Just got another APM 2.5 in the mail today. This one appears to have a piece of pink foam inside the case. My original APM 2.5 did not have this foam. Is this something new? Does it need to come out? If not, do I need a piece in my older APM 2.5?
Yes, the pink antistatic foam is supposed to be in the case between the pwb and the top of the case. If you want to, you can put a piece of pink antistatic foam of the same dimensions in your APM2.5 case that does not have the pink foam. However, if you disassemble the case, just make sure that you get the reset switch plastic extension put back correctly and do not over tighten the case screws so that they do not strip out.
Are you referring to the piece of pink foam that comes with the APM 2.5 case? If so then yes that piece of foam is important, it should rest on top of the barometer. Without it you could subject the barometer to wild changes in air-pressure as your attitude and speed changes, leading to some exciting moments especially when in any auto mode where the AP is attempting to maintain a specific altitude.
If you received a case without the piece of adhesive backed pink foam I would contact 3DR for a replacement or find a suitable piece of foam yourself.
I can't say for sure, just make sure the density is about the same and it must be non-conductive.
Thanks, I'll see what I can find.