IMPROVEMENTS IN HYGROMETERS AND IN METEOROLOGICAL INSTRUMENTS CONNECTED THEREWITH
Year: 1882

page_text: LETTERS PATENT to Friedrich Hermann Felix Engel Civil Engineer and
Patent Agent in the city of Hamburg Germany for an Invention of
"IMPROVEMENTS IN HYGROMETERS AND IN METEOROLOGICAL INSTRUMENTS
CONNECTED THEREWITH A communication to me by Wilhelm Klinkerfues,
"
Doctor of Philosophy, Professor and Director of the Royal Observatory at
Göttingen in the German Empire.
PROVISIONAL SPECIFICATION left by the said Friedrich Hermann Felix
Engel at the Office of the Commissioners of Patents on the 23rd December
1882.
FRIEDRICH HERMANN FELIX ENGEL Civil Engineer and Patent Agent in the
city of Hamburg Germany "IMPROVEMENTS IN "HYGROMETERS AND IN
METEOROLOGICAL INSTRUMENTS CONNECTED THEREWITH" a communication to me by
Wilhelm Klinkerfues, Doctor of Philosophy, Professor and Director of the Royal
Observatory at Gottingen in the German Empire,
This invention relates to hair hygrometers and is also applicable to instruments
in which the hygroscopic qualities of the human hair are employed for indicating
the relative moisture of the atmospheric air in combination with air pressure and
temperature of air.
As a hair or a hair string of quality and preparation as used for hygrometera or
weather-instruments generally changes its length not in geometrical proportion to
the changes of relative moisture of the air and as p. i. a hair string of 100 units
of length is at an increase of relative moisture from 0 per cent to 10 per cent
lengthened by 0.517 of a unit, whilst the length at a rising of relative moisture
from 90 per cent to 100 per cent only increases by 0.117 unit a practical difficulty
arises in construction and adjustment of such hygrometers and other meteorological
instruments connected therewith from the cause that the corresponding scales
cannot be divided into equal parts or divisions without the aid of more or less
complicated mechanism arrangements of adjustment.
By the present invention this difficulty can be overcome with an exactness that
fully suffices for most practically purposes.

page_text: Suppose a hair or hair string be at one end fastened to an arm fastened to an
axle which is influenced by a volute spring in such manner that the hair string is
continually kept in tension and the arm will at an increase of relative moisture of
the air and corresponding lengthening of the hair-string turn to the left together
with its axle. If to this arm a non hygroscopic string be attached with its one
end, whilst its other end is again fastened to a fixed part of the instrument and if
this string is of such length that it will have a slack during all changes in length
of the hair-string, this slack will be of different width according to the changes in
length of the hair-string. With an increase of the length of hair-string, that is
during an increase of percentage of relative moisture, this slack will be reduced
whilst it will increase with a decrease of relative moisture of the air. By con-
necting the slack by means of an eye and another non hygroscopic string to &
roller or lever of the centre axle which latter by another string and roller and a
small spring keeps the slack string tensioned, the indicating hand of the centre
shaft will according to the changes of relative moisture either turn to right or left
and indicate either rise or fall of percentage of relative moisture of the air.
As the bend of the slack of the non hygroscopic string during equal changes in
length of hair string or distance between the points at which the non hygroscopic
string is fastened, does not increase or decrease in geometrical proportion with the
hair string or the aforesaid distance but as in the contrary case the slack grows in
decreasing proportion with equal reductions in length of hair string whilst it grows
in increasing proportion with equal increases in length of hair string this
geometrical attribute of the slack in combination with the aforesaid attribute of a
hair string according to which the dimensions in length grow in decreasing
geometrical proportions with the percentage of relative moisture of the air allows
the use or application of a scale with equal divisions for all percentage of relative
moisture.
If the bracket to which the hair string and non hygroscopic string are attached
instead of being a fixture to the ground-plate of the instrument, is connected to
the free end of a thermometrical ring after Bourdon's system, or to the free end of
an aneroid ring after Bourdon's system, or to the diaphragm of an aneroid box
after Vidi's system, this bracket will according to the changes of temperature, or
to the barometric alterations of air-pressure come nearer to, or be moved further
apart from the axle of the first spring arm and will consequently influence the
movements of the centre axle and indicating hand in combination with the
hygroscopic alterations of the hair-string.
In such combination the invention can usefully be applied to instruments
indicating the dew-point of the air or to instruments for fortelling the coming
weather.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Friedrich Hermann Felix Engel in the Great Seal Patent Office
on the 22nd June 1883.
"
FRIEDRICH HERMANN FELIX ENGEL Civil Engineer and Patent Agent in the
city of Hamburg Germany IMPROVEMENTS IN HYGROMETERS AND IN METEORO-.
LOGICAL INSTRUMENTS CONNECTED THEREWITH "
a communication to him from
abroad by Wilhelm Klinkerfues Doctor of Philosophy Professor and Director of the
Royal Observatory at Göttingen in the German Empire
This invention relates to hair-hygrometers and is also applicable to other
instruments in which the hygroscopic qualities of the human hair are employed for
indicating the relative moisture of the atmospheric air in combination with air
pressure and temperature of air.
As a hair or a hair-string of quality and preparation as used for hygrometers or
weather-instruments generally, changes its length not in geometrical proportion to
the changes of relative moisture of the air, and as for instance a hair-string of
100 units of length is by an increase of relative moisture from 0, per cent to
10 per cent lengthened 0.517 units while by an increase of relative moisture from
90 per cent to 100 per cent the length is increased only 0.117 units, a practical
difficulty arises in construction and adjustment of such hygrometers and other
meteorological instruments connected therewith for the reason that they cannot
have their corresponding scales divided into equal parts or divisions without the
use of more or less complicated mechanical arrangements of adjustment.
By the present invention this difficulty can be overcome with an exactness that
fully suffices for most practical purposes.
Fig 1 is a front view of an apparatus with the dial portion and cover removed
illustrating the invention.. Fig is an axial section of the same and Fig 3 is a
diagram illustrative of the action of a non-hygroscopic string on the hygroscopinc
hair-string.
Suppose a hair or hair string h Figs 1 and 2 be at its one end secured at a fixed
point & and at its other end secured to an arm b fastened to the axle e which is
influenced by a spring m in such a manner that the hair string his continually
kept extended at tension (in a straight line) this arm b will by an increase of
relative moisture of the air and corresponding lengthening of the hair string / be
caused to turn to the left together with the axle e. If to this arm b a non-
hygroscopic string / be attached with its one end, while its other end is fastened to
a fixed part or standard d of the instrument and if this string is of such length
that it will remain bent (have a slack) during all changes in length of the hair-
string this slack designated by in the drawing will be of different width
according to the changes in length of the hair-string h. With an increase of the
length of the hair string / that is during an increase of percentage of relative
moisture this slack will be reduced, while it will be increased with a decrease of
relative moisture of the air. By connecting the slack of the string 7 by means of
an eye o and another non-hygroscopic string i to a roller or lever of the index
pointer axis which latter by another string and roller and a spring p keeps
the slack of the string taut, the indicating hand of the index pointer axis z will
according to the changes of relative moisture either turn to the right or left and
indicate either a rise or fall of percentage of relative moisture of the air.
As the bend of the slack of string 7 during equal changes in length of string h,
or distance between the points at which is fastened, does not grow or decrease in
geometrical proportion with the hair string h or the aforesaid distance, but as on

page_text: the contrary increases in decreasing proportion with equal reductions in length of
the hair-string has will be understood with reference to Fig 3 of the drawings (in
which Figure, ¹ h², h³ and so forth designate the alterations in length of hair
string h and x, x², x³, and so forth the corresponding changes of the bend of slack x
of string ) while it grows in increasing proportion with equal increases in length
of h this geometrical attribute of the slack x in combination with the aforesaid
attribute of a hair-string according to which the dimensions in length increase in
decreasing geometrical proportions with the percentage of relative moisture of the
air allows the use or application of a scale with equal divisions for all percentages
of relative moisture.
If the bracket d to which the hair string h and string are attached instead of
being a fixture to the ground plate of the instrument be connected to the free end
of a thermometrical ring after Bourdon's system, or to the free end of an aneroid
ring after Bourdon's system or to the diaphragm of an aneroid box after Vidi's
system, this bracket d will according to the changes of temperature, or to the
barometric alterations of air-pressure come nearer to, or be moved further apart
from the axle e and will consequently influence the movements of axle z and the
indicating hand in combination with the hygroscopic alterations of hair-string h
In such combination the invention can usefully be applied to instruments
indicating the dew point of the air or to instruments for fortelling the coming
weather.
Having now described the nature and particulars of the said invention in such
wise that the same may be readily carried into practical effect, I claim :-
The combination of a straight hygroscopic hair-string h and a non-hygroscopic
bent slack string 1 connected by means of a string i to the axis z of the index
pointer in such manner that the shortening of the hair string h deepens the bent
slack of the string whilst the lengthening of the hair-string / reduces this bent of
the slack all as herein described as and for the purpose set forth.
In Witness whereof I the said Friedrich Hermann Felix Engel have hereunto
set my hand and seal this sixteenth day of June in the year of our Lord
One thousand eight hundred and eighty three.
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