powersys
Advanced Member level 1
Recently I found out some noise, at about 100Hz, on the scope when I placed the probe of Channel-1 to one end of a coil and the GND-probe to another end of the coil. Before that I did not have such noise problem, which has been haunting me since few weeks ago. When I did FFT of the measured scope data, I found out several spikes at multiple frequencies of 100Hz (e.g. 100Hz, 200Hz, 300Hz, 400Hz...).
Yesterday, I found out that the noise was 'caused' by fluorescent lamp equipped with electronic ballast. When I switched off the lamp, the noise disappeared, and the spikes in FFT spectrum disappeared as well. I could hear some audible noise produced by the fluorescent lamp. According to the technician, the lamp is equipped with 400Hz electronic ballast.
[1] Is it 'conducted' or 'radiated' EMI?
[2] Why are the frequencies at multiple of 100Hz? Since the electronic ballast operates at 400Hz, in my opinion, it should be at multiple of 400Hz, (e.g. 400Hz, 800Hz, 1200Hz...). Pls correct me if I'm wrong.
Thank you very much
Yesterday, I found out that the noise was 'caused' by fluorescent lamp equipped with electronic ballast. When I switched off the lamp, the noise disappeared, and the spikes in FFT spectrum disappeared as well. I could hear some audible noise produced by the fluorescent lamp. According to the technician, the lamp is equipped with 400Hz electronic ballast.
[1] Is it 'conducted' or 'radiated' EMI?
[2] Why are the frequencies at multiple of 100Hz? Since the electronic ballast operates at 400Hz, in my opinion, it should be at multiple of 400Hz, (e.g. 400Hz, 800Hz, 1200Hz...). Pls correct me if I'm wrong.
Thank you very much