Extech Precision Hygro-Thermometer Psychrometer – RH390

In stock

This precision meter measures temperature, humidity and dew point with a very high resolution of 2 percent relative humidity. With the ability to display 2 values at once and a 30 second test time.

Extech Precision Hygro-Thermometer Psychrometer – RH390

Highest 2% RH accuracy with a fast 30 second response time


  • Dual backlit display
  • Simultaneous display of:
    • Humidity/Temperature
    • Humidity/Dew Point
    • Humidity/Wet Bulb
  • Fast 30 second response time
  • Data Hold and Min/Max functions
  • Auto power off with disable and low battery indicator
  • Slim design with rubberized sides for better grip and for one handed operation
  • Comes complete with carrying case and a 9V battery
  • 1 year warranty

This hygro-thermometer psychrometer is a highly accurate way to measure temperature, relative humidity and the dew point. With a very high 2% RH accuracy with a fast 30 second response time. This meter also has wet bulb measurements to help determine the relative humidity and dew point. This kit has everything needed to start testing immediately.

Applications for this meter include monitoring temperature and humidity in greenhouses, warehouses, saunas, museums, storage areas and regular houses. Humidity is very important for living spaces due to its ability to cause skin damage when too low and promote mildew or dust mite growth when too high. The RH390 Precision Hygro-Thermometer Psychrometer Kit User Manual is attached to this page to answer any further questions.


  • Humidity: 0 to 100%RH
  • Temperature (Internal): -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
  • Dew point: -22 to 199°F (-30 to 100°C)
  • Wet Bulb: 32 to 176 °F (0 to 80°C)
  • Dimensions: 7.8x1.7x1.3" (200x45x33mm)
  • Weight: 7oz (200g)

Unit Ship Weight: 1 lb

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