I've just built a power adaptor from some old pins and a DC eliminator... Now how do i check if my adaptor is center positive. If i wire it up to supply and poke in the red probe of a multimeter into the center and the black probe on the outer ring, it shows a positive reading... so is this center positive power adaptor? :-[
Yes. 
Assuming you have connect the red lead to positive. 
oops mike... u confused me... I dont remember how i connected it when i bought my multimeter! silly but i'm really confused... how do i check this now? i'm building a communication project with 2 arduinos and bady need additional power for 1 of it and so much work and i'm all confused! :-/
ok checked that its ok.... Thanks a lot!