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Патент USA US2412541

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Dec. 109 1946u
Pf F. sHxvERs
2,412,54î
ALTIMETER
Filed Nov. 20, 1942
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5 Sheets-Sheet l
Dec. 10, 1946.
P_ F,_5_H|VERS
2,412,541
ALTIMETER
Filed Nov. 20, 1942
5 Sheets-Sheet 2
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Dec. l0, 1946.
P. F. sHlvERs
ALTIMETER
Filed Nov. 20, 1942
5 Sheets-Sheet 3
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Dec. 10, 1946.
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2,412,541
ALTIMETER
Filled Nov. 2o, 1942
5 Sheets-Sheet 4
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Dec. 10, 1946.
P. F. sHlvERs
2,412,541
ALTIMETER
Filed Nov. 2o,l 1942
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Patented Dee. 1o, e1am»
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2,412,541
UNITEDy y STATES PATENT OFFICE
2,412,541
-AL'rlME'rER
Paul F. Shivers, Edina, Minn., asslgnor to Minne
apolis-Honeywell Regulator Company, Minne
apolis, Minn., a corporation of Delaware
Application November 20, 1942, Serial No. 466,283
15 Claims. (Cl. 73-387)
- My present invention relates to measuring
instruments of the type which indicate changesy
in the magnitude of a variable condition by their
response to related changes in the pressure _of a
means operatively connecting a pressure re
.sponsive member and an indicating member, ln
an. instrument such as I have described, the con~
nection being adjustable to compensate for difier
gas mass. More specifically, my invention relates 5 ences, in density and temperature, between the'
to the ñeld of altimeters which indicate variations
standard atmosphere and the actual atmosphere
in'altitude above a reference point by responding
between the instrument and the reference peint.
to the corresponding variations in the static air
Another object of my invention is to provide
pressure (that is, the barometric pressure).
novel means, in an instrument such as l'. have
The static pressure indicated by such an in- 10 described, for increasing or decreasing the altitude
strument is influenced by the altitude of the instrument and by the density of the air mass and
its temperature gradient. For the saire of unì-
formity in instrument dial calibration, certain
indicated by the instrument in accordance with
increase or decrease of the density of the animeea
phere between the instrument and the reference
point
arbltrary values of density and temperature have l5
A further Object or" my invention is te ¿Urol/ld@
been selected to define a "standard atmosphere."
novel means, in
instrument Such as' ï have
rl‘his standard atmosphere is of suoli density as to
described, for adjusting the instrument t@ ©0121“
give a barometric pressure at
point one tout
pensate L50? dîffeïâïlßës bâïJWEeü the 2li-@2m ÈGII m
cury
above sea
29.92
levelinches
equal tohigh.
that oi?‘The
a column
temperature
of mergradient in the standard atmosphere is -sucli that
at sea level the temperature is
F., while te@
perature
mean temperature
of the standard
of the atmosphere
atmosphere between
the instrument im@ the T’êîeï‘enß@ Swim
Yet another obiect of my invention is to are»
vide novelineanain aninstrurnent suoli as b
describen ÍOT âäïálls'tîâ’ls the íïll‘ìißä?i‘ôïlî Gl
instrument in accordance with variation in
temperature at the reference point.
temperature is _67° at the bottom si an 35;;
thermal layer which has been found ‘to exist at
a variable height of> approximately 35,@@0
m
middle latitudes. .ln this standard atmosphere
the barometrie pressure has ‘been :found to have
an inverse logarithmic
relation te the altitude,
'
and pressure responsive means have been designed.
to give indications'on a linear scale
resp@
to logarithme elianges in pressure, ”'
e altitude
A still further object of my `
provide novel
in en instî’urne "
have described, for adjusting the
' i
instrument
simultaneeusl
on this scale corresponding to
se given static
pressure is called the “pressure altitude”
the
point at which the pressure indication is ense-riferi,
and is the altitude indicated by
altimeter.
The atmosphere enveloping
not normally thi s
but differs
uncompensated
craft :lT
i’
tuile therefor
the actual ai nie
ence point.
aríatiens
... llave
indicated altitude
@een
due to extreme barometrì C
may be caused. by Variations of t,M
from the standard.
is an object of my invention to gravide, ‘in
»Ji Èîï@ îï‘lßïï‘üïïleîîî
a pressure responsive instrument for measuring 5S referente
altitudenovelmeans loradiusting tneinstrument
met
et. my invention is to nio
to compensate for tite differences between the
separately onerabi eentrel means for elec
standard atmosphere and the actual atmosphere
pressure
adjusting an'aitimeter
tite referente
forpeint
air ternperatru‘e
and for responu
between the instrument and a reíerence point..
It is another object of my invention to provide
.
.I
-
|
-
)J
sltely
I?
~
r.
:e
„
A»
-`~-
a.
ticle rea-¿lne of the altimeter
2,412,541
4
Other objects and advantages of this inven
in» accordance with the temperature and static
pressure of the ambient atmosphere.
tion are set forth in the following description,
It is also‘an object of my invention to pro- `
vide electrical means for the transmission of
the novel features thereof are pointed out in the
taken with the accompanying drawings, and
appended' claims. The disclosure, however, -is
atmospheric pressure changes to indicating CII illustrative
only and I may make changes in
means whereby to eliminate insofar as possible
detail, especially in matters of shape, size and
meremechanical means for the amplification of
arrangement of parts within the principle of the
the movement of the pressure responsive means.
Another object of my invention is to provide
a balanced electrical bridge circuit and means
for unbalancing the circuit operated by the pres
invention, to the full extent indicated by the
broad and Vgeneral meanings of the terms in
which the appended claims are expressed.
sure responsive member or aneroid of an altim
eter, whereby, upon a change in .the position
partsin the various ñgures,
of the aneroid, the indicator means of the al- timeter may be actuated and the aneroid re 15
20
vide control means for adjusting or varying the
return or zero point of a. counterbiased aneroid
for aI given ambient pressure, such control means
Figure l,
~`
Figure 3 is an enlarged end view of the atmos- Y
pheric pressure responsive control member of
'Y Figure 1.
being regulated `by a temperature . responsive
Figure 4 represents a _modiñed form of manu
ally _operable .temperature compensating con
trol
-
'
A
perature compensating control means shown in
arise.
‘
Y
of my invention,
Figure 2 is an enlarged end view of the tem- y
ing parts through which mechanical error might
means.
K
Figure 1 represents diagrammatically one form
turned to the original or zero position so as to
eliminate insofar as possible mechanical or mov
- Further; it is an object of my invention to pro
i
In the accompanying drawings wherein like
reference characters indicate corresponding
'
Another object of my invention is to provide
a pressure responsive altimeter and electrically
. operated means for the automatic correction of
means.
`
»
'
'
'
'
Figure 5 is a front elevational view of the ccn
Vtrol panel of 'my invention shown in Figure 1
with the manually operable temperature compen
sating control means of Figure 4.
^
the indication of the instrument for the -in
iluence of changes in atmospheric temperature. 30 Figure 6 is a pictographical representation il
lustrating the variation in indicated pressure al
It is also an object of my invention to provide >
_ in an altimeter a. plurality ofv photoelectric cells
and a plurality of separate means for_varying_
the relative electronic emissions therefrom so as
to regulate the zero or return point of a counter
biased atmospheric pressure responsive member
or aneroid for a given ambient pressure, one of ,
said means being controlled by the atmospheric
pressure responsive member and the other of
said means being controlled by a temperature 40
responsive means.
'
Another object of my invention is to provide
an instrument which will utilize an outside sourceV
of power for .operating the gear train of the in
dicating mechanism, instead of utilizing the
` titudes from an assumed standard altitude due to
changes in atmospheric pressure caused by vari
ation in the temperature of the mass or’atmos
pheric air column above and below the assumed
standard temperature.
‘
Y
'
>Figure '1 represents a circuit diagram of a sys
tem embodying a second form of my invention.
Figure 8 is a front elevation of the control
panel for the form of my invention shown in Fig
ure'l.
'
_
Figure 9 represents a circuit diagram illustrat
ing a furthermodifled form of my invention.
Figure 10 is a front elevation of the control
panel for the form of my invention shown in Fig
ure 9.
relatively small movement and power of the at
Figure 11 illustrates graphically the eüect on
mospheric pressure responsive member or
barometric
pressure of variation of the actual
aneroid, and in addition to so arrange the pres
mean temperature from an assumed standard
sure‘responsive, member Vor aneroid that it will
temperature as the altitude increases and
have to work through only a very small range oi 50 mean
showing that the greater the rate of temperature
movement.
.
drop per unit change in altitude the lower the
Another object of my invention is to provide
barometric reading for any given altitude.
control means for adjusting or varying the re
In each of the curves of Figure 11 the ground
turn or aero point of the aneroid or atmospheric
barometric
pressure at sea level is assumed to be
pressure responsive member of my invention, for
‘760 millimeters of mercury. Starting with this
v a given ambient pressure, whereby the ratio
value, the line designated by the letter A indi
between barometric pressure and indicated alti
cates the relationship between altitude and
tude may be increased or decreased. '
barometric pressure under a hypothetical con
Another object of my invention is to provide
control means for varying the operative stand 60 dition wherein the temperature of the air is con
stant at all levels. The line indicated by the let
ard or translation factor oi an instrument such
ter B indicates the relationship between altitude `
as l; have mentioned in accordance with varia
and barometric pressure under a second hypo
tions in atmospheric conditions.
thetical
condition wherein the temperature of the
A further object of my invention is to provide,
atmospheric air at sea level is assumed to be _15° _
in an altimeter, a plurality of photoelectric cells
C. and there is a decrease in the temperature of
subjected to illumination from a source of light
substantially 1.13 degrees centigrade for every
and control means adapted to regulate the illumi
100G-foot increase in altitude until the isothermal
nation of the photoelectric cells whereby to cause
layer is reached at the 35,332 foot altitude level
actuation of the indicator means of the altim
where the air has a. temperature of -55 degrees
eter.
centigrade. Under such conditions the mean
An additional object oi my invention is to pro,
temperature of the air column is substantially
vide, in an altimeter, a balanced bridge circuit
-35 degrees centigrade. The line designated by
and adjustable means for unbalancing the circuit
the letter C illustrates the relationship between
so as to cause actuation of the- altimeter indi
75 altitude and barometrlc pressure under condi
catorÀ means.
'
'
2,412,541
tions most generally assumed as standard in the
calibration of the conventional altimeter: the
temperature ofthe atmospheric air at sea level is
_y
y
6
.
l
winding 1 comprise the input terminals oi' the
bridge circuit and a pair of, output conductors il
and l1 are connected respectively to center tap
assumed to be +15 degrees centigrade and for
Il and to a terminal 20 on conductor H. “Center
,every 100G-foot increase in altitude the tempera 5 tap
Il and terminal 20 constitute the output ter-`
ture decreases substantially 2 degrees centigrade
minals
of bridge circuit 35, and are connected
until the isothermal layer is reached at which
by
output
conductors II and I1 with the input
point the temperature of the air is -55 degrees
terminals 2| and 22 of a thermionic amplifier
centigrade. -Under such assumed standard con
indicated generally by the numeral 39, and hav
ditions the air column has a mean temperature of 10 ing
output terminals 23 and 24. This bridge cir
-20 degrees centigrade. The line D indicates
cuit is designed so as to be balanced when the
the relationship -between altitude and atmos
amounts of light supplied to the cells bear a pre
pheric barometric pressure under a hypothetical
determined
ratio to each other. Any decrease
condition wherein the temperature of the atmos
under the Ápredetermined ratio of the light sup
pheric air at sea level is assumed -to be +145 de 15 plied to cell 5 to that to cell 6 causes a propor
grees centigrade and there is a decrease in the
tional increase in the resistance of cell 6, un
temperature of the atmospheric air of 5.66 de
balancing the bridge circuit in such fashion that
grees centigrade for every 1000-foot increase in
a potential diiîerence appears between termi
altitude until the isothermal layer is reached with
nals
20 and I8 having the same polarity and
a temperature of -55 degrees centigrade. The 20
time-phase relation as the potential between ter
latter air column has a mean temperature of
minals Il and I 6, and of a magnitudepropor
+45 degrees centlgrade. ,
tional
to the unbaiance of the bridge. This po
The computations'of the aforenoted graph are
tential
difference is fed through conductors I5
derived from report No. 538 of the National Ad-4
and Il to input terminals 2i and 22 of ampliiler
visory Committee for Aeronautics and the alti
39.'
tude pressuretablescontained therein based on
Further,
an
increase
over
the
predetermined
the United States Standard Atmosphere. vIi’rom
ratio of the light supplied to cell 5 to that to cell
a study of the foregoing graph it will be seen that
6 causes a proportional decrease in the resistance the greater the rate of temperature decrease with
of
cell t, unbalanciiig the bridge circuit in such
change in altitude the lower the barometric read 30
fashion that a potential difference appears be
ing for any given altitude. Thus in an atmos
tween terminals liti and ‘i6 having the same po
phere where the rate of temperature decrease
larity and time-phase relation as the potential
with change in altitude is greater than that in
cliñerence between terminals it and it, and also
the standard atmosphere, the ’oarometric pres»
o1? a magnitude proportional to the unbelance ol"
'the bridge. This potential cliñlerence is also fed.
directly
Since to terminals
instantaneous
2i and 22
potential
ci amplifier
difference
sure at any level ‘is greater’than that in thegstand
arti atmosphere, and an uncorrected altimeter iri
dicates too low all altitude. Similarly, in an at-=
aerosols-ere where the rate oi” temperature decrease,
with change :in altitude is less than
iii the
with
between terminals
between
the î terminals
"’eiitial
and i@diiïerence
is 135°
ansi outimpresse
itor"will ~f
standard
osphere, an unoorreeted altiree‘ter 40 seen.
inrlieates too leigh en altitude.
across
resistance
terminalsof cell
and 22
is oi’
decreased.
amplifieris39oi’t lt“ e
lilly invention embodies means for automa@
loa y' eorreoting saisi erroneous iiie'hoations of an
'
e phase to that impress-eel on the e
" '
ait meter so that the instrument willi give »correct
'when
resistanse of
ne electronic ' amplifier
o1
tempes@
altiti
re `e ` indieetions
‘ litioos
n 'or
regardless
diverse
or" thefrom
ambient
of whether
those et the
'oh as sie
sl atmosphere.
"
25, i923, "
of my invention
means
if), and ii,
'
’
"'“
"~ of? oeil S
latter '
'
5 and. c eet
impe reses to constitute two aegee-exit
arms ci? a bridge circuit indicated generaliy by
the ninnerai de,
which the remaining two ati-ï
‘iaoent arms comprise the' halves
secondary
winding
’i‘erroinets it and itl ot secondary
¿
„ce secondary
lne
ane senses
i
~
N
`
y
f
l
'l
n
,_
2,412,541
7
oid 65 by the spring 41. Spring 41 is operatively
, As described in detail in the co-pending Upton
adjusted by cam 46, in response to motor 3|, so
as to increase or decrease the force exerted by
spring 41 upon the -aneroid 65, as .previously ex
application previously referred to, ampliñer 39
is of a type >which produces in the output circuit
including conductors 26 and 21 and motor wind
plained.
ing 33 an alternating current of the same fre
64 is adapted to be slidably ad- `
- The member
-quency and phase as the potential applied to
justed by a vernier adjustment knob 11 mounted
input terminals 2| and 22. Since transformer
on an instrument panel 54 whereby themeinber
primary windings 29 and l2 are both connected
64 may be move-d linearly vwith respect to member
to the same alternating current supply lines |3
_63,
whereby to vary theportion of aperture 62
10
and |4, it will be understood that the potentials
covered by member 63. Knob 11 has a pointer l89
appearing at the terminals 'of the secondary wind
for cooperation with suitable scale markings ycar
ings 30 and 1 are of the same phase. The cur
ried by panel 64, and is yconnected by a shaft 86
_ rent liowing through winding 32 is, however,
to vernier pinions 61 -which operatively engage
shifted substantially 90 electrical- degrees with
rack teeth 68 formed on the slide 64 as shown in
l respect to this potential by the condenser 38, as
Figure
3. The sh‘aft 68 is suitably journalled in
previously explained. The winding 33, on the
bearings
66 mounted on a fixed member 69.
other hand, is supplied with current either in
The cam 46 turns in a clockwise direction as
phase or 180° out of phase, with the terminal pothe altitude increases and is so shaped as to pro
tential of windings 1 and 30 depending upon the
20 gressively decrease the vertical adjustmentim
direction of unbalance of the bridge circuit 35.
parted to the roller 1| per unit of rotary motion
In accordance with the well known character
conveyed by shaft 45 as the altitude readings of
istics of a split vphase motor, when the windings
the indicator increase. Thus,v at ground level>
32 and 33 are supplied with currents 90° out of
for example, cam 46 is positioned so that roller
phase, the motor 3| is caused to rotate in a prede- '
1| is near its closest -approach to the center of
termined direction, depending on which of the
shaft
45, and upon a decrease in pressure the
currents lags and which leads.` The operation
aneroid 65 expands upward. -Since at `this point
of a split phase motor of the type described here
the relative movement of cam 46 necessary to
in is well .known in the art and is described` in
lower lroller 1| to increase the force exerted by
spring 41 to balance the circuit is relatively slight,
the indicator recording for such a movement is
lthe co-pending Upton application previously re
ferred to.
.
.
The motor-3| is arranged to drive -a shaft 40
’ in a direction depending upon the sense of -the
‘
»unbalance of the bridgecircuit 35 and the re
sultant phase oi the ‘current supplied from the
amplifier to the motor 3|. The shaft 40 is, in
turn .adapted bysuitable means such as a gear
Y correspondingly
slight.
However, at yrelatively
high altitudes, cam 46 is correspondingly ad
-justed so that roller 1| is relatively widely spaced
from the center of shaft 45, and considerably
' greater rotary movement of cam 1| is necessary
to cause suiilcientl increase of the spring tension
to return the slide 63- so as to balance the circuit.
This increases the necessary rotary movement of
the shaft 45 and causes a correspondingly greater
- is further adapted by suitable means such_as 40 indicator recording per unit of pressure change.
the shaft 40,' train of gears 4|, and a further . >'ll'his variation in the multiplication ratio of the
i shaft 45 to turna cam 46 which cooperates with
indicator means, as the altitude increases, is nec
a roller member 1| mounted on a loading spring
essary in order to approximate the true alti
41 for the adjustment` of the tension in the
since, as previously explained, the vertical
spring 41.V The loading spring 41 is pivoted at` tude,
distance
traveled for each unit of pressure fall
one end on a knife edge 12 4and operably engages
increases with the altitude.>
»
at the opposite end ananerold 65, exerting a com#
The operation of this portion of my„invention
pressive force on the aneroid 65 dependent in
will now be apparent. In the normal position of
magnitude upon the adjustment of „the tension
train conventionally indicated at 4I to drive an
indicator means 43, which isof a suitable type
well >known in the art. Moreover, the motor 3|
grêaintained in the loading spring d1 by the cam
the slider 63 the amount of light passing through
aperture 62 and falling upon photoelectric cell
6 is equal to the amount falling upon photoelectric
cell 5, and the bridge accordingly is in balance.
As shown in Figure 1, there is mounted be
tween the photo-electric cells 5 and 6 an illumi
Upon a decrease in atmospheric pressure, aner
nating lamp 5 l, energized through a suitable elec
65 expands, causing slider 63 to move up
tric circuit ëü; ‘this lamp provides the sole source 55 oid
wardly
to decrease the area of aperture |52 and
oí’ light for the cells. Suitable means are pro
thus to decrease the light falling on photoelec»
vided such as lenses E32 and 53 for directing the
tric cell f5. The resistance of the cell is thereby
light rays from the lamp Eil to the respective
increased, unbalancing the bridge circuit in a first
photo-electric cells 6 and 6g.
T
'
direction. The unbalance potential acts through
in order to control the supply> of light to the
ampliner 3Q to energize winding 33 of motor di
photo-electric cell 6 suitable control means are
in a iirst time-phase relationship. Motor 3i op
provided which, as shown in Figure 3, may com-y '
erates in such a direction as to rotate cam ¿3G in
prise' an adjustable member 66 having provided
a clockwise direction until the force exerted on
therein an aperture 62, for the passage of the light
,
aneroid tä'by spring ¿l1 has been increased by an
rays from the lamp 5i to the photo-electric cell
6, anda control slide 63 for regulating the supply
of light passing through the aperture 62 to the
photo-electric cell â. The control slide 63 is vop
eratively afñxed at one end to a resilient bellows
or other pressure responsive member 65 which
may conveniently be referred to as an aneroid,
65 and the loading sL ing d1. The expansive
force exerted by the aneroid 65 is counteracted
amount equal to the decreased compressive force
of the atmospheric pressure on the aneroid. lThis
increase in the force of spring ¿il .is accompanied
by a compression of the aneroid, and slider 63
moves downward with it, thus increasing the area
of aperture 62 until equal amounts of light fall
on both photoelectric cells. The bridge circuit is
vnow again balanced, and operation of moto!` 3|
is accordingly interrupted. actuation of the mo
by the atmospheric pressure acting upon the
aneroid 65 and by the force exerted on the aner 75 tor has at the same time resulted in changing the
- 2,412,541
reading oi member 43 so that it indicates a higher
altitude.
In the same fashion, upon- an increase in vat
mospheric pressure aneroid C5 contracts, caus
ing slide „to move downward to increase the
area of aperture 32 and thus Ato increase the
light falling on photoelectrlc cell l. v'I'he resist
ance of the .cell is thereby decreased, unbalanc
,
,
lo
tions varying altitude indications may result at
a given altitude level depending, upon the state
of the air column whether contracted or ex
panded.
In order to obviate inaccuracies in~ the indi-l
-cation of my instrument due to the eflect of tem
perature changes, Lhave provided in the form
oi' my invention illustrated in Figure l (as best
ing the bridge circuit in an opposite sense to that
shown in Figure 2) a ñxed light control mem
Just described. 'The unbalance potential actsl
through4 a'mpliner It to energize winding 33 o! 10 ber 82 having an aperture 33 of a selected out
line. A shutter -8| is pivotally attached by a
'motor 3| .in a second time-phase relationship
suitable pivot 80 to the ñxed member 32. The
which is also opposite that just described. Motor
pivoted shutter 3| is operatively connected by a
3l therefore operates this time in such a direc
rod 58 to a free air temperature responsive device
tion as to rotate cam ‘l 1n av counterclockwise 15 ofthe ñuid illled type including a bellows mem
direction, until the torce exerted on anerold 65
ber 59. The lower end of member 58 has con
bysprin’g il has' beenreduced by an amount
nected thereto a conduit 6G which connects
equal to thel increased compressive force o! the
remotely with a- free air thermometer bulb ele
atmospheric pressure on the4 aneroid. ‘This re
ment indicated by numeral 5 i . The thermometer
duction in the force of spring 41 is accompanied 20 bulb
element 6| is preferably mounted so as to
by an expansion of the aneroid, and slide G3
contact the free atmospheric air so that the
iiuid therein may respond volumetrically to the
moves upward >with it, thus decreasing the area
of aperture 62 until equal amounts of light fall
on both photoelectric cells.
The bridge circuit -
is again in balance and operation of motor 3| is
accordingly interrupted. This actuation of mo
tor 3| has, however, resulted in change in the
reading of member 43 so that it now indicates a
temperature of the free air atmosphere. It will
thus be readily seen that as the free air tem
perature decreases the member 59 contracts caus- «
ing the rod 58 to rotate the shutter 8| in a clock
wise direction about pivot 80, so as to progres
sively close the slot 83 and thereby decrease
the ñow of light to the photo-electric cell 5.
It will be understood that the resistance of cell 30
A manually adjusable turnbuckle 92 is pro
B is determined by the area oi aperture 62
vided for regulating the length of rod 58. It will
through which light from the source 5| may pass,
bè realized that the iluid contained in members
and that an increase of this area due to raising
59, 60, and 5| is also subject to expansion with
the upper edge by operation of knob 11 produces
lower altitude.
I
the same effect as an equal increase of the area
due to lowering the lower edge by the operation
of aneroid 85. If the barometric pressure at the
reference point is greater than standard, the
static pressure at all levels also exceeds that of
the standard for that level, and the aneroid is
at all levels compressed beyond the amount
which is proper for an accurate reading of alti
tude in the standard atmosphere for which the
instrument is calibrated. Thisin turn means
that aperture 62 is at all times o1' too great area.
It will now be apparent that actuation of knob
1l to move member 64 in a downward direction
has the effect of partially closing the‘aperture,
and that by suitably calibrating the rectilinear
response of aneroid 65 to changes in static pres
sure, the rectilinear movement of member 84 cor
responding to a unit of the scale on panel 54,
the graduations on indicator 43, the outline of
cam 46, and the tension in spring di (the out
line of aperture .62 also being considered) the
indicator may be made direct reading in altitude
above an arbitrary level, regardless of changes
release of pressure on bellows- 59 due to increase
of altitude. The actuation of» indicator 43 due
to the energization of motor 3| by amplifier 39
is dependent in magnitude on the ratio between
the resistance of photocells 5 and '6, that is. on
the ratio of the quantitiesof light impinging
upon the anodes of the two tubes. The rectilinear
response of bellows 59 to changes in pressure, its
response to changes in temperature, and the outu
line of aperture 83 are so selected that if the
length of rod 58 is adjusted by means of ‘turnn
buckle S2 to bring shutter 8| flush with the bot
tom of aperture 83 when the instrument is under
standard conditions at the reference point, the
relative occlusion of apertures 83 and 62 with
rise of the craft through a standard atmosphere
50 causes uniform increment in the indications of
indicator 43. For a rise of the instrument
through an atmosphere having a temperature
gradient other than standard the relative oc~
clusion of aperture
by shutter Si is deter«
mined as before by the joint effect of temperature
and pressure changes on
taking place
a
different rate so theta factor proportional to
in the density of the air. The reverse of this
the departure of the temperature gradient
is true if the pressure at the reíerence point is
through which thecrait is rising from the standn
below standard.
As I have previously explained in connection 60 ard gradient is introduced into the signal elîect«
ing actuation of indicator
It will further be
with Figure ll, the barometric pressure at any
noticed that this factor occurs independent of
altitude, and therefore the pressure altitude or
and may occur simultaneously with change in
indication of an uncorrected altimeter, is in-~
the factor iniiuenced by variation in pressure,
fiuenced by the mean temperature of the air col»
umn between the observer and ‘the ground. This 65 controlled by member G3 and aperture di?.
The purpose of turnbuclrle t?? is to bring; the
I have illustrated in Figure 6, which shows that
upper surface of shutter di flush with the lower
although the indicated altitude under high and
low mean temperature conditions is the same
as the actual altitude under the standard tem
perature conditions, the actual altitude of the
observer is above the indicated altitude in the case
of high mean temperatures and below it in the
case of low mean temperatures.
lThus, it will »be seen that under such condi
portion of aperture d3 in the beginning oi’ the .
rise of the craft, so that there will be no period
during which the shutter is moving with respect
to member 82 and yet not'varylng the occlusion
of aperture 83. Not only the temperature gradi
ent through which a craft must rise from a given
reference level, but the temperature at the start
ing level may vary from the standard. The
2,412,541
12,„
traction 'of the gas mass or free atmospheric air
mechanism I have just described has been pro
` column resulting from changes in the tempera
vided to permit correction of the instrument for. _`
ture thereof above or below an assumed standard
variations in gradient, but I also provide means
for correcting the indications of the instrument
As is well known in the art and graphically
value.
for variations in the temperature at the refer
ence level. For this purpose there is provided a
slide 88 having mounted thereon rack teeth 8'!
'
-
`
shown in Figure 11,l the vertical distance traveled
for each unit of barometric pressure , fall in
creases with the altitude. Therefore, in order
to secure a scale evenly divided in altitude units
pinions 85 are' connected to a shaft 84 journalled
the ratio of the movement of the indicator means
10
in bearings 44 mounted on the member 82, the
43Ito the deflection` of the pressure responsive
shaft 84 projecting through a suitable control
element 85 must vary continuously with the alti
panel 54. Mounted at the free end of the shaft
tude. For this purpose'the cam 46 is so shaped
84 is an adiustment‘knob 48 having provided a
that the movement of the cam ¿it required for
pointer 42 for cooperation with suitable scale
unitary- increase in the tension in spring 41 in
markings on the control panel 54. Thus, by ad
creases as the indicated altitude increases so
justing the knob 48 .the slide 88 may be raised or
that the ratio between unit increase in altitude
lowered with respect to the slot 83 and-the i'low indications and unit of atmospheric pressure fall
of light to the cell S‘through the slot 83 thereby
is properly increased with the altitude.
adjusted.
’
This is specifically accomplished by construct
It will be understood that the resistance of cell 20 ing the cam 46 so that the pitch of the actuating
5 is determined by the area of aperture 83
cam surface decreases in proper proportion for
through which light from source 5| may pass,
the assumed standard of operation as the cam is
and that'an increase of this_area due to raising
turned in response to a decrease in atmospheric
operably engaged by a pair of pinions 85. The
the-upper edge by operation of knob 48 produces
pressure or rise in altitude. Thus as the altitude
the same effect as an equal increase of the area 25
increases the rotary movement of the cam 48
-due to lowering the lower edge by operation of Y
bellows 58. 1f the temperature at the reference
pointis above the standard, bellows 59 is ex
' panded and shutter 8|, if adjusted to the lower
edge of aperture 83 under standard conditions,
necessary to return the aneroid to the 'starting
- or zero position is increased per unit of pressure
has now taken a position below the edge of aper-ture 8| in an effort to still further increase the'
area for light flow. ,
fall.
,
Further,
as previously explained,
as the tem-_
perature of the atmosphericlair contacted by the
bulb 8| decreases, the shaft -45 is rotated by the
motor 3| so as to turn the "cam 46 in a counter
clockwise direction decreasing the tension of the
Movement of shutter 8| below the point at
loading spring '41 s_o that the aneroid 85 may ex
which lit coincides with the bottom ofl aperture
pand upward to a position where slider 63 so
83 introduces error into the device, since it makes
no actual change in the area through which light ' limits the passage of ~`light to photoelectric cell
6 that the bridge circuit 35 is balanced. `
may pass to impinge on cell >5. It is necessary
Figure 11 shows that the barometric pressure
that the shutter have that position of coincidence
with respect to aperture 83 at the beginning of a 40 at an altitude of 25,000 feet in a standard at
mosphere is 278 millimeters of mercury: in the
flight. Therefore turnbuckle 92 is adjusted to
atmosphere of lower mean .temperature the
set shutter 8l in coincidence with the bottom- of
pressure is 290 millimeters, while in that of higher
\ the slot, and the area of aperture 83 is increased
mean temperature the pressure is 255 millimeters.
, by actuation of knob 48 to provide the necessary
- An uncorrected altimeter is calibrated in terms
ratio of light impinging on cell 5V and 6 respec
of the standard atmosphere, and therefore reads
tively. This light ratio acts through the bridge
24,250 feet in the colder atmosphere and 27,500
and amplifier to’energize motor 3| in such `fash
feet in the warmer atmosphere, although the
ion as to move indicator 43 to a position consist
ent with the departure of temperature from the ì plane is actually at an altitude of 25,000 feet
in each case. In order to bring about a correct
standard, and this corrects the instrument for 50 reading
of my altimeter in the warm atmosphere,
temperature variations at the reference point.
.my spring -46 must increase its pressure upon
It will be appreciated that an increase in the
illlnnination falling on photoelectric cell> 5 (which
lowers its resistance) is eiïectively the same in
the bridge circuit asa decrease in the illumina
tion of photoelectric cell 6 (which raises its re
sistance) , and that the opposite is also true. »r
VAs the temperature decreases the shutter 8|
pivots upward so as to progressively close a por
aneroid 85 by an amount equal to the pressure
differential between 27,500 feet and‘25,000 feet
or, 23 millimeters of mercury. The aneroid is
actually working in the 27,500 foot range while
the indicator and therefore cam ¿i6 is Working
in the 25,000 foot range. Similarly, in order to
bring about a correct reading of my altimeter
tion of the slot 83 thereby decreasing the light 60 in the colder atmosphere, my spring e5 must de
crease its pressure upon aneroid 65 by an amount
supplied to the cell 5. If the decrease in tem
>equal to the pressure diñerential between 25,000
perature is at a rate greater than that in the
feet and 24,250 feet: that is, by l2 millimeters of
standard atmosphere, this decrease in light is
of such magnitude as to unbalance the bridge in V mercury.
Now suppose that the craft rises to an actual
the same sense as motion of member 03 .down 65
elevation
of 26,000 feet. In the standard at
ward: that is, motor 3i is- actuated to decrease
the pressure is 268 millimeters of mer
the reading of the indicator and to reduce the ’ mosphere
cury. -In a colder atmosphere it `is 278 mil
force of 'Spring 4l on aneroid 65. A decrease in
temperature thus hasv the same effect onl the
bridge circuit and the motor as an increase in
pressure due to a decrease in altitude.' 4An in
crease in temperature has the opposite eiïect.
_The 'introduction of these factorsinto the read
ings of the instrument corrects the instrument Y
' for errors introduced by the expansion 0l' 09n- .
limeters, and in a Warmer atmosphere it is 242
millimeters. The change in pressure in the
standard- atmosphere is 10 millimeters. In a
colder atmosphere the change is 12 millimeters
while in the warmer atmosphere the change is 13
Vmillimeters. The indicator of my compensated
altitude must'ndiove through a distance propor
13
2,412,541
` tional to the change o! 10 millimeters, regard-_
less of the atmosphere. My temperature com
pensator, therefore, alters the operative standard
l» of the altimeter so that the same change in in
dicated altitude takes place whether the change
in barometric pressure be 10 millimeters in an
atmosphere of standard temperature, 12 mil
limeters in a warmer atmosphere, or 13' mil
limeters in a colder atmosphere.
In certain simplified applications it may not
be desired to have the temperature responsive.
device include both responsive and manually
operable members. In such an application a
modified form >of means for controlling the light
14
ing a common terminal |30. 'I'he resistance III
is connected'to the impedance coil II3 by a con
ductor |I8 While the resistance II2. is connected
to the impedance coil |I4 by a conductor H9.
A pair of terminals |32 and |33-v are located on
’ conductors H8. and IIS, and constitute the input
terminals of the bridge circuit.A The bridge is
energized from the secondary winding |22 of a
:transformer |23, to which connection is made
10' by conductors
|20 and I 2|'. Current is provided
_
in secondary winding |22' by transformer action
. from primary winding |24, which is supplied with
alternating current from any suitable. source by
I25iand I 26. .
.
"
supplied to photo-electric cell B_may be provided 15 conductors
Terminals
|30
‘and
l3-I
comprise
the
output
such as shown in Figure 4, wherein-a fixed light
terminals yof Abridge circuit- H0, and are con- '
control member 95 is provided having formed
therein an aperture 96. Ailixed to a. shaft 91
pivotally connected to the member 95 is a shutter
S8. Mounted on the shaft 91 is also a gear 99
intermeshing with a second gear 14 aiiixed to
one end of a control shaft 15 which is journaled in
a, bearing arm 49 projecting -from the member
95: said shaft 15 passes through a suitable aper
ture formed in the control panel 54. A control
knob 55 is mounted on the shaft 15 for addust
` ment of the shutter 98. A pointer 56 may be
y provided on the knob 55 for cooperation with a
suitable indicator scale as shown in Figure 5.
The member 95 and control shutter arrangement
may be readily substituted for the temperature
responsive control shutter for controlling the
illumination passing from light 5I to the photo
electric cell 5 the amount of light passing through
the aperture 96 being controlled by the position
of the shutter 98.
An altimeter of the type embodying manually
adjustable control means such as shown in Figure
5 is readily adapted for use Where accurate cor
rection factors are available.
Thus, for example, if a ground operator in a
commercial air line organization ñnds that in
order to correct the ground altimeter so as to
indicate the actual ground altitude at the ground
level it is necessary to adjust the position of knob
11, such information can be conveyed by radio
to the pilot of the plane. Similar information
regarding the temperature at the ground station
may be given to the pilot in the same way.
The
information supplied to the pilot enables him to
operate knobs 418 and 'El so that suitable correc
tion for change in the atmsopheric condition at
the bottom of the column of air may be made.
The altimeter then operates at an assumed stand
ard based upon actual ground atmospheric con
ditions rather than upon an assumed standard
based upon an assumed ground atmospheric con
margin
dition. of
lThus,
erroratisrelatively
the altitude slight
to be measured
since the in
dicated altitude is in error at Ythe point of
measurement only insofar as the atmospheric
conditions at such. point varies from the known
ground atmospheric conditions rather than from
an assumed ground atmospheric condition.
Further, if desired, the reading of the altimeter
may be corrected for temperature conditions
existing at the upper level or point of flight or for
the difference between the ground temperature
and the temperature at the flight level.
ln a further form of my invention illustrated
by Figure 7 there is provided a variable reluctance
or impedance bridge circuit indicated generally
by the numeral itil and including variable re
sistances Hi and lili having a common ter
minal I3l and impedance coils lit and ttt hav
nected as by conductors I 21 and |28 with input ,
terminals |36 and> |35 of an amplifier I25lhav
ing output terminals |36 and |31.
'
`
It will be readily seen that the coils II3 and
H4 form two adjacent arms of the variable im.
pedance bridge circuit I|0. The variable resist
ance windings l I| and I i2 form the opposite arms ~~
of the bridge circuit I I0. v
Coacting with the coils II3 and II4 is a mov
able core II5. The core I l5 of magnetic mate
rial is operably connected by a rod IIS to an at
mospheric pressure responsive member or aneroid
II1.
’
The bridge circuit l I0 is so arranged that nor
_mally with the core I I5 positioned substantially
equally within the two coils I I3 and I I0 the vbridge
circuit IIO is ìbalanced and no potential appears
across output terminals I 30 and I3I.
However, upon a decrease in atmospheric pres
sure permitting the expansion of the aneroid
II1, the core IIS moves upward.
The core II5
then approaches further toward or extends fur
ther into the coil I i3 and is correspondingly re
moved further from or project less into the other
coil I I4. The magnetic flux threading the coil
I I3 therefore increases, increasing the impedance
of the coil H3, and the flux through the coil llt
decreases, decreasing the impedance 0i the coil
IM, thus unbalancing the bridge circuit in such
fashion that a potential diiîerence appears be
tween terminals IM and |35 having the same
polarity and time-phase relation as the potential
difference between terminals i90 and lilo, and of
a magnitude proportional to the unbalance of
the bridge. This potential diñerence is fed
through output conductors it? and lift to input
terminals i3d and E35 of amplifier E
Further, upon the atmospheric pressure in
, creasing so as to cause the contraction of the
aneroid lil and the downward movement of the
core liti past the balancing point of the bridge
circuit itil, the impedance of the coil ¿it? is de»
creased and the impedance of the coil
inn
creased unbalancing the bridge circuit in such
fashion that a potential difference appears be
tweenterminais
and iSEî having the saine
polarity and til „efphase relation as the potential
difference between terminals it@ and ritt, and
also of a magnitude proportional to the unbal
ance of the bridge. This potential difference is
then reddirectly to terminals i3@ and E35» of
amplifier t2@
Since the instantaneous potential diiîerence be
tween conductor ital and terminal
is 180°
out of phase with that between conductor H9
and terminal iëlii, it Will be seen that the poten
tial difference impressed across terminals ißt and
S35 of ampli?ier l2@ when the impedance of coil
tit is increased is
that
2,412,541
shaft |50, train of gears |5| and shaft |56, to
>impressed on the amplifier input when the im
pedance of coil ||4 is increased. It should also
turna cam |58 so as toV adjust the tension of a
loading spring |59 for a purpose which will here
be pointed outthat an‘increase in the impedance
of c'oil'- |'f'l'3" ïëiìectively the same-as a _decrease
in tneimpedäriöë ¿recu m.
'
i
.
'Inefajrnpriner |529 may' be any suitable type
inafter be explained.` The `cam |58- cooperates
' with a roller member 4| 60Ímounted on the loading
of '
electronic 7 aiñplif-i’er ` well? 'known in_ the yart _such
as shown or” example îin the _previously’n'oted
4spring |59 for thé adjustment of the tension of
the spring |59. ' The loading spring |59 is plvoted
at one end cna ñxed knife edge |62 and engages'v
the oppositefjend _theaneroid ||`| exerting
PatentrNc:51586233; granted May 25.21926, to 10 aatforce
'thereon vd`ef_ae'r_i<_ìent upon the adjustment
Anschut‘z-Kaeinpfe, or may be preferably an elec
tronic »amplifier ofthe `type shown and 'described
in the; aforenoted co-pending application- 'of Al
herring-fuma, serial No. 437,561, dated Aprile;
ofthe cam |58.
nIt] will be seen that upon a decrease in pres
sure; aston a'rise Ain altitude, the aneroid ||1
expands forcing‘the rod H6 upward against' the
of the spring |59. Moreover, the upward
A motory '| 45 is shown as being of the split phase 15 tension
movement of the rod ||5 likewise moves the core
type having a pair'of field windings |45 and |41
H5 upwardl _which as previously explained in
which are mechanically 90 degrees apart in phase.
the-impedance of the coil ||3 and de
Winding |41 is connected bythe conductors |43 _Í creases
creases the impedance of the coil ||4 and thereby
and |44 to thevoutput terminals |36 and |37 of
cause an unbalancing of the variable reluctance
the amplifier |29,'j. "
' `
bridge circuit ||0. The unbalanced potential is
A transformer |4|'is provided for continuously
amplified by the Vamplifier |29 in a> manner pre
energizing the motor winding |4|i,¿saidV trans
viously described and the thus ampliñed electro
motive force drives the motor |45 so as to rotate
ondary winding |42. The primary winding |40 is
connected 'through conductors |38 and .|39 to 25 the shaft |50 in a direction to-cause the actuation
„former having a primary winding |40 and a sec
conductors |25 and |26 which are in turn con
nected to a suitable source of alternating current.
of the indicator means |52 in a manner well'
known in the art so as to indicate an increase
in altitude. Moreover, the motor also, upon such
Current is supplied to the secondary'winding
unbalancing of the bridge circuit ||0, turns the '
|42 through transformer action from the primary
winding |40. Motor winding |46 is continuously 30 shaftA | 56 through the shaft |50 and intermeshing
gear means I5I to turn the cam- |58 in a clock
energized from the secondary winding |42 of the
wise
_direction so as to cause downward movement
transformer |4|. A condenser |48 is connected
of- the roller |60 thereby increasing the tension
in series between the secondary winding |42 and
exerted by the spring |59 on the aneroid ||1.
the motor winding |46 and causes a p_hase dis
in turn causes the contraction of the aneroid
placement of substantially 90° between the cur 35 This
|
l1
under
the atmospheric pressure and the addi
rent ñowing inthe winding |45 and the termi
tional tension of the loading spring |59 to cause A
nal voltage of the secondary winding |42.
Y
movement of the rod | I6 until the core
As described in detail in _the co-pending Up-. ' downward
||5 is- -once' again positioned in such a manner
ton application previously. referred to, the am
as to balance the bridge circuit ||0, whereupon
plifler £29 is of a type which produces in the
the motor |45 ceases actuating caml |58 andthe
ybranch of the output circuit including conduc
tors |43 and |44 and motor winding |41 an alter- .
indicator means |52.
nating current of the same phase and frequency
as the potentiall applied to input terminals |34
in the case of a decrease in altitude, the aneroid
and |35. Since transformer primary windings |24
and |40 vare both connected to the same alternat
ing current supply lines |25 and |26, it will be
understood that the potential appearing at the
« terminals of the secondary windings |22 and |42
'are of the same phase. The current liìowing
through winding |46 is, howeveryshifted sub
stantially 90 electrical degrees with respect to
this potential by the condenser |48, as previously
explained. The Winding |41, on the other hand,
vis supplied with -current either in phase or 180°
out of phase with the :terminal potential of wind
ings |22 and |42 depending-upon the direction
`
Upon an increase in atmospheric pressure, as \
||'|l contractsv causing a downward movement
of the rod | IB and causing the core I I5 to increase
the impedance of coil | |4 and decrease the im
peda'nce of coil | I3. The amplified unbalanced po-tential of the circuit ||0 now `causes rotation of
the motor |45 in a direction opposite to that in
the preceding paragraph, moves the indicator
means to indicate the decrease in altitude and
rotates the cam |58 ina counter-clockwise direc
tion so as to decrease the tension of the loading
lspring |59. The decreasing tension of the spring
|59 permits expansion of the aneroid ||1 and up
ward movement of the core ||5 to a position bal- A
ancing the bridge circuit ||0, whereupon theun
of unbalance of the bridge circuit | it.
balanced potential -ceases and the flow of ampli
In accordance ,with well known characteristics
of a split phase motor, when the windings |48 60 fied current to the motor |45 terrr'iinates. _The
movement of the motor ~|45 thus stops until the _
and |41 are supplied with currents 90° out of
bridge circuit H0 is once again unbalanced.
phase, the motor |45 is caused to rotate in a
Cam |58 turns in a clockwise direction as the
predetermined direction. The operation of a split
indicated altitude increases, and the function of ' '
phase .motor of the type described herein is de
this cam is the same as that of cam 46 clearly set
scribed in the co-pending Uptonapplication pre
forth previously.
.
_ »
.
viously referred to.
_
_
In order to more accurately adjust the altimeter
The motor |45 is adapted to drive a shaft |53
lby taking into account the barometric pressure
in a direction depending upon the unbalancing
`
at the ground and for variations from the
of the bridge circuit | i0 and the resultant current
standard mean temperature at the upper level,
supplied from the ampliñer to the motor |45.
I have provided the adjustable resistances ,i ii and
The shaft |50is, in turn, adapted by suitable means
H2 which under assumed standard starting or
such as the gear train |5| to drive an indicator
ground-level conditions are of equal resistance.
means |52, which is of a suitable type well
known in the art. Moreover, the motor -|45 is y . The variable resistance ||| is -adapted to be oper
further adapted by suitable means such as the 75 ated by a~knob |0|, as shown in Figure _8, so
2,412,541
18
@that upon a decrease in barometric pressure
separate manually operable electricalv control
' , vbelow the assumed standard for the ground or
means for adjusting the altimeter for ground at
mospheric pressure and for changes in the tem
perature of the free atmospheric air whereby the
starting level, the resistance || I may be increased
in accordance with a predetermined adjustment
scale and thereby cause the unbalancing of the
bridge circuit IIO, and an unbalance potential
return or zero point of the aneroid may be ad
justed and the multiplication ratio of the indi
cator means varied. Thus, the standard of op
eration of the altimeter may be adjusted so as to
operate accurately with’a minimum of error un
10 der conditions other than those `ol” the standard
to which the instrument was calibrated. In the
form of my invention disclosed in Figure 7, if the
temperature gradient of the air column approxi
‘mates that of the assumed standard. and the
154 above described'adiustment is made for ground
therefore appears across terminals |34 and |35.
This unbalance potential ampliiied, as previously
explained, then causes the motor |45 to rotate
in a manner previously described so as to decrease
the altitude readings and to turn the cam |58
in a counter-clockwise direction so as to decrease
the Aratio between change in indicator readings
andpressure change, and to decrease the force
exerted by the loading spring |59 on the aneroid
| I 1. The decrease in tension of spring |59 in turn
temperature deviation from the standard, the
causes the core- ||5 to rise- until the impedance
cam arrangement I 58 and spring |59 are so con
of coil II3 is increased and the impedance of
structed as to increase the multiplication ratio of Y
coil || 4 decreased to a point whereupon `the
the indicator means as altitude increases. The
bridge circuit ||0 is once again balanced. Thus, 20 instrument thereby properly reilects an increase
correction is affected for altitude readings twhich
in vertical distance traveled per unit of pressure
if uncorrected would under an assumed indicator
as the altitude increases.
standard read too high duev to a decrease in the
However, vunless further compensated, such a1
pressure of the air column at the ground or start
titude readings may depart from the true alti
ing level of the measurement.
'
tude insofar as the temperature gradient or mean
Further, upon an increase in the ground baro
metric pressure causing the altimeter at the orig
lnal standard of operation to indicate an alti- Y
tude below tthe true altitude, the resistance III
temperature of the actual air column diiîers from
that of the assumed standard atmosphere. The
extent of such error as shown in Figure 11 is sub
stantially negligible at the relatively lower alti
may be decreased by adjustment knob I0| in ac 30 tudes but the error increases with the altitude
cordance with a predetermined adjustment scale
and represents a substantial error particularly
as shown in Figure 8, causing the unbalancing
at the greater heights.
of the previously balanced bridge circuit I I0 so
In order therefore, to compensate for such
that the current due to the unbalance potential
errors, I have further provided in the form oi.'
flows through the resistance III and coil ||4
my invention illustrated in Figure 9 automat-ic
causing in turn the motor |45 to rotate so as to
temperature correcting means. Thus, I have pro- turn the indicator |52 to increase the indicated
vided an electric thermometer or resistor |80 of
altitude. The motor |45 simultaneously turns
the cam |58 in a clockwise direction so as to in
crease the ratio between pressure change and -'
' change in indicator readings, and to increase the
tension in spring |59 whereupon the atmospheric
pressure acting upon the aneroid II'I together
with the increased compressive force of spring
|59 tends to force the core ||5 downward until
the impedance of coil ||4 is increased and the
impedance of coil | I3 decreased to a ,point where
upon the bridge circuit |I0 is once again bal
anced. Thus the standard of operation of the
altimeter may be‘adjusted for the actual pres
sure conditions existing at the ground or start
ing level of the measurement.
It will be obvious that the effect of varying the
>resistance `of the resistor II| in this modification
a metal lsuch as nickel having a positive tem
perature coeflicient of resistance. The resistor
|80 is mounted so as to be directly affected by
the temperature of the free atmospheric air.
'Thus, upon the temperature of the free atmos
pheric air decreasing the resistance of the mem
ber |80 will be reduced, and similarly upon an
45 increase in the temperature of the free atmos
pheric air the resistance of the member |80 will
be increased. A micro or milli voltmeter IBI is
shunted across the resistance |80 and is directly
aiîected by the variations in the resistance there
50 of caused by the rise or fall of the temperature
of the free atmospheric air. The meter |8| has
a scale graduated so as to indicate degrees of
temperature oi the free atmospheric air acting
upon the resistor | 80. A switch |03 is provided
of the device is the same as the effect of varying 55 for connecting the meter IBI in and out of the
the setting of knob 'I1 in my first embodiment.
circuit.
'
In a similar fashion, varying the resistance of re
Resistor |80 is connected in series with a var
sistor I|2 in the present modification has the
iable resistance |83 which may be formed of a
same unbalancing effect on bridge circuit IIO as
material such as manganin the electrical resist
varying the setting‘of knob 48 or knob 55 in my 60 ance of which is relatively unaffected by tem
ñrst embodiment.- A decrease in the resistance
perature change. Resistors |80 and |83 form
of the resistor ||2 unbalances bridge circuit ||0
one arm of a bridge circuit |82 which is otherwise
in the same direction as an increase of the im
essentially'the same as the bridge circuit ||0
pedance of winding |I4,v energizing the motor to
previously shown in Figure 7 wherein like nu
operate the indicator'and rebalance the bridge
merals indicate similar parts. The resistance of
by means of core I |5.
^
the variable resistance |83 is so arranged that
A knob |02 is provided for adjusting the resist
at the ground or starting level the same may be
ance of resistor II'2. and the knob may have a
manually varied by adjusting the knob |05, Fig
pointer for cooperation with graduations suit
ure 10. The knob |05 has a pointer |08 co
ably calibrated in temperature units to give cor
related interrelation between actuation` of knob
|02 and the remainder of the device, these grad
nations being carried by a suitable control panel;
It will thus be seen that in the form of my
invention illustrated in Figure 7, I have provided
\
operating with suitable scale markings whereby
the resistance |83 may be increased proportion
ately as the temperature of the atmospheric air
at the starting level decreases below the assumed
standard causing in response thereto the re--
sistance of the resistor |80 tor‘decrease as the
2,412,541 -_
~ 20
v
'
the temperature at the lower and upper level of
temperature of the free atmospheric air de
Thus, the resistance |83 compensates
measurement.
creases.
-
»
Although several embodiments of the inven-A,l
`tion have been illustrated and described injde-f.v ¿.
vention
tail, it isisto’be
not limited
expressly
thereto,
understood
and that
that the
various1
Ain-y .;- _.
for `the other variable resistance |88 at the
ground level. Similarly theresistance |83 may
.be manually adjusted so as to decrease propor
tionately as the resistance of the resistor |80 is
increased in response to a temperature rise at
the ground or starting level. Thus, at the
changes may be made in the design and arrange- ~ .
ment of the parts without departing from the
- spirit and scope of the invention as the same
ground level theeiîect of the one cancels the
effect of the other and the _temperature com 10 Awill now be understood bythose skilled in the
pensating means at the ground or starting level
does not cause the altering of the indicator
art. For a definition of the limits of the inven
tion, reference will be had primarily to the ap-v
reading. Any change in the ground reading due
pended claims.
v`
I claim as my invention:
to a variation from the standard of the atmos
pheric pressure atthe ground> level is com
15
,
'
1. An altimeter comprising, in "combination,
an- atmospheric pressure responsive means, an _
pensated by the adjustment of the variable re
sistance |l| in the manner previously described .
altitude indicatingV means, adjustable transmission means- for driving the 'indicating means
in accordance with the response of the atmos
~with reference to the form of Figure 7. How
ever, durlng flight the resistance |83 may be>
20 pheric pressure responsive means, and means for
manually adjusted by _the knob |05 in accord
adjusting the transmission means whereby the
rate of change in altitude indications for unit of
acce with suitable scale markings such as shown
in Figure 10 for actual atmospheric tempera
ture at the ground level, which information may
be conveyed to the operator by radio or other
atmospheric pressure change maybe varied, said
adjusting ' means including a first and second
'manually operable means to regulate Said oper
' suitable means.
However, upon the altimeter being raised by an
airplane `or other suitable means through the air
column, the resistance |83 after adjustment to
~ground temperature conditions remains constant
as it is not subject to variation in the tempera 30
ture of the atmospheric free air, while the re-~
sistance of the thermometer resistor I8@ varies
with the temperature of the free atmospheric
air, thereby varying‘the resistanceof the arm of
the bridge circuit |83 including the resistances _ -
ative standard in accordance with first and sec
ond atmospheric conditions existing at the vstart- v
ing level of measurement and third means to
regulate vsaid operative standard in accordance
with the variation, from an assumed standard,
of an atmospheric condition existing at the level
oi measurement.
'
` 2. An altimeter- comprising, in combination,
an atmospheric pressure responsive means, an
altitude indicating means, adjustable transmis
sion means for driving the indicating means in
|83 and |80. However, since the resistance |83
remains constant after adjustment to ground
accordance with the response of the atmospheric
pressure responsive means, and means for ad
atmospheric temperature and the resistor l|8il
changes in accordance with the temperature oi ,
justing the transmission'means whereby the rate
the atmospheric free air, it will be readily seen 40 of change in altitude indications for unit of at
mospheric pressure change may be varied, said »
that the eiïect of such arrangement is to con
adjusting means including a manually operable
tinuously adjust the operative standard of the
-means to regulate said operative standard inac
altimeter while passing through the column of
cordance with atmospheric pressure conditions
air for an average temperature between that
existing at a starting level-of measurement and
existing at the lower end of the column of.' air
further means to regulate said operative standard
and at the point of measurement. It will be ap
in accordance with temperatures of the free at
parent that the function performed by resistor
mospheric air existing at the starting level and
|80 in the present modification of my invention
at the level of measurement.
is strictly analogous so that performed by mem
3. An altimeter comprising, in combination, an
` ber 8| and so forth in the modification disclosed 50
atmospheric pressure responsive means, an alti
by Figure 1, and that members 8| and 86 of Fig
vtude indicating means, transmission means for
ure 1 together are the equivalent of members |85
and |83 in the present modiñcation.
driving the indicating means, adjustable in' ac
~
In summary, it Will be seen that I have pro
vided novel compensating means for an alti
cordance with- the response of the atmospheric
55 pressure responsive means, and means for adjust
meter whereby the-calibration of the instrument
may be adjusted at any time to accord with the
atmosphere through which the craft is iiying.
ing the transmission means whereby the rate or
change in -altitude indications for unit of atmos
pheric pressure change may be varied, said ad
justing‘means including first manually operable
' '_I'he device operates Without adjustment in a
means to regulate said operative standard in ac
, Vstandard atmosphere, and is adjustable, in part 60
>automatically and in part manually, `to accord
with the deviating conditions of any other at
mosphere. Manual adjustment is provided for
both pressure and temperature at the ground
level, and automatic adjustments maintain the
instrument in constant calibration ‘with regard
to the pressure and temperature of the ambient
atmosphere.
_
.
There is thus provided a novel altitude gaug
ing apparatus which provides a continuous auto
cordance with atmospheric pressure conditions
existing at a starting level of measurement, sec
ond manually adjustable means to regulate said
operative standard in accordance with the tem
perature of the free atmospheric air existing at
the starting level of the altitude measurement,
and third -means for iniluencing said operative
standard in accordance with the temperature ,of
the free atmospheric air existing at the level-of
the altitude measurement, said second and third
_means arranged in such a manner as to regulate
tude in accordance with the vertical mean tem
perature distribution in the column of airv
said operative standard in accordance with the
arithmetic mean of the temperatures oi’ the free
atmospheric air at the starting level and at the
through which the apparatus passes based 119011 75
level of the altitude measurement. '
matic means for` correcting the indicated alti
'
2,412,541
«2l
y4. An altimeter comprising in combination an
atmospheric. pressure responsive means movable
a bridge- circuit, a plurality of adjustable mem
pressure responsive means, a resetting mecha
' ybers for controlling the electrical balance o! said
circuit, a first condition responsive means and
a second- condition responsive means,> operating
nism actuable to varyl the force of the counter
biasing means in such a manner as to return the
atmospheric pressure responsive means from the
second position to the ñrst position, means op--
to unbalance the circuit, indicator means, means
actuating said indicator means upon the unbal
ancing of the circuit, biasing means effective upon
from a ?lrst position to a second position, a coun
»ter biasing means acting upon the atmospheric
the said adjustable members in such a manner as
actuation to alter the response of one of said con- eratively connecting said responsive means with 10 dition
responsive means, and means actuatingsaid
said resetting mechanism in controlling relation
biasing
means, upon unbalancing of Ithe circuit,
thereto, said last named means including first
in such fashion as to alter the responseof the
and second manually operable means for actuat
last named condition responsive means> to rebal
ing the resetting mechanism so as to vary the said
return position of the measuring member, iirst 15
visual- indicating means whereby the position of
' ance the circuit.
8.' An instrument comprising in combination a
measuring member movable from a iirst posi
tion under influence oi’ the forces to be meas
related With specific values of atmospheric pres
ured, a biasing >means acting upon the meas
sure, and second visual indicating means where
uring member, a sourceof light, a plurality of
by the position of said second manually operable 20 photo-electric
cells arranged yto be equivalently
means may be correlated with specific values of
illuminated
from
said source, whereby to induce
atmospheric temperature.
equivalent electrical responses from said cells,
5. An altitude measuring device comprising in
control means actuated upon movement of said
combination, a plurality of electrical resistors
measuring member for varying the ratio of light
forming an electrical bridge circuit, two of said
said first manually operable means may be cor
supplied> to said cells in such a manner as to dif
resistors being adjustable for atmospheric tem
ferentially affect said responses of said cells, mo
perature and atmospheric pressure conditions at
.tor means controlling the actuation of said bias
the starting level of the altitude measurement,
ing means, and means causing energization of
another of said resistors responsive to atmos
pheric temperature and having electrical charac 30 said motor means in accordance with differential
responses of said cells, whereby to actuate said
teristics variableby changes in atmospheric tem
biasing means in such a. manner as to cause the
p'erature, a slidably mounted magnetic core sur
return of ~the measuring member to the iirst po
rounded by inductors in opposed legs oi’ said
bridge circuit, an atmospheric pressure respon
9. An instrument comprising in combination a
sive member operatively `.connected to said> core
measuring member movable from a ñrst position
>whereby upon movement of said atmospheric
under influence of the ¿forces to be measured, a
pressure responsive member movement is impart
biasing means acting Jupon the measuring mem
ed to said core in such a manner as to vary the
ber, a source of light, a plurality of photo-electric
impedance in said inductors in the opposed legs
of said bridge circuit, a spring means biasing the 40 cells arranged to be equivalently illuminated from
said source, whereby yto induce equivalent elec
pressure responsive member, adjustment means
trical responses from said cells, iìrst control
for varying the tension of the said spring means,
means actuated upon movement of said measur
motor means energized upon the unbalancing of
ing member for varying the ratio of light sup
said bridge circuit for adjusting the said adjust
sition.
ment means so as to vary the tension of the
spring means so as to cause thereby -the move
ment of the said member adjusting the core for
rebalancing the bridge circuit, andan altitude
indicating device actuated by the said motor
means in response to the movement thereof, .
whereby the altitude indicating device is posi
tioned in response to the atmospheric pressure
existing at the point of measurement and the po
sition of said indicating device corrected for the
temperature to which said atmospheric temper
ature responsive resistor is subjected at the time
of measurement and for atmospheric pressure
and temperature conditionsexisting at the start
ing level ofsaid measurement.
„
_
,
f
plied .to said cells in such a manner as to differ
entially aiîect said responses of said cells, motor
means controlling the actuation of said biasing
means, means causing energization of said motor
means in accordance with differential responses of
_ said cells, whereby .to actuate said biasing means
in such a manner as to cause the return of the
measuring member .to the iirst position and sec
ond control means for varying the ratio of light
supplied to said cells so as to cause said motor
means to change 4the return position of the meas
uring member.
l0. An altimeter comprising in combination, a
normally electrically balanced bridge circuit, a
single source of light, a iirst photo-electric cell,
a‘second photo-electric cell, said photo-electric
6. A pressure responsive instrument, compris
60 cells forming adjacent counter balancing arms
ing, in combination, a balanced bridge circuit, a
of said bridge circuit, said cells of the electron
pair of adjustable members for unbalancing said
emissive type arranged to receive iight from said
circuit, a motor means energized upon the'unbal
source, a ilrst apertured control slide for regu
ancing of said circuit, an atmospheric-pressure
lating the intensity of the light supplied to the
condition responsive means operatively connected
ñrst cell from said source. a second apertured con
to one of said members and a ltemperature condi
trol slide for regulating the intensity of the light
tion responsive means operatively connected .to
supplied to the second cell from said source, said
the other of said members, both said condition re
control slides thereby regulating the electron
sponsive means jointly controlling Ithe unbal
emissions from said cells and thus the balance of
ancing of said circuit, indicator means actuated
said bridge circuit, an aneroid for movably actu
by said motor means upon the unbalancing of
ating said ilrst slide upon a change in atmospheric
said circuit, and biasing means actuated by said
pressure, a spring exerting a tension upon said
'motor means for moving at least one of said mem
aneroid, a mechanism controlling the tension of
bers so as to rebalance said circuit.
said spring, an altitude- indicating device, a free
7. An instrument comprising, in combination,
air atmospheric temperature responsive ther
1
,
i
2,412,541
Y
23
mometer bulb of the distant type for movably
actuating the second slide upon a change in tem
perature, and a reversible electronic drive motor
controlled by the unbalanced potential oi said
bridge circuit and mechanically connected to said
. tension control mechanism and said indicating
device, and upon movement of either of said slides
causing the unbalancing of said bridge circuit
energizationof said motor is effected in such a
2t
ment of said measuring member for varying the
ratio of light supplied to said cells in such a man
ner as to differentially aiîect said responses of said
cells, motor means controlling the actuation of
said biasing means, and means causing energize.
tion of said motor means in accordance with dif-V
ferential responses of said cells, whereby to actu
ate said biasing means in such a manner as to
cause the return of the measuring member to the
manner as to adjust said indicating device and 10 first position, said motor means adjusting said in..
dicator means during such return movement of
actuate _said tension control mechanism so as to
said measuring member, and second control
vary the tension of said spring causing the move
means for varying the ratio of light supplied to
ment oi' said aneroid and movement of the ñrst
said cells in such a manner as to cause said motor
sllde'so as to balance the said bridge circuit,
whereby the altitude indicating device is posi
tioned in response to the atmospheric pressure
means' to change said return positionfof the meas
uring member and cause said motor to change the
adjustment of said indicator means.
existing at the point of measurement and the po
14. In an altimeter the combination with a re
sitionl of said indicating device corrected for the
silient diaphragm movable from a i'lrst position in
temperature to which said temperature respon
sive device is subjected at the timeof measure 20 response to'a change in atmospheric pressure act- '
ment.
`
ing thereon; of a tension _spring acting upon said
diaphragm,`a source of light, a plurality of photo
l1. An instrument comprising in combination:
an atmospheric pressure responsive member mov
electric cells arranged to be equivalently illumi
nated from said source, whereby to induce equiv
able from a ñrst position under the influence of
the forces to be measured; a counter-biasing 25 alent electrical responses from said cells, an indi
means acting upon said member; a normally bal
eating device, a ñrst control device actuated upon
movement oí-said diaphragm for varying the in
anced electrical bridge circuit; means associating
tensity of thelight supplied to said cells in such
said member with said bridge circuit, whereby
, movement of said member from said ñrst position
-a manner as> to differentially ail‘ect the electrical '
añects the balance of said bridge circuit; a reset -30 responses of said cells,- a motor controlling the
force exerted by said tension spring, and means
ting mechanism operatively associated with'sai'd
bridge circuit for actuation upon unbalance ofv
causing energization of said motor means in ac_
said bridge> circuit to vary the force -exerted by- «
cordance with differential responses of said cells, `
said counter-biasing means for _returning said
whereby to actuate said spring to cause the re- `
member to said first positionçindicator means -
turn of the diaphragm to the ñrst position, and
said motor adjusting said indicating-device dur
ing such return movement of said diaphragm, a
second control device for varying the intensity of
the light supplied to said cells so as to diii‘eren
tially aiîect the electrical Vresponses from said
movably positioned by said resetting mechanism;
and manually operable -means for unbalancing Y I
said bridge circuit to bring about actuation of
said resetting mechanism so as to vary the re
.turn position of said member andthereby adjust
the position of sai-d indicator means.
,
`
12. In an altimeter the combination with a re
silient diaphragm movable from a ñrst position in
response to a change in >atmospheric pressure act
ing thereon, 'of atension spring acting upon said
diaphragm, a source of light, a plurality of photo
electric cells arranged to be equivalently illumi--
cells- in such a manner as to canse said motor to
change said ñrst position of the diaphragm and
' cause said motor to change the adjustment of
'. said indicating device, and a free air atmos
pheric temperature responsive device for actuat
ing the second control device.
l5. An altimeter comprising .in combination:
movable means -"-whose position is related to at
’nated from said source whereby to induce equiv
mospheric pressure; movable means whose posi
alent electrical responses from said cells, a iirst
.control device actuated upon movement of said 50 tion is related to altitude indications on a .ñxed
scale; adjustable' means -operatively connecting -‘
diaphragm forvarying the intensity of the light
said first named movable means and said second ‘
supplied to said cells in such a manner‘as to dii
named movable means, whereby movement of said
ferentially affect the electrical «responses of said
cells, `a motor controlling the force exerted byÀ
ñrst named lmovable means may cause movement
of said second named movable means, said ad
said tension spring, and means causing energiza
justable means comprising means for varying the
tion of said motor means in accordance with dif
ratio between movements of said connecting
ferential responses of said cells, whereby to actu
Ä means and of said second named movable means,
ate said spring to cause the return of the dia
said ratio varying means comprising ñrst manu
phragm to the iirst position, a second control de
vice for varying the intensity of the light supplied 60 ally operable control méanseffective to alter the
rate of change of said altitude indications withto said cells so as to diñ`erentially affect‘the elec-"
changes in atmospheric pressure, and a second
trical responses from said cells in such a manner
manually operable control~ means eñective to al
as to cause said motor to change said ñrst posi
ter the rate of change of said altitude indications
tion of the diaphragm, and a free air atmospheric
temperature responsive device for actuating the ,
with changes in atmospheric temperature; iirst
second control device.
calibrated means whereby actuation of said ñrst‘
i
I
.
118. An instrument, comprising in combination,
a measuring member movable from a ñrst posi
tion under influence of the forces to be measured,
an additional biasing means acting upon the
measuring member, a plurality of photoelectric
cells arranged to be equivalently illuminated from
said source, whereby to induce equivalent elec
trical responses from said cells, an indicator
means, first control means actuated upon move
control means may be interpreted in terms of
deviation of actual atmospheric pressure at a
reference level from a standardyand second cali
brated means whereby actuation of said second
control means may be interpreted in terms of the
difference between the temperature ambient to
said ñrst named movable means andthe temper
ature at said reference level.
i
PAUL F. SHIVERS.
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