Atmometer

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A Evaporators ( Greek, also Atmidometer or Evaporometer ), evaporation is a knife, an instrument for measuring the amount of evaporation.

Different methods are possible to measure the evaporation. An easy way to measure the evaporation, is to expose receptacles with a predetermined amount of water to the action of the atmospheric air. From the difference between the amount of water originally present and that which is left over after the expiration of a certain time, can determine the size of the evaporation. The difference can either be determined by the volume of the mass ( about the weight ) or; of both can, if the opening of the vessel is known, calculate the amount of evaporated water.

Thus, this method seems simple, it offers yet, if greater accuracy is required, some problems.

The two classes Evaporators can be divided depending on whether the evaporation is determined by the reduction of the volume or the weight loss of the water evaporation suspended. The Evaporators of the first class have the disadvantage that they are during frosty weather unsuitable for observation and destroyed by the frost often. The best-known apparatus of this type are constructed by Adolf Mühry, Prestel, Lament, Piche and morning star. This group includes Dufour Siccimeter which is to specify the difference between rainfall and evaporation. Many designs use the evaporation, which is determined by weighing. The best known are indicated by Saussure and wild, the latter of which is shown in the drawing.

In essence, the Evaporators of game from a cup-like vessel C, which can be placed on a letter scale of A similar device. Is the water bowl is empty, the pointer D is on the zero mark of the scale; but it is burdened by an over-molded water, so the pointer is lifted on the scale. When observing the shell C is filled with water, set to the pin B of the scale and record the reading of the pointer D on protractor G, hereupon removed from the scale and at the end of the observation period (24 hours) put back on the scale and the new position of the pointer determined.

The difference between the two readings are according to the nature of the division of either the weight of evaporated water or its height in millimeters. The whole weighing device is enclosed in a box E, in the under tray dish is prepared with calcium chloride, F, to keep the air inside of the same dry and to protect the metal parts of the instrument against oxidation.

As a result of evaporation observations made ​​so far shows that the same. Because of the influence that the temperature and air movement exercise, play only in an inadequate manner, the ratios of evaporation, as it occurs in nature For this purpose, only larger evaporation container or possibly EvapometerAutomatic are suitable in which the actual evaporation vessel is embedded in a larger, filled with water.