Altimiter and backup altimiter differs above 5000m

Hi!

When I tested the cruise speeds in this thread: https://forums.eagle.ru/showthread.php?t=199853 I saw that the altitudes where not linear.

Did a new test with just the altitudes.

Started on ground and set both altimiters to 0m. (992 hPa)

Started and increased altitude.

They follow each other to 5000m then the backup altimiter speeds up.

At 10000m I had to set main altimiter to something like 1200 hPa to make them same.

Dive to ground level and then they need to be set at 992 to be the same again.

/illern.