type of ferrite bead used in multimeters?

[ftransform]

So I was watching the 2015 teardown and dave pointed out the ferrite bead. Does anyone know what the ferrite bead material used there is?

[c4757p]

Ferrite? 

[ftransform]

Ferrite? 

there are many different grades with different impedances at different frequencies. I assumed the one that is used in a 6.5 digit meter will have a high attenuation of lower frequencies, to remove hf rectification errors.

[ignator]

Ferrite? 

there are many different grades with different impedances at different frequencies. I assumed the one that is used in a 6.5 digit meter will have a high attenuation of lower frequencies, to remove hf rectification errors.

I'm going to guess that it's type 43.  Very common material to use, and kicks in around 20MHz.
My assumption is these ferrites were added after the original design for RE/CE compliance.  Those long wires are real good antennas at picking of the internal clocks, and spraying this out to connected test wiring.  The ferrite does a pretty good job of dissipating the RF on the wires as heat.  I'm not aware of any regulatory reason to have them as input filters, but they serve that function also.

[notsob]

W2AEW did a youtube tutorial on this subjext

[ignator]

W2AEW did a youtube tutorial on this subjext

Thanks, now I have another site to spend time learning from.
I'm not a RF guy (on purpose radio wave design, but digital/analog that had to work in that environment), and spent most of my career doing shake-bake testing.  Ferrite's were used both to make the product robust to RS/CS, as well fix RE/CE.

[ftransform]

this is why you should consider a ferrite bead for things other then EMI compliance. I suspect that keithley did this for this reason. Is there any ferrite that kicks in lower then 20MHz? Important for DC precision.
 
http://www.analog.com/static/imported-files/tutorials/MT-096.pdf