It is essential to know the velocity of the wind. This is determined by
means of an instrument called the anemometer.
Fig. 36. The Standard U. S. Weather Bureau Station Anemometer.
This is the well-known standard Robinson Anemometer, now in universal
use throughout the world for the registration of wind velocity, but of
the latest improved construction. It records electrically the miles or
kilometers, etc., of wind movements on a register. The standard pattern
as furnished to Weather Bureau stations is made of brass, highly
polished and finished, aluminum (or copper reinforced) cups, steel
spindle with hard steel bearings, a ten-mile or kilometer indicator,
electrical contacts, etc.
[Illustration:
Fig. 38
]
The four hollow hemispherical cups are mounted upon cross-arms at right
angles to each other, with the open sections vertical and facing the
same way around the circumference. The cross-arms are on a vertical
axis, which has at its lower end an endless screw. This axis is
supported so as to turn with as little friction as possible. The endless
screw is in gear with a wheel which moves two dials registering the
number of revolutions of the cups. The mechanisms are mounted in a
suitable metal case with glass front, as shown in the illustration, well
protected from the weather, the whole being designed for outdoor use.
[Illustration:
_Courtesy Julien Friez & Sons, Baltimore, Md._
Fig. 39
]
The center of the cups moves with a velocity about one-third that of the
wind which puts them in motion. The cups are four inches in diameter.
The distance from center of cup to center of rotation or axis is 6.72
inches. Assuming that the wind-travel is exactly three times that of the
center of the cup, the dials are marked to register miles of wind
travel, five hundred revolutions of the cups corresponding to a mile.
The ratio of wind-travel to travel of cup is in reality variable,
depending on the velocity of the wind. It is less for high than low
velocities. It varies also with the dimensions of the instrument, being
different for every different length of arm and diameter of cup.
On account of the great interference offered by buildings and other
obstructions to the free movement of the wind, its velocity is much less
in the vicinity of these obstructions than beyond; therefore, in
selecting the location for an anemometer, preference should be given to
the more elevated points in the vicinity of the station, and some rigid
support should be used to raise the instrument as far as practicable
above the immediate influence of the office building itself. The support
must be set up so that the anemometer on top or on the cross-arm is as
nearly vertical as possible.
The illustration shows clearly the appearance of an approved Weather
Bureau pattern combined support for wind instruments, similar to the one
installed at our plant.
[Illustration:
Fig. 40
]
[Illustration:
_Courtesy Taylor Instrument Companies Rochester, N. Y._
Fig. 41
]
Fig. 37. The Gilbert Anemometer.
The Gilbert Anemometer consists of a case containing a spindle passing
through a worm gear, which turns a toothed gear. This gear in its rotary
motion makes a contact with a brass brush, which is connected
electrically with a flashlight. The cross-arms, with cups attached, is
placed on the spindle, and as the wind blows, it revolves the cups,
causing the contact. The velocity of the wind is determined by counting
the flashes for fifteen seconds, thus giving you the number of miles per
hour. For instance, if light flashes eight times in fifteen seconds,
this signifies that the wind is blowing eight miles an hour.
Fig. 38. How to Connect the Gilbert Anemometer.
By referring to the diagram, you will see that one wire which should be
the annunciator wire, or even a small electric light wire, is connected
from the wire at the anemometer case directly to one side of the lamp
socket. Another piece of the same size wire connects the other side of
the lamp socket to one terminal of your switch. The second terminal of
the switch should be connected to an outer post of one dry battery. The
inner post of this same dry battery should be connected to the outer
post of the second dry battery. Complete the circuit by connecting the
inner post of the second dry battery to any one of the screws at the
bottom of the anemometer case. The lamp used should be a small
flashlight battery lamp for use on two and a half to three volts. Be
sure in making the connections that the ends of your wire are scraped
free from insulation and dirt. This can be done by cutting off the
insulation with a knife and then rubbing the copper wire bright by a
piece of sandpaper or emery cloth, or even a file. The switch should be
left open when you are not taking readings, in order to prolong the life
of your batteries. By unloosening the little screw in the hub of the
anemometer vanes, you can remove them and also take off the brass cap on
the anemometer case. This should be taken apart once or twice a month,
and some machine oil used around the bearings to keep them from wearing
out too quickly.
THE STANDARD ELECTRICAL SUNSHINE RECORDER AND THE GILBERT SUNSHINE
RECORDER
Fig. 39. The standard sunshine recorder is designed for recording the
duration of sunshine electrically, continuously, and automatically, on a
register. The instrument is essentially a differential air thermometer
in the form of a straight glass tube with cylindrical bulbs at each end,
enclosed in a protecting glass sheath, with suitable platinum wire
electrodes fused in at the center, the whole mounted in a metal socket
on an adjustable support.
[Illustration:
_Courtesy Taylor Instrument Companies, Rochester, N. Y._
Fig. 42
]
The base is secured to the support on the roof so that the glass tube
points north and south, with the blackened bulb toward the south and
lowermost, then the tube is inclined at such an angle that the
instrument will begin and cease to record sunshine with the proper
degree of cloudiness. This inclination should be approximately 45° from
the vertical. The machine should be adjusted at an hour when the sun is
wholly obscured.
In temperate and cold climates, slightly different adjustments will be
found necessary at different seasons of the year.
Fig. 40. The Gilbert Sunshine Recorder consists of a metal case,
cylindrical in form, with a piece of metal turned up on the ends,
dividing the cylinder in half. On each side of the case are small holes
through which the sun casts its rays and records its movement and
duration on a small piece of blue print paper inside the cylinder, one
piece of paper being in each compartment. When the blue print paper is
dipped in water, it becomes entirely bleached, with the exception of the
path made by the sun, which shows up in a blue line.
[Illustration:
_Courtesy Julien Friez & Sons, Baltimore, Md._
Fig. 43
]
[Illustration:
_Courtesy Julien Friez & Sons, Baltimore, Md._
Fig. 44
]
The sunshine recorder should be set up so that the ends point directly
north and south. The holes pierced in the sides of the case are nearer
one end than the other. The end that the holes are nearest should be
toward the south. It should be held firmly in place.