JPH04301736A - Moisture measuring system - Google Patents

Abstract

PURPOSE:To perform reliable calibration in a low concentration area in a simple manner by performing calibration in sensitivity with one error of a measuring cell operated based on relation between each of plural different actually measured values obtained from a sensor section and each corresponding theoretical value. CONSTITUTION:Highly pure air from which moisture is removed with hydrogen carbon and the like burned, is mixed with standard gas which contains constant hydrogen in a specified ratio, by a divider 6 so as to be supplied to a hydrogen and oxygen combustion type moisture generator 2, the mixture is then burned within a reaction pipe 21 by means of an electric furnace 22 while moisture standard gas is being generated, so that moisture concentration is detected by the sensor section of a measuring cell 3. Thus, a few moisture concentration is measured by the divider 6 with a mixing ratio changed, after measured values have been stored in the memory section of a calibration means 13, each theoretical value of moisture which is obtained by the method of least squares and the like based on the mixing ratio with the quantity of hydrogen in hydrogen standard gas, is compared with each measured value while the constant error in moisture of the cell 3 is obtained, so that moisture concentration can thereby be detected with high accuracy with calibration performed in sensitivity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture measuring system, and more particularly to a moisture measuring system capable of calibrating the sensitivity of a sensor section for detecting the concentration of moisture in gas.

0002

BACKGROUND OF THE INVENTION Generating a moisture standard gas has generally been a difficult and time-consuming process. Among them, hydrogen and
There is an oxygen combustion method. This is a method in which hydrogen and excess oxygen are burned at high temperatures in the presence of a noble metal catalyst to generate the same mole of water as hydrogen. For example, a hydrogen standard gas of known concentration is introduced through the gas inlet of the moisture generator. After adjusting the flow rate to a constant level using a flow rate control valve, moisture etc. are removed using a dehumidifier (for example, molecular sieves). After that, hydrogen and oxygen react in a reaction tube containing a precious metal catalyst,
Moisture is produced. A standard gas containing a known concentration of water is thus obtained.

0003

[Problem to be Solved by the Invention] However, in this hydrogen/oxygen combustion method, a small amount of moisture that is usually adsorbed inside the reaction tube or on the catalyst is released little by little, so the released moisture is added to the generated moisture. This will result in an error. This is especially a problem when producing a moisture standard gas at a low concentration, so it has been necessary to purge it with dry gas for a long time to stabilize it.

[0004] Thus, the main object of the present invention is to provide a moisture measuring system that can easily perform reliable calibration in a low concentration region even with such a moisture generator.

[0005]

[Means and effects for solving the problems] The present invention provides a measurement cell, a measurement gas supply means for supplying a measurement gas to the measurement cell, a calibration gas supply means for supplying a calibration gas to the measurement cell, and a measurement cell. It is built in and consists of a sensor section for detecting the moisture concentration in the measurement gas and the calibration gas, and a calibration means for calibrating the sensitivity of the sensor section based on the moisture concentration signal in the calibration gas from this sensor section, The calibration gas supply means includes a combustion type moisture generator, a hydrogen standard gas supply unit that supplies hydrogen standard gas containing a known amount of hydrogen to the generator, and supplies the calibration gas obtained by the generator to the measurement cell. The calibration means includes a storage section that stores a moisture concentration value in the calibration gas obtained from the sensor section;
This moisture measurement system includes a calculation section that calculates a certain error from a plurality of different moisture concentration values stored in the storage section and calibrates the sensitivity of the sensor section.

In other words, the present invention allows sensitivity calibration to be performed by calculating a certain error of the measurement cell from the relationship between a plurality of different measured water concentration values stored in the storage unit and the theoretical value using the calculation unit. Accurate moisture concentration measurement becomes possible.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on embodiments shown in the drawings. Note that this invention is not limited to this.

First, in FIG. 1, a moisture measurement system (
H) consists of a measurement cell (moisture meter) (3), a measurement gas supply means (7) for supplying a measurement gas to this measurement cell, and a calibration gas supply means (11) for supplying a calibration gas to the measurement cell (3).
), a sensor section (12) built into the measurement cell (3) for detecting the moisture concentration in the measurement/calibration gas, and a sensitivity calibration of the sensor section (12) based on the detection signal from this sensor section. It mainly consists of a calibration means (13) for performing the following.

The calibration gas supply means (11) includes a divider (6
), and a hydrogen standard gas supply line (
10), a dry standard gas supply line (8) that leads the standard gas (air) to the splitter (6) via the electric furnace (4) and the dehumidifier (5), and a hydrogen standard gas supply line from the splitter (6). and a moisture generator (2) which is supplied by mixing and dry standard gas at a specific division ratio and generates moisture by a hydrogen-oxygen combustion type.

In particular, in FIG. 2, the calibration means (13) includes a storage section (15) for storing the moisture concentration value in the calibration gas obtained from the sensor section (12), and a plurality of different moisture concentration values stored in this storage section. A calculation unit (CPU) (14) calculates a certain error from the concentration value and calibrates the sensitivity of the sensor unit (12).
) and becomes the main character. Note that (16) is a digital display section, and (17) is an operation section.

Next, the moisture generator (2), especially in FIG. It mainly consists of a reaction tube (21) which is received through the reactor tube (21). Note that (22) is an electric furnace.

Next, the operation of the moisture measuring system (H) having the above configuration will be explained by adding FIGS. 4 and 5 to FIGS. 1 to 3.

[0013] A standard gas (balance gas: air) containing a certain amount of hydrogen (20 ppm) and high-purity air (air) from which hydrocarbons, etc. are completely combusted and moisture removed are separated by a splitter (6). They are mixed at a specific ratio (for example, 2:5) and supplied to the hydrogen-oxygen combustion type moisture generator (2). In this moisture generator, a mixed gas is combusted in a reaction tube (21) by an electric furnace (22) to generate a moisture standard gas. Next, the moisture concentration of the generated moisture standard gas is detected by the sensor section (12) of the measurement cell (3).

[0014] Subsequently, the mixing ratio of hydrogen standard gas and high-purity air is changed using the divider (6) (for example, 3:5), and the water concentration is measured using the measuring cell (3) in the same manner as above. The measurement data is stored in the storage section (15). In this way, several water concentrations were measured by changing the mixing ratio, and the storage section (1
5), the calculation unit (14) checks that the data is complete, and then calculates the theoretical value obtained from the hydrogen amount and mixing ratio in the hydrogen standard gas and the measurement cell ( 3) is calculated as shown in FIG. 4. As a result, the cutting edge of the Y-axis in Fig. 4 is the error moisture content (for example, 0
．． 3 ppm), and span calibration can be performed using the slope of the straight line found in FIG.

[0015]

[Effects of the Invention] According to the present invention, the arithmetic unit calculates a certain error of the measurement cell from the relationship between the theoretical value and a plurality of different actually measured water concentration values stored in the storage unit, and calibrates the sensitivity. , it becomes possible to measure moisture concentration with high precision.

[Brief explanation of drawings]

FIG. 1 is a functional explanatory diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the measurement cell and calibration means.

FIG. 3 is an explanatory diagram showing the internal structure of a hydrogen-oxygen combustion moisture generator.

FIG. 4 is a graph showing the relationship between actually measured values of moisture concentration when the division ratio between hydrogen standard gas and dry standard gas is changed.

FIG. 5 is a flowchart showing the operation of the moisture measurement system.

FIG. 6 is a diagram corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

2　　　Hydrogen-oxygen combustion type moisture generator 3 Measurement cell 6 Divider 7 Measurement gas supply means 8 Dry standard gas supply line 10 Hydrogen standard gas supply line 11 Calibration gas supply means 12 Sensor part 13 Calibration means 14 Arithmetic unit 15 Memory section H Moisture measurement system

Claims (1)

[Claims] Claims: 1. A measurement cell, a measurement gas supply means for supplying a measurement gas to the measurement cell, a calibration gas supply means for supplying a calibration gas to the measurement cell; The calibration gas supply means consists of a sensor section for detecting the moisture concentration in the calibration gas, and a calibration means for calibrating the sensitivity of the sensor section based on the moisture concentration signal in the calibration gas from the sensor section. a hydrogen standard gas supply section that supplies hydrogen standard gas containing a known amount of hydrogen to the generator, and a calibration gas supply path that supplies the calibration gas obtained from the generator to the measurement cell. The means includes a storage section that stores the moisture concentration value in the calibration gas obtained from the sensor section, and a certain error calculated from a plurality of different moisture concentration values stored in this storage section to calibrate the sensitivity of the sensor section. A moisture measurement system consisting of a calculation section.