hygrometer question...

[Arrow111]

ive calibrated all 6 of my hygrometers. they are reading differently respective from each other but ive marked them with +/- calibrations to correct for the differences.

however, ive placed them in various indoor and outdoor locations and they are all reading several %'s off from their respective calibrations. ideally, i should be able to apply the +/- calibrations under different conditions to tare their rh's. but it seems differences are exacerbated as humidity goes further away from 75.

how can i determine which one/s are truly accurate?

[acarr]

Are they digital? If not that would be your first step.

[TripleF]

If they are located in different locations you might get different levels of humidity. Just a thought..

[Arrow111]

all digital.. 2 hygrosets, 2 accurite, and 2 of another..

i placed them all together in different locations and took the readings as a batch..