The 445580 is a compact, portable RH/Temperature Pen designed for field measurement of relative humidity and temperature. It features a dual LCD display that simultaneously shows temperature in °C or °F and relative humidity percentage, with built-in temperature and humidity sensors for convenient operation. The device includes Max/Min memory functions for both parameters, a Data Hold function to freeze the display, built-in self-calibration utility with optional RH calibration bottles, and operates on a single 3V lithium battery. With its pocket clip design and rugged construction, the 445580 is ideal for HVAC technicians, environmental monitoring, laboratory work, and any field application requiring quick, accurate humidity and temperature assessment.