Incubation: egg temperature vs air temperature

[J.P.]

I have the thermostat probe tucked between the eggs themselves.

this.

and choose which device to trust. the variance in temperature could be caused by an error in calibration. in choosing thermometers, i use an old school but high quality analog thermometer as reference. i only trust digital thermmos that read to within a half degree of the reference....i still use those that fail my test, but i add or deduct the noted variance to get actual temps.