Ripple voltage measurment

Hi all,

I need to measure the Ripple volatage of the AC to DC adaptor. How can i do that using the Logic analyzer. Vpk-pk Voltgae gives the Ripple voltage of the power adaptor right. but in the test setup the power adpator is connected with 100uF and

0.1uF in parllel to power adaptor pin and the power adaptor is connected to the load. Why we need to connect the parllel capacitors in oreder to check the ripple voltage for the power adaptor

Thanks kil