NMEA 2000 inter conductor resistance

Discussion in 'OnBoard Electronics & Controls' started by Roly, Jul 24, 2017.

  1. Roly
    Joined: Jul 2005
    Posts: 508
    Likes: 23, Points: 18, Legacy Rep: 222
    Location: NZ

    Roly Senior Member

    Surprised that something so basic is so hard to find out...

    Greetings to all, long time since last visit.
    Hope all is well with you.


    NMEA 2000 inter conductor resistance/ impedance
    I am stuck with this problem and am lost on impedance. Too complex for me.
    I've tried on CF/SN but nobody seems to know.

    Problem:
    N2K network switching on & off owing to errors. Previously OK. Recently switched PB200
    at masthead owing to fault in device.

    Solution:
    Disconnect PB200 at last node an install terminating resistor to backbone.

    Checks:
    Check PB200 on known good drop-OK
    Check PB200 on PC -OK passes all self tests
    Install known alternate good device at masthead-same problem.
    Check isolated mast cable- all OK except for CanL & CanH to ground = approx 4M ohm[​IMG]
    Up mast and pull cable (with squirrel attached) to check for chaff- OK cable intacto
    Check a spare 6m version of cable for resistance between CanL, CanH & ground -O/load....not 4Mohms

    Is this my problem?
    Would there be a difference of inter conductor resistance from a 6m to 15m cable?
    Would 4Mohms to ground corrupt the Canl CanH data integrity?
    I suspect...yes, no & yes.
    I have emailed Airmar. Not holding my breath
     
  2. Roly
    Joined: Jul 2005
    Posts: 508
    Likes: 23, Points: 18, Legacy Rep: 222
    Location: NZ

    Roly Senior Member

    Solved.
    I pared the rubber plug carefully off the cable at PB200 end and found the liquid dielectric rubber had voids around the solder connections. The ground wire was very close to the CanH. I separated them a little and retested- bingo, O/L.
    Now to remold a waterproof plug to fit the PB200.
    I am confident that this will stop the rapid switching of the network.
    Bravo Airmar.
     
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