Very quick check.
4. + 7,118760
6. - 7,117125
8. 0,00000005
11. + 7,118760
13. - 7,117800
unfortunately i have a lot of noise when measuring the negative voltage, almost 100 microvolt.
Positive reading is only about 5 microvolt noise...
My Meter was at the PREMA factory 6 months ago.
So it should have the latest firmware?
What are the readings on your meter ?
Regards
Joerg