Raymarine RNS-8, Руководство пользователя, Страница: 38 / 66

Cable length in meters
(feet) Wire gauge in AWG
(mm
2
) for 12 V supply
Wire gauge in AWG
(mm
2
) for 24 V supply
24 (75) 14 (2.08 mm 2 ) 16 (1.31 mm 2 )
>32 (>100) 14 (2.08 mm 2 ) 16 (1.31 mm 2 )
Important:
Be aware that some products in your system (such as sonar modules)
can create voltage peaks at certain times, which may impact the voltage
available to other products during the peaks.
Important:
To ensure power cables (including any extension) are of a sufficient gauge,
ensure that there is a continuous
minimum voltage of 10.8 V dc at the end
of the cable where it enters the product’s power connector, even with a fully
flat battery at 11 V dc. (Do not assume that a flat battery is at 0 V dc. Due to
the discharge profile and internal chemistry of batteries, the current drops
much faster than the voltage. A “fully flat” battery still shows a positive
voltage, even if it doesn’t have enough current to power your device.)
10.5 Power cable drain wire connection
The power cable supplied with this product includes a dedicated drain wire
for connection to a vessel's Radio Frequency (RF) ground point (if available),
or the negative battery terminal.
The purpose of the drain wire is to drain excess voltage from the cable shield,
giving it a path to safety. The drain wire protects the cable's inner signal
conductors from electrical noise emitted by other cables and devices.
Although the drain wire is not intended to ground the product's internal
circuits, it's important that the drain wire is connected to the vessel’s common
RF ground point, which should be used for all equipment in your system.
If several items require grounding, the drain wires and dedicated ground
connections (if available) of all equipment should first be connected to a single
local point (e.g. within a distribution panel), and then this point connected via
an appropriately-rated conductor to the vessel's RF common ground point.
An RF ground point is typically a circuit with a very low-impedance signal at
Radio Frequency, connected to the sea via an electrode immersed in the sea,
or bonded to the inner side of the hull in an area that is underwater.
On vessels without an RF ground system , the drain wires and dedicated
ground connections (if available) of all equipment should be connected
directly to the vessel’s negative battery terminal.
The dc power system should be either:
• Negative grounded (“bonded”), with the negative battery terminal
connected to the vessel's RF ground.
• Floating, with neither battery terminal connected to the vessel's ground.
The preferred minimum requirement for the path to ground (bonded or
non-bonded) is via a flat tinned copper braid, with a 30 A rating or greater.
If this is not possible, an equivalent stranded wire conductor may be used,
rated as follows:
• for runs of <1 m (3.3 ft), use 6 mm2 (10 AWG) or greater.
• for runs of >1 m (3.3 ft), use 8 mm2 (8 AWG) or greater.
In any grounding system, always keep the length of connecting braid or
wires as short as possible.
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