calculate DDR power captured from DAQ

[kmc2005]

Hi All,

So I have a DAQ connected to my development board, which provides me with the DDR current output.  As you can see in the picture, it almost looks like a square waveform.  Currently, I get the average number to calculate the DDR power but it does not seem right.  Any suggestions on how to go about calculating the DDR power so that it accurately represent the amount of power consumed by the DDR?  

Thank you.

[Gregory]

There are no units on your graph, but you say it is current so I will assume it is in Amps. I also see "1.2V Power" so you should be able to multiply the current by 1.2V to get your result in Watts. The average definitely looks plausible, why do you think it is incorrect?

[GerdW]

Hi kmc,

which provides me with the DDR current output

The max/min/avg values are given in "Watts", so I assume you get a "power output" and not a "current output"…

As you can see in the picture, it almost looks like a square waveform

Well, a square with 4 (main) levels… 😄

I get the average number to calculate the DDR power but it does not seem right

Yes, you get an average value.

But why doesn't seems to be right? what do you expect instead?

And as you already get "Watts" you don't need to calculate any "power" values!

how to go about calculating the DDR power

Again: your images shows "Watts" already, so what do you want to calculate?

so that it accurately represent the amount of power consumed by the DDR?

What means "accurately"?

What means "amount of power consumed"? Do you want to calculate an energy instead?

Please use units in scientific graphs! (And use SI units for international audience! :D)

Please use correct names of your measurement signals!

[kmc2005]

Yes.  The current is in Amps and I did multiple the voltage to get the Power (Watts).  The reason I feel like it's not very accurate is because of the swing of the mininum value to the max value, the difference is too big that I'm afraid the number might not be very accurate.  So I am just wondering if there are other methods to get the power more accurately.  Thanks.

[AnalogKid2DigitalMan]

Have you tried calculating power by using the RMS values of voltage and current?

http://www.eznec.com/Amateur/RMS_Power.pdf

-AK2DM

[kmc2005]

I did think about using RMS to do the calculation.  However, I only have the base version of LabVIEW so I don't have the RMS VIs to try it out and see if that would be better or not.  Do you know an open source VI for calculating RMS that I can try?  Thanks.

[GerdW]

Hi kmc,

do you know the meaning of "RMS"? Root mean square…

Even with a base version you have all function you need to calculate RMS values!

[RTSLVU]

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@kmc2005 wrote:

I did think about using RMS to do the calculation.  However, I only have the base version of LabVIEW so I don't have the RMS VIs to try it out and see if that would be better or not.  Do you know an open source VI for calculating RMS that I can try?  Thanks.

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Also remember that Amps*Volts in an AC circuit gives you Volt Amperes (Apparent Power) not Watts (True Power). 

You need to figure in the power factor (Amps*Volts*pf) to get true power.