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Extech RH490
Precision Hygro-Thermometer

Highest 2% RH accuracy with Grains Per Pound (GPP) and Grams per Kilogram (g/kg) Display

  • Less Than 30 Second 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
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Extech RH490 Shown
Product Information
Datasheet 155 KB PDF
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Humidity 0 to 100% RH
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)
Absolute Humidity 0 to 1120GPP (0 to 160g/kg)
Dimensions 7.81x1.7x1.3" (200x45x33mm)
Weight 7oz (200g)
Ordering Information
Model Description Buy Online Price
RH490 Extech RH490, Precision Hygro Thermometer Buy Now $359.99
RH490-NIST Extech RH490-NIST Precision Hygro-Thermometer with NIST calibration Buy Now $484.99
Included Accessories
  • 1 - Carrying case
  • 1 - 9V battery

*NOTE: Items ordered with optional NIST calibration will require
approximately 10 days to complete the certification.