivers behind slits, the position of which corresponds to wavelengths of 0.3 μm, 0.4 μm, 0.5 μm, ..., 1.0 μm, 1.1 μm;

- 9 AD795 photocurrent amplifiers;

-9 ADC AD7894;

- 9 RAM 573RF2;

- 9 dividers 27512;

- digital recorder NT1616.

Example 2

Elements used:

- optical system - Industar-51 lens;

- a beam splitting device in the form of a fiber optic collector with one common input and 9 outputs, behind which there are interference light filters with a passband of 10 ... 15 nm and transmission centers of 0.3 μm, 0.4 μm, 0.5 μm, ..., 1, 0 μm, 1.1 μm;

- the remaining elements, as in example 1.

The main error of the device is determined by the rate of change of temperature of the measured object, it should not exceed 1% during the response time of the device (20 ms). When this condition is met, the error in determining the spectral emissivity in the measuring channels will be less than 1%, and the total error in determining the entire characteristic during interpolation of intermediate values will not exceed 3-4%. Errors due to ADC converters are much lower, do not exceed 0.1%, because ADCs are 14-bit, the rest of the elements (dividers, memory blocks, tagistrator) do not affect the measurement error.

Thus, the described device, due to the simultaneous measurement of the signal from the object in 9 channels, makes it possible to find the spectral emissivity of heated objects in workshop conditions at objects with a variable temperature with an error several times smaller than in known devices using standard spectral devices.

The device will find wide application in the study of the spectral emissivity of a wide range of high-temperature materials, primarily metals and their alloys.

Information sources

1. S.S. Sergeev "Improving the accuracy of temperature measurement using new models of pyrometers firm" TECHNO-AS ". Devices, No. 1, 2009, p.1-6 - analogue.

2. Emissive properties of solid materials. Directory. Under the total. ed. A.E. Sheindlin. M .: Energy, 1974, 472 p. pg. 142-143 - prototype.

Claims (1)

A device for determining the spectral emissivity of heated objects, containing an optical system located along the radiation of the object under study, a beam splitting device that emits N narrow spectral ranges in the radiation spectrum of the object uniformly across the entire spectral range of the device, and a recording device, characterized in that, In order to increase the accuracy of measuring the spectral emissivity of heated objects, the number of spectral bands N is chosen to be larger 6, the device includes N independent radiation receivers, N analog-to-digital converters (ADCs), N memory blocks, N dividing devices, a synchronizer, as well as a channel for determining the temperature of the measured object, while the optical input of the radiation receiver in each channel is connected to beam splitting device, and the electrical output is connected to the input of the corresponding ADC, the first output of which is connected to the first input of the corresponding dividing device, the second output of the ADC is connected to the input of the corresponding memory block, for which it is connected to the second input of the dividing device, the outputs of the dividing devices are connected to the inputs of the registration device, the temperature channel of the measured object is in contact with the object, the output of the temperature detection channel is connected to the input of the registration device, all ADC synchronization inputs and the synchronization input of the temperature detection channel the measured object is connected to the output of the synchronization device, and radiation from the object is recorded simultaneously in all spectral bands.