wrote in message
oups.com...
On Aug 15, 9:33 pm, "Phil Allison" wrote:


I have a 5V and a 12V power supply. Both have a N, L, Ground
connections for the AC side. Both also have a V- and V+ connection.
Measuring between V- and V+ I get the correct voltages, i.e. 5V and
12V. Measuring between ground (AC side) and V- on both the 5V and 12V
gives 0V.

** Use a * ohm * meter to check for continuity.

Bet the 5 volt one has no connection from AC ground to the DC output.

Most simple PSUs have the DC output "floating" ie not connected to
safety
ground.

So if both the 12V and 5V need the same reference then could I connect
V- on the 5V PS and the V- on the 12V PS and the ground on the AC side
of the 12V PS all together? Are there any safety issues with this?

Thanks

There should not be any issues with this - safety or otherwise. As Phil
says, output ground is often floating, but just as commonly, if the power
supply has a metal enclosure, it will have an AC-side safety ground, and the
output ground will likely be tied to it.

Arfa