heater: 5 sec stabilization time after switching to closed loop

[rusefillc]

LSU4.2 falls to Underheated state right after switch to closed loop due to rise of sensorEsr (due to applied pump current?)

[mck1117]

have a log?

[dron0gus]

Or maybe this is caused by rapidly increased heater PWM? Unlikely.
Issue can also be solve by using hysteresis for underheatESR thresholds.

lsu42_heating.zip

[mck1117]

That’s pretty strange. It makes me question the accuracy of the ESR measurement…

[mck1117]

What happens if you postpone activating the pump until the sensor is fully warm?

[dron0gus]

I'll do some testing later.

[dron0gus]

Pump control enabled only after sensor reaches targetESR

lsu42_heating_mod.zip

[dron0gus]

Looks like Nernst voltage is too low and AC component is clamped. This gives us lower ESR than actually it is.
When we start feeding pump with some current Nernst voltage get some shift from zero and AC component is measured correctly. This cause ESR rise/calculated temperature drop.
On dial rev1 I have added 0.3V shift to x3 Nernst voltage. Waiting for new HW to check if this helps.

[dron0gus]

Yep, this is clamped Nernst.

[mck1117]

seems like at least worth a comment explaining that finding

[dron0gus]

But this is with
2023-04-16_13.21.46-rev1-warmup.zip
4.9. Needs additional testing with 4.2.

[dron0gus]

[mck1117]

So it seems the same bump up in ESR is still there on 4.9, but not as severe, so it doesn't trip underheat.

[rusefillc]

Just rebased this one

@mck1117 @dron0gus are you guys more or less in agreement about this change? @dron0gus can you add additional code comments into this branch? @mck1117 any chance you would be able to merge and add desired code comments?

[rusefillc]

@mck1117 this was rebased please revisit this PR (fails same as master, will rebase on master when master gets green)