and run down to a navigation station to check
your position, that’s bad ergonomics—and
possibly bad seamanship.
Watertight Integrity
Is the equipment waterproof or water resistant?
The levels of watertight integrity of equip-
ment are often hidden in obscure specifications
that are typically incomprehensible without
reference to the standards. And there are several
standards that apply to water-resistant enclo-
sures for electronic equipment.
In the Code of Federal Regulations (CFR)
Title 46, Part 110, the U.S. Coast Guard
defines waterproof as: “Waterproof means
watertight; except that, moisture within or
leakage into the enclosure is allowed if it does
not interfere with the operation of the equip-
ment enclosed. In the case of a generator or
motor enclosure, waterproof means watertight;
except that, leakage around the shaft may
occur if the leakage is prevented from entering
the oil reservoir and the enclosure provides for
automatic drainage.” The original text of this
regulation included the following definition:
“Waterproof machine means a totally enclosed
machine so constructed that a stream of water
from a hose with a nozzle 1 inch in diameter
that delivers at least 65 gallons per minute can
be played on the machine from any direction
from a distance of about 10 feet for a period of
not less than 5 minutes without leakage.”
Another standard, which comes from a res-
olution made by the International Maritime
Organization (IMO), applies to handheld VHF
radios used in life rafts. The revised “recom-
mendation on performance standards for sur-
vival craft portable two-way VHF radio tele-
phone apparatus” describes several performance
issues related to waterproof integrity: “The
equipment should: be watertight to a depth of
1 m for at least 5 minutes, maintain water tight-
ness when subjected to a thermal shock of 45°C
electronic equipment installation guidelines 133under conditions of immersion, and not be
unduly affected by seawater, or oil, or both.”
Perhaps the most recognized and widely
used rating system is known as the IP (ingress
protection) rating, which is the work of the
International Electrotechnical Commission
(IEC). It includes a foreign-object rating as
well as a waterproof rating, which runs from 1
to 8, as shown in Table 13-1 on page 134.
An example of how this rating would look is
“IP X7.” Using Table 13-1, we can decode this
rating as follows: X indicates no rating for for-
eign objects, and 7 indicates protection against
the effects of immersion to 1 meter in depth for
up to 30 minutes. As another example, IP 67
indicates a piece of equipment is dust tight (6)
and protected against immersion (7).
One other rating system you are likely to
encounter is the Japanese Industrial Standard
(JIS). This standard is nearly identical to the IP
standard. Like the IP system, the waterproof
grade may range from 1 to 8. The higher the
number, the better the protection; for example,
a product that is waterproof rated to JIS 6 has
been subjected to a test that includes exposure to
powerful water jets from all directions with no
ill effects. A JIS 7 rated product has been tested
to withstand being dropped in the water (up to
1 meter deep) and retrieved fairly quickly. This
is a useful rating for handheld VHF radios.
Check the product specification sheet for
any or all of these ratings. They can help you
determine the appropriate location for a piece
of equipment—in an open cockpit versus
inside a cabin or other enclosed space on a
boat. It’s valuable information that can dra-
matically affect the usable life of the electrical
or electronic gear used on boats.Thermal Limits
In Chapter 5, we discussed the use of an
infrared heat-sensing gun to check ambient
and equipment temperatures for problems or