Surge events, including ElectroStatic
Discharge (ESD) and lightning surges, are
common in many parts of the world,
especially during electrical storms. These
energy surges can damage electrical
equipment and lead to network down time.
Surge protectors help protect your printer
from down-time due to these surge events.
Figure 1. Serial Surge Protector
HOW SURGE EVENTS HAPPEN
In a normal equipment
environment there are reasonable threats
from Electrostatic Discharge (ESD) and
lightning transients which can cause
loss of data integrity and permanent
damage to equipment if not controlled.
ESD threats are generated
by personnel movement, which causes
triboelectric (rubbing causing a
separation of charge) charges to
accumulate on equipment or clothing and
then be discharged through hand or tool
"touch". This discharge can represent
several thousand volts at 10 to 30 amps
of current. There are two primary
threats from an ESD event. These are the
peak current of the discharge and the
resulting electromagnetic field. Should
the input to the device not be protected
from this ESD threat, as little as 100
milli-Joules can cause permanent failure
to a device at the silicon die level.
Lightning also can create
a large disturbance and delivery
destructive energy to the equipment.
These lightning events cause
differential voltages to develop as a
result of inductance in the protective
earth ground path to the equipment.
During a direct lightning strike it is
possible to measure peak currents into
the Kilo Amp range. These events can
occur both at the facility as well as
outside the facility along utility power
lines. When they occur on the power line
outside of the facility peak currents
can be extended in time due to the
additional inductance of the power line.
A normal event may be 10 usec zero to
peak, with a decay of 200 usec. These
currents are called longitudinal. The
surge protector will adequately prevent
this transient damage from occurring to
within the industry standards for
lightning protection devices.
EFT disturbances occur as
a result of arcing contacts in
electro-mechanical switches and relays
commonly found in an industrial
environment. The electro-mechanical
switches are used to connect and
disconnect inductive loads. Like ESD,
EFT can be especially fatal on data and
I/O lines. The fast rise time of the EFT
pulses demand similar protection as ESD
CONFIGURATIONS THAT ARE
SUBJECT TO SURGE EVENTS
There are several
hardware configurations and applications
that are more subject to damage from ESD
events. These configurations include the
Locations Subject to Electrical Storms-Any
location where electrical storms are common
is a good candidate site for surge
protection on the serial ports
Unshielded Cables-If unshielded
cables are used to connect to the serial
port, it is much more likely that electrical
discharges will be picked up by the cabling
and damage the serial port.
Long Cable Runs-The longer the cable,
the more susceptible it is to surge events,
even if the cable is shielded.
Outside Wiring-If the cable runs
outdoors, it is more susceptible to surge
Different Earth Grounds-If the router
and the device at the other end of the
serial cable are connected to different
earth grounds, then the cable can become a
conduit for current that equalizes different
Installations with Multiple Serial Port
Failures-If an installation has
experienced multiple serial port failures in
the past, it is a good candidate for surge
BEAGLE HARDWARE'S PROTECTION
In order to improve the
network reliability of installations
subject to surge events, Beagle Hardware
surge protector for Serial interfaces.
If a surge event (Lightning/ESD) is
coupled onto the cables that interface
with the serial interface card, energy
can couple into the transceivers on the
front end of the card. The addition of a
passive cable assembly (with internal
clamping circuitry) can prevent this
energy from damaging the transceivers on
the front end of the interface. When a
voltage over the normal operating levels
seen in the serial communication are
present on the front end of the
interface they are clamped to ground.
This protector attaches to printer end
of the cable. See Figure 2 for a diagram
of how to connect the surge protector.
How to Connect the Serial Line Surge
Table 1. Surge Protection Features
Full Signal Protection
Every signal is
protected from surge events.
Attaches Directly to the
maximum protection by having the
surge protection closest to the
device that needs protection.