IE903481A1

IE903481A1 - Precipitation meter

Info

Publication number: IE903481A1
Application number: IE348190A
Authority: IE
Original assignee: Europ Economic Community
Priority date: 1989-10-09
Filing date: 1990-09-27
Publication date: 1991-04-10
Also published as: EP0422553A1; LU87603A1; EP0422553B1; PT95537A; DE59002187D1

Abstract

The invention relates to a precipitation measuring device. According to the invention, an acoustoelectric transducer (4) is arranged such that individual drops (6), hailstones or snowflakes generate an electrical signal upon striking a baffle plate (1) assigned to the transducer. Said signal is amplified and digitised and then analysed in a frequency analyser (10), whereupon the analyses are then interpreted in a programmable processor (11).

Description

The invention relates to a precipitation meter. According to 5 the invention, an acousto-electric converter (4) is disposed in the precipitation meter in such a way that single drops (6), hailstones or snowflakes produce an electric signal when hitting an impact plate (1) associated to the converter. This signal is amplified and digitalized and then analysed in a frequency analyzer, whereupon the analysed data are interpreted in a programmable processor (11).

Figure 1 t 1964 precipitation ·· 3A fo PUBLIC IN8P€C TION UNDER SECTION 89 ANO RULE 117 j ' · NO ( fe, Of 3 OF I o / q ί T ’ EUROPEAN ECONOMIC COMMUNITY (EEC), Batiment Jean Monnet, Plateau Kirchberg, L - 2920 Luxembourg. 2260 IE PRECIPITATION METER The invention is related to a precipitation meter 5 which is not only capable of recording the total rain amount between two inspection instants but also collects automatically and continuously informations from which the intensity of the precipitation, the size of the rain drops and possibly kind and intensity of other precipitations can be derived, for example hail or snowfall.

The classical method of rain measuring uses containers which are protected against vaporisation and which are emptied at predetermined instants for measuring. Such rain meters naturally deliver only indications as to the total amount of the precipitations having occurred during the observation period, recorded as equivalent amount of water.

Special weather radar devices, which furnish further informations like for example the rain intensity and the exact duration of a precipitation phase are very expensive and can only be used in a plane area.

It is the aim of the invention to indicate a precipitation meter which is less expensive than a weather radar and nevertheless supplies very detailed informations about kind, intensity and duration of precipitations. This aim is attained according to the invention in that an acousto-electric converter is disposed in the precipitation meter in such a way that single drops, hailstones or snowflakes produce an electric signal when hitting an impact plate associated to the converter, that this signal is amplified and digitalized and then interpreted in a programmable processor.

Preferably, a frequency analyser which detects the frequency spectrum of the signal precedes the processor.

The invention thus consists in the observation of the acoustic oscillations to which is submitted an impact plate hit by the single drops. Surprisingly, it has been found out that this observation, which can be carried out at low cost with modern electronic modules, leads to informations which enable to deduce the size of the drops and even permit a dis5 tinction between the different kinds of precipitations such as droplets, hailstones or snowflakes (the latter are best recognized when the acoustic signal of melting snowflakes is examined, i.e. when the impact plate can be heated), so that by accumulation, the precipitation intensity over a predetermined time period can be registered.

It has been found to be particularly advantageous to examine the output signal of the converter in a frequency analyser, since in that way the different kinds of precipitation can be distinguished particularly well from each other.

Advantageously, the impact plate is supplied with heating means which permit the operation of the precipitation meter also in winter for recording snowfalls.

Preferably, the surface of the impact plate which can be reached by the precipitations is so small that the impact of a single droplet, hailstone or a single snowflake on the impact plate can be registered. This implies a diameter of the impact plate between 1 and 5 cm.

Since frequency analysers nowadays are available as specially programmable semiconductor modules, which carry out the frequency analysis of a signal much faster than a programmed processor, it is advantageous to provide such a module separately from the processor and to feed the processor only with the final analysis data. But naturally it is also possible to transfer by a suitable programming the task of the frequency analyser to the processor, which is anyhow needed for the interpretation of the analysis data.

The invention will now be described more in detail by means of a prefered embodiment with respect to the drawings.

Figure 1 shows a schematic circuit of the electric part of the precipitation meter according to the invention, and Figure 2 contains time diagrams of two signals which are created in the acousto-electric converter at the impact of raindrops of different sizes.

Figure 1 shows schematically an impact plate 1, which can be brought to a temperature preventing ice formation by means of electric heating wires 2 and a heating current source (not shown). By means of a glue layer 3, the plate 1 is fixed to a piezoelectric cristal, which delivers an electric signal on an output line 5 when a raindrop 6 hits the plate 1. Two examples for signals on the line 5 are shown in Figure 2, the signal with smaller amplitude being caused by a raindrop with a diameter of 1 mm and the signal with greater amplitude being caused by a raindrop with a diameter of 2 mm.

The signal is raised in wide-band amplifiers 6 and 7 to a level which can be used for the digitalization. Between the two amplifiers a band pass filter 8 is disposed, which suppresses frequency ranges below 150 Hz and beyond 100 kHz.

The amplified and filtered signal is fed to an analog20 digital converter 9 which produces a series of discrete amplitude values of the signal and supplies them to a frequency analyser 10. The latter is for example a so-called FTT processor (Fast Fourier Transform) and supplies in a time duration which is short in comparison with the duration between two droplets hitting the plate 1 a digital indication concerning the frequency spectrum of the converter signal. From this indication, a processor 11 can differentiate, due to stored comparison values, between raindrops, hailstones and even snowflakes. In fact, with hail the frequency maximum is situa30 ted between 2 and 5 kHz, with rain between 10 and 20 kHz and with snowflakes beyond 50 kHz.

Now the signal amplitude of a signal as it is shown in Figure 2 is evaluated under consideration of the kind of precipitation (rain, hail, snowfall) in order to determine for example the size of a raindrop fallen on the plate 1 . From the number and the size of the raindrops fallen on the plate 1 in a time unit the processor 11 can derive the rain intensity and the total amount of rain.

If the measurement is only carried out with rain, the 5 frequency analysis is naturally superfluous and it is then sufficient to evaluate the amplitude of the signal in order to compute the size of the droplets, the intensity of the rain and the total precipitation amount. In this case, the digitalisation of the original signal could be omitted and only the envelope be evaluated, which simplifies the analog-digital converter .

In the frame of the invention, also other acoustoelectric converters can be used, for example dynamic microphones .

Claims

1. A precipitation meter, wherein an acousto-electric converter is disposed in such a way that single drops, 5 hailstones or snowflakes produce an electric signal when hitting an impact plate associated to the converter, this signal being amplified and digitalized and then interpreted in a programmable processor. 10

2. A precipitation meter according to claim 1, wherein the impact plate is provided with heating means.

3. A precipitation meter according to one of claims 1 and 2, wherein the surface of the impact plate which can be reached 15 by the precipitation has a diameter between 1 and 5 cm.

4. A precipitation meter according to one of claims 1 to 3, wherein the processor is preceded by a frequency analyser which evaluates the frequency spectrum of the signal.

5. A precipitation meter as claimed in claim 1 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. Dated this the 27th day of September, 1990 F. R. KELLY & CO.