Product review (1 stars): Junk.
I purchased this to do some testing around my house as we tweak our HVAC/dehumidification system. Not only was this device wildly inaccurate, but it was also completely inconsistent, even after calibration with the required and expensive calibration kit. I returned the whole mess, and instead opted for a few AcuRite sensor kits for continuous and far more accurate measurement and logging.