i face to high vibration at low frequency of planetary ring gear .this gear monitor by two proximity sensor by on line monitoring . frequency rang of on line monitoring system set (10-10k) HZ.at this frequency rang overall vibration is low and accept.but when i measure bu portable vibration analyzer with range of frequency set (0-10k)HZ, I find 6 hz with high amplitude vibration that increase overall vibration to trip .input speed of gearbox is 3000 rpm and out put set to 8000 rpm, so the ring gear rotate at 360 rpm(6 HZ). i suspect to ski slope FFT that i attach it but the instrument staff check the sensor by oscilloscope and find that 6 HZ frequency with high vibration and stable .we check other same sensor mounted on another gear box were ok .
does it related to rotational frequency of ring gear?
those this frequency and amplitude is real ? pls share your idea