The HL-20D HygroLog Temperature & Humidity Logger has an outstanding accuracy at 0.8%rh and 0.2AC. It offers long term stability with a 20000 data point memory with date and time stamps. Alarm limits are programmable and Psychometric calculations of Dew and frost point values are available.
It has a UART to USB interface allowing connection to PC. This allows the user to view the values stored on the device using the HW4 software which is supplied with all hires. The HL-20D also has a long battery life.