Value of an sensitive Analogsensor changes heavy with other power sup. than USB

Hi,

the docs say that the middle pin is inactive.

Nevertheless I tried it, left pin 5V, middle pin analogpin, right pin GND with resistor.

With 1 MOHM 1 get no load: 1,9 V max load: 4,3V

With 100 KOHM no load: 1,9V max load: 3,4 V

Without resistor no load 1,9V max load: 1,9V

Are these better results?

The value is changing about 5 % all the time without any change in weight, but I think this is normal for such a sensitive resistor?

Do you think everything is ok now?

With which resistance I may get the best results?

Many many thanks for your help.

Ralf