The REED R6001 Thermo-hygrometer is an electronic instrument that can measure and display the current temperature and relative humidity. The current temperature is measured by changes in electrical resistance due to heat; while relative humidity, which is the percentage that the air is saturated with water vapor, is calculated with changes in electrical resistance caused by changes in moisture. This digital thermo-hygrometer continuously updates and displays the numerical measurements on the screen when it is turned on. Displays ambient temperature and relative humidity on a dual LCD readout. 9. 5" (h) x 2. 1" (w) x 1. 3" (d). User selectable degree f / degree C. Min/Max memory for both functions. Data hold and Relative functions. Auto power off. Humidity range of 0 to 100% RH. Humidity resolution of 0. 1% RH. Humidity accuracy of + or -3% RH. Temperature range of -4 to 140degree f/-20 to 60degree C. Temperature resolution of 0. 1degree f/degree C. Temperature accuracy of + or -1. 6degree f/0. 8degree C. Powered by a single 9V battery (included). Weighs 6. 4oz. Dual LCD display shows temperature and humidity, high sampling rate of 2. 5 times/sec.