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    • 专利摘要:
    Method for correcting measurement errors caused by the intensity of precipitation in tipping cup rain gauges or any instrument for measuring fluids based on the tipping cup principle. The method reduces measurement errors due to the variation in the intensity of precipitation and characterizes the behavior of the mechanism in instruments for measuring fluids with tilting cups. Characterizing the addition of surpluses during the movement of the rocker, the fall time of the bowl, its variation with the intensity of precipitation and the decrease in the nominal tipping volume. Through the relationship between the increase in excess water and the reduction in the tipping volume, caused by the variation in the fall time of the rocker arm and the water thrust. This method is industrializable, reduces measurement errors, easy to implement, automatable and applicable to any tipping cup equipment. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2831899A1
    申请号:ES202030968
    申请日:2020-09-25
    公开日:2021-06-09
    发明作者:Cardozo Daniel Alberto Segovia；Sinobas Leonor Rodriguez
    申请人:Universidad Politecnica de Madrid；
    IPC主号:
    专利说明:

    [0002] METHOD FOR THE CORRECTION OF MEASUREMENT ERRORS CAUSED BY THE INTENSITY OF PRECIPITATION IN TILTING BOWL RAIN METERS OR ANY INSTRUMENT FOR FLUID MEASUREMENT BASED ON THE TILTING BOWL PRINCIPLE
    [0004] TECHNICAL SECTOR
    [0005] This method is related to the equipment manufacturing and monitoring sector, referring to climatic and environmental issues.
    [0007] BACKGROUND OF THE INVENTION
    [0008] The measurement of atmospheric precipitation has been and continues to be very important for humanity, mainly to understand and track the water cycle on the planet. Thus, one of its basic applications is related to the use of water resources, so that since ancient times there is evidence of the implementation of instruments for its measurement.
    [0010] Precipitation measurement is of interest in many fields, such as Agriculture, irrigation, climate change, geological hazard, hydrological monitoring, early warning and flood prevention, food security, environmental assessment and management, management of water resources, design of structures, airport management, calibration and implementation of multiple methods for the precise measurement of the amount of rainfall in different areas among others. Therefore, throughout history, different devices and techniques aimed at their measurement have emerged.
    [0012] Among the most modern, we can mention: the ultrasonic rain gauge, the float type rain gauge, the weighing rain gauge, the siphon rain recorder, the dendrometer, as well as radar and remote sensing technologies, among others. Among them, the tilting cup rain gauge stands out as one of the most widely used and widespread, mainly due to its ease of production, its low cost and its low energy consumption due to mechanical operation; that facilitate its automation and implementation in remote locations. Being one of the most used in the world by government agencies, airports, industries, universities and farmers, among others.
    [0013] However, despite the characteristics that have favored its expansion, they tend to present errors in the measurements that decrease their precision and reduce their advantages over other equipment. Among the errors it is worth highlighting: those caused by the evaporation of water in the mechanism, due to the frequency of data acquisition; the humans committed during assembly and maintenance; the so-called random ones, typical of the operating mechanism, influence of the wind. Many of these considered insignificant compared to those caused by the variation in the intensity of precipitation, which produce a variation in the volume of water of each tipping, compared to the generalized assumption that it would consider a constant nominal precipitation sheet in each tipping. This generates a trend that underestimates precipitation by increasing its intensity.
    [0015] Current calibration procedures refer to static calibrations and dynamic calibrations. The former are recommended by the manufacturers of the rain gauges and guarantee a predetermined tipping volume, but do not solve the problem of the effect of the variation in the intensity of precipitation. The second are usually carried out in the laboratory and consist of determining a regression between the rain gauge measurements and the actual rainfall applied, or with the measurements obtained by other more precise sensors (dysdrometers); Others use statistical procedures and experimental analyzes between some parameters such as the variation of the time between tilts and the estimation of the tilting volume. These methods require experimentation, most are unsuitable for automation, require external equipment, and take a long time to perform.
    [0017] Due to their characteristics and advantages, these rain gauges are of great interest from companies that manufacture climate and environmental instruments, as well as the research sector. In addition to a constant demand from users, to increase measurement precision.
    [0019] The methodology presented here is based on the characteristics of the equipment so it can be adapted to any cup rain gauge by modifying the initial parameters, the process can also be automated, implemented in a program or software, allows correction in real time and reduces time calibration.
    [0020] In addition, many of the required parameters are given by the manufacturer or can be easily measured.
    [0022] DESCRIPTION OF THE INVENTION
    [0023] The objective of the invention is to reduce the errors generated by the variation of the intensity of precipitation and increase the precision in the measurement of precipitation in tipping bowl rain gauges or any instrument for measuring fluids based on the tipping bowl principle. . The method consists of characterizing the behavior of the rain gauge mechanism and its interaction with the water collected by the funnel as a function of the intensity of precipitation based on its design characteristics such as: the collection area, the area of the outlet hole of the funnel, nominal tipping volume, droplet fall distance from the funnel, bowl fall distance during tilting, nominal blade and bowl dimensions. These characteristics condition the addition of excess water during the falling movement of the rocker (generating an increase in the tipping volume) and the decrease in the nominal tipping volume and the reduction of the tipping time, due to the kinetic energy of the water. that falls on the seesaw (either at rest or motion).
    [0025] The trend of increasing excess water with the intensity of precipitation, compared to the compensation generated by the decrease in the nominal tipping volume due to the action of the increase in the kinetic energy contributed by the falling fluid and the reduction in the fall time of the bowl, which in turn reduces the rate of increase of the excess water, allows the correction of the volume of water that generates a tilt and its consequent sheet of precipitation in relation to the intensity of precipitation.
    [0027] This method is applied to the reduction of errors in tipping cup rain gauges. A type of rain gauge widely used in the world due to its simplicity and low manufacturing cost, as well as having a low energy consumption. However, its reliability in the measurement of precipitation is lower than in other instruments, so a series of calibration methods have been developed to reduce these errors, however, these generally require a long and complex experimental procedure.
    [0028] In a bucket rain gauge, the precipitation is collected in liquid form by a funnel, and is related to the catchment area to obtain the volume of water collected as a function of the rain sheet. The water falls by gravity from the funnel, through a hole located in the lower part of the funnel, to the measuring mechanism (rocker), formed by two tilting cups. One of them receives the falling water and starts a process of collecting water until it reaches a volume that breaks the balance of the rocker and causes it to tilt. This bowl descends a distance of fall from its resting condition until it hits the calibration screws that stop the movement, where it discharges the stored water; With the same falling movement, the other bowl rises to place itself on the water fall line and start filling it to repeat the procedure.
    [0030] This cycle, powered by hydraulic power, repeats as long as there is precipitation. Each tilt is transmitted through an electrical pulse generated by a magnet anchored to the rocker that closes the circuit of a magnetic switch, to an information storage unit through a digital input; to be interpreted with a nominal tipping volume or precipitation sheet assigned to each tipping (generally static).
    [0032] During the descent of the bowl and even before its start, several simultaneous processes take place within the mechanism, which generate excess water greater than the nominal volume that initiates the fall, for example, during the tilting movement, water continues to fall from the funnel , part of this water falls into the bowl that is descending, adding water to the nominal volume that broke the equilibrium. In this way, contrary processes also occur, such as the kinetic energy contributed by the water that falls on the moving bowl, accelerating the fall and reducing the fall time of the rocker or the energy contributed to the balance of the static rocker, which reduces the necessary volume. for tipping; which causes a compensation for the increase in excess water. These are directly related to the increase in the intensity of precipitation, which makes it possible to correct the tilt value as a function of it and, therefore, the measured precipitation.
    [0034] The analysis of the behavior of the water within the mechanism of the rain gauge and its response to variations in precipitation intensity, together with the determination of the fall time of the bowl and its variation, allow to obtain a relationship between the fraction of excess water increase and the rate of reduction of the nominal volume due to the decrease in the fall time of the rocker arm and the increase in the pressure of the falling water funnel. All this makes it possible to know the variation of the tipping volume as a function of the intensity of precipitation and consequently apply a correction to the precipitation measurements and significantly reduce measurement errors.
    [0036] This calibration can be applied once the initial parameters that determine its behavior have been obtained / known. It can be integrated into a calculation routine, a program or software for automation and even implemented on the equipment itself to perform a correction in real time.
    [0038] BRIEF DESCRIPTION OF THE DRAWINGS
    [0039] In a complementary way to the description that is being made, in order to help a better understanding, a set of drawings is attached as part of said description in which, with an illustrative and non-limiting nature, the following has been represented:
    [0041] Figure 1 shows a simplified diagram of a tipping cup rain gauge with its main components, where:
    [0042] 1) Collecting funnel
    [0043] 2) Drain hole for the water collected by the funnel
    [0044] 3) Rocker, rocker mechanism.
    [0045] 4) Cups
    [0046] 5) Magnet
    [0047] 6) Normally open magnetic switch
    [0048] 7) Stop screws
    [0049] 8) Drainage grids for accumulated water in the bowls
    [0050] 9) Collecting surface or exposed surface
    [0051] 10) Spirit level
    [0053] Figure 2 schematically shows some of the characteristics of the rain gauge used in the invention, where:
    [0054] 11) Diameter of the collecting funnel
    [0055] 12) Diameter of the drain hole in the funnel
    [0056] 13) Distance between the funnel hole and the impact zone of the water falling into the bowl.
    [0057] 14) Minimum distance that a water particle must travel after leaving the funnel to be collected as a surplus by the moving cups.
    [0058] 15) Horizontal distance between the water fall line from the funnel and the central part of the rocker arm that divides both cups in a state of rest.
    [0059] 16) Representation of the volume of water necessary inside the bowl to cause it to tilt. Tipping volume.
    [0060] 17) Height of the cups.
    [0061] 18) Linear distance of fall of the cups.
    [0063] Figure 3 schematically shows the representation of some parameters used by the invention, where:
    [0064] RI) Precipitation intensity.
    [0065] tu) Time that the bowl will be under the line of fall of the drops, which goes from the beginning of the tilt until the line of fall of the drops is on the dividing line between the bowls.
    [0066] thc) Time it will take for a water particle to travel the distance between the base of the funnel hole and the minimum point necessary to be placed in the path of movement of the rocker and to be collected by it.
    [0067] td) Time required for a water particle to travel the distance between the base of the funnel orifice and the point of impact on the bowl.
    [0068] ts) Time that a water particle has to become surplus during tilting, resulting from the interaction between tu, thc and td.
    [0069] g) Representation of the gravitational attractive force.
    [0070] tt) Cup fall time.
    [0071] Dt) Relationship between a tilt and the precipitation sheet that it represents.
    [0073] Figure 4 shows the evolution of the precipitation sheet associated with each tilt as a function of the increase in the intensity of precipitation in two rain gauges with different cups, where:
    [0074] 19) Evolution in a first rain gauge, determined by means of a traditional dynamic laboratory calibration.
    [0075] 20) Evolution in a first rain gauge, determined according to the invention.
    [0076] 21) Evolution in a first rain gauge, determined with the simplified method of the invention.
    [0077] 22) Evolution in a second rain gauge, determined by means of a traditional dynamic laboratory calibration.
    [0078] 23) Evolution in a second rain gauge, determined according to the invention.
    [0079] 24) Evolution in a second rain gauge, determined with a simplified method of the invention.
    [0081] Figure 5 shows results of the validation tests of the invention, contrasting the real values of 45 different observations with those obtained through different methodologies, where:
    [0082] 25) Results obtained by means of a traditional dynamic calibration.
    [0083] 26) Actual measured value.
    [0084] 27) Results obtained through the invention.
    [0085] 28) Results obtained by a simplified method of the invention.
    [0086] 29) Assumption of a constant value recommended by the manufacturers.
    [0088] DESCRIPTION OF A PREFERRED EMBODIMENT
    [0089] The present invention refers to a method to increase the precision and reduce the errors generated by the variation of the intensity of precipitation in tipping cup rain gauges or any instrument for measuring fluids based on the tipping cup principle. The method starts from the design characteristics of the rain gauge and the understanding of its operation considering the variation in the intensity of precipitation, unlike conventional calibration methods based on experimental procedures that require time and qualified personnel. For this reason, the proposed method is easily adaptable to any cup rain gauge, simply by changing the initial parameters and allows its implementation in calculation routines or software for the automation of the correction of measurements, facilitating the process and reducing its implementation time.
    [0091] The method is based on the relationship between the excess water in the bowl during the falling movement of the rocker, which generates an increase in the tipping volume, and a decrease in the nominal tipping volume and the falling time of the rocker; caused by the kinetic energy of the water falling and impacting on this; either in the form of drops (at low intensities) or as a continuous jet (high intensities).
    [0093] The efficiency of the method is conditioned by: (i) the precision with which the necessary initial parameters are determined, (ii) a correct previous static calibration to set the nominal tilt volume at very low intensities, (iii) an adequate leveling of the the platform and (iv) the follow-up of the recommendations given by the manufacturers for the assembly and maintenance of the equipment.
    [0095] The water falling in the bowl, once its movement has started, is considered as surplus of the nominal volume, so the time that a drop or particle of water has to become a surplus (ts), will be given by the sum of the time that It takes the drop or particle of water that triggers the sway to travel the distance between the drain hole of the funnel and the impact zone in the bowl (td) and the time that the bowl will remain under the water fall line after starting its fall movement (tu), which is conditioned by the variation of the fall time of the bowl; minus the time it takes for the water droplets or particles to fall a sufficient distance to be collected by the wall that separates both cups during the tilting movement:
    [0100] In the formulas: h is the distance between the funnel orifice and the impact zone of the water falling into the bowl, hb is the height of the bowls, l is the linear distance between the upper central part of the wall that separates both cups and the line of fall of the drops, h is the gravitational acceleration, tt is the time of fall of the cup, ht linear distance traveled by the cup during its fall.
    [0102] The excess water will be given by the water flow from the funnel and ts, because the flow will increase with the intensity of precipitation the volume of Surplus water will also increase with intensity, however the falling water contributes kinetic energy to the balance of the rocker, energy that is increased with the increase in intensity, which generates the acceleration in the fall of the bowl and the decrease in volume. of tilting, consequently the decrease of your and of the time of fall of the bowl. This translates into a progressive decrease in the fraction of excess water increase as a function of the intensity of precipitation, which in turn is diminished by the progressive decrease in the tipping volume, generating that from some point the rate of The decrease in the tipping volume is greater than the rate of increase of the excess water, generating from that point a decrease in the error in relation to the increase in the intensity of precipitation, the opposite of what was seen in intensities below that point, where the error in measurement with reference to a constant tipping volume increased with precipitation. The reduction of the error will generally occur at very high and unlikely intensities in precipitation, however, the increase in the error at intensities below this point follows a non-linear trend, due to this compensation.
    [0104] The fall time of the bowl must be measured at very low intensities (close to zero), so that no excess drops interfere with the movement.
    [0106] In addition, it is recommended to perform multiple measurements to increase the accuracy of the measurement and reduce the random variability of the mechanism. As well as in the slope of decrease in the fall time of the bowl as a function of the increase in the intensity of precipitation, in both bowls.
    [0108] The determination of the decrease in the tipping volume as a function of the increase in precipitation can be determined experimentally from the results contrasted with real measurements in the laboratory. Knowing the factors that influence the increase in the volume of water measured in each tilt, as well as its decrease, a relationship is established between these that allows correcting errors based on the intensity of precipitation to increase the precision of a bowl rain gauge. tilting.
    [0110] A simplification to the method is provided by a relationship between the decrease in the drop time of the bowl, the decrease in the increase of water excess and the decrease of the tipping volume, with the increase of the precipitation intensity for the direct correction to the nominal value, the following can be applied:
    [0115] In the formula: Dt 'is the rate of increase of the corrected tilt precipitation expressed in precipitation depth, Dt is the rate of increase per nominal tilt or precision of the instrument in precipitation depth, Vt is the nominal volume of tilt, RI is the intensity of precipitation expressed as flow rate and tt is the fall time of the bowl.
    [0117] This simplification has been experimentally validated in the laboratory with two different models of cup rain gauges, presenting values similar to those obtained by a general dynamic calibration method, requiring fewer initial and experimental parameters for its application. Because the decrease in the tipping volume due to the action of the kinetic energy of the falling water is very low at low intensities, being significant at high intensities infrequent in precipitation records, so the previous simplification to the method is applicable to the precipitation measurement in cup rain gauges, as well as the following simplification to the method:
    [0122] In the formula: Dt 'is the rate of increase of the corrected tilt precipitation expressed in precipitation depth, Dt is the rate of increase per nominal tilt or precision of the instrument in precipitation depth, Vt is the nominal volume of tilt, RI is the intensity of precipitation expressed as flow and ts is the time that a water particle has to become a surplus.
    [0124] The invention has been subjected to validation processes both in its general version and in the simplified versions and has been contrasted with calibration techniques. traditional methods, obtaining similar satisfactory results, and even greater reductions in error, than conventional laboratory calibration methods and requiring less investment in time for their determination.
    [0126] In addition, they have been tested in cup rain gauges in real field conditions, performing the data calibration, applying the invention automatically by means of a software designed for this purpose in a satisfactory way.
    [0128] INDUSTRIAL APPLICATION
    [0129] This invention is of interest to companies dedicated to the manufacture of climate and environmental monitoring equipment, companies that provide climate management and monitoring software; and companies interested in climate and environmental monitoring. Mainly those sectors interested in the measurement of atmospheric precipitation and the management of water resources.
    权利要求:
    Claims (3)
    [1]
    1. A method for reducing the error in measurements caused by the variation in the intensity of precipitation and increasing the precision of measurement in tipping cup rain gauges or any instrument for measuring fluids based on the tipping cup principle , composed of a collecting funnel (1) that directs the water towards an outlet hole (2) from which it falls to a tilting mechanism (3), composed of opposite cups (4), whose movement is conditioned to a volume of fluid accumulated in relation to precipitation, water or fluid supplied from the outside, based on parameters of the equipment that allow determining the relationship between the addition of excess water in the bowl before and during its falling movement and the increase in intensity precipitation (RI) as well as the relationship of the latter with the decrease in the nominal tipping volume (Vt) and the decrease in the fall time of the bowl (tt); characterized by comprising the following steps:
    a) a first step that characterizes the behavior of the rain gauge in relation to the variation of the intensity of precipitation (RI) and determination of the volume of excess water added during the measurement and tipping process; where this first step comprises the following sub-steps:
    a1) surplus water contributed by the water droplet that triggers the swaying in the range of intensities where the water falls from the funnel in the form of drops, due to the variation in the size of the drop whose volume may exceed that necessary to break the balance of the rocker arm and excess water added during tipping;
    a2) Determination of the time that a drop or particle of water has to fall into the bowl and become a surplus (ts) given by: aa) the time it takes for the drop or particle of water that triggers the rocking to travel the distance between the funnel drainage hole and the impact zone in the bowl (td), ab) the time that the bowl will remain under the water fall line after starting its falling movement, conditioned by the variation of the bowl fall time (tu) and ac) the time it takes for the drops or particles of water to fall a sufficient distance to be collected by the wall that separates both cups during the tilting movement (thc); where this time relationship is described by an equation selected from a first equation

    [2]
    2. A simplified method for the reduction or correction of errors in the measurements of tipping cup rain gauges or any instrument for measuring fluids based on the tipping cup principle according to claim 1, characterized by the relationship between the variation of the time that the water particles have to fall into the bowl and become surpluses (ts), as expressed in claim 1 and the variation of the precipitation intensity (RI) or flow rate of the fluid through the funnel orifice; where said relationship is described by a third equation Dt ':

    [3]
    3. A simplified method for reducing or correcting errors in the measurements of tipping cup rain gauges or any instrument for measuring fluids based on the tipping cup principle according to claim 1, characterized by the relationship between the variation of the time of fall of the bowl (tt), as expressed in claim 1 and the variation of the intensity of precipitation (RI) or flow of the fluid through the orifice of the funnel where said relationship is described by a fourth equation Dt ' :
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    同族专利:
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    ES2831899B2|2022-01-25|
    引用文献:
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