How to use multimeter to check your voltages and rails!

[NGL_BrSH]

I am curious (always kills my cat) about how much Amperage my computer is using and also how many watts it using. I have a 700w Coolmax Greenpower which is supposedly 85% efficient or better (sure sure). I have a high-end Home theatre system plugged into the same circuit in the room as well as a fridge (!, I know.. i know.. but it's the only way to keep beer cold next to the couch) I've seen my home theatre draw as much as 7 amps before and i'm sure the fridge is uber unefficient.. (i don't pay the bill ) Now that I have my computer upgraded (see sig for details) I wanna know how close to the 15amp mark i am and how close to a firey death in my sleep i am


SO I have a fluke true rms 76 multimeter.. and i'd like to utilize this in order to figure these things out if i could.. but i read this thread which helpful as it may be.. not so helpful for my needs.

Multimeter: http://www.industrialelectronics.biz/fluke/248.htm

Can someone help? I took ME in college and i understand OHM's Law well.. but the real question is how to take the readings properly with my multi without causeing fire, death, and worse embarrassment.

Thanks!

 

[Lian Li]

I'm gonna bring mine home this weekend and test one of my rails cause my fan controller stopped working and i'm not sure if it's the controller thats the problem or the rail it was connected to.

 

[sreeja]

Yes it is truth.Digital multimeter gives more accurate readings.

 

[Jayws]

Awesome guide, thanks.

 

[SanDiegoPaul]

Here a good site if you are interested in getting a MM.

They have ones that range form low price ($8) and go all the way up to $200 (they are all digital MM). Another good thing is that they have chart on all them so you can see what you will be getting.

Thanks I was just going to post, asking where to buy. I got one from Radio Shack last year that only lasted six months. I think I used it four times. The analog one, that I was replacing at the time, was 35 years old

 

[EarthDog]

You are replying to someone that hasn't posted in thus thread in 10 months, fyi.

 

[Bobnova]

This needs a bump, even though it's a sticky.

 

[micjmac]

The DriverHeaven guide is a little misleading. I don't know much about electricity, but even I was skeptical about trusting the color of wire as being an indicator of the the line's voltage. Sure enough, my 24 pin does not follow this standard.

 

[Bobnova]

You sure about that?
I've yet to see a non-proprietary (dell, HP, etc.) unit that didn't either use all black wires or the proper color wires.
What colors do you have on the SATA connectors, in what order?

 

[micjmac]

Seems like the Molex conforms to the standard. Red, black, black, yellow from left to right.

I was using my mobo's manual to determine which pin had which voltage in the 24 pin. Maybe there was some kind of loss in translation there

 

[Bobnova]

Probably viewpoint looking at the connector.
The mobo manual will be looking at the mobo connector from the viewpoint of the cable connector.
The guide looks at the PSU connector from the viewpoint of the mobo connector.

The two viewpoints are mirrored in regards to each other. Makes things complicated

 

[wagex]

i like to use pin 16 (green wire) as a reference point

 

[micjmac]

Probably viewpoint looking at the connector.
The mobo manual will be looking at the mobo connector from the viewpoint of the cable connector.
The guide looks at the PSU connector from the viewpoint of the mobo connector.

The two viewpoints are mirrored in regards to each other. Makes things complicated

The mobo guide was arranging the pins how they appear on the mobo's connector. I somehow tricked myself into thinking the guide was arranging the pins as they appear on the PSU cable connector, so I was looking at the mirror opposite of where I should have been looking

Does it matter which 12V, 5V, 3.3V or ground wires that you pick?

 

[Bobnova]

Not at all.

 

[micjmac]

Just picked up a multimeter at Harbor Freight. All 3 rails were in spec.

5V rail was a constant 5.06V.

Is it alright if my 3.3V rail was jumping between 3.33 and 3.34 every second or two?

Also my 12V rail was jumping between 12.11 and 12.12 every several seconds. That alright?

 

[xsuperbgx]

What kind of tolerance should each of these have? 5%?
I have a customer psu that puts 12.5 to the 12V rails. It seems to work ok, I found their issue elsewhere. I will probably recommend considering replacement, since it is an apevia, and I am not a big fan.

(minor side note) Having a sticky that points me away to another forum sucks. I hereby assign to you,(YES YOU!!) that you write and publish a new guide along with pictures and video. So that your brilliance can forever be recognized,memorialized, and celebrated here in the "Power Supplies and Electronic Devices" subforum.

 

[Bobnova]

Officially, 5%. Those number are well within the ranges.

We do need a guide... maybe I'll make a frontpage article if I get enough bribes

 

[micjmac]

Bob are the fluctuations I mentioned 3 posts back anything to worry about?

 

[Bobnova]

Not at all, no.
That sounds perfectly healthy.
If it were jumping a full tenth of a volt, that'd be something to be concerned about.

 

[inVain]

hi, I know it's sound funny to post in the computer forum....
but since this is a multimeter how to, think I'm posting it anyway

so is there any chance to distinguished an N-type transistor from the P one by checking the foot with the multimeter?

since I'm dealing with the sot-23 packages and I think the local shop has mixed the type somehow, not to mention reading those such a micro letter printed on it was giving me a real trouble