I repaired a coertivity meter and when repaired the owner demonstrated what happened with the coertivity from metal if you bend it. The effect was big. He told me that was the reason you never should bend or dril mu-metal after its heat treatment. Thanks for an other interesting video
@@weinihao3632 I do not exactly know because part of the system was a black box (no schematics from those boxes) and known to be good. It is a 19" amplifier/controller/PSU and 3 external cabinets. One is a big extremely heavy cabinet on wheels (size dog-house) with a huge coil inside used to magnetize the sample. There is also a "probe" inside. As far as I know it is a small coil used to measure the remanent magnetic field (If I use the correct term ) In short, it generates a magnetic field and measures the BH curve of metal samples. The meter has several modes, the one they used gave a value in A/m (if I remember well) The company who owns it develops things like electric motors for third parties. Something very rare, they had schematics, so there was no need for reverse-enginering. (95% of what I have too repair (my day-job) has no schematics)
I did something a while back :D ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-l2YS1s6HxHU.html and ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-S27zk_Gj9nU.html
Sorry, isn't it the non-linearity of the diode that is causing all the noise? Just think of diode ring-mixer, where the high frequency mix products are actually wanted..
I guess that is a different way of looking at things - in the diode mixer, you start off with a sine wave and process it using the diode; with a switching converter, you start off with DC and chop it into bits using switches (either mosfets or diodes); it does not have to be a diode, it can be a mosfet and you will get the same amount of noise.
