Product review (4 stars): Nice, But...
When working on HVAC I need to know wet bulb temp.  This calculates it for me.  I misplaced the one I had so I bought another, then found my original.  As you can see, they don't both agree.  They were both left on long enough in the picture to have an accurate reading. I still like them, just wish I knew for sure what the numbers should be.