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Extech RH300 Digital Psychrometer

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  • Humidity range: 1%-100%
  • Humidity accuracy: +/- 3% Rh
  • Temperature range: -4°-to-122°F
  • Temperature accuracy: +/- 1.8°F
  • Measures dew point
Availability: Typically in stock (Details)

Product Information

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).



More Information
Brand Extech
Category Thermo-Hygrometer
Warranty Information One (1) year from the date of purchase on parts and labor
Condition new
Manufacturer Model Number RH300
Thermo-Hygrometer Calculations Dew Point, Rh, Temp, Wet Bulb
Thermo-Hygrometer RH Range 10 to 90%
Thermo-Hygrometer Temp Accuracy ± 1°F
Thermo-Hygrometer Temp Range 32° to 122°F
Thermo-Hygrometer RH Accuracy +/- 3%


Extech RH300 Digital Psychrometer Product Information

Manual / Schematic
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