Alternators and Output Amps

Guys, I have a 99 yukon denali. what is the output amperage of my alternator? is there a way I can measure it at idle?

Here are the RPO codes of the alternators available for your truck (I believe these are correct).

RPO - Rated Amps
K60 100 A
K68 105 A
Alternator model: CS130D

KW2 124 A
KG9 140 A
Alternator model: CS144

or if u want Snap-on makes an awsome D-Tac plus that u hook up to the batterys and it will messure it all for u, just put the amp prob on ur lines and it will tell u if ur starters bad, bad batterys, or if the diodes are bad