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Jan. 4, 1949.
o. c. HILL ETAL
2,458,164
emvnommrm
Filed Oct. 25, 1943
2 Sheets-Sheet 1
10
15
.glwsntou
‘Jan. 4, 1949.
D. C. HlLL- EI'AL
2,458, 1 64
GRAVI TOMETER
Filed Oct. 25, ‘1943
2 Sheets-Sheet 2
PatentedJanf4, 1.949
2,458,164
UNITED STATES PATENT OFFICE
GRAVITOMETER
Donald 0. Hill, Los Angeles, and William A. I
McGlashen, Huntington Park, Calif.
Application October 25, 1943, Serial No. 507,500
11 Claims. (01. 73-24)
This invention relates to gravitometers, and,
As heretofore set forth, the principle upon
which this invention is based is that the frequency
more particularly to a method and means of de
termining the density of a gas or gases. The
principle upon which this invention is based is
that the frequency or pitch of the sound wave pro
duced by a whistle of ?xed length depends on the
density of the gas used in producing the sound
wave; the lower the density of the gas, the higher
the frequency or pitch. Therefore, in‘ accord
or pitch of a sound wave produced by a whistle of
?xed length depends upon the density of the gas
used. We utilize this principle by passing a gas
through a whistle to produce a sound wave and by
varying the effective length of the whistle to pro
duce a sound wave of predetermined frequency.
We determine when this predetermined frequency
ance with this invention, we make use of this 10 of sound wave is reached by actually comparing
the sound produced with the resonance of a single
stituting a single element or mixture of elements
frequency indicator. By utilizing this principle
by passing the gas through a whistle which is
it is evident that the density of the gas is a func
adjustable so that the length of the whistle may
tion of the length of the whistle taking into con
be varied to produce a predetermined frequency 15 sideration the pressure. temperature and ratio of
of sound wave, the reproduction of which is indi
the speci?c heats of the gas used. It therefore
principle in determining the density of gas con
cated by a resonance or single frequency indicator.
It is therefore an object of this invention to
provide a device for determining the density of
. a gas or gases which employs the foregoing prin
ciples.
follows that the frequency of the sound wave pro
duced by changing the whistle length gives a
measurement as to the length of whistle which is
20 a function of the speci?c gravity, temperature,
pressure and ratio of speci?c heats of the gas.
Another object of this invention is to provide a
method for determining the‘ density of a' gas by
passing the gas through a whistle to produce a
sound wave, varying the length of the whistle
Therefore, knowing the temperature, pressure
and ratio of speci?c heats of a. particular gas, and
having determined through the use of our method ‘
until the same may be brought to a predetermined '
frequency of sound wave, and determining the
speci?c gravity of the gas from the effective length
of the whistle required to produce the said fre
quency of sound wave.
.
Another object of this invention is to provide a
method of determining the density of a, gas by
the use of a single whistle of variable length oper
ative to produce a sound wave of de?nite ‘fre
the effective length of the whistle to produce a
given frequency of sound wave, an equation can
be written which gives the speci?c gravity of the
gas or a density in terms of these values.
In accordance with actual practice, the op
30 erating equation thus determined is used to con
struct operating curve sheets similar to Figure
6 for the determination of speci?c gravity of
gases from measured whistle lengths and observed
gas temperatures when the whistle is sounded at a
quency or pitch as indicated by' a resonance or 35 given frequency of sound wave. A simpli?ed gen
single frequency indicator.
Other objects and advantages of this inven
eral equation for determining the e?ective length
ing drawings.
tureTis:
of the whistle in inches as a function of speci?c
tion it is believed will be apparent from the
gravity of the gas S, the temperature T of the
following detailed description of a preferred em
gas at the whistle in °F., and where K is the ratio
bodiment thereof as illustrated in the accompany 40 of the ‘speci?c heats of the gas at the tempera
In the drawings:
Figure 1 is a top plan view of the gravitometer
embodying our invention.
‘
Figure 2 is a side elevation thereof.
Figure 3 is an enlarged fragmental sectional
elevation of the variable length whistle embodied
-,
'
S_aK(460+
T)
"
52012
45 where Z is the effective length of the whistle in
inches.
'
_ The speci?c gravity of the gas is as compared
with air of a specific gravity of .1. In this formula
'
a is a constant, depending on gas pressure, whistle
Figure 4 is a wiring diagram of the resonance
construction and desired constant frequency.
or single frequency indicator.
50
In order to fully understand the method of
Figure 5 is a front elevation of the gravitometer
our
invention and the apparatus used for carry
embodying our invention.
‘
v
ing out the method, it is believed advisable to
Figure 6 is a diagram of whistle lengths as re
?rst describe the preferred form of apparatus as
lated to speci?c gravity of a methane-ethane gas
it is illustrated in the accompanying drawings.
mixture of varying range of temperatures.
55
In the drawings I indicates a whistle barrel
in our invention.
‘ 9,468,164
which is provided with a whistle aperture II. The
whistle barrel is supported in a supporting sleeve
2 which is secured to a supporting tube 3. The
whistle barrel I extends through a reduced cylin
drical portion of the sleeve 2 and is clamped in
position of adjusted length by means of a tube
clamp 4. This enables preliminary adjustment of
l
4
.
.
of the test, needle valve I5 is closed so that the
pressure within the whistle I is atmospheric pres- '
sure. The vertical lift water column I6 is then
adjusted‘ to bring the water in the gauge glass
I9 to the correct zero» pressure position, after
which and during the entire period of test, the
correct pressure and flow of gas from the sample
supply is maintained by adjusting needle valve
I5 so that the water meniscus coincides at all .
standard conditions of operation.
In order to determine the effective length of ll times during the test with the operating mark
2| on the glass tube I9. ' With conditions main'-- ,
the whistle’barrel I, there is mounted therein a
tained as stated above, the\eifective length of
plunger 6 which plunger or piston 6 determines .
the whistle I is varied by turning ‘micrometer
the effective length of the barrel by its position
thimble 9 to move pistonli toward or away from
axially oi the barrel I. In order to determine this
position with the degree .of accuracy required. . whistle aperture I'- to increase or decrease the
ective length of whistle I to that length nec
the plunger Ii has formed thereon a micrometer
essary for the whistle I to produce a sound, wave
screw ‘I which is threaded through the microm
having a _frequency identical to that of resonator
eter barrel 8 and has secured to its outer and
20 as indicated by maximum electric ?ow through
a micrometer thimble 9. The micrometer thim
ammeter M.
ble 9 has graduations 9”- formed thereon, while
The gas temperature, as indicated by thermom
corresponding graduations 9b are formed .on the
eter I3, and the effective length of the whistle I,
outer surface of the barrel 8. It will be observed
as indicated by the micrometer reading, are then
that the sleeve 3 ?ts over the supporting tube 53
used to determine the speci?c gravity of the '
and forms a sliding ?t therewith. A lock screw
5 is provided for locking this adjustment and pro- _ gas sample from a curve ‘sheet similar to Figure
vides a calibrating lock for locking the parts in
6 constructed
The resulting
for.error
the type
fromofthe
gasuse
being‘testedm'
of incorrect
the required adjusted position upon calibration
gas
pressure
is
about
1%
of
the
speci?c
gravity
of the whistle.
of, the gas for each one-quarter inch of water
The whistle barrel I is connected through a
conduit l0 with a cylinder II in which there is 30 pressure variation from the standard operating
gauge pressure for the‘ surrounding temperature.
provided a thermometer reservoir I2 in which the
The error is positive for pressure less than, and
thermometer I3 is positioned for taking thev tem
negative for pressures greater than, the standard
perature of the gas. ‘The thermometer well I2 is
the length of the whistle barrel to determine
connected to a. gas inlet tube I4 in which a gas '
inlet valve I5 is mounted. Means are provided 35
for controlling and adjusting the pressure of the
gas which is used to actuate the whistle. This
pressure adjusting means may be of any suitable
or desirable construction and is herein illus
trated as being of the following construction: A
Water column I6 is carried by parallel links I1
enabling adjustment of the height of the water
operating gauge pressure.
_.
Standard operating gauge pressure is variable
depending on surrounding‘ temperture. The,
standard reference gauge pressure used to call
brate the instrument is 2% inches of water for a
surrounding temperature of '60" F. _
1 -
Since the physical characteristics ofthe reson
ator 28 and other metal parts of the instrument
change slightly with surrounding temperature, it _
column. This water column is connected by means
provide
is necessary,
a means
if extreme
by which
accuracy
the combined
is required,
effects,
to
'
of a rubber hose I8 to a glass tube III which glass
of
these
changes
on
the
accuracy
of
the
instru
45
tube is mounted on the face panel 20 of the in
.ment can be eliminated. This is accomplished by
strument and is marked as indicated at 2|. This
?tting the vertical section of the gauge. glass I9
point 2I is the point to which the water meniscus
with a scale 29 graduated toindicate' zero waterv
is adjusted when tests are being conducted. Gas
pressure positions for surrounding air tempera- ,
pressure is transmitted from the cylinder II to
tures from 30° to 100° F. In other words, gradua-=
the surface of the water within the water column
tions on this scale have been empiricallydeter- ,
I6 through a ?exible hose coupling 22. The gas
mined so that the operating pressure can be
pressure is thus taken at the gas inlet to the
changed the amount necessary to oifset any error
whistle. Any pressure change in system is indi
cated by the change of height of water in the
glass gauge I9 on th front of the panel.
The adjustable veztical lift provided by the
parallel links I‘! operating through the adjust
in the indicated speci?c gravity caused by changes
in the instrument due to changes in surrounding
temperature. _
The resonator 28 is constructed of seamless
brass tubing and one end is completely closed. It
ment handle 23 enables the height of the water
is supported at the closed end by a bracket 30 to
column to be moved to the zero pressure position
in the gauge glass during calibration and for the 60 which it is attached by use of a rubber insulator
which prevents metal to metal contact between
reproduction of an exact zero pressure setting
during subsequent operation of the instrument.
the bracket 30 and the resonator .28. The bracket
30 is so dimensioned and attached to the base of
The handle 23 is carried by a screw 24 which is
the instrument that it supports the resonator 28
threaded through a block 25 carried by the panel
in such a manner that the resonator is parallel _
20 in position to engage a leg 26 carried by one
to and directly beneath the center line of the
' of the parallel links I‘I.
whistle I. This resonator is free to vibrate and
‘During an actual test, the source of the sample
is set in motion by impulses imparted to it by the
of‘gas to be tested is connected by a suitable con
whistle I. The resonator has a natural or de?
duit to conduit connector I5a from which the gas
stream passes through the needle valve I5, hence 70 nite frequency of vibration. When the sound vi
brations set up by the whistle I‘ are adjusted to
through another conduit and conduit connector
the natural frequency of the. resonator 28, a
It to the supported conduit 21, thermometer res
large amplitude of vibration is produced in the
ervoir I2, cylinder II and conduit I0, through
resonator and this vibration in‘ turn is used to
which the gas stream enters the whistle I.
As a preliminary adjustment at the beginning 75 generate an electric current which in turn is by
2,458,164
5 .
proper ampli?cation made to actuate an indicat
ing ammeter 3| during the time the frequency of
sound wave produced by the whistle and that of
the resonator is identical. Accordingly, the constant frequency resonator 28 is operatlvely com.
nected to a generator '32 which in-turn is con
nected with an amplifying unit 33 which may be
'
provided that the amount ‘of electrical energy
produced _is such as to actuate the ammet'er
through a range su?icient ‘to determine when
the maximum current is being generated. _ The
accuracy of determination for low current values
depends upon the degree of ampli?cation only.
As an illustrative example of the use of our
of any suitable or desirable design or character.
invention, the following is set forth: The in
The amplifying unit is in turn connected with - strument was ?rst calibrated and determination
the ammeter 3 l. The generation of current from lo of the constants a and c were then made as
the constant frequency resonator is effected by
causing the metallic plate of the generator to
move in the magnetic ?eld generating alternat
ing current. The ampli?er, therefore, should in
clude, in addition to the ampli?er tubes, a trans
In order to determine the values for the
modified equation
former and a recti?er, all as is well understood in
the art, to produce a current for the actuation of
the sensitf"e ammeter 3|.
in‘which modi?ed formula the expression m+c=l
As will be apparent from the drawing, Figure 6,
the constant frequency resonator 28 has a fre
quency of _ 1147 oscillations, per second.
This
particular frequency was chosen as being a fre
quency which lies within the range of the maxi
mum deviation of the curves of the plotting of
the vibrations per second against the length of
the whistle as such ‘curves are plotted in Figure 1
of the article which appeared in the periodical
“Gas,” issue February 1939, pages 17, 18 and 58.
Any other appropriate frequency which lies with
in this region of the maximum deviation in the
follows:
'
‘ * 520(m+c)=*‘
in which m is the micrometer reading of the
length and c is a constant.
In calibrating the instrument, the zero pres
20 sure adjustment for surrounding temperature
was made, after which the whistle was sounded
at the correct gas pressure with the reference gas
having a known speci?c gravity of, for example,
0.555. The temperature of the gas at the whistle
was found to be 80° F. The micrometer was then
adjusted to read 0.870 inch. This approximate
micrometer setting was chosen to allow for maxi
mum micrometer range for testing gases of high
speci?c gravity and at higher gas temperature.
The calibration lock 5 was then released and the
whistle barrel I was moved over the piston 8 until
the ammeter 3| indicated maximum electrical
which has a vibration frequency lying outside of
current flow, at which point the whistle barrel I
this range of the break of the curve, that there
will be substantially no accurately measurable 35 was locked securely in position at the lock 5, and
the ?nal adjustment made by micrometer adjust_
difference in whistle length for such ranges of
ment of the position of the piston 6. This re
vibration. From the said Figure 1 it will be
sulted in a correct micrometer reading of 0.871
noted that at both ends of the curve the curves
inch for av natural gas having a speci?c gravity
approach parallelism with the ordinate.
_
The method of our invention therefore in 40 (S) of 0.555 and a test temperature of 80° F. By
reference to a table of speci?c heat of gases, the
volves the dtermination of the density of a gas
value of K was determined to be 1.3049 at 80° F.
by passing the gas under ‘ constant pressure
In order to complete the data necessary for the
through the whistle I and of varying the effective.
determination of the constants a and a, another
length of the whistle until the sound wave is
value of micrometer reading was determined by
of a frequency corresponding with, or equal to,
micrometer adjustment only while the whistle
the natural frequency of the resonator 28. A
was being sounded at the correct pressure by a
large amplitude of vibration is produced in the
natural gas having a speci?c gravity of 0.660 and
resonator 28 and the ammeter 3| will indicate
at a test temperature of 80° F. under which con
maximum current ?ow and any further change,
.001" or .002" in effective length of the whistle 50 ditions the ammeter indicated maximum current
flow when the micrometer reading (m) was 0.505
will result in noticeable decrease in amount of
inch. By reference to the table of specific heats,
electrical energy produced. No current will be
the value of K,.the ratio of the speci?c heats in
generated until the length of the whistle has
said curves might be chosen. It will be apparent
from these curves that if a resonator is chosen
been adjusted to within a few thousandths of an
inch of effective length necessary to produce the
correct frequency of the sound wave, at which
point the ?rst indication of current flow will be
observed, and as the whistle length is brought
‘closer to the correct value, the amount of current
generated will increase to reach a maximum only
‘when the length of the whistle is adjusted to
produce the sound wave of the same wave length
as that of the constant frequency resonator 28.
It is an important fact that the accuracy of
the determination utilizing our method does not
depend on the production of a predetermined
amount of electrical energy but only on whether
any further change in the effective length of the
whistle causes an increase or decrease in the
maximum amount of electrical energy that can
be produced under the particular conditions
prevailing during the test. This ‘is important be
cause, under these conditions, any change that
may occur in the emciency of the electrical system
will have no effect on the accuracy of results,
this gas, was given as 1.2690 at 80° F.
The ?nal determination of the constant a was
made by the use of the following formula:
111.
Thus two equations were setup for a constant
0 as follows: ‘
jpsmumm
"-
520><.555
520x .660
By subtracting the latter equation from the
?rst to cancel c and solving the resulting expres
,sion, the value of the constant a was found to be
Using this value of a in the equations above set
forth, c was found to have a value of c=2.9741.
Having determined these constants, the curves
for the speci?c gravity of other gases was deter
mined as is shown in the graph of Figure 6.
9,480,164
duce a maximum current through the vibration
Having fully described our invention, it is 'to
of the‘ said resonator.
be understood that we do not wish to be limited .
’
6. A method of determining the density of a ’
to the details herein set forth, but our invention
is of the full scope of the appended claims
gas, which includes the steps of passing a gas
CR at a predetermined pressure and known tempera-]
We claim:
1. The method of determining the density of
ture through a whistle to produce a sound wave,
imposing the sound wave upon a constant fre
quency resonator to vibrate the same, producing a
current of electricity from the vibrations of the
a gas which comprises passing a gas under pres
sure through a whistle to produce a sound wave,
subjecting a constant frequency resonator to said
sound wave to thereby vibrate said resonator in 10 resonator, and adjusting the length of the whistle
to produce a maximum current whereby the ,den- ,
response to said sound waves, adjusting the
sity of the gas is determined in accordance with
. length of the whistle so that the sound wave of
the equation
'
de?nitelength as compared with the sound wave
_ of said constant ‘frequency resonator is pro
S: aK(460+ T)
duced, determining when the length of the
whistle is of correct length to produce a wave
length corresponding exactly to, that of the con
stant frequency resonator by measuring the in_
tensity of the vibrations of the constant fre- '
quency resonator, and then determining the
density of the gas producing the said vibration
in accordance with the equation
520(1114-6)2
in which m is a measurement of the length of
the whistle in inches, 0 and a are constants, K is
the ratio of speci?c heats of the gas tested, and
T is the temperature of the gas at the whistle
in degrees Fahrenheit.
1
.
'
7. In an apparatus for determining the density
of the.gas,,,,a whistle, means forconducting the
gas through the whistle, a constant frequency
resonator positioned parallel with the whistle in
the range of sound waves emitted from said'
whistle, means for varying the effective length
where m is a measurement of the length of the
whistle so determined, 0 is a constant, a is a con
of the whistle to thereby produce a sound wave
corresponding in wave length to that of the con
30 stant frequency resonator, and means for meas
the whistlein degrees Fahrenheit.
uring the amplitude‘ of vibration set up in the
_ 2. In a method of determining the density of
constant frequency resonator by the sound wave
a gas, the steps of passing a gas through a whistle,
stant, K is the ratio of speci?c heats of the gas
tested, and T is the temperature of the gas at
adjusting the length of the whistle to produce a
sound wave corresponding in wave length to that
of a constant frequency resonator, subjecting
said constant frequency resonator to said sound
wave to thereby vibrate said resonator in re
produced by the whistle to determine when the
whistle length has been adjusted to produce the
sound wave having a wave length corresponding
with that of the constant frequency resonator.
8. In an apparatus for determining the density
sponse to said sound waves, and measuring the ' of a gas, a whistle, means for varying the effec
tive length of the whistle, means for passing a
amplitude of vibrations of the constant frequency
resonator to determine when the whistle length 40 gas through the whistle to produce a sound wave,
a constant frequency resonator positioned paral
is adjusted to produce vibrations corresponding
lel with the whistle to induce vibrations in the
in wave length to that of the constant frequency
resonator, means for producing a current from_
resonator.
the vibrations of the resonator, means for am
3. In a method of determining the density of
a gas from the length of the whistle through 45 plifying the current, and means for measuring
the effective length of the whistle when the maxi
which the gas is passed to produce vibrations,
mum current is being generated from the vibra
- the steps of adjusting the whistle length to pro
tions set up in the constant frequency resonator. v
duce sound vibrations which correspond in wave
. 9. In an apparatus for determining the density
length to those of a constant frequency resonator,
50 of a gas, a whistle, means for varying the effec
tive length of the whistle. means for, passing a
gas through a whistleto produce a sound wave,
rectly adjusted by determining the length of said
a constant frequency resonator, and means op
whistle which produces vibrations of maximum
and as an index of the density of the gas deter
mining when the length of the whistle is cor
intensity in the said constant frequency res-y
cna-tor.
‘
'
,
4. In a method of determining the density of a
gas, the steps of passing a gas through a whistle
to produce a sound wave, impressing the‘ sound
wave upon a constant frequency resonator, ad
eratively associated with the constant frequency
resonator and’ operating in response to the vibra
tions set up therein by the sound waves produced
by the gas passing through the whistle for deter
mining when the whistle is adjusted to produce
a sound wave corresponding in frequency to that
justing the length of the whistle to produce 60 of the constant frequency resonator, and means
sound waves having a frequency equal to the
natural wave length of said resonator, until there
exists a maximum intensity of vibration of the
constant frequency resonator to determine when
for measuring the effective length of the whistle
when so adjusted.
10. In an apparatus for determining the den
sity of a gas, a whistle, means for conducting gas
the whistle length is adjusted to produce a wave 65 under pressure through the whistle, a constant
frequency resonator, means for varying the ‘ef
length corresponding to that of the constant
fective length of the whistle to produce a sound
frequency resonator.
wave to induce a vibration in the resonator, and
5. In a method of determining the density of a
indicating means operative in accordance with
gas, which includes the steps of passing the gasv
the amplitude of vibrations induced in the reso
70
through a whistle to produce a sound vibration,
nator arranged to produce a maximum indica
imposing the sound wave so produced upon a
tion only when the effective length of the whistle
constant frequency resonator to vibrate the same,
is adjusted, with saicLgas ?owing therethrough,
producing an electrical current from the vibra
to emit a frequency of vibration substantially
tion set up in the constant frequency resonator,
equal to the frequency of said resonator.
and adjusting the length of the whistle to pro 78
10 ‘
11. In an apparatus for determining the den
UNITED STATES PA'I'ENTS
‘ sity of a gas, a whistle, means for varying the ef
fective length of the whistle, means for passing
a gas through the whistle to produce a sound
Number
611,028
Name
Date
Brysch _________ __ Sept. 20, 1898
wave, a constant frequency resonator positioned 6
' 838,494
Barlow __________ __ Dec. 11, 1906
in the sound range of the whistle to induce
1,269,599
Harber et a1. ____ .._ June 18, 1918
vibrations in the resonator, means for producing
1,528,586 Tate _____________ __ Mar. 3, 1925
a current from the vibrations of the resonator,
1,570,781
Ruben __________ -_ Jan. 26, 1926
means for amplifying the current, and means
Mikelson _____ _._.-__ May 19, 1942
for measuring the effective length of the whistle 10 2,283,750
when the maximum current is being generated
OTHER REFERENCES
from the vibrations set up in the constant fre
“Use
of
the,
Whistle in the Purging of Gas
quency resonator.
Lines; for Measuring Density and Gas-Air Ratio
DONALD C. HILL.
of Fuel Mixtures," article in Gas magazine, 1"eb._
WILLIAM A. McGLASHEN.
REFERENCES CITED
The following references are of record in the
file, of this patent:
15 1939, PD. 17, 18 and 58.
,
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