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Патент USA US2404894

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July 30, 1946.
w, p_ WILLS
2,404,894
MEASURING APPARATUS
Original Filed Nov. 15, 1938
FIG. 1.
"\46
T 50
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ZNVENTOR.
WALTER P. WILLS .
31/
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Patented July 30, 1946
2,404,894
UNITED STATES PATENT OFFICE
2,404,894
MEASURING APPARATUS
Walter P. Wills, Philadelphia, Pa., assignor to The
Brown Instrument Company, Philadelphia, Pa.,
a corporation of Pennsylvania
Original application November 15, 1938, Serial No.
240,594. ‘Divided and this application Septem
ber 25, 1942, Serial No. 459,638
12 Claims.
(Cl. 172-239)
1
2
A prior application Serial No. 240,594, ?led
November 15, 1938, by Thomas R. Harrison and
myself as joint inventors and issued into Patent
2,300,742 on November 3, 1942, discloses certain
improvements in methods of and apparatus for
preventing hunting in automatic recording and
controlling systems. Said prior application dis
unidirectional potential or current under meas
urement.
When the source of minute unidirectional po
tential or current under measurement is derived
from a thermocouple which is located in a fur
nace, the temperature of which it is desired to
ascertain, additional problems in the measure
closes certain improvements in methods of and
apparatus for the measurement of minute elec
trical currents or potentials and their utilization
for control and analogous purposes which were
ment of the minute unidirectional potential or
current are encountered because of the introduc
tion of extraneous alternating currents into the
measuring circuit from leakage paths in the fur
nace between the thermocouple and ground. By
way of example, when the furnace whose tem
not the joint invention of the applicants who
made said prior application and are my sole in
vention and are disclosed and claimed by me in
the present application, which under the circum
stances is to be regarded as a division of said
prior application.
'
perature under measurement is an electric fur
15 nace which has heating resistance elements dis
\
A general object of the invention is to provide
an improved method of measuring and/or re
cording potential or current variations of minute
posed in its walls, alternating currents frequent
ly flow from the furnace heating elements to
ground through leakage paths in the furnace
walls. The thermocouple extends through the
20 furnace walls and even though it is provided
with a protecting tube some of the alternating
A more speci?c object of the invention is to
or ?uctuating currents which ?ow in the furnace
provide a. method of employing current or po
Wall leakage paths tend to ?ow through the
magnitude.
tential variations of' minute magnitude to con
thermocouple and the measuring circuit to
trol the operation of electro-mechanical appa 25 ground. The thermocouple and measuring cir
ratus.
cuit provide a shunt path for such leakage cur
A still more speci?c object of the invention is
rents to ground since va portion of the apparatus
to provide an improved method of and apparatus
utilized for measuring the potential or current
for eliminating the e?ects of spurious electrical
variations of the thermocouple, generally the
eifects upon the operation of apparatus employed 30 electronic ampli?er is grounded. It is noted that
for measuring the magnitude and changes in
?uctuating currents will also tend to be estab
magnitude of minute electrical currents or po
lished in the thermocouple and measuring circuit
tentials.
due to electrolytic action between the thermo
It is a particular object of the invention to
couple and ground. The alternating or ?uc
provide a method of and apparatus for prevent 35 tuating currents introduced into the thermo
ing the introduction of extraneous alternating
couple and measuring circuit produce inac
currents into the measuring circuit of apparatus
curacies in the measurements obtained and
utilized for making measurements of minute uni
render the operation of the apparatus un
directional currents or potentials in low resistance
stable. More speci?cally, when a potenti
circuits.
ometric measuring arrangement of the self
A serious problem in the measurement of mi
balancing type is employed in conjunction with
nute unidirectional potential or current varia
the thermocouple and electronic ampli?er, such
tions in low resistance circuits, particularly in po
extraneous alternating currents in the thermo
tentiometric measuring circuits wherein the
couple and potentiometer circuit introduce false
source of minute unidirectional potential or cur 45 balance points into- the potentiometer and also
rent is derived from a thermocouple, is the chili
cause erratic operation of the potentiometric re
culty of electrically amplifying such potential or
balancing motive structure.
current variations. The direct ampli?cation of
It is accordingly a primary object of the pres—
minute unidirectional or current variations in
sent invention to provide an improved method
low resistance circuits by means of conventional 50 of and apparatus for measuring minute unidi
electronic amplifying circuits is difficult because
changes in the spacing and relative positions of
the electrodes of the amplifying tubes produce
effects which are similar to and are. of the same
order of magnitude as the. changes inthe. minute. 55
rectional potential or current variations pro
duced by a thermocouple in which the di?iculties
pointed out above have been wholly eliminated
or materially minimized.
This advantageous result is obtainedin accord
2,404,894.
3
ance with the present invention by isolating the
thermocouple from the potentiometric measur
ing network and the associated electronic ampli
fying apparatus. To that end the thermocouple
is periodically connected to the terminals of a
condenser of suitable value which is insulated
from ground, and during alternate intervals the
condenser is disconnected from the thermocouple
and is connected to the input terminals of the
potentiometric measuring network and the asso
ciated electronic ampli?er. By this means any
extraneous alternating or ?uctuating currents
which may exist in any leakage paths from the
thermocouple to ground are prevented from ?ow
ing through the potentiometric measuring net
work and associated electronic ampli?er, and
4
9 adapted to ride on a screw threaded rod Iii
which is rotated in one direction or the other
under control of the thermocouple 3. A suitable
reversible electrical motor H is provided and is
coupled in any convenient manner to the screw
threaded rod ii! to rotate the latter at the de~
sired speed and in the desired direction and there
by to move the contact 8 along the slidewire re
sistance ‘l to rebalance the potentiometer 6 when
the latter is unbalanced.
The terminals of the thermocouple 3 are con
nected by the conductors 13 and 5 to the input
terminals [2 and 13 respectively of a double con
tact interrupter M which is illustrated in Figs.
15 2 and 3. When in one position, the interrupter
it operates to apply the potential developed by
the thermocouple 3 to the terminals of a con
therefore, are rendered incapable of affecting the
denser l5 which is suitably insulated from ground.
operation of the measuring apparatus. Since the
To
this end, the interrupter I4 is provided with a
condenser is insulated from ground, no leakage
movable
pair of contacts l6 and ll which are
20
currents tend to ?ow to the condenser from the
insulated from each other and from contacts l2
furnace leakage paths,
and i3 and are adapted to be moved into engage
The various features of novelty which charac
ment with the contacts 52 and 113, respectively,
terize my invention are pointed out with par
when the interrupter i4 is in said one position.
ticularity in the claims annexed to and forming
a part of this speci?cation. For a better under 25 When the interrupter is in its other position the
movable contacts l6 and H are in engagement
standing of the invention, however, its advan
with
a pair of insulated contacts l8 and !9, respec
tages and speci?c objects obtained with its use,
tively, and in this position of the interrupter the
reference should be had to the accompanying
potential which was impressed on the condenser
drawing and descriptive matter in which I have
l5 by the thermocouple 3 is connected in opposi
illustrated and described a preferred embodiment
tion to the potentiometric potential between the
of the invention.
left end terminal of the slidewire resistance 1
Of the drawing:
and the contact 3. It should be noted that in the
’ Fig. l is a diagrammatic representation of the
last mentioned position of the interrupter M the
use of the invention in a potentiometric record
" thermocouple 3 is totally disconnected from the
ing and controlling system;
Figs. 2 and 3 illustrate in detail a form of
interrupter that may be employed in the arrange
ment of Fig. 1; and
Fig. 4 illustrates schematically a form of elec
remainder of the measuring apparatus, and there
fore, is eii‘ectively isolated from the remainder of
the apparatus. In this manner the introduction
of any extraneous ?uctuating or alternating cur—
tronic ampli?er that may be employed in the 40 rents in the thermocouple circuit due to leakage
paths which may be established between the
thermocouple and ground through the walls of
the furnace due to electrolytic action between
drawing, there is illustrated in schematic form
the thermocouple and ground is eifectively pre
an arrangement including an electronic device l
shown in detail in Fig. 4 for producing effects 45 vented from affecting the operation of the meas
uring apparatus. In addition, since the con
in accordance with the extent of unbalance of a
denser !5 is insulated from ground, n0 extraneous
potentiometric measuring network which controls
?uctuating or alternating currents will flow to
the electronic device and is unbalanced in acthe condenser from leakage paths between the
cordance with the variations in a quantity to be
thermocouple and ground.
.
50
measured and in which because of the small mag
The form of interrupter l4 shown in Figs. 2
nitude of the unbalance electromotive forces, it
and 3 includes a continuously rotating shaft 28
is not practical nor desirable to have the said
which
may be driven by any suitable form of motor
effects produced directly by the potentiometric
such as a synchronous electric motor 2! which
measuring network.
More speci?cally, an arrangement is illustrated 55 receives energizing current from supply conduc
tors not shown and on which shaft are insulat
in Fig. l for recording and controlling the tem
ingly mounted two pairs of slip rings 22, 23 and
perature of a furnace 2 in the interior of which a
24, 25 and a four segment commutator 26 each
thermocouple 3 is arranged in heat transfer rela
segment being of the same arcuate length and
tion therewith and is responsive to slight changes
in furnace temperature. The thermocouple 60 all insulated from each other. Brushes l6 and I‘!
are provided for the commutator 2'5 and corre
which may be located at a distance from the re
sponding brushes l2, l3, l8 and 19 are provided
mainder of the measuring apparatus has its ter
for the slip rings 22, 23, 24 and '25, respectively.
minals connected by a pair of conductors ll and 3
Brushes l6 and H are connected to opposite ter~
to the terminals of a null point potentiometric ‘
minals of the condenser 15 while the brushes [2
measuring network 5. The potentiometric meas 85 and i3 are connected to conductors 4 and 5,
uring network 5 includes a slidewire resistance '7
respectively, and the brushes l8 and is are con
and an associated contact 8 which is capable of
nected to one end terminal of the slidewire re
being moved along the length of the slidewire and
sistance l and to contact 8, respectively. One
may be of any suitable type for example such as
opposite pair of segments On the commutator 25
the Brown potentiometric measuring network
are connected to the slip rings 22 and 23 and the
disclosed in Patent 1,898,124 issued to Thomas R,
other opposite pair of segments are connected to
Harrison on February 21, 1933.
the slip rings 24 and 25. Thus, during each cycle
The movable contact 8 of the potentiometer
of rotation of the shaft 20, one pair of segments
is attached to a suitable carrier which for example
may be in the form of an internally threaded nut 7,5 on the commutator will be in engagement with
Fig. 1 arrangement.
> Referring more particularly to Fig. 1 of the
2,404,894
the brushes [6 and I1 for one half cycle and dur
ing'that time will close the circuit from the ther
mocouple leads 4 and 5 to the condenser l5. Dur
ing the remaining half cycle the other pair of
commutatorsegments will be in engagement with
the‘ said brushes to connect the potentiometer
slidewire resistance ‘I in circuit with the condenser 15. The speed of the motor 21 which drives
‘6
be a strip chart as shown and is adapted to be
driven in any convenient manner as for example
/ by'a undirectional motor 33 through suitable gear
ing (not shown), so that a record of the tempera
ture to which the thermocouple v3 is subjected will
be recorded as a continuous line on the chart.
The electronic ampli?er i as noted hereinbefore
is illustrated in detail in Fig. 4 and as shown in
the shaft 29- is so adjusted that the time for one
cludes an electronic valve 34 which is preferably
cycle of rotation of the shaft is identical with the 10 a heater type high mu triode having an anode,
time of one cycle of the alternating current sup
cathode and a control electrode and having its
plied by the conductors L1 and L2 in Fig. 1. The
input circuit connected by conductors 35 and 36
reason for so relating the speed of rotation of the
to the terminals of the resistance 2?. Anode volt
motor 2! and the time of one cycle of the alter
age is supplied the valve 34 from the terminals of
natin-g‘current supplied by lines L1 and L2 is made 15 a suitable ?lter 3'! which is connected in circuit
apparent hereinafter.
between the valve 34 and a. recti?er 38. The rec
The periodic connection of the potential pro
ti?er 38 is a conventional full wave recti?er em
duced on the condenser H3 in opposition to the
ploying a recti?er valve 39 including two heater
potential tapped on the potentiometer slidewire
type diodes in one envelope. Energizing current
resistance 1 produces a pulsating drop‘ across a 20 is supplied the heater ?laments of the diodes from
resistance 2‘! connected in the potentiometer cir
the low voltage secondary winding 40 of a trans
cuit, which potential drop is either in phase with
former (‘it which also includes a line voltage pri
the voltage of the supply lines L1 and L2 or is
mary winding 42, a high voltage secondary wind
displaced 180° in phase therefrom. This pulsat
ing 43 and an additional low voltage secondary
ing potential drop is impressed on the input ter 25 Winding 44. The line voltage primary winding
minals of the ampli?er I wherein it is ampli?ed
:22 is connected to the alternating current supply
and the ampli?ed quantity is applied to the ter
lines L1 and L2. The anode of the one diode of
minals of one winding '28 or 29 01" the reversible
valve 35 is connected to one terminal of the wind
‘ electrical motor H which as illustrated in detail
ing- 43 and the anode of the second diode is con
in Fig. 4 also includes a winding 39 which is con 30 nected to the other terminal of the winding 43.
nected to the alternating current supply lines L1
The cathodes of the diodes are connected together
and L2 through a suitable condenser 3|,
and through a resistance 45 to the positive ter
The reversible electrical motor H is of the in
minal of the ?lter 31 and the negative terminal
duction variety and includes a squirrel cage. rotor
of the latter is connected to a center-tap on the
and two pairs of oppositely disposed ?eld poles 35 winding 43 and to a center-tap on the winding 4%).
on which the windings 28, 29 and 39 are wound.
The negative terminal of the ?lter is desirably
Winding 28 is wound on one ?eld pole of one of
connected to ground potential as shown.
said pairs and winding 29 is wound on the other
The ?lter 3‘! includes a condenser 46 which
?eld pole of that pair. Winding 3B is wound on
shunts its positive and negative terminals and
the other pair of ?eld poles and due to the ac 40 has its positive terminal connected to the anode
tion of condenser 3| the current which flows
of valve 34 through resistances 41, 48 and 49, and
through the winding 39 will lead the line voltage
has its negative terminal connected directly to the
by approximately 90°. The current supplied the
cathode of said valve. As illustrated, the point of
winding 28 by the ampli?er l is in phase with the
engagement of resistances 4i’ and 48 is connected
supply line voltage and establishes a ?eld in the 45 by a condenser 50 to the negative terminal of the
rotor which is displaced 90° in the forward direc
?lter and the point of engagement of resistances
tion with respect to that established therein by
48 and 49 is connected by a condenser 5| thereto.
the winding 30. Similarly, the current supplied
Energizing current is supplied the heater ?la
winding 28 by ampli?er l is in phase with the
ment of valve 34 from the low voltage transformer
supply line voltage, but since the winding 29 is 50 secondary winding 44 which also supplies energiz
wound on an opposite ?eld pole from that on
ing current to the heater ?laments of a twin type
which the winding 28 is wound, winding 29 estab
electronic valve 52. The flow ofv current through
lishes a ?eld in the rotor which lags by 90° that
valve 34 is normally maintained at a mean value
established by winding 3|]. Reaction between the
since the resistance 21 is connected directly across
?eld set up by winding 28 or 29 with that set up 55 the input circuit thereof, but when a pulsating '
by winding 30 establishes a rotating ?eld in the
potential appears across the terminals of resist
rotor which rotates in one direction or the other
ance 21, the conductivity of valve 34 is alternately
dependent upon whether winding 28 or 29 is ener
increased and decreased resulting in a pulsating
gized and thus on the direction of potentiom
potential drop appearing across the resistance 49
etric unbalance. The motor rotor is connected 60 in the output circuit of the valve 34.
through suitable gearing or couplings to the screw
The output circuit of valve 34 is resistance ca
threaded shaft [9 so that the contact 8 is.ad—
pacity coupled to the input circuit of valve 52
justed along the slidewire resistance 1 in accord
through a condenser 53 and a resistance 54 con
ance with the direction of rotation of the rotor.
nected across the input circuit of valve 52. Valve
The direction and duration of rotation of the ro 65 52 is a heater type valve including two triodes in
tor is controlled by the direction and extent of
one envelope. Each triode includes anode, cath
unbalance of the potentiometer so that on motor
ode and control electrode elements. For conven
rotation, the contact 8 is adjusted in the proper
ience, the triode having the resistance 54 con
direction to reduce the potentiometer unbalance.
nected ‘across its input circuit will be referred to
If desired, a pen may be mounted on the car
riage 9 which carries the potentiometer contact 8
as the triode A and the second triode will be re
ferred to as the triode B.
and arranged in cooperative relation with a re
Anode voltage is supplied the triodes A and
corder chart 32 to thereby provide a continuous
B from the terminals of the ?lter 31, and as
record of the temperature of the furnace in which
shown, the anode of triode A is connected
the thermocouple 3 is inserted. The‘ chart 32' may 75 through a resistance 55 to the point of engage
2,404,894
ing 56 of a transformer 5‘I to the
minal of the ?lter. The cathodes
and B are connected together and
tive terminal of the ?lter.
The output circuit of triode A
capacity coupled by a condenser 58
ance 59’ to the input circuit of the
condenser I5 and resistance 65 in eliminating
overshooting and consequent hunting of the po
tentiometric system is described in detail in the
positive ter
of triodes A
to the nega
prior application, Serial No. 240,594 ?led by
Thomas R. Harrison and myself and referred to
hereinbefore and therefore will only be brie?y
described herein.
With the resistance 55 and condenser I5 ar
ranged as shown, it will be apparent that when
is resistance
and a resist
triode B and
the output circuit of the latter is coupled by
transformer 51 to the input circuit of a pair of
electronic valves 59 and 65 which are connected
in push-pull. The transformer 51 includes a
center tapped secondary winding 5|, the termi
nals of which are connected to a respective con
8
The operation or this arrangement including
ment Of resistances 41 and 48, and the anode of
trio-de B is connected through the primary wind
the interrupter contacts I5 and I? are in en
gagement with the contacts I? and I3, the ther
mocouple 3 operates to charge the condenser I5
through the resistance 55 and the electromotive
15 force thus developed between the condenser ter
trol electrode of the valves 59 and 60 and the
center tap of which is connected through a bias
ing resistance 62 to the cathodes of the valves,
which, as shown, are connected together. As
illustrated, a condenser 63 may desirably be con 20
nected across the terminals of the transformer
minals is thereafter compared with the poten
tiometer electromotive force at the then position
of the contact 8 along the slidewire resistance 1
when the interrupter contacts I6 and H are
moved into engagement with the contacts I8 and
I9, respectively.
With the temperature of the furnace to which
secondary winding 5| for tuning the latter to
the thermocouple is responsive at a predeter
the frequency it is desired to amplify. Valves 59
mined value, the condenser I5 will tend to be
and 60 are heater type tetrodes and include
anode, cathode, heater ?lament, control elec 25 charged through the resistance 65 until the con
denser electromotive force is equal to that of the
trode, and screen grid elements. The heater ?l
thermocouple. The contact 8 would then be in
aments of the valves 59 and 59 are energized from
a position along the slidewire resistance ‘I such
the Winding 44.
that the electromotive force tapped off the slide
Anode voltage may be supplied the valves 59
and 60 directly from the supply conductors L1 30 wire ‘I is exactly equal and opposite to the con
denser electromotive force. For convenience,
and L2, as shown, or may be supplied thereto
when the slidewire electromotive force is referred
from a suitable transformer energized by the sup
to hereinafter, that portion tapped off resist
ply line current, if desired. Winding 28 of mo
ance ‘I and opposed to the condenser electromo
tor II is connected in the anode circuit of valve
59 and winding 29 of the motor is connected in 35 tive force is the electromotive force intended.
On a change in the temperature of the furnace,
the anode circuit of valve 60.
for example on an increase in temperature, the
In operation, when a pulsating potential drop
thermal electromotive force will increase the
is produced across resistance Z‘I as a result of
potentiometer unbalance, the resulting ampli?ed
electromotive force developed across the con
an alternating voltage across the terminals of
duce a potential drop across the latter, and as
appears across the terminals of the transformer
til the current through resistance 65 is reduced
to zero or in other words until the system is again
balanced. Thus, until the slidewire electromo
tive force is adjusted to the new value of the
pulsating current flows through the transformer 40 denser terminals. The ?ow of charging current
to the condenser through resistance 65 will pro
primary winding 55 will cause the induction of
a result, the electromotive force developed across
the transformer secondary winding 6| Which
the condenser terminals will not assume the ?
voltage is impressed on the input circuit of
valves 59 and 68. The alternating voltage which 45 nal value of the thermal electromotive force un
secondary winding 6| swings the potentials of
the control electrodes of the valves 59 and 50 in
opposite phase at a frequency corresponding to
the supply line frequency and thereby renders 50 thermocouple electromotive force, the condenser
electromotive force will tend to assume a value
one valve or the other non-conductive depending
intermediate the thermocouple and slidewire
upon the phase of the voltage of the transfermer
electromotive forces.
The flow of current
secondary winding 6| with respect to the supply
through resistance 2‘! on unbalance of the con
line voltage. The resulting deenergization of one
motor winding 28 Or 29 and the increased ener 55 denser and potentiometer electromotive forces
will operate substantially immediately to pro
duce energization of motor II for rotation to ef
gization of the other operates to produce rota
tion of the motor in one direction or the other
fect adjustment of the contact 8 in the proper
direction to reduce the unbalance between the
depending upon the phase of the pulsating po
tential drop produced across resistance Z‘I and
thereby the direction of potentiometer unbal
ance. As illustrated, a condenser 64 may be de
sirably connected between the anodes of valves
59 and 69 to increase the available torque of
the motor I I.
60
condenser
and
potentiometer
electromotive
forces.
It is noted that there is no delaying means in
the circuit through which the condenser and
slidewire electromotive forces are opposed so
In order that the speed of the motor I I may be 65 that the ampli?er I responds substantially im
mediately to unbalance in said electromotive
as great as possible without overshooting of the
forces to energize the motor II for rotation in
new balance point of the potentiometric network
one direction or the other to adjust the slide
6 and consequent hunting taking place, means
wire electromotive force as required to reduce
have been provided to insure that the motor
the unbalance and reduce the motor energization
speed is reduced to zero as the balance point is
to zero at the instant the balance between said
reached. This end is obtained by the arrange
electromotive force is restored. Due to the in
ment including the condenser I5 and a resistance
ertia of the motor, however, the speed of the
65 which is inserted in the conductor 5 leading
latter will not fall off as quickly as the energiza
from the interrupter contact I3 to the thermo
75 tion thereof and consequently, the slidewise elec
couple 3, as shown.
2,404,894
tromotive force will tend to overshoot the value
of the condenser electromotive force.
As a re
sult, the potentiometric network will be momen
tarily unbalanced in the opposite direction,
vice to charge the latter, opposing the E. M. F.
on said device to a known E. M. F. during each
interval when said ?rst mentioned E. M. F. is not
impressed on said device whereby the resultant
which unbalance will produce an effect energiz b of said opposed E. M. F.’s creates a- current of a
ing the motor for rotation in the reverse direction
regular frequency which can be readily ampli
to thereby quickly decelerate the latter. Inas
?ed, amplifying said current, and applying said
much as the condenser electromotive force differs
ampli?ed current to effect a balance between said
from the thermocouple electromotive force by an
amount equal to the potential drop produced
across resistance 65 by the ?ow of current there
through, the contact 8 will not have reached the
position along slidewire resistance 1 correspond»
ing to the new value of thermocouple electromo
tive force at the instant when the condenser and
slidewire electromotive forces were exactly bal
anced. After the condenser and slidewire elec
tromotive forces are balanced, the condenser will
not assume‘the thermocouple electromotive force
until after the lapse of a predetermined interval
required to charge the condenser to the thermo
couple potential and by making this interval of
the proper duration, the motor will be decelerated
and ease the contact 8 ~gradually into its true
balanced position without overshooting. The
proper adjustment of the duration of the lag be
tween the condenser and thermocouple elec
tromotive forces may be readily effected by prop
erly proportioning resistance 65 and condenser H5
in relation to the effective resistance of the cir
cuit including the slidewire resistance 1 and re
sistance 21. When the circuit components are
properly proportioned, the motor may be ex
tremely fast in its rebalancing effect and is capa—
ble of moving the contact 8 completely along the
length of the slidewire resistance 1, a distance of
approximately 12" in some cases, in a fraction of
a second without overshooting and consequent
hunting taking place.
It will be apparent that the motor H may be
employed to operate a control valve or rheostat
for controlling the supply of heating agent to the
furnace 2 to the temperature of which the ther
mocouple 3 is responsive, or another motor de
opposited E. M. F.’s.
2. The method which comprses producing an
M. F. to be measured, periodically impressing
said E. M. F. on an electrical capacitive react
ance to charge the latter, opposing the E. M. F.
on said reactance to a known E. M. F. during
, each interval when said first mentioned E. M. F.
is not impressed on said device whereby the re—
sultant of said opposed E. M. F.’s creates a current
of regular frequency which can be readily ampli
?ed, amplifying said current at said frequency,
_ and applying said ampli?ed currents to effect a
balance between said opposed E. M. F.’s.
3. In measuring apparatus, a circuit including
in
potentiometer resistance, a standard source of
i I.
for said resistance, an electrical energy
..tcring device, means to periodically connect a
scurc
of E. M. F. to be measured to said device
to charge the latter and to connect said device‘
in said circuit to oppose the E. M. F. on said device
to said standard E. M. F. during each interval
when said E. M. F. to be measured is not con
nected to said device to thereby create a pulsat
ing current ?ow of regular frequency in said cir
cuit, means to amplify said pulsating current, and
means energized by said ampli?ed quantity to
eifect a balance between said opposed E. M. F.’s.
4. In measuring apparatus, a circuit including
a potentiometer resistance, a standard source of
E. M. F. for said resistance, an electrical capaci
tive reactance, means to periodically connect a
source of E. M. F. to be measured to said react
ance to charge the latter and to connect said re
actance in said circuit to oppose the E. M. F. on
said reactance to said standard E. M. F. during
each interval when said E. M. F. to be measured
sirably operated together with the motor I I may 45 is not connected to said ‘reactance to thereby
be so employed. For example, as shown in Fig.
create a pulsating current flow of regular fre—
I, the furnace 2 may be heated by a resistance
quency in said circuit, means to amplify said pul
66 which is connected to electric supply conduc
sating current, and means energized by said am
tors L3 and L4 through a rheostat 61 the adjust
pli?ed quantity to adjust said potentiometer re
ment of which may be effected by a motor 68. 50 sistance to effect a. balance between said opposed
The motor 68 may be exactly like motorll and
E. M. F.’s.
is connected in parallel therewith. The mechan
5. In measuring apparatus, a circuit including
ical connection of the rheostat 67 to the motor 68
a potentiometer resistance, a, standard source of
is such as to increase and decrease the supply of
E. M. F‘. for said resistance, an electrical capaci
electric current to the resistance 66 as the tem as tive reactance, means to periodically connect a
perature to which the thermocouple 3 is respon
source of E. M. F. to be measured to said react
sive drops below and rises above a predetermined
ance to charge the latter and to connect said re
level.
actance in said circuit to oppose the E. M. F.
While in accordance with the provisions of the
on said reactance to said standard E. M. F. dur
statutes, I have illustrated and described the best
ing each interval when said E. M. F. to be meas
forms of embodiment of my invention now known
ured is not ‘connected to said reactance to thereby
to me, it will be apparent to those skilled in the
create a pulsating current ?ow of regular fre
art that changes may be made in the forms of
quency in said circuit, means to amplify said pul
the apparatus disclosed without departing from
sating current at said frequency, a source of alter
the spirit of my invention, as set forth in the
nating current of said frequency, a two phase
appended claims and that in some cases certain
rotating ?eld moto; connected to said potentiom
features of my invention may be used to advan
eter resistance for adjustment of the latter and
tage without a corresponding use of other
having one phase energized from said source,
features.
'
and means to apply said ampli?ed quantity to the
Having‘now described my invention, what I 70 other phase of said motor to control the operation
claim as new and desire to secure by Letters
of the latter and thereby the adjustment of said
Patent ‘is:
potentiometer resistance as required to effect a
1. The method which comprises producing an
balance between said opposed E. M. F.’s.
E. M. F. to be measured, periodically impressing
6. In measuring apparatus, a circuit including
said E. M. F. on an electrical energy storing de
a potentiometer resistance, a standard source of
2,404,894
11
E. M. F. for said resistance, an electrical capaci
tive reactance, means to periodically connect a
source of E. M. F. to be measured to said react
ance to charge the latter and to connect said re
actance in said circuit to oppose the E. M. F. on
said reactance to said standard E. M. F. during
each interval when said E. M. F. to be measured 18
tity to said motor to control the operation of
the latter, said resistance and reactance cooper
ating to automatically control the E. M. F. on
said reactance in a predetermined manner with
respect to time on a change in said ?rst men
tioned E. M. F. so as to cause a balance of the
opposed E. M. F.’s in said circuit when the dif
ference between said ?rst mentioned E. M. F. and
not connected to said reactance to thereby create
said standard E. M. F. is equal to the E. M. F.
a pulsating current flow of regular frequency in
by said device under control of said
said circuit, means to amplify said pulsating cur 10 produced
motor following deenergization of the latter.
rent, and means to utilize said ampli?ed quantity
10. In measuring apparatus, a circuit includ
to effect a balance between said standard E. M. F.
ing a potentiometer resistance, a standard source
and the E. M. F. on said reactance.
of E. M. F. for said resistance, an electrical en
7. In measuring apparatus, a circuit including
ergy
storing device, a double pole-double throw
15
a standard source of E. M. F., an electrical energy
switch
to periodically connect a source of E. M. F.
storing device, means to periodically connect a
to be measured to said device to charge the latter
source of E. M. F. to be measured to said device
to charge the latter and to connect said device
and to totally disconnect said device from said
rent, and means to apply the amplified quantity
to said device to control the operation of the lat
ter, said resistance and reactance cooperating to
quency, a source of alternating current ‘of said
E. M. F. to be measured and to connect said de
in said circuit to oppose the E. M. F. on said de
vice to said standard E. M. F. during each inter 20 vice in said circuit to oppose the E. M. F. on
said device to said standard E. M. F. during each
val when said E. M. F. to be measured is not con
interval when said E. M. F. to be measured is
nected to said device to thereby create a pulsat
not connected to said device to thereby create
ing current flow of regular frequency in said cir
a pulsating current flow of regular frequency in
cuit, means to amplify said pulsating current, and
said circuit, means to amplify said pulsating curmeans to utilize said ampli?ed quantity to effect
rent, and means energized by said ampli?ed
a balance between said standard E. M. F. and the
quantity to effect a balance between said op
E. M. F. on said device.
posed E. M. F.’s.
8. Measuring apparatus including means for
11. In a measuring apparatus, a circuit in
producing a variable E. M. F. to be measured,
means for producing a standard E. M. F., a de 30 cluding a potentiometer resistance, a standard
source of E. M. F. for said resistance, an elec
vice having inertia for varying said standard
trical
capacitive reactance, a double pole-double
E. M. F., a circuit in which said standard
throw switch to periodically connect a source of
E. M. F. is permanently‘connected, an electrical
E. M. F. to be measured to said reactance to
capacitive reactance, a resistance, means to
charge the latter and to totally disconnect said‘
35
periodically connect said ?rst mentioned E. M. F.,v
reactance
from said E. M. F. to be measured and‘
said resistance and said reactance in series to
to connect said reactance in said circuit to op~
charge the latter and to connect said reactance
pose the E. M. F. on said reactance to said stand
in said circuit to oppose the E. M. F. on said re
ard E. M. F. during each interval when said
actance to said standard E. M. F. during each
interval when the E. M. F. to be measured is not 40 E. M. F. to be measured is not connected to said
reactance to thereby create a pulsating current
connected to said reactance to thereby create a
?ow
of regular frequency in said circuit, means
pulsating current flow of regular frequency in
to amplify said pulsating current at said fre
said circuit, means to amplify said pulsating cur
frequency, a two phase rotating ?eld motor con
nected to said potentiometer resistance for ad
justment of the latter and having one phase
energized from said source, and means to apply
automatically control the E. M. F. on said react
ance in a predetermined manner with respect to
said ampli?ed quantity to the other phase of
time on a change in said ?rst mentioned E. M. F.
so as to cause a balance of the opposed E. M. F.‘s 50 said motor to control the operation of the latter
and thereby the adjustment of said potentiometer
in said circuit when the difference between said
resistance as required to effect a balance between
?rst mentioned E. M. F. and said standard
said opposed E. M. F’s.
E. M. F. is equal to the E. M. F. produced by said
12. Measuring apparatus including means for‘
device due to its inertia following deenergization
producing a variable E. M. F. to be measured.
of the latter.
65
means'for producing a standard E. M. F., a device
9. Measuring apparatus including means for
for varying said standard E. M. F., a motor ar~
producing a variable E. M. F. to be measured,
ranged to adjust said device when energized and
means for producing a standard E. M. F., a device
having the inertia characteristic which produces
for varying said standard E. M. F., a motor ar
ranged to adjust said device when energized and 60 further adjustment of said device following dc
energization, a circuit in which said standard
having the inertia characteristic which produces
E. M. F. is permanently connected, an electrical
further adjustment of said device following de
capacitive reactance, a resistance, a double pole
energization, a circuit in which said standard
throw switch to periodically connect said ?rst
E. M. F. is permanently connected, an electrical
capacitive reactance, a resistance, means to peri 65 mentioned E. M. F., said resistance and said re‘
actance in series to charge the latter and to
odically connect said ?rst mentioned E. M. F.,
totally disconnect said reactance from said ?rst
said resistance and said reactance in series to
mentioned E. M. F. and to connect said reaccharge the latter and to connect said reactance.
tance in said circuit to oppose the E .M. F. on
reactance to said standard E. M. F. during each 70 said reactance to said standard E. M. F. during
each interval when the E. M. F. to be measured‘
interval when the E. M. F. to be measured is
is
not connected to said reactance to thereby
not connected to said reactance to thereby cre
create a pulsating current 'flow of regular fre-,
ate a pulsating current ?ow of regular frequency
quency in said circuit, means to amplify said pul
in said circuit, means to amplify said pulsating
in said circuit to oppose the E. M. F. on said
current, and means to apply the ampli?ed quan
1; eating current, and means to apply the ampli
2,404,894
13
?ed quantity to said motor to control the opera
tion of the latter, said resistance and reactance
cooperating to automatically control the E. M. F.
the opposed E. M. F.’s in said circuit when the
difference between said ?rst mentioned E. M. F.
and said standard E. M. F. is equal to the E. M. F.
produced by said device under control of said
with respect to time on a. change in said ?rst 5 motor following deenergization of the latter.
on said reactance in a predetermined manner
mentioned E. M. F. so as to cause a balance of
WALTER P. WILLS.
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