Geeetech

I have a Prusa I3 Pro B printer.

If I measure the temperature of the hotend with a separate thermometer.
Actually a multimeter with a temp sensor.
The external measurement consistently report a 30 - 40 degrees higher temp
than what the Marlin firmware reports.

What temperature sensor type is the correct one for a Mk8 extruder/hotend ?
I can't find any documentation on what sensor is supplied with the Mk8 extruder...

Everything indicates that the extruder is working at a much higher temp than it should.
Including the extruder "base" bending due to high temperature.

I have tried several 100K sensors but I can't see any difference ?

Please let me know what the correct setting should be.
Regards

So the only problem is that the actual temperature is higher than the temperature reading from LCD?

Yes.
But Repetier host also "see's" the incorrect temperature and Marlin acts according to it.
That is, If I set a extruder temp of 240 C, the actual temp being used is around 260-275 C.

The odd thing is that the heated bed reports the correct temp....

You can change it in "thermistortable.h".

My problem is that I don't know what type of thermistor is actually in the hotend, so I dont know what the data are to enter ?
If you could provide the identity / type of thermistor mounted, I can easily enter the values.

Is this information in "Configuration.h" useful for you?
"
1 is 100k thermistor - best choice for EPCOS 100k (4.7k pullup)
"

Thank you
That exactly what I needed to know.