General Tools EP8710 Calibratable Multi-Function Digital Psychrometer, Wet Bulb Capable with Probe Measure temperature, relative humidity, dew point, wet bulb temperature and other moisture parameters; probe measures internal and surface temperature Features a jumbo backlit display with triple readout; minimum and maximum temperature button and data hold button on device as well This device is field calibratable using optional 33% and 75% salts; toggle between Fahrenheit or Celsius with switch Monitor battery life with low battery indicator; psychomotor an Auto Power Off saving your battery when not in use ( can be disabled for calibration) 9V battery included; limited 1-year warranty