The August station psychrometer consists of two identical alcohol thermometers, the reservoir of one of which is wrapped with a piece of thin hygroscopic tissue, dipped at one end in a glass of distilled water at room temperature. Due to the evaporation of water, the temperature of the wet thermometer will be lower than the temperature of the second (dry) thermometer. The thermometers are read 15 minutes after wetting one of them.
Assman’s aspiration psychrometer gives more accurate readings, as his body is enclosed in a metal case, which protects the thermometer tanks from the effects of radiant energy and air movement. Air movement is provided by the fan, which guarantees a constant speed of its movement around the thermometer tanks (2 m / s). The end of one of the thermometers is wrapped with a thin cloth and before each observation it is moistened with distilled water using a special pipette. The fan is started with the key and, after 3-4 minutes from the start of its operation, the readings are recorded. Measurements are made in the center of the room at a height of 1.5 m from the floor.
Hygrometer (from the Greek. Hygros – wet) – a device for directly determining the relative humidity. There are various types of hygrometers, but the most common of them are hair meters, which are based on the ability of a hair to lengthen in a humid atmosphere and shorten in a dry one due to hygroscopicity.
To determine the absolute humidity of the air, two types of devices are used, called a psychrometer (from Greek: psychros – cold): the August station psychrometer and the Assman aspiration psychrometer . Psychrometry principle is camping in a EFINITIONS testimony of two ter mome ters, the tank of one of the koto ryh SW lazhnen. Moisture, evaporating at different speeds depending on humidity and air velocity , takes away heat from the thermometer, therefore the readings of a wet thermometer will usually be lower than those of a dry one.
The principle of operation of a hygrograph is similar to that of a barograph and a thermograph. The device serves for recording continuous measurements of relative humidity, consists of a sensing element – a bundle of skim-free hair, a rotating drum with a tape, connecting levers and a pen with ink.