An essential tool for experimental measurement of air relative humidity. It is widely used in grain storage, greenhouse cultivation, sericulture, tobacco harvesting and drying, weather observation, food processing, and other applications. Features: Function: Analog thermometer and hygrometer measures temperature and humidity Easy to read: Bold and easy-to-read numbers; fade-resistant markings for clear visibility High-grade material: High-impact, durable plastic construction for long-lasting performance Wide application: Suitable for basement, garage, barn, greenhouse, laboratories, nursery, room, and more No battery needed: Mechanical design requires no batteries, providing reliable, maintenance-free operation Specifications: Temperature measurement range: -10°C to 50°C (-20°F to 122°F) Measurement error: ±2°C (±3.6°F), Accuracy class: 1.5 Humidity measurement range: 0% to 100% RH Measurement accuracy: ±5% RH Red size: 257 x 92 x 25 mm Blue size: 300 x 105 x 30 mm Instructions for use: 1. Hang the wet and dry bulb thermometer in a well-ventilated area. Keep the wick and water reservoir clean. 2. Fill the water reservoir with clean water and ensure the wick is immersed before use. 3. The humidity reading is based on the temperature difference between the dry and wet bulbs. When both bulbs show the same temperature, the air is saturated with moisture (100% RH). 4. The rotating dial at the base serves as a psychrometric chart to determine relative humidity. 5. To use: Align the dry bulb temperature scale with the wet bulb temperature scale using the rotating dial. The value indicated by the arrow on the humidity scale is the relative humidity percentage. Package included: 1 x Dry and wet bulb hygrometer thermometer