Galvanic USB isolator

Most of our nodes are POE powered; but are not galvanically isolated from the LAN (power).

It is common (to prevent rust) to run POE at negative voltages; so the 'plus' is somewhat near 0 Volt/earth; and the 'minus' is 40-60Volt below earth. But laptops and other USB devices tend to be wired the other way round.

So it is essential to use a USB condom/galvenic separator when it is connected both to Ethernet and USB.

As otherwise there is a voltage delta of 48 or 2x72V between your devices and earth.

No need for expensive ones

They are relatively expensive; and as they are sometimes mandatory safety equipment when high (kilo) voltages are in use (220V is actually still classed as a low voltage). These easily go vor 150 Euro's and more.

However there is no need for that level of safety in our case; and as it happens - audiofiles worry about a similar issue; in their case the ground loops cause audio quality issues. So using these USB galvanic isolators (which can be had well under 15 euro) is a perfectly good solution.