Talk:Crest factor

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[edit] Table re-organization

1. waveforms in table should be normalized to RMS, not peak. this is the normative normalization method.

2. since this article is about crest factor (peak to average factor), the relevant columns should be put closer to the beginning. i suggest this order:

waveform type, waveform plot, peak value, crest factor (linear), crest factor (dB)

RMS value of 1 is implied for all waveforms so it doesn't need to be a column.

non-relevant columns should be pushed to the end, or removed. right now they are at the center of the table, even though this is not an article about mean-rectifed magnitude, and waveform factor. (and waveform factor is not even related to crest factor/PAPR..)

3. all these mathematical derivations (square roots and ) are obscuring the main data. consider hiding them / moving them.

217.132.27.200 (talk) 21:19, 4 February 2008 (UTC)

let me correct myself re #2 - when waveforms are normalized to 1 RMS, the "peak value" column is equal to the "crest factor (linear)" column. so both columns should be merged into 1 column. this makes the table even simpler and more understandable.

I'm ready to do the corrections myself, but i would like some OK first so that some whimsical admin won't revert my work.

217.132.27.200 (talk) 21:23, 4 February 2008 (UTC)

[edit] Table

The table of the article is wrong.

The mean values of sine, triangle and square wave signals are all 0.

The values given are for (perfectly) rectified signals.

KjellElec

Yes. Also, the meaning of waveform factor is not explained. Omegatron 04:33, 21 October 2006 (UTC)
It appears to be the RMS divided by the mean, though I don't know how it is used. — Omegatron 07:52, 9 March 2007 (UTC)

[edit] Reformat

Please break up the table into individual images and editable math formulas in an HTML table. I'll do it if no one else does, but I don't have time right now. — Omegatron 19:38, 20 October 2006 (UTC)

The table should also be expanded to include Gaussian white noise, pink noise, compressed mastered CD audio, raw audio from a microphone, etc. etc. — Omegatron 19:59, 20 October 2006 (UTC)

Starting:

Image:Crest factor table.jpg

Wave type Waveform Mean value (rectified) Waveform factor RMS value Crest factor
Sine wave {2 \over \pi} \approx 0.637 {\pi \over 2 \sqrt{2}} \approx 1.11 {1 \over \sqrt{2}} \approx 0.707 \sqrt{2} \approx 1.414
Half-wave rectified sine {1 \over \pi} \approx 0.318 {\pi \over 2} \approx 1.571 {1 \over 2} = 0.5 2
Full-wave rectified sine {2 \over \pi} \approx 0.637 {\pi \over 2 \sqrt{2}} \approx 1.11 {1 \over \sqrt{2}} \approx 0.707 \sqrt{2} \approx 1.414
Triangle wave {1 \over 2} = 0.5 {2 \over \sqrt{3}} \approx 1.155 {1 \over \sqrt{3}} \approx 0.577 \sqrt{3} \approx 1.732
Sawtooth wave {1 \over 2} = 0.5 ? ? ?
Square wave 1 1 1 1

Obviously we should create dedicated images. These are just placeholders. Omegatron 04:12, 21 October 2006 (UTC)

I created better images and they are now in the article and here. — Omegatron 05:05, 9 March 2007 (UTC)

http://www.dliengineering.com/downloads/crest%20factor.pdf

I think we should more clearly discuss the mean values are obtained by rectification. At a quick-glance, these values seem incorrect, though they are just rectified.

What do you mean? — Omegatron 05:05, 9 March 2007 (UTC)

Waveform factor is the ratio of DC average to RMS and is used to scale resistors for measurements with DC or AC meters. The waveform factor for the half wave rectified sine wave should be 2.22 as the DC average is VP/Pi. —Preceding unsigned comment added by 212.77.217.195 (talk) 11:32, 26 September 2007 (UTC)

[edit] Peak Value?

Suppose we have a waveform whose peak values are asymmetric. That is, the magnitude of the negative peak is different from the magnitude of the positive peak. Which peak is used when calculating crest factor: the higher or lower magnitude? Or should the average of the peak magnitudes be used?

65.161.52.184 21:22, 18 December 2006 (UTC) Scott L.

The higher value would be used. — Omegatron 05:05, 9 March 2007 (UTC)

[edit] Crest factor vs PAR

The source I am reading says that PAR is "identical to the traditional crest factor", implying that crest factor is an older term. — Omegatron 04:19, 26 July 2007 (UTC)

I still hear the term crest factor used all the time. Much more, in fact, than PAR