CN110411581A - A multi-channel NDIR gas analysis system based on pyroelectric device - Google Patents

Abstract

A multi-channel NDIR gas analysis system based on pyroelectric devices belongs to the technical field of pyroelectric detectors. The invention comprises a casing, on which a light hole is arranged, a central window is installed on the light hole, and a plurality of detection units and temperature sensors are arranged inside the casing, wherein the detection units are arranged below the center window , and all fall into the projection of the central window on the plane where the detection unit is located; the detection units are stacked and distributed symmetrically about the center of the light hole, and the temperature sensor is set at the position of the symmetrical center of the detection unit. The stacking design adopted by the system enables the system to still have a wide enough field of view when the system performs eight-channel simultaneous detection with a single optical aperture, and realizes the miniaturization of the structure while meeting the requirements of multi-channel detection. In addition, the present invention can also provide temperature compensation data in real time, and the data acquisition accuracy is higher, which is beneficial to improving system stability.

Description

A multi-channel NDIR gas analysis system based on pyroelectric device

technical field

The invention belongs to the technical field of pyroelectric detectors, in particular to a multi-channel NDIR gas analysis system based on pyroelectric devices.

Background technique

As a fast and accurate gas analysis technology, non-dispersive infrared (NDIR) gas analyzer is an optical gas analysis system composed of infrared light source, gas chamber, sensor, circuit and software algorithm, which is very common in practical applications. In the process of analyzing a specific component in a mixed gas, when the infrared light passes through the gas to be measured, the gas to be measured absorbs the infrared light of a specific wavelength, and the absorption relationship obeys the Lambert-Beer absorption law. Each gas has its own characteristic infrared absorption frequency. When the mixed gas is detected, each gas absorbs its corresponding characteristic frequency spectrum. They are independent of each other and do not interfere with each other. This is for measuring a specific gas in the mixed gas The concentration provides the conditions. Compared with the previous electrochemical sensors and thin-film capacitor microphone sensors, advanced pyroelectric devices are used as the core components to realize the advantages of higher measurement accuracy, better stability and longer service life of NDIR technology for measuring gas concentration.

At present, most of the domestically known infrared pyroelectric detectors are single-channel detectors, which cannot meet the simultaneous measurement of multiple analytes, and the accuracy has certain limitations. They are mainly used in the fields of human body and anti-theft. There are few studies on multi-channel detectors, and there are three main categories:

The first is the traditional linear structure, which means that multiple light sources are used to enter several parallel channels for simultaneous gas analysis. This structure has multiple light sources. When in use, the light beam emitted by each light source directly enters the detection channel after being filtered, and reaches the pyroelectric chip after absorption. This structure is relatively simple, but the detection rate is low, the signal is weak, and there are certain limitations in the application field and accuracy.

The second is a spectroscopic detector. This structure refers to the simultaneous analysis of gases based on the light emitted by a light source entering several parallel channels. This structure has only one single light hole, and the micro-reflective surface array is packaged inside as a beam splitter. The beam splitter structure is designed according to the number of channels. For the four-channel detector, it is designed as a four-sided reflective micro-pyramid structure. For the dual-channel detector It is designed as a V-shaped groove structure. When in use, the light emitted by the same light source is reflected by the beam splitter to form two or four beams of light. Each part of the light beam enters the detection channel through the filter, and reaches the pyroelectric chip after absorption. However, this structure is difficult to design a microstructure with more channels, and the design of more channels also requires a larger air chamber, which will significantly increase the size of the sensor module.

The third type is a wheel-type detector. This structure means that the light emitted by a light source enters different channels successively for gas analysis. This structure usually uses a mechanical filter wheel for sequential detection of multiple channels, that is, multiple light holes are designed on the detector housing, and filters of different bands are packaged on the light holes. When used, the same light source emits The light enters the corresponding detection channel according to the selection of the filter, and reaches the pyroelectric chip through absorption. This structure cannot realize multi-channel synchronous detection, and due to the design of multiple light holes on the limited detector shell, the detector has a small viewing angle and cannot obtain more effective radiation, background noise and irrelevant radiation. There are also many signals, and the accuracy of the detector has certain limitations.

In order to overcome the defects of existing multi-channel pyroelectric detectors, it is urgent to develop a miniature high-precision infrared pyroelectric detector with multi-channel synchronous detection capability.

In addition, when the pyroelectric detector detects gas, the signal of the NDIR gas analysis system is affected by many factors due to the change of ambient temperature, including: the spectrum of the light source, the temperature coefficient of the detector, the filter, the temperature coefficient of the operational amplifier, and the resistance And many factors such as capacitance temperature coefficient make the temperature compensation of the non-spectral infrared sensor very complicated. In practice, technicians often only consider the influence of (external) ambient temperature changes, but the center wavelength of the optical filter in a steady state will drift due to internal temperature changes. In general, when the temperature rises, the infrared filter will drift to the long wavelength direction, and the transmittance will decrease. However, the existing designs place the temperature sensor outside the system, which has temperature compensation delay and accuracy. There are limited issues.

Contents of the invention

Aiming at the defects of the prior art, the present invention provides a multi-channel NDIR gas analysis system based on a pyroelectric device. The stacked design adopted by the system enables the system to still have a sufficient width when a single optical hole performs eight-channel synchronous detection. The field of view, while meeting the requirements of multi-channel detection, realizes the miniaturization of the structure. In addition, the present invention can also provide temperature compensation data in real time, and the data acquisition accuracy is higher, which is beneficial to improving system stability.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A multi-channel NDIR gas analysis system based on pyroelectric devices, comprising a housing and several detection units arranged inside the housing, characterized in that a light-through hole is arranged on the housing, and a light-through hole is installed on the light-through hole The central window, the detection unit is arranged below the central window, and all the detection units fall into the projection of the central window on the plane where the detection unit is located; wherein, the detection units are stacked and symmetrical about the center of the light hole distribution; the system further includes a temperature sensor arranged inside the casing, and the temperature sensor is arranged at the position of the symmetrical center of the detection unit.

Further, the number of the detection units is 4-8.

Specifically, the temperature sensor is a resistance temperature detector.

Further, the detection unit includes a pyroelectric crystal plate as a sensitive element and a narrow-band infrared filter arranged on the pyroelectric crystal plate.

Further, the light transmission range of the narrow-band filter is set to be different from each other according to the characteristic absorption bands of different gases to be measured or according to the different characteristic absorption bands of the same gas to be measured.

Further, the detection unit includes a thermal compensation chip as a compensation element, a pyroelectric crystal plate as a sensitive element, and a narrow-band infrared filter arranged on the pyroelectric crystal plate.

Further, an inert gas is filled inside the shell.

Specifically, the surface layer of the pyroelectric crystal sheet has an absorption coating, and the thermal compensation chip is a pyroelectric crystal sheet without an absorption coating on the surface layer.

Specifically, the thermal compensation chip has the same size as the pyroelectric crystal plate, is reversely connected to the pyroelectric chip, and has no response to reflected light.

As an implementation, the number of detection units is 4, and the 4 detection units are arranged in the word "ten" or "mouth", and each end point is set in one group.

As an implementation manner, the number of detection units is 6, and the 6 detection units are arranged in a symmetrical hexagonal star shape, and a group is arranged at each end point.

As an implementation, the number of detection units is 8, and the 8 detection units are arranged in a "mouth" shape on four sides, with 3 groups on each side.

As an implementation manner, the light through hole may be a circular hole, and its diameter is preferably 8.5×8.5mm ² .

As an implementation manner, the material of the central window is preferably a silicon-based material.

As an implementation manner, the central window is installed on the light hole by welding, which can ensure the complete sealing of the detector, provide reliable protection, and prevent the environment, especially moisture, from affecting the system.

The present invention is based on the design of a detection array under a light hole, and adopts a modular stacking design for the middle detection unit in a very limited space, so that the system still has a wide enough field of view when a single light hole is used for multi-channel synchronous detection. The structure miniaturization is realized; the present invention superimposes the sensitive element, the compensation element and the optical filter of the same size, which is different from the existing design where the sensitive element and the compensation element are placed on the same plane, which is further conducive to the miniaturization of the structure, and The detector pins that cannot be used due to the traditional separate installation of compensation elements can be effectively used; at the same time, this stacking design makes all the detection units close to the adjacent detection units inside the detector, ensuring more When the radiant energy is incident on the pyroelectric chip, a higher signal is obtained, and the optical crosstalk between channels can be effectively suppressed. On the other hand, in the present invention, a temperature sensor is integrated inside the casing to generate a temperature signal of the detection unit to indicate the temperature of the detection unit, and to provide temperature compensation data in real time to cope with temperature drift of temperature-sensitive components.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The stacking design adopted by the present invention in a very limited space enables the detector to have a sufficiently wide field of view, realizes the miniaturization design of the structure, and realizes the reception of the radiation energy of the multi-channel detector chip at the same time. Compared with the existing dual-channel and four-channel detectors, it can measure more kinds of gases in the same size.

(2) The present invention can provide temperature compensation data in real time to cope with temperature drift of temperature sensitive components such as optical filters, and the temperature compensation data has high precision and good stability.

(3) The present invention can realize complete sealing and packaging, prevent the influence of the environment on the detector, and avoid the problem that the signal entering the detector is unstable due to aging effects and use stains affecting the optical path.

(4) The present invention can analyze multiple gases synchronously through reasonable structural design, and can also realize more accurate measurement of a single gas by measuring different absorption bands of the same gas.

Description of drawings

Fig. 1 is a schematic top view of an eight-channel pyroelectric infrared detector structure provided by a specific embodiment of the present invention.

Fig. 2 is a schematic cross-sectional structure diagram of an eight-channel pyroelectric infrared detector structure provided by a specific embodiment of the present invention.

In the figure: 1 is a pyroelectric crystal sheet, 2 is a narrow-band infrared filter, 3 is a temperature sensor, 4 is a detector shell, 5 is a light hole, and 6 is a thermal compensation chip.

Detailed ways

In order to make the solutions and principles of the present invention more clear to those skilled in the art, the following describes in detail in conjunction with the drawings and specific embodiments. The content of the present invention is not limited to any specific embodiment, nor does it represent the best embodiment, and general substitutions known to those skilled in the art are also covered within the protection scope of the present invention.

Example:

This embodiment provides an eight-channel pyroelectric infrared detector, the structure of which is shown in Figures 1 and 2, including a detector housing 4, eight detection units disposed in the detector housing 4 capable of receiving light sources, and a temperature sensor 3 A single detection unit includes a piece of pyroelectric crystal sheet 1 and a narrow-band infrared filter 2; wherein a thermal compensation chip 6 is installed under the pyroelectric crystal 1; The center window is welded on the hole 5; the eight detection units are located directly below the light-through hole, arranged in a "mouth" shape, with three groups on each side, and a total of eight channels; wherein, the detection units adopt a stacking design, including stacked The thermal compensation chip 6, the pyroelectric crystal sheet 1 arranged on the thermal compensation chip 6 and the narrow-band infrared filter 2 arranged on the pyroelectric crystal sheet 1, the narrow-band optical filter of eight detection units 2 have different light transmission ranges; the temperature sensor 3 is located in the center of the eight channels.

In this embodiment, the light through hole 5 is a square light through hole of 8.5mm×8.5mm. The central window 5 welded on the light hole is preferably a silicon-based window, which can ensure the complete sealing of the detector.

In this embodiment, the pyroelectric crystal sheet 1 in the pyroelectric infrared detection unit is a lithium tantalate crystal sheet with a size of 1.4 mm × 1.4 mm; the pyroelectric crystal sheet 1 is provided with narrow-band filters for different absorption bands. The optical filter 2 can independently select a suitable optical filter according to the requirements of different optical filter wavelength bands. Preferably, the size of the narrow-band optical filter 2 is 2mm×2mm.

In this embodiment, the thermal compensation chip 6 has the same size as the pyroelectric chip 1 , is reversely connected to the pyroelectric chip 1 , and has no response to reflected light. When the external temperature changes, the two chips will generate charges of equal size and opposite polarity, thus eliminating the bias voltage caused by temperature disturbance.

In this embodiment, the thermal compensation chip 6 in the pyroelectric infrared detection unit is a lithium tantalate crystal chip without a black absorbing coating, and its size is 1.4mm×1.4mm.

In this embodiment, the temperature sensor is a resistance temperature sensor (RTD material is platinum), and the size is 2.2mm×2.2mm.

When the infrared pyroelectric detector is working, the infrared beam enters the detector through the light hole 5 and is refracted by the central window to form a maximum viewing angle of 80°, ensuring that more infrared light is incident on the infrared heat detector. In the discharge detection unit, the infrared light entering the detector is first absorbed by different (with specific waveband) narrow-band filters 2, and then sensed in the pyroelectric crystal sheet 1. The pyroelectric crystal sheet 1 selected in this embodiment The crystal sheet is a lithium tantalate crystal sheet, and other pyroelectric materials can be selected according to specific conditions; the pyroelectric crystal sheet 1 will undergo a pyroelectric effect after being irradiated by infrared light, and reach the infrared light of the pyroelectric crystal sheet 1. The stronger the light, the higher the temperature of the pyroelectric crystal sheet 1, and the more obvious the polarization phenomenon, that is, the more bound charges of different signs gathered at both ends of the pyroelectric crystal sheet 1, and the electrical signal can be drawn out and passed through in a suitable way. The follow-up circuit performs subsequent processing, and finally detects and analyzes to obtain gas information, and then realizes multi-channel infrared detection.

The invention adopts a reasonable design to analyze multiple gases synchronously, and can also measure different absorption bands of the same gas to achieve more accurate measurement of a single gas. It is suitable for detecting mixed gas components, precise measurement of single component gases, etc. In addition, the present invention can also provide temperature compensation data in real time through the temperature sensor 3 placed directly under the light hole to deal with the temperature drift of temperature sensitive components such as optical filters.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention shall still be covered by the claims of the present invention.

Claims (10)

1. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device, including shell, setting are in the interior of shell Several probe units, which is characterized in that a light hole is set on the shell, center window is installed on light hole, The lower section of the centrally disposed window of probe unit, and probe unit entirely falls in center window and puts down where probe unit In the projection in face；Wherein, probe unit is stacked structure and symmetrical two-by-two about light hole center；The system also includes Temperature sensor inside the housing is set, and the temperature sensor is arranged in probe unit symmetrical centre position.

2. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 1, feature exist In the number of the probe unit is 4~8.

3. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 1, feature exist In the detection is pyroelectric electric device.

4. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 3, feature exist In, the probe unit include the pyroelectric crystal piece as sensitive member and be arranged in the pyroelectric crystal on piece narrowband it is red Outer optical filter.

5. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 4, feature exist In the probe unit further includes the thermal compensation chip being arranged in below pyroelectric crystal piece as compensation member.

6. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 5, feature exist In the thermal compensation chip has size identical with pyroelectric crystal piece, and Opposite direction connection is in pyroelectricity chip, and and reflected light Without response.

7. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 1, feature exist In the transparency range of the narrow band filter is according to the characteristic absorption wave band of different under test gas or according to same under test gas Different characteristic absorption bands be set as different from each other.

8. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 1, feature exist In the number of the probe unit is 4, and 4 probe units are in " ten " word or " mouth " word arrangement, each endpoint setting one Group.

9. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 1, feature exist In the number of probe unit is 6, and 6 probe units are in " star " word arrangement, and each endpoint is arranged one group.

10. a kind of multichannel NDIR gas analysis system based on pyroelectric electric device according to claim 1, feature exist In the number of probe unit is 8, and 8 probe units are arranged in four side of " mouth " shape, three groups of every side.