This battery-powered instrument records relative humidity from 20 - 99% and a temperature range from 14 - 1400 F. The memory function allows review of minimum and maximum levels reached from the time the monitoring began. Excellent for display cases, storage facilities, home libraries, and galleries. Temperature measured is accurate +/- 1.80F, humidity measued is accurate +/- 5% RH. Dimensions of the unit are 4.25" x 2.5" x .5" (107 x 65 x 15mm). Runs on one AAA battery, and can be wall mountable. Unit also has a switch on back to be switched to Celcius readings.