Hi everyone,
I have a board working from 10kHz upwards and have been seei9ng microphonics whenever the chassis/box is vibrated/shocked. Working to get rid or at least seriously improve this I have so far changed all my capacitors in the signal path from ceramic X7Rs to tantalums (COGs not available in 10uF). This has made it much better, apart from a single key component, a transformer.
The transformer is an RM10 bobbin with two 3C90 ferrite halves clipped together. A test board with just the transformer on will product noise spikes on a spectrum analyser whenever it is shocked. I am trying gluing various parts of the structure and also considering mounting the PCB differently. One or all of these might fix the problem.
What I would like to know is what the mechanism is for the generated noise. The test board is not powered. I didn't think that ferrite was magnetic in itself, so that would rule out the ferrite moving relative to the coil. I suppose there is always the earths magnetic field...Can a ferrite generate a magnetic field under vibration?
Also, any tips generally would be welcome.
Thanks
James