I am using 50 Hz, DBD plasma for material treatment. I see that the current and the voltage signals are too noisy. What is the reason behind it? How can i eliminate this noise? How would such noisy peak result in the accurate calculation of electron density?
Can anybody suggest me in this regard?
Rajesh Prakash Guragain
Kathmandu University
Nepal
Rajesh Prakash Guragain - I think, you can either install a low pass filter with a cut-off of 50 Hz or do averaging/smoothing over a sufficiently large number of measurement curves. The oscillations in the current are quite low frequency, it might also be worthwhile to do a Fourier Transformation and see what the frequency actually is. This might lead to some insights about the origin of these oscillations.
Rajesh Prakash Guragain Ideally while recording discharge current signal you can change the sampling methodology by taking average of waveform in your instruments (I assume oscillascope). Even after doing this the spikes (or Noise as you stated) in discharge current waveform needs to be investigated in detail. In DBD the discharge is dominated by filamentary channels. After packing or placing material the discharge characteristics changes to surface+filamentary mode. Thus I belive these spikes or noise ( as you stated) are spikes in current due to filamentary discharge channels in your DBD reactor which could be due to inhomogeneous topology of electrodes you have employed in study.
Fluctuations in discharge current during a plasma discharge are common and generally depend on type of discharge mode, plasma impedance and impedance of generator along with the length of the leads used with generator. These fluctuations can be due to:
1. Impedance mismatch between generator and plasma results in reflection of enenrgy back to source. In such cases in coming and reflected signals form multiple harmonics of applied signals some times appearing as noise. A matching network is highly recommended in this case.
2. Filamentary discharge where rapid oscillations of space charge under applied pulsating voltage results in such type of discharge current signals.
3. Smaller leads used with oscilloscope.
Sufficiently longer leads not only separate the in coming and reflected signals but also reduce noise particularly at lower applied frequency.
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