This pocket-sized REED digital psychrometer reads relative humidity and air temperature together, then works out wet-bulb and dew-point figures automatically so you don't need reference charts. It covers 0-100% RH and -4 to 122F (-20 to 50C) internal temperature, and adds Max/Min/Avg logging, a data-hold button, low-battery warning and auto shutoff in a compact one-hand body. This listing includes a NIST-traceable calibration certificate on top of the base instrument.