SU1516804A1 - Atomic absorption analyzer - Google Patents

Abstract

The invention relates to technical physics and is intended for use in spectral instrumentation. The purpose of the invention is to improve the accuracy of measurements of the useful signal. The signal from the lamp 7 simultaneously arrives at the signal extraction unit 19 and through the optical system 12, 14, the atomizer 13 and the monochromator 15 - at the photodetector 16. The recording system 18 detects the radiation of the lamp 7 at the same time, which compensates for interference in the light flux. In addition, due to the fact that lamp 7 contains several cathodes, for example, cathodes 9-11, a large difference in atomic absorption coefficients is achieved, which also leads to an increase in measurement accuracy. 2 Il.

Description

The invention relates to technical physics and is intended for use in atomic absorption spectral instrumentation.

The purpose of the invention is to increase the accuracy of measuring the useful signal by eliminating fluctuations in the radiation of a spectral lamp.

Figure 1 presents the block diagram of the analyzer; figure 2 - block diagram of the switch.

The block diagram of the analyzer (Fig. 1) contains a pulse generator 1, a switch (block) 2, a lamp power supply unit 3, power amplifiers (blocks) 4-6, a lamp 7 containing an anode 8 and several cathodes, in this case griri cathode 9 -eleven. Power amplifiers are connected to the cathodes of the lamp. The cathodes of the lamp have through holes for the passage of radiation in both directions through the windows (indicated by arrows). The radiation of the lamp 7 through the optical system 12 and 13 is directed through the atomizer 14 and the monochromator 15 to the photodetector 16. The signal from the photoreceiver (block) 16 is fed to the input 17 of the system 18 for the division, registration and processing of the light signal. Through the other window, the same radiation from the lamp is injected by a system of blocks 19 containing a device 20 for selecting a light signal (for example, a monochromator) and a photodetector 21. The signal L from the output of block 19 is fed to the input 22 of block 18, and then to the logarithm (block) 23.

The signal from the input 17 is fed to the device (block) 24 of the pulse separation (as it can be used conventional electronic keys, controlled from the side of the pulse generator 1 through the switch 2) The signals from the output of the block 24 are fed to the logarifters 25 and 26, then devices (blocks) 27 and 28 of the subtraction which also receives a signal from the output of block 23. The output signal of blocks 27 and 28 goes to block 29 of the subtraction (where it is subtracted). Finally, the signal is indicated by block 30.

The analyzer works as follows.

The pulse generator 1 generates a sequence of pulses that goes to switch 2. The commutator (figure 2) contains a counter 31 connected to a distributor (a block 32 of pulses. Number of bits)

5 0 5 Q

.Q.

five

50

31 is selected to be larger than necessary to control the block 32, which is connected to the higher bits of the counter 31, since this is necessary to provide the necessary time delays in the operation of the spectral lamp 7. Thus, the signals of the generator 1 are fed to the counter 31, its bits are connected to the block 32. The signals from block 32 arrive at power amplifiers and sequentially turn them on. Suppose that the cathodes of the lamp 7 are turned on in the direction from cathode 9 to cathode 10.

Turning on the cathode 9 provides a light signal (for short durations) with virtually no self-absorbing resonance line. At this point, the atomic absorption coefficient at its center is maximum. The signal controlled by the power amplifier 4 is used to turn on the unit 24. After turning on the cathode 9, the radiation of the lamp enters the block 19, where it is allocated, and then goes to the block 22, where the signal is logarithmized. The signal from the output of block 24 goes to logarithm 25. Both of these signals are then subtracted in subtractor 27. The latter causes the fluctuations in the luminous flux of the lamp 7 to compensate for the cathode 9. At the same time, a cloud of neutral atoms is formed in the cavity of the cathode 9, which gradually dissipates. Cathode 10 is turned on when it has not yet resolved. The moment of switching on the cathode 10 can be determined by experiment. When the cathode 10 is turned on, block 19 still captures Unabsorbed light, while block 16 captures light with a reduced atomic absorption coefficient in the center. resonance line, because the radiation passes through the above-mentioned cloud of neutral atoms created by the cathode 9.

If there are only two cathodes in lamp 7, then the output of block 2, controlling block 5, now controls the pulse separation device. The signal from its output through the logarithm 26, the device 28 is subtracted and enters the subtractor 29.

Thus, when the concentration of substances changes, the signal corresponding to the first measurement (and with compensated fluctuation disturbance) goes to block 29. At the second

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In the measurement, a signal with compensated fluctuation disturbance is supplied to block 29 from the output of block 28. The control signals of the power amplifier are also controlled by signals fed to blocks 27 and 28, for example, passing them through ordinary electronic switches. This is necessary to avoid interference in blocks 27 and 28.

168046

Thus, the proposed analyzer provides an increase in the accuracy of measuring the concentration of elements both by reducing the compensation of radiation fluctuations and by obtaining a greater difference in the atomic absorption coefficients in the center of the line, which is an advantage over the known device.

ten

If lamp 7 contains more cathodes, for example, three, then k-atom 10 serves as a means of generating neutral atoms in the cavity of cathode 10 and due to their diffusion and in the cavity of cathode 9. Measurements are carried out only when cathodes 9 and 11 work. 11, block 19 still registers unabsorbed light, and block 16 absorbs, and the atomic absorption coefficient at the center of the resonance line is significantly more reduced compared to the known device when the lamp is powered by a large current pulse. Obviously, at equal currents in the second case, a greater drop in the atomic absorption coefficient at the line center can be obtained, and thus the accuracy of measurements of the element concentrations can be improved.

After that, the cathodes 9-11 are turned off for the time of switching the lower bits of the counter 31, which corresponds to a pause in the lamps. The latter is necessary for resorption of vapors in the lamp and ensuring the maximum atomic absorption coefficient of the resonance line B to its center when the cathode 9 is re-operated.

Claims (1)

Invention Formula An atomic absorption analyzer containing a spectral lamp consisting of an anode and a hollow cathode, placed in a cylinder with a window for radiation output, a power supply unit for the lamp containing a pulse generator and an amplifier connected to the cathode of the lamp, optical system, atomizer , the main system for extracting, detecting and processing the light signal of a lamp, characterized in that, in order to improve the accuracy of measurement, the analyzer introduced an additional system of separation by the new system, and the spectral lamp contains a second window for the output of the radiation and at least one additional cathode installed along the axis of the emitted light, the cathodes having through holes and connected to additional power amplifiers, entered into the power supply unit and the inputs connected to the output of the pulsed generator through the switch, while the additional system of selecting the light signal is installed in the path of the light exiting the second window spectral lamp. 35 40