SU1543309A1 - Absorption analyzer - Google Patents

Abstract

The invention relates to analytical instrumentation and can be used to create optical analyzers for liquid and gas. The aim of the invention is to reduce the measurement error by reducing the signal power loss during modulation. The goal is achieved by additionally introducing a unit for switching the speed of rotation of the optical filters, the output of which is connected to the drive input, and the input to the second output of the position sensor of the optical filters. 1 il.

Description

The invention relates to analytical instrumentation and can be used to create optical liquid and gas analyzers with RMS detection of the information signal.

The purpose of the invention is to increase the sensitivity of the analysis, reducing the measurement error.

The drawing shows a diagram of the absorption analyzer.

The analyzer consists of a radiation source 1, a working cell 2 through which the test substance is pumped, a modulator unit and a change of light filters 3 with interference light filters 4 and 5 of the working and reference channels, a stepper motor 6 with a power supply and control unit 7, and a master oscillator 8 pulses with a frequency divider 9, which is controlled by the position sensors of the optical filters 10 through the driver 11, the photodetector 12, the system 13 for recording and processing the signal, the indicator 14.

Absorption analyzer works as follows.

The radiation flux Ф0 from the radiation source 1 passes through the cuvette 2 and enters the node of the modulator and the change of light filters 3, on which the interference light filters 4 and 5 of the working and reference channels are fixed. The filter of the reference channel transmits radiation with a wavelength at which it is not absorbed by the measured component, and the filter of the working channel at which the measured component absorbs radiation. Since the area of the interference light filters is small compared to the total area of the modulator disk, with a uniform rotation of the modulator disk, the luminous flux Mt) reaches the photodetector 12 only during its passage through the optical filters C and 5,

S

(L

ate

with

00

about with

those. during a small part of the whole period of modulation T.

To increase the modulation efficiency, it is necessary to increase the transit time t of the light flux through the optical filters by slowing down the speed of rotation of the optical filters when they are in the radiation flux.

Where

m S and

t with

U dT / dC

sensitivity analysis; the output signal of the measuring transducer of the analyzer with a uniform rotation of the modulation unit and the change of light filters in the absence of the analyzed gas in the working cell; skipping the cuvette;

concentration of gas to be analyzed.

This is achieved by using a rotation speed switch of the light filters, which includes a power supply and control unit 7, a master oscillator 8, a frequency divider 9 and a switching pulse generator 11. For this, the node disk for the modulator and the change of the light filters 3 are rotated with the help of a stepper motor 6 with its power and control unit 7. Control pulses to block 7 are received from master oscillator 8 through frequency divider 9. The division factor changes from 1 to 20 when switching pulses are received from the position sensors of the optical filters 10 through the shaper 11 to the frequency divider 9 as they pass through the luminous flux of the optical filters. The modulated light flux is detected by the photodetector 12. The transmission of the light filters k and 5 is chosen in such a way (taking into account the spectral characteristics of the photoreceiver and the radiation source), so that the signals taken from the photoreceiver are identical in the absence of absorption in the working cell 2. Then the appearance of the test substance in the working cell leads to a weakening of the radiation of the working channel and to the imbalance of the signals taken from the photodetector. The detected imbalance goes to the signal recording and processing system, which is switched

0

five

0

five

0

five

0

five

The sensors are positioned light filters 10 and further on the indicator.

When the frequency of the pulses of the master oscillator is divided by 20 times, the duty cycle of the pulses taken from the photodetector and corresponding to the opening of the light flux is small. Therefore, the coefficient taking into account the power loss of the luminous flux during modulation is close to unity, which ensures a good signal-to-noise ratio and improves the sensitivity of the analyzer. With a uniform movement of the modulator, the pulse ratio is large, and to achieve the same signal-to-noise ratio, it is necessary to use more efficient radiation sources and photodetectors, which is not always possible.

The efficiency of the solution is to increase the sensitivity of the analysis, increase the detected signal-to-noise ratio and, as a result, decrease the measurement error by reducing the power loss of the light signal during modulation, which leads to an increase in measurement accuracy.

This analyzer thus combines the advantages of differential structural diagrams of analyzers (high sensitivity analysis) and single beam multichannel (high temporal stability of insensitivity readings to non-selective contamination of optical elements).

Claims (1)

Invention Formula An absorption analyzer containing a radiation source and a working cell sequentially arranged along the radiation path, a node for modulating and changing the working and reference channel optical filters, mechanically connected to the drive output and optically to the input of the position sensor of the light filters, photodetector connected to the first input of the recording system and processing the signal, the second input of which is connected to the first output of the position sensor of the optical filters, characterized in that, in order to increase the measurement accuracy by reducing the sweat s output signal at modulation it additionally introduced switching unit filters rotational speed coefficient, the rate of slowing down the movement of light filters at the moments of their presence in the radiation flux U (dT / dC) sensitivity analysis; the magnitude of the signal at the output of the recording system with a uniform rotation of the light filter a moat of a node for modulating and changing light filters; T - the transmission of the working cell; C - concentration of the analyzed gas, the output of the rotational speed switching unit of the filters is connected to the input of the drive, and its input is connected to the second output of the position sensor of the optical filters. Editor M.Nedoluzhenko Compiled by I. Ilyin Tehred M. Khodanych Order 396 Circulation 507 VNIIPI State Committee on Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, 4/5 Raushsk nab. Corrector o.Tsiple Subscription