Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Ferrite beads for EMC testing

DIAGO1000

Newbie level 4
Joined
Oct 21, 2019
Messages
7
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
59
I'm looking at the effect of ferrite bead on a pcb to improve Susepability when EMC testing.
Looking at the curves on the data sheets .
The peak resistance seems to be around the 2mhz range.
Does this mean the ferrite bead will filter out frequencys around this range ie the higher the resistance( and reactance) the better the filtering??
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
46,978
Helped
13,934
Reputation
28,116
Reaction score
12,574
Trophy points
1,393
Location
Bochum, Germany
Activity points
273,927
There are quite different types of ferrite beads, e.g. beads on leads, surface mount beads, chip beads, wound beads, with different impedance and frequency range and current rating. You should narrow down the range you are talking about.

Chip beads e.g. mostly have impedance maxima between 100 MHz and several GHz. Low MHz range would be rather expected for wound beads. Ferrite beads are usually inserted to increase the high frequency impedance of a connection wire or a circuit branch. They can be also part of low pass filters.
 

SunnySkyguy

Advanced Member level 5
Joined
Sep 26, 2007
Messages
6,734
Helped
1,673
Reputation
3,344
Reaction score
1,641
Trophy points
1,413
Location
Richmond Hill, ON, Canada
Activity points
50,685
I'm looking at the effect of ferrite bead on a pcb to improve Susepability when EMC testing.
Looking at the curves on the data sheets .
The peak resistance seems to be around the 2mhz range.
Does this mean the ferrite bead will filter out frequencys around this range ie the higher the resistance( and reactance) the better the filtering??
Attenuation is ratio of impedances with series path included with source.

Although your values are missing, if the load is capacitive or low impedance a high series peak will improve attenuation at this peak.

We can only guess how much without values.
 

DIAGO1000

Newbie level 4
Joined
Oct 21, 2019
Messages
7
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
59
Attenuation is ratio of impedances with series path included with source.

Although your values are missing, if the load is capacitive or low impedance a high series peak will improve attenuation at this peak.

We can only guess how much without values.
I am testing an output of a hall effect sensor using a wurth ferrite bead 742792662.
Testing to ISO11452-2 RF immunity,the immunity if 200Mz but passing at 400mhz upwards
 

volker@muehlhaus

Advanced Member level 5
Joined
Apr 11, 2014
Messages
2,483
Helped
976
Reputation
1,954
Reaction score
957
Trophy points
113
Activity points
14,708
If your load is high impedance, you better combine the ferrite bead with a shunt capacitor, to form a low pass filter.
 
  • Like
Reactions: FvM

    FvM

    points: 2
    Helpful Answer Positive Rating

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
46,978
Helped
13,934
Reputation
28,116
Reaction score
12,574
Trophy points
1,393
Location
Bochum, Germany
Activity points
273,927
I won't expect an UHF problem from your post #1 mentioning 2 MHz. If the problem is actually ferrite bead impedance > 200 MHz, you might refer to a HF ferrite bead like 742861210.

An additional shunt capacitor should be helpful too, as mentioned by Volker.
 

Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top