Here it is the pic:- background: the circuit which works ok- grey ferrite ring - which does not work (wired)- blue ferrite ring which does not workThe length of the wires in blue and grey cases were 80 cm and then 40 cm.The length of the wires in the white ferrite ring 30 cm.
intentionally very lossy.
Noise In, Heat OutRecall that ideal inductors and capacitors do not dissipate any energy; they merely store energy, either in a magnetic field (inductors) or an electric field (capacitors). A resistor, on the other hand, takes energy out of the circuit and dissipates it as heat. Ferrite beads, unlike inductors, are intentionally resistive at high frequencies. This is why the above plot has the red dotted line labeled "R"--from about 100 MHz to 1 GHz, the bead exhibits significant resistive impedance, not reactive impedance. Actually, some ferrite beads and ferrite-core inductors are almost identical in construction, except that the ferrite bead uses a more "lossy" ferrite material because the manufacturer wants the bead to dissipate rather than store high-frequency energy.But why belabor this point? We belabor for two reasons. First, you cannot truly understand a ferrite bead until you have adequately pondered this fundamental distinction between an inductor and a bead. Second, this "lossy" characteristic makes the ferrite bead especially suitable for noise suppression. Why? Inductance can lead to resonance and ringing when high-frequency noise energy stored in the inductor interacts with capacitance elsewhere in the circuit. As we saw in the previous articles, ringing can become seriously problematic even when we are dealing only with parasitic inductance. We don't want to exacerbate the resonance/ringing situation, and thus we opt for ferrite beads over inductors.
Another way to look at this is in terms of what the part is actually doing while in its inductive and resistive stages. Like other applications where there is an impedance mismatch with inductors, part of the introduced signal is reflected back to the source. This can provide some protection for sensitive devices on the other side of the ferrite bead, but also introduces an "L" into the circuitry and this can cause resonances and oscillations (ringing). So when the bead is still inductive in nature, part of the noise energy will be reflected and some percentage will pass through, depending on the inductance and impedance values.When the ferrite bead is in its resistive stage, the component behaves, as stated, like a resistor and therefore impedes the noise energy and absorbs this energy from the circuit and does so in the form of heat. Though constructed in an identical manner as some inductors, using the same processes, manufacturing lines and techniques, machinery and some of the same component materials, the ferrite bead uses a lossy ferrite material while an inductor utilizes a lower loss ferrite material. This is shown in curves of Figure 2.1008_F2_fig2Figure 2: Reflection vs. AbsorptionThis figure shows [μ''] which is used to reflect the behavior of the lossy ferrite bead material.
Where I can find similar info to compare totoid with rods ?