INA219B reading vs UT61E as it warms up

[Rick Law]

I've been doing some temperature vs shunt reading deciding if I would upgrade my shunt to one with better temp-co for my B3603 DC-DC buck board.

With the stuff all set up, out of curiosity, I did a graph to see how the Adafruit INA219's shunt reacts under the same circumstances as the shunt warms up by current and cools back down by a fan.



- Cooling is done by have a PC case-fan 2.5 inch blow over the PSU (and the INA219).
- Fan cycle is 8 minutes ON (cool down), 35 minutes off (warm up)
- Temperature is not temperature of the shunt but air-temperature near the PSU shunt.
- Temperature is measured by an LM35z.
- UT61E serves as the bench mark, set at the 10A range, connected in series with 2ohm 10watt
- Current is set to desired (around 1.6A) by setting the PSU voltage at the start of the run
- An empty cycle (i.e. not logged cycle) was ran before data log begin
- Room has air vent, house heat (and night cooling) is the only expected disruption to air temperature

I expected the INA219B reading to change as the current warms the shunt and as the fan cools it back down.  The INA219B resisted change and tracks the UT61E's amp measurement a lot better than I expected!

Thought you may find this data interesting.

Rick