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Posted by xavros (148.221.53.112) on September 21, 2003 at 18:55:03:
In Reply to: Re: pmpo vs rms posted by deepti on March 02, 2003 at 12:25:53:
: : : : Time and time again I see people referring to r.m.s. power, and time and time again I see people correcting, as I am about to do yet again, the confusion.
: : : : The product of r.m.s. voltage and r.m.s. current, (i.e. Vrms x Irms), is equal to AVERAGE power, NOT r.m.s. power. There is NO SUCH THING as r.m.s. power.
Well I'm Electronic and Communications engineer and I have a Maestry in Electronic Systems, I can say some really stupid things about EFFECTIVE POWER (RMS) and AVERAGE POWER, AVERAGE POWER is for DC Voltaje and Current, DC Voltaje or Current is when there's ONLY positive o negative component, AC is when there is (are) component POSITIVE AND NEGATIVE, even there's only a few femtoseconds peak, EFFECTIVE POWER (RMS) is for AC signals and there are EFFECTIVE POWER and APARENT POWER (RMS) where we are talking about EFFECTIVE POWER (RMS) is for FACTOR POWER = 1, APARENT POWER (RMS) is -1
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: : : : Yet people doggedly cling to their misconceptions and propogate the myth. Part of the trouble is that no-one likes to have their cherished beliefs challenged and most of them refuse to accept that they could, even possibly, be wrong.
: : : RE: Boy that really is bad news to those of us that have spent years in the indusry using RMS power meters made by such pervayers of misinformation as Hewlett-Packard for example. Which reference material are you quoting that indicates there is no such thing as R.M.S. power?
: : Try using E2/R instead of ExI to get power. A typical example is an amplifier providing 20 vrms into an 8 ohm load. That will give you 20x20 (400) / 8 = 50 watts RMS into 8 ohms. This is a federally mandated standard as outlined:
: : Back in the 1960's, audio equipment manufacturers and dealers were having a hey-day with power specifications, rating their little 20-watt-per-channel amplifiers as having 80 watts. Here's what they would do. Rather than using the RMS voltage of the amplifier output which might be 12.6 volts driving the 8 ohm speaker, they would use the peak voltage (17.9 volts) and figure power that way: (17.9)(17.9)/8 = 40 watts. And then they'd add both channels together: 80 watts. Sounds high-power in the advertizing, but in actual practice was misleading.
: : The Feds finally got into their faces and made everyone rate their equipment in RMS power into 8 ohms for each channel.
: : Ok, now I feel better.
And Now I wonder why was Fourier so Stupid??? I mean told that a periodic signal could be represented by sin's and consins's adds??? and gave us a Spectrum!!!! hag!!!! I dont understand this world!!!
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