WO2015186407A1

WO2015186407A1 - Gas measurement device and measurement method

Info

Publication number: WO2015186407A1
Application number: PCT/JP2015/058265
Authority: WO
Inventors: 彰守川; 稲永　康隆; 河野　裕之; 柏野　敦彦; 智規近野
Original assignee: 三菱電機株式会社
Priority date: 2014-06-04
Filing date: 2015-03-19
Publication date: 2015-12-10
Also published as: JP5875741B1; JPWO2015186407A1

Abstract

A gas measurement device wherein: a light projection unit is provided at one end side of a hollow fiber into which gas to be measured is introduced; light from a light source is irradiated into the hollow fiber; a detector is disposed past the other end side of the hollow fiber, which is sealed by a transparent member; light passing through the hollow fiber is detected; a measurement and control unit measures the gas to be measured on the basis of the detected light; an optical filter unit is provided in a space between the other end of the hollow fiber and the detector and transmits light that has passed through the hollow fiber and is within the light absorption band of the gas; and the hollow fiber has a bent shape such that the detector is placed in a position outside of the area extending linearly from the light source of the light projection unit to the hollow fiber.

Description

Gas measuring device and measuring method

This invention relates to a gas measuring device and the like.

As a conventional gas measuring device, for example, it is used to measure the gas in oil in order to monitor the state of insulating oil inside oil-filled electrical equipment such as a transformer and a reactor. For example, the following patent document 1 discloses a specific example of such a method. In the gas analyzer disclosed in Patent Document 1 below, insulating oil is collected from the oil-filled electrical device body, gas dissolved in the insulating oil is extracted, and the extracted gas is introduced into the hollow fiber. The light introduced from one end of the hollow fiber by the LED as the light source is detected by a detection unit in the vicinity of the other end of the hollow fiber through the gas in the fiber, and calculation and diffraction are performed. Since there is light absorption in the hollow fiber according to the gas concentration, the gas amount can be measured from the output difference. In order to perform measurement according to the type of gas, a plurality of bandpass filters are installed in the vicinity of the light emitting unit.

Further, Patent Document 2 below discloses a gas detector including a light source, a measurement cell, an infrared detection element as an infrared sensor, a bandpass filter, and a heat conduction suppression unit.

JP 2012-242111 A (page 7, page 34 to page 8, line 11; FIG. 5) Japanese Patent Laying-Open No. 2013-185996 (page 4, page 37 to page 7, line 18, FIG. 1)

In the conventional gas measuring apparatus as described above, when the bandpass filter is heated by the heat derived from the light source, the optical characteristics of the bandpass filter, that is, the shift of the center wavelength and the half width (full width at half maximum) are Due to the fluctuation, there is a problem that stable measurement is difficult.
Also, when measuring multiple gases at the same time, switch the bandpass filter every fixed time to obtain the respective output, but the temperature is not constant immediately after switching the bandpass filter, so it is not stable and it is necessary to wait until it becomes stable Therefore, there was a problem that high-speed measurement was impossible.

The present invention has been made to solve the above-described problems, and realizes a stable measurement that is hardly affected by the heat from the light source, and obtains a gas measurement device that can measure at a higher speed. It is an object.

The present invention includes a hollow fiber into which a gas to be measured is introduced, a light projecting unit that is disposed on one end side of the hollow fiber and irradiates light from a light source into the hollow fiber, A detector that detects light that has passed through the hollow fiber at the tip of the other end that is sealed with a transparent member, and a measurement that measures the gas to be measured based on the light detected by the detector An optical filter provided in a gap between the control unit and the other end of the hollow fiber and the detector and having a transmission frequency band that transmits light in the light absorption band of the gas out of the light that has passed through the hollow fiber A gas measurement in which the hollow fiber is bent so that the detector is installed at a position other than an area extending linearly from the light source of the light projecting unit to the hollow fiber. Location.

In the present invention, it is possible to provide a gas measuring device and the like that can realize a stable measurement that is hardly affected by the heat from the light source and can measure at a higher speed.

It is a schematic sectional drawing which shows the gas measuring device by Embodiment 1 of this invention. It is the block diagram seen from the direction of the detector 25 of the rotation part 23 of FIG. It is a flowchart which shows operation | movement of the gas measuring device by Embodiment 1 of this invention. It is a figure which shows an example of the measurement result by Embodiment 1 of this invention. It is a schematic sectional drawing of the gas measuring device by a general NDIR method. It is a figure which shows the experimental result of the gas measuring device by a general NDIR method. It is a figure which shows the experimental result of the gas measuring device by Embodiment 1 of this invention. It is a schematic sectional drawing which shows the gas measuring device by Embodiment 2 of this invention. It is the schematic sectional drawing which extracted and showed a part of gas measuring device of FIG. It is a block diagram of the shielding board 30 seen from the detector 25 side of FIG. It is the figure which showed the change of the relative light quantity when changing the distance L1 of FIG. It is a schematic sectional drawing which shows the gas measuring device by Embodiment 3 of this invention. It is an expanded sectional view of the lens 24 vicinity in the gas measuring device of Embodiment 1 of this invention. It is an expanded sectional view of the lens 24 vicinity in the gas measuring device of Embodiment 3 of this invention. It is a schematic sectional drawing which shows the gas measuring device by Embodiment 4 of this invention. It is the block diagram which looked at the light-shielding plate 36 of FIG. 15 from the direction of the filament 16. FIG. It is a schematic sectional drawing which shows the gas measuring device by Embodiment 5 of this invention. It is a schematic sectional drawing which shows an example of the gas measuring device by Embodiment 6 of this invention. It is a schematic sectional drawing which shows another example of the gas measuring device by Embodiment 6 of this invention.

Hereinafter, a gas measuring device and the like according to the present invention will be described with reference to the drawings according to each embodiment.
In each embodiment, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.
Moreover, the gas measuring device which concerns on each embodiment is used in order to measure the gas which melt | dissolves in the insulating oil in oil-filled electrical equipment. However, the present invention is not limited to such applications, and the present invention can also be used for general gas measurement applications.

Embodiment 1 FIG.
1 is a schematic sectional view of a gas measuring apparatus according to Embodiment 1 of the present invention.
A light projecting unit 5, a hollow fiber 6, a detecting unit 7, a lock-in amplifier 8, and a measurement / control unit 9 are provided, and an oil-filled electrical device 10 and a gas sample extraction mechanism 11 are connected to these. .

The oil-filled electrical device 10 is, for example, an oil-filled transformer or an oil-filled reactor, and the inside thereof is filled with insulating oil. The gas sample extraction mechanism 11 is connected to the oil-filled electrical device 10 through the

pipes

12a and 12b. An extraction container 13 for extracting a gas dissolved (dissolved and mixed) in the insulating oil is provided in the gas sample extraction mechanism 11.

The gas sample extraction mechanism 11 is provided with a pump (not shown) for decompressing the inside of the extraction container 13. By decompressing the inside of the extraction container 13, a gas sample is extracted from the insulating oil inside the extraction container 13. The extracted gas sample is sent to the detection unit 7 through the pipe 14a. In the middle of the pipe 14a, a three-way valve 27 for switching the gas sample flow path, and a dirt removal filter 15 for removing mist (water, oil, etc.) and sulfur components contained in the gas sample are provided. . A pipe 14b is connected to one end side of the branch of the three-way valve 27. Further, the dirt removal filter 15 and the detection unit 7 are connected in order, and the pipe 14c is connected to the other end side so that the air is open.

The light projecting unit 5 is configured as follows. The light projecting unit 5 itself is a sealed and highly airtight casing. Infrared light generated from the filament 16 that is a light source is collected by the reflector 17 and optically connected to one end side of the hollow fiber 6 via a resonance chopper 18 that chops the collected infrared light. It is connected.

The curved inner wall surface of the reflector 17 serving as a light condensing part is in a mirror surface state in which gold or the like is deposited, and has a function of reflecting and condensing light including a wavelength to be measured. The reflector 17 has a spherical shape, an elliptical spherical shape, and the like. However, it is desirable to optimize the shape so that the light is condensed as much as possible on one end side of the hollow fiber 6. Further, light other than the measurement wavelength is not necessary for measurement, and far infrared rays (heat rays) having a wavelength of 5 μm or more act to heat the hollow fiber 6. Therefore, the inner wall surface of the reflector 17 is formed by depositing various dielectrics so as to be a dielectric layer such as alumina that reflects light in the wavelength region including the measurement wavelength or only light in the measurement wavelength instead of gold deposition. Also good.
The measurement wavelength region is a wavelength region of light corresponding to various gases measured by the measurement / control unit 9.

The resonance chopper 18 physically operates a pair of

blades

3a and 3b by electromagnetic force. The gap between the blade 3a and the blade 3b is periodically changed between 0.1 mm and 5 mm so that the infrared light is chopped. The frequency at which the blade chops is preferably in the range of 100 to 10000 Hz, but is 2000 Hz here.

The light projecting unit 5 and the detecting unit 7 are connected by a hollow fiber 6. The light projecting unit 5 is provided with a pipe 19 for discharging a gas sample and a pump 20. In the hollow fiber 6, the direction of infrared light and the direction of flow of the gas sample are reversed. That is, infrared light is conducted from the light projecting unit 5 to the detection unit 7 through the hollow fiber 6, while the gas sample is made to flow from the detection unit 7 to the light projection unit 5 through the hollow fiber 6. Yes. The light source may be an LED or a laser instead of the filament 16, and the means is not particularly limited as long as it emits mid-infrared light. Since some of the infrared light is far-infrared, LEDs and lasers also serve as heat sources and have the same problems as in the case of the filament 16. Also, the number need not be one, and a plurality may be used side by side.

In the first embodiment of the present invention, a gas sample to be measured and infrared light are passed through the hollow fiber 6, and the inside also serves as a conduction between the gas cell and the infrared light. The hollow fiber 6 has a characteristic that the optical path length of the infrared light can be increased, and at the same time, since the inner diameter is small, the heat conduction from the light projecting portion 5 is small.

The hollow fiber 6 can be manufactured by a known method such as sputtering of Ni, Al, Au, Ag or the like on a cylindrical base material such as quartz glass and then coating with a cyclic olefin polymer. A detailed description of the method is omitted. The hollow fiber 6 generally has an inner diameter of 0.5 to 1.0 mm, but here, the inner diameter of 0.7 mm was used. Although it is desirable that the hollow fiber 6 has a long length because of high sensitivity, it is difficult to manufacture the long hollow fiber 6, and a 3 m long fiber 6 was used here. The volume of the cell can be calculated from the inner diameter and the length, and in this embodiment is calculated as 1.15 mL (milliliter). In order to replace the gas sample to be measured inside the hollow fiber 6, the gas amount of about 2 to 3 times the internal volume is required at least, so the volume of the gas sample needs to be at least 4 mL.

The detection unit 7 is configured as follows. Although the detection unit 7 itself is a mere housing, it is wrapped with a heat insulating material such as urethane foam, and is kept warm so that the inside becomes a constant temperature. Further, unlike the light projecting unit 5, the detecting unit 7 does not need to have high airtightness. The gas sample introduction part 21 connected to the other end side of the hollow fiber 6 and the other end side of the pipe 14 b is provided with a glass window 22 that is a transparent member facing the other end side of the hollow fiber 6. That is, a glass window 22 is provided on the opposite side of the gas sample introduction portion 21 to the side where the other end of the hollow fiber 6 is connected, and the other end of the hollow fiber 6 is sealed with the glass window 22. Yes. The glass window 22 is made of a material that transmits infrared light, such as quartz glass.
Although the glass window 22 may be made of quartz glass alone, it may be a filter that removes light having a wavelength not related to measurement. For example, a short wave pass filter that removes infrared light of 5 μm or more known as heat rays may be used. Thereby, the influence of heat can be excluded. Specifically, the short wave pass filter is made of, for example, quartz glass coated with a multilayer film such as alumina on a base material such as sapphire and silicon, and has a function of blocking infrared light having a specific wavelength or more.

A rotation unit 23 is provided at a position facing the glass window 22 outside the gas sample introduction unit 21, and

bandpass filters

4 a, 4 b, 4 c, and 4 d are mounted therein. FIG. 2 is a configuration diagram viewed from the direction of the detector 25 of the rotating unit 23. As shown in FIG. 2, the four

bandpass filters

4a, 4b, 4c, and 4d are installed in the same circle. By rotating the rotating unit 23, the

bandpass filters

4a, 4b, 4c, and 4d are In order, they are appropriately selected so as to be on a straight line connecting the lens 24 and the detector 25. The order of rotation is 4a, 4b, 4c, 4d. Instead of the rotating unit 23, the

bandpass filters

4a, 4b, 4c, and 4d may be attached to a slide jig (not shown) that slides in a linear direction (for example, laterally) and may be switched by sliding.
The rotating unit 23 and the slide jig are used as a band-pass filter switching mechanism. The switching mechanism includes a movable portion corresponding to the rotating portion 23 and the like provided with a bandpass filter, and a support portion that movably supports the movable portion. Further, each of the single bandpass filters or the

bandpass filters

4a, 4b, 4c, and 4d and the switching mechanism thereof is an optical filter unit.

The

bandpass filters

4a, 4b, 4c, and 4d are made by coating a base material such as quartz glass, sapphire, or silicon with a multilayer film such as alumina, and have a role of blocking infrared light other than near the center wavelength. Since the absorption characteristics are different for each type of gas,

bandpass filters

4a, 4b, 4c, and 4d corresponding to each gas are provided. That is, each of the

bandpass filters

4a, 4b, 4c, and 4d has a transmission frequency band that transmits light in a light absorption band of a different type of gas, and the transmission frequency band is different. For example, when converted to wavelength,
3.05 μm for acetylene,
4.25μm for carbon dioxide,
4.70μm for carbon monoxide
For example, it may be appropriately selected according to the target gas type. The

bandpass filters

4a, 4b, 4c, and 4d have a characteristic of transmitting infrared light having a wavelength apart from the center wavelength by a certain range, and are defined by a half-value width. Although the influence of the spectrum of other interfering gases can be cut off by reducing the half-value width, there is a demerit that the light sensitivity decreases and the measurement sensitivity decreases, so depending on the spectral characteristics of other gases and the target measurement lower limit value. Set the half width. Further, the band-

pass filters

4a, 4b, 4c, and 4d may be a combination of a short wave pass filter and a long wave pass filter instead of a single band pass filter.

here,
Bandpass filter 4a is used for acetylene measurement.
The bandpass filter 4b is a transparent glass for background measurement,
The bandpass filter 4c is for measuring carbon dioxide,
The band pass filter 4d was used for measuring carbon monoxide.

The number of bandpass filters is four, but may be two, three, or five or more.
Note that the switching mechanism is not required when there is one bandpass filter. A lens 24 is provided in the gap between the rotating unit 23 and the glass window 22. The lens 24 may be fixed to the above-mentioned supporting portion that does not rotate and supports the rotating portion 23, or may be fixed by a dedicated support (not shown). Infrared light emitted from the other end of the hollow fiber 6 (the end on the detection unit 7 side) is not guided by a constant light beam, that is, a bundle of 0.7 mm, but is diffused, so that it is condensed by the lens 24. .
Since the lens 24 has a role of collecting infrared light, it is made of, for example, quartz and has a convex shape. The condensed infrared light is configured to be guided to the detector 25 having the detector element 31 through the band-pass filter 4a. The focal length and the lens diameter of the lens 24 are determined according to the diameter of the hollow fiber 6 and the distance between the lens 24 and the detector 25. Here, the focal length is 25 mm and the lens diameter is 8 mm. The detector 25 uses a photoconductive element such as PbSe, InSb, or MCT, a photomultiplier, or the like, but is not particularly limited here, and may be anything that can detect infrared light. The photoconductive element and photomultiplier used for the detector 25 have a characteristic that the sensitivity is higher as the temperature is lower. Therefore, the Peltier cooler 26 is installed to increase the sensitivity by cooling the entire detector 25.

It should be noted that the installation position of the resonant chopper 18 is preferably as far away from the detector 25 as possible. This is because the resonance chopper 18 is electromagnetically operated, so that not only electromagnetic noise is generated but also physical noise (vibration) is generated, so that the measurement sensitivity of the detector 25 is not affected. The gap between the blade 3a and the blade 3b of the resonance chopper 18 may be a gap of about 1 mm at maximum depending on the resonance frequency of the resonance chopper 18. As described above, the inner diameter of the hollow fiber 6 is 0.7 mm and there is not much difference in size. Therefore, in order to guide infrared light as much as possible inside the hollow fiber 6, the installation position of the resonance chopper 18 is set. Is preferably as close as possible to one end side of the hollow fiber 6 on the light projecting portion 5 side.

In this embodiment, the filament 16, one end and the other end of the hollow fiber 6, the lens 24, and the detector 25 are installed on the same straight line as an axis 37 a indicated by a one-dot chain line.

In this embodiment, the infrared light guide direction in the hollow fiber 6 and the gas sample flow direction are opposite, but they may be the same direction. In this case, the pipe 14b of the pipe 14 is inserted into the light projecting unit 5, the other end side of the pipe 14b extends to one end side of the hollow fiber 6, the pipe 19 and the pump 20 are provided in the detection unit 7, and the lower end of the pipe 19 is Connected to the gas sample introduction unit 21.

The lock-in amplifier 8 is electrically connected to the output from the detector 25 and the output of the resonance chopper 18. The output of the lock-in amplifier 8 is connected to the measurement / control unit 9. The measurement / control unit 9 has a built-in memory (not shown) for temporarily storing data. If necessary, the measurement / control unit 9 includes an AD conversion unit (not shown), and an external port (not shown) for transferring data to a personal computer or the like is provided in the measurement / control unit 9. Arithmetic processing may be performed by a personal computer or the like.

Although not shown, there are a power supply unit and a driver for supplying power to each of the filament 16, the resonance chopper 18, the pump 20, the rotating unit 23, the detector 25, the Peltier cooler 26, and the three-way valve 27 (both not shown). ), For example, is controlled by the measurement / control unit 9 so that each operates properly. The control lines from the measurement / control unit 9 to each unit are not shown because the drawings are complicated.

Next, the operation of the gas measuring apparatus according to Embodiment 1 will be described with reference to the flowchart of FIG. This operation is controlled by, for example, the measurement / control unit 9.

The filament 16 is lit for a certain time before starting the measurement, for example, 1 to 4 hours before (S1, S2). Since the filament 16 takes time to reach a stable state, it is lit in advance. However, if the amount of light is immediately stabilized, it may be lit immediately before the measurement.

Measurement is first performed on the background (first time) (S10). The gas sample to be measured in this case is atmospheric air, but a nitrogen + oxygen cylinder (mixing ratio 79:21) may be separately prepared and introduced. By switching the three-way valve 27, the gas sample flow path is set to cb (S11). By operating the pump 20, mist and sulfur components contained in the gas sample are removed by the dirt removal filter 15. The gas sample that has passed through the filter 15 is sent to the detection unit 7.

Next, a gas sample is sent into the gas sample introduction part 21 inside the detection part 7, and the gas sample introduction part 21 is filled with the gas sample. When the pump 20 is further operated, the gas sample inside the gas sample introduction part 21 flows into the light projecting part 5 through the hollow fiber 6, and is further discharged to the outside through the pipe 19 from the light projecting part 5. The The flow rate at this time is not particularly defined, but considering the operating range of the pump 20, a range of 0.1 to 1.0 L / min is appropriate. Considering the internal volume of the hollow fiber 6 as described above, it is only necessary to introduce a gas sample of at least about 4 mL, so that the operation time is about 2.4 to 24 seconds.
In practice, however, it is desirable to introduce the gas sample in a longer time in consideration of measurement stability, and it is desirable to determine the introduction time in consideration of the volume of the gas sample obtained from the insulating oil and the measurement time. . As a result, the gas sample to be analyzed (measured) is introduced into the hollow fiber 6. Here, the pump 20 is temporarily stopped, and the gas sample inside the hollow fiber 6 is brought into a stationary state. The reason for setting the stationary state is to avoid a decrease in the S / N ratio due to the inside of the hollow fiber 6 being in a flow state or being a source of noise due to vibration during operation of the pump 20 ( S12).

In the state where the inside of the hollow fiber 6 is filled with the gas sample, the rotation unit 23 is rotated and the bandpass filter 4a is used (S13). Infrared light emitted from the filament 16 passes through the gap between the

blades

3 a and 3 b of the resonance chopper 18 and is guided to one end of the hollow fiber 6. Infrared light guided from one end of the hollow fiber 6 is transmitted through the hollow fiber 6 and emitted from the other end of the hollow fiber 6. At this time, since the gas sample is air inside the hollow fiber 6, there is no absorption of infrared light except for carbon dioxide. Infrared light emitted from the other end of the hollow fiber 6 passes through the glass window 22 in the gas sample introduction portion 21 and is collected by the lens 24, passes through the bandpass filter 4a, and has an appropriate wavelength range. It is received by the detector 25 on the detection unit 7 side as infrared light. The detector 25 outputs an electrical signal having an intensity corresponding to the received light intensity of infrared light.

The output signal from the detector 25 is sent to the lock-in amplifier 8. The lock-in amplifier 8 removes noise by performing synchronous detection with the output signal from the resonance chopper 18. The output signal from which the noise has been removed is subjected to calculation of moving average processing in the measurement / control unit 9, and background data is stored in the memory in the measurement / control unit 9 (S14).

Next, the rotation unit 23 is rotated after a predetermined time to switch from the bandpass filter 4a to 4b (S15, S16). Similarly, the output signal from the detector 25 is synchronously added (synchronized) by the lock-in amplifier 8. Then, a moving average process is performed on the output signal from which noise has been removed, and the result is stored in the memory in the measurement / control unit 9 as background data. Next, by rotating the rotator 23, the bandpass filters 4b to 4c and the bandpass filters 4c to 4d are switched to perform the same measurement, and the data is stored in the memory in the measurement / control unit 9 (S14-S16). repeat).

This completes the first background measurement (S17). In this background measurement, except for carbon dioxide, since the gas component that is the measurement object is usually not included, this measurement value is regarded as 0 ppm.

Next, the gas component contained in the insulating oil is measured (S20). Only the gas sample is different, and the measurement flow is the same as the background measurement. Insulating oil is collected from the oil-filled electrical device 10 via the pipe 12a. The collected insulating oil is sent to the gas sample extraction mechanism 11. In order to extract the gas sample dissolved in the insulating oil, the extraction container 13 of the gas sample extraction mechanism 11 is decompressed. This extracts a gas sample from the insulating oil.

The gas sample flow path is set to ab by switching the three-way valve 27 (S21). By operating the pump 20, mist and sulfur components contained in the gas sample are removed by the dirt removal filter 15. The gas sample that has passed through the filter 15 is sent to the detection unit 7.

The gas sample is sent to the gas sample introduction unit 21 inside the detection unit 7 to fill the gas sample introduction unit 21 with the gas sample. Next, the pump 20 provided on the light projecting unit 5 side is further operated. Thereby, the gas sample inside the gas sample introduction part 21 flows from the detection part 7 to the light projecting part 5 through the inside of the hollow fiber 6, and is further discharged from the light projecting part 5 to the outside through the pipe 19. At this time, a gas sample to be analyzed is introduced into the hollow fiber 6. Here, the pump 20 is temporarily stopped, and the gas sample inside the hollow fiber 6 is brought into a stationary state (S22).

The bandpass filter to be used is set to the bandpass filter 4a (S23), and the infrared light emitted from the filament 16 passes through the gap between the

blades

3a and 3b of the resonance chopper 18 and is guided to one end of the hollow fiber 6. Infrared light guided from one end of the hollow fiber 6 is transmitted through the hollow fiber 6 and emitted from the other end of the hollow fiber 6. At this time, infrared light is absorbed inside the hollow fiber 6 by the flowing gas sample. Infrared light emitted from the other end of the hollow fiber 6 passes through the glass window 22 in the gas sample introduction portion 21 and is collected by the lens 24, passes through the bandpass filter 4a, and has an appropriate wavelength range. It is received by the detector 25 on the detection unit 7 side as infrared light. The detector 25 outputs an electrical signal having an intensity corresponding to the received light intensity of infrared light.

The output signal from the detector 25 is sent to the lock-in amplifier 8. The lock-in amplifier 8 removes noise by performing synchronous detection with the output signal from the resonance chopper 18. The output signal from which the noise has been removed is subjected to calculation of moving average processing in the measurement / control unit 9, and the gas component data is stored in the memory in the measurement / control unit 9 (S24).

Thereafter, similarly to the background measurement, the bandpass filter 4a is switched to 4b by rotating the rotating unit 23 after a predetermined time has elapsed (S25, S26). Similarly, the output signal from the detector 25 is sent to the lock-in amplifier 8, and the lock-in amplifier 8 removes noise by synchronous addition (synchronous detection) with the output signal from the resonance chopper 18. The output signal from which the noise has been removed is subjected to a calculation of moving average processing in the measurement / control unit 9, and gas component data is stored in a memory in the measurement / control unit 9. Next, by rotating the rotator 23, the bandpass filters 4b to 4c and the bandpass filters 4c to 4d are switched to perform the same measurement, and the data is stored in the memory in the measurement / control unit 9 (S24-S26). repeat). This completes the measurement of the gas sample contained in the insulating oil (S27).

Next, the second background measurement (S30) is performed in the same manner as the first time (S31-S37). Since the operation is the same as the first time, the description is omitted.

Finally, the measured value is calculated from the data stored in the measurement / control section 9 (S40). Calculate the average of the first and second measurements in the background. The average calculation may be either a simple average or a logarithmic average, but here it is a simple average. The background voltage value is not constant in time and always fluctuates due to the influence of drift noise. By this averaging operation, it is possible to cope with drift noise whose background value changes with time, and to realize measurement that is hardly affected by noise.

After obtaining the measured value of the background, using this value as a reference, the difference from the measured value at the time of gas component measurement is obtained, and the difference in sensor output voltage (unit is V) is compared with the previously calculated calibration curve. Calculate and output the gas concentration.

When the concentration of gas from the insulating oil is expected to be relatively high, the sensor output voltage difference, that is, the output voltage difference of the detector 25 (hereinafter the same) is larger than the background fluctuation. The ground measurement may be performed only once.

FIG. 4 shows an example of the measurement result. Here, the gas component was measured by using a gas sample of 5 ppm of acetylene instead of the extracted gas of the insulating oil. Specifically, the outlet of a gas cylinder of 5 ppm acetylene is directly connected to the gas sample introduction part 21. The bandpass filter was fixed by using only the bandpass filter 4a for measurement. The measurement is performed by switching the gas sample every 10 minutes, in the order of background (air) → acetylene 5 ppm → background (air). The introduction time of the gas sample was 2 minutes.

As shown in FIG. 4, when the gas sample is introduced, the sensor output voltage is unstable, so it is not subject to calculation. The moving average value is calculated by stopping the introduction after 2 minutes and measuring 8 minutes until 10 minutes later. As a result, the measured value A of the background (first time) was 2.081V. The sensor output voltage B when acetylene was 5 ppm was 2.075V. The background (second time) sensor output voltage A 'was 2.079V. Therefore, the measured value of the background is the average value of A and A 'and is 2.080V. The sensor output voltage difference is the difference between 2.080V and 2.075V, which is 0.005V. Since acetylene 5 ppm has a relatively low concentration and drift noise cannot be ignored compared to the sensor output voltage difference, a method of measuring the background before and after the measurement of the gas sample is effective.

Next, the experimental results in this embodiment will be shown. In addition to the first embodiment shown in FIG. 1, an experiment is also performed for a gas measuring apparatus using a general NDIR (non-dispersive infrared absorption spectroscopy) method as shown in FIG. 5, and the results of both are compared. FIG. 5 shows a gas measuring device using the transmission cell 1 instead of the hollow fiber 6. In FIG. 5, the permeation cell 1 is provided with a gas sample inlet 1a and a gas sample outlet 1b. The gas sample inlet 1a is connected to the pipe 14b and the dirt removal filter 15, and is configured so that the background or insulating oil gas can be introduced as in FIG. The light source 2 is the same as the filament 16 in FIG. 1, and infrared light is irradiated from one end side into the transmission cell 1 in which a background or insulating oil gas is sealed. Infrared rays are transmitted through the transmission cell 1 and guided to the detector 25 via the band-

pass filters

4 a and 4 b of the rotating part provided on the other end side in the transmission cell 1.

The transmission cell 1 is configured so that the inside reflects infrared light. The material is not limited, but generally it is made of stainless steel because metal is often used. The gas sample to be analyzed is introduced into the permeation cell 1 from the gas sample inlet 1a along the direction a, and discharged from the gas sample outlet 1b to the outside of the permeation cell 1 along the direction b.

In the configuration shown in FIG. 5, most of the heat from the light source 2 reflects the inner wall of the transmission cell 1 to heat the

bandpass filters

4a and 4b. It is also heated by heat transfer from the metal portion of the transmission cell 1. When the bandpass filter 4a is heated, the transmission characteristics of the filter, such as the center wavelength and the half width, change. In addition, when switching from the bandpass filter 4a to the bandpass filter 4b, a physical movement in the transmission cell 1 causes the temperature to change and causes noise. For this reason, with the configuration shown in FIG. 5, it is difficult to measure with high accuracy when measuring a plurality of gas sample components at high speed.

The experiment was performed using a gas of 5 ppm acetylene as a sample gas, and compared each of the apparatus shown in FIG. 1 showing the first embodiment and the apparatus shown in FIG. 5 (hereinafter referred to as “conventional method”). In the experiment, only the gas component is measured without measuring the background. That is, in the flowchart of FIG. 3, only the measurement of the gas component (S20) was performed. The switching time of each of the

bandpass filters

4a, 4b, 4c, and 4d is 120 seconds.
That is, after 120 seconds had elapsed, for example, the experiment was conducted for a total of 480 seconds assuming that the bandpass filter 4a was switched to 4b.

FIG. 6 shows the results of measurement by a conventional gas measuring device. Immediately after switching of any of the

bandpass filters

4a, 4b, 4c, and 4d, peak noise is generated as indicated by a round circle. It was found that noise was included for 40 seconds immediately after switching of the bandpass filter, and this was not suitable for measurement in this time domain.

FIG. 7 shows a measurement result in the gas measuring apparatus of the present embodiment. It can be seen that the peak noise immediately after switching as shown in FIG. 6 does not occur and is stable. Even if the band-pass filter is switched, noise is not mixed and immediately stabilized, thereby achieving an effect of realizing high-speed measurement.
In addition to the peak noise, the cause of the noise mixing is not only the influence of the heat transmitted to the

bandpass filters

4a, 4b, 4c, 4d already described, but also the vibration generated when the rotating part 23 rotates is the resonance chopper. 18 is transmitted to noise. This is because the resonance chopper 18 is susceptible to vibration because it transmits or blocks infrared light by opening and closing the

blades

3a and 3b. Therefore, as shown in FIG. 1 shown in the first embodiment, separating the rotating unit 23 and the resonant chopper 18 as much as possible leads to noise reduction.

As described above, according to the first embodiment, noise generation is small even when the band-pass filter is switched, so that more stable high-speed measurement can be realized.

Embodiment 2. FIG.
FIG. 8 is a schematic cross-sectional view of a gas measuring device according to Embodiment 2 of the present invention.
The difference from the configuration shown in FIG. 1 of the first embodiment is that the infrared light derived from the glass window 22 is guided directly to the detector 25 via the band-pass filter 4a without using the lens 24.
Since the infrared light derived from the glass window 22 is diffused due to the absence of the lens 24, the infrared light reaching the detector 25 decreases.

The hollow fiber 6 is different from general solid optical fibers, and the light propagation area is air, so the numerical aperture cannot be defined. The hollow fiber 6 is a multimode transmission, and the incident angle at the light entrance of the hollow fiber 6 allows arbitrary light to enter, but for higher-order modes, that is, the mode where the incident angle of the hollow fiber 6 is large, Since loss increases in the hollow fiber 6, the transmission efficiency decreases. Since the diffusion state of the light from the exit of the hollow fiber 6 cannot be obtained from the numerical aperture, the degree of diffusion from the exit of the hollow fiber 6 was examined experimentally here.

FIG. 9 shows only the optical member (optical system portion) in FIG. 8, and the description of some members is omitted. An angle between a straight line connecting one end side (light entrance) of the hollow fiber 6 and the end of the reflector 17 and a straight line connecting one end side of the hollow fiber 6 and the filament 16 serving as a light source is defined as θ ₁ . Since the filament 16 can be approximated as a point light source, the incident angle of the light emitted from the filament 16 to the hollow fiber 6 has a maximum θ ₁ .

About the other end side (light exit) of the hollow fiber 6, the shielding board 30 is installed in the position of the distance L1 from the other end side of the hollow fiber 6. FIG. FIG. 10 is a configuration diagram of the shielding plate 30 as viewed from the detector 25 side. The shielding plate 30 is a plate material that does not transmit light, such as aluminum, with a hole having a diameter r. In the experiment, the amount of light reaching the detector element 31 in the detector 25 was measured by changing the distance L1. The diameter r was 1 mm, and the distance L2 between the other end of the hollow fiber 6 and the detector element 31 was 40 mm.
The detector element 31 has a rectangular shape of 3 × 3 mm (in this case, a square).

FIG. 11 is a diagram showing a change in relative light quantity when the distance L1 is changed from 0 mm to 40 mm. The relative light quantity indicates the ratio of the output voltage at each L1 when the output voltage from the detector 25 without the shielding plate 30 is 1.0.

According to FIG. 11, the relative light amount decreases as L1 increases. Here, when L1 which is 0.95 as a relative light quantity is read, L1 is 10 mm. When the relative light quantity is 1.0 to 0.95, the light quantity is reduced by 5%. However, since there is substantially no problem in terms of the sensitivity of the detector 25, there is almost no reduction in sensitivity from L1 up to 10 mm. It is considered. At this time, θ _{2 in} FIG. 9 is obtained by the following equation.

θ ₂ = arctan (r / 2 / L1)

From this experimental result, when L2, that is, the distance from the other end of the hollow fiber 6 to the detector element 31 is 10 mm or less, the light emitted from the other end of the hollow fiber 6 is hardly lost and detected. The device element 31 can receive light, but if L2 exceeds 10 mm, the loss cannot be ignored.
As shown in FIGS. 8 and 9, the other end of the hollow fiber 6 and the glass window 22 must be flush with each other (constitute the same plane) so that a gap of about 2 mm is required because of the gas flow path. Furthermore, the glass window 22 needs to have a thickness of at least 1 mm in consideration of the strength, which is difficult. In practice, the distance between the glass window 22 and the detector element 31 is 7 mm or less, which satisfies this experimental result. It becomes. Therefore, when the thickness of the rotating part 23 is 7 mm or less, as shown in FIG. 8 of the second embodiment, it has been found that there is no problem in terms of sensitivity even if the lens 24 is not used.

However, when the thickness of the rotating part 23 cannot be reduced too much, the configuration shown in FIG. 1 shown in the first embodiment results in higher sensitivity. It is desirable to decide which one to choose from the viewpoint of balance.

The configuration and operation of the other parts of the gas measurement device according to the second embodiment are the same as the configuration and operation of the corresponding part of the gas measurement device according to the first embodiment, and therefore description thereof is omitted.

The effect of the second embodiment is the same as in the first embodiment, since the generation of noise is small even when the band-pass filter is switched, stable high-speed measurement can be realized, but measurement with a smaller number of components is possible. is there.

Embodiment 3 FIG.
FIG. 12 is a schematic cross-sectional view of a gas measuring device according to Embodiment 3 of the present invention. The differences from the configuration shown in FIG. 1 of the first embodiment are as follows. In FIG. 1, the position of the lens 24 is placed in the gap between the rotating unit 23 and the glass window 22, but in FIG. 12 showing the present embodiment, the position of the lens 24 is in the gap between the rotating unit 23 and the detector 25. The point is different. Here, the lens 24 is a concave lens. FIG. 13 is an enlarged view of the vicinity of the periphery including the lens 24 in FIG. 1 and shows the state of diffusion and collection of infrared light emitted from the hollow fiber 6. FIG. 14 is an enlarged view of the vicinity including the lens 24 of FIG.

At the position of the lens (convex lens) 24 in FIGS. 1 and 13, as shown in FIG. 13, the lens 24 immediately collects infrared light emitted from the hollow fiber 6, and the bandpass filter 4a is heated. Cheap. On the other hand, in the configuration shown in FIG. 14, since the infrared light from the hollow fiber 6 is once diffused, the bandpass filter 4a is hardly heated. However, since it is necessary to use a lens (concave lens) 24 according to the third embodiment having a larger curvature than that of the lens (convex lens) 24 according to the first embodiment, it is difficult to condense, and the measurement sensitivity may be slightly different depending on conditions. Since it may be lowered, it is desirable to select either the configuration of the first embodiment or the third embodiment in accordance with the balance between measurement sensitivity and high-speed measurement.

Since the configuration and operation of other parts of the gas measurement device according to the third embodiment are the same as the configuration and operation of the corresponding portion of the gas measurement device according to the first embodiment, description thereof will be omitted.

As in the first embodiment, the effect of the third embodiment is that the generation of noise is small even when the band-pass filter is switched, so that stable high-speed measurement can be realized, and further measurement without being affected by heating. Is possible.

Embodiment 4 FIG.
FIG. 15 shows a schematic sectional view of a gas measuring apparatus according to Embodiment 4 of the present invention. The difference from the configuration shown in FIG. 1 of the first embodiment is as follows. In the configuration of FIG. 15, a rotary chopper 35 is installed instead of the resonant chopper 18 shown in FIG.

A known configuration can be applied to the rotary chopper 35, which includes, for example, a light shielding plate 36 formed of a thin plate of stainless steel or aluminum, a motor (not shown) that rotates the light shielding plate 36, and the like. FIG. 16 is a configuration diagram of the light shielding plate 36 as viewed from the direction of the filament 16. As shown in FIG. 13, four holes 36 a are formed, and transmission and blocking of infrared light is realized by rotating the light shielding plate 36. The number of holes 36a is not necessarily four, and may be any number. As in the case of the resonant chopper 18, the transmission and cutoff frequencies generated by the rotation are suitably in the range of 100 to 10000 Hz, but here, 2000 Hz as in the first embodiment.

Since the configuration and operation of other parts of the gas measurement device according to the fourth embodiment are the same as the configuration and operation of the corresponding portion of the gas measurement device according to the first embodiment, the description thereof is omitted.

The effect of the fourth embodiment is that, as in the first embodiment, noise generation is small even when the bandpass filter is switched, so that stable high-speed measurement can be realized. Therefore, the effect of blocking heat is greater.

Embodiment 5 FIG.
FIG. 17 is a schematic sectional view of a gas measuring apparatus according to Embodiment 5 of the present invention. The difference from the configuration shown in FIG. 1 of the first embodiment is as follows. In the configuration shown in FIG. 17, the wavelength tunable filter 29 is installed instead of the rotating unit 23 and the

bandpass filters

4a, 4b, 4c, and 4d shown in FIG.

The wavelength tunable filter 29 is a mechanism in which optical characteristics (including the transmission frequency band) change when the applied voltage of the film is changed according to the Fabry-Bellows interference principle. The

bandpass filters

4a, 4b, 4c, and 4d are not mechanically rotated and switched as in the first embodiment, but the characteristics of the filter are electrically switched. There is almost no movement of air, and the temperature change with time is small.
It should be noted that the portion consisting of the

bandpass filters

4a, 4b, 4c, and 4d and the switching mechanism thereof, and the portion consisting of the wavelength variable filter 29 and the power supply unit (not shown) for changing the applied voltage in each of the above embodiments, Also referred to as a variable optical filter section.

Further, as in the second embodiment, when the wavelength tunable filter 29 can be made sufficiently thin, the lens 24 may be omitted.

Although the lens 24 is installed on the glass window 22 side, it may be installed on the detector 25 side as in the third embodiment. Since the structure of the other part of the gas measuring device according to the fifth embodiment is the same as the structure of the corresponding part of the gas measuring device according to the first embodiment, the description thereof will be omitted.

The operation is almost the same as in the first embodiment, but instead of switching the

bandpass filters

4a, 4b, 4c, and 4d in the first embodiment by the rotating unit 23, the applied voltage of the wavelength tunable filter 29 is changed to change the filter. It is different in changing the characteristics.

The effect of the fifth embodiment is that, as in the first embodiment, the wavelength tunable filter 29 is not heated, so that stable high-speed measurement can be realized. Further, since there is no mechanical operation, more stable measurement can be performed. It becomes possible. In addition, a more space-saving device can be realized.

Embodiment 6 FIG.
FIG. 18 shows a schematic sectional view of a gas measuring apparatus according to Embodiment 6 of the present invention. The difference from the configuration shown in FIG. 1 of the first embodiment is as follows. In the configuration shown in FIG. 18, a part of the hollow fiber 6 shown in FIG. 1 is wound in a round shape to form a spiral shape or a wound coil shape. As a result, the filament 16 and one end of the hollow fiber 6, i.e., the region near the resonance chopper 18, are placed on the same straight line as shown by the one-dot chain line axis 37 b. Further, the detector 25, the lens 24, and the other end of the hollow fiber 6, that is, the region near the gas sample introduction portion 21, are installed on the same straight line as shown by the one-dot chain line 37c. Note that the hollow fiber 6 may be bent so that the shaft 37b and the shaft 37c form an angle with each other, instead of winding the hollow fiber 6 in a bowl shape.

In FIG. 18, the three-way valve 27, the

pipes

14a and 14b, the extraction container 13, the oil-filled electrical device 10, the gas sample extraction mechanism 11, and the

pipes

12a and 12b are omitted in FIG. The connections are the same as in FIG.

Part of the heat generated from the filament 16 is reflected by the reflector 17, and the heat has a characteristic of linearly transmitting around the shaft 37b. That is, the area 38 tends to be hot. If the distance from the filament 16 is increased, it is less susceptible to heat, but the area 38 tends to be relatively hot compared to its surroundings. Therefore, the influence of heat can be further reduced by not installing the bandpass filter 4a and the detector 25 in the cylindrical range including the area 38, that is, the shaft 37b. An appropriate range of the radius r of the cylindrical range depends on the output of the filament 16, but 3 cm or more is necessary. On the other hand, in FIG. 1 shown in the first embodiment, the bandpass filter 4a and the detector 25 are included in a cylindrical range including the shaft 37a, and the influence of heat cannot be completely excluded. Other configurations and operations are the same as those in the first embodiment.
That is, the hollow fiber 6 is connected to the detector 25, for example, the shaft 37b that is the optical axis from the filament 16 that is the light source and one end of the hollow fiber 6 to the hollow fiber 6, and the other end of the hollow fiber 6. What is necessary is just to make it the shape which the axis | shaft 37c used as the optical axis to the detector 25 from the other end of the hollow fiber 6 makes an angle mutually. The hollow fiber 6 is bent into, for example, a U shape or an L shape as shown in FIG. The bent angle is not limited to 90 degrees and 180 degrees. That is, the angle θ at which the shaft 37b and the shaft 37c intersect may be 90 degrees as shown in FIG. 19, or may be 60 degrees, for example. As a result, a portion where the detector 25 and the lens 24 are located can be set at a position away from the area 38 extending linearly along the hollow fiber 6 from the light projecting portion 5 having the filament 16.
In the configuration example of FIG. 18, since the hollow fiber 6 is bent into a wound coil shape or a U shape, the shaft 37b and the shaft 37c form an angle of 180 degrees with each other (parallel and opposite directions) and overlap each other. The distance is set so as not to become. In such a configuration, for example, the substantial exclusive area of the gas measuring device is small compared to the case where the L-shaped hollow fiber 6 is used (the exclusive length in the vertical direction of the drawing of FIG. 18 is short), and actually It is preferable when installing a gas measuring device.
More broadly, the hollow fiber 6 has, for example, one bent shape so that the detector 25 is installed at a position other than the area 38 extending linearly from the light source 2 of the light projecting unit 5 to the hollow fiber 6. Have.

The effect of the sixth embodiment is that stable high-speed measurement can be realized as in the first embodiment, but more stable high-speed measurement can be realized by suppressing the heating of the bandpass filter 4a.

Note that the present invention is not limited to the above embodiments, and includes all possible combinations thereof.

Industrial applicability

The gas measuring device according to the present invention is applicable to gas measuring devices in various fields.

Claims

A hollow fiber in which a gas to be measured is introduced;
A light projecting unit disposed on one end of the hollow fiber to irradiate light from a light source inside the hollow fiber;
A detector for detecting light that has passed through the interior of the hollow fiber at the other end side sealed with the transparent member of the hollow fiber;
Based on the light detected by the detector, a measurement / control unit that measures the gas to be measured,
An optical filter unit provided in a gap between the other end of the hollow fiber and the detector, and having a transmission frequency band that transmits light in a light absorption band of the gas out of the light that has passed through the hollow fiber;
With
The gas measuring device having a shape in which the hollow fiber is bent so that the detector is installed at a position other than an area linearly extending from the light source of the light projecting unit to the hollow fiber.
The gas measuring device according to claim 1, further comprising a condensing lens in a gap between the transparent member of the hollow fiber and the detector.
3. The gas measuring device according to claim 2, wherein the condensing lens is provided in a gap between the optical filter unit and the detector.
The gas measuring device according to any one of claims 1 to 3, wherein the optical filter section has a variable transmission frequency band.
The gas measuring device according to claim 4, wherein the optical filter unit is a wavelength tunable filter whose transmission frequency band changes when the applied voltage is changed.
The gas measurement according to any one of claims 1 to 5, wherein a rotary chopper or a resonant chopper that intermittently blocks light is installed in a gap between the light source of the light projecting unit and one end of the hollow fiber. apparatus.
The gas measuring device according to any one of claims 1 to 6, wherein a short wave pass filter for removing infrared light of 5 µm or more is provided instead of the transparent member.
The said light projection part has a condensing part which condenses the light from the said light source, The said condensing part condenses the light of the wavelength range containing a measurement wavelength. The gas measuring device described in 1.
Introduce the gas to be measured into the hollow fiber,
Irradiating light from a light projecting unit having a light source inside the hollow fiber from one end side of the hollow fiber,
At the tip of the other end sealed by the transparent member of the hollow fiber, light that has passed through the hollow fiber is detected through the optical filter that transmits light in the light absorption band of the gas. Detect with the instrument,
Based on the detected light, measure the gas to be measured,
A gas measurement method using a hollow fiber having a shape bent so that the detector is installed at a position other than an area extending linearly from the light source of the light projecting unit to the hollow fiber.