From time to time we get concerned about voltages, usually after some things crashed, blown or not working.
I got a multimeter originally to check my
VDIMM on the old
DFI NF4Ultra boards, it tended to over volt so I wanted to know by how much. This let me run my memory as I wanted, if
VDIMM was over recommended
ddr voltage it was because I wanted it

I also used it to
Calibrate MBM Volts to Multimeter
Testing is more meaningful if done twice:-
1) PC running idle
2) PC fully loaded, usually use Prime or other benching tool.
Ideally with all the voltages we measure we want to see 2 things
1) Voltage as close to spec or
bios settings.
2) Difference between Idle and Fully loaded is small
You need a multimeter prices vary with quality
Maplins Multimeter The one I have was about £28
1) Multimeter
Note: refer to the manual of your own unit to select the right settings.
UNI-T UT58 Multimeter
Probes - Black = Earth/Ground Red = Live

Dial is used to select Function & Signal range