EXTECH RH300 Hygro-Thermometer Psychrometer


Price $99.99
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Extech Test & Measurement

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

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


Type | Range | Resolution | 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)