Emerson 781S, Reference Manual

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NOTICE
IEEE 802.3 PoE gives protection from damaging a computer or another piece of
equipment
When using IEEE 802.3 PoE, one of the important new features of this standard is that PSE
devices have a test mechanism to protect connected incompatible devices from being
damaged. Only devices which have an authenticating characteristic based on the IEEE
802.3 standard, receive power via the Ethernet cable. To determine whether a PD is
connected, the input parameters are checked by the PSE. This method is called “Resistive
Power Discovery”. During the discovery process resistance, capacitance, and current are
checked
If the PSE detects a PD, it starts classification (i.e. determination of the power requirement
of the connected device). The PSE applies a small defined voltage to the power input of the
PD's and measures the resulting current. The PD is assigned to a power class based on the
value of the current. Only now the total voltage is supplied to the power input.
This sophisticated system prevents computers and other devices from being damaged
when connected to these cables.
PoE FAQs
What do I have to
do to order IEEE PoE
on a 1410S
Gateway? There is no specific option code for PoE. All 1410S Gateways have
PoE. The only configuration needed is to flip DIP switch 5. Turning
the switch “ON” means to disable PoE.
What is the
maximum Voltage
PoE PSE can source? Maximum voltage is normally 48 VDC; up to 25 Watts.
Can you do
redundant power
with PoE? Yes, as PoE becomes more popular many network appliance
(switch) providers are supplying innovative switches and other
hardware to create redundantly powered networks. Typically,
many switch suppliers offer switches that allow multiple power
inputs. Check your local switch supplier for available
configurations. Also, the Gateway will work with a local power
supply connected to the power input terminals of the Gateway
and as a PD with power coming over the Ethernet at the same
time. If both sources are present, the Gateway selects the local
power supply first. If the local power fails, the Gateway
automatically switches to Ethernet power. When the local power
is restored, the Gateway automatically returns to local power.
3.7 Verify operations
Operation is verified through the web interface by opening a web browser from any PC on
the host system network and entering the Gateway IP address or DHCP host name in the
address bar. If the Gateway has been connected and configured properly, the security alert
will be displayed followed by the log in screen. This will need to be done to both the
Wireless HART
®
and ISA100 networks.
Installing the Gateway Reference Manual
May 2020 00809-0600-4410
32 Emerson.com