How To Check The Galvanic Isolation Of NI PXI and C Series Modules?

Issue Details

I would like to check the Galvanic isolation of NI PXI and C series modules but I could not locate it in the specification sheet. Do the modules comes with the isolation? How to know that the if module has Galvanic Isolation?

Solution

Galvanic and electrical isolation are generally the same thing. It means the i/o ground (channel) is isolated electrically (galvanically) from the earth ground (or chassis ground), it also means non-conductive isolation. In products this isolated is generally mentioned as the specified voltage that the isolation barrier can withstand. 

Galvanic isolation causes a lot of confusion in applications, as ‘galvanic’ refers to the electrochemical process where metals corrode when they experience electrical contact with an electrolyte. However, galvanic isolation blocks the electrical flow by communicating without a direct conduction path between the two isolated circuits.

So when the datasheet specifies 'channel to earth ground' isolation to a certain voltage say 250Vrms etc. It means it has electrical (or 'galvanic') isolation between all the channels or i/o to earth ground. 

However there is no electrical isolation between the channels, unless it also specifies channel to channel isolation.

Additional Information

Pay attention to the 'isolated' voltage limits as this determines how much you can 'float' the channel above that isolated ground.