Download Measuring instrument of the potentiometer type

Feb. 10, 1942.
E. A. ‘KEELER
2,272,914
MEASURING‘ INSTRUMENT OF THE POTENTIOMETER TYPE
I Filed Sept. 30, 1938
,
'
2 Sheets-Sheet 1
FIG. I.
INVENTOR.
EARL A. KEELER
BY
ATTORNEY '
Feb. 10, 1942.
2,272,914
E_ A_ KEELER
MEASURING INSTRUMENT OF THE POTENTIOMETER TYPE
Filed Sept. 30, 1938
2 Sheets-Sheet 2
A.C. LINE
INVENTOR.
EARL A. KEELER
A TTORNEY
Patented Feb. 10, 1942
2,272,914
UNITED STATES PATENT OFFICE
2.272,914_
MEASURING INSTRUMENT OF THE
POTENTIOMETER TYPE
Earl A. Keeler, Norristown, Pa., assignor to The
Brown Instrument Company, Philadelphia, Pa.,
a corporation of Pennsylvania
Application September 30, 1938, Serial No. 232,586
13 Claims.
The present invention relates to measuringin
strum'ents, and more particularly to an instru
(CI. 17145)
drawings and descriptive matter in which I have
illustrated and described a preferred embodiment
ment that is both sensitive and rugged for meas
of the invention.
uring the value of a condition.
In the drawings:
At the present time it is customary to measure CR
Fig. 1 is a wiring diagram of one form of my
high temperatures by means of a potentiometer
invention showing diagrammatically recording
I circuit in which deflection of a galvanometer in
response to variations in the voltage of a ther
mocouple, subjected to the temperature, is~used
provisions and a furnace;
.
Fig. 2 is a side view of my novel galvanometer;
Fig. 3 is a view on line 3--3 of Fig. 2;
to position a relay which in turn rebalances the 10
Fig. 4 is,a fragmentary sectional view through
potentiometer and adjusts a pen with respect to
one side of the galvanometer coils;
a chart. The di?iculty with such an arrange
Figs. 5 to 7 are wiring diagrams of other em
ment is that the relay mechanism is ordinarily
both cyclic inoperation and cumbersome. It is
bodiments, of my invention;
an object of my invention to do away with the
tion in which the galvanometer pointer does not
necessity of a complicated relay system and the.
necessity of depending upon any cyclically op
'
Figs. 8 to 10 are wiring diagrams of my inven
directly detect the measuring circuit unbalance;
and
erating mechanism in order to rebalance a po
Fig. 11 is a wiring diagram of my invention in
tentiometer circuit and ‘obtain a reading. To this
which the galvanometer pointer serves only to
end de?ection of the galvanometer is directly 20 limit the de?ection of the coil.
used to disclose a circuit and operate a series of
Referring ?rst to Fig. 1, a galvanometer i hav
electrical relays to cause rebalancing of the po
ing a pointer 2 is adapted to ‘respond to unbal
tentiometer circuit. I also provide a mechanism
ance in a null point potentiometric circuit, the
that is free from any cyclic mechanism and is
latter of which may be of any suitable type, such
substantially ‘instantaneous in its response to 25 as the Brown potentiometer circuit disclosed in
any variation of the value of the thermocouple
'Harrison Patent 1,898,124, issued February '21,
voltage.
1933. Such circuits are well-known and it is su?i
It is a further object of my invention to provide
cient for the present purpose to note that the
a measuring instrument which is rapid in action'
potentiometer circuit includes a circuit branch
and one that is inherently stable in operation. 30 including a source of variable potential to be
Such an operation is accomplished with the addi-‘
measured ‘such for example, as the thermocouple
tional feature of obtaining an accelerating action
3 inserted in a furnace 4 whose temperature is to
in the instrument by using a second coil in the
be measured. An opposing circuit branch in
galvanometer which upon energization thereof,
cluding a source of known potential such as the
is used to add an additional biasing force to the .35 cell 5, and resistors 8, a variable portion of the
galvanometer. Upon the completion of a rebal
latter of which may be connected» into the op
ancing operation a circuit through the additional
posed branches by means of a sliding contact 1
or‘auxiliary coil is broken and a recoil action is
whereby the respective effects of the variable and
produced which quickly returns the galvanometer
known sources are made equal and opposite, and
toward its neutral position. It is a further ob 40 the galvanometer is thus rendered undeilected
ject of my invention to provide a galvanometer
when the circuit is balanced for a given value of
which has two movable coils, one of which is in a
the E. M. F. of the thermocouple 3- with contact
measuring circuit to cause a de?ection thereof,
‘I in a corresponding position along the resistors
and the other of‘ which is in an auxiliary or
6. The position of contact ‘I is then a measure
biasing circuit and is used to add an additional 45 of the value of the thermocouple E. M. F. and
force to that-of the ?rst coil and toy provide a
may then‘serve as a measure of thevv temperature
means that produces'a recoil action upon break
_ to which it is exposed.
ing of the circuit.
'
.
.
In the form of Figure 1 my invention is ‘con
The various features of novelty which charac
cerned with the manner in which the contact ‘I
terize my invention are pointed out with particu 50 is moved along the resistances 6 to rebalance a
larity in the claims annexed to and forming a
potentiometer circuit. The contact ‘I is mounted
part of this speci?cation. For a better under
on and movable with a carriage 8 that is shifted
‘standing of the invention, however. its advan
in response to rotations of a threaded shaft 9
tages and speci?c objects obtained with its use,
uponpwhich the carriageis mounted. Also fas
reference, should be had to the accompanying 55 tened to the carriage 8 is a marking‘element i0
2
8,272,914
that is adapted to move across a chart II. This
through the circuit which includes contacts 2|
chart is provided with calibration marks in
and 2|, coil 2|, battery 2|, conductor 21, coil
terms of the temperature to which the thermo
couple is exposed and is driven past the marker
2|, contacts 25 and 24, conductor 22, coil H and
pointer 2, regardless of its low magnitude will
III by a motor I2 and a driving drum l2.
produce‘a torque which is additive to that pro
The construction of the galvanometer l ‘which
I use is novel and tormsa highly important fea
duced by the current in the coil II to thereby
cause additional pressure between contacts 2|
and 2|, to permit a greater current ?ow there
through. Thus the current builds up until it is
ture of my invention. The galvanometer em
ployed may desirably be heavily damped and con
sists of a frame H of usual form upon which is 10 suilicient to energize the relays Ill and 2| and
open their respective switches 22 and 24. As
wound‘a coil || whose terminals I511 and ||b
the switch 22 opens, the motor 24 will rotate
are connected in the potentiometer circuit. A
second coil I8 is also wound upon the frame I4 '- shaft 9 and adjust contact ‘I along resistance
| in a direction to restore potentiometer balance.
and this coil has one lead connected to the pointer ’
2 while the other lead extends to a relay circuit 15 Switch 24 is an interrupter switch which pref
erably is not opened until the motor N has per
to be described below. These two coils l5 and
formed a rebalancing operation. The time de
I8 do not have any electrical connection with
lay between the opening of switch 22 and the
each other. Extending from each end of the
opening of switch 24 is due to the fact that a
frame M are the usual bearing shafts that are
greater flow of current is required to actuate
pivoted in any suitable manner in frame members
that relay to move contact 2| out of engage
l1 and ||. The pointer 2 is attached to the
ment with contact 2| and break the holding cir
lower supporting shaft and is in the form of a
cross, three arms of which are threaded and re
ceive balancing weights || that are adjustable to
insure free turning of frame l4. The fourth arm
is the pointer proper and has contact element 2|
formed on its tip, which contact is adapted to
cooperate with either of the adjustable contacts
2| and 22 depending upon the direction of de?ec
tion of the galvanometer coils.
,
Referring now to Figure 1 it will be seen that,
as above described, one end of coil l| is con
nected to pointer 2 while the other end'is con
nected by a conductor 22 to a movable contact
24 that forms part of a switch. The other con
tact 2| of the switch is connected to one end of
a relay 2| that is connected by line 21 to the mid
point between two batteries 2| and 2|. The other
cuit. Opening of switch 24 permits relay 2| to
again close switch 22 to stall motor 24 and relay
2| to close contacts 24 and 2|. If the movement
of contact I along the resistances 6 was suiii—
cient to rebalance the potentiometer circuit the
contacts 2| and 2| will now be open. If not,
the same cycle of operations will occur and the
motor will be rotated in a series of short, rapid
steps until the potentiometer circuit is re
balanced.
Upon the occurrence of a de?ection of pointer
2 in a clockwise direction the opposite of the
above operations will take place and relay 2|
will open switch 22 to permit motor 34 to rotate
in a reverse direction from that in which it pre- I
viously rotated. It is noted that the battery 2|
is of such a polarity that the current ?ow, in
terminal of battery 2| is connected to one end of
a relay coil 2| whose other end is connected to ll) this case, through the coil || will increase the
pressure between contacts 2| and 22 until the
the contact 2|. In a like manner the second ter
current flow is suillcient to energize the relay
minal of battery 2| is connected to one end of
2|.
a relay coil || whose second end is connectedto
The embodiment of the invention disclosed in
the contact 22. The relays 2| and 2| are adapted,
when energized under control of the galvanome 45 ll'lgureoisverysimilartothatinli'ig. 1,the
ter, to open the normally closed switches 22 and - diilerence being in the manner that relay 2| is
connected in the circuit. In this embodiment
22, respectively, to which switches are connected
the relay 2| is of the ‘time delay type and is nor
on one side to the line and on the other side to
mally energized to hold contacts 24 and 2| closed.
the ?elds of a standard reversible induction mo
Each of the relays 2| and 2| when energized in
tor 2| and from there to the other side of the
addition to actuating vthe motor switches, also a
line. In a circuit of this type when one of the
open respectively switch 2| and switch 2| in the
switches is opened, one field of the motor is con
circuit of the relay 2|. The switches 2| and 2|
nected directly to the line and the other is con
are shown connected at each end of the relay
nected to the line through a condenser 2|a. In
such a case the energizing current for one of the 55 2| so that when either is opened, switch 2| by
relay 2| or switch 2| by relay 2|, the connec
rotating ?elds lags the other to set up a rotating
ileld in the rotatable element of the motor, the
direction of rotation depending upon which is
leading. Upon energization of one of the relays
2| or 2| by the galvanometer a switch is opened
in one field circuit and the motor is energised to
rotate shaft | to shift carriage | in the proper
direction for contact ‘I to rebalance the poten
tiometer circuit.
In the operation of this embodiment of the
invention if the thermocouple voltage varies in
tion between the batteries” and 2| and ‘the
‘relay 2| will be broken. -
In the operation of this embodiment a varia
tion in the thermocouple voltage will cause a
de?ection of the galvanometer pointer 2 to bring
contact 2| into engagement witheither contact
2| or contact 22. If, for example. the contacts
2| and 2| engage, a circuit will be completed
from‘ contact 2| through relay”, battery a.
line 21a switch 2|, 2|, line 22 coil ||, pointer 2
a direction to cause coil II to move counter
‘ clockwise in Figure 1 the contact 2| will be
and contact 2| to energize relay 2| in a manner
pressure between the contacts 2| and 2| to cause
direction,. while opening switch 2| deenergises
su?icient current to now through the circuit to
operate relay 2|, though a very small current
the relay 2|.
previously described. When the current flow
has built up sufficiently the relay 2| will open
moved into engagement with contact 2|. In the
ordinary form of galvanometer, a slight poten 70 switches 22 and ||. Opening switch 22 permits
motor?torotatetodriveshaftlintheproper
t‘ometric unbalance will not result in suiilcient
may‘ ilow between the contacts. This ?ow
when the relay 2| 7 is deenergised
an interval of time will occur before contacts
2| and2lareseparatedanditisduringtmsin
2,272,914
terval that motor, 34 rotates. When contacts
24 and 25 open they break the holding circuit
for relay 36 to deenergize that relay and close
switches 32 and 35. The closing of the former
stops the motor and the closing of the latter
energizes relay 26 to close contacts 24 and 25
and places the circuits in condition for another
3
use of a recti?ervin a source of A. C. voltage to
produce the D. C. for the relays instead of the
batteries previously disclosed. It is of course to
be understood that the batteries may be used
if desired in this case just as the recti?er can
be used instead of the batteries in the previously
described embodiments.
One end of relay 36 is connected as usual to
As in the embodiment of Figure 1, if the con
contact 2| and the other end is connected at
tact ‘I was not moved enough to rebalance the 10 33 to a voltage divider 46. The other relay 3|
potentiometer circuit the operation will be suc
is connected at 4| to the other end of the voltage
cessively repeated until potentiometerrebalance
divider 46 and to the contact 22. A center 'tap
is obtained. Upon the occurrence of an opposite
42 of the voltage divider is connected through
galvanometer de?ection, where contacts 26 and
the switches 35 and 36 .to the conductor 23 and
22 are brought into engagement, the relay 3| 15 from there to the coil l6 to complete the circuit
will be energized and it will open switches 33 and
for the relays 36 and 3| respectively when pointer
36 to respectively cause an opposite rotation of
2 is de?ected to bring contact 26 into engage
motor 34 from that previously obtained and to
ment with either contact 2i or contact 22.
deenergize the relay 26.
Shunted across the switches 35 and 36 is a vari
‘The embodiment of the invention disclosed in 20 able resistance 43 and a condenser 44 in series,
Figure 6 differs from those previously described
which upon opening of either switch 35 or 36
in that only two relays are used with a condenser
is placed in circuit with the relays 36 or‘ 3|.
in each relay circuit serving to permit the neces
The voltage divider 46 is supplied from an A. C.
sary time delay during which the motor 34 is
‘source through a copper oxide recti?er 45 of
energized for rotation.
25 usual type and a transformer 46.
In this embodiment one end of relay 36 is con
In the operation of this embodiment of the
nected, as previously, to the contact 2| while
invention a de?ection of the galvanometer pointer
the other end is connected both to one contact
2 will move contact 26 into engagement with,
of the switch 35 and one terminal of a condenser
for example, contact 2|. A circuit will thus be
31 of suitable capacity. The other terminal of 36 completed from contact 2|, relay 36, the upper
the condenser and the other contact of the switch é' half of voltage divider 46, through center tap
are both connected to one terminal of the bat
42, switch 35, switch 36, conductor 23, coil l6,
tery 28. In a like manner one end of relay 3|
pointer 2 to contact 26. When the current is
is connected to contact 22 while the other end
su?icient the relay 36 will be energized to open
is connected to one contact of switch 36 and 35 switches 32 and 35. As in the previously de
one terminal of a second condenser 36. The
scribed embodiments of the invention the open
ing of switch 32 will permit the motor 34 to rotate
second contact of switch 36 and the second
terminal of condenser 38 are connected to one
shaft 3 and move contact 1 across resistances 6
terminal of battery 29. The conductor 23 in
to rebalance or tend to rebalance the potenti
this case extends from coil l6 to a connection be 40 ometer circuit. The opening of switch 35 breaks
the circuit for relay 36, but deenergization of
tween the batteries.
operation.
>
‘
'
In the operation of this embodiment a varia- '
tion of the thermocouple voltage will cause a
de?ection of the pointer 2 to bring, for example,
contacts 26 and 2| into engagement. Thus, in
a manner described in connection with Figure
1, a flow of current is set up through contact 2|,
coil 36, switch 35, battery'26, conductor 23, coil
i6, pointer 2 and contact 26. When sufficient
current has been built up in the circuit the relay
the relay is delayed due to the subsequent charg
ing of condenser 44. The time interval during
which the charging of the condenser takes place
determines the lengths of time that the motor
34 is rotating and this interval can, be varied by
adjusting the value of resistance 43.
In a similar manner a de?ection of the gal
vanometer to bring contact 26 into engagement
with contact 22 would cause energization of relay
36 will become energized to open switches 32 and
'35. The opening of switch 32 permits the motor
3|, this time using the lowerhalf of the voltage
divider 46 between point 4| and center tap 42
to rotate shaft 3 to shift contact ‘I along re
in order to reverse the direction of ?ow of the
current in the circuit. This is necessary in order
sistances 6 in a direction to rebalance,‘ or tend
to rebalance, the potentiometer circuit. The .55 that the coil |6 will bias the pointer toward
opening of switch 35 breaks the circuit for relay
contact 22 instead‘ of‘ toward contact 2| as it
formerly did.
’
36, but the relay is not instantly deenergized
due to the charging of condenser 31. The in
In each of the above described embodiments
terval of time during which the condenser is
of the invention, the additional torque on the
charging after switches 32 and 35 have been 60 galvanometer that is derived from the secondary
opened and before the relay 36 is deenergized is
coil I6 is used to add to the unbalance of the
the time during which the motor 34 is rotating
galvanometer. I have discovered that if this
shaft 9. This operation is, as in the previously
force, with relation to the galvanometer design
described forms of the invention, rapid enough
is such that it tends to slightly bend the pointer
so that a substantally continuous rotation of 55 2 between its point of support and contact 26
the motor is obtained until the potentiometer
or to shift the coil in its pivots, or both, a rapid
circuit is rebalanced. For an opposite de?ection
recoil takes place when the circuit is broken.
of the galvanometer the same operation would
The eifect secured is quite valuable and sub
take place through relay 3| and condenser 36 to
stantial in that it gives an acceleration feature‘
energize the motor 34 for rotation in the oppo 70 to the operation of the device.
site direction.
In a self-balancing instrument of the general
. The embodiment of the invention disclosed, in
type shown in Fig. 1, “hunting” or oscillation
Figure '7 is similar to that of Figure 6 except
of the device may occur by virtue of the time
that only one condenser is used instead of two.
lags-and particularly the mechanical time lags
Also there is disclosed in this embodiment the 76 involved. For example, the, time ‘necessary to
4
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galvanometer pointer is so great compared to the
speed of the electrical changes in the potenti
ometer system that nothwithstanding the rota
ever of relays 25 or 3| was energized. If the ro
tation of the motor 54 was su?icient to rebal
ance the measuring circuit the galvanometer
coil will remain in its neutral position, if not the
tion or motor 34 into a position which the con
tact should occupy to rebalance the system under
a stabilized. condition, the galvanometer will et
same cycle of operations will be repeated until
the measuring circuit is rebalancr‘d.
Another, type of relay mechanism is shown in
iect further motor rotation before such rotation
is interrupted. While for a slow motor opera
connection with my invention in Figure 9, which
relay uses a so-called “A. C.-D. C." galvanometer.
overcome the inertia of even a light and delicate
tion, the system may be suitably damped with 10 As shown the moving coil I! of the galvanometer
is connected by means of pigtails or slip rings 52
auxiliary means, it is essential for high-speed
and 53 with the leads lid and I5!) while the
recorder operation to insure that motor 24 will
auxiliary coil |l is connected at one end by slip
come to rest exactly at its balance point. The
ring 54 with the conductor 22. A iclr-up coil
recoil action referred to above following deen
ergization of the galvanometer coil II, it prop 15 55, which is positioned in an alte ating mag
nétic ?eld, is connected to the pivot of the gal
erly predetermined in magnitude, as it can be
vanometer coils l5 and I6 and is arranged to be
by adjustment of the biasing force of coil II.
rotated therewith. The pick-up coil is connect
in a manner hereinafter described, will restore
ed between the poles of a suitable ?eld structure
the galvanometer to its neutral position, thereby
interrupting the action of the rebalancing motor. 20 55 on which is wound a ?eld winding 51 that is
energized from a suitable A. C. supply line, and is
Another type of relay mechanism with which
so arranged with respect to the poles of the ?eld
my invention may be used is shown in Fig. 8.
structure 56 that when the coil I5 is in its un
In the previously described embodiment the
de?ected position the pick-up coil is in zero in
pointer 2 was used both to detect the unbalance
oi the measuring circuit and to close the circuit 25 ductive relation to the alternating magnetic ?eld
set up in the ?eld structure. When the galva
through coil It. That this double function of
nometer moving coil i5 de?ects in one direction
the pointer is not necessary is shown in the
or the other the pick-up coil de?ects accordingly
embodiment now to be described.
and, as a result, an alternating voltage in phase
In Figure 8 the galvanometer coil i5 is respon
sive to variations in the measuring circuit as 30 with or 180° out of phase with the line voltage
will be induced in the pick-up coil.
.
in the previously described embodiment. ~The
In the operation of this embodiment, when the
cell has attached to it for movement therewith,
thermocouple voltage changes the galvanometer
in addition to the pointer 2, a mirror 41 that
moving coil l5 will be de?ected in one direction
is adapted to reflect a beam of light from some
or the other and thereby the pick-up coil 55 will
suitable source, such as from the lamp 4!, to
be rotated into inductive relation with the alter
a photocell 49. A mask 50 is provided in front
of cell 4! so that if the galvanometer de?ects in
nating magnetic ?eld set up by the ?eld struc
one direction the beam falls on the cell and it
it de?ects in the other direction the beam is on
the mask. The current from cell 49 goes to
an ampli?er 5| that is used to _energize one or
the other of the relays III or 5| depending upon
whether the light beam is on the cell 49 or the
ture 56, resulting in the induction of an alter
nating voltage in the pick-up coil. The phase
and amplitude of the alternating current so in
duced is determined by the direction and extent
oi’ de?ection, respectively. The induced alter~
mask 50. If the galvanometer is in its neutral
position the beam falls equally on the cell and
mask and neither of the relays is energized.
Various forms of ampli?er relays are available
which would be suitable for use as ampli?er 5|,
tails or slip rings 58 and 59 to the input terminal,
of an electronic ampli?er 60. The output of
nating voltage is connected through suitable pig~
' ampli?er O0 is connected to one winding of a ro
tating ?eld motor 8|, the other ?eld of which is
connected to line. As is well known, motor 5| is
and in particular the device 5| may include a re
energized for rotation in one direction or the
lay for a coil responsive to the ampli?ed photo
cell current and a pair. of contacts adapted to
control the energization of coils 3|! and II ex
cept for the normal current condition of the
other depending upon the phase of the current
supplied from ampli?er 60. As in the preceding
embodiments motor 8| is adapted to effect an
adjustment in the rebalancing direction of the
contact ‘I along the resistances 6.
photo-cell circuit existing when the galvanometer
is in its neutral position. See, for example,_the
ampli?er disclosed below in connection with
Figure ll.
The function of coil I8 is the same in this em
bodiment as it was in the embodiment of Fig. 8,
When either of the relays 20 or 3| is energized.
it opens its switch 32 or 22, respectively, to per
mit rotation of the motor 34. As the galva
nometer deflects it brings contact 20 on pointer
2 into engagement with either contact 2| or 22
engagement with either contact 2| or 22 to com
plete a circuit from one of those contacts through
namely to e?ect rapid mechanical rebalance of
the galvanometer. Upon de?ection of the v gal-'
vanometer, pointer 2 will bring contact 20 into
either battery 28 or 29, switch contacts 25, 24,
coil 28, line 23, slip ring 54, coll I8 to the pointer
2. When the current ?ow through the relay 2|
tacts, battery 22 or 2!, switch contacts 24 and
H25, coil 24, line 22, coil I‘ back to pointer 2. The 65 has increased to a large enough value the relay
will be energized to open‘ contacts 24 and 25 to
battery brought into ‘the circuit is of such a p0
break the circuit._ If the potentiometer[circuit is
larity that the current v?ow through coil l6 in-v
not rebalanced the cycle will be repeated until
creases the bias of pointer 2 in its initial direction
to complete a circuit through one of the con
' to increase the pressure between-contact 2|! and
suchtime as it is.
contacts 2| or 22. As the current in the relay 25 70 My invention is shown in Figure 10 in use with
a capacitance type relay. In this embodiment
increases it will movecontact 24 away from con
a condenser plate 62 is carried by and insulated
tact 25' to
the circuit and the galvanometer
Winter" 2:,willspring back to its neutral position;
thiQiIsOImQves ‘the beam of’ light until it is equal
from the pointer 2.
This plate moves relative to
a second stationary condenser plate 83, the plates
ly_ on the cell 45 and-mask ‘I to deenergize which 75 being connected to an oscillator 54 the output cur
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rent of which varies in response to the relative
positions or the plates 62 and 63. As the output
current of the oscillator varies the energization
of a relay coil 66 varies in accordance therewith
to shift its armature 66 that is used to control the
position of a switch member 61, which is pivoted
at its left end. An adjustable spring 61a urges
member 61 toward contact 69 from which it is
normally held in the neutral position of the
galvanometer by the normal current value in
coil 65.
t
.
5
balanced the‘ cycle will be repeated until such
.
is the case.
From the above description it will be seen that
by providing a second coil in the galvanometer
I am able to use the galvanometer pointer direct
ly to actuate the rebalancing system of a po
tentiometer circuit. By having the two coils on
the galvanometer frame separate from each other
no disturbing in?uence is introduced into the
thermocouple circuit and its initial sensitivity can
be retained. The motor 34 is caused to rotate
In the operation of this embodiment of the in
in a series of steps that are short enough to
vention when the pointer 2 is in its neutral po
give small movements to the contact ‘I and thus
sition the plates 62 and 63 are in such relative
the possibility of moving the contact too
positions that the oscillator output current 15 render
far negligible. On the other hand the steps fol
through relay 65 is su?lcient to keep the switch
low each other in quick enough succession that
member 61 out of engagement with contact 69.
for
larger unbalances of the potentiometer cir
When, however, the galvanometer de?ects due to
cult the rotation of the motor 34 is substantially
.a change in the thermocouple voltage the relative
positions of the plates 62 and 63 are changed to 20 continuous so that the contact -‘I may move
smoothly across the resistances 6. '
vary oscillator output current and thereby
" In cases where the pointer does not form
either increase or decrease the energizing force
part of the electrical relay system it still serves
of relay 65 and bring switch member 61 into
an important part by acting as an element in
engagement respectively with contact member
68 or 69. Contacts 68 and 69 are connected to
the fields of an ordinary reversible series motor
34A which is adapted to serve the same pur
the circuit of the auxiliary coil l6 or acting as a
stop to limit the de?ection of the galvanometer
coils. In any event the use of the pointer in
a manner above disclosed and the auxiliary coil
on the galvanometer produces a quick acting and
The coil I6 has the same function in, this em
bodiment of the invention as it has in the pre 30 inherently stable device which has an anticipat
ing effect. The latter is true because after each
viously-described ones and operates here in a
rebalancing step of the motor the recoil action
manner identical to Figures 8 and 9.
produced by deenergization of the coil I6 always
The embodiment of the invention disclosed in
pose as motor 34 of Fig. 1.
Figure 11 is very similar to that disclosed in Fig
returns the galvanometertoward its neutral po
electrical circuit for the coil l6. In this form
tion. The introduction of the relays in the sys
ure 8, but differs from that embodiment and from 35 sition to immediately stop the motor 34 and‘pre
vent any overrun or hunting of the system it
the other embodiments previously disclosed in
the potentiometer has reached balanced condi
that the pointer 2 does not form part of the
tem permits the use of a motor which is suf
and ‘II to limit its movement and that of the 40 ?ciently powerful to move the contact ‘I and pen
l0 and to actuate any desired controls that may
mirror 41.‘
be used in connection with the system.
The circuit for the coil l6 extends from one
the pointer cooperates with adjustable stops ‘I6
end of the coil through conductor 23, normally
I have thus provided a measuring instrument
closed contacts 24, 25, relay 2'6‘, normally open
which is free to instantaneously respond to any ~
variation in the condition which it is being used
switches 12 or 13, actuated by relays 30 or II,‘
batteries 28 or 29, respectively, and conductor 45 to measure, without the necessity of relying on
the cyclic operation of any relay mechanism and
14 to the coil I6. In this case the contact mem
without the necessity of introducing the result
ber 24 is shown provided with an adjustable
ing complications of such a relay mechanism
spring 24a that tends to hold it in closed po
'
sition. In this manner more current has to be 50 into the instrument. '
It should be noted in connection with the re
built up in the coil 26 before it can break the
coil or acceleration effect, particularly in com
circuit through contacts 24 and 25 and an ad
nection with Fig. 9 which does not employ a
justable time delay is provided. It is obvious
contacting relay for rebalancing motor control,
that a similar spring may be used if desired, in
this relay in the other embodiments of the in 65 that advantage may be taken of this effect in a
device which does not include a step-by-step mo
vention.
1
tor action, which step-by-step action in itself
In the operation of this embodiment, a varia
tends to decrease thenecessity for anti-hunting
tion of the measuring E. M. F. through the coil
I! will cause a de?ection thereof to move point
or acceleration features.
‘
‘
While in accordance with the provisions of the
er 2 into engagement with one of the stops 10 '
or ‘II and move mirror 41 so that it will re 60 statutes, I have illustrated and described the
?ect the beam or light either completely on the
photocell 49 or the mask 66. In either case one
of the relays 30 or 3| will be energized. Assum
ing that relay 30 is ‘energized, the switch 22
best form of my invention now known to‘ me,
it will be apparent to those skilled in the art
that changes may be made in the form of the
apparatus disclosed without departing from the
will be opened to permit motor 24 to run and 65 spirit of my invention as set forth in the ap
shift the contact 1 along resistances 6. At the
pended claims and that in some cases certain
"same time the switch ‘I2 will be closed to com
features of my invention may sometimes be used
plete the circuit between'it, battery 26, coil l6,
to advantage without a corresponding use of
switch 24, 26 and the relay 26. vWhen sutncient~ 70 other features. ‘ a
_. , current has been built up in the relay 26 to over
Having now described my invention, what I
come the force of spring 24a it will open switch
clog: as new and desire to secure by Letters Pat
24, 26 to deenergize the coil I6 and permit the
galvanometer to move to its neutral position. If
en
:
1. In'a self-balancing measuring instrument,
the measuring; circuit has not been completely 75 a galvanometer having a pair of coils associated
6
2,272,914
therewith and a pointer, one of said coils being
in the measuring circuit which includes a varia
ble to be measured and to which said coil is re
sponsive, a motor for rebalancing said circuit,
control circuits for said motor, the other oi’ said
coils being selectively connected in one or the
other of said control circuits in accordance with
the direction of de?ection of said galvanometer
pointer in response to changes in said variable.
2. In a measuring instrument a gaivanometer
responsive to variations in a measurable condi
tion, a control circuit comprising a relay coil, a
switch actuated thereby and a source or current,
means to energize said second coil and means
‘ to deenergize said second coil a predetermined
time later.
8. In a sell-balancing measuring instrument, a
galvanometer having a pair of coils associated
therewith one or which is in a measuring circuit
that includes a variable to be measured and to
which said coil is responsive, a motor to rebal
ance said circuit, control circuits ior said motor
responsive, respectively, to said galvanometer de
?ections in one sense or the other, an additional
biasing force for said galvanometer including
said second coil, means to energize said coil in
opposite directions in response to de?ection 01'
responsive to de?ections of said galvanometer to 15 said galvanometer in one direction or in the op
posite direction from a neutral position, and
close said circuit and energize said relay coil to
means operative in response to energiaztion oi’
open said switch, charging of said condenser pre
said second coil to complete one of said motor cir
venting immediate deenergization of said relay
a condenser shunted across said switch, means
coil.
cuits.
.
-
.
.3. In a measuring instrument a galvanometer 20
9. In a measuring instrument, the combination
de?ecting in response to variations in a measur
with a galvanometer having two coils associated
able condition, a circuit comprising a normally
therewith one 01 which is connected in a meas
deenergized relay coil, a normally closed switch
uring circuit that has a variable to be measured
operated thereby, and a source of current, a sec
.to which said coil is responsive, a pair of biasing
ond switch in said circuit closed in response to 25 circuits each including said second coil, means
de?ections of said galvanometer to thereby close
responsive to de?ection of said galvanometer in
said circuit to energize the relay coil and open
either direction to close one or the other of said
the ?rst switch, a‘ condenser shunted across said
biasing circuits to add an additional force to the
?rst switch, the condenser charging through the
galvanometer in one direction or the other,
30 means forming part 0! each circuit to break said
relay coil when the ?rst switch is opened.
4. In a measuring instrument, a galvanometer
biasing circuit and suddenly release said iorce
de?ecting in response to variations in a measur
whereby the galvanometer will spring back to
able condition, a ?rst circuit comprising a ?rst
ward its neutral position.
relay coil, a source of current, a second relay coil
10. In a measuring instrument, a galvanometer
and a switch operated thereby, a second circuit as adapted to de?ect in both directions from a mid
comprising a third relay coil, a source of current,
position and having two coils, one 0! said coils
said second relay coil and said switch, means re
‘ being in a measuring circuit and being respon
sponsive to de?ections 01' said galvanometer to
sive to variations thereof to cause de?ections of
close one of said circuits to energize said ?rst or
said galvanometer, a pair of control circuits each
third and second relay coils, said second relay 40 comprising a relay coil and a source of current,
coil opening the said switch to deenergize said
means responsive to de?ection 01.’ said galvanome
relay coils, and control apparatus operated by ‘’ iter to place the second coil thereof into one of
said ?rst and third relay coils.
said control circuits and to close the said circuit
5. In a device of the class described, control
whereby to energize said relay coil, means re
circuits each comprising a relay coil, a switch 45 sponsive to said energization to break said cir
operated thereby to open the circuit and a source
cuit and time delay means to retard deenergiza
of current supply, a condenser shunted across
tion ot‘said relay coil.
said switches. a device responsive to variations in
11. In a measuring instrument the combina
a condition adapted to complete one or the other
tion with a measuring circuit, a galvanometer
50
of said circuits to cause energization of one or
having two independent coils one of which is in
the other of said relay coils to open its respec
said measuring circuit, a pointer for said gal
tive switch in response to the direction oi the
vanometer, the second of said coils being con
variation, and control apparatus operated in re
nected at one end to said pointer, a pair 0! con
t:Kionse to the energization 0! one of said relay
is.
v
trol circuits each including said second coil, said
55 pointer, an individual source of current and an
6. In a measuring instrument the combination
with a potentiometer circuit, a galvanometer
having a pointer and a pair of unconnected coils,
individual relay coil, means responsive to de?ec
one of said coils being in the potentiometer cir
cuit, a pair of alternate control circuits, means
including said pointer to connect the second gal
vanometer coil in one or said control circuits de
pending upon the direction 01 movement of said
in the opposite direction to close the other of
pointer and control apparatus operated by said
tion 0! the pointer in one direction to close one
of said circuits and to de?ection of the pointer
said circuits and thereby energize one 01’ said re
lay coils, means operative upon closure of the
circuit to open the circuit and means to inject a
" time delay into‘ the opening means.
12. In a measuring instrument, a galvanometer
65 responsive to a variable condition, a coil carried
control circuits.
7. In a self-balancing measuring instrument, a
by said galvanometer, a motor, a pair‘ 0! control
galvanometer having a pair of coils, one of said
circuits therefore each including said coil, means
coils being in the measuring circuit which in
responsive to de?ection of said galvanometer in
either direction to energize one 0! said pair of
cludes a variable to be measured and to which
said coil is responsive, a motor for rebalancing
control circuits for said motor depending upon
said circuit, control circuits for said motor re
the direction 0! de?ection, adjustable mechani
sponsive, respectively, to the direction 01 de-.
cal stops to limit the de?ection of said galvanom
lie'ction oi the galvanometer, means to quickly
eter, completion oi either of said control circuits
open either of said control circuits upon comple
through said coil operating to bias said galvation thereof comprising the second or said coils, 75 nometer‘ for further rotation in‘themdirectlen of
7
2,272,914
the stop limiting the movement thereof, ‘and
means operated following completion of either 01'
said control circuits to break said control cir
cuit, discontinue said biasing means, and stop
said motor.
13. In a measuring instrument the combina
.tion with a measuring circuit, of a galvanometer
having a pair of coils associated therewith one
of which is in said measuring circuit, a pointer
for said galvanometer having a contact on the
end thereof, a pair of cooperating contacts, the
second of said coils being electrically connected
to said pointer, a pair of control circuits each
including said second coil, said pointer and its
contact, a source of current, a relay coil and one
of said cooperating contacts, de?ection of‘ the
pointer in one direction into engagement with
one of said cooperating contacts operating to
close one control circuit, and de?ection of the
pointer in the opposite direction into engagement
with the other of said pair of contacts operating
to close the other control circuit, completion of
either of said control‘circuits through said sec
ond coil operating to bias said pointer for fur
ther rotation in the direction of the cooperating
contact it is engaging, and means operating fol
lowing the completion of either control circuit to
break said control circuit and discontinue said
biasing means._
"
EARL A. KEELER.