Phase Shift and Power Spectrum..

[rpursley8]

Power is proportional to the square of the voltage, so the FFT plots will reflect this.

[tbob]

Usually the two terms are used interchangeably.  To get real technical, power is measured in either watts (linear scale) or dB (log scale).  Amplitude can be expressed in volts or dBV.  But generally, power and amplitude mean the same when it comes to transmitted signals.  Pay attention to the units of measurement instead.  There are probably mixed opinions on the use of power vs amplitude.

[gokul_bits]

Hi..

I am now actually implememnting a instrument in which i need to get the signal at DC.. So I saw another implememntation in which one has used a filter (chebyshev, inv. chebyshev etc..) to filtewr out the signals beyond 0.75 Hz and then he has taken the rolling average of all the remaining values.. Instead of that can I take the Amplitude Spectrum of the resulting signal and then take the value at DC using the extract portion VI in LabVIEW.. And if I do tht I need not multiply by sqrt (2) right.. Or should I multiply??

Thank U.

Gokul..

[gokul_bits]

Hi.. Someone out there.. please help me out.. please reply to the above question...

Thnx..

Gokul.

[Reddy]

hey gokul

you follow that filtering and rolling average method. that will be efficient.

Anil

[gokul_bits]

anil.. thnx a lot.. but can u explain me y the other method is not efficient..??

[gokul_bits]

plz... help me.. answer to the above question..

[gokul_bits]

Hi.. When i used a low pass filter I am getting results only when the low pass freq is below 0.5 Hz.. Above tht I am not getting any answer.. why is it so..?

Message Edited by gokul_bits on 06-22-2006 04:31 AM

[rpursley8]

You do not have the sampling frequency input wired so it defaults to 1 Hz.  Due to Nyquist limitations, the highest frequency you can filter is a little less than 0.5 Hz.

[Reddy]

Hi Gokul

yesterday this site was giving some problem here, so i could not reply to you...

Just check out "Extract portion of the signal", there you can not mention frequency. you can mention the no.of samples or time period. So it is better to go with filter which remove the signal above 0.75Hz to get DC signal........

But i have one doubt over here.......Where from this signal is coming. i mean are you getting this from outside or you are simulating it in the software...To get DC signal you can use Express VI also i think........Just let me know what exactly you are doing...so that i can give some sort of solution to you.

Regards

Anil