Calculating how many watts your psu is using

L

lt.murda

Limp Gawd
Joined
Apr 16, 2005
Messages
381
My friend is looking for a program that can tell you how many watts your PSU is useing on load.Do you guys know of any such programs?


Thanks
 
I think they have software like that if you are using an ups (uninterrupted power supply)

Haven't seen any that works on a computer alone
 
Unless your PSU has some monitoring built in you will need an external device to measure your computer usage power such as the P3 Kill a Watt meter which is easily obtainable on ebay. I got one for $40 Can after shipping & postage extortion fee (cough I mean customs handling fee)
 
well first you have to ask the question of what your measuring AC or DC
second you have to determine why you want to know, As in are you buying a PSU?

if so watts dont mean jack
its amps and of the right voltage your concerned with

the draw at the outlet also has little to do with what DC its supplying
you have to factor both the current load and the efficiency at that load

if its AC you have to deterime if its volt amps your after (VA) the apperant power
or the real power which is VA times the power factor

as far as what a "typical" config may draw in real life as opposed to worse case senerios
http://www.silentpcreview.com/article265-page1.html


in here unless your estimating to get as quiet and as lean as possible, a healthy overpower will see you through the next upgrade with care and increase the life expectancy of the supply, silent computing runs much much closer to the bone however

calculators are additive in nature, and many PSU manufacturers lie
the link I supplied is the process I employ to factor those two into an answer
 
Ice Czar said:
as far as what a "typical" config may draw in real life as opposed to worse case senerios
http://www.silentpcreview.com/article265-page1.html
Click to expand...

Ice Czar said:
the link I supplied is the process I employ to factor those two into an answer
Click to expand...

I have seen that article before and it appears to be well done

Did you happen to catch this part:

THE HEAVIEST LOAD

As a matter of curiosity, a system of the most power hungry components in our lab was put to the highest load we could devise.
Click to expand...

now I'm not a powersupply expert but it seems to me that "heaviest load we could devise" is something similar to worst case scenario (I know there are other things they could have done to make it worse, but there are things you could do to get every single powersupply to fail)

It is located on this page: http://www.silentpcreview.com/article265-page4.html
 
well if you follow the process Ive outlined for discounting some of the amp draw of devices that have spun up, you'll be alot closer to their figures, but no, they didn't do a wprse case senerio in those tests. They have in the past however.

http://www.silentpcreview.com/article166-page2.html

A Technical Postscript: Output Voltage Regulation and AC Voltage

Voltage regulation with most PSUs examined by SPCR has been virtually unnecessary. Perhaps because only reputable brand samples are submitted for our stringent testing, almost every PSU has passed voltage regulation checks easily, often with flying colors. The Seasonic Super series were among the best in this regard, and the new Rev.03 models are no different, with tolerance better than +/-2% in every case.

A test instrument mentioned in the article SPCR's Revised PSU Testing System was used briefly with the new Rev. 03 samples. The California Instruments 801RP Variable AC Power Supply (CI-801RP) allows AC voltage to be varied in order to consider the effects of brownouts and other real-world conditions on PSU performance.

As the voltage is reduced, the PSU has to draw more current (Amps) in order to maintain the output voltages. The actual power drawn by the PSU rises when the input voltage is reduced. This is why, for example, that a power supply rated for 120VAC, 5A might be rated for 240VAC, 3A. Maintaining steady output voltage lines becomes much harder with lower or varying AC voltage. This is how PSU voltage regulation can be really tested.

The PSU was placed in the thermal test rig, with 120VAC power delivered by the CI-801RP. Each PSU was warmed up for a few minutes at 120W, then set to deliver full power. Internal test box temps were ~37°C. AC measurements were made with the Kill-a-Watt AC power meter. Voltmeters were used to continuously monitor the 12V, 5V and 3.3V output lines. The VAC was then reduced from the standard 120VAC down to 80VAC. This is a very demanding test, as the Seasonic PSUs are rated for full power output with 100-240VAC.

Seasonic S. Tornado 300 @ 300W load
VAC....Amps.....Watts.....12V........5V.........3.3V
120......3.13.......372........12.08......4.96.......3.34
100......3.8.........378........12.08......4.97......3.34
80........5.6.........500.......12.07.....4.97......3.33

Note that the output voltage remains constant through these dramatic drops in AC input voltage — and the associated increases in the current and power drawn by the PSU.

The same test was conducted at 300W output on two other SPCR-reviewed PSUs that will remain unnamed at this time: One rated at 350W sparked and shut down within 15 seconds of running at 90VAC. It appears to be dead. The latter, rated at 380W, auto-shutdown safely within seconds of 100VAC operation. It appears to consider operation at any AC voltage under ~103W to be unsafe.

It is a measure of the Super series' quality design. It means that sags and brownouts in AC power, experienced by many people in many places in the world, should have little effect on a computer powered by one of the Seasonic Super series PSUs. A table of the Super Silencer 400 could have been posted but it would have been redundant because the voltage accuracy and output remained constant down to 80VAC there as well.
Click to expand...

and while the total load doesn't change the reserve the supply has can effect how well it deals with variable VAC

the problem is that 300W doesnt equal 300W
in reality you can compare 500Watt supplies to 300Watt supplies where the later will kick butt, do to better amp distribution, design and what temperature they where rated at.

Many supplies are rated at 21>25C and for a peak rating (split second) while a good supply is rated at 40>50C at a continious rating



POWER SHMOWER
or How PSU Power Ratings Mean Almost Nothing

A frustrating fact about PSUs is that there does not appear to be a stringent or regulated standard for reporting, advertising and labeling rated power. This is despite the existence of standards like ATX2.03 or Intel ATX12V.

There are well-established standards for measuring and rating HDD capacity, an engine's horsepower, or the heat generated by a furnace... but not one for how much power a PSU can deliver. There are so many cases of people with "450W" PSUs having power stability issues running a system that can't possoibly draw more than 150W. And "300W" units that keep running where the "450W" units are faltering.

It's not just about bad PSUs vs better ones. It's a dumb situation caused by uncontrolled marketing competition. Real regulation would bring PSUs out of snake oil territory and into a more sensible consumer-friendly terrain.

There are many ways PSU makers fudge to make their units seem more powerful.

1) Out and out lying. You add up the power on all the lines in many PSUs and they fall short of the rated power by 10, 20 30W or even more.

There are more sophisticated ways:

2) Limit the AC input voltage to a very narrow tolerance. The best PSUs are able to deliver their rated power given a decent range of AC input power, say 90~130V for a 120V unit. It's much more demanding to produce 300W w/90VAC input than with 120VAC, so what some PSU makers will detail in their tech specs (usually not in their consumer brochures) is to specify 115-120VAC for input power. A PSU specified this way will not deliver full power if the AC voltage sags, if there is a brown-out. Surely it causes instability more often than a PSU rated to deliver full power with 90-130VAC.

3) Specify a low operating temperature for rated output. This is quite common, but again not often seen in consumer brochures, but rather tech spec sheets provided usually only on demand by engineers or corp buyers. A typical PSU operating temp statement is somthing like this:

0ºC ~25ºC for full rating of load, decrease to zero Watts O/P at 70ºC

Examine what that says. Full power (let's say 400W) is available when the unit is at 0ºC ~25ºC. Hmmm. Think about this.

Have you ever felt air blown out of a PSU in a PC running absolutely full tilt (which it would have to do to get anywhere near 400W output) that felt cool to the fingers? 25ºC airflow would feel exactly that: Cool, given that normal body temperature is 37 °C.

So this PSU cannot deliver full rated power when its temperature goes over 25ºC. OK, what happens to the max power output capacity above that temp? It decreases gradually so that by the time the PSU temp reaches 70ºC, the PSU cannot deliver any power at all. So if you assume that this power drop as temp rises is linear, then max power capacity will drop by ~9W for every degree over 25ºC.

Now having examined as many PSUs as I have over the last 2~3 years, I have to say there's not a single PSU in ANY PC I have ever used or examined that would not measure at least 30~35ºC almost anywhere inside the PSU under almost any kind of load. And if/when it is pushed, 45ºC is nothing at all, especially for or near hot running components like voltage regulators.

So let's say 40ºC is a fairly typical temp inside a PSU. This 400W rated unit would actually be able to deliver a max of just 220W at that temp. Hmmm. Interesting, isn't it? At 50ºC, the available power would drop to just 130W. No wonder some PSUs have 3 fans each capable of 50 cfm!!

Here's a simple fact: Really high quality PSUs are actually rated for full power output at as high as 40ºC. The trick is get a hold of the spec sheets that tell such information so you can compare apples to apples. Or ask.
Click to expand...


from dansdata
Unethical PSU Marketing 101.

Here's how to make overly optimistic power supply specifications. It's really simple.

First, power the thing up. You can make an ATX power supply that isn't connected to a motherboard turn on by grounding pin number 14 on the big motherboard power connector. It's easy to spot that pin, because it's the only one with a green wire going to it.

Use any handy bit of wire - like the paper clip in this picture - to connect pin 14 to any ground contact. The ground contacts are the ones with the black wires going to them. Presto, the PSU will turn on.

Now, break out your brick-sized power resistors and load the heck out of one of the output rails - the +5V rail, for instance. Measure the current as you increase the load, until the voltage sags unacceptably far below the rated voltage.

How do you tell what an unacceptable voltage sag is? Well, you could choose a nice conservative small permitted sag - say, 0.1 volts - so that your results are genuinely useful to your customers. Or you could just ignore the voltage and say that when a fuse (or some other component...) blows, that must have been the limit, right there.

OK. Now you've made a big fat amperage number for the +5V rail. If you blew up the PSU in the process, get another one, and repeat the process for +12V and +3.3V, and for the low current rails as well.

On no account, though, should you test more than one rail at a time. This is the key to the whole scam.

A big beefy PSU may be able to deliver 50 amps (say) on the 5V rail when nothing else is under load, and 25 amps (say) on the 12V rail when it's similarly all alone. But the 12V and 5V rails together may only be able to deliver, say, 350 watts between them, when they're both under load. Watts equals amps times volts.

In a real PC, all of the power rails will always be under load together.

But you're not testing what the PSU can really do - you're making pretty numbers for the sales brochure!

So test all of your rails alone, get an amperage figure for all of them, multiply that figure by the voltage of the rail it came from (the nominal voltage, not whatever the voltage had sagged to as the PSU pumped electrons through the dessert spoon you'd soldered to the circuit board), then take all of the resulting wattage figures and add 'em up. That's a wrap, folks. Ship it!
Click to expand...

there is a difference between the heaviest possible draw you can create
and a worse case senerio, in the worse case, its summer your upstairs and the AC dies, meanwhile your on deadline while the room temperature steadily climbs, you switch off all extraneous equipment but the room still gets hotter, as it does the capacity of your supply drops (known as a derating curve) every other yahoo in town has their ACs cranked and the utility is having problems dealing with it, there are intermittent brownouts, your UPS has discharged batteries and you havent replaced them.

Thats a worse case.

For me with my boxes in a rackmount relocation to the basement isnt an option, under deadline would be completing the rendering of a 3D scene.
 
his rig self feeds heat from the resistors in the DBS-2100 PSU load tester
which at a given ambient is a fair representation of what would really happen, what he doesnt do is set the whole shooting match into an environmental test chamber and raise that ambient.
 
but then "a fair representation of what would really happen" isn't worse case scenario sorta like 80VAC isn't a fair representation of what one would expect from their outlet
 
DOH :p

the heat produced by the resistors would be proportional to the load on the supply once we get done making the electrons dance through a few hoops first, the variables would be the heatsource locations and sairflow pattern in the box, Mike has his rig setup so that it all cycles through the PSU, in reality there would ba a hot exhaust on an aircooled heatsink closer to the PSU but also additional heatsorces might not even be cycling through the PSU do to other exhausting fans, that part is pretty reasonable, but the ambient temperature in his lab is the control, as the ambient rises all thermal solutions decrease in efficiency and it becomes harder for them to dump their heatload for the set massflow and interface area

http://hardforum.com/showpost.php?p=1027988413&postcount=7
 
He wants to know if he can add 4 more hard drives with the following specs.

msi neo4 platinum motherboard
1 sound card audigy 2 in pci slot
1 tv tuner card in pci slot
1 dvd-rw 16x and 1 cd-rw 52x
1 floppy drive
5 case fans
4 hard drives (2 raptors, one 200 gb wd one 30 gb maxtor)
ati x850 xt
athlon 64 4000+
2 GB ddr 400 corsair 4x512
antec true550 watt PSU



The 4 hard drives he wants to add are 250gb 8mb cache
 
davidhammock200 said:
If TP II = yes
If +12V@36A = yes
If +12V@30A = probably
If +12V@24A = probably not running anyway

If the case is keept cool enough.

Jusy MO,
Dave ;)
Click to expand...

He said his psu is running at 23 a on the 12v+,but it only has 1 rail
so basically if he adds 4 more HDDS his psu might bite the shit?
He plays games fine and everything with no visible signs of stress or failure
 
lt.murda said:
He said his psu is running at 23 a on the 12v+,but it only has 1 rail
so basically if he adds 4 more HDDS his psu might bite the shit?
He plays games fine and everything with no visible signs of stress or failure
Click to expand...
If his is an old TruePower with only +12V@24A, then I'm surprised it's running now!

Of course those were industrial PSU's back then & way under-rated. ;)
 
You must log in or register to reply here.
Back
Top