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Extech RH300 Digital Psychrometer

Out of stock accepting backorders.

Product Highlights

Compact and affordable, the Extech RH300 Digital Psychrometer measures air temperature, relative humidity, wet bulb, and dew point. Plus, it gives you all the extras that make taking measurements easy: a data hold switch, memory function, low battery indicator, and auto power off.
  • Humidity range: 1%-100%
  • Humidity accuracy: +/-3% Rh
  • Temperature range:-4°-to-122°F
  • Temperature accuracy: +/-1.8°F
  • Measures dew point
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Product Description

The Extech RH300 Digital Psychrometer measures air temperature (-4°F to 122°F), relative humidity (0-100%), wet bulb, and dew point (-90.4°F to 122°F).


Designed like a microprocessor, you get data hold, low battery indicator, auto power off, and memory (minimum, maximum) functions. Batteries are included.


The unique sensor cap design lets you simply twist the cap to close and protect the sensor during storage.



  • Displays: 
    • Dew point (-90.4°F to 122°F)
    • Temperature (-4°F to 122°F)
    • Wet bulb
    • Relative humidity  (0-100%)
  • Min/max memory
  • Data hold
  • Auto power off
  • F/C switch
  • Pocket clip
  • Low battery indication


Comes with:

  • Batteries
  • Protective cap with pocket clip


How to Read the RH300 Display:

  • At the top of the screen, you will see the RH (Relative Humidity)
  • At the bottom left, you will see t1 or DB (Dry Bulb, which is actually the Ambient Room Temperature)
  • At the bottom right, you will see WB (Wet Bulb Temperature) and then F (Fahrenheit)


The WB (Wet Bulb) temperature is NOT the true Fahrenheit temperature reading in the room. WB is a ratio between the DB (Dry Bulb) temperature and the RH (Relative Humidity).


The lower left hand side reading on the meter is the real temperature in the air. Though the display shows t1 and not F (for Fahrenheit).

Technical Specifications

Brand Extech
Thermo-Hygrometer Temp Accuracy ± 1°F
Category Thermo-Hygrometer
Condition new



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