This Digital Psychrometer provides simultaneous relative humidity and air temperature readings, as well as automatically calculating wet bulb and dew point temperatures without needing to consult charts. Simultaneous display of %RH, temperature and dew point or wet bulb. Optional external probe (87P6) for contact/differential temperature measurement. Max/Min/Avg readings. Data Hold Function. Low battery indicator and auto shut-off. Temperature Measuring Range: -4 to 158°F (-20 to 70°C) Dew Point Measuring Range: -109 to 122°F (-78 to 50°C) Wet Bulb Measuring Range: -69 to 122°F (-21 to 50°C) Dimensions: 7 x 1.9 x 1 (179 x 48 x 25mm) Operating Humidity Range: 10-80% ASIN B008S0H9E4 Batteries 2 AA batteries required. (included) Manufacturer Reed Item model number 8706 Product Dimensions 7 x 1 x 1.9 inches; 2.47 ounces Is Discontinued By Manufacturer No