JPH03110452A - Measuring device for transmittance of fume - Google Patents

Abstract

PURPOSE:To enhance measurement precision by converting measuring light and calibrat ing light into intermittent light with a chopper and performing photoelectric conversion therefor and thereafter sending an electric signal to a controlling part and herein calculating transmittance and absorptivity of light and substituting the inside of the space between a flooding/photodetecting part and a reflecting part with clean air. CONSTITUTION:One part of light emitted from a light source 6 is focused to a first holes 21 of the rotary sector 20 of a chopper device 15 via a projection lens 7 as measuring light a and also projected to a reflection part 2 via a first objective lens 5 as intermittent light. The measuring light a reflected by the mirrors 2a, 2b of the reflection part 2 is introduced into a photoelectric conversion part 12 via a half-mirror 8 and a second objective lens 9. An electric signal is inputted to a controlling part 19 via a pre-amplifier circuit part 13. On the other hand, calibrating light b is converted into intermittent light by the chopper device 15. This intermittent light is passed through the lens 5 and thereafter photoelectrically converted 12 similarly as the measur ing light a via a prism 14 and the mirror 8. Thereafter an electric signal is inputted to the controlling part 19. Herein transmittence of absorptivity of light is calculated and output to the prescribed part.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a smoke transmittance measuring device for measuring the light transmittance or extinction coefficient inside a road tunnel or the like.

(Prior art) Conventionally, this type of smoke transmittance measuring device has a light emitting part and a light receiving part separated by about 100 meters, and light is transmitted from the light emitting part into the smoke in which soot, dust, etc. are floating. , and measured its transmittance.

The above-mentioned device is equipped with a calibration function to compensate for decreases in measured values due to luminous flux reduction of the light source of the light emitter, deterioration of the light receiver over time, dirt on the lens surface, etc., and the calibration is performed at regular intervals. and corrected the decrease. Further, the absolute value (100%) was set either by visual inspection at the measurement site or by recording the measured value and setting the highest value.

(Problem to be solved by the invention) The above conventional technology has the following problems.

■ Since the gain is adjusted by several percent at each fixed cycle, an error of several percent is unavoidable in terms of accuracy.

■ Because the setting of the insulation value (100%) was adjusted visually, there was a risk that the error would become large.

■ Because the emitter and receiver are 100 meters apart, on-site adjustments such as optical axis alignment and gain adjustment took time.

■ Measurement accuracy was poor due to noise and drift in the measurement processing section.

An object of the present invention is to provide a smoke transmittance measuring device that is easy to adjust and has good measurement accuracy.

(Means for Solving the Problems) In order to achieve the above object, the present invention arranges a light emitting/receiving section and a reflecting section to face each other, and the light emitting/receiving section receives light projected from the light emitting/receiving section. In a smoke transmittance measurement device that measures the light transmittance or extinction coefficient of a layer of smoke particles floating between a reflective part and a reflective part, a light source and a light source are provided on a light emitting/receiving part that is provided integrally with the reflective part. a projection lens and an objective lens for projecting the measurement light from the reflection section onto the reflection section; a photoelectric conversion section that enters the measurement light reflected at the reflection section through a half mirror and converts it into an electrical signal; a light guide means for introducing the calibration light from the light source into the photoelectric conversion unit via the half mirror; and a chopper means disposed midway between the projection lens and the objective lens for making the measurement light and the calibration light into intermittent light. and a light switching means that alternately switches between the calibration light and the measurement light introduced into the photoelectric conversion section via the half mirror, and further inputs the electric signal from the photoelectric conversion section and adjusts the light transmittance. and a control unit that calculates an extinction coefficient;
The present invention is characterized in that an Mjl removing means is provided for replacing the space between the light emitting/receiving section and the reflecting section with clean air in order to set the absolute value.

(Function) Since the above means is adopted, the measurement light and the calibration light are made into intermittent light by the chopper means, are converted into electric signals by the photoelectric conversion part, and then enter the control part, where the light transmittance and extinction coefficient are determined. The control unit continuously compares and calculates the two beams of measurement light and calibration light, and does not require a calibration function at regular intervals.

Furthermore, the control unit can calculate the light transmittance and extinction coefficient using the values obtained by subtracting the measured value when the measuring light is cut off by the chopper means (0% calibration value) from each measured value of the measuring light and the calibration light. This makes it possible to remove noise, drift, etc. from measured values.

Further, the absolute value (100%) of the transmittance is set by operating the smoke removal means, and the absolute value is adjusted by the control section.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a configuration diagram showing a first embodiment of the smoke transmittance measuring device of the present invention, in which 1 is a light emitting/receiving section, 2 is a reflecting section, 2a,
2b is the mirror of the reflecting section 2; 3 is soot and dust;

4 is a casing, 4a, 4b are apertures, 5 is a first objective lens, 6 is an incandescent lamp as a light source, 7 is a projection lens, 8 is a half mirror, 19 is a second objective lens, IO is an aperture for limiting the field of view, 11 is a diffuser 12 is a photoelectric conversion section, 13 is a preamplifier circuit section, 14 is a prism serving as a light guide means, 15 is a chopper means, 16 is an electric motor for the chopper, 17
18 is a light switching means, 19 is a control unit, a is a measurement light, and b is a calibration light.

In the figure, a light emitting/receiving section 1 and a reflecting section 2 are installed facing each other and integrally, and the light projected from the light emitting/receiving section 1, that is, the measurement light and the calibration light, The light transmittance or absorption coefficient of a layer of soot, soot fi3, etc. floating between the reflector 2 and the reflector 2 is measured.

Specifically, the casing 4 of the light emitting/receiving section 1 is provided with openings 4 for light entry/exit at positions corresponding to the mirrors 2a and 2b of the reflecting section 2.
a, 4b are formed, a first objective lens 5 is arranged corresponding to the light emitting aperture 4a, and a light source 6 and the first objective lens 5
A projection lens 7 and chopper means 15 are arranged between them. Further, at a position corresponding to the light incidence opening 4b, a half mirror 8 and a second measuring light a from the half mirror 8 are provided.
Objective lens 9. Aperture 10. A photoelectric conversion unit 12 that performs photoelectric conversion upon input through the diffusion plate 11 and a preamplifier circuit unit 13 that amplifies the output electrical signal from the photoelectric conversion unit 12 are provided.

A part of the light emitted from the light source 6 is sent to the prism 1 as a calibration light.
4. The light enters the photoelectric conversion section 12 via the half mirror 8 or the like. A chopper means 15 is disposed between the projection lens 7 and the first objective lens 5, and the chopper means 15 makes the measurement light a and the calibration light intermittent light.
The measurement light a and the calibration light S are selectively made incident on the photoelectric conversion unit 12 via the light source.

FIG. 2 is a front view of the chopper means 15, showing a disc-shaped rotating sector 20 with a plurality of holes 21 in the circumference, and a frequency of the chopper light produced by the rotating sector 20.
In order to prevent the influence of noise from, for example, a sodium lamp in a tunnel, the electric motor 16 shown in FIG. 1 rotates the rotating sector 20 at a frequency that is not a multiple of the primary power source frequency. .

Figure 3(,) is a front view of the optical switching means 17, Figure 3(b)
is a side view of the optical switching means 17, with a 180° angle on the circumference.
The rotating plate 22 in which the elongated hole 23 is formed in the range of
It is composed of an electric motor 18 shown in the figure.

The control section 19 is an arithmetic processing device that receives an electric signal from the preamplifier circuit section 13 and calculates a light transmittance or extinction coefficient based on this electric signal.

FIG. 4 shows electrical signals VA and V from the preamplifier circuit section 13.
The control section 19 calculates the light transmittance and extinction coefficient based on this electric signal (voltage value).

That is, in general, the light transmittance TL of a layer such as the dust 3 is expressed by the following equation 0.

TL=J・(VA/Vl) ・・・・・・■ However,
J is a coefficient.

However, since the electrical signals VA and V contain noise and drift, it is necessary to remove these. Therefore 0
Using the value ve when the measurement light a is blocked during % calibration, (V*Vc) can be used as the value of the measurement light a, and (V'A Vc) can be used as the value of the calibration light S.

Therefore, the light transmittance TL' without error is given by the following formula %. Moreover, the extinction coefficient is expressed by the following 0 formula.

K = (1/2L)・gog(1/Tt') """
(2) However, L is the distance between the active light receiving section 1 and the reflecting section 2 in FIG.

FIG. 5 is a configuration diagram showing a smoke removal means, in which 24 is a smoke removal tube surrounding the space between the reflecting part 2 and the casing 4, and 25 is a supply of clean air into the smoke removal tube 24 through a valve 26. The air cylinder 27 is a tube driving device that moves the smoke removal tube 24 to a position in the path of the measurement light a and a position outside the path.

In the same figure, when setting the absolute value (100%), the smoke removal tube 24 is moved to position A in the path of the measurement light a by the tube drive device @27 automatically in conjunction with the calibration command.
The valve 26 is opened and clean air is supplied from the air cylinder 25, and the inside of the smoke removal tube 24 is filled with clean air, and fl, l
After removing l, the control unit 19 automatically adjusts the coefficient J so that TL'=1.

Next, a specific measurement method will be explained.

A part of the light emitted from the light source 6 is transmitted to the rotating sector 2 of the chopper means 15 via the projection lens 17 as measurement light a.
The measurement light a that is focused on the first hole 21 of the 0 and is reflected by the mirrors 2a and 2b of the 0 reflection unit 2, which becomes an intermittent beam and is projected onto the reflection unit 2 via the first objective lens 5, is a half mirror. 8
and enters the photoelectric conversion unit 12 via the second objective lens 9 etc., and enters the preamplifier circuit unit 13 as an electric signal (voltage value).
The signal is input to the control unit 19 through the.

On the other hand, the calibration light is made into intermittent light by the plum chopper device 15,
After passing through the first objective lens 5, it passes through the prism 14 and the half mirror 8, and is converted into an electrical signal by the photoelectric converter I2 in the same way as the measurement light a.Then, the signal is input to the controller 19, where it is The light transmittance or the number of light absorbers is calculated based on Equation 0 and output to a predetermined location.

Further, the control section 19 continuously compares and calculates the measured values of the two bundles of measuring section a and the calibration light beam, and does not require a calibration function at regular intervals.

In the above embodiment, the calibration light is made to enter the half mirror 8 from the light source 6 after the first objective lens 5 and directly through the prism 14. As in the second embodiment, an optical fiber cable 29 as a light guiding means is provided after the first objective lens 5, and collimators 28 and 30 are provided at both ends to make the light parallel. Alternatively, the calibration light may be received and made to enter the photoelectric conversion section 12 via the half mirror 8.

FIG. 7 shows a third embodiment of the light emitting/receiving section 1, in which a light switching means 31 is provided after the first objective lens 5, and a light switching means 31 shown in FIG. Long holes 34, 35
It is also possible to use a device with a hole in it and rotate it with the electric motor 32 shown in FIG. 7 to emit one calibration light, and then switch the measurement light a.

In addition, in FIGS. 6 and 7, members corresponding to those explained in FIG. 1 are designated by the same reference numerals.

(Effects of the Invention) According to the present invention, it is possible to provide a smoke transmittance measuring device that exhibits the following effects.

■ Measurement is performed by continuously comparing the measured values of two luminous fluxes, so
Unlike conventional calibration at regular intervals, measurement accuracy can be improved.

(2) When setting the insulation value (100%) of light transmittance, the measurement is performed by replacing the air with clean air, so unlike conventional visual inspection, errors can be almost eliminated.

■ Since the light emitting/receiving section and the reflecting section are provided integrally, on-site adjustments such as optical axis alignment can be easily performed.

■ When calculating the light transmittance and extinction coefficient, noise in the measured values can be reduced by subtracting the value when the measuring light at 0% calibration is cut off from each measured value of the measuring light and calibration light. , drift etc. can be removed, so 31
It is possible to improve g-determination accuracy.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a first embodiment of the smoke transmittance measuring device according to the present invention, Fig. 2 is a front view of the chopper means, and Fig. 3 (
a) is a front view of the first embodiment of the optical switching means, FIG. 3(b)
1 is a side view of the first embodiment of the light switching means, FIG. 4 is a waveform diagram of the electric signal from the preamplifier circuit section, FIG. 5 is a configuration diagram of the fog removal means, and FIG. 6 is a second embodiment of the light emitting/receiving section. Example configuration diagram,
FIG. 7 is a configuration diagram of a third embodiment of the light emitting/receiving section, and FIG. 8 is a front view of another embodiment of the light switching means. DESCRIPTION OF SYMBOLS 1...Light projection/reception part, 2...Reflection part, 3...Soot dust, 4...Casing, 5...First objective lens, 6...Light source, 7...Projection lens, 8
...Half mirror 9...Second objective lens, 10...
・Aperture for limited field of view 11...Diffusion plate, 12・
... Photoelectric conversion section, 13... Preamplifier circuit section, 14°29... Light guiding means, 15... Chopper means. 16... Electric motor for chopper, 17.31... Optical switching means, 18.33... Electric motor for optical switching, 19.
...Control unit, 20... Rotating sector, 21... Hole, 2
2... Rotating plate, 23° 34, 35... Long hole, 24.
...Fume removal tube, 25...Air cylinder, 26...Valve, 27...Tube drive device, 28.30...Collimator, 33...Rotating plate, a...Measuring light, b
...Calibration light.

Claims (2)

[Claims] (1) A light emitting/receiving part and a reflecting part are arranged to face each other, and the light transmitted from the light emitting/receiving part causes the light transmittance or light absorption of a layer of smoke particles floating between the light emitting/receiving part and the reflecting part. In a smoke transmittance measuring device for measuring a coefficient, a light source is provided on a light projecting/receiving section side provided integrally with the reflecting section, and a projection lens and an objective lens for projecting measurement light from the light source onto the reflecting section. and a photoelectric conversion unit that converts the measurement light reflected by the reflection unit into an electrical signal by entering it through a half mirror;
a light guide means for introducing the calibration light from the light source into the photoelectric conversion unit via the half mirror; and a chopper means disposed midway between the projection lens and the objective lens for making the measurement light and the calibration light into intermittent light. and a light switching means for alternately switching between the calibration light and the measurement light introduced into the photoelectric conversion unit via the half mirror, and further inputting the electric signal from the photoelectric conversion unit and adjusting the light transmittance. and a control unit that calculates an extinction coefficient, and a smoke removal unit that replaces the space between the light emitting/receiving unit and the reflecting unit with clean air in order to set an absolute value. Transmittance measuring device. (2) The light switching means is a rotating plate, and this rotating plate is the first
The smoke transmittance measuring device according to claim 1, characterized in that it is provided midway between the objective lens and the light guiding means.