Grounding; Figure 5 - Earthing - Elpro Technologies 915U-2 User Manual

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30006 Local Battery voltage (8-40V scaling)
30007 Local 24V loop voltage (8-40V scaling) – Internally generated +24V supply
used for analog loop supply. Maximum Current limit is 150mA
30008 115S Supply Voltage (8-40V scaling)
Floating Point Registers 38005 – 38008 also indicate the Supply voltage, Battery
Voltage, +24V Supply and 115S Supply voltages but in a voltage scale.
There are no dedicated discrete low voltage alarm indicators however each supply
voltage does have a High and a low Setpoint Status which can be used for this type of
alarm.
See section 0"Analog Inputs" for details on how to configure these alarms.

2.2.4 Grounding

To provide maximum surge and lightning protection each module should be effectively
earthed / grounded via a "GND" terminal on the module – this is to ensure that the
surge protection circuits inside the module are effective. The module should be
connected to the same common ground or earth point as the enclosure "earth" and the
antenna mast "earth".
The 915U-2 has a dedicated Earth connection screw on the bottom end plate next to
the Supply terminals. All EARTH wiring should be minimum 2mm² - 14 AWG
If using the 915U-2 with serial Expansion I/O modules then all expansion modules must
have a separate earth connection from the front terminal back to the common earth or
ground point. See Figure 5 below
PWR
RF
232
485
ELPRO
915U-2
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PWR PWR
OK OK
TX TX
RX RX
ELPRO ELPRO
115S-12 115S-12

Figure 5 - Earthing

915U-2 Wireless I/O
PWR
OK
TX
RX
ELPRO
115S-12
915U-2 Wireless I/O