Stranded aluminium wire sheath attached to ground?

Hey guys,

I have 2 electric fence monitors, both the same model, (user manual is attached) and they were assembled by another person. He has done them both slightly different. They both have a multi wired cable attached to the various inputs and outputs. This cable has 4 wires within it's sheath (each has their own insulation sheath). These are used for the inputs/outputs. It also has multiple, what I think is, aluminium, wires wrapped around the 4 input/output wires. These aluminium wires are, I think, for stopping interference.

The person who assembled the two electric fence monitors treated the aluminium wires different on each monitor. On monitor A, he cut them off at the point where the 4 input/output wires splay out to their unique connections (eg ground, Vs, etc). On monitor B, he twisted the aluminium wires together, put heat shrink around them, and connected them to ground.

What is the reasoning for setup he has on monitor B?

View attachment Users Manual for PTE0700 V2 (1).pdf

The mesh wire overbraid (as it's commonly called) is indeed for shielding (although its typically stainless steel, not aluminum). The purpose of all shielding is to provide signals that reach the shield with a low resistance path back to their sources. In the case of most hardware I've used overbraid on, it is connected to the chassis of the box. This is either done at the backshell for a connector (the overbraid is electrically bonded to the outer shell of the connector, then the shell of the connector is electrically bonded to the chassis of the box), or is done right next to the connector (overbraid is pulled together and a "pigtail" wire is attached to it; that short "pigtail" wire is then connected to the chassis of the box with a screw).

The reason for terminating/grounding a shield, choosing which end it's grounded on, and what its grounded to... that all depends on the signal environment and what you are trying to accomplish (keeps signals in, keep signals out, or both).

Generally speaking, you would tie the shield to the chassis of your box. That way, any signals from the outside world that reach the shield, travel up the overbraid to your chassis, which is connected to (earth) ground. The signals from the outside world should also be referenced to ground, so the (earth) ground provides the low resistance return path for the signal to get back to it's source. That's the basic theory, but it all can be adjusted, depending on what you are trying to accomplish with the shielding.

Unless the cable with the shields grounded passes close to an AC line, in which case grounding the shields would reduce hum pickup, I suspect the person installing the cables grounded the first one, then decided it was superfluous and didn't bother with the second one.