Are AT testers required to be in a climate controlled area to function to their intended specifications?
The accuracy of the AT3600 is guaranteed over a temperature range of 23 degrees +/- 5 degrees.
It is most common for the transformer's environmental characteristics to dominate performance changes over temperature rather than performance changes due to the AT tester.
For example please note the following transformer material characteristics:
1. The temp co. of copper is 0.00393 per deg C - or 4% in 10 degrees.
2. The initial permeability of ferrites varies wildly and non-linearly with temperature. The Siemens N27 (which used to be the industry standard for power transformers) permeability varies by 0.025 per deg C around 20 deg C - or 25% in 10 degrees! Permeability is directly proportional to inductance for U-gapped cores.
Limits for DCR should be no tighter than +/- 10%. 20% is common. (1mm wire can be +/- 6.5% tolerance of R on the reel, even BEFORE the degrading effects of stretching, temp and termination).
Limits for L can be a few % for gapped ferrite cores, but +/-25% is common for un-gapped ferrites.