Extech RH305
Digital Hygro-Thermometer Psychrometer Kit

  • Includes a RH300 with 33% and 75% calibration bottles, PC cable, and case
  • Simultaneous display of %RH, Temperature and Dew point or Wet Bulb or Probe Temperature
  • Wet bulb measurements without slinging
  • Calculates T1-T2 differential (Air Temperature minus External Probe Temperature) using probe (TP890) and T2-Dew Point
  • Unique sensor cap design twists to closed position for protection during storage
  • Switchable °F/°C temperature units with 0.1° resolution
  • Data Hold freezes current reading on display
  • Max/Min readings
  • Auto power off to save battery life
  • Available as a standalone product - Extech RH300
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Extech RH305 Shown
Product Information
Datasheet 339 KB
Manual 571 KB
PDF Help
Humidity Range and Resolution 0.0 to 100.0% RH
Accuracy ±3% RH (10 to 90%) @ 23°C
Temperature (internal) Range and Resolution -20 to 50°C (-4.0 to 122.0°F)
Accuracy ±1°C (±1.8°F)
Temperature (external) Range and Resolution -20 to 70°C (-4.0 to 158.0°F)
Accuracy ±1°C (±1.8°F)
Display Triple LCD
Sensor Type Humidity: Precision capacitance sensor
Temperature: Thermistor
Response Time 60 seconds typical
Dew Point -90.4 to 122.0°F (-68 to 50°C) (calculated from RH and Air temperature
Wet Bulb -6.88 to 122.0°F (-21.6 to 50°C) (calculated from RH and Air
temperature measurements)
Operating Conditions -20 to 50oC (-4 to 122°F); < 99% RH non-condensing
Battery Life Approx. 80 hours
Ordering Information
Model Description Buy Online Price
RH305 Extech RH305 Digital Psychrometer Kit Buy Now Sale $106.49
(Reg. $149.99)
RH305-NIST Extech RH305-NIST Digital Psychrometer Kit with NIST Buy Now $274.99
Optional Configurations
RH300 Extech RH300 Digital Psychrometer Buy Now Sale $74.99
(Reg. $99.99)
RH300-NIST Extech RH300-NIST Digital Psychrometer with NIST Buy Now $220.99
Kit Includes
  • 2 - AAA batteries
  • 1 - RH300 Digital Hygro-Thermometer Psychrometer
  • 1 - Temperature probe
  • 1 - 33% calibration bottle
  • 1 - 75% calibration bottle
  • 1 - Carrying case
Optional Accessories
TP890 Extech TP890 Thermistor Probe -4 to 158 Degrees F For Model RH300 Hygro-Thermometer Psychrometer Buy Now Sale $10.87
(Reg. $15.99)
RH300-CAL Extech RH300-CAL, Humidity Solution Kit, 33% and 75% Buy Now Sale $43.79
(Reg. $59.99)

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