I have 2 temperature/humidity guages in my workshop but they never agree with each other. Obviously at least one of them is grossly inaccurate. Maybe both of them are. What I've been doing is just going with a value that's between the 2 numbers and calling it good enough. Maybe I should splurge on an expensive instrument that's more acurate and properly calibrated. This picture is typical of how they read. Often, they're off by even more than this. The difference in temperature is 2.2 F The difference in humidity is 5 percentage points.