Phase difference measurement problem ???

[Adham]

Hello everyone

i am building a power factor corrector using Labview 7.1 and Multifunction DAQ MIO PCI 16 E-01 i am using two referenced channels to acquire the voltage and current waveforms of one phase. The amplitude and frquency readings of the singals is acqurate.

But concerning phase i am getting a VARIABLE phase difference although i tried to use the tone detection VI to get the phase of each one of the singals alone and tried the FFT cross power VI to get the phase difference between the signals.

Can anyone help in this please

Thank you
Adham

[rpursley8]

What kind of waveforms are you acquiring? Can you post an example of your code?

[Adham]

I am using the acquire analog waveform VI to get the current and voltage waveforms.

The difference between my case and the other posts conerning phase differnce in this forum is that they are getting an inaccurate or delayed reading while im my case i am getting a variable phase difference through the tone detection VI.

Thanks

[rpursley8]

Can you post a vi with an example of your voltage and current waveforms contained within it?

[rpursley8]

There could be many causes so I want to see what you have to try to narrow it down.

[MarcS]

Are you using a simultanous sampling data aquision card? You need to sample both channels at exactly the same time to measure power factor as you are measuring the phase difference between both channels.