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Extech RH300 Hygro Thermometer Psychrometer

Humidity, Wet bulb, Dew Point, Air Temperature plus External Probe Temperature measurements

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Extech RH300 Hygro Thermometer Psychrometer
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  • Extech RH300 Hygro Thermometer Psychrometer
  • Extech RH300 Hygro Thermometer Psychrometer
  • Extech RH300 Hygro Thermometer Psychrometer

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    Item #708

The RH300 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.


  • 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° resolution
Specifications Ranges Max Resolution Basic Accuracy
Humidity 10 to 90%RH 0.1%RH ±3%RH
Temperature (internal) -4 to 122°F (-20 to 50°C) 0.1° ±1.8°F or ±1°C
Temperature (external) -4 to 158°F (-20 to 70°C) 0.1° ±1.8°F or ±1°C
Dew Point -90.4 to 122°F (-68.0 to 49.9°C)
Wet Bulb -6.9 to 122°F (-21.6 to 49.9°C)
Dimensions 7 x 1.9 x 1" (178.5 x 48.4 x 24.7mm)
Weight 3.3oz (95g)