JPH0816659B2 - Calibration method of gas concentration measuring instrument and apparatus used for the implementation - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a calibration method for a gas concentration measuring instrument and a calibration device used for the implementation.

2. Description of the Related Art Conventionally, many measuring machines for measuring the concentration of a specific gas have been provided, but it is necessary to calibrate all of the specific gas by the manufacturer, and one measuring machine can measure a plurality of unspecified types. It cannot measure gas, cannot record data, and cannot be used for personal exposure measurements. Further, in gas measurement, it is important to know the relationship between the indicated value of the measuring instrument and the amount of the target gas component correctly, and therefore the standard gas is adjusted. Conventionally, as a method therefor, a method using a diffusion cell and a method of vaporizing a certain amount of liquid in a container having a constant volume are known as typical methods.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the former of the conventional adjustment methods, there is a problem that not only a large amount of clean air is required, but also a long time is required until the concentration becomes stable. Yes,
Further, in the latter case, there is a problem that even if an attempt is made to use it to calibrate the gas sensor, it is difficult to install the sensor in the container and it cannot be used. Further, both of them are configured to be used in a laboratory, which is difficult to use at a measurement site, and it takes time to clean the container.

Therefore, an object of the present invention is to solve the problems of the conventional method of calibrating a measuring instrument and its calibrating device, so that the user can easily adjust the standard gas and calibrate the measuring instrument based on the standard gas at the measurement site. It is an object of the present invention to provide a calibration method which can be performed in a relatively short time and enables one measuring instrument to measure a plurality of kinds of gas concentrations, and an apparatus used for carrying out the calibration method.

Means for Solving the Problems In order to achieve the above object, the present invention according to claim 1 provides a gas circulation system in which the semiconductor sensor of a gas concentration measuring instrument having a semiconductor sensor is used. Installed in a test tank installed in the passage, the inside of the gas circulation system passage is cleaned with a clean gas, the inside of the gas circulation passage is filled with a clean gas, and then the inside of the gas circulation passage is filled with a standard gas. The gas concentration measuring device is circulated, and the gas concentration measuring device is adjusted so that the output value of the semiconductor sensor corresponds to the gas concentration. The invention according to claim 2 is the gas circulation system. Path, a gas supply port and a discharge port provided in the gas circulation system path for supplying and discharging a clean gas to the gas circulation system path, and a test tank and a gas-liquid injection port provided in the gas circulation system path And provided in the gas circulation system And a pump for circulating a gas in the gas circulation system.

Operation In the above method, the clean gas is circulated and filled in the circulation system by the pump, the sensor output at that time is adjusted to 0, and the standard gas or the standard solution is introduced into the circulation system. Introduced, when they are diluted in the circulation path and their gas concentration reaches a predetermined value after a certain time, if the output value of the sensor differs from that value, they will be matched by span adjustment. .

Practical Example FIGS. 1 to 3 show a gas concentration measuring instrument 1 calibrated by the method of the present invention.

The measuring machine 1 shown in FIG. 1 comprises a semiconductor sensor 3, an amplifier 4, a clock 5, a key switch 6, an A / D converter 7, an arithmetic processing unit 8, a ROM 9, a RAM 10 and the like, and a liquid crystal display unit 1.
1, a memory card 12 and a power supply circuit 13.
The measuring device 1 may be portable or stationary,
In the case of a portable type, the power supply circuit 13 is a battery built-in type.

In the above, various types of semiconductor sensors may be used, and the most suitable one is disclosed in Japanese Patent Laid-Open No. 143946/1984. A brief description will be given with reference to FIG. For details, refer to the description in the publication.

The semiconductor sensor in this embodiment is shown by 15 in FIG. 2, 16 is a substrate, 17 is an insulating layer, and 18 is a metal layer. Metal layer
18 has 3 each having two electrode parts and one thin wire part 3
It is formed on the pattern of the book, 22 and 24 are heaters, 22
Reference numerals a, 22d, 24c, and 24f are heater electrodes, 23 is a gas detection lead, and 23b and 23e are detection electrodes. 21 is a semiconductor layer for gas detection. Reference numeral 19 is an insulating layer, and each electrode portion (22a, 23b,
24c, 24d, 23e, 24f), after opening the window of insulating layer 19
20 are formed. The gas detector 15 is a film
26 Lead foils 31 (6 pieces) mounted on each electrode part (22
a, 23b, 24c, 22d, 23e, 24f) is mounted on the film 26 by heating and bonding to the bump 20.
The lower part is covered with a lower cover 27, and the upper part is covered with an explosion-proof net 29 and a dust-proof filter 30. The explosion-proof net 29 and the dust-proof filter 30 are attached and fixed to the upper cover frame 28 provided on the film 26. The explosion-proof net 29 is for preventing ignition. The dust-proof filter 30 has a fine structure of the gas detection device 15, and is for preventing the influence of dust attached to the surface such as reduction of life and unstable operation,
When the gas detection device 15 of this embodiment is attached to the film 26, glass wool is used, which does not allow dust of 0.1 μm or more to pass through and does not hinder the inflow and outflow of gas. The gas is adsorbed on the gas detecting semiconductor 21 through the explosion-proof net 29 and the dust-proof filter 30.

4 to 6 show details of the calibration device 2 used in the method of the invention.

In the calibration device 2, one end of a connecting pipe 40 is connected via a three-way cock 39 to an intake pipe 38 provided with a gas inlet 36 on one side and an air inlet 37 with an activated carbon filter on the other side. At the other end of this connecting pipe 40, a four-way cock 41
The closed pipe line 42 is connected to the two sides of the exhaust pipe 44, and the exhaust pipe 44 is connected to the other side thereof.

A buffer tank 45, a test tank 46, a sampling port 47, a gas-liquid injection port 48, and a pump 49 are sequentially arranged in the closed pipe line 42 in a direction away from the cock 41. This pump 49
Is composed of a diaphragm pump or a bellows pump, and the gas contact portion is formed by a material such as Teflon, glass, or stainless steel, which is less corroded or adsorbed.

FIG. 5 shows the sampling port 47 and the gas-liquid injection port 48, and FIG. 6 shows the ports of the test tank 46. These ports are provided with Teflon-clad silicone stoppers 50 and 51, respectively. Then, the silicone stopper 50 can be inserted with a silidine needle (not shown) through the packing.

FIG. 7 shows a state in which the sensor 3 is mounted on the test layer 46, and the stopper 50 'at this time has a hole 53 for mounting the sensor stopper 51 and the cord 52.

Each member of the calibration device 2 is separably connected by a joint (not shown), so that part of the conversion and cleaning of each part can be performed separately. Further, a heater may be attached to the buffer tank 45, the test tank 46 and the like to keep the temperature constant, and after they are assembled, they are integrally formed so that they can be stored and transported easily.

FIG. 8 is a flow chart of the operation of the measuring instrument 1 during calibration, and the calibration work will be described with reference to this.

The sensor 3 is attached to the test tank 46 as shown in FIG. 7, and the three-way cock 39 is set to the position shown in FIG.
Is the position shown in FIG. 10 (a), the suction port of the intake pipe 38
Clean air is introduced into the closed pipe line 42 through the connecting pipe 40 through the activated carbon filter 37 and is discharged from the exhaust pipe 44. Therefore, the four-way cock 41 is switched to the position shown in FIG. The tube 44 is closed, whereby the system of the calibration device 2 is filled with clean air. Therefore, at this time, the display unit 11
The zero value is automatically adjusted by the operation of the control means so that the output value of the sensor 3 displayed at 0 becomes zero.

When a standard solution or standard gas is injected from the gas-liquid injection port 48 using a syridine or the like, the standard solution is vaporized and diluted to become a gas, and the standard gas is diluted, and the diluted gas enters the system. After a certain period of time, the concentration C is calculated by the following equation.

(1) In case of standard solution injection M: Molecular weight ρ: Density (g / ml) V: Standard solution injection amount (μ) A: System volume () T: Freezing point temperature 273.15 (° K) t: Temperature (° C) (2) For standard gas injection If c: Standard gas concentration (ppm) v: Standard gas amount (ml) In this case, the gas concentration C in the system can be increased stepwise by successively injecting the standard liquid or standard gas.

Here, as an example, a system having a capacity of 5 is used,
The relationship between the injection amount μ of acetone at 25 ° C and the concentration ppm of acetone in the system is shown in the graph of FIG.

Next, as another example, the case of using toluene as a standard solution will be described. After adjusting the output of the gas sensor 3 to 0, 1 μl of toluene was injected in place of acetone, and the toluene concentration was adjusted to 46 ppm by the above, If the output value of the sensor 3 is read and it is displayed that the value is other than 46 ppm, the span is adjusted by the operation of the control means to adjust the displayed value to 46 ppm, thereby the output of the gas sensor 3 The value will show the correct value.

In this case, since the relationship between the output voltage of the sensor 3 and the gas concentration is not a linear relationship, it is linearized in the arithmetic processing unit 8 and is displayed on the liquid crystal display unit 11, whereby the measuring device 1 The calibration work is completed.

After the calibration is completed in this way, the measuring instrument 1 measures the test gas in the environment of the measurement site, and the measured gas is displayed on the display unit.
When the writing start signal is sent by the key switch 6 at that time, the concentration of the test gas can be accumulated in the memory card 12. Then, this memory card can be read out by a personal computer or the like, and the change with time of the airborne concentration can be graphed as shown in FIG.

During the calibration operation, the sampling port 47 is used, and the gas in the system is sampled from this by a gas tight syringe or the like, and this can be used as a standard gas for gas chromatographic analysis and the like.

When the calibration work is completed as described above, the calibration device 2
The inside of the system is to be cleaned, but it is a 3-way trick 39
Is set to the position shown in FIG. 9 (c) or (d), the four-way cock 41 is set to the position shown in FIG. 10 (a), and the pump 49 is operated. By the operation of this pump 49, the inside of the system is brought into a depressurized state, and the substance adsorbed on the inner wall of each member is discharged.

After that, if the three-way cock 39 is set to the position shown in FIG. 9A or 9B, the inside of the system will be replaced with clean air from the suction port 37, nitrogen gas from the suction port 36, or the like.

By repeating the above-mentioned cleaning operation, the inside of the system will be cleaned. At that time, if the apparatus is heated by a heater or the like, the cleaning will be more effective.

In the calibration device as described above, it is preferable to use Teflon, glass, stainless steel, or the like, which is less adsorbed and decomposed, in the gas contact part so as to reduce the change in concentration over time. Further, it is possible to put a member in the test tank 46 and perform a deterioration test with different gases.

EFFECTS OF THE INVENTION The present invention is as described above, in which a semiconductor sensor of a gas concentration measuring instrument is installed in a test tank, the test tank is installed in a standard gas circulation system path, and the circulation system path is cleaned with a clean gas. After this, the standard gas was circulated in the system and the output of the sensor was adjusted to correspond to this gas concentration, so the user could adjust the standard gas and calibrate the measuring machine at the measurement site. In this way, it is possible to measure different gases with one measuring instrument, and a small amount of clean gas, standard solution or standard gas can be used, and calibration work is quick. There is an effect that is done in. Therefore, it is possible to measure the change with time of the individual exposure concentration of the worker such as the organic solvent.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of an embodiment of a measuring machine of the present invention, FIG. 2 is a schematic diagram of a semiconductor sensor most suitable for the same as above, and FIG. 3 is a sectional view taken along line III-III above. FIG. 4 is a schematic view of an embodiment of the calibration device of the present invention, FIG. 5 is an enlarged sectional view of a portion 5 in FIG. 4, and FIG. 6 is an enlarged sectional view of a portion 6 in FIG. FIG. 7 is a drawing showing a state in which the sensor of the measuring machine is attached to the one shown in FIG. 6, FIG. 8 is a flow chart of the measuring machine when the method of the present invention is carried out, and FIGS. 9 (a) and 9 (b). (C) and (d) are operation explanatory views of the three-way cock of FIG. 4, FIG. 10 (a) and (b) are operation explanatory views of the same four-way cock, and FIG. 11 is of FIG. FIG. 12 is a graph showing the relationship between the amount of injected acetone and the concentration in the thing, and FIG. 12 is a graph showing the relationship between the concentration in the air and the time at the time of measurement by the measuring instrument. 1 ... Measuring instrument, 2 ... Calibration device 3 ... Semiconductor sensor, 7 ... A / D converter 8 ... Arithmetic processing unit, 9 ... ROM 10 ... RAM, 11 ... Liquid crystal display unit 37 ... Air inlet with activated carbon filter, 39 …… 3-way cock 41 …… 4-way cock, 42 …… Closed conduit 44 …… Exhaust pipe, 46 …… Test tank 48 …… Gas-liquid inlet, 49 …… Pump

Front Page Continuation (72) Inventor Katsushi Nakano 1-17-1 Kitamamagome, Ota-ku, Tokyo Rico Techno Research Co., Ltd. (72) Inventor Yoichi Arai 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company In Ricoh (56) References Published by Shoko 49-4395 (JP, Y1)

Claims (2)

[Claims] 1. A gas concentration measuring instrument having a semiconductor sensor, wherein the semiconductor sensor is installed in a test tank installed in a gas circulation path, and the inside of the gas circulation path is cleaned with a clean gas. Fill the circulation path with clean gas,
After that, a standard gas is circulated in the gas circulation system passage, and the gas concentration measuring instrument is adjusted so that the output value of the semiconductor sensor corresponds to the gas concentration. 2. A gas circulation system passage, a gas supply port and a discharge port provided in the gas circulation system passage for supplying and discharging a clean gas to the gas circulation system passage, and a gas circulation system passage. A calibration device for a gas concentration measuring instrument, comprising a test tank and a gas-liquid inlet, and a pump provided in the gas circulation system passage for circulating gas in the gas circulation passage.