- 14th November 2007, 08:28 #1

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## What is the difference between RMS and average current?

what is difference between RMS and average current?

after simulating, what should i see to measure current consumption?

till now, i'v checked the average current.

when can i use RMS value?

thanks in advance~!:D

- 14th November 2007, 08:28

- 14th November 2007, 10:50 #2

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## Re: BASIC

RMS current and voltage are mostly used in alternate current (AC) measurements.

If you try to calculate the simple average of an AC sinusoidal (or any other periodic) waveform (current or voltage) symetrical from ground, you will get the value zero, as the waveform is composed of positive and negative values, unless you take only one semi cycle (positive or negative alone).

But AC waveforms of current or voltage can generate power, so using RMS (root mean square) calculation, you can obtain a value relationed to power (V x I) without the cancellation of negative with positive values. The RMS value is the equivalent AC voltage or current that generates the same power of a DC voltage or current value.

When you squared (to 2nd power) the negative samples/values of the waveform, you turn them into positive values that are added to the positive squared samples. After that you divide by the number of samples and do the root square of the "averaged sum of squares" and obtain the RMS value (for sinusoidal waveform, RMS value is 70% of the peak value, and average value of one semi cycle is 63% of the peak value).

RMS calculation can be used also in measuring vibration or any other physic event that is variable. Obs. power is not measured in RMS, there is no the unit Wrms, as it does not make sense.

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- 14th November 2007, 10:50

- 17th November 2007, 13:11 #3

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## BASIC

which software of your simulation,different software is different

- 17th November 2007, 13:11

- 19th November 2007, 00:45 #4

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## BASIC

really?...I didnt know...

sim. sftware is hspice or hsim..and

i usually use awaves or sandwork waveview to see power.

- 19th November 2007, 16:43 #5

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## Re: BASIC

the average valure is the DC component in the AC signal, whereas the RMS is the effective value that would generate a heat through a resistor like DC.