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+12v fluctuating

wiskeychris

Limp Gawd
Joined
Dec 17, 2002
Messages
168
should I be concerned? It keeps switching from 11.84 to 11.90. I just plugged in two 200gb hdds.
 
wiskeychris said:
should I be concerned? It keeps switching from 11.84 to 11.90. I just plugged in two 200gb hdds.
How do you know it is fluctuating?
 
wiskeychris said:
I'm watching the temp monitor. Asus probe.
Software readings aren't reliable. Get a multimeter to check the voltages if you are concerend....however even at its low point that voltage is in spec.
 
Wait, so if anything, I'm low? I really dont understand how the whole voltage things works. I just bought a new 7800gt and I have a good antec 400w psu. Just want to make sure I have enough. Thanks for the help.
 
wiskeychris said:
Wait, so if anything, I'm low? I really dont understand how the whole voltage things works. I just bought a new 7800gt and I have a good antec 400w psu. Just want to make sure I have enough. Thanks for the help.

Ok so each rail in a PSU is supposed to run at it's rated voltage 12v, 5v, or 3.3v. When you say yours is at 11.84 to 11.90 that is below the rails rated voltage of 12v....however, the spec defines a tolerance of +/-5% in which the componenets will still function properly. So even you lowest reading of 11.84 is still in spec. SOftware readings can be off in either direction....they are really a crapshoot.
 
wiskeychris said:
Ok cool. I get it. Thanks for the info, these are really the best boards on the net.
We try....if you need anything else just ask.
 
I used to think that mobo monitors couldn't be trusted for absolute voltages but indicated fluctuations accurately. Then I had a mobo where the built-in monitor showed that the +12V fluctuated a few tenths of a volt, but my multimeter indicated a rock-steady +12.11 all the time all the time.
 
larrymoencurly said:
I used to think that mobo monitors couldn't be trusted for absolute voltages but indicated fluctuations accurately. Then I had a mobo where the built-in monitor showed that the +12V fluctuated a few tenths of a volt, but my multimeter indicated a rock-steady +12.11 all the time all the time.

let me comment on this. DMM's do not show changing voltage very well. That is, they tend to take the average voltage. It actually shows you the RMS voltage (root mean square) Some better multimeters have a min/max option. So it is likely you will see a steady value with a DMM when the voltage is actually fluctuating. Oscilliscope would be the best way to measure this, or second best use a min/max feature on a good DMM perhaps. (This is why Tom's hardware used an oscilliscope on their stress test)
 
aL Mac said:
let me comment on this. DMM's do not show changing voltage very well. That is, they tend to take the average voltage. It actually shows you the RMS voltage (root mean square) Some better multimeters have a min/max option. So it is likely you will see a steady value with a DMM when the voltage is actually fluctuating. Oscilliscope would be the best way to measure this, or second best use a min/max feature on a good DMM perhaps. (This is why Tom's hardware used an oscilliscope on their stress test)
My meter can record min/max for RMS values, and it showed less than 0.1V fluctuation over about 15-20 minutes.
 
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