The RH300-NIST is a compact meter that is ideal for field applications. Simultaneously displays relative humidity (10% to 90% 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. Built-in protective sensor cap. Other features include Data Hold, Auto Power Off, and MAX/MIN reading. Complete with 2 AAA batteries. Includes certificate traceable to NIST.