blueLog - RS485 Cables and wiring

    The following table shows the recommended cable types you should use for good communication quality in connection with meteocontrol dataloggers:

    Signal

    Device type

    Cable type

    Max Recommended length

    Bus cabling (RS485)

    Inverters, Current Sensors

    Li2YCYv (TP) 2×2×0.5 mm²

    1200 m

    Analog (0-10 V)

    Irradiance, Temperature sensor

    LiYCY 2×2x0.5 mm²

    100 m

    Analog (0-20 mA)

    Irradiance, Temperature sensor

    LiYCY 2×2x0.5 mm²

    200 m

    PT1000

    PT1000 temperature sensor

    LiYCY 1x2×0.5 mm²

    30 m

    Digital (S0- interface)

    Energy Meter, Remote Control System

    LiYCY 1x2×0.5 mm² /
    LiYCY 2x2×0.5 mm²

    10 m

    Ethernet (TCP / IP)

    Ethernet network devices

    CAT 5(e) / CAT 6

    100 m

    We recommend using the cable type UNITRONIC® Li2YCYv (TP) manufactured by Lapp Kabel, or an equivalent cable type. This cable is suitable for laying in soil.

    For cables exceeding the given length, the additional use of repeaters is necessary.

    Several separate cables of this length length require a hub.

    Data cables must be isolated from power cables in accordance with EN 50174-2 using metal cable supports.

    The cable shielding may only be grounded at one end of the connection.


    troubleshooting

    If the data logger reports the error that one or more inverters do not respond to the requests via the RS485 bus (e.g. loss of communication), a bus problem could occur. Since it is unlikely that several inverters will have a hardware defect at the same time, it can be assumed that this is a problem with the bus cabling.

    In order to localize the problem more precisely, the following information is important:

    • Cable type used
    • Cable lengths between the bus participants
    • Order of the bus participants
    • Points where the shield is grounded

    Typical problems with bus cabling:

    • lose clamping points
      Please check all points for loose connections
    • RS485 A/B swapped
      If RS485 A and B have been swapped over one or more times, this can result in either no inverter data being able to be recorded at all, or only specific ones.
    • Cable shield grounded at several points
      The cable shield must only be grounded at one end of the connection.
    • RS485 bus routed near live lines.
      Data cables must be insulated from power lines according to EN 50174-2 with metal cable trays.
    • Using an incorrect cable type
      Simple stranded wire -> cable is not twisted, this does not reduce interference and disturbs the signal.
      Unshielded cable -> even small external influences can disturb the signal.

      We recommend the following cable types:
      Li2YCYv (TP) 2×2×0.5mm
      CAT 6
    • Bus signal weak
      y setting the terminating resistor (terminator) and the resulting voltage drop, A critical limit WILL be undercut and no bus participant or not all will be found. To improve the situation, writing can be done with an additional hub or repeater, or the terminating resistor can be removed.
    • Bus connections with GND connection
      If, according to the inverter manufacturer, a GND signal is required in addition to Data A and Data B, this must be followed. There is no higher-level reference potential and there are disruptions in communication (at the latest when several inverters are connected).
      GND ≠ PE. The GND line used as reference potential must never be grounded. Otherwise the signal is disturbed from 5-10% WR power.

    Published