Simultaneous display of RH, Temperature and Dew point or Wet Bulb or Probe Temperature. Wet bulb measurements without slinging. Calculates T1-T2 differential (Air Temperature-External Probe Temperature) using optional probe. Unique sensor cap design twists to closed position for protection during storage. Switchable F/C temperature units with 0.1 degree resolution. RH305 includes RH300 meter, 33 and 75 percent calibration bottles, temperature probe and carrying case.