# Has control shielding requirements changed?



## kb1jb1 (Nov 11, 2017)

I noticed a lot of things are not built the way we are use to. QC is lacking especially post Covid.


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## oldsparky52 (Feb 25, 2020)

I'm not in the category of those you listed, but I was always taught like you and would also question what you saw. Bonding at both ends becomes a parallel ground path which I was taught is not good.


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## bill39 (Sep 4, 2009)

This same thing came up on the plctalk.net. See link below:




__





New Science: Ground both ends of instrumentation cable? - PLCS.net - Interactive Q & A


New Science: Ground both ends of instrumentation cable? LIVE PLC Questions And Answers



www.plctalk.net


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## just the cowboy (Sep 4, 2013)

bill39 said:


> This same thing came up on the plctalk.net. See link below:
> 
> 
> 
> ...


That is a good one and even they can't agree. My question goes even further by asking about multi point unintentional grounding.


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## emtnut (Mar 1, 2015)

Last I heard, drain grounded on ONE end only. 
It can cause ground loop current that can mess up the signal. Especially the 0-5 and 0-10 V signals.

One end also is all that is needed to shield from 60hz


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## JRaef (Mar 23, 2009)

Signal / communications cables, ground one end only.

*POWER* shielded cables should be grounded at* BOTH ends*. Different issues. For the signal/comm conductors, you are shielding them FROM external noise getting in. With power shielding, you are creating a Faraday cage around the conductors to keep the noise IN the cables.


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## just the cowboy (Sep 4, 2013)

JRaef said:


> Signal / communications cables, ground one end only.
> 
> *POWER* shielded cables should be grounded at* BOTH ends*. Different issues. For the signal/comm conductors, you are shielding them FROM external noise getting in. With power shielding, you are creating a Faraday cage around the conductors to keep the noise IN the cables.


Would you say if the are bundled with insulation and foil striped off and touching the panel at many spots they are NOT grounded at only one point.


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## JRaef (Mar 23, 2009)

just the cowboy said:


> Would you say if the are bundled with insulation and foil striped off and touching the panel at many spots they are NOT grounded at only one point.


I would consider that a risk for errors / failures in whatever it is.


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## MHElectric (Oct 14, 2011)

I’m not a controls guy either, but I did a lot of fire alarm work my first few years in the trade. We always pulled shielded cable, twisted the foil and ground wire together at every device, taped it back on the cable so it wouldn’t touch anything and it was landed in the fire alarm panel & the NAC boosters by Honeywell or Simplex.


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## bill39 (Sep 4, 2009)

IMO the electricians should follow the supplier’s drawings and not make this decision on their on. Write an RFI, email, or ask question in a meeting. Then wire according to that answer. Otherwise you will be chasing literal ghosts forever.


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## just the cowboy (Sep 4, 2013)

bill39 said:


> IMO the electricians should follow the supplier’s drawings and not make this decision on their on. Write an RFI, email, or ask question in a meeting. Then wire according to that answer. Otherwise you will be chasing literal ghosts forever.


100% agree, that is what I told the last installer. I also asked if he was going to cover the warranty since they may of just blown the manufacture one.


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## glen1971 (Oct 10, 2012)

just the cowboy said:


> Would you say if the are bundled with insulation and foil striped off and touching the panel at many spots they are NOT grounded at only one point.


I know if an issue arose in the future that was "inaccuracy" of a device, I know where I'd start looking first.


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## CMP (Oct 30, 2019)

Everyone knows its wrong, what you do about it will set a new standard.

Didn’t you have a bunch of controls reworked in the recent past that were improperly labeled?


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## just the cowboy (Sep 4, 2013)

glen1971 said:


> I know if an issue arose in the future that was "inaccuracy" of a device, I know where I'd start looking first.


Luckily I run all current loops so chances are small. If it was motion with encoders or 0-10 volts to drives it would be worse.


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## just the cowboy (Sep 4, 2013)

CMP said:


> Everyone knows its wrong, what you do about it will set a new standard.
> 
> Didn’t you have a bunch of controls reworked in the recent past that were improperly labeled?


Yep that it one of them 3000-4000 wires relabeled. On that job an engineering firm signed off if would not effect anything, I banned them for that.
This job is a pilot project job that I will not own for 3 years, but I told them I will not accept it upon turnover.

I am a great boss, but as a contractor don't BS me.

Cowboy


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## Mobius87 (May 20, 2019)

So the drain wires are only connected at 1 end, or both ends? 

It sounds like they are all terminated at the same END, but the issue is that they are touching each other and the enclosure before they make it to the ground POINT?

If so, I think the confusion here is between 'POINT' and 'END'. Do they need to terminate to the same point, or is it just that it needs to be at one end only?

What difference does it make if they are touching each other or the enclosure after they've been stripped out of the cable if they terminate at the same point? They are all at the same potential as each other and the enclosure, and any interference induced on the cable outside of the enclosure is still going to be pulled to ground.

I'm not a controls guy, but the issue I would have is that all of these cables are not shielded from interference within the enclosure. I would think any issue they would have at that point would be from this interference, not from the drain wires touching.


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## emtnut (Mar 1, 2015)

Think he means at the other end, the foil is dangling out and touching the cabinet. 

In the same panel I agree, it won't be an issue. But I'd never accept a panel like that. Looks like crap, and I'd fail it on workmanship ... jebus, if I wanted crap like that I'd get the Cable guy to terminate it


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## Mobius87 (May 20, 2019)

emtnut said:


> Think he means at the other end, the foil is dangling out and touching the cabinet.
> 
> In the same panel I agree, it won't be an issue. But I'd never accept a panel like that. Looks like crap, and I'd fail it on workmanship ... jebus, if I wanted crap like that I'd get the Cable guy to terminate it


The OP only says that the shields are bundled together at the control panel and then go to ground. Nothing about the other side? Also does't say if it is done neatly or not?

Sent from my SM-G991W using Tapatalk


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## joe-nwt (Mar 28, 2019)

I always ground the shields as close as possible in the panel and isolate the other end with heat shrink. I was told eons ago that the signal could only get dirty on that last inch or two of wire. Sometimes if there are enough shield wires to ground, I'll mount a small ground bar just above the panduit so the shield wires are short as well.

I'm not all up on the latest science of shielded wiring, but I haven't had any complaints in 35 years.


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## glen1971 (Oct 10, 2012)

I shake my head when I see where someone has opted to save 8 terminals and share a shield with 2 pairs in a 16 pair cable. PITA to slide everything down to do it right later on..


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## micromind (Aug 11, 2007)

This sounds a lot like some sort of an educated idiot engineer who is out to revolutionize the industry because he is so smart...........


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## mburtis (Sep 1, 2018)

So I'm curious if I am understanding this right. If all the shielded twisted pair cables come into the panel then are stripped and bundled and routed to a common point. What would really be the problem? Theoretically they are all connected to the enclosure ground reference whether they are connected to a common lug or through seperate terminals bonded to the enclosure. Connecting at 1 end I understand as the two ends may be in different locations and have different ground references, but if they are all connected to the same ground reference point what difference does it make. I'm considering the panel enclosure as a single ground reference point, is that inaccurate?


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## wiz1997 (Mar 30, 2021)

When I was doing instrumentation work in chemical plants and refineries, different plant engineers had different ideas.

One would land the shield in the instrument, the other would land the shield in the DCS.

I don't believe either could prove their method was correct.


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## Almost Retired (Sep 14, 2021)

i like the concept of grounding in the device and not the panel
A) it saves room and terminals in the panel
B) it will be easier to insulate/heat shrink everything all at once in one place with easily available power for the heat gun
C) it looks so much neater than drains and shields going where ever you send them


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## glen1971 (Oct 10, 2012)

Almost Retired said:


> i like the concept of grounding in the device and not the panel
> A) it saves room and terminals in the panel
> B) it will be easier to insulate/heat shrink everything all at once in one place with easily available power for the heat gun
> C) it looks so much neater than drains and shields going where ever you send them


Except the grounding at the PLC or DCS should be very good, and not so much at many analog devices in the field.


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## Almost Retired (Sep 14, 2021)

glen1971 said:


> Except the grounding at the PLC or DCS should be very good, and not so much at many analog devices in the field.


that is an excellent point, and it will be very easy to check grounding any time you are troubleshooting
but since all of the panels i have noticed are field grounded, it is too late to change conventions now

maybe this was the concept in the original post ?


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## paulengr (Oct 8, 2017)

JRaef said:


> Signal / communications cables, ground one end only.
> 
> *POWER* shielded cables should be grounded at* BOTH ends*. Different issues. For the signal/comm conductors, you are shielding them FROM external noise getting in. With power shielding, you are creating a Faraday cage around the conductors to keep the noise IN the cables.


In power cables the purpose of the shield is to control the amount of electrical stress in the insulation and to protect the cable against induced voltages that may create an overvoltage situation (keeping things out). Any noise control is purely inadvertent. If we were after noise control, we'd ground one end only just as with signal cables.









Shielding Of Power Cables


In shielding Of Power Cables rated over 2,000 volts, a conductor shield is required by indusby standards. The purpose of the semiconducting




electrical-engineering-portal.com





And it may not be just 60 Hz. Even in non-VFD cables quite often there are switching transients and the like that radiate all kinds of frequencies. Even a worn bearing can induce current harmonics that we actually use for diagnostic purposes. If a motor is not running in its magnetic center you get about a half dozen harmonics spaced 120 Hz apart.









A Closer Look at Air Gap Eccentricity


During operation, several stresses are brought to bear upon key components of the motor. An air gap eccentricity results in increasing these stresses during operation. A motor operated with an eccentric air gap results in increased mechanical vibration, accelerated insulation degradation due to...




reliabilityweb.com





You ground both ends of a shielded power cable for the simple fact that the foil shield impedance is intentionally not all that great in order to minimize losses in the cable. If the shield impedance is not maximized then you get huge losses in the cable where the power is capacitively coupled into the shield and you get a large current. Also standards require shield voltage to be 25 V maximum.



https://www.pesicc.org/iccWebSite/subcommittees/E/E04/2001/f2001_landinger.pdf


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## splatz (May 23, 2015)

If the shield / foil is not present in the panel, it could pick up noise inside the panel. In some panels, depending how the wire is routed, this might not be any big deal. If there are drives and starters in the panel, inside the panel might be the noisiest part of the run, especially if the field wiring is run in conduit. Also, if it's twisted pair wire, the wire maintains the twist better laid and packed inside the jacket as it was manufactured. So the jacket could be important even for unshielded twisted pair. 

If you stripped the jacket off romex or MC ten feet back from the box, so you could stuff it through smaller bore holes in the framing, everyone could see that's trash. Yes there are NEC articles that it would violate but even if there weren't, you're clearly not using the cable as intended. 

Regarding grounding one or both ends - if the instructions don't specify whether to ground one end or both ends, I ground one end of the drain wires. I ground them at the panel so it's easy to check the work. I don't want any unintentional ground loops running on itty bitty accidental equipotential bonds. If I have a problem, I'm not above grounding the other end to see if it fixes it and leaving it that way without understanding why. 

Regarding 4-20ma instead of 0-10V, 0-5V, etc. - I have never seen interference on 4-20ma. I have heard of induced voltages but not induced currents. The voltage on the loop doesn't have to be exact, the sensor figures it out and regulates to the right current. So I don't see how you could have interference on the signal wire skewing 4-20ma. 

I have never got an explanation that I could understand as to why the shield would function significantly better or worse grounded at one end or both ends. Very possible I got a valid explanation and didn't understand it but you'd think it would be simple enough to explain. If the shield will function better grounded, it's grounded when it's grounded at any point, right? 

I wouldn't think shields always need to be grounded to function. If you put your cell phone inside a 4" pipe nipple, put a threaded cap on both ends, set it on a on a wooden floor and call it, will it ring? But I have heard of people having a bad time with shielded UTP cables that failed to ground the shields, where they thought the shields were actually amplifying interference. 

One of the highest performing cables around is your cable TV, most work at gigaHz these days. The coax shield seems to be working pretty well, and it's typically grounded at multiple points - at the tap on the street, at the building entrance, at splitters if the ground wire is installed, at surge protectors, etc. Seems to work.


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## paulengr (Oct 8, 2017)

just the cowboy said:


> That is a good one and even they can't agree. My question goes even further by asking about multi point unintentional grounding.


There have been many cases of instrumentation signals having major problems, mostly signals getting swamped by 60 Hz power bleeding through, with unintentional grounding. Crazy stuff like plugging in a computer causes a signal to a PLC to stop working simply because they don't share grounds and plugging it in induces a ground loop through the serial ports.

In practice inherently multipoint grounding is going to exist. You can't reduce the impedances in the ground system to zero. So putting in huge 4" copper bus around the IT room and doing crazy stuff like that throughout the facility is an exercise in futility. What you can do is recognize that as much as possible, use isolated signal transmitters and receivers and differential signals such as RS-485 or better yet those with a low frequency notch or low voltage notch such as Ethernet, Arcnet, and 4-20 mA current loops as opposed to those that don't like voltage signals (0-5 V, 0-10 V, +/-10 V) and ground referenced communications (RS-232).

IEEE Green book (IEEE Standard 142) talks a lot about the engineering argument about power system and instrumentation grounding. You can get quite a bit of impedance by creating two entirely separate ground grids (separate ground rods) although the Earth is conductive and the separation isn't as much as you think, and there's quite a bit of expense in doing it, AND the entire purpose for isolation can be messed up if the voltages are actually that far apart (ground potential rise issues) and could cause arcing in the instrumentation, not a good thing. The alternative is that everyone shares a common Earth ground. That is the consensus right now whether we like it or not because NEC has mandated it by Code. So at least conceptually your ground starts at the inter-system bonding jumper or at the frame bonding to the instrumentation bus power and goes from there. So within a control panel we'd ground the power and panel together (power system and equipment grounding bus), and then we'd either run a separate jumper and supply an instrument ground or just make sure it's all low impedance.

But trying to extend that across the plant is ridiculous. So that's where differential systems come into play and the practice of grounding at one end only. I'm not a strictly "MUST GROUND AT PANEL" person. I like the idea of grounding at "main" panel. It's simple and convenient to figure out which end is grounded and often grounding at the instrument end is a royal pain. But sometimes you can't avoid grounding at one end for various reasons and that's when you may reverse this logic.

The common practice these days I've been seeing which is very convenient is to place grounding terminals right next to the signal terminals. The grounding terminals have a screw and teeth that make good electrical contact with the DIN rail that is naturally bonded to the backpanel, forming a very low impedance path to the ground connections to the power system.

Within the panel the goal is really just minimizing noise within the panel. There is a lot of ELECTRICAL noise with switching power supplies (VFD's, 24 VDC switching power supplies, etc.) generated just within an electrical panel itself. Why would you not try to shield everything as much as possible for as long as possible?


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## just the cowboy (Sep 4, 2013)

paulengr said:


> There have been many cases of instrumentation signals having major problems, mostly signals getting swamped by 60 Hz power bleeding through, with unintentional grounding. Crazy stuff like plugging in a computer causes a signal to a PLC to stop working simply because they don't share grounds and plugging it in induces a ground loop through the serial ports.
> 
> In practice inherently multipoint grounding is going to exist. You can't reduce the impedances in the ground system to zero. So putting in huge 4" copper bus around the IT room and doing crazy stuff like that throughout the facility is an exercise in futility. What you can do is recognize that as much as possible, use isolated signal transmitters and receivers and differential signals such as RS-485 or better yet those with a low frequency notch or low voltage notch such as Ethernet, Arcnet, and 4-20 mA current loops as opposed to those that don't like voltage signals (0-5 V, 0-10 V, +/-10 V) and ground referenced communications (RS-232).
> 
> ...


Thank you very much Paul, you are the type of engineer this trade needs. 
But I have to know " _Do you look this up or pull it out of your head_" 

Harvey


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## Almost Retired (Sep 14, 2021)

edit


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## oldsparky52 (Feb 25, 2020)

just the cowboy said:


> Thank you very much Paul, you are the type of engineer this trade needs.
> But I have to know " _Do you look this up or pull it out of your head_"
> 
> Harvey


My guess is he pulls it out of that brain of his. He seems to know a lot about a lot.


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## paulengr (Oct 8, 2017)

just the cowboy said:


> I have been in controls for 45 years and I am seeing a change in panels the way they land shields.
> I have always been taught and told shields only go to ground at one spot, and that should be at the end it is sourced at.
> Last big project they striped the insulation and foil off as the cables entered the panel bundled the together and ran around the panel to the terminal strip to be grounded. I brought it up and an engineer signed off on it saying " it is not right but it won't cause issues".
> I just went into another new panel by a completely different contractor and they did the same thing. His excuse was it is now due to insulation properties.
> ...


That's just weird and wrong. Not acceptable in my book. That's equivalent to just stripping a couple wires back and taping them together as a "connection". It's the sort of thing you might do in a class with low voltage/low power where it's all temporary connections and nobody cares if you actually tighten the screws or wire nuts on anything. You just spend more time trying to figure out what your lab experiment fails to work properly the first time. The shielded cables always have an internal bare ground wire in instrument cables. No reason to mess with the shield itself, just land the ground wire. What I don't like is turkeys who fail to provide a convenient place to land it nearby...equipment manufactures and panel builders. I've seen plenty of panels where they have an entire row of 4-20 mA terminal blocks but NO ground terminals AT ALL. And that includes equipment that comes that way.

As to stripping them all the way back, the entire panel in most modern panels is nothing but pure RFI. You've got PLC's and other controls with Gigahertz speed processors, switching power supplies, UPS's, and VFD's all running into Kilohertz speeds and noise, noise, noise. The manufacturers of those devices tell you to run the shielded cable right up to the terminal strip and even provide (never enough) grounding terminals specifically for the analog signals. Right in the instruction manuals it is pretty detailed on this point. This is completely unacceptable and I'd make them redo it all, no exceptions.

I can see where the practice gets started. With molded cables such as SO, tray cable, instrument cables, and NM, you connect it with some kind of gland/cord grip (well you are supposed to anyway) so the outer jacket just continues up into the box, even if it's minimal. With power cables (tray cable, SO, NM) practice at least in the past was to strip it back mostly because it made it more flexible and easier to route within a panel. No reason to do it other than trying to be neat and tidy. Within residential panels in the past I've seen it both ways but since the neutral now has to land on the breaker to make the GFCI/AFCI work, I can see where it makes more sense to leave the jacket on further into the panel. With conduit, liquidtight, MC, and gutters, the conductors are within a raceway that terminates at the panel. The jackets do not and can't continue up anywhere into the enclosure. So you can easily teach apprentices to just strip EVERYTHING back and that's what they do. You see a lot of jackleg stuff with conduits. Like mid-span stripping back a ground wire and looping one wire through all the grounding bushings. A lot of grounds get terminated right along with this jackleg conduit stuff, too. So this crap job sounds exactly like the same crowd of apprentices doing some jackleg thing just to save time.

The practice is simply WRONG with instrument cable though.

As to engineers putting this information on the drawings, REALLY? When is the last time you saw a physical layout drawing with anything more than terminal strips on them that might have labels if you are lucky? When is the last time you saw the panel shop actually follow the same drawing that they themselves drew out? Drawings and shop practice are almost never the same thing. And when is the last time you saw a detailed cable illustration telling you how to terminate a cable? How about this...ever seen a bid spec for an industrial job that specifically called out NM as NOT ACCEPTABLE? Electricians that do industrial jobs for a living know that two screw connectors and NM are NOT ACCEPTABLE. You don't need a drawing for this and you don't need to call it out. Professionals that do instrumentation work have been trained on shielding and you don't need to tell them not to cut the shields all the way back.

This is the same crowd where I've seen an electrician take a CAT 5 cable and strip back the insulation about 3 inches, untwist all the conductors and then carefully stick each of the conductors into the RJ45, then crimp it on with about 2-3 inches of untwisted cables and no jacket (so no strain relief) sticking out of it. Needless to say it failed to even achieve 100 Mbps.


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## joe-nwt (Mar 28, 2019)

oldsparky52 said:


> My guess is he pulls it out of that brain of his. He seems to know a lot *of stuff*.


Having trouble expressing yourself this morning?


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## oldsparky52 (Feb 25, 2020)

joe-nwt said:


> Having trouble expressing yourself this morning?


I thought I did okay, he knows a lot of stuff about a lot of stuff.  

Some people know a lot about some but Paul seems to know a lot about a lot. lol


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## mburtis (Sep 1, 2018)

My theory is that Paul is either one of the smartest people on this planet, at least pertaining to electrical, electronics, and computers….. or he is the world’s absolute king of bullshitting. Either way I always learn something when he posts even if I have to google most of it to understand it.


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## Jlarson (Jun 28, 2009)

We as a pretty hard rule maintain the jacket, shields and twist on instrument and VFD cables to as close the termination point as possible. All the shields go to ground blocks then at least on block from each din rail gets wired back to the main ground bar in the cabinet. 

Sometimes on refits especially and rail space it tight we'll pull the cables extra long so we can have extra shield drain wire from the terminations to a ground bar, that we often have to add because no one ever puts enough ground points, or neutral terms or even control power to pull from.


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## paulengr (Oct 8, 2017)

Jlarson said:


> We as a pretty hard rule maintain the jacket, shields and twist on instrument and VFD cables to as close the termination point as possible. All the shields go to ground blocks then at least on block from each din rail gets wired back to the main ground bar in the cabinet.
> 
> Sometimes on refits especially and rail space it tight we'll pull the cables extra long so we can have extra shield drain wire from the terminations to a ground bar, that we often have to add because no one ever puts enough ground points, or neutral terms or even control power to pull from.


When I build a panel it’s not a problem. It is vastly easier to avoid mistakes if you put the terminals in, in the order the cables are. So 4-20 mA is signal+, signal-, shield. Remember the panel builder is working in a well lit, dry comfortable room with the backpanel laud out. They’re paid a pretty low rate as electrical work goes. The guy in the field may have to be on his knees or laying on dirt or concrete with weather, bugs, and poor lighting, and costs a lot more per hour. Spend the extra $0.25 for the materials and 3 minutes of labor. Just stating the obvious.


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## EJPHI (May 7, 2008)

I'll join the discussion because I deal with this every day. I also ask job interview question on this topic.

Shielded differential pair where do you ground the shield?
1) Audio frequencies and below, you ground the shield at the source end.
WHY? A ground disturbance at the source end hits both pair members and the shield equally. So connecting the shield at that end makes the disturbance common and easily rejected
at the load end. Grounding the shield at the load end would be OK if you had PERFECT uniform coupling between the shield and the pair members. Since that is impossible, you go with tying the shield to ground at the source.
BUT WHERE AT THE SOURCE? You tie the shield to the return/ground connection of the driver to capture the essence of the common mode disturbance on the driver output.

2) At RF frequencies what do you do? Ground at both ends because you want a contiguous ground from the source to the load that will block out RF interference.
WHY? If you only ground at one end, you make the shield resonant at some RF frequency depending on the cable length. You are also more subject to shielding effectiveness or impedance.

BUT WHERE DO YOU MAKE THE SHIELD TERMINATION CONNECTIONS? At the source and load chassis so RF is screened out.

BUT WHAT ABOUT GROUND LOOPS? Yeah you get the potential for current flow on the shield and inductive/capacitive coupling introducing an imbalance which shows up as normal mode at the load. As above, the pair members are not uniformly coupled to the shield so you get common mode to normal conversion that is not rejected by the load side differential receiver. This can be mitigated with R or C in serieis with the shield on one end. You could also address the ground potential difference with massive copper bonding jumper$$$!



3) WHAT IS PERFECT? Nothing; its about trade-offs. You have 500 MHz radios and >1GHz cell phones in the real world. Plus long runs and "separately derived " systems that you have to monitor and control. 4-20 mA is excellent because the common mode noise gets reflected across the high current source output impedance as opposed to the load. Shielded twisted pair in ferrous conduit enjoys good 60 Hz magnetic field rejection from the conduit as long as you don't run power and signal in the same conduit. Capacitive/resistive connection from the shield to ground at one end can give you good good rejection of low and high frequency external interference.

It goes on from there. A couple of my favorite references:









Grounds for Grounding: A Circuit to System Handbook: Joffe, Elya B., Lock, Kai-Sang: 9780471660088: Amazon.com: Books


Grounds for Grounding: A Circuit to System Handbook [Joffe, Elya B., Lock, Kai-Sang] on Amazon.com. *FREE* shipping on qualifying offers. Grounds for Grounding: A Circuit to System Handbook



www.amazon.com













Noise Reduction Techniques in Electronic Systems, 2nd Edition: Ott, Henry W.: 9780471850687: Amazon.com: Books


Noise Reduction Techniques in Electronic Systems, 2nd Edition [Ott, Henry W.] on Amazon.com. *FREE* shipping on qualifying offers. Noise Reduction Techniques in Electronic Systems, 2nd Edition



www.amazon.com













Grounding and Shielding Techniques (IEEE Press), Morrison, Ralph, eBook - Amazon.com


Grounding and Shielding Techniques (IEEE Press) - Kindle edition by Morrison, Ralph. Download it once and read it on your Kindle device, PC, phones or tablets. Use features like bookmarks, note taking and highlighting while reading Grounding and Shielding Techniques (IEEE Press).



www.amazon.com


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## Peewee0413 (Oct 18, 2012)

joe-nwt said:


> I always ground the shields as close as possible in the panel and isolate the other end with heat shrink. I was told eons ago that the signal could only get dirty on that last inch or two of wire. Sometimes if there are enough shield wires to ground, I'll mount a small ground bar just above the panduit so the shield wires are short as well.
> 
> I'm not all up on the latest science of shielded wiring, but I haven't had any complaints in 35 years.


If we look at what causes interference, why grounding both ends can cause a loop, you'll realize that waiting long as possible to break off and ground is not a bad thing. Heat shrink is just added protection. I've done both with no interference. I generally have zero issues with 4-20, and take a few extra wiring precautions and routes with 0-10. Most of my 4-20 issues are with high frequencies near the device. Isolating a transducer from a tank via via uhmw or something usually fixes that though. 

Sent from my SM-S908U using Tapatalk


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## joe-nwt (Mar 28, 2019)

I treat all shielded wires the same, 4-20, 0-10, whatever. It's just how I roll.


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## splatz (May 23, 2015)

Peewee0413 said:


> Most of my 4-20 issues are with high frequencies near the device. Isolating a transducer from a tank via via uhmw or something usually fixes that though.


Do you think the interference is messing with the signal on the wire, or the device sensor itself?


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## Peewee0413 (Oct 18, 2012)

splatz said:


> Do you think the interference is messing with the signal on the wire, or the device sensor itself?


I am speaking of past experiences, and sometimes you isolate the tank from the sensor the reading changes. I have always made sure to monitor instruments at the time a motor turns on. If I see interference I track it down. First thing I do is test the tank or whatever it is for HF. 

Sent from my SM-S908U using Tapatalk


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