RU2356031C2 - Device and method to measure light transmission in atmosphere and to determine meteorological range of visibility - Google Patents

Abstract

FIELD: physics, measurements.

SUBSTANCE: invention relates to measuring light transmission in atmosphere and determining meteorological range of visibility and can be used at runways. The proposed device comprises the radiator and radiation receiver systems arranged at post structure made up of pipes, composed of the inner load-bearing pipe and outer pipe protecting the former, and mechanically isolated from it. Aforesaid inner pipe supports all measuring hardware components designed to center optically the radiator and receiver systems, the outer pipe accommodating all structural elements that can vary their spatial position due to gravity, wind force or directional sun radiation to keep optical alignment unhampered. The atmosphere dissipation factor metre makes an integral part of the device measuring the light transmission and is directly coupled with the outer pipe. Protective glass plates, V-shaped and arranged at 90° relative to each other, are mounted ahead of aforesaid radiator and receiver systems to protect electronic and optical components against dirt. Every V-shaped system of protective glasses incorporates a light transmission device to determine the degree of their contamination. The radiator and receiver systems are furnished with universal joint-type drive.

EFFECT: ease of operation.

13 cl, 7 dwg

Description

The invention relates to a device and method for measuring transmittance (light) in the atmosphere and determining the meteorological visibility range, moreover, this device and method is used, in particular, on runways.

The device of the light emitter and the device of the light emission of the visibilimeters using the measurement of light transmission in the atmosphere are installed opposite each other at a hard distance, the so-called length of the measuring base. Based on the range of measurements of the visibility range required for air traffic, typical standard values of measuring bases of 50 m or more are obtained, for the possibility of converting the transmission measurement results to the corresponding visibility ranges within the permissible errors.

Embodiments are known in which a combined light emitter / light emitter system is combined with a mirror system along the length of the base. In this case, the light from the emitter passes the area twice.

In any case, both of these parts of the device are mounted on an appropriate stand to ensure a nominal measurement height of 2.5 m above the surface of the runway. For reasons of stability needed to center the optics, these stand designs are usually fixed to a massive concrete foundation.

In order to achieve the entire required measuring range for the highest category of flight mode (CAT IIIb), two different lengths of measuring bases are usually combined with each other. An additional, so-called short base (measuring base length 10-15 m) provides measurement values for the region of very small visibility ranges (<100 m), which can no longer be generated within the permissible errors for standard values of measuring bases. Typically, a light emitter is combined with two light emitters, systems with light emitters / light receivers and two mirror systems are also known.

Further, the so-called visibilimeters are known that use transmission measurements in the atmosphere with measuring base lengths of up to 300 m, which are used for a range of visibility ranges of up to 10 km.

To exclude the effects of environmental light radiation, the light emitter is modulated in intensity, the light radiation detector preferably responds to incident light with known modulation. This modulation can be provided periodically or in the form of pulses. As light sources, preferably known are mechanically modulated or modulated at a very low frequency halogen sources that are in pulsed mode at a low frequency of xenon flash lamps, as well as diodes emitting infrared light, and laser sources.

From the measurement result of atmospheric transmission, based on the threshold of contrast sensitivity, the meteorological visibility range MOR (Meteorological Optical Range) is calculated as follows:

MOR (m) = (lnKB) / ln T,

Where

K = 0.05 (5% threshold for contrast sensitivity),

B is the length of the measuring base in meters and

T is the normalized transmission in the atmosphere.

Since the installation, start-up, and operation of the visibilimeter contain numerous problematic and difficult to learn individual aspects, as well as the measurement accuracy of the visibilimeters is undesirably affected due to various environmental influences, various measures are known to simplify installation and / or start-up, as well as reduce unwanted environmental influences on the visibilimeter.

Since light emitters and light emitters are mounted on separate concrete foundations, precision centering of the optics is first inevitable. In this case, individual deviations in the installation and execution are compensated by centering. In fact, massive concrete foundations do not guarantee that their position relative to each other always remains exactly unchanged. Each displacement of the concrete foundations leads, however, to a violation of the alignment of the optics, which can often be observed in practice, and thus forcibly leads to measurement errors of the visibility range identical to those that arise due to contamination of the outer surfaces of optical devices. Therefore, centering should be checked regularly and adjusted if necessary. At the same time, optical aids are introduced, which are introduced into the beam to check the quality of centering. To do this, it is usually necessary to interrupt the measurement. In any case, exposure to the light emitter and the light radiation receiver at the installation site is required, they are associated with a loss of time and, in case, violate the flight mode. Another source of errors is the surface contamination of optical devices, which are detected, and then this pollution should be compensated or eliminated by appropriate measures. The outer surfaces of the optical devices are subject to continuous contamination, which even with a slight occurrence reduces the transmission of hardware glasses and leads to significant measurement errors of the visibility range, especially at the upper end of the measurement region. In addition to the regularly necessary and usually often carried out cleaning of hardware glasses, various structural measures are known to reduce this pollution and the significant maintenance costs associated with it. For example, shields can be used that only occasionally release the outer surfaces of the optical devices during the measurement. This method has the disadvantage associated with constantly moving parts in the outer area, with the danger of a complete loss of functioning in the event of a shield defect, and with a small measurement sequence if the technique should achieve a noticeable reduction in pollution. Such embodiments are no longer of nominally significant practical use. US patent 4432649 describes a similar mechanism for elements mounted with the possibility of rotation in the course of the rays. Caps protecting from atmospheric agents belong to standard execution, and they can be found in practically any design. The protective effect of these caps, in essence, depends on their length in front of the outer surfaces of the optics. The length of the hoods for protection against atmospheric agents, of course, is limited by the required field of view for optical systems and the increasing size of the surface exposed to wind.

With caps for protection against atmospheric agents, only the large pollution effects associated with precipitation can be reduced. A continuous increase in pollution, which is dust and fine particles, cannot be significantly affected. Blowers that create airflow on or in front of the appliance glasses find practical application in some embodiments. They have the advantage that they can also partially keep dust and fine particles at a distance from the outer surfaces of the optics. Of course, also in this case, a constant increase in pollution cannot be avoided. Due to the turbulence of the air flow, constantly some part of the particles of contaminants gets on the hardware glass and negatively affects the measurement efficiency of the visibilimeter equipped in this way. From the application EP 1300671, a device is known in which, if necessary, a correspondingly clean segment of a hardware glass made in the form of a circle can be introduced into the optical path of the rays of the light emitter and the light emission receiver by rotating this glass. This event is suitable to extend the time interval between cleanings in accordance with the number of segments available. Although also protecting the clean segments from contamination and the presence in the outer area of frequently driven parts is not a problem. In each of the known embodiments, sooner or later, cleaning the hardware glasses is the only reliable means to eliminate the effect of contamination. However, the complete prevention of pollution is not possible. Along with the above possibilities of preventing or reducing pollution, various methods and devices are known that determine the degree of contamination of the outer surfaces of the optics of optical measuring devices in outdoor applications. From US Pat. No. 4,432,649, a method and apparatus are known in which the change in the total internal reflection of a hardware glass due to contamination particles is evaluated. At an angle of total internal reflection at the edge of the glass, light is supplied using a separate light emitter. The luminous flux penetrates through the entire glass along a typical zigzag path between the two inner boundary surfaces of the glass. If there are particles of dirt on the surfaces, then part of the light is screened out of the glass. On the edge of the glass opposite the feed, there is a corresponding light emitting detector that detects the residual luminous flux. By the loss of the light signal after passing through the glass, we can draw a conclusion about the degree of its pollution.

From the patent specification EP 1300671, a method and a device are known in which, if necessary, a clean segment of a hardware glass made in the shape of a circle can be introduced into the optical path between the light emitter and the light emitting receiver by rotating this glass. By comparing the measured values with a contaminated and temporarily introduced clean glass segment, a conclusion can be drawn about the degree of contamination present. The disadvantage of this method is, accordingly, the necessary violation of the transmission measurements in order to determine the degree of contamination and the mechanical elements of the device that are often shifted in accordance with the need.

EP 0745838 discloses a method and apparatus which, for a transmission measuring device, comprises equipping two light emitters / light detectors with angularly mounted hardware glasses, determines the transmission of these hardware glasses with separate emitter glass and receiver glass systems and associates with both of them measurement results to obtain the transmittance in the atmosphere.

The described method requires two systems of devices, both of which require both a light emitter and a light radiation receiver for measuring transmission in the atmosphere along two separate paths using various hardware glasses.

Visibilimeters that use the measurement of light transmission in the atmosphere, however, after installation and centering, need to adjust their measured transmission (light) value in the atmosphere and the value of the visual range obtained from these measurements to the real conditions of visibility at the installation site. This fitting process is commonly called calibration. With particular regard to the fact that the visibilimeter in the finally calibrated operating state at infinitely high visibility range must reach 100% transmittance, calibration is usually carried out under very high visibility conditions> 10 km in order to at least approximately achieve the required calibration conditions , since a situation with an approximately infinitely high range of visibility can usually be found too rarely.

Thus, nevertheless, the range of visibility that is currently taking place is evaluated by trained observation personnel, and for this visibilimeter, the measured transmittance is set according to the length of the measuring base.

This adjustment is often done only manually as an electronic “sensitivity setting” on the receiver or by adjusting the light intensity.

In the process of electronic data processing, purely computational methods of calibration have also become possible. An additional calibration factor is supplied to the measured value issued by the visibilimeter, which is oriented to the visibility range obtained by the observer, and after entering the visibility range from the observer into the keyboard, it is automatically calculated using the data processing device.

The basis of the invention is the task of providing a device and method by which you can eliminate the disadvantages of devices known from the prior art.

According to the invention, a device for measuring atmospheric transmittance and determining the meteorological visibility range using a radiation system and a radiation receiving system fixed to a pipe structure made of pipes is solved due to the fact that the structure of a pipe made of pipes consists of a supporting inner pipe and is mechanically fully with it a disconnected outer pipe protecting the inner pipe, and on the inner pipe all the devices necessary for measuring are installed, which, in particular, provide they center the optics of the radiation and reception systems, and all the structural elements are installed on the outer tube which, due to their own weight, wind load or one-sided solar radiation, can change their position, so that the centering of the optics is not affected by these effects, and the device for measuring the atmospheric scattering coefficient is an integral component of the transmission measurement system and consists in direct connection with the outer pipe, while in front of transmitting and receiving devices are equipped with hardware glasses in the form of V at an angle of 90 ° relative to each other to protect optical and electronic components from contamination, while each of the installed in the form of V hardware glasses has a transmission measuring device for measuring transparency, which determines the degree of contamination of the hardware glass, while the optical system of the emitter, the optical system of the receiver are arranged to move by means of a gimbal device. Preferably, the emitting device and the receiving device are equipped with a purge air system in such a way that the path of the precipitation particles directed against the apparatus glasses deflects toward the ground before they enter them so that these particles of precipitation, such as raindrops or snow flakes cannot reach the outer surfaces of the optics. Moreover, since the device for measuring the atmospheric dispersion coefficient registers precipitation, this information can be used to start the air purge system. Thus, continuous operation is excluded, in the presence of precipitation, the possible deposition of contaminants on the glass of the devices is prevented. The device for measuring the coefficient of dispersion of the atmosphere is preferably made in the form of a device for measuring the coefficient of dispersion of the atmosphere with forward dispersion. Particularly preferred is the use of a white light emitting diode as a radiation source. Further preferred is if the receiver uses synchronous demodulation and is tightly synchronized with the modulating frequency of the emitter.

According to an aspect of the invention, there is provided a method for measuring atmospheric transmittance and determining meteorological visibility range due to the fact that a calibration coefficient is determined in automatically selected situations, the calibration coefficient being obtained by forming the ratio of the visibility range generated by the device for measuring atmospheric dispersion coefficient, which has been converted to equivalent transmittance, and the measured transmittance in the atmosphere, which is between by automatically selected contamination factors, the correction factor is determined by constantly measuring the transparency of the hardware glasses that are in front of the emitter and receiver, which, knowing the correction factor and calibration coefficient obtained, determine the centering coefficient, which is equivalent to what has changed optical centering between the emitter and the receiver, which is the measured transmittance in the atmosphere, floor data from the transmittance measuring device is corrected by a calibration coefficient and a correction factor, while the obtained centering coefficient is used to again create the initial alignment position between the receiver and the emitter.

The present invention is made with the possibility of eliminating all known harmful effects from practice, and on the other hand, with the ability to take into account in detail and, if necessary, compensate for these harmful effects.

Thanks to this, a transmission measurement system is obtained to determine the meteorological visibility range at aerodromes, which requires almost no maintenance.

The invention is further explained in more detail based on embodiments with reference to the accompanying drawings, in which:

Figure 1 is a table of the image of the relative measurement error of the visibility range for the adopted coefficient of contamination of the glass 1%.

Figure 2 represents the main elements of the device according to the invention.

Figure 3 is a graph illustrating the measurement error of the visibility range due to an error in reading traditionally, in comparison with the device according to the invention.

Figure 4 represents the main structure of the construction of the rack, made of pipes, with fixed main structural units mounted on it.

5 represents the design of a radiation system.

6 represents the design of a purge air system.

7 is a view of a device for measuring the transparency of hardware glasses.

Following the basic principle of visibilimeters using the measurement of light transmission in the atmosphere, as can be seen from figure 2, the emitter system 3 and the receiver system 4, mounted on a rack structure 1 made of pipes, and protected by a cap 2 for protection against atmospheric agents, are located opposite each other. In this case, the distance, the so-called length of the measuring base, between both systems is 30 m, and other standard lengths of the measuring bases of 50 m and 75 m can also be implemented.

To achieve the required measurement height of 2.5 m, the emitter system 3 and the receiver system 4 are mounted on a rack structure 1 made of pipes. It provides particularly high stability, in particular with regard to possible warping due to unilateral solar radiation and wind loads.

The implementation of the design 1 of the rack of pipes provides a double structure of pipes, and the only mechanical contact between the inner and outer pipes 5, 6 is made in the area of the base plate.

This new embodiment of the invention allows the complete mechanical separation of the optoelectronic systems relevant for measurement from other parts of the structure. The optoelectronic systems are supported by a mechanically separated inner pipe 5. The outer pipe 6 serves to protect the inner pipe 5 and carries all heavy or especially environmentally sensitive components, in particular, the supporting structure 7 with a mounting yoke, blower 8 and cap 2 for protection against atmospheric agents (see figure 4).

The cap 2 for protection against atmospheric agents in the aforementioned new embodiment can be made particularly long and, thus, particularly effective, therefore, the resulting wind load due to the construction of the rack 1 made of pipes does not affect the optical centering of the optoelectronic system. Due to the open design of the cap 2 for protection against atmospheric agents, despite this hardware glass 9 remains easily accessible for maintenance personnel when cleaning them.

The optoelectronic system on the inner tube 5 and the supporting structure 7 on the outer tube can be rotated around the pipe axes for rough centering vertically, and are also equipped with set screws for fixing in the final position.

The sighting device on the supporting structure 7 is used as an aid to the rough centering process, then the rough centering is further supported by acoustics. Powerful signaling devices in the optoelectronic systems of the emitter and receiver with an increased signal cycle allow you to find out when the light signal of the emitter, sufficient for fine centering, reaches the optics of the light emission receiver system.

The implementation of the optical systems 10 inside the optoelectronic system of the emitter and receiver allows for automatic thin centering of the emitter and receiver. The optical systems 10 in the area of the lenses are mounted using a cardan suspension 17. Drive motors 11 with eccentric elements 12 in the region of the focal length of the optical systems 10 provide an extremely accurate and gap-free electromechanical alignment of the optical axes. Using the appropriate control elements, it is possible to control the drive motors 11 using a microprocessor. The position of the eccentric elements 12 and thereby the optical axes is determined using potentiometers 13 separately for adjusting horizontally and vertically and after analog-to-digital conversion is recorded by the microprocessor of the control system (figure 5).

In the process of automatic fine centering, the optics of the emitter and receiver move sequentially both vertically and horizontally. During the movement process, both the mechanical position of the optical systems and the corresponding reception signal are continuously and simultaneously recorded. Due to the systematic course of the tuning process, it becomes possible to determine both the intensity profile of the emitter and the distribution of receiver sensitivities.

After receiving individual profiles, the resulting optimal horizontal and vertical central positions of the optical axes, both for the emitter and for the receiver, are set automatically. For this optimal centering of the optical systems, the corresponding positions of the eccentric elements 12 are stored in the control system at zero voltage and are thus available at any time if necessary.

To protect the optoelectronic elements of the transmission measuring device, transparent hardware glasses are provided for both the emitter and the receiver, which do not limit the optical path of the rays. In this embodiment, the new air purge system prevents wetting of the outer optical surfaces, for example, by sediment particles driven by the wind, which are not reflected by cap 2 for protection against atmospheric agents. In order to counteract the constant recirculation of dust and fine particles of contaminants by the purge air system and the danger of deposits of such particles on the hardware glasses, the blower of the purge air system comes into effect only with actual precipitation. Information about precipitation, as follows from figure 2, is created using a device for measuring the coefficient of dispersion of the atmosphere on the supporting structure 7 of the emitting system, which is configured to ascertain the necessary weather conditions at the moment.

The injection flow of the purge air system has such channels that an air flow directed towards the ground arises in the area in front of the hardware glasses. Particles of precipitation, before reaching the hardware glass, are guaranteed to deviate downward, and the air flow reinforces and accelerates the movement of particles towards the ground.

The air channel 14 of the purge air system is a structural component of the design of the cover of the optoelectronic system. It is completely mechanically disconnected from the blower. Thus, the resulting vibration from the blower 8 cannot have any effect on the measurement system and in particular does not affect the centering of the optical axes (Fig.6).

The integral component of the device according to the invention is a device for measuring the atmospheric dispersion coefficient, with which you can carry out ongoing quality control of the calibration of the transmission measurement.

The system of the emitter and receiver 3, 4 have a mounting yoke, which is part of the supporting structure 7 mounted on the outer protective tube for blower 8 and cap 2 for protection against atmospheric agents. A device 15 for measuring the atmospheric dispersion coefficient is mounted on this yoke, which can, therefore, carry out the comparative measurements necessary for this method in the immediate spatial proximity of the transmission measurement site. Since weather phenomena that limit the range of visibility, as a rule, have an inhomogeneous distribution in space, one should prefer this immediate proximity of the measuring complex, consisting of a visibilimeter and a device for measuring the atmospheric dispersion coefficient, to other locations. The operating procedure and the underlying method of operation of the device used to measure the scattering coefficient of the atmosphere is known from the prior art. Due to the more reliable measurement efficiency, a measurement system in accordance with the optical method for measuring forward scattering coefficient is preferable compared to the method for measuring backscatter. In addition, the used device for measuring forward forward scattering provides the determination of the current weather and generates information about precipitation situations, both for controlling the air purge system and for the calibration coefficient determination described in this connection.

Direct scattering measurement systems are much less prone to measurement errors due to pollution, which is explained by the principle of their design, and, in addition, they are able to reliably determine very large visibility ranges from 10 km or more, which is only possible with transmission measurement systems with very long measuring bases (with the disadvantage associated with the absent but certainly required range of visibility range below 200 m) with, of course, still increased the occurrence of measurement errors due to pollution.

The sources of errors in devices for measuring the atmospheric dispersion coefficient are mainly based on a relatively small and thus not always equivalent volume of air, typically <1 L, which is used to determine the range of visibility, as well as on the problems of non-equivalent measurement of apparent increase in cloudiness for various precipitation phenomena, which makes it preferable to use selective visibilimeters for the measurement range of visibility below about 3 km, which is of importance the reliability on the ground.

In this embodiment of the invention, then also the measured values of the visibility range obtained using the device for measuring the scattering coefficient of the atmosphere are preferably used for comparison with the results of measurements of transmittance (light) if

- the measured value of the visibility range obtained using the device for measuring the scattering coefficient of the atmosphere exceeds 10 km;

- the change in the measured value of the visibility range obtained using the device for measuring the scattering coefficient of the atmosphere relative to the average value in the considered period of time, in no way exceeded +/- 10%;

- no precipitation was detected by a device for measuring the atmospheric dispersion coefficient;

- there are no violations in the operation of the device for measuring the coefficient of dispersion of the atmosphere;

- the change in the measured transmittance relative to the average value in the considered period of time in no way exceeded +/- 1%;

- there are no violations in the operation of the device for measuring transmittance (light).

Knowing the set length of the measuring base for transmittance measurement in this selected situation, the measured value of the visibility range obtained using the device for measuring the atmospheric dispersion coefficient is converted to the equivalent transmittance value, and it is compared with the measured value obtained using the device for measuring transmittance, and for both values the coefficient is calculated. In this case, the average value of all the individual readings depending on the modulating frequency in the corresponding measuring unit of the transmittance measuring device and the device for measuring the atmospheric dispersion coefficient over the past minute is preferably used as the measured value, and the information obtained from this is used to determine the transmittance in the atmosphere and / or visibility range. From the calculated coefficients, the calibration factor KF is then derived for the measured transmittance.

The calibration factor is now used during subsequent measurements, and in particular during a visible increase in cloud cover below 10 km. It retains its effectiveness until a new calibration factor is determined using the described method.

The described computing operations are carried out using a microprocessor in the control system of the visibilimeter, the change in the calibration coefficient is subject to limitation by the maximum step size, which counteracts the manifestation of errors due to temporary violations. The corresponding calibration factor is stored by the control system with guaranteed zero voltage.

Due to the use of the measured value obtained using the device for measuring the atmospheric dispersion coefficient in order to determine the calibration coefficient only in the region above the upper limit of the measurement range of the visibilimeter and the fact that the measurement error of the visibilimeters, which occurs due to environmental influences, with a decrease in visibility ranges decreases, for the visibility range used by the visibilimeter, the optimum measurement accuracy is constantly achieved th.

The method just described has the same sequence of actions as when calibrating a visibilimeter by a trained observer, with the difference that every possible calibration situation at any time of the day or night is used to optimize the effectiveness of the visibilimeter measurements. As a result, this leads to a large number of effective calibration cases, which in no way can be achieved using known calibration methods supported by observers. The automatic determination and application of the calibration coefficient for transmittance measurements allows both constant and complete compensation of the effects that limit the effectiveness of the visibilimeter measurements.

According to Fig.7, you can see two hardware glass 9 located in the form of V at an angle of 90 ° relative to each other. With their help, it becomes possible to thread the same glass along two axes. The main axis represents the direction of the rays for measuring transmission (light) in the atmosphere, the lateral axis offset by 90 ° describes the rays for the separate measurement of the transparency of hardware glasses. Both optical axes penetrate one instrument glass, each at an angle of 45 ° to the surface of the glass and in the same region of the glass, while the other glass is pierced only by the path of the rays following respectively the side axis.

This arrangement makes it possible to continuously measure the true transparency of the glasses and allows accurate compensation of the effects that may limit the effectiveness of pollution measurements. To determine the contamination of the glasses, it is not necessary to interrupt the measurement in order to make comparison with a clear comparison glass possible, or to apply empirical transformed values derived from the glass scattering properties.

Based on the use of elongated hoods 2 for protection against atmospheric agents, it can be assumed that both glasses are dirty evenly. Thus, the correction of the atmospheric transmittance measurement based on the described transparency measurement is also acceptable if only one instrument glass 9 respectively affects the transmittance measurement in the atmosphere.

Further, the device according to the invention does not use any separate receiver system 16 for measuring the transparency of glasses, it is an integral component of the control electronic device. Using the correspondingly formed part of the body of the optoelectronic system, the beam of rays after the intersection of the hardware glasses is deflected in the direction of the optical receiving device of the control system (see Fig. 7).

From the result of measuring the transmission of glass, the microprocessor of the control system determines the correction factor due to pollution for measuring transmission. It is determined separately for the emitter system and for the radiation receiver system (3, 4).

In this case, the ratios are:

VS = 1 / (TPS) · 0.5,

VE = 1 / (TPE) · 0.5,

in which:

VS — contamination correction factor for the emitter;

VE is the pollution-related correction factor for the receiver;

TPS is the normalized result of measuring the transparency of the glasses of the optoelectronic system of the emitter;

TPE is the normalized measurement result of the transparency of the receiver glass.

Both pollution-related correction factors can be combined into a common pollution factor VG:

VG = VSVE.

With clean hardware glasses, VG becomes = 1.

Using the same mechanism, the coefficient VG _{temp is} calculated, which, however, unlike VG, is again normalized to 1 with each determination of the new calibration coefficient. This temporary correction factor due to pollution is taken into account in this case, along with the calibration coefficient, as applied to the measurement result transmittance.

TM _corr = TMmess · VG _temp · KF,

Where

TM _Corr - corrected measurement of transmission in the atmosphere;

TMmess - uncorrected transmission measurement result in the atmosphere;

VG _temp - temporary correction factor due to pollution;

KF is the calibration factor.

Thus, the effects of glass contamination on transmittance measurements between situations in which a new calibration factor is determined are compensated by transmittance measurements. Each newly obtained calibration factor automatically also compensates for the effect represented by VG due to contamination of the glasses.

A clear knowledge of the contamination coefficient of optical external surfaces on the basis of the measurement of the transmittance of the hardware glasses located in the V shape already described, together with the knowledge of the calibration coefficient described above, now allows for the first time to separate transmission errors due to centering and pollution, and thereby also errors in the measurement of visibility ranges.

Since the calibration factor consists of a correction factor due to centering and a correction factor due to contamination for the measured transmittance, but there is still separate information about the correction factor due to contamination, the component of the calibration coefficient due to centering can be calculated directly.

KA = KF / VG,

Where

KA is the proportion of the calibration coefficient due to centering;

KF is the calibration factor;

VG is the overall pollution factor.

Knowing the KA and VG - coefficients according to the invention, we can conclude on the quality of centering and the degree of contamination of the hardware glasses. Using VG _temp, it is possible to obtain, by calculation, compensation for glass contamination that has arisen also for the time interval between situations in which a new calibration coefficient KF can be determined on the basis of the fulfilled conditions for using the measured value obtained by the device for measuring the atmospheric dispersion coefficient. With each new calculation of the calibration factor, the centering quality is again determined. The user can thus obtain information on both the degree of contamination of the hardware glasses and the quality of centering.

With the introduction of appropriate limit values specific for an embodiment of the invention for KA and VG, it is clearly determined when the hardware glasses should be cleaned and whether a new alignment of the optical axes of the emitter and / or radiation receiver is required. In this case, a new centering can either be initiated by the user, or completely automatically. A fully automatic new centering is preferably carried out if:

- the measured value of the visibility range obtained by the device for measuring the scattering coefficient of the atmosphere exceeds 10 km;

- the change in the measured value of the visibility range obtained by the device for measuring the scattering coefficient of the atmosphere, in relation to the average value in the observed period of time in no way exceeded +/- 10%;

- no precipitation was detected by the device for measuring the atmospheric dispersion coefficient;

- there is no violation in the operation of the device for measuring the coefficient of dispersion of the atmosphere;

- the change in the measured transmittance in relation to the average value during the period of consideration in no way exceeded +/- 1%;

- there is no violation of the device for measuring transmission.

The determination of the calibration coefficient KF according to the invention, as well as the temporary correction factor VG _temp due to contamination at any time, ensures optimal transmission measurements and ultimately unattainable accuracy of meteorological range measurements, with virtually no maintenance required.

The constant synchronization of the light receiver with the modulation frequency of the light emitter makes it possible for the synchronous demodulation of the received light modulated in intensity of the light signal, known in the prior art, with known improvements in measurement properties for small noise signals. After analog-to-digital conversion with more than a million increments in accordance with a resolution above 0.0001%, the received light signal in the form of numbers is sent to the microprocessor of the control electronic device for further processing (see figure 3).

A white light emitting diode is used as a radiation source, the service life of which reaches more than 5000 hours due to the reduced operating current, which is much lower than the permissible maximum current. A light emitting diode is periodically modulated in intensity with a so-called modulation frequency. The modulation frequency is usually more than 1000 Hz, for the formation of a large number of readings, which favors the stability of the measurement.

The light emission intensity is modulated with a duty cycle of 50% between zero and the set operating current. The average value of the operating current is only a few milliamps. The intensity of the light source is maintained with high stability using an electronic precision control loop.

The spectrum of white-light-emitting white light emitting diodes used in comparison with monochromatic light sources, such as color or infrared light-emitting diodes or also laser light sources, has the advantage of fully representing the wavelength range recommended by the international aviation organization ICAO for light sources in visibilimeters to measure the visibility range. Compared with mechanically modulated halogen light sources or also with pulsed mode at low frequencies, xenon flash lamps, which usually have a recommended spectral range, there is an advantage in realizing significantly higher modulation frequencies and, consequently, more frequent contributions to the results measurements in the formation of an average value.

Notation list

1 - rack design made of pipes

2 - a cap for protection against atmospheric agents

3 - emitter system

4 - receiver system of the emitted light

5 - an internal pipe

6 - an external pipe

7 - supporting structure

8 - blower

9 - hardware glasses

10 - optical system

11 - drive motor

12 - eccentric element

13 - potentiometer

15 - air channel

16 - device for measuring the coefficient of dispersion of the atmosphere

17 - receiver system for measuring the transparency of glasses

18 - cardan suspension

Claims (13)

1. A device for measuring light transmission in the atmosphere and determining the meteorological range of visibility, comprising a system of an emitter and a receiver system of the emitted light, which are respectively mounted on a rack structure made of pipes, characterized in that
the rack construction made of pipes consists of a supporting inner pipe and an outer pipe mechanically completely disconnected from it, protecting the inner pipe, and on the inner pipe all the systems necessary for measurements are installed, which, in particular, provide optical centering of the transmitter and receiver systems, when this on the outer tube installed all the structural elements that can change their position due to their weight, wind load or unilateral solar radiation so that the opt cal centering remained unaffected by these effects,
a device for measuring the coefficient of dispersion of the atmosphere is an integral component of a device for measuring transmission and is directly connected to the outer pipe;
respectively, in front of the emitter and receiver systems for protecting the optical and electronic components from pollution, hardware glasses in the shape of V are installed at an angle of 90 ° relative to each other;
each of the installed in the form of V hardware glasses corresponds to a device for measuring transmission for measuring transparency, which determines the degree of contamination of the hardware glasses, and
both the optical system of the emitter and the optical system of the receiving device are mounted for movement by means of a gimbal device. 2. The device according to claim 1, characterized in that the emitter system and the receiver system are respectively equipped with a purge air system that deflects the precipitation particles towards the ground before they hit the instrument glass, so that these particles do not reach the optical outer surfaces. 3. The device according to claim 1 or 2, characterized in that the device for measuring the scattering coefficient of the atmosphere is a device for measuring direct scattering. 4. The device according to claim 1, characterized in that the receiver system uses synchronous demodulation and is tightly synchronized with the modulation frequency of the emitter system. 5. The device according to claim 1, characterized in that the emitted light source is a white light emitting diode. 6. The device according to claim 1, characterized in that the signal identifier is associated with a receiving device system. 7. The device according to claim 6, characterized in that the signal identifier is an acoustic signal sensor. 8. A method of measuring light transmission in the atmosphere and determining the meteorological visibility range, characterized in that
in automatically selected situations, a calibration coefficient is determined, the calibration coefficient being obtained by generating a coefficient of the visibility range supplied by the device for measuring the atmospheric dispersion coefficient, which has been converted to the equivalent transmittance, and the measured transmittance in the atmosphere;
between the automatically selected situations, a correction factor due to contamination is determined, the correction coefficient being determined by continuously measuring the transparency of the hardware glasses that are in front of the emitter and receiver systems;
taking into account the obtained correction coefficient and the calibration coefficient, a centering coefficient is determined, which is equivalent to the fact that the optical centering between the transmitter and receiver systems has changed;
the measured transmittance in the atmosphere, which was determined by the device for measuring transmittance, is adjusted taking into account the calibration coefficient and the correction factor;
the obtained centering coefficient is used to re-create the initial alignment position between the receiver and radiator systems. 9. The method according to claim 8, characterized in that the automatically selected situation is determined by the fact that the evaluation of the measured values issued by the device for determining the atmospheric dispersion coefficient shows that there is no precipitation and a visibility range of more than 10 km. 10. The method according to claim 8, characterized in that
after installation and rough centering of the systems of the emitter and receiver, automatic thin centering is carried out, and at first the emitter system and then the receiver system are moved both vertically and horizontally;
accordingly, the occupied positions are stored with the reception values registered in this case;
The intensity profile of the emitter system recorded due to this and the sensitivity profile of the receiver system are used to establish the optimal position in the space between the emitter system and the receiver system. 11. The method according to claim 10, characterized in that the intensity profile and sensitivity profile are stored at zero voltage. 12. The method according to claim 8, characterized in that the measurement values provided by the device for measuring the atmospheric dispersion coefficient are used to bring the existing purge system with air into operation or turn it off. 13. The method according to claim 8, characterized in that the correction factor is subjected to verification of the threshold value and when the threshold value is exceeded, a signal is generated about cleaning the hardware glasses.

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