Question

How is relative humidity determined ?

Answer 1

Hey here is your answer !!!

Relative humidity represents the extent to which air is saturated with moisture at a given temperature. When raising plants, you should have some idea of the relative humidity, especially in the winter. If you get a shock from a spark every time you touch something, it is certainly too dry. If water is condensing on the windows, the air is too moist (at least for the health of your house).

A hygrometer is used to measure the level of humidity. The usual type that you can buy is typically made from a fibre (originally horse hair) that changes length with changes in humidity. Because the fibre hygrometer can be affected by many different conditions, it should be calibrated quite regularly. They are especially quite inaccurate at very high and low humidities.

A sling psychrometer is similar portable device used to measure relative humidity. An example and explanation is found here. Obviously easy to fabricate using a couple thermometers.

Answer 2

Relative humidity is the ratio of amount of water that is present in air to the amount of water vapour or the moisture which the air can hold

Hope it’s helpful...