The RH300 is a small meter that is suited for field use. Simultaneously displays relative humidity (10% to 90% RH), ambient temperature, and dew point or wet bulb. Calculates T1-T2 differential (air temperature minus external probe temperature) with optional probe (TP890) and T2 minus dew point. Sensor cap with built-in protection. Additional functions include Data Hold, Auto Power Off, and MAX/MIN reading. Comes with two AAA batteries.