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Extech RH25: Heat Index Psychrometer

Compact indoor/outdoor meter for measuring up to 6 environmental parameters

Extech’s pocket-sized Heat Index Psychrometer Pen easily monitors Heat Index during hot humid days to prevent heat stroke during outdoor activities, sporting events or, indoor workplace. Its pen-sized design makes it convenient to fit into your pocket and carry it wherever you go. Complete with CR2032 battery.

CE1 Year Warranty


  • Built-in multiparameter sensor measures Heat Index, Wet Bulb Globe Temperature (WBGT), Humidity, Ambient Temperature, Temperature, Dew Point and Wet Bulb
  • User Programmable Heat Index/WBGT alarm
  • MIn/Max/Average
  • Data Hold, Auto Power Off with disable
  • Complete with CR2032 battery


Specifications Ranges Resolution Basic Accuracy
Temperature -4 to 122°F (-20 to 50°C) 0.1°F/C ±1°F/0.6°C
Relative Humidity 0 to 99.9%RH 0.1%RH ±3%RH
Wet Bulb -4 to 122°F (-20 to 50°C) 0.1°F/°C
Dew Point -108.4 to 122°F (-78 to 50°C) 0.1°F/°C
Heat Index -50.8 to 401°F (-46 to 205°C) 0.1°F/°C
WBGT -13 to 130°F (-25 to 54.5°C) 0.1°F/°C
DImensions 5.5×1.4×0.7″ (140x35x18mm)
Weight 1.8oz (50g)