Hi everyone,

first off, hello to all the experts on this forum, I'm pretty new to the topic and also new on the forum.

Here's my question/problem:

I just (almost) finished building my first 3d printer from scratch and I'm having trouble with the Marlin temp readings of the board (MKS Gen L).

When I plug the board on USB only (4,65 V), the reading at room temp is only 2-3 degrees off, but as soon as I power the board from an external supply with 4,93V, the readings are 34 degrees, when it's actually 21 degrees in the room.
It doesn't seem to matter which thermistor table I'm using, all behave the same way.

How does Marlin calculate the temp? Do they assume there's exactly 5V as a reference voltage? Can I adjust that in the code? Apart from that constant voltage error, table 13 seems to be OK for my thermistor (3950 1% China stuff).

Thanks in advance!
Pete

I forgot: When I heat up to >100 degrees C the readings are a lot closer to the actual temp (as far as I can measure).

Marlin uses look up tables so setting the correct thermistor type is essential

Most do have inaccurate lower temperature readings... 2-3 degrees , 13 degrees is not right...

type 11 should be you thermistor

Hi Dust,

thanks for your reply. I know that already, but no matter which one I choose, the temperature is way off when cold. As soon as I power with 4,6V (USB only) it's fine, however...

Any other ideas? So far I helped myself modifying the thermistor table to almost match my needs. But that can't really be the root of the problem?!

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screenflow
Hi Dust,

thanks for your reply. I know that already, but no matter which one I choose, the temperature is way off when cold. As soon as I power with 4,6V (USB only) it's fine, however...

Any other ideas? So far I helped myself modifying the thermistor table to almost match my needs. But that can't really be the root of the problem?!

The clue to the answer is in your own text.

Edited 1 time(s). Last edit at 01/13/2019 04:58AM by MKSA.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

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MKSA
The clue to the answer is in your own text.

I don't get it, please point me at it. Are you talking about the modificaton of the table? Is that really the desired solution?