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  • Dual backlit display
  • Simultaneous display of: humidity/temperature; humidity/dew point; humidity/wet bulb
  • Data hold and Min/Max functions

What's in the Box

  • Carrying case
  • 9V battery


The precision Extech RH390 psychrometer measures humidity, air temperature, dew point, and web bulb temperature. Highly accurate (±2% of RH readings, ±1.8°F for temperature readings) and with high resolution (0.1% RH, 0.1°F), the Extech RH390 psychrometer also gives users a wide measurement range: 0 to 100% for relative humidity, -22 to 199°F for dew point, 32 to 176°F for wet bulb, and -4 to 199°F for temperature.

The Extech RH390 psychrometer features a response time of under 30 seconds and simultaneously shows humidity and one other parameter (temperature, wet bulb or dew point) on the dual backlit LCD display. The Extech RH390 psychrometer also features data hold and min/max functions along with auto off (with disable function) and a low battery indicator. The Extech RH390 psychrometer has a slim design with rubberized sides for a better grip that facilitates one-hand operation.

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