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Extech RH390 Precision Thermohygrometer, 0 to 100% RH, -22 to 199F

Extech  |   Mfr# RH390  |   Item# DO-37803-33

$199.99 USD/EACH

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  • Measures relative humidity with ±2% accuracy
Precision capacitance humidity sensor offers fast response. Slim design with rubberized sides for better grip and easy, one-handed operation. The dual LCD provides simultaneous display of humidity and temperature, or humidity and dew point, or humidity and wet bulb. Advanced features include data hold, min/max readings, low-battery indication, and auto power off.
What's Included:
one 9 V battery and carrying case
Product Type Thermohygrometer
RH range (min) 0%
Temp range -4 to 199°F (-20 to 100°C)
RH range (Max) 100%
RH range 0 to 100%
Max temperature (º C) 100
RH accuracy ±2%
RH resolution 0.1%
Min temperature (º F) -4
Min temperature (º C) -20
Max temperature (º F) 199
Temp accuracy ±1.8°F (±1.0°C)
Temp resolution 0.1°F/°C
Dimensions 1.625 in W x 7.75 in H x 1.25 in D
Dewpoint Yes
Wet bulb Yes
Response time 30 seconds
CE Compliance Yes
Model RH390
Qty/ea 1
Manufacturer number RH390
Brand Extech
Display LCD,
Power One 9 V battery (included)


at $158.00 USD/EACH
Usually ships in 14 days.

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Questions and Answers

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2 Questions | 2 Answers
Displaying questions 1-2
  • Q:

    Is this unit able to be calibrated and does it come with a certificate?
    Asked on 5/4/2011 by Anonymous

    1 answer



      This product can be calibrated to meet the standards provided by the National Institute of Standards and Technology (NIST), with the addition of P/N: 17005-00.

      Answered on 5/4/2011 by Chris from Technical Support
  • Q:

    is this device has a charger?
    Asked on 10/8/2010 by Anonymous

    1 answer

    • Staff Reviewer


      No, this item takes standard 9V batteries, there is no AC adapter currently available.

      Answered on 10/12/2010 by Jen from Technical Support
Displaying questions 1-2

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Product Reviews


by PowerReviews
Extech RH390 Precision Thermohygrometer, 0 to 100% RH/, -22 to 199F

(based on 1 review)

Reviewed by 1 customer

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(2 of 3 customers found this review helpful)


On Inspection...

By Randers

from Waukesha, WI

About Me Academic/Professional Researcher

Verified Buyer


  • Accurate
  • Durable
  • Easy To Use
  • Well Calibrated
  • Works Properly


    Best Uses

    • In The Field

    Comments about Extech RH390 Precision Thermohygrometer, 0 to 100% RH/, -22 to 199F:

    Our company uses this product for attic inspections. The quick readings are incredibly helpful and essential to inspecting in a timely manner.

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