Published 17.09.2020 The device Hair hygrometer M-19 is designed to measure relative humidity at air temperatures below minus 10 ° C.
At meteorological stations, a hygrometer is installed for observations in a psychrometric louvered booth to exclude the influence of solar radiation and radiation from surrounding objects on the readings, as well as to protect against precipitation and strong gusts of wind.
The hygrometer consists of a hair, a nut, a lock nut, a frame, a scale, an arrow, a cam shaft, an arrow axis, a cam, a weight and a screw.
The hair in the hygrometer is attached at one end at the top of the frame on a regulator with a nut. The other end of the hair is fixed at the bottom on a cam with a weight, the weight keeps the hair taut. The cam is connected by a rod to the axis on which the arrow is fixed. A scale is attached to the frame, along which the end of the arrow moves. The scale has uneven, gradually decreasing divisions from 0 to 100. The divisions are numbered every ten. The scale division is equal to 1% relative humidity. The regulator nut is used to move the hygrometer needle. In working order of the hygrometer, the regulator nut must be secured with a lock nut.
The action of a hair hygrometer is based on the property of defatted human hair to change its length depending on changes in air humidity. When the relative humidity of the air decreases, the hair is shortened and the arrow turns to the left. As the humidity increases, the hair lengthens and the arrow turns to the right.
Using the readings of a hygrometer and a dry bulb thermometer at meteorological stations, such important characteristics of air humidity as dew point, partial pressure of water vapor and deficiency of air humidity saturation are calculated.