How to determine relative air humidity

How to determine relative air humidity

A feeling of discomfort is caused by too dry air, but the same feeling will be caused also by too high humidity of air. For control and maintenance in necessary limits of relative air humidity it is necessary to be able to determine it. There are several types of special devices (hygrometers) by means of which it is possible to measure relative air humidity: hair, membrane, psychometric, weight (absolute).

It is required to you

  • small glass capacity, hair, membrane hygrometers, 2 spirit thermometers, rectangular plate for thermometers, 6 buckles for fastening of thermometers and a cylinder for water to a plate, a cylinder for water, a fabric match.


1. There is quite easy way allowing to learn approximate humidity of air. Gather water in capacity and cool in the fridge up to the temperature of 2-3 degrees. Carry to the room and put far from heating devices. Look at capacity walls in 5 minutes. Walls dry – humidity of air low, walls damp – humidity of air average, on walls of capacity appeared water streamlets – humidity of air high.

2. The hair hygrometer consists of a metal framework, the arrow index and the fat-free hair tense between the index and a framework. This device uses ability of a hair to change the length depending on humidity of air. For measurement bring a hair hygrometer to the room. In 10 minutes consider instrument readings.

3. In a membrane hygrometer the humidity of air is perceived by a membrane from organic matter. Changes of provision of a membrane at change of relative air humidity are transferred to the arrow system attached to it. At measurement of humidity of air such hygrometer wait 20 minutes, then consider instrument readings.

4. Indications of the psychrometer are more exact. In the absence of factory it is possible to manufacture the self-made psychrometer. 4 buckles attach 2 spirit thermometers to a plate. Between them 2 buckles attach a cylinder for water. Wind a cylinder with alcohol of one thermometer with fabric and fix by a thread. Lower the free edge of fabric in a cylinder with water. Calculate humidity of air according to the table recorded on the image to a step.

Author: «MirrorInfo» Dream Team