Displayed temperature drops to -15 when reaching 300°C

Hi all,

I made an high temperature test with my all-metal hotend to test my thermal fuse.
Firmware maximum temperature was set to 330°C (Marlin 1.1.9, which is self compiled).
Exactly when I reached 300°C the displayed temperature droped to -15°C (same temperature as if no sensor is connected) and the heating fails therefore after some time.
Because when the temperature drops to 299°C again everything works fine and the NTC-sensor works fine afterwards, I think it's a firmware related problem.

Has anyone went over the same problems or does know how to fix this problem?

Best regards,
Florian

... such problems generally occur, when the measured/recieved data exceed the defined variable type "size" - so either bigger variable type, or reducing (eg. remapping) the measured value ...

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Viktor
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Thank you for your answer!

That would explain that behaviour...
But most of the boards have an voltage divider with 4k7 Ohms to 5V and the NTC has about 75 Ohms so the measured voltage would be about 78mV.
The raw value variable is 16 bit integer so I don't think an under- or overflow happens and the real temperature value is stored in an float variable...

I can't imagine what the problem is...

Edited 1 time(s). Last edit at 09/01/2019 01:23PM by flo94.

... so maybe the conversion and calculation to output the degrees value?

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Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]