Shielded wire
Moderators: JeffC, rdoherty, stieg, brentp
Shielded wire
Hi, is it possible to use wire with an external stainless steel shield or does it need to be the standard type with internal copper shield.
i have gone slightly mad.!!!!!!!!!!!!!!!!!!!!!!!!!!
OK i feel a little silly.
The cable in question is two core but it has a stainless steel braid (shield) instead of the foil. i suppose you could say it looks like a braided brake hose
But with a clear plastic/PVC coating on it.
I actually use it at work for internally fitted TDC/VR sensors but i work on industrial diesel engines so that's why the steel braid is needed.
I have checked and it is a proper shielded cable.
Is there a perticular resistance or a limit i should avoid.
I can post a picture if needed.
OK i feel a little silly.
The cable in question is two core but it has a stainless steel braid (shield) instead of the foil. i suppose you could say it looks like a braided brake hose
But with a clear plastic/PVC coating on it.
I actually use it at work for internally fitted TDC/VR sensors but i work on industrial diesel engines so that's why the steel braid is needed.
I have checked and it is a proper shielded cable.
Is there a perticular resistance or a limit i should avoid.
I can post a picture if needed.
There is no foolproof way of determining whether a shielded cable is absolutely required.
Very dependent on where the cable is in relation to other (radiating) cables & components, so it's a case of try it then fix it if there are suspected issues.
Even the big OEM's have to do it that way.
The braided shield mentioned is probably around 98% shielding, no problem on a diesel but possibly not good enough on an electrically noisy spark ignition engine.
A good source of very high grade cable is 'heavy duty stage environment audio' cable.
That's the stuff used on rock concert stages to interconnect sound gear. Built to withstand handling by a gorilla, very good double layer shielding, reasonably heavy cores with very good flexibility.
Most any large electronics house will have it as will your local DJ supplier.
Very dependent on where the cable is in relation to other (radiating) cables & components, so it's a case of try it then fix it if there are suspected issues.
Even the big OEM's have to do it that way.
The braided shield mentioned is probably around 98% shielding, no problem on a diesel but possibly not good enough on an electrically noisy spark ignition engine.
A good source of very high grade cable is 'heavy duty stage environment audio' cable.
That's the stuff used on rock concert stages to interconnect sound gear. Built to withstand handling by a gorilla, very good double layer shielding, reasonably heavy cores with very good flexibility.
Most any large electronics house will have it as will your local DJ supplier.
I've used a lightweight cable, foil shielding, 24ga conductor- originally used for wiring home automation applications. The temperature rating isn't super high, but if you run the cable past hot zones it should be sleeved regardless. It's worked very well for me.
We have a couple of large spools lying around, I've been considering selling off segments of it for a small fee.
Brent
We have a couple of large spools lying around, I've been considering selling off segments of it for a small fee.
Brent
Definitely not! Earthing both ends creates a ground loop which WILL give you grief.
Earth at the EDIS end to the SAME point the EDIS module and MJLJ are earthed to. Make it nice and solid, clean metal and all, then apply a SMALL amount of grease to all surfaces before bolting down tight.
There is silver-bearing grease around (for IC's in computers) and if you can get some it's excellent.
Earth at the EDIS end to the SAME point the EDIS module and MJLJ are earthed to. Make it nice and solid, clean metal and all, then apply a SMALL amount of grease to all surfaces before bolting down tight.
There is silver-bearing grease around (for IC's in computers) and if you can get some it's excellent.
In the context of the MJLJ+EDIS, the primary way to avoid ground loop problems is to ground everything (MJLJ, EDIS) to the same point on the car's chassis.
It is certainly appropriate to ground both ends of a shielded cable; take apart any shielded interconnect cable and you will see this. Again, if everything is properly grounded there will be no problem.
Here is one of many articles discussing Ground Loop issues.
http://en.wikipedia.org/wiki/Ground_loop_(electricity)
It is certainly appropriate to ground both ends of a shielded cable; take apart any shielded interconnect cable and you will see this. Again, if everything is properly grounded there will be no problem.
Here is one of many articles discussing Ground Loop issues.
http://en.wikipedia.org/wiki/Ground_loop_(electricity)
Quoting from the text on wikipedia (and it is almost identical to the solutions offered in my old study books):
"The first solution is to ensure that all metal chassis are interconnected, then to the electrical distribution system at one point. The next is to have shielded cables for the low currents, with the shield connected only at the source end. Another solution is to use isolation transformers, opto-isolators or baluns to avoid a direct electrical connection between the different grounds. However, bandwidth of such is of consideration. The better isolation transformers have grounded shields between the two sets of windings. In circuits having high frequencies, such as computer monitors, chokes are placed at the end of the cables just before the termination to the next appliance, eg: computer. These chokes are most often called ferrite core devices."
Do NOT earth at both ends! There is a good probability of differences in potential (particularly at RF) in a car.
If you feel that there may be an issue with stray RF on the shield (which there shouldn't be unless you run a high power transceiver like me) then on the sensor end install a .01uF 500V ceramic capacitor between the end of the shield and ground as close to the sensor connector as you can get.
For a full 'belt & braces' approach add a large ferrite bead over the cable at the EDIS end (salvaged from the data cable from a dead VGA monitor).
Given the relatively open weave of the shield braid pictured, try to route the cabling well away from spark plugs and leads, alternator etc. Other side of the engine block would be good.
Earth at the same point as EDIS and MJLJ and try the cable, it should be OK with good installation.
"The first solution is to ensure that all metal chassis are interconnected, then to the electrical distribution system at one point. The next is to have shielded cables for the low currents, with the shield connected only at the source end. Another solution is to use isolation transformers, opto-isolators or baluns to avoid a direct electrical connection between the different grounds. However, bandwidth of such is of consideration. The better isolation transformers have grounded shields between the two sets of windings. In circuits having high frequencies, such as computer monitors, chokes are placed at the end of the cables just before the termination to the next appliance, eg: computer. These chokes are most often called ferrite core devices."
Do NOT earth at both ends! There is a good probability of differences in potential (particularly at RF) in a car.
If you feel that there may be an issue with stray RF on the shield (which there shouldn't be unless you run a high power transceiver like me) then on the sensor end install a .01uF 500V ceramic capacitor between the end of the shield and ground as close to the sensor connector as you can get.
For a full 'belt & braces' approach add a large ferrite bead over the cable at the EDIS end (salvaged from the data cable from a dead VGA monitor).
Given the relatively open weave of the shield braid pictured, try to route the cabling well away from spark plugs and leads, alternator etc. Other side of the engine block would be good.
Earth at the same point as EDIS and MJLJ and try the cable, it should be OK with good installation.
I believe we may be talking about two different things. for the VR Sensor wire, obviously yes, do only shield at one end- the EDIS end- don't ground the sheild at the sensor end.
For the PIP and SAW signals going between the MJLJ and EDIS module: this should be shielded wire- and the shield should be grounded at least at one end- and if at both ends - even better, since the ground for both the EDIS and MJLJ should be grounded at the same location regardless.
To your point about grounding at the 'source' of the signal- the PIP and SAW are bi-directional, where the PIP source is the EDIS module and the SAW is the MJLJ. The analogy is exactly like a shielded interconnect- like a USB or serial cable where the shield is grounded at both ends.
For the PIP and SAW signals going between the MJLJ and EDIS module: this should be shielded wire- and the shield should be grounded at least at one end- and if at both ends - even better, since the ground for both the EDIS and MJLJ should be grounded at the same location regardless.
To your point about grounding at the 'source' of the signal- the PIP and SAW are bi-directional, where the PIP source is the EDIS module and the SAW is the MJLJ. The analogy is exactly like a shielded interconnect- like a USB or serial cable where the shield is grounded at both ends.