Message-ID: <01FD6EC775C6D4119CDF0090273F74A4022027@emwatent02.meters.com.au> From: "da Silva, Joe" To: "'opendos AT delorie DOT com'" Subject: RE: Power measurement (was [off-topic] shutting down) Date: Mon, 9 Apr 2001 15:10:39 +1000 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2448.0) Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id BAA24057 Reply-To: opendos AT delorie DOT com Wow! For an O/T, this stuff about SI/Imperial/American terminology and measurements sure generated a lot of messages! Anyway, back to the original topic ... You cannot determine the power consumption of PC's and monitors by just measuring the current - even if you measure this in RMS! Of course, if the current measurement isn't RMS, then that's even more useless! If you measure the RMS current and multiply by the (RMS) voltage, what you have is the "apparent power" (VA), not the "real power" (W). That's the reason why the "power" figures quoted below are higher than expected. Now, "apparent power" (VA) is the _vector_ sum of "real power" (W) and "reactive power" (VAR). So, what is "reactive power" (VAR), and what impact does it have? Well, it's the out-of-phase current ... it is current that recirculates in the power system but, apart from resistive losses in the wiring and generation system (ie. second-order effects), does not require any input (eg. coal) to the system. If we used superconductors for all this stuff, then even these resistive losses would disappear! So, the only way to correctly measure the power consumption of PC equipment, is to either use a proper power meter (hard to find) or use an energy meter (eg. the one at the front or side of your house) and see how much energy it accumulates in one hour (if necessary, run the test for several hours, then divide the energy accumulated, by the number of hours). Joe. > -----Original Message----- > From: Matthias Paul [SMTP:Matthias DOT Paul AT post DOT rwth-aachen DOT de] > Sent: Sunday, 8 April 2001 3:54 > To: opendos AT delorie DOT com > Subject: Re: [off-topic] shutting down > > On 2001-03-29, Robert W Moss wrote: > > This is going to be very off-topic, Iīm afraid, but I can no other > but comment on it... Sorry... > > > AFAIK an internal modem uses no (minuscule) power unless it > > is turned on and you are on-line. External modems would only > > use 9 watts when you are using them on-line, otherwise they > > most likely use less then one watt of standby power. > > Modems and most other external components are not the major > power consumers, of course, so at the first glance it might be more > important to have very good standby modes for monitors (standby/ > suspend ca. 0,5-30W, in operation typically 100-200W), (laser) > printers (up to kilowatts when in operation), and the computer itself > (typically 150-300W in operation), but since there are so many > other small devices in standby or suspend mode all the time > (VCRs, hifi equipment, TV sets, radio clocks, phones, answering- > and fax-machines, active loudspeakers, ...), their total power > consumption *is* significant. In Germany we say: "Kleinvieh macht > auch Mist." ("Even small cattle produces some manure.") Also, > these small devices usually have extremely inefficient transformer > power supplies, and often no true mains switch any more. > > > With computer prices being as low as they are, and big businesses > > replacing all of their work stations after three years, it doesn't make > > sense to most of the bean counters to worry about saving money by > turning > > off the complete system when you are not using it. Most IT managers in > > large Corporations just tell every user to turn it on in the morning and > > off when you go home, just logging off of the network when you leave > your > > work station. > > Even worst, recently I had a discussion with someone in our datacenter who > asked me not to switch off the computer and monitor over night because he > was afraid, it could get damaged. He stated, that the monitor (a five year > old > quality 15" model) would go into suspend and only the LED on the front > panel would continue to dim. It was very difficult to convince him that > he was wrong, because he couldnīt follow me, as he had no imagination > whatsoever of the inner components of a CRT... Only after I brought in > a meter to actually measure the power consumption in suspend mode he > suddenly became quiet: That monitor took 37 W in suspend mode, even > more than I had expected! Even today most monitors take at least 5 W > in suspend mode, Eizo/Hitec monitors are one of the few exceptions > I am aware of with just 0,5 W. Unfortunately, there are many people > out there without even a basic knowledge of electrical engineering... > > (Just check it out yourself, a simple meter will give you a good > approximation, but for accurate results you will need a true RMS > meter. You can also ask your power provider to lean you a > power monitor plug for a symbolic fee, so you can get a better > picture of the true power consumption of all the devices in your > office or household. You can also get them in most electronics > shops, but make sure you get one that has a resolution of at least > 1 W and is able to measure downto 1 W, otherwise itīs useless > when you want to measure in standby or suspend modes.) > > Of course, it *will* damage a desktop computer or a CRT monitor > if you permanently switch it on and off every few minutes, but if > you switch it on/off in terms of hours, thereīs no recognizable > shortage in its operating life (even if you speak of 5-10 years). > In this respect there even isnīt much difference between going > into suspend mode or completely disconnecting the mains. > > > This works great in the USA, until this year, especially > > in California, where the electric bills went up over 200% > > for a lot of people at home and more for businesses. > > AFAIK the problem in California is that they have reached > the upper limit of what their power stations can provide, > rather than that they would force usage of regenerative > energy now. But otherwise: > > Very good!!! Well, it shouldnīt be only a question of > money, but humans tend to start thinking only when it > hurts, and higher bills always hurt... It works with fuel > as well as with electricity. Nothing is moving without > any kind of pressure... > > Not that we would not have similar acceptance problems > over here, but what you are describing is what many > Europeans view as "typical American donīt care attitude", > it is a pitty... Fact is, weīre all sitting in the same boat, > and we are *all* responsible for it, and these problems > can only be solved globally... > > It took almost two decades, but quite many people over > here are "awake" now and are actively trying to change it > to the better, while according to the news and various > discussions there appears to be still "deepest winter" in > the States, unfortunately - just thinking of the World Climate > Summitt... > > This bill is just not balanced. With more than 6 billion humans > on this planet (and extrapolations for up to 12,5 billions in > about 200 years), we just cannot continue with hunting and > collecting (that is "consuming") like we did it for the past > few 100.000 years. It will come back to us (that is "humankind"), > and if not us, then at least our children will have to pay the > price for our ignorance. > > For example, have you ever thought of the fact, that according > to the statistics (estimates from 1998) natural oil will be available > only for another 45 years on earth, already counting in new > deposits that still have to be found and an assumed progress > of efficiency in using it? Consider that humans use it for just > about one century now in contrast to the millions of years that > were necessary for it to develop. Well, natural gas and coal > will probably last a bit longer (65 years and ca. 200..500 > years respectively), so this is nothing we should be worried > about, I guess, in particular since we have Uranum left for at > least 6.000..8.000 years... ;-> > > > When the cost of power goes up the ATX systems will > > come in handy when set properly to turn off or go on > > standby after a period of no activity. > > > > Ain't Technology Grand? > > Am I missing a subtle kind of irony here? > > Advanced *dynamic* power saving technologies in hard- > and software are a good thing in general to reduce the > overall power consumption of a device, but they a question > of smart ecologic design. I donīt think that it is a good > idea to leave an increasingly large number of devices > running in standby or suspend modes rather than actually > disconnecting the mains, when they are not used. When I > switch off my computer (non-ATX), it will consume 0,00 > (in words: zero) Watt. > > Just my opinion. > > Matthias > > ------------------------------------------------------------ > Matthias Paul, Ubierstrasse 28, D-50321 Bruehl, Germany > > http://www.uni-bonn.de/~uzs180/mpdokeng.html > ------------------------------------------------------------ > My homepage has moved, please update your pointers. >