Thermistor for heatbed shows +100 degrees while at room temperature

Hello,

I've ugpraded my printer with a heated bed and I'm using the Rumba board. Now the thermistor for HB is the following: NTC resistor, pearl 5 kOhm, B57540G0502F000, EPCOS.
When i measure the resistance when the thermistor is not pluged it ishows something around 5kOhm when at room temperature, but when i plug it in in Rumba's THB pins, then the resistance is somewhat around -12kOhm. The result is, that Pronterface shows me +110 degrees celcius for the heated bed.
Why is that, and how can i fix it?

If you measure it plugged, you will read the resistance of the whole circuit and not just the thermistor that's why the difference in readings. Did you selected the correct thermistor in the firmware? I usually use 100k thermistors and I don't know if a 5k is in the options? If not you might still be able to use it but will have to create a new table for it.

Edited 1 time(s). Last edit at 06/11/2016 12:46PM by ggherbaz.

Get a better air conditioner. The one you have is letting your room get too hot.

Did you change the thermistor type in the firmware?

Well i found this here: [www.thingiverse.com] to generate the temperature table. I entered in all the Values from the thermistors data sheet and generated the Table.
But now i get the error MAX temperature reached. So something still seems to be off.

I usually verify my thermistors this way:

With a multimeter measure the resistance with a block of ice 0 centigrade and with boiling water 100 centigrade depending on altitude, then measure it at ambient and with those 3 readings you can create the table, it will be the closest to actual values.

Well, stupid mistake. The calculated thermistor table was correct but i forgot to add progmem before the table object as it was with all the others. Now it's workin fine.