SU1545151A1 - Apparatus for analysis of expired air - Google Patents

Abstract

The invention relates to gas analyzing instrumentation and can be used to create gas detectors of the composition of exhaled air. The purpose of the invention is to increase the accuracy of the analysis and save it during the rapid analysis. In the device, the chamber is divided into two volumes — sampling and analytical, each of which is provided with ventilation openings. The inlet opening of the sampling volume and the opening connecting the sampling volume with the analytical volume are arranged to provide a diffusion gas inlet into the analytical volume, for example, mutually perpendicular. The device is equipped with a thermal stabilization unit of the chamber, and the sampling volume of the chamber is removed by a heating element located in its lower part, and two thermister meters, the measuring and control ones. Both thermistors are connected to the inputs of the block for determining the completeness of sampling, the heating element is connected to the output of the chamber thermal stabilization unit, to the input of which the control thermometer is connected. 1 hp f-ly, 2 ill.

Description

in the partition. In both volumes there are air vents 4, in addition, in the sampling volume .1 there is a horizontal inlet 5, provided with a mouthpiece 6. Otg. Versions 3 and 5 are mutually perpendicular to provide a diffusion approach of the analyzed sample to an analytical volume located in the analytic volume, 2 the gas-sensitive element 7 is bounded, as usual, from the bottom and from above by metal grids 8. Its heater 9 is connected to the output of the voltage regulator 10, and the gas sensor -4 ny layer 11 -vK to the output 12 of the output signal measurement unit "In the sampling volume there are two thermisters - a measuring 13 and a control 14. The measuring thermometer 13 is located 2 directly behind the entrance hole Stage 5, and the control thermister 14 - in a place practically not blown out with exhaled air. Both thermister 13 and

the sample is diluted with ambient air. And only with a ratio of areas within 0.5-2, an increase in the accuracy of the analysis and its preservation during the rapid analysis due to good ventilation of the gas sensitive element is achieved.

The device works as follows.

Exhaled air through the mouthpiece 6 and the inlet 5 enters the sampling volume of 1 chamber. When this happens, the measuring thermistor 13 located in the sampling volume 1 in front of the inlet 5 is cooled. The resistance difference between the measuring thermister 13 and the control thermister 14 (the sample practically does not fall on the thermometer 14 and its resistance depends only on the temperature in the chamber) is an informative input parameter for block 15 determining the completeness of sampling

14 are connected to the inputs of the 15-meter unit. When this difference is achieved, the sampling rate is complete. The control thermometer 14 is connected to the input of the thermal stabilization unit 16 of the chamber, to the output of which the set threshold is connected. The LED signals the end of the sampling and the possibility of measurements. During the entire sampling part of the sample through the opening 3 diffusively enters the analytical volume 2 on it gas sensitive element 7. Due to chemisorption, the resistance of sensitive layer 11 of gas sensitive element 7 changes. Output signal measurement unit 12 registers a gas sensitive electric resistance variation ment 7 and provides the required information about the presence of an analyte in exhaled air.

At the bottom of the sampling volume, 1 is the chamber heater 17.

The sampling completeness measurement unit 15 consists, for example, of a bridge, in

whose shoulders include thermistors

 and 14, an amplifier block, a comparator and a comparator connected to the output

1 LED,

The block 16 of the thermal stabilization of the chamber consists, for example, of temperature

the dependent divider, amplifier and Schmidt trigger, to the output of which is connected the base of the transistor that supplies the voltage to the chamber heater 17. Thermister 14 is connected to the input of the thermal stabilization unit 16 and the ow - chamber 5 controlled by a thornistor

It is a temperature dependent 14 arm and an adjustable temperature control unit 16 for the camera. For this purpose, to ensure optimal performance of the temperature-dependent divide

The operation of the gas sensitive element during the express analysis of exhaled air is the ratio of the areas of the ventilation openings of the sampling and analytical volumes within 0.5-2.

Experimental studies have shown that with a ratio of areas less than 0.5, the chamber is poorly ventilated, and with a ratio of areas greater than 2, a representative of the selection is lost. When this difference is reached

the set threshold of the block LED signals the end of sampling and the possibility of measurements. During the entire sampling part of the sample through the opening 3 diffusively enters the analytical volume 2 on the gas sensitive element 7 located in it. Due to chemisorption, the resistance of sensitive layer 11 of gas sensitive element 7 changes. The output measurement unit 12 registers this change in the resistance of the gas sensitive element 7 and provides the required information on the presence of the analyzable substance in the exhaled air.

I

During operation of the device, the heater 17 is heated.

The l, one arm of which is the control thermister 14, is fed to the amplifier of the block 16. From the output of the amplifier, the signal goes to the Schmidt trigger, to the output of which the base of the transistor is connected, which supplies power to the chamber heater 17.

f o rm u l a

and

acquisitions

1. A device for analyzing exhaled air, comprising a chamber, provided with

Fie.2

Claims (2)

Claim 1, A device for analyzing exhaled air containing a chamber is provided with 154515! a horizontally located inlet with a mouthpiece and a heater, a gas-sensitive element, the heater of which is connected to the output of the voltage regulator, and a gas-sensitive layer - to the input of the output signal measuring unit, a sampling completeness measuring unit, characterized in that, in order to maintain accuracy during express -analysis, the camera is equipped with a unit for its thermal stabilization, is divided by a partition with a vertical hole into two volumes, a sampling and is located- | An analytical one above it, in which a gas-sensing element is installed, the sampling volume will contain the inlet, the chamber heater located in its lower part, and two thermistors — the measuring one, located immediately behind the inlet, and which? test, both thermistors are connected to the inputs of the unit for measuring the completeness of sampling, the heating element is connected to the output of the thermal stabilization unit of the camera, to the input of which a control thermistor is connected, each chamber volume is equipped with ventilation holes. 2. The device according to π. 1, about. t l and, more generally, with the fact that, in order to ensure the optimal operating mode of the gas-sensitive element during ex .; presue'-analysis of exhaled air, the ratio of the areas of the ventilation openings of the sampling o and the analytical volumes is within 0.52. Figure 1