An instrument commonly used to measure humidity is the hygrometer. Hygrometers can be mechanical or electronic, and they measure the amount of moisture in the air. Some basic hygrometers use materials that absorb moisture, causing a change in their physical properties. More advanced electronic hygrometers use sensors that detect humidity levels by measuring electrical resistance or capacitance changes in the presence of water vapor. Accurate humidity measurements are important in various fields, including meteorology, agriculture, and HVAC systems, to ensure proper climate control and to understand weather patterns.