Did anyone else notice that turning the bluetooth on causes the meter to cool by more than half a degree C and turning it back off causes it to heat back up to previous half a degree higher temperature?
I can confirm this happens on my 121GW. Drops about 0.6C within a few seconds when BT is turned on, and rises again very quickly after it is turned off.
The thermistor NTC1 which I presume is used for temperature sensing is at top right of the PCB (looking from the back) and BT module at top left.
I hooked up some fine wires so I could monitor B+, VDD (3.6V), and VDD_P (3.3V) with the case closed. The thermistor is part of a voltage divider on VDD.
VDD and VDD_P do not really change when BT is enabled, but I do see a small drop on B+ due to the extra load.
VREF+ on the STM32 connects to VDDA which connects to VDD_P. No idea... maybe a firmware issue with code trying to correct for something no longer relevant?