# Does Ground Voltage Need Lowered As Well?

I am dividing voltage of a 9V battery to 3V for a Rasperry Pi GPIO. I have the ground connected to the end of the resistors, so it is back to 9V when I connect it to the Pi's ground pin. Is it ok to have the ground at 9V?

simulate this circuit – Schematic created using CircuitLab

• By definition, "Ground" is zero volts. Draw a diagram to show us exactly how you have connected and measured things. This site has a nice schematic editor you can access by hitting "Control-M". Feb 17, 2015 at 5:24
• First time ever drawing a diagram. Let me know if it makes no sense.
– rys
Feb 17, 2015 at 5:39
• I think I did that wrong. Is that really 3V there or not? I kind of guessed that 3 resistors divides 9V by 3. I was using a multimeter and testing between source power and between each resistor. Is that the right way to measure it? So 3V after first, 6V after second, all 9V after all 3 resistors?
– rys
Feb 17, 2015 at 5:50
• to get 3v, you should take voltage across R3. @rys Feb 17, 2015 at 5:57
• I hope you are using this 3V just to connect to a GPIO (to indicate that the abttery is present??), not to power the RaPi. Feb 17, 2015 at 8:12