October 1957 Radio & TV News
Wax nostalgic about and learn from the history of early
electronics. See articles from
Radio & Television News, published 1919-1959. All copyrights hereby
If you enjoy reading about instruments with names like the
Eppley pyrheliometer and the
conductivity bridge salinometer, then this article is for you.
Long before there were Earth-imaging and environment-monitoring
sonobouys, and autonomous robotic dolphins perpetually roaming
the world's oceans, it was up to ships and crews to do the often
perilous work. Even with the aforementioned remote sensing technology,
it is still necessary for the detailed work to be carried out by
humans at the study sites. Raging, swelling, stormy seas imperil
the lives and well-being of everything aboard, but don't pity the
scientists - they are there because they love what they are doing
and thrive on the challenge. It is a seafaring tradition and trait
that reaches back to the dawn of time. Landlubbers like myself appreciate
the sacrifices of sailors from ancient days of yore as well as today's
intrepid explorers. That said, I could do without the types who
do 'research' based on what the politically correct desired outcome
is to prove some scientifically unsound theory ... and it usually
involves receiving large sums of money for supporting 'the cause.'
Electronics on the Hurricane Ship
By Nicholas Rosa
Woods Hole Oceanographic Institution
Special electronic devices provide measurements of the elements
on the world's only hurricane vessel, a pioneer in the important
science of oceanography.
The R/V "Crawford," 125·feet long and powered by husky
twin diesels, carries fifteen officers and crewmen and seven
scientists. Formerly a Coast Guard cutter, she is now the
property of Woods Hole Oceanographic Institution. Living
quarters are forward in hull while the laboratory is at
the aft end of the deckhouse.
Everyone has at least a nodding acquaintance with the usual items
of shipboard electronic gear. Two-way radio in one form or another
has been used since the early part of the century and radio direction
finders were an early development. Since World War II loran and
radar have come into wide use and before that the sonic depth finder,
or echo sounder, had appeared.
The world's only hurricane ship, the research vessel "Crawford"
of the Woods Hole Oceanographic Institution on Cape Cod, has all
of these things, but they are just for getting the ship from one
place to another. For her work with the elements, the "Crawford"
carries some new developments and others which, if not quite new,
are at least exotic.
The "Crawford" is not one of the well-known Coast Guard-Weather
Bureau weather patrol ships. She is part of WHOI's private fleet,
which includes the famous ketch "Atlantis." Like the "Atlantis,"
she is essentially an ocean-research vessel. A group of scientists
at Woods Hole has developed a theory on the origin of hurricanes
in which the moods of the tropical ocean play a major role. None
of the other Woods Hole ships was quite suited to the work of investigating
this theory, and all were tied to other research programs that have
years to run.
Early in 1956, the "Crawford," a surplus Coast Guard cutter in
mothballs, was acquired from the U.S. Department of Health, Education,
and Welfare. Several months were spent in refitting and alterations,
including the addition of a laboratory deckhouse and changes in
living arrangements. Air conditioning was installed for cruising
in the tropics, something of a novelty on research ships. (Until
the "Crawford" came along, it was traditional for oceanographers
to steam like so many clams.) Three electric winches, including
a heavy trawl winch, were added to the usual deck gear. To power
all this, plus an evaporator to make fresh water from the salty,
and all the electronic research tools, extra generating capacity
was added in the engine room.
In the summer of 1956, the ship was delivered to the WHOI fleet,
and after a couple of weeks spent installing research equipment
she set out for the tradewind belt of the North Atlantic, the most
common breeding-place of hurricanes. Her assignment was not to look
for storms but to study the structure of both the atmosphere and
the ocean of the tradewind belt. If she happened to be where a hurricane
was starting and could get detailed data on the early stages (which
has never been done), this would be considered "good luck." The
job of "hurricane hunting" is for the B-50's, once the hurricane
is big enough to be noticed.
I joined her in San Juan, Puerto Rico, in time to meet Hurricane
Betsy, which caught us in San Juan harbor after we had been out
for a few days' routine research. The ship was in danger of being
pounded against the concrete dock, so we cast off and put out into
the wind. The ship handled very well, but we just treaded water
until Betsy got by. We had orders not to look for trouble; that
was for the hurricane-hunting planes. Betsy was now full-grown;
we had missed her birth.
The author studying the record of the precision echo
sounder. which is far more elaborate than conventional sounders
and is only partly pictured here. Double row of toggle switches
offers wide choice of "ping" lengths and spacings. The parallel
lines on paper are fathom-interval marks. Knob near author's
wrist controls width of fathom range. Panel marked "Prec."
at top has precision a.c. frequency and voltage meters.
Outgoing and returning "ping" can be heard through a pair
Scientist puts finishing touches on some of the lab equipment
before a cruise. Objects in rack at right are Nansen bottles
with deep-sea thermometer frames, used for capturing water
samples at different depths. From Nansen bottles samples
are transferred to glass or plastic storage bottles which
are shown at lower right.
I had been assigned to the "Crawford" to help out with radiosonde
observations and also to operate one of the newer "black boxes"
in the lab. This was the conductivity bridge salinometer, for measuring
the salinity of sea water samples.
Salinity can be defined as the total amount, in grams, of dissolved
solids in a kilogram of sea water. In all the open oceans and larger
seas, where land influences do not interfere, all the solids, or
"salts," are in a fixed ratio to each other. Sea water is sea water,
whether "thin" like the Baltic Sea or "thick" like the central North
Atlantic. The composition is everywhere the same, but the concentration
varies. The major salts are ionized; that is, they are broken up
into constituent atoms or groups of atoms, each bearing an electric
charge. Sea water is an electrolyte.
For that reason, salt water can conduct electricity. Like any
conductor, it has the properties of conductivity and resistance,
which are functions of each other. It so happens that the conductivity
or resistance of a sample of sea water changes predictably with
changes in its salinity, "other things being equal."
The most important of the "other things" is temperature. In the
salinometer, the sample testing cells sit in an oil bath which is
kept at a constant temperature by means of a heating element that
is controlled by a thermistor bridge.
In this work, the resistance of the sample has to be measured
to the hundredth of an ohm, and a good bridge circuit is called
for. An ordinary d.c. Wheatstone bridge would present some problems.
Electrolysis effects from the d.c. would damage the sample, with
the water breaking up into hydrogen and oxygen, certain ions depositing
on the testing cell electrodes, etc.
The Woods Hole bridge, like earlier Coast Guard models, uses
a 1000-cycle a.c. signal which keeps these effects to a tiny minimum,
which can be ignored.
The sample is connected in the "unknown" arm of the classical
bridge circuit. A semi-permanent sample of sea water is carried
in an adjacent arm to give both sides of the bridge the same temperature
response. The other two arms consist of manual decade resistances.
One is the reading arm, which carries a precision potentiometer
across part of its circuit for "fine" balancing. The other arm is
also variable to compensate for minor variations in the individual
Rough balancing is done manually, and then electronics takes
over. As long as the bridge is unbalanced, a 1000- cycle signal
will appear at its output. The signal is fed to a phase detector
(like the one in a modern FM receiver) and compared there to a 1000-cycle
reference signal. The output of the phase detector is a d.c. voltage,
the polarity of which depends on the direction of unbalance of the
The d.c. output is fed to a chopper type servo amplifier which
controls a small servomotor. This turns the precision potentiometer
in the "reading" arm. When the bridge comes into balance, the d.c.
voltage disappears, the servo amplifier output cuts off, and the
motor stops. A visual indicator geared to the motor-potentiometer
shaft reads the final hundredth of an ohm.
The salinometer is checked at intervals against a "standard"
sea water carried in sealed glass ampules, and also against standard
500-ohm resistors, which can be substituted for the permanent and
"unknown" sea water samples.
Salinity affects the density of sea water, and its boiling and
freezing points. It has an effect on the vapor pressure of the water
surface, and therefore a slight effect on the rate at which sea
water evaporates into the atmosphere, although this last effect
is usually masked by other forces.
Salinity is also part of the environment of all sea life, and
partly determines what kind of animals can live where in the sea.
This is of vast interest to biologists, fisheries experts, and others,
including all consumers of sea food, from pelican to epicure.
By plotting the temperature-salinity curves of water samples,
oceanographers can trace water from the Mediterranean all the way
over to the western Atlantic, and find Antarctic water flowing under
the North Atlantic. Currents like the Gulf Stream can be traced
by salinity as well as temperature contrasts with surrounding waters.
Currents carry heat from place to place, it being an old story that
the Gulf Stream moderates the climate of Europe. They also carry
oxygen, nutrients, and vast streams of plant and animal life in
the drifting plankton, which is the first link in the food chain
running from microscopic algae through shrimp and fish to whales,
birds, and men.
I have mentioned temperatures as the other identifying mark of
a water mass (such as Mediterranean) or a current. It also happens
to be a villain in the hurricane story, because water temperatures
down to a considerable depth affect the amount of energy (in the
form of heat) available for the making of hurricanes.
Liquid-in-glass thermometers of various types have served very
well in oceanography as everywhere else, but they are fragile and
fussy. They cannot be used to give a continuous, automatic record,
which is often needed, especially when the temperature profile from
the surface to a depth is desired.
For many years oceanographers have used a mechanical bathythermograph,
or BT, which is a small, torpedo-shaped brass "fish." This is lowered
into the depths at the end of a cable, and it traces a record of
temperature vs depth on a small smoked-glass slide in its innards.
The BT is the sine qua non of ocean research. It is almost hard
to imagine an oceanographic ship moving from one dock to another
without starting a BT schedule as a regular procedure.
Unfortunately, the BT, while rugged-looking and heavy, is vulnerable
to thermal as well as to severe physical shock, and is only good
to 900 feet. It doesn't take much imagination to know all kinds
of things can happen to smoked glass slides as well, including being
smudged by the operator's thumb or dropped to the deck and smashed.
If a cable breaks or a fitting comes loose in spite of the operator's
loving care, more than just a record is lost in the deep. The brass
"fish" itself is quite expensive.
A group of engineers and technicians at Woods Hole have come
up with a thermistor BT. Variations in the thermistor's resistance
with varying water temperature will cause corresponding variations
in a current sent through it from the ship. This eliminates the
delicate glass slides, as the variations can be recorded on a moving-paper
chart. This also delivers a record many times the postage-stamp
size of the slide. The record is instantly available and a choice
of multiplier resistors and chart speeds control the sensitivity.
The thermistor must be electrically insulated and protected from
the salt water and its pressure, of course.
Troubleshooting is fairly easy; the equipment is amenable to
all the standard servicing instruments. Comparison resistors switched
into the thermistor line give spot-checks on calibration. (Checking
the calibration of a mechanical BT is a long and tedious process.)
Taking the surface temperature at intervals with a good liquid-in-glass
thermometer and knowing that the machine is properly calibrated
are all the oceanographer needs for confidence.
It is still necessary to know the depth at which the temperature
is being taken. The length of "wire out" will not give the answer
because of the movement of the ship. There is always a "wire angle"
and this is not constant under water. A combination of a Bourdon
tube, sensitive to pressure, and a variable precision resistor is
the answer to this.
The thermistor comes into play again for the continuous recording
of surface temperatures as the ship cruises. The usual engine-room
thermograph (at the cooling system intake) is not very reliable.
A thermistor thermograph can be kept "on the nose" very easily.
The "Crawford" carries two thermistors in protective housings below
the water line on her bow. Either of these may be switched into
a recorder in the lab.
For many purposes, the plotting of ocean currents on charts by
means of temperature and salinity data is too slow and cumbersome.
Sometimes an ocean current will shift, or throw off short-lived
"coils" or "eddies."
There is another, more direct way of tracing currents in the
open ocean, while the ship is cruising in the current. This is the
Geomagnetic Electrokimetoqraph, or (understandably) GEK.
"Everyone" knows that a conductor moving through a magnetic field
will have an electric current induced in it by that field. Sea water
is a conductor, and an ocean current is a conductor in motion. The
earth itself supplies the magnetic field. The principle of the GEK
is as simple as that.
The ship trails two electrodes astern, about a hundred meters
apart on the same two-conductor cable. They trail far enough back
to get away from the magnetic influences of the ship itself. Since
the two electrodes are "tapped" along the semi-resistive conductor
of sea water, there is a potential difference between them. The
GEK turns out to be nothing more or less than a recording voltmeter.
The front panel of the conductivity bridge salinometer.
Moving chart at right records final .01 ohm of reading:
hundreds, tens, and units are read from three manual decades
at top right. Other five decade switches are for compensating
for differences in the five sample cells set in plastic
discs (bottom). The magic eye tube shown at the top right
of the panel is also used to indicate bridge balance.
A technician records date and time on the automatic record
chart of the Eppley pyrheliometer. used for measuring the
intensity and duration of sunlight. This record is similar
in appearance to that made on other units used in the laboratory.
After running four minutes on a base course, the ship turns 90
degrees and runs four minutes more. Then it backtracks over both
of these legs. This reverses the polarity of the voltages being
recorded and allows a "zero point" or average to be taken. Since
the current is moving the ship, the "set" of the ship will show
up as a displacement of the trace to one side or the other of the
zero line. The two four-minute legs are sides of an electrical right
triangle, and the third side can be found by applying the Pythagorean
Theorem. This will give the strength of the current after corrections
for the vertical intensity of the earth's field, etc. The displacement
of the recorded legs with the set of the ship indicates direction.
For years sonic sounders have been used in navigation, and a
conventional model is used on the "Crawford's" bridge. A very fine
version, called simply the precision echo sounder or PES, is part
of the laboratory.
The PES employs an Alden recorder, in which a strip of chemically
treated paper runs between a fixed electrode and a single turn,
rotating helix electrode. A current between these electrodes makes
a tiny colored mark on the paper. Each time an echo returns from
the bottom (or from the scattering layer) such a current flows.
Just where the mark appears on the paper depends on where the helix
is in contact with the fixed electrode bar which depends, in turn,
on the elapsed time since the outgoing "ping" was sent. Paper speed
and helix rotation are synchronized so that the fine marks are very
close together, making a fairly thick but clean (and clearly readable)
A precision a.c. supply is incorporated in the unit to insure
proper synchronization. This is a husky amplifier using push-pull
807's in the output. The input signal is supplied by an electrically
driven, 60-cycle tuning fork in association with a tube. The input
circuit is reminiscent of a crystal r.f. oscillator, except that
the tuning fork with its magnetic pickup replaces the crystal in
its capacitor holder.
The PES gives a breathtakingly clear picture of bottom contours,
and the operator may select from several ranges at will to bring
out fine detail. The paper speed, helix rotation, and timing of
the "ping" automatically synchronize for the different ranges. A
time marker appears on the paper at frequent intervals. This helps
to plot the geographical positions of bottom features to close accuracy,
by consulting the navigator's log of "fixes." The paper comes off
the instrument in a continuous sheet for constant availability.
On it, the machine has electrically marked fathom-interval lines
for ease in reading.
On other ships, enormous submarine canyons have been discovered
by continuous echo sounding. These are often named after the discovering
ship. At this writing, the "Crawford" hasn't found hers, but it
is fascinating to watch the mountain ranges "come into view" far
beneath the ship. With the PES, cruising becomes something like
The oceans and the atmosphere have long been regarded as heat
engines, and modern oceanographers tend to see air and sea as one
heat engine. The fuel, of course, is the sun, and scientists would
naturally want to measure the "fuel intake."
For this purpose the "Crawford" carries a recording
Eppley pyrheliometer, supplied by the U. S. Weather Bureau.
This consists of a sensing element, an amplifier, and a recording
output meter. The sensing element is a thermopile mounted between
two small discs, a white reflecting disc and a black absorbing disc.
This assembly is enclosed in a glass bulb about the size and shape
of a 100-watt household lamp bulb. Sunlight produces a temperature
difference between the white and black discs. The temperature difference
acts on the thermopile to produce a voltage which can be measured
and recorded by the rest of the system. The sensing bulb sits high
in the rigging and the recorder down in the lab.
Radiosonde was mentioned near the beginning of this article,
and now it rounds out the description of the ship's instruments.
Most readers are probably familiar with the radiosonde concept,
but perhaps a brief review would be helpful.
After a cruise come weeks or months of "working up" data. Colin
Macafee, expedition leader of 1956 cruises. goes over scientific
logs of ocean "stations," where ship stopped to collect hydrographic
and meteorological data. with assistant.
A balloon is sent aloft carrying weather instruments and a radio
transmitter. The instruments are an aneroid barometer, a thermistor
temperature element, and a chemical-on-glass humidity strip. The
resistances of the latter two change with temperature and relative
As the balloon rises, the barometer element reacts to the falling
air pressure around it. Instead of moving a pointer on a dial face,
it moves a contact arm over a printed-circuit switch. With the help
of a small relay this switch cuts the instruments in and out of
the modulator circuit of the transmitter.
On every fifth contact, a fixed resistor is in the circuit to
signal a pressure reference. On all other contacts the humidity
element is in the circuit. Between contacts, the thermistor is in
the circuit. The resistance of each of these elements, in turn,
controls the pitch of an audio oscillator, which modulates the 403-mc.
signal of the tiny transmitter.
The receiver on the ground consists of a superhet, an audio frequency
meter and still another moving paper recorder. Several manufacturers
make the various units of the system. The operator interprets the
frequency record to prepare a chart showing pressure, temperature,
and relative humidity vs height. The results are coded and sent
to the Weather Bureau by radio.
Radiosondes were used twice a day during the hurricane-season
cruises (summer and fall) of the "Crawford" and surface weather
observations were radioed to the Bureau every three hours. The ship
thus acted as an "operational" weather station for forecasting purposes,
as well as an observatory for the hurricane research program.
At times the "Crawford" has worked closely with the WHOI flying
laboratory, a PBY-6. One of the Woods Hole devices aboard the PBY
is a radiometer for measuring sea-surface temperatures from altitudes
of a thousand feet or so. The "Crawford's" role was to take surface
temperatures by conventional means for calibrating the radiometer,
plus surface weather observations to supplement the plane's studies
of the structure of the tradewind belt.
Recently the radiometer has been able to help unravel some of
the intricacies of the Gulf Stream's structure. It is now being
used in the hurricane studies, along with other special electronic
equipment designed for airborne oceanography.
The story of electronics in oceanography does not end here. Many
other devices, some just now a-borning, were not carried on the
"Crawford" or the PBY for the hurricane work. There are transponder
drift buoys, for instance, that answer a radio call from their mother
ship or plane so that she can track them. There are also robot hydrographic
observers that can be anchored in out-of-the-way spots, even submerged.
A sonic call from the mother ship will bring them to the surface,
and they then signal their whereabouts by radio.
In many of these research aids the circuitry is new. Some ideas
await the development or genius-stroke of a usable circuit. In such
things as the drift buoys, where power supply is limited and weight
and size are critical factors the use of transistors will be important
Transistor circuitry will also be useful in sensing elements lowered
from a ship. An example is a new salinity-temperature-depth instrument
under development for use at the end of a cable. Many of the salinometer
functions described earlier will be carried on far under water,
by servomotor and other control from the ship. Much of the salinometer
circuitry will have to be "packed in the can" along with much of
the power supply. Here the transistor with its small power requirement
will come into its own.
The study of hurricane , big as these storms are in man's way
of looking at things, is the study of mere "backfires" in the ocean-air
heat engine in the tradewind belt. As every reader knows, a gigantic,
coordinated international effort at examining the entire "machinery"
of the earth is being made during the International Geophysical
Year, 1957-58. The "Crawford" and the other Woods Hole ships are
participating in this exciting venture.
At the end of January, 1957, the "Crawford" left Woods Hole once
more for the tropical Atlantic on a four-month preliminary cruise
(the IGY actually runs from July 1, 1957 to December 31, 1958).
On this cruise we brought along special sampling equipment for studies
of the age of the deep Atlantic waters by the Carbon-14 method,
along with the equipment described so far. The hurricane work is
not being abandoned in the IGY. All the IGY findings on oceanic
and atmospheric energy will probably have a bearing on it.
Oceanography is rather new to the public, although it has been
recognized as a scientific province for more than a century. Until
recent years there was rather little publicity on all that oceanographers
have been doing. The field has been growing in scope, size, and
importance, especially as land resources dwindle and the world's
population increases. The oceans are an untapped source of food,
minerals, and energy. Oceanography will soon be recognized as a
"new frontier." Its instrumentation will be a new frontier in electronics.
We have hardly more than punctured the surface of this virtually
Posted January 2, 2015