67 milliamperes for 3 seconds
AVOIDING ELECTRIC SHOCK
The three basic ways to prevent yourself from
receiving an electric shock can be summed up in three
words: isolate, insulate, and ground.
1. Isolate: Isolate yourself from the source of
electric shock. Make sure you secure the power to
equipment before you attempt to remove it. And, make
sure all electrical equipment covers, doors, and
enclosures are kept in place when youre not actually
working on the equipment. If you must leave live
circuitry exposed, rope off the area, post appropriate
signs, and warn your fellow workers of the danger.
2. Insulate: Make sure the electrical tools and
equipment you use are properly insulated. Use only
insulated hand and portable electric power tools.
Frequently check power and extension cords for
deterioration, cracks, or breaks. Breaks in the insulation
of power and extension cords cause many electrical
3. Ground: Electric current always follows the
path of least resistance. To prevent yourself from being
the unintentional path to ground, make sure your
equipment is well grounded. This will direct any stray
electric current to ground, thereby protecting you from
electric shock. A good ground could also protect your
equipment from excessive voltage spikes or lightning.
For further information on equipment grounding, see
Shipboard Bonding, Grounding, and Other Techniques
for Electromagnetic Compatibility and Safety, MIL-
RESCUING VICTIMS OF
The first thing to do when you see someone being
shocked is to secure the power. DO NOT touch a vic-
tim who is in contact with a live circuit, or youll be
shocked too. If you cannot secure the power, use a dry
insulating material like a rope, a belt (without the
buckle), or a wooden cane to remove the victim (by
pulling, pushing, or rolling) from the live circuit or
wire. Then, immediately call for medical personnel.
If the victim is unconscious AND you are certified
to administer cardiopulmonary resuscitation (CPR),
begin to do so.
The effects of the electric shock can range from
mild surprise to death. It depends on the amount of
current, voltage, and the duration of the electric shock.
Its hard to know exactly how a victim of electric
shock has been affected. More than likely, the victim
will be very pale or bluish in color and unconscious.
MEASURING VOLTAGE ON
As an ET, youll work on energized equipment.
You will be troubleshooting a piece of electrical or
electronic equipment, and the technical manual will
instruct you to measure voltages or to check signal
waveforms while the equipment is energized. But,
before you hook up the multimeter or oscilloscope,
there are certain safety precautions and procedures
you MUST follow. Theyre designed to protect you
from electric shock. These precautions and procedures
are divided into two basic categories: (1) voltage
measurements below 300 volts, and (2) voltage meas-
urements above 300 volts.
MEASURING VOLTAGE BELOW
Most of the voltage measurements that you will
make will be below 300 volts. Almost all of the newer
electronic systems use voltages that are less than 28
volts, except for the main input ac power. Here are
some safety procedures you should follow when you
need to measure voltages below 300 volts:
1. Notify and obtain permission from the
commanding officer (afloat) or your supervisor
(ashore) to work on energized equipment. Some
commands require you to complete a checklist before
2. Study the schematic and wiring diagrams of the
equipment on which youll be working. Note the
location of the points you will be measuring and, also,
the location of any other high-voltage points you should
be careful not to measure or touch.
3. Remove all metal watches, belt buckles, rings
(even wedding bands), and any other items that have
exposed metal. If youre wearing a security badge, put it
in your pocket.
4. Make sure youre wearing electrical safety
shoes, if they were issued, and that youre standing on
insulating rubber matting. If you must insert your hand
into the enclosure of the energized equipment, wear a
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