It's been asked, so I thought do a real quick read on the difference:



Taking a wet bulb temperature measurement directly requires a “wick”.  The original purpose of wet bulb temperature measurements was to calculate relative humidity.  People would measure both wet bulb and dry bulb, and then look up the relative humidity based on altitude charts.


With the advent of humidity sensors, wet bulb temp isn’t really useful for most people.  Some industries still use the measurement because their charts are based on wet bulb.  We calculate wet bulb in the K3500 and K4000 series based on humidity, dry bulb temp, and pressure measurements.  Hence, no wick.



This is based on an equation that uses a combination of environmental elements to calculate the reading. The calculation is a measure of the heat stress in direct sunlight, which takes into account: temperature, humidity, wind speed, sun angle and cloud cover (solar radiation).