The only difference I can find between the A and AX models is the specified operating temperature range. However, is the difference only due to the fact that the AX comes with and uses AA lithium batteries (which happen to operate over a wider range), or are there also differences in the internal circuitry/display and PCB? Said another way, if I use lithium batteries in the A model (which I normally do anyway to avoid leakage), do I effectively have an AX? I’m trying to confirm whether it’s the batteries themselves that allow the unit to operate over a wider temperature range. Thank you.