A psychrometer is a device that includes both a dry-bulb and a wet-bulb thermometer.
From the en.wikipedia.org
A wet-bulb thermometer is an instrument which may be used to infer the amount of moisture in the air.
From the en.wikipedia.org
Even though specialized tools such as the wet bulb global thermometer are available, not all football coaches decide to use them.
From the sciencedaily.com
The value indicated by a wet-bulb thermometer often provides an adequate approximation of the thermodynamic wet-bulb temperature.
From the en.wikipedia.org
If the air surrounding a wet-bulb thermometer is dry, evaporation from the moist wick will be more rapid than if the air is moist.
From the en.wikipedia.org
When the air is saturated, no water will evaporate from the wick and the temperature of the wet-bulb thermometer will be the same as the reading on the dry-bulb thermometer.
From the en.wikipedia.org
The accuracy of a simple wet-bulb thermometer depends on how fast air passes over the bulb and how well the thermometer is shielded from the radiant temperature of its surroundings.