JP2002357548A - Non-dispersive infrared absorption detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-dispersive infrared absorption detecting device capable of substantially heightening the effects of removing noise components of a conventional infrared absorption detecting device, shortening warm-up time, and improving detection sensitivity. SOLUTION: The non-dispersive infrared absorption detecting device with two cells, a sample cell 3 and a reference cell 4, is provided with a gas channel interchanger 1 for simultaneously interchanging a sample gas and a zero gas at every predetermined times and supplying them for the sample cell 3 and the reference cell 4. Therefor with differences in structure, size, fixing and wiring methods, and temperature between the sample cell and the reference cell, it is possible to substantially heighten the effects of removing the noise components of the conventional absorption detecting device and improve detection sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-dispersive infrared absorption detector used for quantitative measurement of gas components such as in atmospheric gas component analysis.

[0002]

2. Description of the Related Art Conventionally, a non-dispersive infrared absorption detecting apparatus has two cells, a comparison cell and a sample cell. The comparison cell contains only zero gas (a gas that does not absorb infrared light) and the sample cell contains a sample. 2. Description of the Related Art A two-beam non-dispersive infrared absorption detector that supplies a gas and detects unnecessary signals other than a sample by detecting a difference between outputs from two cells is used. The sample cell and comparison cell are manufactured and controlled so that their structure and dimensions and the cell surrounding environment such as cell temperature are the same. When an environment difference occurs, a noise component is mixed in the output, the output becomes unstable, and the sensitivity of the detector is reduced. A non-dispersive infrared absorption detector is a one-beam type device that supplies a sample gas and a zero gas alternately to one cell in time, separates and detects signals in each period, and detects a difference between them as a sample output. However, in the one-beam type apparatus, the signals of the sample gas and the comparison gas are signals at different times, and are affected by temporal fluctuations in the surrounding environment and fluctuations in the characteristics of the electronic circuit. The sensitivity is lower than that of the detection device.

The structure of a conventional two-beam non-dispersion type infrared absorption detector which has been widely used will be described below with reference to FIG. The incident light L passes through the sample cell 3 or the comparison cell 4 alternately with time by the rotation of the optical chopper 2 at, for example, about 10 Hz. Sample gas SG and zero gas RG
Are guided from the gas inlet 3C and the gas inlet 4C to the sample cell 3 and the comparison cell 4, respectively, pass through the sample cell 3 and the comparison cell 4, respectively, and are passed through the gas outlet 3D of the sample cell 3 and the gas outlet 4D of the comparison cell 4 respectively. It is discharged outside. Light transmitted through the sample cell 3 and the comparison cell 4 is detected by the detector 5. Since the signals of the sample cell 3 and the comparison cell 4 are repeatedly obtained sequentially for each rotation of the optical chopper 2, these signals are separated by the electronic circuit of the signal processing circuit 6, and the signal output of only the sample cell 3 and the comparison cell Only four signal outputs are accumulated for a period necessary for subsequent signal processing.

Since the signal output of only the sample cell 3 contains noise components due to, for example, power supply voltage, ambient temperature, and temporal variations in the characteristics of the detector 5, the signal output from the signal processing circuit 6 is further increased. By calculating the difference between the signal output of the sample cell 3 only and the signal output of the comparison cell 4 only, and using this as a true sample output, the influence of the noise component is reduced.

[0005]

The structure of the conventional non-dispersion type infrared absorption detector is as described above. However, in the prior art, the difference in structure and dimensions between the sample cell 3 and the comparison cell 4 and the sample cell If there is a temperature difference between the reference cell 3 and the comparison cell 4, the effect of removing the noise component is impaired. Therefore, it is necessary to improve the manufacturing accuracy and use a high-stability thermostat, and increase the weight and size of the apparatus. , Leading to an increase in manufacturing costs. Even if the production accuracy is improved or a thermostatic chamber is used, the sample cell 3 and the comparison cell 4 are essentially manufactured separately, placed at different positions, and fixed and wired separately. However, there was a limit in securing the same characteristics.

An object of the present invention is to provide a non-dispersive infrared absorption detecting device which solves such a problem.

[0007]

The non-dispersive infrared absorption detecting device provided by the present invention is intended to solve the above-mentioned problems.
A gas flow exchanger is provided in front of the gas inlets of the sample cell and the comparison cell for alternately and simultaneously exchanging the sample gas and the zero gas at predetermined time intervals and supplying the gas to the sample cell and the comparison cell. The road is changed repeatedly. According to the present invention, the sample cell is also used as a comparison cell for a certain period, and the comparison cell is also used as a sample cell for a certain period.

[0008]

FIG. 1 is a diagram showing a configuration of a non-dispersion type infrared absorption detector provided by the present invention, and FIG. 2 is a diagram showing an embodiment of a specific structure of a gas flow exchanger 1. It is. In addition,
1 and 2, components denoted by the same reference numerals as those shown in FIG. 3 are the same as the components shown in FIG. 3, and a detailed description of these functions will be omitted.

First, the configuration of the gas flow exchanger 1 will be described with reference to FIG. The gas flow exchanger 1 has a sample gas inlet 11.
And a zero gas inlet 15, each of which has a sample gas SG
And the zero gas RG are supplied. Further, the gas channel exchanger 1 is provided with a sample cell connection port 12 and a comparison cell connection port 16, and as shown in FIG. 1A, the gas inlet 3A of the sample cell 3 and the gas It is connected to the inlet 4A. In FIG. 2, a rotary valve 14 having two gas passages is attached to the exchanger body 13 so as to be rotatable by sliding. The open ends of the two passages are provided at equal intervals on the outer periphery of the rotary valve 14. Therefore, FIG. 2 shows a state in which the sample gas SG is connected to the sample cell connection port 12 and the zero gas RG is connected to the comparison cell connection port 16. However, when the rotary valve 14 is rotated by 90 degrees, the sample gas SG is turned off. Is the comparison cell connection port 16
Next, the zero gas RG is connected to the sample cell connection port 12.

By rotating the rotary valve 14 by 90 degrees at predetermined intervals and stopping again for the predetermined interval, the sample gas SG is sequentially supplied to the sample cell connection port 12 and the comparison cell connection port 16. Supplied to Further, the zero gas RG is sequentially supplied to the connection port opposite to the sample gas SG, that is, the comparison cell connection port 16 and the sample cell connection port 12. With this configuration, the gas inlet 3A and the gas inlet 4A
As shown in FIG. 1 (b), the supply gas to is supplied after being exchanged every predetermined time. The gas that has passed through the sample cell 3 and the comparison cell 4 is discharged from the gas outlet 3B and the gas outlet 4B of FIG.

The signals from the sample cell 3 and the comparison cell 4 are separated by the electronic circuit of the signal processing circuit 6N and stored for a period required for the subsequent signal processing. The signal processing circuit 6N accumulates the signal of the sample cell 3 as a signal output of the sample gas SG during a period when the sample gas SG passes through the sample cell 3, and compares the signal during a period when the sample gas SG passes through the comparison cell 4. The signal of the cell 4 is stored as a signal output of the sample gas SG. During the period when the zero gas RG passes through the sample cell 3, the signal of the sample cell 3 is accumulated as the signal output of the zero gas RG, and during the period when the zero gas RG passes through the comparison cell 4, the signal of the comparison cell 4 is stored as the zero gas RG. And accumulate it as a signal output. The difference between the signal output of the sample gas SG and the signal output of the zero gas RG is calculated to obtain a true sample output.

The predetermined time may be set to a time much longer than the rotation cycle of the optical chopper 2, for example, several seconds or more. Therefore, no special high-speed operation technology is required for the design and manufacture of the drive circuit of the rotary valve 14 and the design and manufacture of the synchronous operation circuit with the rotary valve 14 of the signal processing circuit 6N.

FIG. 2 shows an example of a specific structure of the gas flow path exchanger 1. The structure of the gas flow path exchanger 1 is as follows.
The structure is not limited to the structure shown in FIG. 2 as long as it meets the purpose of simultaneously exchanging the sample gas and the zero gas every predetermined time and supplying them to the sample cell 3 and the comparison cell 4. Also, an example of a specific rotation cycle of the optical chopper 2 and the rotary valve 14 has been described, but the present invention is not limited to this value.

[0014]

The present invention has been described in detail above. Therefore, even if there is a difference in the structure and dimensions of the sample cell and the comparison cell, a difference in the fixing / wiring method, a temperature difference, etc., the conventional infrared absorption detection is performed. Since the effect of removing the noise component of the apparatus can be further enhanced and the detection sensitivity can be improved, the design of the cell, the constant temperature bath and the like can be simplified, and the warm-up time can be shortened.

[Brief description of the drawings]

FIG. 1 is a diagram showing a non-dispersion type infrared absorption detection device according to the present invention. (A) is a perspective view showing the structure of the device, (b)
FIG. 4 is a diagram showing a state of temporal replacement of supply gas.

FIG. 2 is a cross-sectional view showing an example of a gas flow exchanger of the non-dispersive infrared absorption detection device according to the present invention.

FIG. 3 is a perspective view showing the structure of a non-dispersive infrared absorption detection device according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gas flow exchanger 2 ... Optical chopper 3 ... Sample cell 4 ... Comparison cell 13 ... Exchanger body 14 ... Rotary valve SG ... Sample gas RG ... Zero gas

Continued on the front page F-term (reference) 2G052 AA01 AD42 CA04 CA35 GA12 HC10 2G059 AA01 BB02 EE01 FF08 HH01 JJ24

Claims (1)

[Claims] 1. A cell having two cells, a sample cell and a comparison cell,
In a non-dispersive infrared absorption detector that detects and supplies a sample gas to a sample cell, it is necessary to simultaneously exchange the sample gas and zero gas at predetermined time intervals and repeatedly supply the sample cell and the comparison cell. Characteristic non-dispersive infrared absorption detector.