Voltage Measuring Guide

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Note: usual disclaimer - Use of multimeter incorrectly can have severe health risks to you and/or your equipment. If unsure on what you’re doing - DON’T

Index

Post
2 - Multimeter
3 - Selecting Settings & Power on
4 - Using the Probes
5 - Measuring 12v
6 - Measuring 5V
7 - Measuring 3.3v
8 - Measuring Vcore (CPU Voltage)
9 - Measuring VDIMM (memory Voltage)

Motherboards Voltage Measurement Points:-
Asus P5K Deluxe Wifi
Asus Commando
Abit IX38 QuadGT
DFI X38/X48 Voltage Measuring Points.
DFI UT X48-T3RS Voltage Measuring Points
Gigabyte GA-X48T-DQ6

If you see or have measuring point pictures of other motherboards please let me know & i'll add them to the guide. Hopefully we can build up a library that will help people.

Thanks.

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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

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The dial is used to select function & voltage range. Do this with multimeter power off.
Here mine is set in the DC Voltage segment (denoted by the V symbol with the dots & bar above it Obvious)
The setting selected on the dial of 20 is good to measure DC voltages from 2v~20v (the majority of readings)
For voltages <2 select 2 use this for Vcore.

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PC Power Leads
Your power supply leads are colour coded as:-
Yellow = 12v
Black = Ground/Earth
Red = V
Orange = 3.V

To measure any voltage place the black probe on the ground cable.
the probe plugs into a spare molex cable.

I generally plug this in as shown and leave it there during tests. Some people say you get more accurate motherboard readings by earthing to the mobo. This may be true but I've measured both ways and seen no real difference. This might vary with the quality of the power supply so I'll keep an open mind.

It is though, far safer to have the earth probe in the molex, leaving you to just focus on where you place the red lead. So if your just starting I'd use this method , until you feel confident using the probes.

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Power on multimeter.
Place red probe in 12v point on molex.


Check meter reading

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Power on multimeter.
Place red probe in 5v point on molex.


Check meter reading

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Measuring 3.3v is different to 5v & 12v as there is no 3.3v lead on a molex connection.
Depending on your power supply you may have two ways to measure:-

1) Sata Lead
The underside of some leads gives access to the 3.3v (orange ) touch the exposed metal connection on the orange lead
with the red multimeter probe.

2) 24pin Mobo Lead
Which is the option i have with my psu
touch/push gently in the orange socket


Check reading , you should see something similar

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Note: Measuring the PSU power points are relatively easy. Measuring the voltage points on the motherboard is more dangerous, it being easy to slip with the probe and short out a chip or other component. So i wouldn't advise doing this when you've just come back from the pub

Change dial to 2 (as described in Selecting Settings & Power on)

Check the location of the Vcore reading point. Check the index to see if your board is listed. Then use the pictures as a guide,

Place probe on measuring point


Read meter


Note:most of the readings we do are best done twice:-
1) With PC running idle.
2) With PC running load. - I usually run prime or similar benchmark for test.

In the case of Vcore the difference between the 2 readings is known as vdroop.

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Note: Measuring the PSU power points are relatively easy. Measuring the voltage points on the motherboard is more dangerous, it being easy to slip with the probe and short out a chip or other component. So don't do this if you have the shakes :lo5l:

Set meter dial to either 2 or 20 depending on your voltage (see Selecting Settings & Power on)
Check the location of the VDIMM reading point. Check the index to see if your board is listed. Then use the pictures as a guide,

Power on multimeter and carefully place the red probe on the VDIMM measuring point.


Check reading on meter

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Voltage Measuring Points - Asus P5K Deluxe Wifi


Copyright - GMX