Ferrite beads vs low-pass for noise filtering

[JohnnyVoxel]

Hello,

I have a system on a 24 VDC bus that I am trying to eliminate noise going to. An inverter on the bus is causing a periodic 41khz wave shown in the attachment. My first thought was installing a lowpass filter, but due to the high frequency I'm wondering if a simple ferrite bead would do the trick. Thanks for any insight.

-Johnny

[JohnnyVoxel]

Annnnd... I just realized I measured the wave wrong. My noob is showing

Should read 62.5khz

[floobydust]

Ferrite beads have little inductance and at low frequencies <100kHz they don't do much.
You can get some multi-turn ferrite beads, but you need more inductance, 10uH-1mH.

I would add an LC lowpass filter with a resistor across the inductor to dampen it. Don't chose values near the 62.5kHz or its harmonics to avoid resonance.
I have also used 1mH common-mode chokes on 24V vehicles, depending on the load current and the noise source, and if things don't need a direct ground.

[f5r5e5d]

yes, beads are orders of magnitude too low inductance to be effective at 60 kHz

need multiturn inductors and R, C to make a LP filter, or just R, C if your current draw isn't too high

[T3sl4co1l]

That's an awfully low frequency to be having a problem with.  Most analog circuits will ride through that just fine, for example.  Can you not simply...get better stuff? 

Tim

[Zero999]

That's an awfully low frequency to be having a problem with.  Most analog circuits will ride through that just fine, for example.  Can you not simply...get better stuff? 

Tim

I agree, it's unlikely it's a problem. He probably just put his 'scope on the +24V line, noticed the noise and worried about it causing interference.