Starting at $427.89 Starting at $342.31 Found a better price? Let us match.



  • Humidity range: 0 to 100% RH
  • Absolute humidity range: 0 to 1120 GPP (0 to 160 g/kg)
  • Temperature range: -22 to 199°F (-30 to 100°C)
  • Dewpoint range: -22 to 199°F (-30 to 100°C)
  • Wet bulb range: 32 to 176 °F (0 to 80°C)
  • Basic accuracy: ±2% RH, ±1.8°F/1°C
  • Resolution: 0.1% RH, 0.1°F/°C
  • 30 second response time

What's in the Box

  • Carrying case
  • 9V battery


The Extech RH490 hygro-thermometer is a precision hygro-thermometer specifically designed for HVAC and water damage restoration contractors. The Extech RH490 hygro-thermometer features a fast 30 second response time and an accuracy of ±2%. The dual backlit display simultaneously shows humidity or water vapor in grains per pound (g/kg) along with either temperature, dew point, or wet bulb.

The Extech RH490 hygro-thermometer features a slim, handheld design with rubberized sides for better grip and for one hand operation. The Extech RH490 hygro-thermometer has data hold and min/max functions as well as auto power off with disable and low battery indicator.

In Stock

Manufacturer Stock

This stock is typically available to ship in 3 - 5 working days.

Part Number Price Available
$342.31 50 in stock

Interested in Other Part Numbers?

Other part numbers are available to order but are not currently in stock. Current availability for non-stock parts is "Usually ships in 3-5 business days". Click here to select options