RU1831674C - Infra-red filter analyzer - Google Patents

Abstract

SUMMARY OF THE INVENTION: An IR analyzer comprises a comparison channel and a measurement channel containing IR radiation, a modulator, first and second focusing mirrors, sample cuvettes, a set of interchangeable filters and an IR radiation receiver that is connected to the digital recorder through a series-connected amplifier , made with adjustable gain, synchronous rectifier, DC component extraction circuit, analog optical density computer and analog-to-digital converter and the synchronous rectifier is also connected to the pulse generator of the frequency of rotation of the modulator, contains a reference voltage source, an amplifier gain control circuit and a digital code reader for the installed filter, the reference voltage source is connected to an analog optical density computer, a digital reader code through the gain control circuit connected to the amplifier, and the filters are fixed in the walls of a multifaceted holder having an axis rotations and a position lock, where code holes are also made, four lamps or optical fibers and four photodiodes are installed on both sides of the holder wall, which together with the code holes form a digital code reader for the installed filter, the second mirror and the infrared receiver multifaceted holder. 3 ill. 00 OJ (H CO

Description

The invention relates to the study of the composition of gaseous, liquid and solid samples in the infrared range of the spectrum, mainly for geology, in the study of sedimentary rocks for mineral composition and their gas-oil-bitumen content.

The purpose of the invention is to simplify its construction by eliminating the optical part of the comparison channel.

The essence of the invention lies in the fact that the functions of the comparison channel are transferred to the source of the reference voltage. Initially, in the absence of the analyzed sample in the cuvette, the amplifier gain is set so that when any filter is installed in the measuring beam, the voltage at the first input of the analog optical density calculator will be the same as the reference voltage source connected to the second input of the analog optical density calculator. And during the measurements, the comparison of the voltage change in the measuring channel is carried out with the reference voltage set by the source of the reference voltage.

To achieve this goal, the optical circuit of the analyzer is made according to a single-beam circuit, but it uses the principle of two-channel measurement by simulating the signal of the reference channel by electronics.

The use of a single-beam scheme made it possible to use not a pair of identical filters per channel, which are very difficult to manufacture, but only one. In this case, the cost of the analyzer is sharply reduced, since the number of filters is halved. In addition, the use of a single-beam scheme allows the modulator to be positioned after the first focusing mirror, and the mirrors can be made with a small focal length and brought closer to the IR source and receiver, which makes it possible to increase the intensity of the measuring beam. Even in the adopted scheme, the beam is rotated only at the receiver and at a small angle (about 45 °). which improves the quality of focusing on the sensitive element of the infrared receiver. These measures increase the sensitivity and accuracy of the analysis, especially in the long wavelength region of the spectrum.

The use of one filter per channel and a single-beam optical scheme allowed all light filters to be placed on the drum, which is the dispersing element of the analyzer and is constantly located inside it, which increases the reliability of the device and improves its service.

Figure 1 - 3 shows the structural diagrams of the optical and electronic parts of an infrared filter analyzer of substances.

 The optical part of the analyzer (Fig. 1) consists of a source of infrared radiation 1, the first and second spherical focusing mirrors 2 and 3, a 4-measurement modulator

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a beam rotated by an engine 5, a cuvette 6, a set of light filters 7 mounted in the walls of a multi-faceted holder 8 whose axis 9 is mounted on the analyzer platform 10 (FIG. 2) and a handle 11 for changing the light filters 7, a device for fixing the position of the filter 12, the receiver 13, infrared radiation, pulse shaper 14 of the rotational speed of the modulator, consisting of an incandescent lamp and a photodiode and a reader 15 of a digital code for an installed filter 7, which consists of four incandescent lamps 15a, four photodiodes 156 and a laid on the drum 8 in accordance with the installed filter 7 and the fixing device 12 of the holes 15B, indicating the number of the installed filter in binary digital code.

The electronic part of the analyzer (Fig. 3) consists of an infrared receiver 13, an amplifier 16 with a controlled gain, a synchronous rectifier 17. controlled by pulses from a pulse shaper 14 of the speed of the modulator, a low-pass filter 18 used to isolate the constant component of the pulsating voltage, which is supplied to the first input of the analog computer of the optical density 19, the other input of which receives the reference voltage from the reference voltage source 20 of the analog-to-digital conversion the indicator 21 and the digital display 22. Information from the reader 15 of the digital code of the installed filter enters the gain control circuit 23 of the amplifier 16. The gain of which is selected individually for each installed filter.

The analyzer works as follows. The IR source 1, which is a helix of a nichrome wire heated to a temperature of about 1000 ° C, produces radiation in the range of 0.4-15 microns, uniformly decreasing in the long wavelength region. This radiation is focused by the first spherical concave mirror 2 into a parallel beam, which hits the second focusing mirror 3. With this mirror 3, the beam is focused on the sensitive element of the infrared radiation receiver 13 with an offset of 40-45 ° from the measuring beam. The formed parallel beam is interrupted by the modulator 4, passes through the cell 6 with the analyzed sample and the installed filter 7. In accordance with the spectral properties of the sample and the installed filter 7, a smaller amount of radiation will arrive at the receiver 13 than without the analyzed sample. The receiver 13 converts the modulated PC radiation to an alternating voltage, which is amplified by the amplifier 16 and is fed to the input of the synchronous rectifier 1.7. where the rectification is carried out in accordance with the phase of the reference signal taken from the modulator 4. Then, the rectified signal passes through a low-pass filter 18, which selects only the constant component and excludes the ripple voltage entering the optical computing unit 19 densities. The other input receives the reference voltage from the reference voltage source 20, equal to the voltage level at the first input without the analyzed sample in the cell 6. The optical density calculator 19 performs the calculation operation in accordance with the formula K-log log-r D (A).

The calculation result is converted into a digital code on the ADC 21 and displayed on the digital indicator 22. In accordance with the number of the filter 7 set to the beam, the reader 15 generates a digital binary code, which is fed to the amplifier gain control circuit 23. Thus, when changing the filter in accordance with the code, the gain of amplifier 16 is changed. It is selected on all filters so that when any filter is installed at the input of the optical density calculator 19, the rectified voltage is the same and the voltage of the reference voltage source 20 wife is set equal to him.

Work with the analyzer is as follows. Here are the steps for adjusting the supports. the analyzer state and the measurement process are separated in time. Before measurement, a cell without a sample is installed in the beam and the amplifier gain is adjusted on each filter so that the first voltage input of the analog block of the optical density calculator has the same voltage when all filters are installed. Then, the same voltage is set at the reference voltage source, from which it is supplied to the second input of the optical density calculator. If these voltages are set correctly, the indicator will show a zero reading.

After the tuning step, a measurement step is performed. In this case, the analyzed sample is placed in the same cuvette and readings are taken when all filters are sequentially installed in the measuring beam. The readings will correspond to a reduced voltage at the output of the amplifier with installed filters, which corresponds to absorption in the analyzed ranges

spectrum. Periodically, after several measurements, the step of checking and adjusting the reference state of the analyzer is again performed.

Claims (1)

The claims An infrared filter analyzer of substances, comprising a comparison channel and a measuring channel containing an optically coupled IR radiation source, a modulator, first and second focusing mirrors, a cuvette for the analyzed sample, a set of interchangeable ones installed in. filter holder and infrared receiver. which is connected to digital the recorder through a series-connected amplifier, a synchronous rectifier, a DC component isolation circuit, an analog computer of optical densities and analog-to-digital the converter, and the synchronous rectifier is also connected to the pulse generator of the rotational speed of the modulator, characterized in that, in order to simplify its design by eliminating the optical part of the comparison channel, the amplifier is made with a control gain, and the analyzer further comprises a reference voltage source gain control circuit an amplifier and a reader of the digital code of the installed filter, and the comparison channel is made in the form of a reference voltage source connected to an analog optical density computer, the reader of the digital code is connected to the amplifier through the gain control circuit, and the filter holder is made in the form of a polyhedron with an axis of rotation , a position lock and code holes, and a reader in the form of four lamps or LEDs and four photodiodes located on both sides of the wall of the holder, with the second mirror and the infrared radiation receiver inside the multi-faceted holder. 1shch ff / fft No.% IL 8 gglf fri9tE8l Fig.Z