Should I write a new thermistor table?


#1

Currently according to my Thermal couple testing of the hotend,. I am ~8c low from what the setting for the temp should be.

I have checked the thermistor at 25c and it’s very close within 1kohm of being 100k very hard to get the temp sampled exactly as there is thermal lag etc. but I think it’s very close to right.

This it seems to me can be either the voltage divider that the ADC is sampling is off or the reference voltage is off.

So as all the components are all SMD and no pots for adjustment are involved. I was thinking I could write a new table for my setup so the values track closer to true.

The low temp has caused me a problem or 3 as several times I’ve had to lay on hands to warm up the hotbed and hotend to a temp that is greater than 5c

I did the PID autotune and was surprised at how much tighter the temperature control is.
I accept I can be 3-5 degrees off but 8c is out of spec and it could be better with a little fiddling.
I did see that I could try some other thermistor types settings in the firmware, but using the device 5 thermistor seems like a good template to tweak.

Has anyone else been fussing with the temps?

Thanks for comments.

Remo


#2

So Thermistor tables are not too bad to tweak, but do take time.
I’m pretty sure it’s the voltage divider on the Pica board that had my temps off.
After 2 hours of fiddling about my temp sensor tracks within 2c of the desired temp!

I used 2 type K thermal couples, snugged under the E3D sock against the bottom of the hotend,
using some aluminum foil to reflect the heat back and a dry bit of cloth to provide pressure to the sock and hold the thermal couples against the heat block.

Leaton Digital Thermometer

As my reference.