JP3081755B2 - Infrared gas analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an infrared gas analyzer.

[0002]

2. Description of the Related Art Detectors 14 of an infrared gas analyzer (see FIG. 5) include thermal detectors such as a thermopile type and a pyroelectric type, and the like.
A semiconductor detector such as a photoconductive type is used. Since these detectors 14 are easily affected by the ambient temperature, it is necessary to keep the temperature of the sensor block 16 to which the detectors 14 are fixed to improve the measurement accuracy. Measures have been taken such as forming a structure in which the block 16 itself is thermally insulated from the surrounding atmosphere.

[0003]

However, as described above, even when the sensor block 16 is formed in a heat insulating structure, the cell holder adjacent to the sensor block 16 is radiated by the radiant heat from the infrared light source 1. Since the temperature of the light receiving surface 7a of 6 gradually increased, the temperature of the sensor block 16 was also likely to be high.

When the sensor block 16 is formed of a heat insulating structure, it takes a long time from when the infrared light source is turned on until the temperature of the sensor block 16 becomes constant. The time required was relatively long.

On the other hand, in order to improve the measurement accuracy, the optical filters 12 and 13 disposed immediately before the detector 14 are used.
It is necessary to prevent light from entering the optical filter from an oblique direction. Conventionally, a method such as providing light shielding plates 7 and 10 having small light transmitting holes in front of the optical filters 12 and 13 has been adopted. .

However, if the light-shielding plate has a thickness, infrared light is reflected by the wall surface of the light-transmitting hole, for example, as shown by a broken line in FIG. In some cases, the transmission band of the optical filters 12 and 13 may be changed. In FIG.
Denotes an optical window, and 17 denotes a chopper blade.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide an infrared gas analyzer that is hardly affected by ambient temperature and an infrared gas analyzer that prevents light from being obliquely incident on an optical filter in order to improve measurement accuracy.

[0008]

According to the present invention, means for achieving the above-mentioned object are constituted as follows. That is, in the invention according to claim 1, between the detector provided with the optical filter in front straight and optical window that transmits infrared light which has passed through the cell, infrared gas analyzer formed by arranging the light shielding plate
A light- transmitting hole on a light-receiving side surface of the light-shielding plate .
A light reflection layer made of a material that reflects infrared light is formed on the other side.

[0009] In the invention described in claim 2, between the detector provided with the optical filter in front straight and optical window that transmits infrared light which has passed through the cell, the first light blocking at a mutual spacing In the infrared gas analyzer in which a plate and a second light-shielding plate are arranged, the first light-shielding plate and the second light-shielding plate have a knife-edge cross section and a hole diameter increases in the light transmission direction. The first light-transmitting hole and the second light-transmitting hole formed as described above are respectively opened, and the light reflected in the first light-transmitting hole is prevented from being incident on the second light-transmitting hole. Further, an edge angle of the light-transmitting hole and an interval between the two light-shielding plates are set so that light passing through the first light-transmitting hole is not reflected in the second light-transmitting hole. It is characterized in that an air heat insulating layer is formed between the two light shielding plates.

According to a third aspect of the present invention, a light reflecting layer made of a material that reflects infrared light is formed on the light receiving side surface of the first light shielding plate according to the second aspect. .

[0011]

[Action] In the invention according to claim 1, dividing the light-transmitting hole of the light-receiving side surface of the light shielding plate disposed between the optical window and the detector
Since the infrared light is reflected by the light reflection layer formed in the portion , the propagation of radiant heat to the detector behind the light shielding plate is prevented.

According to the second aspect of the present invention, the light reflected in the light transmitting hole of the first light shielding plate does not pass through the light transmitting hole of the second light shielding plate, and the first light shielding plate does not. Since the light passing through the light transmitting hole of the plate is not reflected in the light transmitting hole of the second light shielding plate, the light does not enter the optical filter from an oblique direction. Further, the propagation of radiant heat from the infrared light source to the detector is prevented by the air heat insulating layer formed between the two light shielding plates.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the infrared gas analyzer of the present invention will be described below in detail with reference to the drawings. 2 and 3 are cross-sectional views of the infrared gas analyzer. Reference numeral 1 denotes an infrared light source, 2 denotes a cell for flowing a sample gas, 3 denotes a sample gas inlet, 4 denotes a sample gas outlet, 5 is an optical window made of CaF ₂ or the like, 6 is a cell holder, 7 is a first light shielding plate,
A light reflection film (light reflection layer) on the light receiving side by aluminum evaporation
8 is formed.

Reference numeral 9 denotes a first light-transmitting hole formed in the first light-shielding plate 7, which is formed so that its cross section is formed in a knife-edge shape and its diameter increases in the light transmitting direction. 10
Is a second light-shielding plate provided at a predetermined distance X (see FIG. 1) from the first light-shielding plate 7, and 11 is a second light-transmitting hole.
Similar to the light-transmitting hole 9 of the first light-shielding plate 7, the cross-section is formed in a knife-edge shape so that the hole diameter increases in the light transmitting direction. An air-insulating layer A is formed between the two light-shielding plates 7 and 10.

Reference numerals 12 and 13 denote optical filters for setting an infrared transmission band corresponding to the measurement component, 14 and 14 'denote semiconductor detectors (hereinafter referred to as detectors), and 16 denotes both detectors 14 and 14.
A sensor block 14 'is held, 17 is a chopper blade, and 18 is a motor for driving the chopper blade.

As shown in FIG. 1, the first and second light transmitting holes 9 and 11 first allow the light reflected in the first light transmitting hole 9 to pass through the second light transmitting hole 11. Not to pass, and the first
The edge angles θ ₁ and θ ₂ and the distance X between the light shielding plates 7 and 10 are set so that the light passing through the light transmitting hole 9 is not reflected in the second light transmitting hole 11. ing.

As a result, oblique incidence of light on the optical filters 12, 13 due to reflection of the thick portions of the light shielding plates 7, 10 is prevented, so that the incident light angle on the optical filters 12, 13 becomes constant, and the optical The infrared transmission bands of the filters 12 and 13 do not change, and the calibration curve, the influence of interference gas,
In the C meter, the variation (instrument difference) of the hexane conversion value is reduced, and a highly accurate measurement value can be obtained. Further, the reproducibility of the characteristics is improved even after the optical system is disassembled and reassembled.

On the other hand, the propagation of radiant heat from the infrared light source 1 to the detectors 14 and 14 'is prevented by the light reflecting film 8 and the air insulating layer A formed on the surface of the first light shielding plate 7, and the detection is performed. The temperature rise of the vessels 14, 14 ' is suppressed. The light reflection film 8
May be gold, nickel, chromium, or the like, or a thin plate may be attached instead of vapor deposition.

As described above, the detectors 14 and 14 ' can obtain stable and high measurement accuracy. Detector 1
Since an increase in the temperature of the sensor block 16 supporting the 4, 14 ' is prevented, an expensive heat insulating material does not need to be used for the constituent material, and an inexpensive vinyl chloride material or the like can be used.

Since the temperature rise of the sensor block 16 is suppressed, the time from when the infrared light source 1 is turned on until the temperature of the sensor block 16 becomes constant, that is, the time required for warm-up is short. I'm done.

Further, since the maximum temperature due to the self-heating of the analyzer is suppressed, the high temperature side of the operating temperature range of the analyzer is expanded. That is, since the upper limit of the temperature control can be set low, it is possible to cope with high-temperature environmental conditions.

[0022]

As described above, according to the present invention, Oite to <br/> infrared gas analyzer according to claim 1, the infrared light which has passed through the cell
A light- transmitting hole on a light-receiving side surface of a light-shielding plate disposed between an optical window to be transmitted and a detector having an optical filter immediately before the optical window.
Since a light reflection layer made of a material that reflects infrared light is formed on the part except for, the radiant heat from the infrared light source is prevented from being transmitted to the detector, and highly accurate measurement becomes possible. In addition, the time required for warm-up is reduced. Further, since the upper limit of the temperature control can be kept low, it is possible to cope with high-temperature environmental conditions.

Since the temperature of the sensor block supporting the detector is prevented from rising, a general material can be used for the component parts, and the cost can be reduced.

An infrared gas analyzer according to claim 2
In the optical window that transmits infrared light that has passed through the cell
Each having a between the detector provided with the optical filter just before the first section is formed so as to be formed in the shape knife edge hole diameter is enlarged to the light transmission direction, a second light-transmitting hole The first and second light-shielding plates are provided at an interval from each other, and light reflected in the light-transmitting hole of the first light-shielding plate is prevented from passing through the light-transmitting hole of the second light-shielding plate. since the light passing through the light-transmitting hole of the first light-shielding plate so as not to be reflected in the transmitting hole of the second light shielding plate, the oblique incidence of light is prevented on the optical filter, an infrared optical filter The transmission band does not change, a highly accurate measurement value is obtained, and good reproducibility is also obtained. Further, when a light reflecting layer is formed on the light receiving side surface of the first light shielding plate, a more accurate measurement value can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a configuration of a main part in an embodiment of an infrared gas analyzer of the present invention.

FIG. 2 is a sectional view of a main part of the infrared gas analyzer.

FIG. 3 is a cross-sectional view of the infrared gas analyzer.

FIG. 4 is a schematic diagram showing an example of a configuration of a main part of a conventional infrared gas analyzer.

FIG. 5 is a sectional view of a main part of the infrared gas analyzer.

[Explanation of symbols]

Reference numeral 2 denotes a cell, 5 denotes an optical window, 7 denotes a first light blocking plate, 8 denotes a light reflection layer, 9 denotes a first light transmitting hole, 10 denotes a second light transmitting plate, 11 denotes a second light transmitting hole, and 12 denotes a second light transmitting hole. , 13 ... optical filter, 14,14 '
…Detector.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-215685 (JP, A) JP-A-6-249778 (JP, A) JP-A-4-9642 (JP, A) JP-A-61- 262640 (JP, A) JP-A-5-240774 (JP, A) JP-A-6-30759 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/00-21 / 74 JICST file (JOIS)

Claims (3)

(57) [Claims] Between 1. A detector comprising an optical filter cell infrared before and optical window for transmitting a straight light passing through a barrier
An infrared gas analyzer in which a light plate is disposed, wherein a light reflection layer made of a material that reflects infrared light is formed on a portion of the light shielding plate except a light transmitting hole on a light receiving side surface. An infrared gas analyzer characterized by the above-mentioned. Between 2. A detector provided with the optical filter cell infrared before and optical window for transmitting a straight light passing through the first light-shielding plate at a mutual interval and the second light-shielding plate An infrared gas analyzer comprising: a first light-shielding plate and a second light-shielding plate, wherein the first light-shielding plate and the second light-shielding plate have a knife-edge cross-section and are formed so that a hole diameter increases in a light transmission direction. And a second light-transmitting hole are respectively opened, and light reflected in the first light-transmitting hole is prevented from being incident on the second light-transmitting hole. An edge angle of the light-transmitting hole and an interval between the two light-shielding plates are set so that light passing through the hole is not reflected in the second light-transmitting hole, and air insulation is provided between the two light-shielding plates. An infrared gas analyzer, wherein a layer is formed. 3. The infrared gas analyzer according to claim 2, wherein a light reflecting layer made of a material that reflects infrared light is formed on a light receiving side surface of the first light shielding plate.