If, by constant function, you mean a constant function with no time varying component the RMS has no relevance.For a constant function the mean value and the RMS value are identical. That does not allow you to say that one is correct and the other is not.
DC voltage drop
- Thread starter Jon1980
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Whether or not the value is relevant, the calculation can be made. And if the mean (in this case constant) value is relevant, perhaps anything else which always has the same value is just as relevant? :angel:
If by "has no relevance" you are trying to say that it is not needed because other measures give you the same information, then I cannot disagree. But that is not my definition of relevance.
I often find that my understanding of various measures or statistics is improved by lookiing at several edge cases where the result could be called trivial.
Carultch
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The RMS value still exists for a constant function, it is just that its value is the absolute value of the only function output. It still exists as a calculation you can do, it is just not usually necessary to specify RMS voltage for DC.
One reason you might want to know about RMS voltage in DC, is if there is distortion from high frequency components, power line carrier data, or noise. RMS simply is a special time average value that gives you the nominal value of DC as a positive number.
If it's DC there is no time average.
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If it is DC there is no need to take a time average and the value of the time average is trivial to calculate. That does not mean that there is no time average.
Your argument, to me, seems to be in the same boat as saying that there is no DC offset in a pure sine wave rather than that the DC offset is zero.
Same end result from both descriptions, but the measure, namely DC offset, exists whether you care about it or not.
That makes no sense to me.
Carultch
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The point is, the quantity still exists and can be calculated, whether there is a need for it or not.
For instance, what is the average of 3, 3, 3, 3, and 3? Carry out the definition of an average, and you get (3+3+3+3+3)/5 = 3. No surprise, the average value of this list equals the only value in this list. What is the RMS value in this same list? sqrt((3^2+3^2+3^2+3^2+3^2/5) = 3. Again, no surprise.
The RMS value of the list is 3, the average (arithmetic mean) value of the list is 3, and just about all measures of center you could conceive of, will give you 3. All trivial to calculate, because they equal the only value in the list. The same is true for a constant DC voltage.
Thank you for making my point so eruditely.
kwired
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Vehicle batteries are not "deep cycle" batteries. They can put out high currents but only for short time.
Typical alternator on a vehicle probably will not put out 2400 watts either, I think many higher rated ones top out around 1000 watts. A diesel truck may be the exception that is higher, but remember it was also designed to run items on the truck.
You may want to set this up to some deep cycle battery, and even if recharging from vehicle alternator remember it will basically have a duty cycle so to speak, and will not recover as fast as you can discharge.
ggunn
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Jeez, you guys will argue about anything, won't you? Slow news day?
But, what the hell; I''l play. My submission: there is no such thing as DC, just AC with period approaching infinite t.
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That's one way of complicating it...........Jeez, you guys will argue about anything, won't you? Slow news day?
But, what the hell; I''l play. My submission: there is no such thing as DC, just AC with period approaching infinite t.
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Another way of complicating it is that if you ever turn it on or off it is no longer DC but a (perhaps very long period) pulsed or step waveform. :angel:
Pulsed?
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You turn it on and then at any later time you turn it off. One pulse.
Or you turn it off and at any later time turn it on. One pulse in the opposite direction.
Silly me...........You turn it on and then at any later time you turn it off. One pulse.
Or you turn it off and at any later time turn it on. One pulse in the opposite direction.
ggunn
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drcampbell
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