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 more.Features: Function: Analog thermometer and hygrometer measures temperature and humidity Easy to read: Bold and easy-to-read numbers; you can read the measuring data easily, with fade-resistant markings High-grade material: High-impact, durable plastic construction; reliable material ensures long-lasting performance Wide application: Ideal for basement, garage, barn, greenhouse, laboratories, nursery, room, and more No battery needed: The thermometer is mechanical and not electronic; no batteries required, saving time and money Specifications: Temperature measurement range: -10C to 50C (-20F to 122F) Measurement error: 2C (3.6F), 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 from this wet and dry bulb thermometer is based on the Celsius scale. When both thermometers show the same temperature, the air is at saturation point. 4. The rotating calculation dial at the bottom 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 below is the relative humidity percentage. Package included: 1 x Dry and wet bulb hygrometer thermometer