In your first post you quote that "RMS Power" is "wrong", but it's being used by the audio industry and has been used for a number of years now.
Hardly a 'number of years'
As far as I'm aware it's been used all the time the electronics audio industry has existed, and certainly well before WW2.
Also, as far as I'm aware, NOTHING else was ever used, until the American advertisers got involved, and started claiming amplifiers were 150W etc. - when they were only 5W or so - that was probably late 60's?, early 70's?.
My little Name Brand 2.1 powered speaker system is advertised as, "150 Watts Total Output and Output RMS 75W". But inside it has a few small power amplifier ICs with little bits of metal glued on top as heatsinks and the transformer is marked "9VAC/1.1A" which is 9.9W . But the ICs are class AB that have about 60% efficiency so the actual output power is only 6W.
The difference between average power and RMS power is so small that it cannot be heard because our hearing's sensitivity to loudness is logarithmic so we can hear things that are very low level and hear very loud things. Double or half the power is just a small loudness difference. 10 times the power sounds twice as loud and 1/10th the power sounds half as loud.
My 52 years old Scott stereo receiver suddenly produced lots of hum. The 5000uF/50V main filter capacitor has no microFarads anymore. I tried to remove big capacitors from amplifiers I do not use anymore but they are glued down so I cannot remove them.
That could be 1 year to 200 years, but in this case it is the number of years since the Federal Trade Commission forced the audio industry to adopt the standard.
What has the Federal Trade Commission got to do with it? - it's not an 'American' Standard, and LONG predates the dates you suggested.
However, if American manufacturers used to make up their own standards it perhaps explains the laughable specifications on American equipment in the 70's
It looks like the Sylvania 2.1 amplified speaker system I showed did not violate the American rules by lying about 150 Watts when the system produces only 6W because it was ordered from China and I am sure they have an e-mail ordering a 150 Watts system.
Interesting topic here guys - I've been saying "RMS power" since forever without giving it a second thought; it seems I may have been wrong!
To try and get a clarification on the original question (as I understand it, at least) am I correct in saying we are all agreed that "Average Power" and "RMS Power" are the same thing. Even if the nomenclature is not correct, these two terms *don't* represent different measurements that might produce different results when carried out on the same piece of equipment?
Interesting topic here guys - I've been saying "RMS power" since forever without giving it a second thought; it seems I may have been wrong!
To try and get a clarification on the original question (as I understand it, at least) am I correct in saying we are all agreed that "Average Power" and "RMS Power" are the same thing. Even if the nomenclature is not correct, these two terms *don't* represent different measurements that might produce different results when carried out on the same piece of equipment?
Not at all, that's how it's always been (and still is), it allows you to accurately compare different systems, and to easily measure that the system meets the claimed specification.
I don't really see how 'average power' is at all useful?, unless of course it's simply a short term for something much longer that explains it? - like RMS power is.
So it's the actual power and so that means the actual heat generated by a load would be based on that measurement/calculation.
Which is EXACTLY what RMS power is - without the confusing mention of 'average'.
Which is EXACTLY what RMS power is - without the confusing mention of 'average'.
Ok Nigel,
How would you describe the power produced by the dotted box (or dissipated by the resistor) in this simple circuit?
Here is my (unambiquous) description of what I see:
With the 50% duty-cycle shown, the power dissipated by the resistor is 5W.
If the switch was closed 100% of the time, the power dissipated by the resistor is 10W.
The instantaneous peak power is 20W, as shown by the green trace.
Notice that I didn't mention RMS or Average....
Huh? It has everything to do with power measurement, unless, I guess, you are an audiophile...I wouldn't (in the context of this thread), as it has no bearing on it....
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