ASI Power issue

Hello,All

Our company has one machine that installed ASI communication system .Total two segments,one repeater and two ASI powers.I measure the voltage between ASI+, - and grounding and found one power is around +-15V and another one is around+- 2~3V ,but the voltage between ASI+ and ASI- of both powers is around 30V. I can't understand it ,Could you help me ? Thanks!

I'm not familiar with ASI . . .
But my guess would be that one (or both) has a 'floating ground'.
As in it is not referenced to ground.
Poet.

AS-i spec is for +- ~15V from ground.

The second PSU is floating, and needs to be grounded. Without the grounding, you will see communication issues due to noise.

Thanks! You are right ! Ground of the PSU that Voltage is around 2~3 is floating.