question on using a multimeter

I am curious when we use multimeter to test the PSU, should we turn off the system before we put the probe into the power connector?

A mulimeter will only be able to measure current if the current is there. What are you trying to measure exactly?

You can connect it while it is on.

aphreman is correct.

power supply for the computer. I am just a bit worried when I have to use it to my mobo's connector, worry that if it will damage my system or not.

What exactly are you trying to measure?

the stability of the amps on the 12v, 3.3v, 5v. I know that I can use the 4pin molex for the 12,5v but not for 3.3v

It is hard to measure while plugged in.

You can jump the power supply to have it running while out of the computer and check it that way...

but that won't give me the load reading of the psu. I have seen people who did load reading on the psu, and wonder how they did these tests.

Said By SAMSAMHA

but that won't give me the load reading of the psu. I have seen people who did load reading on the psu, and wonder how they did these tests.

You can get power supply testers from most pc places. They have a connecter that goes between the connector on the psu and the mobo/hdd/cdrom/whatever to test things under load. I'm sure you can imagine how to make a pass-through connector thing on your own. Be careful!

Buy a new power supply.

got an multimeter, they are quite easy to use. I think all computer builder should get one.