What filter to apply for a 50 Hz signal

[hemalathagopal]

hello All,

We are acquiring input 240V,at 50Hz, 3 phase voltage thru voltage transducer and that is fed to NI Input DAQ card, NI USB 6210 using LabVIEW 2019

When we check in the program, we see that

Rphase is on AI0 channel -> perfectly sinusoidal on the graph

Yphase is on AI1 channel -> skewed

Bphase is on AI2 channel -> skewed

I put low pass filter butterworth order 3, now the waveforms are OK but Y and B phase amplitude has reduced.

What should be done for the correction, please let me know.

attached waveform screenshot here

actual waveform has all 3 phases same amplitude but Y phase, Bphase skewed.

Filtered waveform shows  clear waveform on R, Y B...But Y and B amplitude is lesser than Rph.

All phases connected to 3ph 240V input signal. 3 transducers also OK.

[Henrik_Volkers · Accepted solution]

By the picture my first two guess: voltage transducer maybe a transformer where one phase is also abused as power supply?  (saturation)

or

Depending where you measure and what (bad) powersupplies are hooked on the system ..maybe real signal ?

If you swap channel inputs does the signal shape follow or not?

You use a multiplexed input card. See spec  and Fig 1. All channels have the same (hopefully low) source impedance?

If you hook up a scope (even 2 channel), how does the signals looks like?

[Henrik_Volkers]

Thanks for the market solution 🙂

Are you willing to share the solution?  (Just curious 😄 )