Measuring power draw of various components?

[brikis98]

Is there a way to measure how many amps and/or watts are being pulled by the various components in a computer - for example, how much juice the CPU is using or how many amps on the +12V rail(s) the video card is really pulling in?

 

[brikis98]

anyone?

 

[sdy284]

you have a DMM?

 

[brikis98]

Originally posted by: sdy284
you have a DMM?

DMM = digital multi meter?

whatever it is, i doubt i have it 🙂

 

[sdy284]

well without a DMM (yes a digital multi meter)

then you're out of luck. Pick up a DMM & then you can measure pretty much any voltage/current/amps you want on your mobo

 

[Navid]

Originally posted by: sdy284

Pick up a DMM & then you can measure pretty much any voltage/current/amps you want on your mobo

How do you measure the CPU current with a meter without causing damage (cutting tracks) to the motherboard?

 

[sdy284]

very carefully 😛

i've never done it but I know its possible

 

[Navid]

Originally posted by: sdy284
very carefully 😛

i've never done it but I know its possible

Yes, it is possible after you cut the track on the motherboard. For your information, a Volt meter is placed in the circuit in parallel while a current meter is placed in series.

 

[brikis98]

so, even though there is software that lets you see the voltage readings on the various rails (5V, 12V, etc), there's no software that can tell how much current is going through those same rails?

 

[Bobthelost]

No, none at all. You'd either have to cut the track or use some sort of induction method (which can't be done without cutting the board the track is on....

You could always make an extention socket for the CPU to sit in (betwen the CPU and the socket) and measure the power flowing through the pins there, but that'd be a pain in the rear to do as well.

 

[brikis98]

well, i just wanted to do it out of pure curiosity. for example, the x1900xtx i have says i should have 30A on the +12V line but i'm pretty damn sure that with everything combined on the +12V line i won't come anywhere near 30A. but, it sounds like way too much of a pain to check, so to hell with it.

 

[Navid]

Originally posted by: brikis98
well, i just wanted to do it out of pure curiosity. for example, the x1900xtx i have says i should have 30A on the +12V line but i'm pretty damn sure that with everything combined on the +12V line i won't come anywhere near 30A. but, it sounds like way too much of a pain to check, so to hell with it.

To see how unrealistic those numbers are the simplest thing to do is to get one of these.
http://www.p3international.com/products/special/P4400/P4400-CE.html

This is an example of one through Amazon.
http://www.amazon.com/P3-International-...Watt-Electricity-Monitor/dp/B00009MDBU

You just connect it and it shows the total power drawn by your PSU from the AC line. You divide that power by 12. That would be the most pessimistic estimate you can come up with for the current drawn from the 12V rail. It is pessimistic to the point of being incorrect because this calculation ignores the PSU efficiency completely and ignores all the power drawn through the 5V rail completely. Still, you will get a number that may surprise you.

If you are up to it, you can switch your graphics card and calculate the difference between the 12V rail current, that you measured, in the two cases and that may give you an idea what the current of your 1900 is.

 

[brikis98]

Originally posted by: Navid

Originally posted by: brikis98
well, i just wanted to do it out of pure curiosity. for example, the x1900xtx i have says i should have 30A on the +12V line but i'm pretty damn sure that with everything combined on the +12V line i won't come anywhere near 30A. but, it sounds like way too much of a pain to check, so to hell with it.

To see how unrealistic those numbers are the simplest thing to do is to get one of these.
http://www.p3international.com/products/special/P4400/P4400-CE.html

This is an example of one through Amazon.
http://www.amazon.com/P3-International-...Watt-Electricity-Monitor/dp/B00009MDBU

You just connect it and it shows the total power drawn by your PSU from the AC line. You divide that power by 12. That would be the most pessimistic estimate you can come up with for the current drawn from the 12V rail. It is pessimistic to the point of being incorrect because this calculation ignores the PSU efficiency completely and ignores all the power drawn through the 5V rail completely. Still, you will get a number that may surprise you.

If you are up to it, you can switch your graphics card and calculate the difference between the 12V rail current, that you measured, in the two cases and that may give you an idea what the current of your 1900 is.

cool, looks like a useful device.

anyone here have one or tried it and wanna post their results? 🙂

 

[Paperdoc]

Bottom line is: unless you REALLY! know what you're doing and MUST have the answer, DO NOT ATTEMPT THIS AT HOME!
As Navid said, to measure a current you must insert the meter in series with the load, which means breaking the connection and putting the meter into the circuit, then reversing the process to remove the meter. (By the way, just inserting a meter into a circuit upsets it slightly, because there is a small voltage drop across the meter itself.)
Bobthelost mentioned using an induction meter system. They ONLY work for AC, and electricians etc use these often on house wiring and so on. But they cannot pick up a steady DC current flow, which is what your computer is using out of the PSU.
Navid came closest. He suggested buying a power meter to place bewteen the wall outlet and you computer's power cord. It will only tell you total power being consumed (and he's right to say the efficiency is not well known). Then by swapping components you could see how much DIFFERENCE that makes, but it does not give you the actual number you wanted, which was: how many watts does your video card (or whatever) consume?