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Патент USA US2388534

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Nov. 6, 1945.
R. K] FRAZIER
2,388,534
POTENTIOMETER
Filed June 4, 1942
T0
RECEIVER
' UNDER
TEST
INVENTOR
' RADFORD K. FRAZ/ER
ATTORNEY
Patented Nov. 6, 1945
2,388,534
UNITED STATES ‘PATENT OFFICE
2,388,534
POTENTIOMETER
Radford K. Frazier, Baltimore, Md., assignor to
‘f Bendix Aviation Corporation, South Bend, Ind.,
a corporation of Delaware
'
Application June 4, 1942, Serial No; 445,742
11 Claims. (01. 178-44)
This invention relates to potentiometers and
plished by a potentiometer design in which the
more particularly to potentiometers for use at
magnetic linkage between the potentiometer im
very high frequencies.
pedance element and the controlled circuit is
Potentiometers commercially available at this
substantially zero for a predetermined position
time usually comprise an arcuately shaped re
of the movable potentiometer arm.
sistance element over which a contacting arm is
moved by the rotation of 9. centrally located shaft.
Connecting terminals are attached to either end
of the resistance element and a third connect
ins terminal establishes contact to the rotatable
arm via a ?exible brushor its equivalent. The
Other objects and advantages of the invention
will in part be disclosed and in part be obvious
when the following speci?cation is read in con
’iunction with the drawing in which:
resistance element normally occupies a circular
sector of approximately 330 degrees; and the
terminals making connection to the element ends
are therefore approximately thirty degrees apart,
the arm terminal being located centrally in this
cordance with the principles of the invention.
Figure 2 is a side view showing additional de
tails of the potentiometer construction of Fig
thirty degree sector.
The circular shaped resistance element may be
viewed as one turn of an inductance coil produc
Figure 1 is a rear view showing the essential
elements of a potentiometer constructed in ac
'
ure
1.
‘
Figure 3 is a rear view of an alternative form
of potentiometer also designed in accordance
with the principles of the invention.
Figure 4 shows a typical utilization circuit
ing the type of magnetic ?eld normally asso 20 wherein the advantages of this new potentiometer
ciated with such coils. This field links, not only‘
are of particular importance.
with the loop formed by the resistance element .
itself, but also with the loop circuit enclosed by
It is to be understood that the drawing is
intended to illustrate specific forms of ‘the in
' the movable contact arm and the stationary con
vention, and are not to comprise a limitation on
nector to the rotatable am. With direct current
the content or scope of the invention.
applied to the resistance element and the contact
In the drawing, like parts are designated by
arm rotated to one end of the element, it is
like reference characters.‘
found that no potential appears between the con
Referring to Figure 1, there is shown the cir
tact arm terminal and the winding terminal with
cular impedance element I mounted on the base
which the arm is in contact. With high frequen 30 2 of insulating material by the screws 3 passing
cies of the order of 100 megacycles impressed on
through the mounting ears 4 which form a part
the resistance element, however, considerable
voltage may be measured between the contact
arm terminals and the winding terminal, thus
making it impossible to obtain zero voltage out
put from the potentiometer. This is- particu
larly detrimental in signal generator attenuators
for use at the above frequencies and must be
, eliminated for satisfactory operation. I have
traced the source of this voltage to the magnetic
coupling existing between the resistance element
and the area included between the contact arm
and the stationary connector establishing con
nection to the contact arm.
One of the principal objects of the invention
is to provide an improved potentiometer for the
of the impedance element I. v For frequencies
greater than 80 or 90 megacycles per second a
strip of copper or other highly conductive mate
rial approximately one thirty-second of, an inch
thick may be used for element 1 as the'reactance
of the loop is su?icient to provide the desired im
pedance. The arm 5 is movable over the element
i upon rotation of the shaft 5, to which the arm
5 may be secured by the sweated collar ‘I. Elec
trical connection to the arm 5 is established
through the fixed contact arm 8- which by virtue
of its form in the region of the shaft, is main
tained in contact with arm 5 under spring ten
45 sion. It is to be noted that arm 5 is of somewhat
unusual form for a purpose to be discussed more
control of high frequency alternating currents.
Another object of the invention is ‘to ‘provide
fully below. Electrical connections for the ener
gization of the element 1 may be made by two
a new and novel potentiometer in which the out
wires slipped through the apertures 9 and I0 and
put vs. rotation characteristic in the low output 60 soldered in place. Apertures H in the base 2 are
position is independent or the applied frequency.
provided for convenience in mounting the
Yet another object of the invention is to pro
vide an improved potentiometer for use with high
assembly.
Turning to Figure 2, the side view of the po
frequency alternating currents in which the out
tentiometer of Figure» 1 shows the bushing l5
put voltage measured between the connector to 55 mounted in the base 2 and secured by the nut 16.
the movable arm and one end of the impedance
The shaft 6 passes through the'bushing' l5 and
element is substantially zero when the movable
is kept in place by the O-shaped washer II which
arm is in contact with said end of said imped
is snapped into the groove l3. The collar 1 is
ance
'
sweated on the shaft 6 and secures the arm 5
The above objects and advantages are accom
60 thereto, contact between the arm 5 and the fixed
element.
_
'
'
>
.
v2
arm a being maintained by the tension exerted
A typical signal generator attenuator circuit
' as a result of the deformation of the shaft end
is shown in Figure 4, with the radio frequency
of the arm 8 shown in the drawing.
' In the potentiometers ?nding wide present ap
source I9 connected to the potentiometer 28
through the resistor 2|. The ladder attenuator
plication, the rotatable arm'is generally straight
network and selector switch are connected to the
in form or, if not straight, is symmetrical so that
terminals 22 and 23 of the potentiometer. With
the net e?ect from the standpoint of magnetic
the potentiometer arm rotated to the maximum
clockwise position along the impedance element
of the potentiometer, viewing the potentiometer
linkage is the same as if a straight arm were
employed. Considering the potentiometer of Fig
ure 1 and visualizing a straight contact arm in 10 from the rear as shown in this ?gure, no input
use, it is seen that the circuit including the ?xed
. voltage is delivered to the input of the attenuator
arm 8 and the contact arm 5 would be electrically
network when using‘ a potentiometer of my de- ‘
linked to the impedance element by the magnetic ' sign, whereas there has always existed a residual
?eld linkage, and even with the arm in contact
voltage where attenuators of the previous design
' with the impedance element aperture 9, there will 15 were employed. ‘In the event that coupling exists
still be an output voltage developed between
?xed arm 8 and the connection to the aperture 8,
between the power circuit and the controlled cir
cuit external to the potentiometer, as indicated
the magnitude of this voltage being controlled by
by the arrow 25, the potentiometer may be de
the intensity of the current in element i, the fre
signed along the line which I have previously
quency of that current, and the area included 20 enumerated and this undesired‘voltage cancelled
between the ?xed arm 8 and the movable arm 5.
out when the potentiometer arm is in contact
By using an arm 5 having a bend of approxi
with one of the end ‘points of the impedance
mately the shape shown, the voltage appearing
element. This potentiometer is of great value in
between the ?xed arm 8 and the aperture 8 when
any application where it is desired tocontrol the
the arm 5 is in the position shown as a result of 25 intensity of a high frequency alternating current
the ?ux linking with the area I! is made to op
by the varying of the position of a contact, espe
pose and cancel the residual voltage introduced
cially where very small or zero output potential
by all other undesired coupling in the potentiom
is desired at a limiting position of the potenti
eter structure. That zero output is thus attained‘
ometer contact movement. The‘ circuit just de
is due to the fact that the net ?ux linkage be 80 scribed, however, has been included merely as a
tween the potentiometer element loop and the out
speci?c illustration of the application ofv this po
put loop is reduced to zero. To the ?ux linkages
tentiometer and it is not intended to limit the ap
normally existing, there are added, when the arm
plication of the invention to this particular class
5 is in engagement with one end of the element i,
of service. '
>
the ?ux linkages of reverse sense‘ occurring 85 It will be obvious that many changes and mod
through the area l2 enclosed by arm I and the
i?cations may be made in the invention without
?xed arm 8. The net ?ux from the current ?ow
departing from the spirit thereof as expressed in
ing in element A linking the controlled output
the foregoing description and in the appended
terminal circuit (arm 8 and terminal aperture 9)
claims.
is thus brought to zero. A bend in the contact 40 What I claim is:
arm 5 or ?xed arm 8 so reversely linking the ?ux
1. In a potentiometer, an impedance element,
from element I may therefore be conveniently
_a movable contact member engaging said element,
and accurately referred to as a de-gaussing bend,
and a current take-off member electrically con
and the relative con?guration of these two mem
nected with said contact member, said members
bers be referred to as a de-gaussing con?guration. 45 having a cooperating con?guration enclosing a
In cases where the potentiometer isto be em
de-gaussing area when said contact member is in
ployed in conjunction with a known circuit con
engagement with a predetermined end of said
?guration, the reverse couplingmaytbe adjusted
element.
‘
in the design to also balance out other undesired
2. In a potentiometer, an impedance element,
potentials induced in portions of the controlled 50 a movable contact member engaging said ele
circuit external to the structure of the potenti
ment, and a current take-oil’ member electrically
‘
connected with said contact member, one of said
As an alternative design, the arrangement of
members having a lateral bend intermediate its
Figure 3 shows a potentiometer securing the free
length de?ning with said other member a' de
dom from magnetic coupling between the imped 55 gaussing area when said movable contact mem
ance element and the controlledcircuit in a some
ber is in engagement with a predetermined end
what different manner. As before, an arm I1 is
of said impedance element.
secured to the rotatable shaft 8 by the collar
3. In a potentiometer, an impedance element, a
1, and the outer end of the arm ll moves over
movable contact member engaging said element,
the impedance element i which is secured to the 60 and a current take-oil member electrically‘ con
_ base 2 by the screws 3 passing through the mount
nected with and underlying said contact member,
ing ears 4. Connection to the impedance ele
said current take-off member having a bend in
ment is established by soldering wires in the aper
termediate its length de?ning with said movable
tures 9 and it. Contact to the movable arm is
contact member a de-gaussing area when said
afforded by the ?xed arm i 8, which is roughly 8 65 movable contact member is in engagement with
shaped in form. Arm i8 is dished in form of a
a predetermined end of said impedance element.
spring washer in the region of the shaft v8 ‘to pro
4. In a potentiometer, an impedance element
vide a contact in tension with arm i‘i. By virtue
occupying an arcuate sector of less than 360°,
of the form of the ?xed arm it, which has'also
means for making electrical connection to said
the shape of a de-gaussing bend an area i2 is 70 impedance element at a plurality of points, a
included between the movable and ?xed arms in
movable contact arm engaging said impedance
the minimum output position of the movable arm, ‘ element, and stationary current take-oi? means
whose sign of coupling is such as to oppose the
electrically connected with said contact arm and
residual coupling existing between'the impedance
having a terminal intermediate the extremitiesv
ometer proper.
element and the controlled circuit. _
75 or said impedance element, said contact arm and
"
2,388,534
said current take-off means having a cooperat
ing con?guration enclosing a de-gaussing area
when said contact arm is in engagement with a
predetermined end of 'said element.
5. In a potentiometer, an impedance element
of arcuate form occupying less than 360° of arc,
means for making electrical connection to said
impedance element at a plurality of points, a
3 i
therewith, a load impedance, means for connect
ing one terminal of said load impedance to one
of said end terminals of said impedance element,
a stationary current carrying member connected
to the other terminal of said load impedance, a
movable contact member displaceable over the
length of said impedance element connected to
said stationary current carrying member, the
contact arm rotatable in engagement with said
connections to said load impedance forming a sec
impedance element about an axis of rotation 10 ond loop circuit receiving energy from said ?rst
passing substantially through the center of our
vature of said arcuately formed impedance ele
ment, current take~oif member extending sub
loop circuit via space coupling addition to the
energy transferred through said contact member,
said stationary current carrying member and said
‘ stantially radially from said axis of rotation, said
movable current carrying member having a coop
contact arm being'provided with a bend in the 15 erating con?guration when said contact member
plane of rotation de?ning with said current take
is in engagement with one of said end terminals
’ o?‘ member a de-gaussing area when said moi?
forming a third loop circuit magnetically coupled
able. contact arm is inengagement with a pre
to said ?rst loop circuit with a sense opposing the
determined connection point to said impedance
coupling between said ?rst loop circuit and said
20 second loop circuit.
6. In an alternating current system, a source
10, In an alternating current system, a source
element.
,
‘
of periodic electrical energy, an impedance ele- _
ment connected across said source and forming a
_
of periodic electrical energy, an impedance ele
ment provided with two end terminals connected
loop circuit therewith, a load impedance, means
across said source and forming a loop circuit
adjustably and galvanically connecting said load
‘therewith, a load impedance, means for connect
impedance to said ?rst impedance element,
ing one terminal of said load impedance to one
whereby a second loop circuit is formed by said
of said end terminals of said impedance element,
load impedance and the connecting means as
a stationary current carrying member connected
sociated therewith, said second loop circuit in
to the other terminal of said load impedance, a
herently being magnetically coupled to said ?rst 30 movable contact member displaceable over the
‘loop circuit, and means for introducing magnetic
length of said impedance element connected to
coupling opposing said inherent coupling between
said stationary current carrying member, the
said ?rst 100p circuit and said second loop cir- ' ‘connections to said load impedance forming a
second loop circuit receiving energy ‘from said
7. In an alternating current. system, a source 35 ?rst loop circuit via space coupling in addition
of periodic electrical energy, an impedance ele
to_the energy transferred through said contact
ment connected across said source and forming a
member, said stationary ‘current carrying mem
loop circuit therewith, a load impedance, means
ber and said movable current carrying member
adjustably and galvanically connecting said load
having a cooperating con?guration when said
impedance to said ?rst impedance element, 40 contact member is in engagement with that end
whereby a second loop circuit is formed by said
terminal of said impedance element connected
load impedance and the connecting means as- to said load impedance forming a third loop cir
cuit magnetically coupled to said ?rst loop circuit 7
sociated therewith, said second loop circuit in
, herently being coupled to said ?rst loop circuit, I with a sense opposing the coupling between said
, and means for introducing magnetic coupling op 45 ?rst loop circuit and said second loop circuit. T
posing said inherent coupling between said ?rst
11. In an alternating current system, a source
7 loop circuit and said'second loop circuit with a
of periodic electrical energy, an impedance ele
magnitude developing a voltage equal to said in
ment provided with two end terminals connected
herent coupling when said adjustable means is
across said source and forming a loop circuit
in engagement with a predetermined point on’ 50 therewith, a load impedance, means for connect
said ?rst mentioned'impedance..
,
.
ing one terminal of said load impedance to one
8. In an alternating current system, a source
of said end- terminals of said impedance element,
of periodic electrical energy, an impedance ele
a stationary current carrying member connected
ment provided with two and terminals connected
to the other ‘terminal of said load impedance, a
across said source and forming a loop circuit 55 movable contact member displaceable over the
cuit.
.
therewith, a load impedance, means adJustably
and galvanically connecting said load impedance
to said ?rst impedance element, whereby a sec
ond loop circuit is formed by said load impedance
and the connecting means associated therewith,
said second loop circuit inherently being coupled
to said ?rst loop circuit, and means for introduc
length of said impedance element connected to
said stationary current carrying member, the
connections to said load impedance forming a
second'loop circuit receiving venergy-from said
?rst loop circuit via space coupling in addition.
to the energy transferred through said contact
member, said stationary current carrying mem
ing magnetic coupling opposing said inherent
ber and said movable current carrying member
coupling between said ?rst loop circuit and said
having a cooperating con?guration'when said
second loop circuit, with a magnitude developing 66 contact member is in engagement with that end
a voltage equal to said inherent coupling when
terminal of said impedance element connected to
said adjustable means is in engagement with a , said load impedance forming a third loop circuit
predetermined one of said end terminals.
magnetically coupled to said ?rst loop circuit with
9. In an alternating current system, a source
a sense opposing and equal to the coupling be
of periodic electrical energy, an impedance ele .70 tween said ?rst loop circuit and said second loop
ment provided with two end terminals connected
circuit.
.
across said source andiorming a loop circuit
RADFORD K. FRAZER.
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