@bewaren the sharp dips suggest to me that you have an intermittent connection in the wiring between the thermistor and the Duet. This is most likely caused by a bad crimp connection at one end of the cable between the Duet and the Smart Effector. But I suggest you also check that the soldering of the 8-way connector on the Smart Effector looks OK, in particular that all the pins have been soldered. That connector is hand-soldered so mistakes are possible. Likewise, check the soldering of the 2-pin temperature sensor connector on the Smart Effector.

Problem isolated to thermistor, not Duet.
#ISSUE CLOSED

@deez3443 said in Two thermisor on chamber and limited heater:

Do you have any idea how to use autotune correctly in this system? At best, I will set it up manually.

Given a 300W chamber heater, I had no luck with autotuning. Temperature rise was simply too slow. In the end, I figured out parameters that gave me just some rare heater warnings - they indicate, at least, proximity to a proper model of the heating process.

Finally, I enhanced the fault tolerance with M570 H3 P300 T25, as my heated chamber is (due to the weak heater) quite an inert system. However, you might wish to use other parameter values.

@wurth51 if you get a short between Vssa and a higher voltage then you should get a message on the DWC console warning you of the short.

@dc42 this is the problem, thank you. I will try to repair it

@schild0r, on Duet 3 MB6HC the un-calibrated errors can be quite large. Typically, TEMP0, TEMP1 and TEMP2 have significant error at low temperatures only, and different TEMP3 has significant error at high temperatures only.

Thank you Droftarts, you save my day...
My duet maesto was not working with the good firmware.

@Phaedrux said in M305 Thermistor Values for the Duet 2 WiFI on the Ender 3 Pro?:

Try M305 P0/P1 T100000 B3950 and see if it matches more closely to the previous temp tower performance.

@Phaedrux, thanks! That seems to work better and align with what would be acceptable temperatures.

I finally solved my mystery of weird noisy hot-end thermistor readings!
The problem goes back to even https://forum.duet3d.com/topic/5582/hot-end-auto-tuning-failed-due/1 which is also solved now!

When I built my printer and my XY carriage I tried to be clever and reduce the number of wires I need to run through my drag chain by combining all ground / power / etc connections as much as possible.

I wrongly assumed that VSSA can be substituted with GND. I essentially plugged my thermistor into GND+THERMISTOR1. This gave me a "good enough" reading apparently that I never bothered to double check. 🤦

This however creates a few tiny problems because @dc42 is even more clever and compensates for the extra fuse resistance of VSSA in the firmware - which means I have a wrong reading in certain cases.

Now I'm running my thermistor wiring the way god @dc42 intended, and I have a super clean temperature reading!

Let this be a lesson guys! RTFM!

@LostJen No need to apologise! Easy mistake to make. Just needed to work out if there was anything needing changing our end.

Ian

@hamiltonprops From re- reading your OP, you say that the temperature drops 20 degrees within a second or two. That would indicate it's not a "real" drop in temperature but rather a drop in the indicated (measured) temperature - unless your hot end has an insanely low thermal mass. So, yes I go for some sort of cross talk or electrical "noise". Are you sure you haven't got a bad crimp on the thermistor wiring somewhere?

@3mm I bet it even acts as a desiccant! Brilliant.