Vaisala PTB330 - Manual (Page 39)

Chapter 3 _______________________________________________________________ Installation
VAISALA _______________________________________________________________________ 37
Galvanic Isolation for Output
If galvanic isolation of the power supply line from the output signals
is needed, the barometer can be ordered with optional output isolation
module. This module prevents harmful grounding loops.
NOTE Output isolation module is not needed when using the AC power
supply module.
Figure 21 Galvanic Power Isolation
Number refers to Figure 21 above:
1 = Power Supply module