Lufft certified thermohygrometer Model #100 measures relative humidity, temperature, absolute humidity and dew point. It has a 4" overall brass plated case that can be wall or desk mounted. The 3-1/2" dial has a glass cover. The silver face has black figures. The precision Durotherm hygrometer element is accurate within ±4% RH. The dial indicates the complete range of 20 to 100% relative humidity. Humidity graduations are in 4% RH. The bi-metallic thermometer is accurate to 2°F with a range of 20 to 100°F. Temperature is in graduations of 2°F.