good for normal use. avoid it if you're an OC kakis

The multimeter's accuracy has nothing to do with PFC, because reactive current should be of secondary domain and harmonics doesn't affect a DMM's reading, reactive power should be provided by generator and not the load. Accuracy depends on whether the multimeter is RMS or Root Mean Square capable, and if your multimeter is decent i don't see why it shouldn't have any issue as long as the CPS or Counts Per Second is fine.

Anyways i don't get what you're saying about the AC mode and current measurement. If you wanna measure your power consumption, you will have get a current reading. But personally i prefer using a clamp meter based off the hall effect. Less messy ya?



Build a shunt and use Ohm's law in the case of individual parts. I think i posted it here somewhere. Once you know resistance of the known shunt and since you obviously know the voltage, just find the current and use the Power law to derive a wattage. If you're calculating from the AC, remember to use RMS values and not peak.

But yeah, you could break the circuit and insert the DMM and let the current flow through. But as with all handling of deadly voltages, i don't recommend it. Get a clampjaw meter.

Thanks for pointing that out, though I'll have to clarify a bit.

Power factor should have an effect on current readings taken with a digital multimeter. If the power factor is poor, the current (based on the apparent power) which is measured by the DMM should be higher for any given power intake by the PSU-AFAIK the PSU will only use the real power component. So for non-PFC psu, the watt reading will be higher, which will not reflect the power consumption of the PSU. Its bad enough that we don't have a decent method of measuring the PSU's real life efficiency, having the power factor further compound the problem of getting accurate power consumption readings is just (theoretically, its possible for the measurement to be as much as 2x off the actual value, assuming a power factor of 0.7 and efficiency of 75%, which are typical values for cheap PSUs)

Most affordable clampjaw meters don't have enough accuracy to measure the AC current used by a typical PC. Most PCs take up 1-2A only (even a fully loaded 1000W PSU will only take 5A at most), so a clamp meter must be able to read up to about 0.01A to be reasonably accurate to a few percent, and those are pretty expensive. If accuracy is any worse, might as well use an affordable DMM (which would have similar accuracy).

And yeah, a shunt works too, like you mentioned. But you still have to cut a cable to put it in.

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Added on June 24, 2007, 3:40 pmJust remembered the key reason why I said using an active PFC PSU is important-active PFC PSUs typically have power factors of 0.99 or better, which will mean the current waveform will be sinusoidal (assuming the AC voltage is sinusoidal-not likely to be perfect sine wave, but should be ok unless your AC supply is outright shit). A sinusoidal current waveform will allow even non-RMS DMMs to give decently accurate readings (my estimate is it would be less than 30% off, which is better than most of the affordable clamp meters)

This post has been edited by lohwenli: Jun 24 2007, 03:40 PM

TDP stands for Thermal Design Power, which can be more or less taken to be the power consumption of the processor. In the PSU calculator, the percentage refers to your typical usage of the processor. If you're an overclocker or a heavy user which does a lot of video editing or number crunching when just set it to 100%. Otherwise just place your estimate. 80% is still a safe bet for non-overclocked systems, even for gaming.

bought AMD athlon 64 x2 3800, Gigabyte SLI mobo, Cooler Master Centurion, 1 GB of Kingston DDR667 ram and a Gigabyte 8600GT. (Will buy another to complete the SLI bridge). I have 2 sata HDD and 1 IDE. 2 layer of LG DVDrw and CDRW. Is this PSU can stand those stack of items i mentioned?

Or shoul i buy Cooler Master Real power ACLY/X? 450wts

have a question about power consumption here. my friend want to change his cap ayam psu bcoz the number of molex output is too small (i`d say 5@6). so can someone suggest me the psu that suits his specs?

amd64 x2 3800+
gigabyte ga-m51s2g
cvs ddr2 667 1gb
160gb hdd
internal graphics
3x120mm fans (leds)
2x80mm fans
dvd-rw
ccfl

so suggest me what brand and how much power?

Silverstone OP650
Nahh, it's overkill for that system.

cis gila kau!! he`s not an o/cers la.. just need some extra power. i think ss op650 is way way off his budget la
btw how about cooler master extreme power? is it ok?

maybe Acbel 350watt/450watt already enough for that system. but if ur friend got interest in getting a good gc, go for Acbel 500watt or other branded PSU with true power and active PFC....

edited: last time using Acbel 500watt, good for ocing and really stable (at least for me la since i'm not hardcore oc-er ).now using zalman silent PSU 400watt (downgraded maa ) still great for my ancient P4 3.2E soc478...

This post has been edited by rainingzero: Jun 25 2007, 11:30 AM

Dont forget to get activePFC feature when buying PSU coz besides of oc, also need to consider current's bill.

owh ic.. but acbel oso pricy la i think... how about other ayam brands like power logic atrix, i-cute and so on. are these brands are good enough to use in normal state (no o/c) ?

CM realpower is ok, though only the 550W and above has enough connectors for SLI (you won't need so much power though). For the cost of a Realpower 550W it might be better to get a silverstone. I'm not sure which silverstone models support SLI though.

CM extreme power is ok, even for overclocking low power systems. But stay away from the models boasting more than 430W-the 5xxW model can barely pump out 470W.

Active PFC won't reduce your electricity bill much, but it will make your life easier if you happen to be using a UPS-you'll get more battery time. Main advantage of active PFC is that those PSUs handle AC voltage fluctuations better, and reduce the need for a voltage regulator.

I'm not sure about power logic, but an icute i tested seems ok, though I wouldn't suggest using it on PCs taking more than 150-200W. Voltage regulation for most icute are pretty sloppy when load is heavy. And I'm also not sure how well it handles overheating.

Look out for these OEM brands-Enlight, Enhance, FSP. If you happen to dig one up somewhere, they are often good value for money. Very decent performance, usually almost dirt cheap price.

Previously my friend using Icute 450W used on his AMD64 1.8GHz @ 2.4GHz and 6800GT. Lasted for a year and then kong.

Hmm, seems icute has reliability problems, I wonder if its simply because of poor circuit design or due to overheating. That system doesn't take that much power. Didn't have enough time to check the components of the unit i handled.

iCute 450W real power is around 250W only lar... if OC of course kong la... Try realpower 300W and above... or OC c2D or Celeron CPU without adding voltage... can undervolt summo... then u don need so much power...

Just let ur pocket spill some RM200 and above to get better PSU.

got it. just bought my friend a cooler master extreme power 450w. price around rm160. i think this psu is enough to power his rig.

I'm very much not really worried about PSU and PFC because it's very much universal thesedays in switching power supplies due to the requirement of the european market. And depending on place, Apparent power might be factored in as billable power and not just the bog standard Real Power as the billable power. Seeing how power companies are seeking to minimize losses and the advent of high performance powermeters with waveform analysis, i think it's possible.

a 2 voltmeter setup with a variac could also work, but then again, variacs aren't cheap. But i do favour a shunt for the simple fact that you can board it and place proper probe points instead of the circuit breaking method where you'll have let the multimeter's leads form a part of the circuit. Anyways, been using shunts for graphics card power consumption numbers, and 1 ohm to half an ohm works fine for me so far, although for the power through the moboslot, i'll just take my numbers from the PCI-SIG WPs.

how much you estimate this system consumes power?

AMD Athlon 64 3000+ (Overcloked @ 2.4GHz)
DFI NF4 Ultra Infinity
2x Corsair 512MB DDR400
3x HDDs
8800GTX 768MB
4x casing fans with some lights...

im running it on Coolermaster RealPower 450W

do you think it is enough?
i feel the psu is running more hot than before i use 8800GTX (7600GT before)
but the meter (comes w/ coolermaster psu) showing that my system only draws around 100+ Watts only...