Laundryman
Well-Known Member
Nearly finished my nmea 2000 backbone. Autopilot, Actisense and radio all have shield wires. Where is it best to connect them to please, or do I need em? Everything seems to work without ! Thanks. Alan
Shield, where to?
- Thread starter Laundryman
- Start date
coopec
N/A
You probably need an expert's advice like WilliamH et al. If they are shield wires then surely they must be connected to a ground plate or maybe the motor (which would ground through the propeller) Now where are all the experts?
Laundryman
Well-Known Member
My guess is, when there's a lack of response, it's because no one wants to admit that they too haven't bothered to connect. Being more of a spanner (or possibly hammer) type person, I understood the shield to be something to do with interference avoidance, corrupting sentences etc. so I'm out of my depth. Is it necessary please?
lw395
Well-Known Member
Shields in data cables should normally be connected to signal ground or chassis of the equipment, close to the connector.
It is sometimes best to only connect them at one end, generally the receive end.
Things will often work fine with the shields unconnected, but it gives better immumunity to interference and less chance of interfering with anything else.
That's general for any data wiring, not specific to NMEA 2000.
It is sometimes best to only connect them at one end, generally the receive end.
Things will often work fine with the shields unconnected, but it gives better immumunity to interference and less chance of interfering with anything else.
That's general for any data wiring, not specific to NMEA 2000.
Laundryman
Well-Known Member
Thank you. That's easier than I thought. I can get on with things now .
David2452
Well-Known Member
That's a bit difficult to reconcile, on an N2K bus both ends are receive and send, it should be grounded at the drain shield at the backbone power insertion point only and no other RF grounding is needed. NMEA 0183 shield cables should be grounded at the transmit (or talker) end only. I suspect Laundryman is close to the truth, but it is an easy thing to do so why not give everything the best chance of working as well as possible both now and in the future. BTW the NMEA0400 standard calls for the RF ground cable at a minimum 8 AWG, around 8.5mm2 so call it 10mm2, pretty beefy conductor.
charles_reed
Well-Known Member
Leave 'em unconnected until opinion comes to some form of consensus...
;-)
;-)
David2452
Well-Known Member
No need to wait for any further consensus, it has already been arrived at by a large panel of industry professionals over a number of years and thousands of successful installs, just use the NMEA0400 standard which I alluded in post #6, other methodology might well work in some cases, the standard will work in every case and give optimum results.
