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Extech RH490 Thermo‑Hygrometer with Grains Per Pound (GPP)

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  • Humidity range: 0% to 100%
  • Humidity accuracy: +/-2%
  • Temperature range:-4° to 199°
  • Temperature accuracy: +/-1.8°
  • Also measures dewpoint, wet bulb and grains per pound (GPP)
Availability: Typically in stock (Details)

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Product Information

The Extech RH490 Thermo-Hygrometer is well known in the restoration community for its fast response time load of features. It also offers operators unparalleled accuracy and durability. Comes with a carry case and 9V battery.



  • Less than 30 seconds RH response time
  • Water vapor in GPP (g/kg)
  • Dual backlit display
  • Simultaneous display of:
    • Humidity or GPP (g/kg) plus Temperature
    • Humidity or GPP (g/kg) plus Dew Point
    • Humidity or GPP (g/kg) plus Wet Bulb
  • Slim design with rubberized sides for better grip and for one hand operation
  • Data Hold and Min/Max functions
  • Auto power off with disable and low battery indicator
  • Complete with carrying case and 9V battery



  • Humidity: 0 to 100% RH
  • Temperature (internal): -4 to 199°F
  • Accuracy: ±2%RH
  • Max. Resolution: 0.1%RH
  • Dewpoint: -22 to 199°F
  • Wet Bulb: 32 to 176 °F
  • Absolute Humidity: 0 to 1120GPP
  • Dimensions: 7.8" x 1.7" x 1.3"
  • Weight: 7 oz


More Information
Thermo-Hygrometer RH Accuracy +/- 2%
Brand Extech
Thermo-Hygrometer Temp Accuracy ± 1.8°F
Thermo-Hygrometer Temp Range -22° to 199°F
Thermo-Hygrometer Calculations Dew Point, GPP, Rh, Temp, Wet Bulb
Thermo-Hygrometer Temp Accuracy ± 1.8°F
Thermo-Hygrometer RH Range 0 to 100%
Category Thermo-Hygrometer
Warranty Information One (1) year from the date of purchase on parts and labor
Condition new
Manual / Schematic