How to properly ground a shielded cable from a servo driver ?

Hi guys,
I am looking for advice,
I have a 1kw ac servo motor. the encoder is connected to the driver and they work well. the driver reads the encoders position well.
when trying to read the encoder pulses from the driver to my arduino, i get a lot of noise, i.e, i get pulses even when the motor is not turning.
I tried to use different cables. I got a cat7 cable. and as per to the illustration hooked up the couples of twisted cables to each signal and ground (they are all grounded at the arduino side only).
1. Should the outer braid be soldered to the connector at the driver side?
2. Do i need to connect also the inner naked wire ?
3. Should I connect it to the earth ground ? This is what I understand from the illustration (down left "FG")
4. On the arduino side, should i connect the shield to the ground pin ?
5. Not all wires are connected, can this cause a problem ?
6. Should i connect the arduino ground with the 12v power supply (of the servo) ground ?

Thank you.
servo pinout.jpg

My guess is that you have the mains power wires (220/230 VAC) and the low level signal wires run in the same conduit or very close to each other. Most often--in my experience--electrical noise is induced from an AC source that is in close proximity to the low level signal wires. It is not good practice to mix power and low-level signal wires in the same conduit or raceway or lay them next to each other.

Another practice which is all too common is to ground both ends of shield drain wires. That is also very bad practice. Shield drain wires should be grounded at one end only. Your post mentions grounding them at the arduino side only, but the drawing shows them being grounded at the FG "terminal" on the drive end. The convention is that shield drain wires are to be grounded at the "control system" end of the wire, but for most applications it doesn't really make a difference if it's at the control system end or the other end (in this case, the drive end)--as long as the connection to ground is solid at the end where the shield is terminated.

Grounding any conductor, or drain wire, or shield drain wire, at both ends results in a "loop" through which induced currents can flow and cause problems with the signals which are supposed to be protected. Hence, convention--and good wiring practice--dictate that any low level signal wire or shield which is grounded only be grounded at one end. (It is common practice in many parts of the world to use armour-shielded wiring/cabling for mains power wires, and that both ends of the shielding are grounded--but that's very different from low-level signal wiring/cabling, very different. The grounding of mains shields is for safety, not to prevent electrical noise.)

I have never seen Ethernet cable pairs with individual shields and drain wires--I'm not saying they don't exist, I have just never seen or used them. Simply twisting pairs of wires does not provide a proper shield from induced signals (again--mostly from AC power wires which are too close to the signal wires). A shield is usually a foil "wrapper" around a twisted pair of wires, and the drain wire is a bare conductor/wire (uninsulated) which is in contact with the foil wrapper. The drain wire is used to ground one end of the foil shield (and a bare conductor/wire is because it's easier to terminate than a foil shield, which usually tears very easily). I have seen industrial Ethernet cables which have an overall shield (either a foil wrapper with a drain wire) or a woven sheath (usually of uninsulated stainless steel strands). The shield is terminated to a metal outer casing on the plug ends of the Ethernet cable, and the manufacturer usually makes sure that only one end of the cable's connections is grounded (very hard to do, but it can be done if the manufacturer provides all of the connected equipment as well as the cable).

>>EDIT<< I just found an article about widely available Cat 7 cabling--with BOTH individual shields (but seemingly no drain wires) AND an overall cable braided cable shield. So, while I haven't seen this myself, according to this particular article apparently it's become commonly available and widely recommended for new home/office/industrial construction. BUT, while the article I read shows shields for each pair, it DOES NOT show individual drain wires for each pair and shield. Further, the article states the maximum recommended cable length for Cat 6 is 100 meters, and Cat 7 was designed to be the standard for cable lengths over 100 meters. Pretty interesting; again, I haven't run into any of that in my work or personal life. Sorry for any confusion.

If you're using "standard" Ethernet cabling (which, by another name, is called UTP cabling: Unshielded, Twisted Pair cabling) which you can get from any electronics or computer shop (or just about any retailer these days, including grocery retailers!) the pairs will most likely NOT have individual shields and drains to ground. [See the EDIT note above.]

Finally, if you have an unused conductor in any twisted pair (and the other conductor is used for a signal or even a common wire), the convention is that the unused conductor should be grounded--at one end only.

Hope this helps! Although it may be difficult to find in your part of the world (though it can probably be obtained from an on-line source), I would recommend you find some TSP (Twisted, Shielded Pair) cabling. This will be a twisted pair, with a foil shield and drain wire, wrapped in an "plastic" outer covering. A very well-known manufacturer of this type of cabling is Belden, and lots of people refer to any TSP wire/cable as "Belden wire" (much like facial tissues are commonly referred to as "Kleenex" because a famous brand of facial tissues is Kleenex brand). Use a single TSP for each of the paired wire signals in your application, and ground the shield drain wire at ONE end only--making sure that the end which is ground is actually firmly connected to a proper ground (earth). I have even seen TSP wire/cable sold at some large hardware store chains, or hardware stores which sell to industrial users.