[AMPS] RMS POWER
Billy Ward
billydeanward@hotmail.com
Fri, 29 Jun 2001 18:12:03 -0000
I do want to add one little thing. If you are doing a COMPLETE computation
of the RMS, you do use the 360 degrees. The formula starts with E sub 1 not
E sub Zero, That is the Square Root of the sum of the Squares of each
indivicual degree 1 through 360. Or of course you could use Zero through
379 and cover them all--HI.
Thanks for your help, Bill.
Billy
>From: William Fuqua <Wlfuqu00@pop.uky.edu>
>To: "Billy Ward" <billydeanward@hotmail.com>
>Subject: Re: [AMPS] RMS POWER
>Date: Fri, 29 Jun 2001 10:11:29 -0400
>
>You know, I was looking at the message I sent. All column date is
>scrambled. I guess I can't use TAB in emails .
>Must use spaces from now on.. My neat table is all jumbled and I am a bit
>surprised that people could make it out.
>
>73
>Bill wa4lav
>
>
>At 04:30 AM 6/29/01 +0000, you wrote:
>>Yeah, I guess your right Bill. ENOUGH! I have not made myself clear and
>>it is probably my fault. The below is standard stuff that I knew and have
>>been teaching for 30 years. It still does not answer my question. I will
>>re-group and later on, if I have not figured out what I am trying to
>>figure out, I will find a better way to ask the question.
>>
>>Billy
>>
>>
>>>From: William Fuqua <Wlfuqu00@pop.uky.edu>
>>>To: <amps@contesting.com>, <billydeanward@hotmail.com>
>>>Subject: [AMPS] RMS POWER
>>>Date: Thu, 28 Jun 2001 13:21:47 -0400
>>>
>>>OK enough...
>>>
>>>RMS has one meaning, definition or procedure if you want to call it that.
>>>
>>>R take square root
>>> of
>>>M the average (mean)
>>> of
>>>S the square of a number of data points
>>>
>>> It may look complicated as an equation or an integral expression
>>>(calculus)
>>>but it is SIMPLE!!!!
>>>
>>>For example...
>>>
>>>
>>>Take one cycle of a 1 volt sine wave and divide into at least 8 equally
>>>spaced points starting at zero degrees.
>>>Calculate instantaneous voltage, voltage squared and power into 50 ohms
>>>load at each point.
>>>Do not use 360 degrees because it is the same point as 0 degrees. You may
>>>do this for any number
>>>of full cycles and you may want to do this on a spread sheet for each
>>>degree (ie 360 points) or what ever.
>>>
>>>Phase Voltage Voltage Squared Power into 50 ohms
>>> Watts
>>>0 0 0 0
>>>45 .7071 .5 .01
>>>90 1 1 .02
>>>135 .7071 .5 .01
>>>180 0 0 0
>>>225 -.7071 .5 .01
>>>270 -1 1 .02
>>>335 -.7071 .5 .01
>>>
>>>totals 0 4 .08
>>>average of totals .5 .01
>>>Square Root of average .7071
>>>
>>>
>>>The RMS value of the signal is .7071 times the peak (1 Volt)= .7071
>>>volts GEE look at above bold and underlined.
>>>
>>>What is the power of this signal into a 50 ohm load?
>>>.7071 volts squared divided by 50 ohms= .01 watts Look again above at
>>>the average power bold.
>>>
>>>It is all very consistent with calculations using RMS voltage or
>>>Current and resistance and power.
>>>
>>>Now what happens when we take RMS of the Power??
>>>
>>>
>>>Phase Voltage Voltage Squared Power into 50 ohms Power
>>>Squared
>>> Watts
>>>0 0 0 0
>>> 0
>>>45 .7071 .5 .01
>>> .0001
>>>90 1 1 .02
>>> .0004
>>>135 .7071 .5 .01
>>> .0001
>>>180 0 0 0
>>> .0
>>>225 -.7071 .5 .01
>>> .0001
>>>270 -1 1 .02
>>> .0004
>>>335 -.7071 .5 .01
>>> .0001
>>>totals 0 4 .08
>>> .0012
>>>average of
>>>totals .5 .01
>>>.00015
>>>Square Root of
>>>average .7071
>>>0.01225 RMS power ?????
>>>
>>>OK above is your RMS power for what ever good it is....
>>>And it does not relate to any of the other numbers you may use such as
>>>voltage, current. resistance or power. But does give you 22.5% bigger
>>>number in this example.
>>>73
>>>Bill wa4lav
>>>
>>>
>>
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