Hygrometer - Psychrometer

It is so humid in here. We would like to use air conditioner to reduce the humidity, but we don't want to waste energy, so a hygrometer will be useful. We checked its price in last weekend and decided to make our own.

We have a thermometer which can measure 2 temperatures. Here are some information about hygrometer and psychrometer and the psychrometric chart from wiki.

Hygrometers are instruments used for measuring humidity. A simple form of a hygrometer is specifically known as a "psychrometer" and consists of two thermometers, one of which includes a dry bulb and the other of which includes a bulb that is kept wet to measure wet-bulb temperature.

Psychrometrics or psychrometry are terms used to describe the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures. The term derives from the Greek psuchron (ψυχρόν) (cold) and metron (μέτρον) (means of measurement).