Amazon could do a much better job at accepting customer feedback. I understand they have to deal with clickspam, but at this point, you probably cannot leave feedback with any links in them.
Case in point: I was on a lark buying a cheapo set of Yohii Toroid Ferrite Cores Green Inductor Coils Ferrite Ring Toroid - 100pcs. They turned out OK, but the listing has no specs other than dimensions, which isn’t really that useful for most purposes. You want to know what material it is and which inductance it will have.
This is what I wrote (more or less, since amazon just deleted the comment so I can’t see what I wrote:
Seems OK but you need to publish specs
I was buying these on a lark, given the low price and having time to experiment.
I measured these as 10.5mm OD, 5.8mm ID, and 5.5mm height.
It's not clear what material these are made of (ferrite proper or sintered iron powder.)
I thus wound 30 windings of 0.5mm magnet wire around one and measured
inductance with a cheap LCR meter as 1730uH. That would make a relative
permeability of about 2800, according to
https://www.changpuak.ch/electronics/amidon_toroid_calculator.phpSince Amazon does not want the comment, I leave it here :) I should also let the seller know to update their product page.
Written on August 10, 2020