JP2001235419A - Infrared gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply perform the correction of the output of an infrared gas analyzer against a temperature change. SOLUTION: Temperature data from rising to stable time at the time of warming operation and the indication data thereof are collected as shown by the dotted line of Fig1 (a). For example, a zero point temperature correction characteristic curve Z2 based on 25 deg.C is operated from these data, and a zero point at an arbitrary temperature is calculated from this correction characteristic curve. In the same way, a temperature correction characteristic curve S2 like Fig1 (b) is calculated, a span at an arbitrary temperature is calculated from this correction characteristic curve, and accurate output indication data at an arbitrary temperature is made possible to operate from two correction characteristic curves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption type infrared gas analyzer for performing a quantitative analysis of a multi-component gas contained in a sample gas.

[0002]

2. Description of the Related Art An absorption type infrared gas analyzer performs qualitative and quantitative analysis of a sample gas based on the amount of infrared absorption by a measurement component gas contained in the sample gas. It is widely used in various fields as a gas analyzer because of its good measurement sensitivity. The configuration of a conventional non-dispersive absorption type infrared gas analyzer and the operation principle thereof will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a measurement cell through which a sample gas flows, reference numeral 2 denotes an infrared light source provided on the incident side of the measurement cell 1, reference numeral 3 denotes a chopper for interrupting an infrared light beam emitted from the infrared light source 2, and reference numeral 4 denotes a chopper 3. Is a detection unit provided on the emission side of the measurement cell 1. The detection unit 5 has a sensor mounting block 6 and a plurality of detection component gas corresponding to various measurement component gases contained in the sample gas (in the figure, $ 1 to $ 3
Of the infrared sensor 7A and the optical bandpass filter 7B. The optical bandpass filter 7B includes a multilayer interference filter in order to make the detection element 7 have wavelength selectivity.
Further, a solid-state sensor such as a pyroelectric sensor or a semiconductor sensor is employed as the infrared sensor 7A.

[0003] In the above configuration, the infrared light emitted from the light source 2 is included in the sample gas in the process of entering the measurement cell 1 as an infrared light beam intermittently intermittently by the chopper 3 and transmitting through the measurement cell. Depending on the various measurement component gases
The specific infrared wavelength is absorbed according to the component concentration. In general, it is well known that a gas of a heteroatomic molecule absorbs infrared light having a specific wavelength according to its molecular structure, and the relationship between the intensity of the infrared absorption and the gas concentration obeys Lambert-Beer's law. ing. I = Io · exp (−kcL) Io: incident light amount of infrared light I: transmitted light amount of infrared light k: extinction coefficient c: concentration of gas component to be measured L: infrared light transmission thickness

That is, in the absorption type infrared gas analyzer of FIG. 2, the wavelength of the specific absorption band of the gas to be measured is selected by the optical band-pass filter 7B, the change in the amount of infrared light is detected by the infrared sensor 7A and converted into an electric signal. The signal is converted to obtain a signal proportional to the density.

[0005]

In the gas analyzer described above, the ambient temperature of the analyzer changes due to the temperature characteristics of a sensor, an optical band-pass filter, a light source, a power supply circuit for driving them, an amplifier, and the like. As a result, an instruction change occurs, so that the temperature characteristic is normally corrected by calculation to obtain a signal that is not affected by the ambient temperature. However, the data for correcting the temperature characteristics is based on the sensor,
The analyzers differ from each other due to variations in optical bandpass filters, etc.In order to obtain accurate correction data, it is necessary to perform a temperature test on each analyzer and obtain temperature correction data. There is a problem that requires. Accordingly, an object of the present invention is to obtain accurate temperature correction data by a simple method and to obtain a highly accurate output.

[0006]

In order to solve such a problem, according to the invention of claim 1, temperature data and an instruction from a start-up time to a stable time in warm-up of an infrared gas analyzer having an arithmetic function are provided. Data is collected, and a zero-point temperature correction characteristic curve and a span temperature correction characteristic curve based on a certain temperature are calculated from these data, and instruction data at an arbitrary temperature can be calculated from the two correction characteristic curves. It is characterized by having done.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram for explaining an embodiment of the present invention. The present invention utilizes the data at the time of warm-up operation of the infrared gas analyzer as shown in FIG. 2, and sets a certain temperature as a reference from the temperature change data from the start-up to the stable time and the instruction data. A zero-point temperature correction characteristic curve and a span temperature correction characteristic curve are calculated.
A zero point and a span at an arbitrary temperature are obtained from the two correction characteristic curves, thereby obtaining correction data at an arbitrary temperature.

Now, it is assumed that the zero point during the warm-up operation of the analyzer changes, for example, as shown by a dotted line Z1 in FIG. Here, if the temperature Ts at the start of warm-up and the indicated value Zs at that time and the temperature Te at the end of warm-up and the indicated value Ze at that time are recorded, zero represented as Q = aT + b (1) is obtained. A point temperature characteristic curve can be obtained.

That is, since Q = Zs when T = Ts and Q = Ze when T = Te, a zero-point temperature characteristic curve is obtained from a = (Zs−Ze) / (Ts−Te) (2) Can be determined.
The intercept is obtained in the same manner, but here, T = 2
This is set to “0” based on the time of 5 ° C. (T25). Thus, b = −aT25 = −T25 (Zs−Ze) / (Ts−Te) (3) In this manner, the zero point temperature correction characteristic curve indicated by the solid line Z2 in FIG. 1A can be obtained.

Similarly, the span temperature correction characteristic curve S2 can be obtained as shown by the solid line in FIG. The span is Ss = Sts−Zs from the indicated value Sts and the zero point indicated value Zs at the start of warming up, and Se = St from the indicated value Ste and the zero point indicated value Ze at the end of warming up.
It is determined as e-Ze. As described above, the zero-point temperature correction characteristic curve Z2 is obtained by converting the actually measured data curve Z1 into T = 2.
Similarly, the span temperature correction characteristic curve S2 is parallelized so that the measured data curve S1 becomes “1” or “100% FS (full scale)” when T = 25 ° C. It can be obtained by moving.

The warm-up start temperature sensor data Ts and the warm-up end temperature sensor data T
e, a warm-up start zero point instruction value Zs, a warm-up end zero point instruction value Ze, a warm-up start span point instruction value Sts,
Table 1 below summarizes the warm-up end span point instruction value Ste, the warm-up start span Ss, the warm-up end span Se, and the like.

[Table 1]

From the above results, the zero point and the span value at an arbitrary temperature can be determined. By comparing these values with the zero point and the span value at T = 25 ° C. (calculating the ratio between the two). , An indicated value at an arbitrary temperature can be obtained.

[0013]

According to the present invention, the change in temperature of the sensor unit and the change in instruction of the analyzer when the analyzer is warmed up are recorded,
Since the amount of change (ratio) of the instruction of the analyzer with respect to the temperature is obtained by the calculation, it is possible to easily obtain temperature correction data that is very close to the temperature characteristic of each analyzer, and to measure the temperature characteristic for each analyzer. The advantage that labor can be saved can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for describing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a general configuration of an infrared gas analyzer.

[Explanation of symbols]

1. Measurement cell, 2. Infrared light source, 3. Rotary chopper,
4 ... motor, 5 ... detector, 6 ... sensor mounting block, 7
A: infrared sensor, 7B: multilayer interference filter, 8: infrared light flux.

Claims (1)

[Claims] 1. An infrared gas analyzer having an arithmetic function collects temperature data and instruction data from a start-up time to a stable time when the infrared gas analyzer is warmed up, and corrects a zero point temperature based on these data based on a certain temperature. An infrared gas analyzer wherein a characteristic curve and a span temperature correction characteristic curve are calculated, and instruction data at an arbitrary temperature can be calculated from the two correction characteristic curves.