Power meter questions

comomolo · Post by **comomolo** » Sat Mar 22, 2008 8:48 am

Hi everyone

I just bought one of those power meters (a Chinese no-name thing at the supermarket) and I've been playing around with it for a while. I have checked appliances I know well such as lamps, microwave, toaster, etc. and the readings seem fine.

Then I went to check my PC and I get something weird:

- When the system is shut down I get 11 W
- If I turn the PSU switch off too, I get 4 W

Only if I remove the plug from the wall I get 0 W...

Is that normal? Why is that?

Thanks for any help.

BTW, here's my rig:

Case: Antec P150
Mobo: Gigabyte GA-MA68GM-S2H (ATI 690G chipset)
CPU: AMD Athlon BE2400 (2300 MHz)
2 GB RAM
3 x 500 HDD

It idles at 75 W, more or less, and no matter how hard I try, I can't get the system past 120 W. Nice (if the meter's right, that is...)

Post by **MikeC** » Sat Mar 22, 2008 10:48 am

Yes, it is normal.

When your systems is "off" it's actually on standby. The 5V standby current is live, and keeps the USB ports live, along with a portion of the motherboard in order to for it to "see" the trigger on signal from the momentary contact switch (fron panel PC power switch).

11W is pretty high on standby, tho. This implies the PSU does not have Active PFC and/or is poor on efficiency in general and/or you have many USB devices left plugged in all the time.

The 4W you see when the power switch is off is not good. Again, this suggests poor efficiency and/or non-APFC.

Is that a NeoHE430 PSU that came with the P150? Unfortunately, that was reviewed before we began to measure standby / turn on power. If there's one kicking around here, I'll toss it up on the test bench some time this weekend.

I'm not surprised you don't exceed 120W AC -- that's about what I'd expect. 99% of hardware sites keep the "must have unlimited power" mantra alive.... for the benefit of all the hardware sellers in the biz.

comomolo · Post by **comomolo** » Sat Mar 22, 2008 11:47 am

The PSU is the NeoHE430. Not exactly the one that came with the case, because that one had the famous issues with Asus mobos and I had an Asus mobo back then. Antec replaced the PSU for a new one. S/N (under bar code) in this one is: S06020203265.

Yes I have a number of USB devices connected to the computer, including a scanner and printer on standby, but removing USB connections doesn't seem to change the reading in the meter.

I have 235 V AC here, confirmed with a digital multimeter. Maybe this has something to do with it?

(I'll be trying a few other PSUs and computers during the weekend. I'll let you know how they behave.)

The meter is a clone of this one:

http://www.rce.it/strelettr/strelettr.htm

Post by **MikeC** » Sat Mar 22, 2008 12:37 pm

Your meter probably works fine.

Try this -- unplug the ATX and AUX12V connectors from the motherboard. Then when you measure the power with the PSU plugged in, you'll only be seeing what the PSU itself pulls. The motherboard probably has some power draw when it's "off".

Whether it's 235VAC or other doesn't matter.

nutball · Post by **nutball** » Sat Mar 22, 2008 11:39 pm

I'm a little surprised by the idle draw to be honest. I'd've thought that if C&Q were working as it should it would be lower, in the 40-50W range.

comomolo · Post by **comomolo** » Sun Mar 23, 2008 4:20 am

C&Q is working properly I think. It idles at 1000 MHz. Also, I'm reading somewhat lower figures for the latest 20 hours. They are around 65 W now but I've also seen 50 W numbers occasionally (maybe Windows services are doing something here, this is not exactly a fresh install...)

To be honest, my worries were about the meter itself. I need to make sure it works for other builds, not for this particular one. This is my own system and I keep trying things on it so I wouldn't be surprised if either its software or hardware is not perfectly tuned at the moment. My main concern is making sure the systems I build for my customers work properly and that's why I bought the meter.

However, I'll try Mike's suggestions and will post the results to see if there's something wrong with my PSU or other parts of the system. It'll be a good learning experience.

Arvo · Post by **Arvo** » Sun Mar 23, 2008 8:42 am

This little chinese(?) device (I'm using one myself, this time it is named "E-Tech Energy Meter PM300") most probably cannot handle reactive loads properly. I just bought FSP/Fortron Epsilon 80Plus 500W, power meter shows about 22W(!) while PSU is turned off by its switch and 24W while turned on (PC is off)... According to internet real active load of this PSU should be about 2W while PC is in standby - this corresponds to 2W difference well; other 22W seems to be pure reactive load (VAR, not W).

Thus you cannot trust such power meter readings at lower loads, when PSUs power factor correction may not work at full 99%

Well, one thing is sure - your PC consumes not more than cheap PM says. It may consume less.

comomolo · Post by **comomolo** » Sun Mar 23, 2008 9:23 am

But I can trust it for 200+ W readings? That's what's really important for me right now.

I'd love to get a better meter in the future, so suggestions are welcome. (How about these: https://www.wattsupmeters.com/secure/products.php ?)

Post by **MikeC** » Sun Mar 23, 2008 9:49 am

comomolo wrote:But I can trust it for 200+ W readings? That's what's really important for me right now.

I'd love to get a better meter in the future, so suggestions are welcome. (How about these: https://www.wattsupmeters.com/secure/products.php ?)

Those are good... but this one from Maplin in the UK works as well and it's much cheaper. Looks like it might come from the same mfg as the KillaWatt

Arvo · Post by **Arvo** » Sun Mar 23, 2008 1:12 pm

comomolo wrote:But I can trust it for 200+ W readings? That's what's really important for me right now.

Yes, IMHO you can, with some error margin of course. If for example your PSU has power factor of 96%, then 200W corresponds to 208VAR (I mean device will show 208) - not so big difference. With PF=99% there's only 2W (or VAR? Let's say 2 units

) difference, this is similar to error margin (good devices have accuracy about 1-2%, which corresponds to 2-4W error).

And you can compare loads with less (absolute) error too.

@MikeC
Interesting, are such devices for "normal" EU sockets available? (Haven't seen here in Estonia.) Needs to search on .de or .fi domain

Felger Carbon · Post by **Felger Carbon** » Sun Mar 23, 2008 2:20 pm

Here's the PDF manual (~200k) for the Etech PM-300. At the top you can see the pic; at the bottom the specs. It reads 230V with a resolution of 0.02A - that's a resolution of 4.6W (I think). Not designed for low-power loads, it would seem.

floffe · Post by **floffe** » Sun Mar 23, 2008 2:23 pm

@ Arvo: A quick search at Sweden's largest gadget store revealed at least 2 different variants with Type F connections (the round one with two pins + earth on the sides)

comomolo · Post by **comomolo** » Sun Mar 23, 2008 10:38 pm

Arvo wrote:
comomolo wrote:But I can trust it for 200+ W readings? That's what's really important for me right now.
Yes, IMHO you can, with some error margin of course. If for example your PSU has power factor of 96%, then 200W corresponds to 208VAR (I mean device will show 208) - not so big difference. With PF=99% there's only 2W (or VAR? Let's say 2 units ) difference, this is similar to error margin (good devices have accuracy about 1-2%, which corresponds to 2-4W error).

And you can compare loads with less (absolute) error too.

Good enough for now then. The reason I like the expensive WattsUp is the USB connection in the Pro Version. That would allow me to make more serious analysis of the power consumption. (To be honest, good digital multimeters will also provide an RS232 port for the same purpose, costing less and being more versatile, albeit more complex to use.)

@MikeC
Interesting, are such devices for "normal" EU sockets available? (Haven't seen here in Estonia.) Needs to search on .de or .fi domain

Yep, that's the issue for me too (and no, I havent' found them with the EU socket). Sure you can put an adapter in the back and another one in the front, but that makes the thing bulky and inconvenient. Another interesting feature of the WattsUp in this department is the international Universal Outlet (IEC320) version. It will work everywhere. They even provide you with the right cables for each region. Considering the current weakness of the US dollar, buying from Europe is not that bad. Oh well, let's sell a few workstations first...

If you want to search in German domains, the thing is called "energiemessgerÃ¤t" or "energiekostenmonitor"

nutball · Post by **nutball** » Sun Mar 23, 2008 11:57 pm

Arvo wrote:@MikeC
Interesting, are such devices for "normal" EU sockets available? (Haven't seen here in Estonia.) Needs to search on .de or .fi domain

The meter I have is made by Brennenstuhl, who sound somewhat German to me. I presume they'll service the whole EU market, not just the UK!

Arvo · Post by **Arvo** » Mon Mar 24, 2008 9:27 am

Many thanks for hint - Brennestuhl BS-PM230 does measure V/A/cos phi/frequenzy and real wattage (V x A x cos phi) and seems to be available even here (for 26.40 â‚¬)

Navvie · Post by **Navvie** » Wed Mar 26, 2008 11:24 am

MikeC wrote:this one from Maplin in the UK works as well and it's much cheaper. Looks like it might come from the same mfg as the KillaWatt

I have one of these and I think it is pretty reliable! I've tested in lamps and things where I'm pretty certain of how much power is being used. I have used it to test my PC, and other PCs and always find the results quite interesting, as do the people who's PCs I test on.. no, you really don't need that 750watt PSU!

The manufacturer is Prodigit Electronics, Taiwan.. although the device itself bears a 'made in china' sticker.

Cheers,
Mike O aka The Navvie.
(Long time lurker and reader, but first time poster.)

kater · Post by **kater** » Thu Mar 27, 2008 1:21 am

Voltcraft sells a variety of power meters in Europe, AFAIK they now offer at least 3 models, the newest is quite advanced - Energy Logger 3500. They are always in Conrad.

comomolo · Post by **comomolo** » Tue Apr 08, 2008 5:16 am

I just received my Voltcraft Energy Logger 3500 from Conrad (and returned the Chinese thingy). Very nice service from Conrad BTW. Their international sales people speak English and everything went smooth.

My first measurements:

PSU switch ON (Computer OFF): 2.9 W
PSU switch OFF: 0 W
CPU Idle: 65 W
CPU BurnIn (two times, one per core): 95 W

Now that makes sense to me. (It also makes me happy!!)

I'll try it this afternoon with a system that used to climb up to 400 W at startup, and will see.

Also, as soon as I get hold of a suitable SD card, I'll play with the logged data and bring a few curves here.

EDIT: A system with 8 HDD, a Q6600 CPU and NVIDIA 8800GT draws a peak of 610 W at startup, then it stabilises at some 180 W idle, 240 W at 4 x CPU Burn In (haven't tried graphics and disk stress yet).