I have a pwm that takes AC from the wall, and without an isolation transformer, turns it to a ~+-170V switching supply. I'm using the pwm to power a custom device (about 6ohms and 0.15H). The problem I'm having is that there is noise everywhere. Specifically I have a hall effect current sensor wired in the pwm power line going to the device. I hooked the sensor to a scope and can see the DC offset I was expecting clearly, but there is 22kHz noise (the switching freq.) that is about 100 times the DC signal. So I need to attenuate this
22kHz noise.The setup is pretty nasty right now, long untwisted wire leads from the pwm to the device, and the same from the sensor to the scope. Other than twisting wires, making them shorter, and adding shielding,.... what else can I do to eliminate the large 22kHz noise? I tried RC filters, with little improvement, would a LC work better? What about just wrapping the lines around a high permeability core? I am pretty good with math (book filter design and Laplace transforms), but lack a lot of practical knowledge and experience. Thanks for any suggestions.