The Extech RH300 is a compact meter that is ideal for field applications. Simultaneously displays relative humidity (10 to 90 percent RH), air temperature and dew point or wet bulb. Calculates T1-T2 differential (air temperature minus external probe temperature) using optional probe (TP890), and T2 minus dew point. Compact meter is well-suited for field applications. Unique sensor cap closes to protect to protect meter during storage. Advanced features include Data Hold, selectable Auto Power Off, and MAX/MIN/Average reading.