The Extech EA20-NIST is a Hygro-Thermometer that measures Relative Humidity, Temperature, Dew Point, and Wet Bulb and displays any two parameters (Temperature and Humidity or Dew Point, or Wet Bulb) simultaneously. Min/Max function stores and recalls highest and lowest readings. Timer function displays the elapsed time (mins : secs and day : hour). Additional features include: programmable auto power off time frame, switchable °C/°F temperature units, Data Hold, Auto power off, and Low battery and over-range indication. With NIST Calibration.