Extech 5 in 1 environment tester hygro thermo anemometer light sound meter extech en300 the extech en300 5 in 1 environment tester measures humidity temperature air velocity light and sound in one compact hand held unit its large dual lcd simultaneously displays temperature and air velocity or relative humidity as the meter has sensors top and bottom the characters on display reverse direction depending on mode hygro thermo anemometer or light sound a built in low friction vane wheel