Measures and records temperature from - 20 to 120°F, +40 to +110°F, relative humidity from 0 to 95% (Non-condensing). Accurate to within c 1.8°F for temperature; ± 2% from 0 to 60%RH, ± 3% from 61 to 95%RH. 1, 7 and 31 day recording time. AC adapter, 4" D batteries. Microprocessor control and electronic sensing.