Ok, I got my sheet of mumetal today, and did some work. My compassmot is 148%, so it's definitely needed, but I'm not at the stage of rebuilding my stack (nor do I see why I need to, since everything worked ok in 2.9.1). And some strangeness appeared....
My magfield was 380, with no mumetals.
When i slipped the corner of an A4 sized sheet of mumetal under the APM (shiny side down, sticky side up), the Magfield jumped to 695. I then placed the mumetal on top of the cage, around 4cm above the APM. Magfield dropped to 150. Hardly scientific, but interesting all the same.
I've since covered the entire bottom of the carrying plate for the APM, with the shiny side facing the PDB just below. Magfield was now 400.
It should be noted that the flight pack is not connected, so no power through the PDB. I connected the 6S to the PDB, and...nothing changed.
Hmm...I turned the quad 90' (turning it directly south in the process)...and it dropped to 360. I turned it back again...and it's up to 420.
I check the compass...and it's completely back to front!
So....I run a live compass calibration. And...
Magfield is now 252 facing North, 220 West, 270 South and 304 East. But at least it's pointing in the right direction on the compass!
What is going on??? And why should I have to care about this stuff...I just want to fly....:-(
Replies
Anything that stresses the material destroys it's properties. Hence most types of cutting, and bending. After forming, you have to heat treat it in a hydrogen atmosphere...
Alternatives are to use very thin foils, and be careful, with only gentle bends.
Companies who supply Mumetal, will usually re-anneal it for you, for a small fee.
It is possible to treat in other atmospheres, with only a small loss of efficacy's, but careful temperature control is essential.
Best Wishes
You do understand, that when you cut or bend mumetal, it has to be annealed again to restore it's properties....
Best Wishes