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What are rain gauges?

What are rain gauges?

What are rain gauges?Rain gauges are instruments used to measure rainfall and precipitation. In addition to rain, the water equivalent of snow, hail or sleet can be determined using rain gauges. That is why rain gaugesare also called precipitation meters. Other names are Ombrometer, Pluviometer or Hyetometer.

Today, Rain gauges are offered in analog and digital form. Analog devices are often very simple and less sophisticated. They consist in the basic structure of a measuring cup, which is often filled by means of a funnel in precipitation with water. After the precipitation, the height of the water filling can be read so that conclusions can be drawn on the amount of precipitation per square meter. Very simple rain gauges have a scaled measuring cup made of plastic, which is attached to a stick. This stick is stuck in the ground. The measuring cup is often open to catch the precipitate. He usually has a cylindrical shape. Sometimes the cup also conically narrows down. The measurement is usually quite inaccurate, because before reading again evaporated water or in strong wind and collected water can be blown away again.
More sophisticated analog devices such as the precipitation gauge according to Professor Hellmann have a scaled measuring cup, which is located inside a metal housing. The metal housing can be made of stainless steel or zinc sheet. The precipitate flows through a funnel into the collecting vessel. The measurements in a rain gauge according to Professor Hellmann are very accurate, because the closed metal housing prevents rapid evaporation and the continuation of the water. Almost all the water can be used for the measurement. The Rain gauges according to Professor Hellmann are also used as standard by professional weather services.

Very accurate are also digital rain gauge. These pluviometers determine the amount of precipitation via an outdoor sensor. This sensor contains tilting cups or tilting spoons, which fill with water during precipitation. After a while, they tip over like a seesaw and empty themselves. Based on the number of tipping operations, the unit calculates the total amount of water. The measurements are very accurate. The measurement results are transmitted via radio to the digital station. There, the measured values ​​can then be read off.



How does a rain gauge work?

In analogue rainfall meters, the scaled measuring cups fill with water during precipitation. The value can be read on the measuring scale. One millimeter on the scale corresponds to one liter per square meter. Thus, the read millimeters show how many liters of water per square meter have fallen. The distance of the scaling marks is also dependent on the shape of the measuring cup. If the cup tapers down slightly, the scaling line spacing must also increase downwards and vice versa.

With the measuring cups open at the top, the water is exposed to evaporation and the influence of the wind. This leads to inaccurate values. Accurate readings can only be obtained if the loss of water is close to zero.

The measurement in digital devices is based on the counting of tipping operations of the water bowls. These are located in the outdoor sensors of these devices. Each shell can only absorb a defined amount of water. When completely filled with water, it tips over. The number of tipping operations is electronically counted and added together. This automatically results in the amount of precipitation, which can be read on a display.

what should be considered when buying a rain gauge?

The rain gauge is mainly about its functionality.

It should be delivered accurate results. Unfortunately, this is not always the case with the very cheap devices.
But especially with decorative rain gauge, it can happen that the design affects to the detriment of accuracy.
So you should pay particular attention to the following points:

– The openings of funnels or cylinders should not be too narrow. These rain gauges have a much too small collection area for the precipitation. The measurement is thus too inaccurate, especially in wind air turbulence occur, which can still carry away the remnants of water. If you value the functionality of the rain gauge, you should keep your hands off these devices.

– If the measuring cylinder is made of pressed glass, often there are air deposits in the glass. If such air bubbles are detected in the glass, it is not recommended to buy the device. Because in cold weather these glasses are susceptible to breakage.

– Furthermore, should be tested with rain knives made of glass and whether the manufacturer offers replacement glass in the delivery.

– If you expect very accurate measurement results, you should look for the higher-quality tube rain gauge made of stainless steel or zinc sheet according to Professor Hellmann or radio rime knives

what should be considered when buying a rain gauge?

The rain gauge is mainly about its functionality.

It should be delivered accurate results. Unfortunately, this is not always the case with the very cheap devices.
But especially with decorative rain gauge, it can happen that the design affects to the detriment of accuracy.
So you should pay particular attention to the following points:

– The openings of funnels or cylinders should not be too narrow. These rain gauges have a much too small collection area for the precipitation. The measurement is thus too inaccurate, especially in wind air turbulence occur, which can still carry away the remnants of water. If you value the functionality of the rain gauge, you should keep your hands off these devices.

– If the measuring cylinder is made of pressed glass, often there are air deposits in the glass. If such air bubbles are detected in the glass, it is not recommended to buy the device. Because in cold weather these glasses are susceptible to breakage.

– Furthermore, should be tested with rain knives made of glass and whether the manufacturer offers replacement glass in the delivery.

– If you expect very accurate measurement results, you should look for the higher-quality tube rain gauge made of stainless steel or zinc sheet according to Professor Hellmann or radio rime knives

The history of the rain gauge

Rain gauges were used more than 2000 years ago in ancient India. They were simple cylindrical vessels, with which the precipitation was collected. Hints for the use of primitive rain gauge go back even to 500 years before the time. However, the first standardized rain gauge has only been clearly documented since the 15th century. Especially a lot of evidence comes from Korea. There were already used during the Yi Dynasty (Joseon Dynasty), which ruled in the period from 1352 to 1910, primitive rain gauge. With these, however, the depth of puddles was measured, which of course led to very inaccurate readings because the water was absorbed by the soil.
For this reason, the fourth king of the Joseon Dynasty (Sejong) of the then astronomical, meteorological and geographic research site Gwansanggam, had a device to develop, which could absorb the precipitation. This device was named Cheugugi. In contrast to the rain gauges, which determined the depth of the puddles, this device delivered many times more accurate measurement results. The Cheugugi was introduced in 1441 in the Korean capital. Just one year later, it was also used in the provinces.

This device consisted of an iron vessel, which was placed on a rectangular stone. The installation on a stone served to increase the only 30 centimeters high vessel. This was to prevent rain spatter from splashing from the ground into the container. The diameter of the vessel was 15 centimeters.

Since that time, however, the rain or rain gauge have experienced rapid development. A highlight was the invention of Gustav Hellmann in 1886. He developed a rain gauge, which is still used today. The rain gauge by Professor Hellmann is made of stainless steel or zinc sheet, has a catchment area of ​​up to 200 square centimeters and is bounded by a brass ring. This forms a cylindrical cavity that collects water and is protected to the outside.

The water is kept from evaporating, which makes the measurement accurate to within 0.05 millimeters. Snow can also be measured with this rain gauge.
To prevent turbulence in the snow, a snow cross can be used in the precipitation gauge by Hellmann. Then all you have to do is wait until the snow has melted. The rain gauge of Hellmann is still in many weather stations today
used.
Today, there are also radio-controlled precipitation meters in addition to the analogue rain gauge. Here, the measured values ​​are transmitted by radio up to 100 meters to a base station. At the same time, there are the latest developments in which rain gauge is networked with other meters. For example, the French company Netatmo, founded in 2011, is involved in the general networking of relevant technological processes and, especially in the meteorological area, offers the private user access to all measured values ​​of various private weather stations of apps. In addition to precipitation, temperatures, air pressure, wind speed and much more are transmitted. Professional meteorologists and hobby meteorologists are thus provided with extensive meteorological data, which can also be recorded in diagrams. Thus, weather trends and climatic changes can be recorded over longer periods of time.

Here you can find some decoratief like for example a Frog rain gauge or a Gnome rain gauge

 

 

 

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