CN105241835A - CO2 concentration detection method with main-flow-type water vapor influence reduction - Google Patents

Abstract

The invention discloses a CO2 concentration detection method with main-flow-type water vapor influence reduction, wherein a three-channel pyroelectric sensor is employed and includes a CO2 measurement channel, a reference channel and a water vapor measurement channel. The method comprises the following steps: determining peak values and valley values of all terminals according to data collected in the three channels; extracting voltage peak values of the water vapor measurement channel and the reference channel, calibrating a wave form formed by subtracting the two voltage peak values to obtain the voltage peak values corresponding to different water vapor concentrations; extracting the voltage peak values of the CO2 measurement channel and the reference channel, calibrating the wave form by subtracting the two voltage peak values to obtain the voltage peak values corresponding to different CO2 concentrations with the water vapor influence; obtaining a fitted curve of the voltage peak values corresponding to different CO2 concentrations without the water vapor influence; and performing real-time measurement. The method can increase measurement precision of CO2.

Description

A kind of main stream-type reduces the gas concentration lwevel detection method of influence of moisture

Technical field

The invention belongs to biomedical engineering field, is a kind of people's End-tidal carbon dioxide concentration precise monitoring method.

Background technology

In clinical medical monitoring such as grade, in people's breathing, gas concentration lwevel Real-Time Monitoring more and more comes into one's own, and especially partial pressure of carbon dioxide in endexpiratory gas becomes six basic vital signss.The current End-tidal carbon dioxide density monitoring system based on Non-Dispersive Infra-red (NDIR) principle is measured mainly can be divided into two kinds: the side stream type that the main stream-type of directly measurement is monitored and measured by extracting breathing gas is monitored.

Side stream type monitoring can make measuring accuracy higher to extraction gas dehumidification, voltage stabilizing, but due to the time delay extracting air-flow make display waveform have obvious distortion and also equipment more loaded down with trivial details.And main stream-type monitoring can be divided into thermopile sensor to monitor mostly and pyroelectric sensor monitoring, although thermopile sensor monitoring can make circuit power stablize, but the interference due to respiratory air flow makes monitoring result error comparatively large, and waveform also easily occurs drifting problem when long-time continuous is monitored.Pyroelectric sensor occurs Monitoring Performance is greatly improved, and it is wide that it has induction wavelength coverage, fast response time, steady performance, but it is weak also to there is output signal, is subject to the problems such as circuit noise interference.

Although current main-stream formula carbon dioxide monitoring technology is soon corresponding, stable performance, current main-stream formula carbon dioxide monitoring technology is easily subject to people and breathes the not high impact of precision that water vapor absorption infrared light causes.

Summary of the invention

The present invention innovates object: overcome the impact that current main-stream formula carbon dioxide monitoring technology is easily subject to steam in people's breath, provides a kind of people's End-tidal carbon dioxide concentration precise monitoring method.Technical scheme of the present invention is as follows:

A kind of main stream-type reduces the gas concentration lwevel detection method of moisture effects, the infrared light module adopted and sensor detection module are placed in the two ends of pipeline adapter respectively, triple channel pyroelectric sensor passage is carbon dioxide Measurement channel, another passage is reference channel, the 3rd steam Measurement channel; In each passway, optical filter is all installed by place, and wherein the optical filter of carbon dioxide Measurement channel is 4.26 μm, and the optical filter of steam Measurement channel is 1.37 μm, and the optical filter of reference channel is 3.95 μm; Control the bright sudden strain of a muscle of infrared light module periodicity and carry out input, method is as follows:

1) carry out timing signal, determine peak value and the valley of each port according to the data of three channel acquisition;

2) extract the peak-to-peak value of steam Measurement channel voltage and the peak-to-peak value of reference channel voltage, the waveform that both data are subtracted each other is demarcated, obtains the Voltage Peak peak value of the correspondence in different vapour concentration;

3) extract the peak-to-peak value of carbon dioxide concentration measurement channel voltage and the peak-to-peak value of reference channel voltage, the waveform that both data are subtracted each other is demarcated, obtain different gas concentration lwevel containing Voltage Peak peak value corresponding under influence of moisture;

4) integrating step (3) and (4), according to langbobier law, obtain different gas concentration lwevel not containing the matched curve of Voltage Peak peak value corresponding under influence of moisture;

5) when measuring in real time, determine peak value and the valley of each port according to the data of three channel acquisition, the waveform exported according to each port obtains concentration value and the vapour concentration now of corresponding carbon dioxide.

Known according to non-infrared spectroscopy principle, steam Absorbable rod part infrared light, can have an impact to carbon dioxide absorption infrared light intensity, cause carbon dioxide concentration measurement to have deviation.And the present invention can record each people breathes out the content of steam, and then affect the amount of gas concentration lwevel according to target experimental verification in the past, and then compensate for current carbon dioxide concentration measurement, obtain carbon dioxide concentration value accurately.

Accompanying drawing explanation

Fig. 1 people breathes out last CO ₂monitoring modular.

Embodiment

Gas concentration lwevel monitoring method of the present invention proposes for main stream-type gas-monitoring, provides the monitoring system composition that the present invention is suitable for below.

This main stream-type breathing carbon dioxide density monitoring system is made up of host computer and monitoring modular.Host computer is multi-purpose computer or patient monitor.As shown in Figure 1,1 represents light source module to monitoring modular, and 2 represent sensor assembly, and 3 is transparent glass sheet, and 4 is gas passage.Wherein 3 and 4 form pipeline adapter, can be directly installed on people's breath official road.And light source module divides the both sides standing in pipeline adapter.Sensor assembly has three passages, and in each passway, optical filter is all installed by place, and wherein the optical filter of CO2 passage is 4.26 μm, and the optical filter of vapor channel is 1.37 μm, and the optical filter of reference channel is 3.95 μm. and its operating process is:

(1) power-on self-test, when passing through without pipeline airless, opening power, checks that whether sensor three passage waveforms are normal.

(2) in waveform pipeline vent flow under normal circumstances, now waveform can be produced at sensor three passages, wait for that waveform stabilization starts analog to digital conversion, Wave data is transferred to host computer, and host computer determines peak value and the valley of each port according to the method for the data acquisition glide filter collected.

(3) first processing module sends square-wave signal and controls the intermittent bright sudden strain of a muscle of light source module, when passing into a certain amount of CO2 concentration, three groups of sinusoidal signals will be exported at sensor assembly three groups of passages, respectively carry out peak-to-peak value to the sinusoidal signal of three passages to sample, sampling continuous print 16 groups of peak-to-peak value signals.

(4) to the peak-to-peak value signal sequence that CO2 measuring junction collects, remove minimum 3 groups of data and maximum 3 groups of data totally 6 groups of data, what be averaged 10 groups of remaining data arrives last mean value D _c.

(5) to the peak-to-peak value signal sequence that steam measuring junction collects, remove minimum 3 groups of data and maximum 3 groups of data totally 6 groups of data, what be averaged 10 groups of remaining data arrives last mean value D _h.

(6) to the peak-to-peak value signal sequence that reference edge collects, remove minimum 3 groups of data and maximum 3 groups of data totally 6 groups of data, what be averaged 10 groups of remaining data arrives last mean value D _ref.

(7) according to langbobier law, the concentration C of the CO2 after influence of moisture is got rid of _cO2have in like manner known, the concentration C of steam _h2Ohave $C_{H2O}=c\·In\left(\frac{D_H}{D_{ref}}\right)+d$

(8) constant a can be tried to achieve by calibration experiment, the value of b, c, d, can matched curve be drawn, may correspond to concentration value and the vapour concentration now of CO2 according to the known waveform exported by sensor of matched curve.

Claims (1)

1. the gas concentration lwevel detection method of a main stream-type reduction moisture effects, the infrared light module adopted and sensor detection module are placed in the two ends of pipeline adapter respectively, triple channel pyroelectric sensor passage is carbon dioxide Measurement channel, another passage is reference channel, the 3rd steam Measurement channel; In each passway, optical filter is all installed by place, and wherein the optical filter of carbon dioxide Measurement channel is 4.26 μm, and the optical filter of steam Measurement channel is 1.37 μm, and the optical filter of reference channel is 3.95 μm; Control the bright sudden strain of a muscle of infrared light module periodicity and carry out input, method is as follows:

1) carry out timing signal, determine peak value and the valley of each port according to the data of three channel acquisition;

2) extract the peak-to-peak value of steam Measurement channel voltage and the peak-to-peak value of reference channel voltage, the waveform that both data are subtracted each other is demarcated, obtains the Voltage Peak peak value of the correspondence in different vapour concentration;

3) extract the peak-to-peak value of carbon dioxide concentration measurement channel voltage and the peak-to-peak value of reference channel voltage, the waveform that both data are subtracted each other is demarcated, obtain different gas concentration lwevel containing Voltage Peak peak value corresponding under influence of moisture;

4) integrating step (3) and (4), according to langbobier law, obtain different gas concentration lwevel not containing the matched curve of Voltage Peak peak value corresponding under influence of moisture;

5) when measuring in real time, determine peak value and the valley of each port according to the data of three channel acquisition, the waveform exported according to each port obtains concentration value and the vapour concentration now of corresponding carbon dioxide.