I have calibrated the heat bed thermister.  I have determined it measures 8 deg low at 80 deg C.  If i want the bed to be 80 deg C, I have to set the bed temperature to 88 deg C.    Knowing the calibration results and thermister error, does not help me tell the Prusa the sensor is wrong.  

Given the importance of temperature for both the heat bed and the extruder, I believe the firmware should allow a user to calibrate the thermisters.  

The work around is to change the settings in the profile, but this is a work around and not a solution.  There should be a process to calibrate the temperature sensors.  

I have replaced my heat bed thermister but now the bed temperature is 20 degrees C less than indicated on the LCD panel.   I measured the room temp resistance at 127k ohm. It is supposed to be 100k ohm. That is about the same % error I am seeing in the temperature.     

Is there a way of manually adjusting the thermister room temp resistance in the software?  

Doing a calibration from the LCD does not fix the problem that the thermister is indicating the temperature about 20% higher than it really is, so the bed is cold.

I figure there is somewhere in the software that sets the room temperature thermister resistance at 100k.  I want to change that to about 127k.