FI118980B - Rain sensors and method for measuring rain - Google Patents

Description

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Rain sensor and method for measuring rain Ί j 0980

The invention relates to a rain sensor according to claim 1.

The invention also relates to a method for measuring rain according to claim 10.

The invention is used to measure rain intensity and rainfall.

10 The most commonly used rain sensors are rain counter type sensors (tipping buckets) with a funnel-type collector and a small volume measuring container underneath. The measuring vessel is automatically tracked to drain automatically whenever it accumulates a certain amount of water, most simply by a flip-board type mechanism. A pulse is obtained from the meter whenever the measuring container is empty, so that one pulse corresponds to a certain amount of rain, eg 0.1 to 15 mm. The use of Tipping bucket sensors includes: problems like:

Their basic problem is poor resolution. The resolution is determined by the volume of the measuring container. Light rainfall where the total precipitation is below the volume of the measuring cup will not be fully recorded.

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Another problem is the "dead time" of the sensor. During the dip of the measuring cup *: water dripping from the collector may not be measured. This causes a measurement error • ·: * '*, especially when the rain intensity is high.

The blockage of moving parts due to contamination or, for example, insects that have entered the sensor structures also causes measurement error.

* · • · • · ·. Attempts have been made to solve these problems. with a sensor structure that does not have a separate measuring · · ... vessel but leaves the collector in individual drops, the number of which is counted.

• *

The counting is done, for example, by dropping the droplets into an electric circuit (US

»· ·" · * Patent 4,520,667) or optically (International Patent Application PCT / DK98 / 00425).

* * • · • · *

Typical for known solutions is that the collector is designed to: • · **. * ·: Produce droplets of as uniform size as possible, regardless of the conditions and the intensity of the rain 118980 2. In this case, the number of droplets is directly proportional to the amount of rainfall. The disadvantage is that the structure of the droplet forming part of the collector becomes mechanically complicated, easily clogged and expensive to manufacture. In mechanically simple implementations, the droplet size of the water leaving the hopper varies according to the intensity of the 5 rain resulting in a measurement error (Stow et al., Journal of Atmospheric and Ocenic Technology, vol. 15, pp. 127-135).

The object of the present invention is to eliminate the problems of the prior art and to provide a completely new type of rain sensor and method for measuring rain.

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The invention is based on the fact that the rain sensor consists of a funnel-like collector, in which the rainwater is discharged in single droplets, and a sensor operatively connected to the collector, which provides a signal proportional to the size of the droplet leaving the collector.

More specifically, the rain sensor according to the invention is characterized in what is stated in the characterizing part of claim 1.

The method of measuring the rain according to the invention, in turn, is characterized by what is disclosed in the characterizing part of claim 10.

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The invention provides significant advantages.

The measuring method allows for a very simple and inexpensive mechanical design, since the variation in droplet size is allowed. The collector may be e.g. a funnel with a straight '* 25 outlet. Further, contamination or partial clogging of the collector will not cause a * measurement error, provided that water is nevertheless discharged through the outlet. Thus, • * '· · · * measurement error due to varying droplet size can be eliminated.

* .. * In the following, the invention will be examined by means of the working examples illustrated in the accompanying figures.

Figure 1 schematically illustrates one force sensing device. '' 'According to the invention for measuring rain.

• · »* *» lf • · 118980 3

Figure 2 schematically shows another capacitance measuring apparatus according to the invention for measuring rain.

Figure 3 is a block diagram of a third charge measurement device 5 according to the invention for measuring rain.

Fig. 4 is a block diagram of a fourth optical measurement apparatus according to the invention for measuring rain.

Figure 5 is a graph showing the water droplet impulse in one of the apparatuses of the invention.

Thus, the rain sensor according to the invention consists of: 1) For example, a funnel-like collector which discharges the rainwater as single droplets and 2) a sensor functionally connected thereto, which provides a signal proportional to the size of the droplet leaving the collector.

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The relationship between droplet volume and detector signal is determined either. . laboratory or field tests. The precipitation is then calculated by summing the volumes of the individual droplets from the detector signals »· ♦ • · ·" 1 1.

• M

*. , by calculating the change in rainfall over the selected measurement period.

• · ·.! »: 25 • ·

Drop counting and volume measurement can be accomplished in a number of different ways, using •, ···, eg piezoelectric, capacitive, optical, or electric droplet charge • · ·· ♦ methods.

30 Force Sensor Detection • · · · »··

The principle of an embodiment based on a force transducer, for example piezoelectric detection, is shown in Figure 1. According to the invention, the transducer comprises a collecting vessel 1, 9 9 9 "I, 1 having a large cross-sectional collecting end 2 and a low cross-sectional discharge end 3. Such a collector 1 is typically funnel-shaped. The droplets falling from the outlet end 3 of the collector 1 hit the detector plate 11 of the measuring device 4 to which the piezoelectric force sensor 5 is attached. .

The particular advantages of piezoelectric detection are, firstly, that the detector part can be completely closed, whereby the electronics are protected from moisture and dirt. Second, the power consumption of the metering electronics is easily minimized by using a processor 10 having a so-called "ready-to-use" processor. “Sleep-mode” function. If, within a certain time set in the processor program, no droplets emerge from the collector 1, the processor switches the measurement electronics to sleep mode with very low power consumption. The processor can be woken up by applying a voltage to a specific input. When piezoelectric detection is used, the voltage pulse generated by the detector can be used as the excitation signal, whereby the measuring electronics enters the measuring mode as the first drop of water drops onto the detector. For example, a capacitive acceleration sensor, a sensor made of conductive plastic or a sensor made of piezoelectric plastic can be used as the force sensor. The droplet volume is calculated computationally in block 13. The force transducer may also comprise force-transmitting structures, such as lever structures or the like, instead of the direct force measurement shown.

: To determine the droplet volume, proceed as follows. As it strikes the detector plate 11, the rain droplet exerts a force which is transmitted to the force transducer 5 and is detected at its output as a voltage pulse. The pulse shape is recorded and one or more parameters proportional to the droplet volume are measured. Suitable parameters are e.g.

• «· · · | * peak-to-peak pulse voltage (Vpp), maximum or minimum voltage, or • · '···' half-width of the pulse (wl4). A typical pulse shape and the parameters determined from it are shown in Figure 5.

In some cases, the response of the detector is also influenced by factors other than the size of the drop ··· # · · V *, such as temperature. If necessary, these can be measured with separate sensors and ··· • · * · · · * included as additional parameters in the calculation.

··· ···· • ·:. * · · The droplet volume is now calculated using the expression 5 118980 V = f {pl, ... pn, ql, ... qm) where V is the droplet volume, ρΐ, .ρη are the values of the droplet size dependent measurement parameters and ql ... qm values for additional parameters required, such as temperature. The function f represents the relationship between these, which has been determined experimentally by either laboratory or field tests.

Capacitive detection

The principle of the detector is shown in Fig. 2. The outlet pipe 3 of the collector 1 is made of conductive material and a conductive ring 12 of larger diameter is placed beneath it. The detector measures the capacitance between the outlet pipe 3 and the lower ring 12. Because rainwater is always somewhat conductive, a drop forming on the outlet 15 of the outlet pipe forms a conductive electrode for capacitance measurement. Consequently, as the drop increases, the capacitance between the exhaust pipe 3 and the outer ring 12 also increases until the drop 10 drops and the capacitance returns to its initial value. The change in capacitance when the droplet 10 drops is proportional to the size of the droplet 10 and can be used as the output signal of the detector. The droplet volume is determined computationally in 20 blocks 13.

; A | · Electric Charge Detection • A: The measurement principle and one embodiment of the measurement electronics are shown in Figure 3.

* · ** · 25 The droplets 10 falling from the collector 1 are electrically charged by means of the DC voltage.

The amount of charge a droplet depends on the surface area of the droplet 10 and, therefore, its volume. A droplet 10 drops onto a conductive electrode 14 below which is connected to the input of a charge sensitive amplifier 15. The output of the measuring circuit produces a signal proportional to the drop charge; in the case of a pattern, a burst in which the number of pulses • · *; · * 30 depends on the charge of the droplet. Charge measurement can also be performed in ··· V · other ways. Based on the charge, the droplet volume is determined in block 13.

»· Opt * *::: Optical Detection::: 89 89 118980 6

Detection may also be performed optically according to Fig. 4, e.g. by dropping a light beam passing from the light source 11 to the photodiode 12 or the like of the optical unit 9. The larger the droplet diameter, the longer the light beam is cut off; this length can be used as the output signal of the detector 5. Based on the optical signal, the volume of droplet 10 is determined in block 13.

For the purposes of this application, an electroactive plastic is one whose plastic property is affected by the changing forces exerted on it. Such electrical properties include conductivity, specific capacitance, etc.

It is also possible to make the funnel heated. Particularly in the case of snowfall, a collecting funnel comprising a heated funnel would also provide information on the amount of rainfall and the water value of the snowfall.

15 • a a • · a • aa • • • • • • • • • • • • • • • • • • a • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Claims (17)

1189; A rain sensor comprising - for example, a funnel-shaped rain collecting vessel (1) having a collecting head (2) for collecting rain 5 and a collecting head having a cross-sectional outlet (3) for conducting rain measurement, and , characterized in that the measuring device 10 comprises means (4,13) for determining the volume of a single droplet. A rain sensor according to claim 1, characterized in that the measuring device (4) comprises a force sensor (5) fitted to the drop drop path, by means of which the volume of the drop drop can be determined. Rain sensor according to claim 1 or 2, characterized in that the force sensor 15 is a piezo sensor. A rain sensor according to claim 1 or 2, characterized in that the force sensor * · • is a capacitive acceleration sensor. A rain sensor according to claim 1 or 2, characterized in that the force sensor is a sensor made of electroactive plastic or piezoelectric plastic. • · • · • M A rain sensor according to claim 1. characterized in that the measuring device comprises a capacitive transducer (6) adapted to the drop path of the droplet, by which the capacitance proportional to the volume of the droplet · · * ·; means (13) for determining a droplet volume by means of a measured capacitance. • · * · · • · · · · 1 · · 2 • e • · · 118980 A rain sensor according to claim 1, characterized in that the measuring device comprises means (7) for charging the drop with an electric charge and measuring means (8) for measuring the drop charge and additionally calculating means (13) for determining the mass of the drop. A rain sensor according to claim 1, having optical means (9) for measuring the amount of rain, characterized in that the sensor further comprises means (13) for determining the droplet volume of the optical signal. A rain sensor according to any one of the preceding claims, characterized in that the collecting hopper is heated. A method for measuring rain, comprising: - collecting rainwater by means of, for example, a funnel-shaped rain collecting vessel (1) having a collecting head (2) for collecting rain and a collecting head having a smaller cross-section (3) ) by means of a measuring device (4) located in the vicinity, · · t:: characterized in that: ··· · 5 ··· · ····················································icing • · A method according to claim 10, characterized in that the force exerted by the falling drop is measured to determine the volume of the drop. t · t · * ··: ***: The method according to claim 10 or 11, characterized in that a piezo sensor is used as the force. • ·· • · • ·. Method according to Claim 10 or 11, characterized in that the force sensor "" ϊ ·!!!! On on on is a capacitive acceleration sensor. " Method according to claim 10 or 11, characterized in that the force sensor is a sensor made of conductive plastic or piezoelectric plastic. Method according to claim 10, characterized in that a capacitance proportional to the volume of the droplet is determined, from which the volume of the droplet 5 is determined. A method according to claim 10, characterized in that the falling drop is charged by electrical charge and the drop drop charge is measured from which the drop volume is further determined. The method according to claim 10, characterized in that the droplet volume 10 is determined by an optical method. • 1 1 ♦ • · · · · · ♦ «« 1 1 1 1 1 1 1 1 1 1 1 1 1 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ›