A technical note from Weller on how accurate your soldering tool reading are. Link here (PDF!)
With so many technological advancements, there is no excuse for incorrect measurement readings. For example, your automobile has a number of alternative methods to check the accuracy of the speedometer. You rely on those indicators to be accurate. If they’re not, major problems can result.
Consider this question: Do you trust the accuracy of your soldering station temperature readings the same as you do your car’s speedometer?