I have a lot of thermistor to read and I am thinking using the internal pull-up resistor so i can connect directly the thermistor to the pin and the ground. So i don't need to connect a lot of 10k resistor, one for each thermistor.
On the Arduino Uno description page : http://arduino.cc/en/Main/ArduinoBoardUno It says that the internal pull-up resistor is of 20-50 kOhms.
Is it a variable resistor value ? Is there a way to know precisely the resistor value ?