The feed-through capacitors or by-pass capacitors as well as EMI filters are used for the passage of power supply through a chassis or metal can (boxes) in order to filter out any RF noise that may cause problems if it arrives to the electronic circuit. They are also useful to not radiate RF signals outside the box that could cause interference with other external circuits.
These pass-through capacitors should not be confused with the RF pass-through zero capacity.
Bypass stand-off capacitors are not like feed-through that filter through a panel, they are a ground bypass used as support, they are mounted with a nut fixed on the panel, one end of the capacitor is connected to ground and the other is the connection lead.
RF ATTENUATION COMPARISON DIAGRAM OF SOME EMI FILTERS
We tested in our laboratory the real attenuation of some EMI filters from 9 KHz to 1 GHz, as it is clearly seen from the diagram the attenuation is remarkable. What distinguishes them from ordinary by-pass capacitors is the attenuation value that is high even at low/mid frequencies.
electronicRF PP-76-102-4.5H3.1
Spectrum Control Inc. SCI-9920-101AG
Tusonix / CTS 4400-089LF
Tusonix 4101-002
