RU2445606C1 - Laser device for measuring dialysate flow rate - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: laser device for measuring flow rate of dialysate has a dialysate pumping system with a membrane. The laser device also has a laser light source, a laser beam splitter for irradiating the dialysate, a photodetector with light reflectors and an electronic unit for measuring the flow rate of dialysate. The dialysate pumping system has one or more tubular cuvettes, on the inner surface of which there is an interference coating, and a probing laser beam passes along the axis of the cuvette. The material used for the interference coating is metal fluorides and/or selenides.

EFFECT: high accuracy of measurements owing to high output of scattered laser light.

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Description

The inventive device relates to the field of measurement technology, specifically to laser Doppler anemometry, and can be used for non-contact remote measurement of dialysate flow rate.

Laser Doppler anemometry is widely used in the analysis of flow characteristics of gas and liquid media [1]. In the field of applied medical optics, measuring the flow rate of dialysate (the totality of substances passing through the dialysis membrane during dialysis) is of great practical importance, which determines the effectiveness of hemodialysis machines used to temporarily replace the excretory function of the kidneys [2].

Known laser Doppler speed meters containing a sequentially located laser, a polarizing splitter, focusing and receiving lenses, a polarizing prism analyzer, two photodetectors and an electronic unit for measuring Doppler frequency [3].

The disadvantage of these devices is the relatively low accuracy of the measurements due to the low signal-to-noise ratio.

A laser Doppler speed meter is also known, which contains a laser and spherical and cylindrical lenses sequentially arranged along the beam, a Wollaston polarizing splitter of a laser beam, a rotary mirror with two slit diaphragms located in the path of the beams, a focusing lens, and protective glass. It also includes a second rotary mirror, a micro lens, an interference filter, a field slit diaphragm, an infrared filter, a Wollaston polarizing prism, two photodetectors installed on the path of the laser beams split by this prism and connected by outputs to the inputs of the subtractive circuit, sequentially placed in the direction of the scattered surface of a moving object , and an electronic measurement unit. The electronic measurement unit contains a filtration unit, two comparators, counting pulse generation units and a pulse strobe, and analog and digital speed meters [4].

The specified flow rate meter also has insufficient measurement accuracy caused by a low signal to noise ratio.

The closest technical solution of the claimed device is a dynamic scattering device for analyzing a dialysate stream, containing a dialysate pumping system with a membrane, a light source with a fiber optic fiber for irradiating dialysate, a photodetector, a reflector and a dialysate pump [5].

The disadvantage of this device is the low yield of scattered laser radiation due to significant losses when scattered radiation is introduced into the optical fiber, which reduces the accuracy of the measurements.

The task of the invention is to increase the accuracy of measurements by increasing the yield of scattered laser radiation.

The proposed laser device for measuring dialysate flow rate comprises a dialysate pumping system with a membrane, a laser light source with a laser beam splitter for irradiating dialysate, photodetectors with reflectors and an electronic dialysate flow rate measuring unit, characterized in that the dialysate pumping system contains one or more tubular cuvettes, on the inner surface of which an interference coating is applied, and a probe laser beam is transmitted along the axis of the cuvette.

Fluorides and (or) metal selenides can be used as materials of the interference coating [6].

A fundamentally new technical solution is the placement of one or more tubular cuvettes in the dialysate pumping system, on the inner surface of which an interference coating is applied, and a probe laser beam is transmitted along the axis of the cuvettes. An increase in the measurement accuracy is achieved here by increasing the output of the scattered laser radiation by transmitting a probe laser beam along the axis of the cuvettes, which ensures the maximum value of the obtained Doppler signal.

The proposed device is illustrated by the following graphic material.

Figure 1 shows a schematic diagram of a laser device for measuring dialysate speed, where 1 is a Michelson interferometer, 2, 3 are translucent mirrors of the interferometer, 4, 5 are reflective mirrors of the interferometer, 6 is a laser, 7 is a laser beam splitter, 8-11 - tubular cuvettes, 12 - hoses, 13 - dividing plates, 14 - electronic unit for measuring dialysate flow rate.

Figure 2 presents the system for pumping a solution of dialysate, where 12 are hoses, 15 is a membrane, 16 is a dialysate tank.

Figure 3 presents a tubular cuvette 8 with windows 17.

The device operates as follows. Beams of radiation generated by a laser (6) after passing through a laser beam splitter (7) pass through translucent mirrors (2), (3) and propagate in the Michelson interferometer (1) in opposite directions, reflected from translucent (2), (3) and opaque mirrors (4), (5). Laser radiation is scattered in a dialysate solution pumped through hoses (12) using a dialysate solution pumping system with a dialysate cleaning membrane (15) and a dialysate tank (16) through cuvettes (8-11) with enlightened plane-parallel windows (17) placed in the shoulders of the interferometer. The Doppler signal generated by the scattering of laser radiation propagating in the Michelson interferometer in opposite directions through the dividing plates 13 is fed to the input of the electronic speed measuring unit (14), which is a frequency meter with a controlled counting clock.

By setting the counting time multiple of the conversion factor of the Doppler frequency to the speed value, it is possible to obtain the frequency meter readings directly in units of speed [1].

Due to the propagation of laser beams in the Michelson interferometer in opposite directions, a doubled value of the received signal is achieved, so that the dialysate flow rate

where c is the speed of light in the dialysate solution, Δf is the frequency difference between the received Doppler signal and the laser radiation source, f ₀ is the laser radiation frequency, θ is the angle between the direction of movement of the dialysate stream and the scattered radiation wave vector [1]. In the present invention, the conditions for obtaining the maximum value of the received signal are realized, because here θ = 0 and

Thanks to a new technical solution for placing one or more tubular cuvettes on the inner surface of which an interference coating is applied in the dialysate pumping system, an increase in the measurement accuracy is achieved by increasing the yield of scattered laser radiation when a probe laser beam is transmitted along the axis of the cuvettes, which ensures the maximum value obtained Doppler signal.

Literature

1. Dubnischev Yu.N., Arbuzov V.A., Belousov P.P., Belousov P.Ya. Optical methods for studying flows. Novosibirsk: Sib.univ. ed, 2003.

2. Grinvald V.M., Kiselev B.L., Maksimov E.P., Khaitlin A.I. Equipment for artificial blood purification, ed. V.A. Viktorov. M .: CJSC VNIIMV-VITA, 2002.

3. Auth. testimonial. USSR №529660.

4. Artamonov B.F., Belousov P.Ya., Dubnischev Yu.N., Zhmud V.A., Stolpovsky A.A. Laser meter of speed of hot rolling // Steel, No. 8, 1986.

5. US patent No. 5485270 - prototype.

6. RF patent No. 2097801.

Claims (2)

1. A laser device for measuring dialysate flow rate, comprising a dialysate pumping system with a membrane, a laser light source with a laser beam splitter for irradiating dialysate, photodetectors with reflectors and an electronic dialysate flow rate measuring unit, characterized in that the dialysate pumping system contains one or a more tubular cuvette, on the inner surface of which an interference coating is applied, and a probe laser beam is transmitted along the axis of the cuvette. 2. A laser device for measuring dialysate flow rate according to claim 1, characterized in that metal fluorides and / or metal selenides are used as interference coating materials.

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