SU1366922A1 - Nephelometer - Google Patents

Abstract

The invention relates to the field of photometric measurements and can be used in the chemical industry to control a turbid environment. The invention makes it possible to increase the accuracy of nephelometric control of disperse media by eliminating errors caused by the non-linearity of photodetectors while maintaining a high channel switching frequency. For this, the working chamber (RK) 5 is installed before the intersection of the optical channels formed by lenses 3 and 4, and an optical attenuator 14 is installed at the intersection of the optical channels. The radiation sources 1 and 2 are alternately switched on by the control circuit 15. In the first half-period the radiation from source 1 transmitted through the RC is attenuated by the attenuator 14 and hits the photodetector 13, while the radiation scattered in the Republic of Kazakhstan simultaneously hits the photodetector 12. In the second half-period, the radiation from the source 2 passed the SL

Description

 3 f

I, 1c

:

00 about

O5 CO

Yu

ttt

through the RC and attenuated by the attenuator 14, enters the photodetector 12, while the radiation scattered in the RC enters the photodetector 13. The signals from the photoreceivers are separated by a signal separation circuit 1b and processed in a computer 17. 1 sludge.

one

The invention relates to a technique of photometric measurements and can be used in chemical industry to control turbid media, for example, to monitor contaminants of combustible and lubricating materials in conditions of increased explosive hazard, as well as in chemical-photographic industry to control the process of solid phase deposition. .

The purpose of the invention is to improve the measurement accuracy.

The drawing shows a functional diagram of a nephelometer.

The nephelometer contains controlled sources 1 and 2 of radiation, which can be used as light-emitting diodes located along the course of radiation from radiation sources of lenses 3 and 4, forming the first and second optical channels whose axes intersect at one point, the working chamber 5 with svetopropuskantsimi. windows 6-9 installed against output windows 8 and 9 of lenses 10 and 11 to collect radiation scattered in the chamber to photo detectors 12 and 13 with amplifiers installed in the second and first optical channels, optical attenuator 14 installed at the intersection of the first and the second optical channels, the signal processing system from the photodetectors, including the control device 15, the signal separation unit 16 and the computing device 17, the controlled light sources being connected to the first output of the control device 15, the second output of which Wow is connected to block 16. signal separation, the signal inputs of which are connected to the outputs of photodetectors 12 and 13 with amplifiers, and the outputs of the signal separation unit are connected to the inputs of the computational

a device whose output is a nephelometer output.

. As an optical attenuator 14, an optical 5 wedge or diaphragm, or a system of two crossed polarisations, or any other optical system, can be used to attenuate the radiant flux.

The nephelometer works in the following 0 way.

The radiation sources 1 and 2 are alternately switched on by the control circuit 15. In the first half period of measurement, the radiant flux from the source 1 is radiation. neither, formed by the lens 3, passes through the window 6 of the working chamber, the working chamber 5 with the test medium, window 8, optical attenuator 14 and enters the photodetector 13. The signal, which is proportional to the luminous flux, arrives at the first signal input of the circuit 16 separation of signals.

At the same time, the light flux through the window 8 of the working chamber scattered by the medium is focused by the lens 10 onto the photo receiver 2, the signal from which is fed to the second signal input of the signal separation circuit 16.

Under the action of the control signal 0, the control circuit 15 at the first and third outputs of the signal separation circuit are formed in a direction equal to the signals fed to the input. The voltage data is stored at the outputs of the signal separation circuit 5 for the second half period of measurement.

During the second half period of measurement, source 1 of control circuit 15 is turned off, and source 2 is turned on. 0 The radiant flux from the radiation source 2, formed by the lens 4, passes through the window 7 of the working chamber, the working chamber 5 with the test medium, window 9, optical attenuator 14 and hits the photodetector 12. The signal is proportional to the light flux, post-R (B) is fed to the second input of the signal separation circuit 16.

At the same time, the light flux diffused by the medium through the window 9 of the working chamber is focused by a lens onto a photodetector 13, the signal from which is fed to the first signal input of the signal separation circuit 16. . Yu

Under the action of the controlled signal T (B), the voltage from the control circuit 15 at the second and fourth outputs of the signal separation circuit is equal to the signals applied to the signal inputs of the separation unit 15. The voltage data at the second and fourth outputs is stored for the time of the next measurement cycle. T, jT, T,

Thus, at the output of the unit T-dividing the signals, the following signals are present: U and are signals from the photodetectors 12 and 13 with the radiation source 1 turned on and ufj and medium scattering in the first channel in the direction of the photodetector 12, due to the symmetry of the measurement circuit equal to the scattering of the medium in the second channel in the direction of the photodetector 13;

transmission of the medium in the first channel, due to the symmetry of the measurement circuit equal to the transmission of the medium in the second channel; measured parameter (turbidity of the medium);

donkey

passing windows 6, 7, 8, and 9;

Transmission. Weakness 14.

Using expressions (2) - (5) .dl signals from photodetectors 12 and 13 at 25 signals U, according to the processing circuit of the switched on radiation source 2. These signals (1) receive the expression signals are fed to the input of the computing device 17, which implements the following signal processing algorithm 30

does not depend on the intensity of the radiation sources and on the contamination of the windows of the working chamber. Due to the nonlinearity of the photodetectors, the result depends on the sensitivity of the photodetectors. However picking up the transmittance attenuator

and s «(2iis, 5 1 RL (2)

(6)

fishing:

and

at “112,

g

four

and ,, iGz

s, i (, p-,;) tch / 1)

Thus, the measurement result

(one)

where and is the measurement result.

Using the laws of light attenuation

medium for U signals,

and

wives:

ufi, and; e

5 You can write the following expressions:

 F s, (cf.) T, Ta-K (; 1) s

(F

and

"P S ,,

(2

) -t.

t, tf)

(2) J (3)

14 in such a way that the intensities directly transmitted to the photoreceiver and scattered radiation are equal to Ф, «i 40 Рчг, i fs compare the sensitivity of the photodetectors)

.i ,, Ф 8, (Ф „). Т ,. Td. t (/ 5) T.MJC) 9 s ,, K) -T, -T, .R (p) (5)

de 5, g (P), 5, (F) - sensitivity of photodetectors 12 and 13 for the radiation flux,

  radiation fluxes from sources 1 and 2 that fell on the photodetector 12; 13 radiation fluxes from

sources 1 and 2, trapped on the photodetector 13; .I

I 2.

 , Р - radiation fluxes from radiation sources 1 and 2:

one

scattering of the medium in the first channel in the direction of the photodetector 12, due to the symmetry of the measurement circuit equal to the scattering of the medium in the second channel in the direction of the photodetector 13;

transmission of the medium in the first channel, due to the symmetry of the measurement circuit equal to the transmission of the medium in the second channel; measured parameter (turbidity of the medium);

donkey

Using expressions (2) - (5). The signal U, according to the signal processing circuit (1), is given by

and s «(2iis, 5 1 RL (2)

(6)

s, i (, p-,;) tch / 1)

Thus, the measurement result

14 in such a way that the intensities directly transmitted to the photoreceiver and scattered radiation are equal to Ф, «i 40 Рчг, i fs compare the sensitivity of the photodetectors)

 ,), s ,, (p ,;) s ,, (cp.t). /

As follows from expression (6), the measurement result does not depend 45 on the sensitivity of the photodetectors:

one

and - K

  T (| 3)

(7)

K -; - - constant of the device.

50

WASP

The invention makes it possible to eliminate the error due to the nonlinearity of the photodetectors, and to improve the measurement accuracy.

55 Formula of invention

A nephelometer containing the first and second radiation sources, connected to the control circuit, is located 5 13669226

optically formed formations of the first and second

the system for forming the first and second optical channels and the point of the second optical channels, the axes of which are the axes of these channels,

intersect at one point, the working point of the intersection of the axes of the channels to the set chamber for the medium under investigation, first the optical attenuator, and between

and the second photodetectors located by the working camera and photodetectors

in the first and second optical channels, the optical collection system on

connected to the processing system of the sig-second photodetector of radiation, the rails connected to the controlled-io circuit of the test medium in the first

Nor, characterized by the channel and optical collection system

that, in order to improve the accuracy of the measurement of the first photodetector of radiation,

rhenium, the working chamber is installed in the medium in question

both channels between these optical-second channel.

Claims (1)

Claim The nephelometer containing the first and, · the second radiation sources, connected to their control circuit, is located5 13 During the emission, optical systems for forming the first and second optical channels, the axes of which intersect at one point, the working chamber for the medium under investigation, the first and second photodetectors located in the first and second optical channels, connected to the signal processing system, connected to the control circuit, characterized in that, in order to improve the measurement accuracy, the working chamber is installed in both channels between the optical themes of the formation of the first and second optical channels and the intersection point the axes of these channels, while an optical attenuator is installed at the point of intersection of the axes of the channels, and an optical collection system is inserted between the working chamber and the photodetectors on the second photodetector of radiation scattered by the test medium in the first channel, and the optical collection system on the first photodetector of the radiation scattered by the medium under investigation the second channel.