Would it make a difference if I put, first the variable power supply and second a not variable power supply in series than the other way around (first not variable PSU and then variable PSU)? What would be preferred of not?

 

hi,
Are the two power supplies mains powered.?
E

 

hi,
Are the two power supplies mains powered.?
E

Yes, I'm from Europe. Just a power supply plunged in the wall

 

If they are transformer based AND the negative terminal is NOT connected to earth ground, then "yes"!

It doesn't make any difference the order of the supplies.

 

Are both supply outputs galvanically isolated from the mains inputs?

 

Are both supply outputs galvanically isolated from the mains inputs?

Clould you tell me in what case it would matter?

 

If both supplies had the same common (e.g. mains neutral or ground), connecting the two supplies in series would short out one supply.

 

Depends on the power supply, Suppose the supplies were 1000 V 0.1A. My crystal ball is broken.
Proably not. Suppose they are 12 v 10A; Maybe. Suppose they are ATX supplies - NO!

There is a specification on how far you can float instruments from ground. $1000V is probably too much. ATX power supply have the negative 12 connected to chassis ground. So no.