difference between placing not placing ground in multisim

[fm101]

Hello,

what is the difference between placing ground and not placing ground in multsim as shown in the figure. circuit with and without ground gives different voltages and currents.

thank you

 

[FvM]

Some simulators have even problems with convergence of floating circuits, Multisim apparently hasn't, it's still givving reasonable currents, identical between both cases. Absolute voltage levels can't be the same without ground, isn't it?

It looks like Multisim solves the floating circuit problem by adding a small conductance from each circuit node to ground.

 

[wwfeldman]

remember that voltage is always measured across two points.

placing the ground, as on the left, provides the software with a user defined voltage at some point.
the software has a reference and all other voltages are then relative to that

not placing the ground, as on the right, means there is no point with a user defined voltage.
you are then at the mercy of whatever the software does.

 

[fm101]

actually, i should have put picture with different image, the two circuit are on different pages, not on the same sheet but the picture shows as if they were sharing the same sheet....