Extech RH390 Precision Psychrometer

Offers a dual backlit display

The Extech Precision Psychrometer RH390 has a high 2% RH accuracy, a fast response time, less than 30 seconds, and a dual backlit display.

The RH390 can simultaneously display humidity and temperature, humidity and dew point, or humidity and wet bulb measurements.


  • Offers a dual backlit display
  • Made with a slim design complete with rubberized sides for better grip and for one hand use
  • Includes Data Hold and Min/Max functions
  • Auto-powers off with disable feature
  • Alerts user with low battery indicator
  • Has a simultaneous display of humidity/temperature, humidity/dew point or humidity/wet bulb


Humidity 0 to 100%RH
Internal Temperature -4 to 199°F (-20 to 100°C)
Basic Accuracy ±2%RH, ±1.8°F/1°C
Max Resolution 0.1%RH, 0.1°F/°C
Dewpoint -22 to 199°F (-30 to 100°C)
Wet Bulb 32 to 176 °F (0 to 80°C)
Dimensions 7.8" H x 1.7" W x 1.3" D
Weight 7 oz (200g)

NIST Calibration

The Extech RH390 Precision Psychrometer is available with standard factory calibration or with NIST Calibration Certification (adds 5 days to product lead time). NIST certification offers a traceable certificate that satisfies ISO & other regulatory requirements for product accuracy traceability to nationally recognized reference standards.

2 Reviews Hide Reviews Show Reviews

  • 5
    Excelent Product

    Posted by Jorge on Jun 1st 2010

    Precision and good product

  • 5
    Excelent Product

    Posted by Jorge on May 28th 2010

    Excelent Product, Price/Value, as its named Precision

Please see our warranty page for more information regarding the warranty on this item.

Return Information

  • Return windows close 30 days after you receive your item.
  • You are responsible for obtaining a Return Merchandise Authorization, the cost of shipping, and potential restocking fees, if the item has been opened.
  • To start a return, or to view the full returns policy, click here.
Your Price
Ships Free (US 48)
Ships in 2-3 weeks

Learn more about each option

Select an option...

  • NIST Calibration
  • Order Review

*Cycle through all the options by clicking the "Next" and "Back" buttons below

Click the next button to move to the next option

Select to see the list of options, and click each option to explore


Build Progress

( 0% completed)