Product review (5 stars): Must have piece of test equipment for HVAC technicians in ...
Must have piece of test equipment for HVAC technicians in order to ensure proper refrigerant charge.  Wet Bulb of air at evaporator and Dry Bulb at the condenser are needed to properly calculate the correct charge for a system.  This tool has helped me to optimize the charge in rental property AC systems that I manage.  The tool is incredibly simple and intuitive to use and so far has not given me any issues in terms of quality.  Hopefully this will last me a long time.  And being such a necessary tool of the trade it is quite reasonable priced relative to the cost of other tools.  I have not calibrated the unit to a traceable standard but when I take my Dry Bulb readings I have a rough idea of the temperature from the weather forecast and this device seems to track what I believe the actual temp to be.