Polarity of dell inspron 9100 ac adapter

[gurunathan]

hi guys will anyone help me to identify the polarities of my dell inspiron 9100 ac apapter output barrel pin let me know any diagram for this bcoz i am getting two different voltages while i keep the outer sleeve of the barrel pin as comman i it seems that the inner needle like pin is giving -12 volts and the inner sleeve is giving -19.5 volts is it right please assit me

 

[frozenlead]

Voltage is relative - you can get two different readings depending on what you're using as ground.

If your connector has a center post inside of it, connect your positive lead of your multimeter to that, and the ground lead to the outside of the connector. If your connector does not have a center post, just put your positive lead inside of the connector, and the ground on the outside.

Why do you need to know this, anyway?