CN214374280U

CN214374280U - Gas concentration detection device

Info

Publication number: CN214374280U
Application number: CN202120304569.2U
Authority: CN
Inventors: 武斌; 申涛
Original assignee: Shenzhen Meisi Xianrui Electronic Co ltd
Current assignee: Shenzhen Meisi Xianrui Electronic Co ltd
Priority date: 2021-02-03
Filing date: 2021-02-03
Publication date: 2021-10-08
Anticipated expiration: 2031-02-03

Abstract

The utility model discloses a gas concentration detection device, including light source module, air chamber module, infrared thermopile module and signal processing module, light source module and infrared thermopile module are all installed on signal processing module, and the air chamber module is installed in signal processing module top. The utility model discloses a gas concentration detection device, produce infrared light and launch to the air chamber module through the light source module, utilize inside gaseous absorption infrared light and reflection infrared light to infrared thermopile module of awaiting measuring through the air chamber module, detect the infrared luminous intensity and output corresponding voltage signal to the signal processing module after being awaited measuring gaseous absorption through infrared thermopile module, calculate the gaseous concentration of awaiting measuring according to voltage signal through the signal processing module, thereby make user direct measurement gas concentration, satisfy the concentration measurement demand of different gases, it goes to study relevant principle to need not the user to expend a large amount of time again, improve project development efficiency, shorten development time.

Description

Gas concentration detection device

Technical Field

The utility model belongs to the technical field of infrared measurement, concretely relates to gas concentration detection device.

Background

When a continuous wave of infrared light passes through a certain gas, if the vibration frequency or rotation frequency of a certain group of a gas molecule is consistent with the frequency of the infrared light, the gas molecule absorbs energy and transits from a ground state energy level to an energy level with higher energy, the infrared light at the frequency is absorbed to form an absorption peak, and an infrared absorption spectrum is generated in the wavelength range of 0.78-1000 um. Because the chemical bonds of atom combination in different molecules are different, and the energy required by the transition of different chemical bonds is different, the infrared absorption spectra of different gases are also different, for example, CO2 gas easily absorbs infrared light with a wavelength of 4.26um, CH4 gas easily absorbs infrared light with a wavelength of 3.40um, and SF6 gas easily absorbs infrared light with a wavelength of 10.60 um. When the infrared wavelength is coincident with the absorption spectrum of the gas to be measured, the infrared energy is absorbed, the greater the gas concentration is, the greater the attenuation of light is, and therefore, the gas concentration is measured by measuring the attenuation of infrared rays by the gas.

The working process of measuring the gas concentration by infrared rays is as follows: the infrared light source radiates wide-spectrum infrared light, the infrared light passes through a gas to be detected in a specially designed gas chamber with high reflectivity, the gas passes through a specific narrow-band filter on the infrared thermopile sensor and reaches an infrared thermopile chip inside the sensor, the infrared thermopile chip generates corresponding voltage signals to be output according to the Seebeck effect after receiving infrared light signals, an operational amplifier with low noise and zero temperature drift is used for amplifying output signals of the infrared thermopile sensor, the amplified signals are converted into digital signals through an analog-to-digital conversion chip, algorithm calculation is carried out by using the beer Lambert law which accords with the gas absorption relation of NDIR, and finally the concentration of the gas to be detected is obtained.

However, this working process is complicated and difficult to understand, a user needs to select a special infrared light source according to the infrared absorption spectrum of the gas to be measured, the user needs to design a special gas chamber structure with high reflection property, the user needs to reasonably design a signal processing circuit according to the output characteristics of the infrared thermopile sensor, the user needs to design a processing algorithm according to the beer-lambert law of the NDIR gas absorption relationship to calculate the gas concentration, and a lot of time and effort are needed to be spent on learning, so that the development efficiency of user projects is seriously affected.

SUMMERY OF THE UTILITY MODEL

In order to solve the problem, the utility model provides a gas concentration detection device need not the user and expends a large amount of time again and goes to study relevant principle, improves project development efficiency, shortens development time.

The utility model adopts the technical proposal that:

the utility model provides a gas concentration detection device, is including the light source module that is used for producing the infrared light, be used for utilizing inside gas that awaits measuring to absorb the infrared light and reflect the air chamber module of infrared light, be used for detecting by the infrared luminous intensity of gas absorption back that awaits measuring and output corresponding voltage signal's infrared thermopile module and be used for calculating the signal processing module of the gas concentration that awaits measuring according to voltage signal, light source module and infrared thermopile module are all installed on signal processing module, the air chamber module is installed in signal processing module top.

Preferably, the air chamber module includes an air chamber cover unit and an air chamber bottom plate unit, and the air chamber cover unit is mounted on the air chamber bottom plate unit.

Preferably, the air chamber cover unit comprises an air chamber cover body, an air inlet, an air outlet and a reflection assembly for reflecting infrared rays, wherein the air inlet is formed above the air chamber cover body, the air outlet is formed in one side, away from the air inlet, of the air chamber cover body, waterproof breathable films are arranged on the air inlet and the air outlet, and the reflection assembly is installed at the top end of the inner cavity of the air chamber cover body.

Preferably, the reflection assembly includes a first reflection member, a second reflection member and a third reflection member, and the first reflection member, the second reflection member and the third reflection member are all installed at the top end inside the air chamber cover body and are arranged in a triangular direction.

Preferably, the air chamber bottom plate unit comprises an air chamber bottom plate body, a first placing hole for placing the light source module and a second placing hole for placing the infrared thermopile module, and the first placing hole and the second placing hole are both installed on the air chamber bottom plate body.

Preferably, the infrared thermopile module includes a first optical filter, a first sensor cap, a first infrared thermopile chip, a first NTC chip and a first base, the first optical filter is installed at a round hole on the upper portion of the first sensor cap, the first infrared thermopile chip and the first NTC chip are both installed on a round table on the upper portion of the first base, and the edge of the first sensor cap is hermetically welded with the edge of the first base.

Preferably, the signal processing module includes an infrared thermopile analog sensor U1, a first operational amplifier U2, a first analog-to-digital converter U3 and a first single chip microcomputer U4, a first pin of the infrared thermopile analog sensor U1 is connected in series with a second resistor R2 and then connected in parallel with a third pin of a first operational amplifier U2 and one end of a first capacitor C1, a second pin of the infrared thermopile analog sensor U1 is connected in parallel with one end of a fourth resistor R4 and one end of a fifth resistor R5, the other end of the fourth resistor R4 is electrically connected with a second pin of the first analog-to-digital converter U3, the other end of the fifth resistor R5 is connected with a power supply VCC, a third pin of the infrared thermopile analog sensor U1 is connected in parallel with a reference voltage VREF and a fourth pin of the first analog-to-digital converter U3, and a fourth pin of the infrared thermopile analog sensor U1 is grounded;

a second pin of the first operational amplifier U2 is connected in parallel with one end of a first resistor R1, one end of a third resistor R3 and one end of a second capacitor C2, the other end of the first resistor R1 is connected with a reference voltage VERF, the other end of the third resistor R3 and the other end of the second capacitor C2 are both electrically connected with a sixth pin of the first operational amplifier U2 and a common connection end of a first pin of the first analog-to-digital converter U3, a fourth pin of the first operational amplifier U2 and the other end of the first capacitor C1 are both grounded, a seventh pin of the first operational amplifier U2 is connected in parallel with one end of the third capacitor C3, one end of the fourth capacitor C4 and a power supply VCC, and the other end of the third capacitor C3 and the other end of the fourth capacitor C4 are both grounded;

a third pin and a fifth pin of the first analog-to-digital converter U3 are both grounded, a sixth pin of the first analog-to-digital converter U3 is connected in parallel with a power supply VCC, one end of a sixth resistor R6, one end of a seventh resistor R7, one end of a fifth capacitor C5 and one end of a sixth capacitor C6, a seventh pin of the first analog-to-digital converter U3 is connected in parallel with the other end of a seventh resistor R7 and a fifth pin of a first single chip microcomputer U4, an eighth pin of the first analog-to-digital converter U3 is connected in parallel with the other end of a sixth resistor R6 and a fourth pin of a first single chip microcomputer U4, and a ninth pin of the first analog-to-digital converter U3, a tenth pin of the first analog-to-digital converter U3, the other end of the fifth capacitor C5 and the other end of the sixth capacitor C6 are all grounded;

the first pin of first singlechip U4 and the second pin of first singlechip U4 all connect the power VCC, the first pin of the parallelly connected first crystal oscillator Y1 of ninth pin of first singlechip U4 and the one end of seventh electric capacity C7, the tenth pin of the parallelly connected first singlechip U4 of second pin of first crystal oscillator Y1 and the one end of eighth electric capacity C8, the other end of seventh electric capacity C7 and the other end of eighth electric capacity C8 all ground connection, the forty-seventh pin and the forty-eighth pin of first singlechip U4 all ground connection.

Preferably, the infrared thermopile module includes a second optical filter, a third optical filter, a second sensor cap, a second infrared thermopile chip, a third infrared thermopile chip, a second NTC chip and a second base, the second optical filter and the third optical filter are respectively installed at an opening on the upper portion of the second sensor cap, the second infrared thermopile chip, the third infrared thermopile chip and the second NTC chip are all installed on a circular table on the upper portion of the second base, the second infrared thermopile chip and the third infrared thermopile chip respectively correspond to the second optical filter and the third optical filter, and the edge of the second sensor cap is hermetically welded to the edge of the second base.

Preferably, the signal processing module comprises a dual-channel infrared thermopile sensor U5, a second operational amplifier U6, a third operational amplifier U7, a second analog-to-digital converter U8 and a second single chip microcomputer U9, a fourth pin of the dual-channel infrared thermopile sensor U5 is grounded, a first pin of the dual-channel infrared thermopile sensor U5 is connected with one end of a seventeenth resistor R17 and a second pin of the second analog-to-digital converter U8 in parallel, the other end of the seventeenth resistor R17 is connected with a power source VCC, a second pin of the dual-channel infrared thermopile sensor U5 is electrically connected with a third pin of the second operational amplifier U6 after being connected with an eighteenth resistor R18 in series, and a third pin of the dual-channel infrared thermopile sensor U5 is electrically connected with a third pin of the third operational amplifier U7 after being connected with a nineteenth resistor R19 in series;

a second pin of the second operational amplifier U6 is connected in parallel with one end of a twelfth resistor R12 and one end of a fourteenth resistor R14, a second pin of the third operational amplifier U7 is connected in parallel with one end of an eleventh resistor R11 and one end of a thirteenth resistor R13, the other end of the eleventh resistor R11 and the other end of the twelfth resistor R12 are both electrically connected with a reference voltage Vref, a sixth pin of the second operational amplifier U6 is connected in parallel with one end of a fifteenth resistor R15 and the other end of the fourteenth resistor R14, and a sixth pin of the third operational amplifier U7 is connected in parallel with one end of a sixteenth resistor R16 and the other end of a thirteenth resistor R13;

the other end of the fifteenth resistor R15 is electrically connected to the first pin of the second analog-to-digital converter U8, the other end of the sixteenth resistor R16 is electrically connected to the fourth pin of the second analog-to-digital converter U8, the third pin and the fifth pin of the second analog-to-digital converter U8 are both grounded, the seventh pin of the second analog-to-digital converter U8 is connected in parallel with one end of a twenty-first resistor R21 and one end of a twenty-third resistor R23, the other end of the twenty-third resistor R23 is electrically connected with a fifth pin of the second singlechip U9, the eighth pin of the second analog-to-digital converter U8 is connected in parallel with one end of the twentieth resistor R20 and one end of the twenty-second resistor R22, the other end of the twenty-second resistor R22 is electrically connected with a fourth pin of the second singlechip U9, the other end of the twentieth resistor R20, the other end of the twenty-first resistor R21, the sixth pin, the ninth pin and the tenth pin of the second analog-to-digital converter U8 are all electrically connected with the power supply VCC.

Compared with the prior art, the utility model discloses a gas concentration detection device, produce infrared light and launch to the air chamber module through the light source module, utilize inside gaseous absorption infrared light and reflection infrared light to infrared thermopile module of awaiting measuring through the air chamber module, detect the infrared luminous intensity after being awaited measuring the gaseous absorption and export corresponding voltage signal to signal processing module through infrared thermopile module, calculate the gaseous concentration of awaiting measuring according to voltage signal through signal processing module, thereby make the user directly with the gaseous concentration that can measure in filling the air chamber module of awaiting measuring, satisfy the concentration measurement demand of different gases, it goes to study correlation principle to need not the user to consume the plenty of time again, the efficiency of project development is improved, the development time is shortened.

Drawings

Fig. 1 is a schematic structural diagram of a gas concentration detection apparatus provided in embodiment 1 of the present invention;

fig. 2 is a schematic structural diagram of an air chamber module of a gas concentration detection apparatus provided in embodiment 1 of the present invention;

fig. 3 is a schematic structural view of a gas chamber cover unit of a gas concentration detection apparatus according to embodiment 1 of the present invention;

fig. 4 is a schematic structural diagram of a first infrared thermopile module of a gas concentration detecting apparatus according to embodiment 1 of the present invention;

fig. 5 is a circuit diagram of a first signal processing module of a gas concentration detection apparatus according to embodiment 1 of the present invention;

fig. 6 is a schematic structural diagram of a second infrared thermopile module of a gas concentration detecting apparatus according to embodiment 1 of the present invention;

fig. 7 is a circuit diagram of a second signal processing module of the gas concentration detection apparatus according to embodiment 1 of the present invention;

fig. 8 is a flowchart of a control method of a gas concentration detection apparatus according to embodiment 2 of the present invention.

Description of the reference numerals

1-a light source module, 2-a gas chamber module, 21-a gas chamber cover unit, 211-a gas chamber cover body, 212-a gas inlet, 213-a reflection assembly, 2131-a first reflection piece, 2132-a second reflection piece, 2133-a third reflection piece, 22-a gas chamber bottom plate unit, 221-a gas chamber bottom plate body, 222-a first placement hole, 223-a second placement hole, 3-an infrared thermopile module, 31-a first optical filter, 311-a second optical filter, 312-a third optical filter, 32-a first sensor cap, 321-a second sensor cap, 33-a first infrared thermopile chip, 331-a second infrared thermopile chip, 332-a third infrared thermopile chip, 34-a first NTC chip, 341-a second NTC chip, 35-first mount, 351-second mount, 4-signal processing module.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

The embodiment of the utility model provides a gas concentration detection device, as shown in fig. 1-7, including the light source module 1 that is used for producing the infrared light, be used for utilizing inside gaseous absorption infrared light that awaits measuring and reflect the air chamber module 2 of infrared light, be used for detecting by the gaseous infrared light intensity after absorbing of awaiting measuring and export corresponding voltage signal's infrared thermopile module 3 and be used for calculating the signal processing module 4 of the gaseous concentration of awaiting measuring according to voltage signal, light source module 1 and infrared thermopile module 3 are all installed on signal processing module 4, air chamber module 2 is installed in signal processing module 4 top.

Like this, produce the infrared light and launch to air chamber module 2 through light source module 1, utilize inside gas that awaits measuring to absorb the infrared light and reflect infrared light to infrared thermopile module 3 through air chamber module 2, detect the infrared light intensity after being awaited measuring the gas absorption and output corresponding voltage signal to signal processing module 4 through infrared thermopile module 3, calculate the gas concentration that awaits measuring through signal processing module 4 according to voltage signal, thereby make the user directly fill the gas that awaits measuring in the air chamber module and can measure gas concentration, satisfy the concentration measurement demand of different gases, need not the user and again consume the plenty of time to go to study relevant principle, improve project development efficiency, shorten development time.

Infrared light is radiated out through the infrared light source module 1, and infrared light passes through the gas to be detected in the air chamber module 2, and the concentration of the gas to be detected is judged through measuring the intensity of infrared light entering the infrared thermopile module 3 by penetrating through the narrow band filter on the infrared thermopile module 3 and reaching the infrared thermopile chip inside the infrared thermopile module 3. When no gas to be detected exists in the environment, the intensity of the gas to be detected is strongest, when the gas to be detected enters the gas chamber, a part of infrared light is absorbed by the gas to be detected, the light intensity reaching the infrared thermopile module 3 is weakened, and the concentration of the gas to be detected can be calculated through calibrating the zero point and the infrared light absorption degree and the calibration of the measuring point.

The infrared light source provides wide-spectrum infrared light, and a bulb light source and an MEMS black body light source can be selected. The bulb light source is a tungsten filament packaged in a vacuum glass tube, the tungsten filament is heated by electrifying, the tungsten filament generates infrared radiation light, and the infrared radiation light radiates infrared light within 5um outwards through glass; the MEMS black body light source is generally an MEMS heater chip, black body treatment is carried out on the surface of the chip, a film heating resistor on the chip is heated after the chip is electrified, and infrared light of 1-25 um is radiated outwards uniformly. The utility model discloses be used for CO2 gas measurement generally, so select the bulb light source can, for avoiding factors such as ambient temperature change to measuring result's influence, general frequency of use is 4Hz, the duty cycle drives infrared light source for 50% signal.

The tungsten filament thermal mass of the bulb light source is large, the heating power and the working current of the tungsten filament are large, and the temperature can rise rapidly after working, so that the utility model needs long heat engine time, and the voltage when the bulb light source is closed is adjusted from 0V to more than 0V, so as to ensure that the device is always in a slight heat engine state, thereby shortening and reducing the heat engine time; and the working current of the infrared light source can be reduced and the heat engine time can be reduced by increasing the series resistance and the current limiting circuit.

The air chamber module 2 comprises an air chamber cover body unit 21 and an air chamber bottom plate unit 22, and the air chamber cover body unit 21 is installed on the air chamber bottom plate unit 22.

In this way, infrared rays pass through the chamber bottom plate unit 22, and are absorbed by the gas to be measured in the chamber lid unit 21.

Air chamber lid unit 21 includes air chamber lid body 211, gas inlet 212, gas outlet and is used for reflecting infrared's reflection subassembly 213, gas inlet 212 is seted up in the top of air chamber lid body 211, gas outlet sets up the one side of keeping away from gas inlet 212 on air chamber lid body 211, all be equipped with waterproof ventilated membrane on gas inlet 212 and the gas outlet, reflection subassembly 213 is installed on air chamber lid body 211 inner chamber top.

Thus, the gas to be measured is filled into the gas chamber cover body 211 through the gas inlet 212, the gas to be measured is discharged through the gas outlet, infrared light is emitted through the light source module 1, and the infrared light is reflected by the reflecting assembly 213 and then is transmitted to the infrared thermopile module 3. In order to avoid the influence of external atmospheric water vapor components entering the air chamber module 2 on measurement, a waterproof and breathable film of polypropylene fabric formed by laminating hot melt adhesive is attached to the surfaces of the gas inlet 212 and the gas outlet, and the gas inlet and the gas outlet cannot be used in a mixed manner in order to ensure the stability of gas measurement. The reflection assembly 213 can reflect the infrared light generated by the infrared light source module 1 to the infrared thermopile module 3 for multiple times, so that the optical path of the infrared light is increased, the gas absorbs the infrared light at the characteristic spectrum more sufficiently, and the signal change of the infrared thermopile module 3 is larger, thereby obtaining better gas concentration resolution.

Another alternative structure of the air chamber module 2 is a linear cavity, infrared light emitted by the infrared light source module 1 passes through the linear cavity and is directly absorbed by the infrared thermopile sensor without being reflected, and compared with a reflection-type cavity, the linear cavity can obtain a better effect, but has a larger volume and is not suitable for application scenes with requirements on the volume.

The reflection assembly 213 includes a first reflection element 2131, a second reflection element 2132 and a third reflection element 2133, wherein the first reflection element 2131, the second reflection element 2132 and the third reflection element 2133 are all installed at the top end of the inner portion of the gas chamber cover body 211 and are arranged in a triangular direction.

In this way, infrared light emitted by the light source module 1 is reflected by the first reflector 2131 to reach the second reflector 2132, reflected by the second reflector 2132 to reach the third reflector 2133, and finally reflected by the third reflector 2133 to reach the infrared thermopile module 3. In order to reflect infrared light onto the infrared thermopile module 3, the first and

second reflectors

2131 and 2132 are each provided with a slope angled at 1 ° and the third reflector 2133 is provided with a slope angled at 45 °.

The gas chamber module 2 is made of ABS material, and the inner cavity is plated with gold or aluminum to obtain good reflectivity so as to reduce loss in the infrared light reflection process.

The air chamber bottom plate unit 22 comprises an air chamber bottom plate body 221, a first placing hole 222 for placing the light source module 1 and a second placing hole 223 for placing the infrared thermopile module 3, wherein the first placing hole 222 and the second placing hole 223 are both installed on the air chamber bottom plate body 221.

In this way, the light source module 1 is placed through the first placing hole 222 so that the infrared light emitted from the infrared light source module 1 is directed to the inside of the cavity of the gas cell module 2, and the infrared thermopile module 3 is placed through the second placing hole 223 so that the intensity of the infrared light is received and measured.

A first infrared thermopile module:

the infrared thermopile module 3 includes a first optical filter 31, a first sensor cap 32, a first infrared thermopile chip 33, a first NTC chip 34 and a first base 35, the first optical filter 31 is installed at a round hole on the upper portion of the first sensor cap 32, the first infrared thermopile chip 33 and the first NTC chip 34 are all installed on a round table on the upper portion of the first base 35, the edge of the first sensor cap 32 is hermetically welded with the edge of the first base 35.

In this way, by installing the first optical filter 31 at the circular hole on the upper portion of the first sensor cap 32, infrared light with a specific wavelength can reach the first infrared thermopile chip 33, the first infrared thermopile chip 33 absorbs radiation energy of the infrared light to generate a weak voltage, so that a light signal is converted into an electrical signal, the voltage signal is output through a pin, the internal temperature of the sensor is detected through the first NTC chip 34, and the first sensor cap 32, the first infrared thermopile chip 33, and the first NTC chip 34 provided with the first optical filter 31 are installed on the first base 35, so as to be cooperatively connected with the signal processing module 4.

The first optical filter 31 is a wavelength range in which an infrared absorption peak of the measured gas is located, for example, an infrared optical filter of 4.26um is used for measuring CO2 gas, so that the influence of the concentration of other components in the atmosphere on the measurement accuracy can be shielded, the atmospheric absorption wavelength band causing interference can be shielded outside the sensor, and the radiation energy received by the thermal first infrared thermopile chip 33 is ensured to be only related to the concentration of the measured gas and not interfered by the concentration of other components in the atmosphere; the first infrared thermopile chip 33 converts the absorbed infrared light into a voltage signal to be output by using the seebeck thermoelectric effect, and the first NTC chip 34 is used for monitoring the ambient temperature of the first infrared thermopile chip 33 to compensate the thermopile sensor output voltage.

The signal processing module 4 comprises an infrared thermopile analog sensor U1, a first operational amplifier U2, a first analog-to-digital converter U3 and a first single chip microcomputer U4, a first pin of the infrared thermopile analog sensor U1 is connected with a second resistor R2 in series and then connected with a third pin of a first operational amplifier U2 and one end of a first capacitor C1 in parallel, a second pin of the infrared thermopile analog sensor U1 is connected with one end of a fourth resistor R4 in parallel and one end of a fifth resistor R5 in parallel, the other end of the fourth resistor R4 is electrically connected with a second pin of the first analog-to-digital converter U3, the other end of the fifth resistor R5 is connected with a power supply VCC, a third pin of the infrared thermopile analog sensor U1 is connected with a reference voltage VREF and a fourth pin of the first analog-to-digital converter U3 in parallel, and a fourth pin of the infrared thermopile analog sensor U1 is grounded;

In this way, the uV level weak voltage Vtp output by the infrared thermopile analog sensor U1 is differentially amplified by using the first operational amplifier U2 with low noise and zero temperature drift, and the amplification factor G is determined by the first resistor R1 and the third resistor R3, that is, the amplification factor G is determined by the first resistor R1 and the third resistor R3

The voltage signal is then amplified to Vout, i.e., V_tp＝(V_out-V_ref)/G；

The NTC chip inside the infrared thermopile sensor is matched with the fifth resistor R5 to perform measurement by adopting a bridge circuit according to the voltage division principle, namely

Will collectThe collected NTC divided voltage is converted into a digital signal through the first analog-to-digital converter U3, and the output voltage of the sensor is compensated. The software algorithm is based on the Bohr-Lambert law, i.e. I₁＝I₀e^-klx；

Wherein, I₁Denotes the density of the target gas, I₀Denotes the density of the zero gas, k denotes the absorption coefficient of the particular gas and filter combination, l denotes the equivalent optical length of the infrared light source and infrared thermopile sensor, and x denotes the gas concentration.

Since the measured gas does not absorb all of the infrared light at the infrared absorption peak, the beer-Lambert law is modified to fit the practical application for measurement, i.e., measurement

Wherein m represents the absorption capacity of the gas to be measured on infrared light emitted by an infrared light source, the value of the absorption capacity is less than 1, n represents a power term which is required to be increased due to the change of the optical path length and the scattering of light, and the equation can be accurately matched with actual absorption data.

A second infrared thermopile module:

the infrared thermopile module 3 includes a second optical filter 311, a third optical filter 312, a second sensor cap 321, a second infrared thermopile chip 331, a third infrared thermopile chip 332, a second NTC chip 341, and a second base 351, where the second optical filter 311 and the third optical filter 312 are respectively installed at an opening of an upper portion of the second sensor cap 321, the second infrared thermopile chip 331, the third infrared thermopile chip 332, and the second NTC chip 341 are all installed on a circular truncated cone of an upper portion of the second base 351, the second infrared thermopile chip 331 and the third infrared thermopile chip 332 respectively correspond to the second optical filter 311 and the third optical filter 312, and an edge of the second sensor cap 321 is hermetically welded to an edge of the second base 351.

Thus, by adopting the dual-channel infrared thermopile sensor, two infrared thermopile chips are matched with two infrared filters with different wave bands, and the infrared filters are divided into a reference channel and a working channel.

Taking the CO2 gas as an example, the dual-channel infrared thermopile sensor structure is shown in fig. 6, and includes two infrared thermopile chips, two infrared filters, and an NTC chip, the second infrared thermopile chip 331 and the third infrared thermopile chip 332 convert the absorbed infrared light into a voltage signal to be output by using the seebeck thermoelectric effect, and the second NTC chip 341 monitors the ambient temperature of the thermopile sensor to compensate the output voltage of the second infrared thermopile chip 331 and the third infrared thermopile chip 332.

The infrared filter comprises two wave bands, namely a 3.95um wave band and a 4.26um wave band, wherein the 4.26um second filter 311 is used as a working channel, and because CO2 gas can absorb infrared light of the 4.26um wave band, the corresponding second infrared thermopile chip 331 is used for detecting voltage change caused by concentration change of CO2 gas; the third filter 312 of 3.95um is used as a reference channel, because CO2 gas is not sensitive to infrared light of 3.95um waveband; the voltage output by the corresponding third infrared thermopile chip 332 is used as a reference, and the measurement error caused by the decreasing of the dust or radiation intensity can be eliminated by matching with the working channel.

The two-channel infrared thermopile sensor absorbs infrared radiation emitted by an infrared light source, after the infrared radiation passes through CO2 gas, the output voltage of an infrared thermopile chip corresponding to a working channel is reduced, the output voltage of an infrared thermopile chip corresponding to a reference channel is not influenced by CO2 gas concentration, measurement errors caused by descending of dust or radiation intensity can be eliminated by mutual matching of the two infrared thermopile chips, after the output voltages of the two channels are recorded, and after algorithm analysis processing, the current CO2 gas concentration can be obtained. The double-channel infrared thermopile sensor has good long-term stability and small influence of environmental temperature on the single-channel infrared thermopile sensor, but has more complex structure and higher price.

The signal processing module 4 comprises a dual-channel infrared thermopile sensor U5, a second operational amplifier U6, a third operational amplifier U7, a second analog-to-digital converter U8 and a second single chip microcomputer U9, a fourth pin of the dual-channel infrared thermopile sensor U5 is grounded, a first pin of the dual-channel infrared thermopile sensor U5 is connected with one end of a seventeenth resistor R17 and a second pin of the second analog-to-digital converter U8 in parallel, the other end of the seventeenth resistor R17 is connected with a power supply VCC, a second pin of the dual-channel infrared thermopile sensor U5 is electrically connected with a third pin of the second operational amplifier U6 after being connected with an eighteenth resistor R18 in series, and a third pin of the dual-channel infrared thermopile sensor U5 is electrically connected with a nineteenth resistor R19 in series and then is electrically connected with a third pin of the third operational amplifier U7;

Therefore, the collected voltage signals output by the dual-channel infrared thermopile sensor U5 are sent to the second single chip microcomputer U9 for signal processing, and the current gas concentration can be obtained after the signals are analyzed, processed and calculated through a gas concentration algorithm.

1) Injecting N2 into the air chamber module 2, waiting for the stability of the air chamber module, and constructing a zero-concentration environment of the gas to be detected;

2) measuring the peak-to-peak value output V1 of the working channel, the peak-to-peak value output V0 of the reference channel and the current ring temperature T0;

3) calculate the sensor zero position Z0 (the ratio of the reference channel to the working channel at zero target gas concentration), i.e.

4) Injecting the measured gas with the concentration of x1 into the gas chamber, measuring the peak-to-peak output V4 of the working channel, the peak-to-peak output V3 of the reference channel and the current ambient temperature T1, and the concentration relations are as follows:

wherein, FA represents the absorbance, namely the absorption capacity of the detected gas to the infrared light at the characteristic absorption peak, m represents the absorption capacity of the detected gas to the infrared light emitted by the infrared light source, k represents the absorption coefficient of the combination of the specific gas and the optical filter, and l represents the equivalent optical length of the infrared light source and the infrared thermopile sensor.

5) Calculating the temperature coefficients of the parameters m and FA, namely:

mT＝m0+i0*(T-T0)

(1-FAT)＝(1-FA)*(1+j*(T-T0))

where mT denotes a value at the time when the ambient temperature is T, m0 denotes a value obtained at the time of calibration, i0 denotes a temperature coefficient of the parameter m, and T0 denotes the ambient temperature at the time of calibration;

FAT indicates a value at which the ring temperature is T, FA is a value obtained by calibration, and j indicates a temperature coefficient of the parameter FA.

From the two parameters temperature coefficient, the temperature compensation of the coefficient m at various concentrations can be calculated, i.e.

mT＝m0+i*(T-T0)

Where i represents the correction coefficients of the parameters m and FA.

6) Calculating the concentration of the gas to be measured, i.e.

For the infrared thermopile sensor with a single channel, because no reference channel exists, the value of the reference channel can be set to 1, and in practical application, the zero self-calibration is carried out through an algorithm. Can be manually and automatically calibrated, and avoid the problem of inaccurate measurement caused by aging of the infrared light source. The measures are as follows: in the use, the utility model discloses can record CO2 concentration minimum in a day, select minimum CO2 concentration value in the record value of 14 consecutive days, think that this CO2 concentration value is the test result of air 400ppm CO2 content in fact, use this as the standard reference value and carry out the automatic calibration of algorithm. The signal processing module 4 is internally integrated with UART, PWM and other communication protocols, can carry out external communication, and meets the requirements of different customers on communication modes. Meanwhile, 4 threaded holes are reserved on the PCB of the signal processing module 4 and used for fixing the PCB and the air chamber module 2; the gap of connection between the PCB of the air chamber module 2 and the PCB of the signal processing module 4 needs to be sealed by glue, so that the influence of atmospheric components on gas concentration measurement is prevented.

The NTC chip temperature calibration algorithm comprises the following steps: obtaining the actual output voltage of the infrared thermopile sensor through at least two temperature calibration points according to the preset environment temperature; and converting the obtained resistance value of the NTC chip into an actual NTC temperature by using an NTC chip resistance value-temperature corresponding relation table, and comparing the actual NTC temperature with a preset environment temperature to obtain an NTC compensation coefficient.

The utility model uses a single-channel infrared thermopile sensor or a double-channel infrared thermopile sensor to detect and absorb infrared light emitted by an infrared light source reflected by the air chamber module 2, and then weak voltage signals are generated; when CO2 gas passes through the gas chamber, the CO2 gas absorbs infrared light of 4.26um wave band emitted by the infrared light source, the infrared signal absorbed by the sensor is attenuated, the output voltage correspondingly changes, and the concentration of the CO2 to be detected is obtained after the voltage is processed, analyzed and calculated by a built-in gas concentration algorithm.

The utility model discloses a gas concentration detection device, produce the infrared light and launch to the air chamber module through the light source module, utilize inside gas to be measured to absorb the infrared light and reflect the infrared light to infrared thermopile module through the air chamber module, can guarantee that the infrared light that infrared light source sent still can be absorbed by infrared thermopile module after the multiple reflection, the user can directly let in CO2 gas, need not to design the air chamber in addition, detect the infrared luminous intensity after being absorbed by the gas to be measured and output corresponding voltage signal to the signal processing module through infrared thermopile module, can be compatible the infrared thermopile sensor of different grade type, be applicable to single channel infrared thermopile sensor and binary channels infrared thermopile sensor, can test CO2, gas such as CH4, calculate the gas concentration to be measured according to voltage signal through the signal processing module, thereby use the user directly to fill the gas to be measured in the air chamber module can measure gas concentration, the concentration measurement requirements of different gases are met, a user does not need to spend a large amount of time to learn the relevant principle, the project development efficiency is improved, and the development time is shortened.

Example 2

As shown in fig. 8, embodiment 2 of the present invention provides a control method using the gas concentration detection apparatus, which specifically includes the following steps:

s1, infrared light is generated through the light source module and is emitted to the air chamber module, and the air chamber module absorbs the infrared light by using the gas to be detected inside and reflects the infrared light to the infrared thermopile module;

and S2, detecting the intensity of the infrared light absorbed by the gas to be detected by the infrared thermopile module and outputting a corresponding voltage signal to the signal processing module, wherein the signal processing module calculates the concentration of the gas to be detected according to the voltage signal.

Thus, the utility model discloses a gas concentration detection device's control method, produce the infrared light and launch to the air chamber module through the light source module, utilize inside gas that awaits measuring to absorb infrared light and reflection infrared light to infrared thermopile module through the air chamber module, detect the infrared light intensity after being awaited measuring gas absorption and output corresponding voltage signal to signal processing module through infrared thermopile module, calculate the gas concentration that awaits measuring through signal processing module according to voltage signal, thereby make the user directly fill the gas that awaits measuring in the air chamber module and can measure gas concentration, satisfy the concentration measurement demand of different gases, it goes to study relevant principle to need not the user to consume the plenty of time again, improve project development efficiency, shorten development time.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention should be covered by the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The utility model provides a gas concentration detection device, its characterized in that, is including light source module (1) that is used for producing the infrared light, be used for utilizing inside gas absorption infrared light that awaits measuring and air chamber module (2) of reflection infrared light, be used for detecting infrared light intensity after being awaited measuring gas absorption and output corresponding voltage signal's infrared thermopile module (3) and be used for calculating signal processing module (4) of the gas concentration that awaits measuring according to voltage signal, light source module (1) and infrared thermopile module (3) are all installed on signal processing module (4), air chamber module (2) are installed in signal processing module (4) top.

2. The gas concentration detection apparatus according to claim 1, wherein the gas chamber module (2) includes a gas chamber cover unit (21) and a gas chamber floor unit (22), the gas chamber cover unit (21) being mounted on the gas chamber floor unit (22).

3. The gas concentration detection apparatus according to claim 2, wherein the gas chamber cover unit (21) includes a gas chamber cover body (211), a gas inlet (212), a gas outlet, and a reflection assembly (213) for reflecting infrared rays, the gas inlet (212) is disposed above the gas chamber cover body (211), the gas outlet is disposed on a side of the gas chamber cover body (211) away from the gas inlet (212), the gas inlet (212) and the gas outlet are both provided with a waterproof and breathable film, and the reflection assembly (213) is mounted on a top end of an inner cavity of the gas chamber cover body (211).

4. The gas concentration detecting apparatus according to claim 3, wherein the reflection assembly (213) includes a first reflection member (2131), a second reflection member (2132), and a third reflection member (2133), and the first reflection member (2131), the second reflection member (2132), and the third reflection member (2133) are installed at an inner top end of the gas chamber cover body (211) and are disposed in a triangular direction.

5. The gas concentration detection apparatus according to any one of claims 2 to 4, wherein the gas cell floor unit (22) includes a gas cell floor body (221), a first placement hole (222) for placing the light source module (1), and a second placement hole (223) for placing the infrared thermopile module (3), the first placement hole (222) and the second placement hole (223) being installed on the gas cell floor body (221).

6. The gas concentration detection apparatus according to claim 5, wherein the infrared thermopile module (3) includes a first filter (31), a first sensor cap (32), a first infrared thermopile chip (33), a first NTC chip (34), and a first base (35), the first filter (31) is mounted at a circular hole at an upper portion of the first sensor cap (32), the first infrared thermopile chip (33) and the first NTC chip (34) are both mounted on a circular table at an upper portion of the first base (35), and an edge of the first sensor cap (32) is hermetically welded to an edge of the first base (35).

7. The gas concentration detection apparatus according to claim 6, wherein the signal processing module (4) comprises an infrared thermopile analog sensor U1, a first operational amplifier U2, a first analog-to-digital converter U3 and a first single chip microcomputer U4, the first pin of the infrared thermopile analog sensor U1 is connected in series with the second resistor R2 and then connected in parallel with the third pin of the first operational amplifier U2 and one end of the first capacitor C1, the second pin of the infrared thermopile analog sensor U1 is connected in parallel with one end of the fourth resistor R4 and one end of the fifth resistor R5, the other end of the fourth resistor R4 is electrically connected to the second pin of the first analog-to-digital converter U3, the other end of the fifth resistor R5 is connected to the power supply VCC, a third pin of the infrared thermopile analog sensor U1 is connected with a reference voltage VREF and a fourth pin of a first analog-to-digital converter U3 in parallel, and the fourth pin of the infrared thermopile analog sensor U1 is grounded;

8. The gas concentration detecting apparatus according to claim 5, wherein the infrared thermopile module (3) includes a second filter (311), a third filter (312), a second sensor cap (321), a second infrared thermopile chip (331), a third infrared thermopile chip (332), a second NTC chip (341), and a second base (351), the second filter (311), the third filter (312) are respectively mounted at an opening at an upper portion of the second sensor cap (321), the second infrared thermopile chip (331), the third infrared thermopile chip (332), and the second NTC chip (341) are respectively mounted on a circular table at an upper portion of the second base (351), and the second infrared thermopile chip (331) and the third infrared thermopile chip (332) correspond to the second filter (311) and the third filter (312), respectively, the edge of the second sensor cap (321) is hermetically welded to the edge of the second base (351).

9. The gas concentration detection apparatus according to claim 8, wherein the signal processing module (4) comprises a dual-channel infrared thermopile sensor U5, a second operational amplifier U6, a third operational amplifier U7, a second analog-to-digital converter U8, and a second singlechip U9, the fourth pin of the dual-channel infrared thermopile sensor U5 is grounded, the first pin of the dual-channel infrared thermopile sensor U5 is connected in parallel with one end of a seventeenth resistor R17 and the second pin of a second analog-to-digital converter U8, the other end of the seventeenth resistor R17 is connected with a power supply VCC, the second pin of the dual-channel infrared thermopile sensor U5 is electrically connected with the third pin of the second operational amplifier U6 after being connected with the eighteenth resistor R18 in series, a third pin of the dual-channel infrared thermopile sensor U5 is electrically connected with a third pin of a third operational amplifier U7 after being connected with a nineteenth resistor R19 in series;