CN117470795B - Non-spectroscopic infrared gas sensor and gas testing method thereof - Google Patents
Non-spectroscopic infrared gas sensor and gas testing method thereof Download PDFInfo
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- 238000012360 testing method Methods 0.000 title claims abstract description 18
- 238000001514 detection method Methods 0.000 claims abstract description 33
- 235000013405 beer Nutrition 0.000 claims abstract description 21
- 238000005259 measurement Methods 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 4
- 238000010521 absorption reaction Methods 0.000 claims description 21
- 230000003287 optical effect Effects 0.000 claims description 17
- 101100162020 Mesorhizobium japonicum (strain LMG 29417 / CECT 9101 / MAFF 303099) adc3 gene Proteins 0.000 claims description 13
- 238000013031 physical testing Methods 0.000 abstract description 2
- 230000035945 sensitivity Effects 0.000 abstract description 2
- 238000010998 test method Methods 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 88
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 56
- 230000002093 peripheral effect Effects 0.000 description 17
- 238000009529 body temperature measurement Methods 0.000 description 7
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 5
- 229910002091 carbon monoxide Inorganic materials 0.000 description 5
- 101100434411 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) ADH1 gene Proteins 0.000 description 4
- 101150102866 adc1 gene Proteins 0.000 description 4
- 239000003345 natural gas Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 101150042711 adc2 gene Proteins 0.000 description 2
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- 230000007613 environmental effect Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007084 catalytic combustion reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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Abstract
The invention relates to the technical field of physical testing, and discloses a non-spectroscopic infrared gas sensor and a gas testing method thereof, wherein the sensor comprises an infrared detection gas chamber, the infrared detection gas chamber comprises a transmitting end, a gas chamber and a receiving end, the receiving end comprises a reference channel and a measuring channel, the reference channel outputs reference voltage, and the measuring channel outputs measuring voltage; the MCU control unit is used for calculating the emergent light intensity of the infrared detection air chamber according to the reference voltage and the measurement voltage, and then calculating the concentration of the gas to be detected according to the lambert beer law; the method comprises the following steps: the sensor is respectively placed in air, gas which is the same as the gas to be measured and has known concentration, and zero calibration is carried out on the sensor; and testing the concentration of the gas to be tested. The sensor provided by the invention has the advantages of high reliability, high sensitivity, low cost and high accuracy of the test method.
Description
Technical Field
The invention relates to the technical field of physical testing, in particular to a non-spectroscopic infrared gas sensor and a gas testing method thereof.
Background
Natural gas is one of the living energy sources, the safety of the natural gas is closely related to life and property, and the leakage of the natural gas can cause serious consequences of damaging the environment and damaging the personal and property safety. The existing household natural gas detection device mainly adopts catalytic combustion type products, and has the problems of poor stability, short correction period, easiness in poisoning, necessity of working in an aerobic environment, short service life and the like although the price is low. There is therefore a need for a gas sensor that is highly reliable, highly sensitive and low cost.
Disclosure of Invention
The invention aims to design a gas sensor with high reliability, high sensitivity and low cost, and provides a non-spectroscopic infrared gas sensor and a gas testing method thereof.
In order to achieve the above object, the embodiment of the present invention provides the following technical solutions:
a non-spectroscopic infrared gas sensor comprising:
the infrared detection air chamber comprises a transmitting end, an air chamber and a receiving end, when the air chamber contains the gas to be detected, the transmitting end transmits infrared light to the receiving end according to the high level transmitted by the MCU control unit, the receiving end comprises a reference channel and a measuring channel, the reference channel transmits reference voltage to the MCU control unit, and the measuring channel transmits measuring voltage to the MCU control unit;
and the MCU control unit is used for calculating the emergent light intensity of the infrared detection air chamber according to the reference voltage and the measurement voltage, and then calculating the concentration of the gas to be detected according to the lambert beer law.
The circuit also comprises an operational amplifier peripheral circuit;
the reference channel sends reference voltage to the MCU control unit through the operational amplifier peripheral circuit, and the operational amplifier peripheral circuit is used for amplifying the reference voltage output by the reference channel;
the measuring channel sends measuring voltage to the MCU control unit through the operational amplifier peripheral circuit, and the operational amplifier peripheral circuit is used for amplifying the measuring voltage output by the measuring channel.
The reference circuit is connected with the input end of the operational amplifier peripheral circuit and is used for providing reference voltage for the operational amplifier peripheral circuit.
The infrared detection device also comprises a temperature measurement peripheral circuit, wherein the temperature measurement peripheral circuit comprises a circuit connected between the reference circuit and an ADC3 port of the MCU control unit and a circuit connected between a receiving end of the infrared detection air chamber and an ADC0 port of the MCU control unit;
the MCU control unit calculates the ambient temperature of the infrared detection air chamber according to the voltage of the ADC0 port and the voltage of the ADC3 port:
；
wherein T is the ambient temperature of the infrared detection air chamber; under the same environment, V_ADC0 is the voltage value received by the ADC0 port of the MCU control unit; V_ADC3 is the voltage value received by the ADC3 port of the MCU control unit;is a known fixed coefficient.
The infrared detection device further comprises an infrared lamp driving unit, the MCU control unit sends high level to the sending end of the infrared detection air chamber through the infrared lamp driving unit, and sufficient driving current is provided for the infrared lamp through the infrared lamp driving unit.
The gas testing method of the non-spectroscopic infrared gas sensor comprises the following steps:
step 1, respectively placing the sensor into air and gas which is the same as the gas to be detected and has known concentration, and carrying out zero calibration on the sensor based on the lambert beer law to obtain the intensity of incident light, absorption coefficient and optical path length after zero calibration;
step 2, acquiring the ambient temperature of an infrared detection air chamber when the sensor is placed in the air during zero calibration;
and 3, calculating to obtain the concentration of the gas to be measured based on the lambert beer law by combining the incident light intensity, the absorption coefficient, the optical path length and the ambient temperature in the air which are obtained after zero calibration and the ambient temperature when the gas to be measured is tested.
The step 1 specifically comprises the following steps:
the sensor is placed in air according to lambert beer's law:
（1）；
then the sensor is put into the gas which is the same as the gas to be measured and has the known concentration of x C According to lambert beer's law there are:
（2）；
wherein I is 0 Is the intensity of incident light; i LOW For the intensity of the emergent light in the air environment, I C The intensity of emergent light in the gas environment to be detected; x is x LOW Is the concentration of the gas to be measured in the air environment, x C The concentration of the gas to be measured in the gas environment to be measured; k is the absorption coefficient; l is the optical path length;
I LOW equal to the ratio of the measured voltage V_ACT to the reference voltage V_REF in the air environment, I C The ratio of the measured voltage V_ACT to the reference voltage V_REF is equal to the gas environment to be measured; due to I LOW 、I CAL From the measurements, x LOW 、x CAL Also known are the combination of (1) and (2), and the I after zero calibration is calculated 0 And the product kl of the absorption coefficient k after zero calibration and the optical path length l.
The step 2 specifically comprises the following steps:
during zero calibration, the ambient temperature is acquired:
（3）；
wherein T is LOW Calibrating the ambient temperature in the air environment for zero calibration; under the same environment, V_ADC0 is the voltage value received by the ADC0 port of the MCU control unit; V_ADC3 is ADC3 of MCU control unitA voltage value received by the port;is a known fixed coefficient.
The step 3 specifically comprises the following steps:
when testing the gas to be tested, there is a corresponding ratio:
（4）；
wherein FA is the absorption rate; i 0 The intensity of the incident light obtained after zero calibration is obtained; i is the intensity of emergent light, I=V_ACT/V_REF, V_ACT is the measurement voltage received by the MCU control unit, and V_REF is the reference voltage received by the MCU control unit;
combining lambert beer's law with equation (4), we get:
（5）；
（6）；
（7）；
in the formula (5), kl is the product of the absorption coefficient k after zero calibration and the optical path length l; in formula (6), T LOW Calibrating the ambient temperature measured in the air environment for zero calibration; in the formula (7), T is the ambient temperature when the gas to be measured is measured,the V_ADC0 is a voltage value received by an ADC0 port of the MCU control unit when the gas to be measured is measured, wherein the voltage value is a known fixed coefficient; V_ADC3 is the voltage value received by the ADC3 port of the MCU control unit when the gas to be measured is measured.
Compared with the prior art, the invention has the beneficial effects that:
(1) The infrared detection air chamber takes the infrared light with specific wavelength absorbed by the gas to be detected as the detection principle, the infrared light is non-spectroscopic infrared light, the structure and the light source driving are simple, and the back-end processing circuit is simple because the light source does not split light and the emergent light power is high.
(2) The infrared detection air chamber is a double channel, namely a reference channel and a measurement channel, wherein the reference channel is not influenced by air in the air chamber, and a fixed reference voltage is output to the MCU control unit; the measuring voltage output by the measuring channel to the MCU control unit changes along with the concentration change of the gas to be measured in the gas chamber, the MCU control unit uses the ratio of the measuring voltage to the reference voltage as the emergent light intensity of the infrared detection gas chamber, so that the concentration of the gas to be measured is calculated, instead of directly calculating the concentration of the gas to be measured according to the voltage output by the infrared detection gas chamber in a traditional mode, the measuring method is more reliable in comparison with the traditional mode, which considers the basic voltage of the whole circuit when calculating the concentration of the gas to be measured.
(3) Before testing a gas to be tested, the invention respectively puts the sensor into air and gas with the same type and known concentration as the gas to be tested based on lambert's law, and performs zero calibration on the sensor to obtain the intensity I of incident light after zero calibration 0 And the product of the absorption coefficient k and the optical path length l, the zero-calibrated I 0 And kl brings back lambert beer law, so that the calculated concentration value of the gas to be measured is more accurate.
(4) Before testing a gas to be tested, the invention acquires the ambient temperature of the infrared detection air chamber when the sensor is placed in the air during zero calibration of the sensor, and also acquires the ambient temperature of the infrared detection air chamber during formal testing of the gas to be tested, and compensates the concentration value of the gas to be tested by using the ambient temperature, thereby compensating the error caused by temperature change on the measurement of the sensor.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of a sensor module of the present invention;
FIG. 2 is a schematic diagram of a sensor circuit of the present invention;
FIG. 3 is a flow chart of the method of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without making any inventive effort, are intended to be within the scope of the present invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. Also, in the description of the present invention, the terms "first," "second," and the like are used merely to distinguish one from another, and are not to be construed as indicating or implying a relative importance or implying any actual such relationship or order between such entities or operations. In particular, the terms "connected," "coupled," and the like may be used to connect elements or devices directly or indirectly via other elements or devices.
The invention is realized by the following technical scheme, as shown in fig. 1, and provides a non-spectroscopic infrared gas sensor which comprises an infrared detection gas chamber, an MCU control unit, a temperature measurement peripheral circuit, an operational amplifier peripheral circuit and a reference circuit. The infrared detection air chamber comprises a sending end, an air chamber and a receiving end, wherein the sending end is an infrared lamp, the receiving end is two channels realized by two detectors, one channel is a reference channel, and the other channel is a measurement channel.
The infrared detection air chamber takes the infrared light with specific wavelength absorbed by the gas to be detected as the detection principle, the infrared light is non-spectroscopic infrared light, the structure and the light source driving are simple, and the back-end processing circuit is simple because the light source does not split light and the emergent light power is high.
The basic principle of the scheme is as follows: the gas to be detected diffuses into the air chamber, the MCU control unit sends high and low levels to the infrared lamp to control the infrared lamp to be turned on and off, and infrared light emitted by the infrared lamp reaches a receiving end after being absorbed by the gas to be detected in the air chamber at the high level. The reference channel outputs reference voltage to the MCU control unit through the operational amplifier peripheral circuit, and the reference voltage is not influenced by the gas to be detected; the measuring channel outputs measuring voltage to the MCU control unit through the operational amplifier peripheral circuit, and the measuring voltage is influenced by the gas to be measured. And the MCU control unit calculates the emergent light intensity of the infrared detection air chamber according to the reference voltage and the measured voltage. The temperature measurement peripheral circuit is used for outputting temperature measurement voltage to the MCU control unit according to the ambient temperature of the infrared detection air chamber, and the MCU control unit calculates the ambient temperature of the infrared detection air chamber according to the temperature measurement voltage. And finally, the MCU control unit obtains the concentration of the gas to be detected according to the output light intensity of the infrared detection air chamber, and performs temperature compensation on the concentration of the gas to be detected by using the ambient temperature.
With continued reference to fig. 1, the present sensor further includes an infrared lamp driving unit, through which the MCU control unit sends high and low levels to the infrared lamp. Since the driving current outputted by the MCU control unit is small, the infrared lamp driving unit is arranged between the MCU control unit and the infrared lamp and is used for providing enough driving current for the infrared lamp, so that the infrared lamp can receive a high level of 5V.
In detail, as shown in fig. 2, the infrared lamp driving unit is a power chip U4, and a GPIO port of the MCU control unit is connected to an EN pin of the power chip U4, where the GPIO port is configured to output a high level or a low level to the power chip U4. The VOUT pin of power chip U4 is connected with the infrared lamp for output 5V's high level or 0V's low level to the infrared lamp.
The receiving end of the infrared detection air chamber adopts a thermopile sensor and consists of a plurality of thermocouples connected in series and/or in parallel (only schematic diagram in fig. 2). The receiving end comprises a reference channel (A in fig. 2) and a measurement channel (B in fig. 2), the operational amplifier peripheral circuit comprises a first operational amplifier U1 and a second operational amplifier U2, and the reference circuit comprises a third operational amplifier U3. The reference channel is connected with an ADC1 port of the MCU control unit through a first operational amplifier U1, and the ADC1 port receives a reference voltage V_REF; the measuring channel is connected with an ADC2 port of the MCU control unit through a second operational amplifier U2, and the ADC2 port receives the measuring voltage V_ACT.
The forward input end of the first operational amplifier U1 is connected with the reference channel, the reverse input end is connected with the output end of the third operational amplifier U3, and the reference voltage 3.3V is fixedly output by the third operational amplifier U3, and the voltage output by the reference channel is not influenced by the gas to be detected, so that the voltage of the forward input end and the voltage of the reverse input end of the first operational amplifier U1 are both fixed, the voltage of the output end of the first operational amplifier U1 is also fixed, namely, no matter whether the gas to be detected exists in the air chamber or not, and no matter what concentration of the gas to be detected exists in the air chamber, the reference voltage V_REF received by an ADC1 port of the MCU control unit is always unchanged.
The positive input end of the second operational amplifier U2 is connected with the measuring channel, the negative input end is connected with the output end of the third operational amplifier U3, the third operational amplifier U3 fixedly outputs a reference voltage of 3.3V, but the voltage output by the measuring channel is influenced by the concentration of the gas to be measured in the air chamber, when the gas to be measured such as methane exists in the air chamber, the measuring channel outputs the voltage to the positive input end of the second operational amplifier U2, and after differential operational amplification, the measuring voltage V_ACT output by the second operational amplifier U2 is also influenced by the concentration of the gas to be measured.
The MCU control unit takes the ratio of the measurement voltage V_ACT to the reference voltage V_REF as the emergent light intensity I=V_ACT/V_REF of the infrared detection air chamber, and the ratio is I=I based on the lambert law 0 e -klx Wherein I is the intensity of the emitted light, I 0 For the intensity of incident light, k is the absorption coefficient, l is the optical path length (distance from the transmitting end to the receiving end), and x is the concentration of the gas to be measured. Intensity of incident light I 0 The voltage output by the power chip U4 can be known, the output light intensity I can be known by the voltage signal received by the MCU, and k and l are known, so that the concentration x of the gas to be measured can be calculated according to lambert beer's law.
However, there is a certain error in each sensor when leaving the factory, and in particular, when aiming at different types of gases to be measured, the measured errors are also irregular. Before formally testing one gas, the sensor is respectively placed in air and gas with known concentration, and the incident light intensity I is measured 0 And performing zero calibration on the absorption coefficient k and the optical path length l to improve the accuracy of detecting the concentration of the gas to be detected.
For example, before testing methane, the calibration mode of the sensor is as follows:
the sensor was first placed in air (0% vol methane) and there was, according to lambert beer's law:
（1）；
the sensor was then placed in methane (5% vol methane) according to lambert beer's law:
（2）；
wherein I is LOW For the intensity of the emergent light in the air environment, I CAL Is the intensity of the emergent light in the methane environment; i 0 For incident light intensity, the intensity is equal in both air and methane environments; x is x LOW Is the concentration of methane in the air environment, x CAL Is the concentration of methane in the methane environment. I LOW Equal to the ratio of the measured voltage V_ACT to the reference voltage V_REF in the air environment, I CAL Equal to the ratio of the measured voltage v_act to the reference voltage v_ref at methane environment. Due to I LOW 、I CAL From measurements, x LOW 、x CAL Also known, therefore, are combinations of (1) and (2) to calculate I 0 And kl (k, l are expressed as products), thus deriving I 0 And kl is the value after the zero calibration operation, and compared with the value of the concentration of the gas to be measured which is finally obtained without the zero calibration operation, the value of the gas to be measured is more accurate.
It will be readily appreciated that the sensor may be placed in methane before the sensor is placed in air. If the type of the gas to be detected is carbon monoxide, respectively putting the sensor into air (0% VOL carbon monoxide) and carbon monoxide (10% VOL carbon monoxide), and then calculating the I after zero correction and calibration 0 And kl, the concentration of carbon monoxide can be customized.
Referring to fig. 2, the temperature measuring peripheral circuit includes a line connected between the third operational amplifier U3 of the reference circuit and the ADC3 port of the MCU control unit, and a line connected between the receiving end of the infrared detection air chamber and the ADC0 port of the MCU control unit. The reference voltage 3.3V output by the third operational amplifier U3 is output to the ADC3 port of the MCU control unit and is not influenced by the ambient temperature of the air chamber; the voltage received at the ADC1 port is affected by the ambient temperature of the air chamber.
Further obtaining the temperature T during the zero calibration LOW ：
（3）；
Wherein T is LOW The ambient temperature when in an air environment; under the same environment, V_ADC0 is the voltage value received by the ADC0 port of the MCU control unit; V_ADC3 is a voltage value received by an ADC3 port of the MCU control unit, and V_ADC3 is not affected by any environment;is a known fixed coefficient.
When testing the gas to be tested, there is a corresponding ratio:
（4）；
wherein FA is the absorption rate; i 0 The intensity of the incident light obtained after zero calibration is obtained; i is the intensity of the emitted light, i=v_act/v_ref, v_act is the measurement voltage received by the MCU control unit, and v_ref is the reference voltage received by the MCU control unit.
Combining lambert's law with equation (4), one can obtain:
（5）；
after zero calibration is finished, methane can be tested in real time, and after methane enters the air chamber, the combined formula (4) and formula (5) can be obtained:
；
because this scheme has set up temperature measurement peripheral circuit, consequently this scheme is when finally calculating gas concentration x that awaits measuring, with temperature compensation into:
（6）；
in formula (6), T LOW Calibrating the ambient temperature measured in the air for zeroing; t is the ambient temperature when measuring the gas to be measured, the acquisition mode and T LOW The same, namely:
（7）；
in the formula (7), T is the ambient temperature when the gas to be measured is measured,the V_ADC0 is a voltage value received by an ADC0 port of the MCU control unit when the gas to be measured is measured, wherein the voltage value is a known fixed coefficient; V_ADC3 is the voltage value received by the ADC3 port of the MCU control unit when the gas to be measured is measured.
Therefore, the scheme is characterized in that the environmental temperature is further added when the concentration of the gas to be measured is measured in the formula (6), so that the influence of the environmental temperature on the measurement is compensated, and the measurement result is more accurate.
Based on the above sensor, please refer to fig. 3, the present disclosure further provides a gas testing method of a non-spectroscopic infrared gas sensor, which includes the following steps:
and step 1, respectively placing the sensor into air and gas which is the same as the gas to be detected and has known concentration, and carrying out zero calibration on the sensor based on the lambert beer law to obtain the incident light intensity, the absorption coefficient and the optical path length.
Lambert beer's law is i=i 0 e -klx Wherein I is the intensity of the emitted light, I 0 For the intensity of incident light, k is the absorption coefficient, l is the optical path length, and x is the concentration of the gas to be measured. For example, if the type of gas to be measured is methane, the sensor is placed in air (0% vol methane), and according to lambert beer's law:
（1）；
the sensor was then placed in methane (5% vol methane) according to lambert beer's law:
（2）；
wherein I is LOW For the intensity of the emergent light in the air environment, I CAL Is the intensity of the emergent light in the methane environment; i 0 For incident light intensity, the intensity is equal in both air and methane environments; x is x LOW Is the concentration of methane in the air environment, x CAL Is the concentration of methane in the methane environment. I LOW Equal to the ratio of the measured voltage V_ACT to the reference voltage V_REF in the air environment, I CAL Equal to the ratio of the measured voltage v_act to the reference voltage v_ref at methane environment. Due to I LOW 、I CAL From measurements, x LOW 、x CAL Also known, therefore, are combinations of (1) and (2) to calculate I 0 And kl, thus derived I 0 And kl is the value after the zero calibration operation, and compared with the value of the concentration of the gas to be measured which is finally obtained without the zero calibration operation, the value of the gas to be measured is more accurate.
And 2, acquiring the ambient temperature of the infrared detection air chamber when the sensor is placed in the air during zero calibration.
（3）；
Wherein T is LOW Calibrating the ambient temperature in the air environment for zero calibration; under the same environment, V_ADC0 is the voltage value received by the ADC0 port of the MCU control unit; V_ADC3 is a voltage value received by an ADC3 port of the MCU control unit, and V_ADC3 is not affected by any environment;is a known fixed coefficient.
And 3, calculating to obtain the concentration of the gas to be measured based on the lambert beer law by combining the incident light intensity, the absorption coefficient, the optical path length and the ambient temperature in the air which are obtained after zero calibration and the ambient temperature when the gas to be measured is tested.
When testing the gas to be tested, there is a corresponding ratio:
（4）；
wherein FA is the absorption rate; i 0 The intensity of the incident light obtained after zero calibration is obtained; i is the intensity of the emitted light, i=v_act/v_ref, v_act is the measurement voltage received by the MCU control unit, and v_ref is the reference voltage received by the MCU control unit.
Combining lambert's law with equation (4), one can obtain:
（5）；
（6）；
（7）；
in the formula (5), kl is the product of the absorption coefficient k after zero calibration and the optical path length l; in formula (6), T LOW Calibrating the ambient temperature measured in the air environment for zero calibration; in the formula (7), T is the ambient temperature when the gas to be measured is measured,the V_ADC0 is a voltage value received by an ADC0 port of the MCU control unit when the gas to be measured is measured, wherein the voltage value is a known fixed coefficient; V_ADC3 is the voltage value received by the ADC3 port of the MCU control unit when the gas to be measured is measured.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (1)
1. The gas testing method of the non-spectroscopic infrared gas sensor is characterized by comprising the following steps of: the method comprises the following steps:
step 1, respectively placing the sensor into air and gas which is the same as the gas to be detected and has known concentration, and carrying out zero calibration on the sensor based on the lambert beer law to obtain the intensity of incident light, absorption coefficient and optical path length after zero calibration;
the step 1 specifically comprises the following steps:
the sensor is placed in air according to lambert beer's law:
（1）；
then the sensor is put inIn the same type of gas as the gas to be measured, and with a known concentration of x C According to lambert beer's law there are:
（2）；
wherein I is 0 Is the intensity of incident light; i LOW For the intensity of the emergent light in the air environment, I C The intensity of emergent light in the gas environment to be detected; x is x LOW Is the concentration of the gas to be measured in the air environment, x C The concentration of the gas to be measured in the gas environment to be measured; k is the absorption coefficient; l is the optical path length;
I LOW equal to the ratio of the measured voltage V_ACT to the reference voltage V_REF in the air environment, I C The ratio of the measured voltage V_ACT to the reference voltage V_REF is equal to the gas environment to be measured; due to I LOW 、I CAL From the measurements, x LOW 、x CAL Also known are the combination of (1) and (2), and the I after zero calibration is calculated 0 And the product kl of the absorption coefficient k after zero calibration and the optical path length l;
step 2, acquiring the ambient temperature of an infrared detection air chamber when the sensor is placed in the air during zero calibration;
the step 2 specifically comprises the following steps:
during zero calibration, the ambient temperature is acquired:
（3）；
wherein T is LOW Calibrating the ambient temperature in the air environment for zero calibration; under the same environment, V_ADC0 is the voltage value received by the ADC0 port of the MCU control unit; V_ADC3 is the voltage value received by the ADC3 port of the MCU control unit;is a known fixed coefficient;
step 3, calculating to obtain the concentration of the gas to be measured based on the lambert beer law and by combining the incident light intensity, the absorption coefficient, the optical path length and the ambient temperature in the air which are obtained after zero calibration and the ambient temperature when the gas to be measured is tested;
the step 3 specifically comprises the following steps:
when testing the gas to be tested, there is a corresponding ratio:
（4）；
wherein FA is the absorption rate; i 0 The intensity of the incident light obtained after zero calibration is obtained; i is the intensity of emergent light, I=V_ACT/V_REF, V_ACT is the measurement voltage received by the MCU control unit, and V_REF is the reference voltage received by the MCU control unit;
combining lambert beer's law with equation (4), we get:
（5）；
（6）；
（7）；
in the formula (5), kl is the product of the absorption coefficient k after zero calibration and the optical path length l; in formula (6), T LOW Calibrating the ambient temperature measured in the air environment for zero calibration; in the formula (7), T is the ambient temperature when the gas to be measured is measured,the V_ADC0 is a voltage value received by an ADC0 port of the MCU control unit when the gas to be measured is measured, wherein the voltage value is a known fixed coefficient; V_ADC3 is the voltage value received by the ADC3 port of the MCU control unit when the gas to be measured is measured.
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