The hygrometer is placed in places remote from heat sources at least 1 m and excluding direct sunlight on the hygrometer.

Purpose

Hygrometers M - 19 are designed to measure the relative humidity of the air at meteorological stations. It is used for the needs of the national economy. It is operated under canopies or indoors in stationary conditions.

Description of the hygrometer M - 19

The principle of operation of hair hygrometers M 19 is based on the property of a fat-free human hair to change its length with a change in the relative humidity of the surrounding air.

 The hygrometer consists of the following main parts:

• humidity sensor;

• specially processed human hair,  it is missing- torn;

• frames with a scale;

• arrows with axis;

• an adjusting device consisting of a rod with a weight and a screw, which serves to move the end of the pointer relative to the scale.

The change in the length of the hair is transmitted to the arrow of the hygrometer M - 19, which, moving along the scale, indicates the relative humidity in percent.

Metrological and technical characteristics of the hygrometer M - 19:

Range of indications of a hygrometer, % ……. 0 to 100

Measurement range of relative air humidity with a hygrometer at temperatures from minus 35 ºС to plus 45 °С …….. from 30 to 100

The price of the smallest division of the hygrometer scale, % ……… 1

Basic absolute error of the hygrometer, % no more …….. +10

Setting time of hygrometer readings, s, not more than ………. 150

Variations in hygrometer readings, %, not more than ………. 6

Change in hygrometer readings caused by changes in ambient temperature in the range of operating temperatures, %/°C, not more than ……… ±5

Overall dimensions of the hygrometer, mm, not more than ………. 30*160*290

Mass of the hygrometer, kg, not more than ………. 0.25

Probability of failure-free operation for 1000 hours, not less than ……… 0.94

Average service life, years, not less than ………… 8

Operating conditions, ° С from - 35 to + 45