Understanding RMS vs. Absolute Value for Calculating Averages in Data Analysis

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Discussion Overview

The discussion centers around the differences between using Root Mean Square (RMS) and absolute value for calculating averages in data analysis, particularly in the context of alternating current (AC). Participants explore the implications of these methods on power consumption and the characteristics of waveforms.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants express confusion regarding why RMS is preferred over the arithmetic mean of absolute values for averaging data, particularly in AC contexts.
  • One participant clarifies that RMS current is not the same as average current, noting that RMS is the root of the average squared current.
  • Another participant highlights that RMS current is useful because it relates directly to power consumption.
  • It is noted that power depends on the square of the voltage, which influences the effectiveness of RMS in representing heating effects compared to average values.
  • Participants discuss specific numerical relationships, such as the average voltage of a sine wave being 0.637 times the peak value, while the RMS value is 0.707 times the peak value, emphasizing the significance of peak values in heating effects.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the preference for RMS versus absolute value for averaging. Multiple competing views are presented regarding their respective applications and implications.

Contextual Notes

The discussion reflects varying levels of understanding regarding the mathematical and physical principles underlying RMS and average calculations, with some assumptions about the relationship between voltage, current, and power remaining unaddressed.

gsingh2011
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I never really understood why using the Root Mean Square of negative data is the preferred method of finding the average of the data as opposed to taking the absolute value of the data and taking the average (arithmetic mean) of that. The example that recently made me wonder about this is alternating current. The RMS current is the maximum current divided by root two. But why isn't the average current simply the average value after taking the absolute value of the current?
 
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gsingh2011 said:
I never really understood why using the Root Mean Square of negative data is the preferred method of finding the average of the data as opposed to taking the absolute value of the data and taking the average (arithmetic mean) of that. The example that recently made me wonder about this is alternating current. The RMS current is the maximum current divided by root two. But why isn't the average current simply the average value after taking the absolute value of the current?


THe RMS current is not the average current, it is the root of the average squared current. You do not use RMS current/average current interchangeably, I believe (but hey I'm not a physicist/EE)
 
The RMS current is useful because it's directly related to the power consumption.
 
gsingh2011 said:
I never really understood why using the Root Mean Square of negative data is the preferred method of finding the average of the data as opposed to taking the absolute value of the data and taking the average (arithmetic mean) of that. The example that recently made me wonder about this is alternating current. The RMS current is the maximum current divided by root two. But why isn't the average current simply the average value after taking the absolute value of the current?

The difference is that power depends on the square of the voltage, not just the voltage.
The RMS voltage of a waveform is the DC voltage that would have the same heating effect as the this waveform.

So, the parts of the waveform that are twice as big as others have 4 times as much heating ability.

The average voltage of a sinewave (allowing for absolute values) is 0.637 times the peak value, but the RMS value is 0.707 times the peak value.
The difference between these values is due to the heating effect of the parts of the sinewave near the peak value.
 

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