<s>
A	O
potentiometer	B-Device
is	O
a	O
three-terminal	O
resistor	O
with	O
a	O
sliding	O
or	O
rotating	O
contact	O
that	O
forms	O
an	O
adjustable	O
voltage	O
divider	O
.	O
</s>
<s>
If	O
only	O
two	O
terminals	O
are	O
used	O
,	O
one	O
end	O
and	O
the	O
wiper	O
,	O
it	O
acts	O
as	O
a	O
variable	B-Device
resistor	I-Device
or	O
rheostat	O
.	O
</s>
<s>
The	O
measuring	O
instrument	O
called	O
a	O
potentiometer	B-Device
is	O
essentially	O
a	O
voltage	O
divider	O
used	O
for	O
measuring	O
electric	O
potential	O
(	O
voltage	O
)	O
;	O
the	O
component	O
is	O
an	O
implementation	O
of	O
the	O
same	O
principle	O
,	O
hence	O
its	O
name	O
.	O
</s>
<s>
Potentiometers	B-Device
are	O
commonly	O
used	O
to	O
control	O
electrical	O
devices	O
such	O
as	O
volume	B-Algorithm
controls	O
on	O
audio	O
equipment	O
.	O
</s>
<s>
Potentiometers	B-Device
operated	O
by	O
a	O
mechanism	O
can	O
be	O
used	O
as	O
position	O
transducers	B-Algorithm
,	O
for	O
example	O
,	O
in	O
a	O
joystick	B-Device
.	O
</s>
<s>
Potentiometers	B-Device
are	O
rarely	O
used	O
to	O
directly	O
control	O
significant	O
power	O
(	O
more	O
than	O
a	O
watt	O
)	O
,	O
since	O
the	O
power	O
dissipated	O
in	O
the	O
potentiometer	B-Device
would	O
be	O
comparable	O
to	O
the	O
power	O
in	O
the	O
controlled	O
load	O
.	O
</s>
<s>
Some	O
terms	O
in	O
the	O
electronics	O
industry	O
used	O
to	O
describe	O
certain	O
types	O
of	O
potentiometers	B-Device
are	O
:	O
</s>
<s>
Potentiometers	B-Device
consist	O
of	O
a	O
resistive	O
element	O
,	O
a	O
sliding	O
contact	O
(	O
wiper	O
)	O
that	O
moves	O
along	O
the	O
element	O
,	O
making	O
good	O
electrical	O
contact	O
with	O
one	O
part	O
of	O
it	O
,	O
electrical	O
terminals	O
at	O
each	O
end	O
of	O
the	O
element	O
,	O
a	O
mechanism	O
that	O
moves	O
the	O
wiper	O
from	O
one	O
end	O
to	O
the	O
other	O
,	O
and	O
a	O
housing	O
containing	O
the	O
element	O
and	O
wiper	O
.	O
</s>
<s>
Many	O
cheap	O
potentiometers	B-Device
are	O
constructed	O
with	O
a	O
resistive	O
element	O
(	O
B	O
in	O
cutaway	B-Application
drawing	I-Application
)	O
formed	O
into	O
an	O
arc	O
of	O
a	O
circle	O
usually	O
a	O
little	O
less	O
than	O
a	O
full	O
turn	O
and	O
a	O
wiper	O
(	O
C	O
)	O
sliding	O
on	O
this	O
element	O
when	O
rotated	O
,	O
making	O
electrical	O
contact	O
.	O
</s>
<s>
On	O
panel	O
potentiometers	B-Device
,	O
the	O
wiper	O
is	O
usually	O
the	O
center	O
terminal	O
of	O
three	O
.	O
</s>
<s>
For	O
single-turn	O
potentiometers	B-Device
,	O
this	O
wiper	O
typically	O
travels	O
just	O
under	O
one	O
revolution	O
around	O
the	O
contact	O
.	O
</s>
<s>
Another	O
type	O
is	O
the	O
linear	O
slider	O
potentiometer	B-Device
,	O
which	O
has	O
a	O
wiper	O
which	O
slides	O
along	O
a	O
linear	O
element	O
instead	O
of	O
rotating	O
.	O
</s>
<s>
An	O
advantage	O
of	O
the	O
slider	O
potentiometer	B-Device
is	O
that	O
the	O
slider	O
position	O
gives	O
a	O
visual	O
indication	O
of	O
its	O
setting	O
.	O
</s>
<s>
While	O
the	O
setting	O
of	O
a	O
rotary	B-Device
potentiometer	I-Device
can	O
be	O
seen	O
by	O
the	O
position	O
of	O
a	O
marking	O
on	O
the	O
knob	O
,	O
an	O
array	O
of	O
sliders	O
can	O
give	O
a	O
visual	O
impression	O
of	O
settings	O
as	O
in	O
a	O
graphic	O
equalizer	O
or	O
faders	O
on	O
a	O
mixing	O
console	O
.	O
</s>
<s>
The	O
resistive	O
element	O
of	O
cheap	O
potentiometers	B-Device
is	O
often	O
made	O
of	O
graphite	B-Application
.	O
</s>
<s>
Conductive	O
track	O
potentiometers	B-Device
use	O
conductive	O
polymer	O
resistor	O
pastes	O
that	O
contain	O
hard-wearing	O
resins	O
and	O
polymers	O
,	O
solvents	O
,	O
and	O
lubricant	O
,	O
in	O
addition	O
to	O
the	O
carbon	O
that	O
provides	O
the	O
conductive	O
properties	O
.	O
</s>
<s>
Multiturn	O
potentiometers	B-Device
are	O
also	O
operated	O
by	O
rotating	O
a	O
shaft	O
,	O
but	O
by	O
several	O
turns	O
rather	O
than	O
less	O
than	O
a	O
full	O
turn	O
.	O
</s>
<s>
Some	O
multiturn	O
potentiometers	B-Device
have	O
a	O
linear	O
resistive	O
element	O
with	O
a	O
sliding	O
contact	O
moved	O
by	O
a	O
lead	O
screw	O
;	O
others	O
have	O
a	O
helical	B-Application
resistive	O
element	O
and	O
a	O
wiper	O
that	O
turns	O
through	O
10	O
,	O
20	O
,	O
or	O
more	O
complete	O
revolutions	O
,	O
moving	O
along	O
the	O
helix	B-Application
as	O
it	O
rotates	O
.	O
</s>
<s>
Multiturn	O
potentiometers	B-Device
,	O
both	O
user-accessible	O
and	O
preset	O
,	O
allow	O
finer	O
adjustments	O
;	O
rotation	O
through	O
the	O
same	O
angle	O
changes	O
the	O
setting	O
by	O
typically	O
a	O
tenth	O
as	O
much	O
as	O
for	O
a	O
simple	O
rotary	B-Device
potentiometer	I-Device
.	O
</s>
<s>
A	O
string	O
potentiometer	B-Device
is	O
a	O
multi-turn	O
potentiometer	B-Device
operated	O
by	O
an	O
attached	O
reel	O
of	O
wire	O
turning	O
against	O
a	O
spring	O
,	O
allowing	O
it	O
to	O
convert	O
linear	O
position	O
to	O
a	O
variable	O
resistance	O
.	O
</s>
<s>
User-accessible	O
rotary	B-Device
potentiometers	I-Device
can	O
be	O
fitted	O
with	O
a	O
switch	O
which	O
operates	O
usually	O
at	O
the	O
anti-clockwise	O
extreme	O
of	O
rotation	O
.	O
</s>
<s>
Before	O
digital	O
electronics	O
became	O
the	O
norm	O
such	O
a	O
component	O
was	O
used	O
to	O
allow	O
radio	O
and	O
television	O
receivers	O
and	O
other	O
equipment	O
to	O
be	O
switched	O
on	O
at	O
minimum	O
volume	B-Algorithm
with	O
an	O
audible	O
click	O
,	O
then	O
the	O
volume	B-Algorithm
increased	O
,	O
by	O
turning	O
a	O
knob	O
.	O
</s>
<s>
Multiple	O
resistance	O
elements	O
can	O
be	O
ganged	O
together	O
with	O
their	O
sliding	O
contacts	O
on	O
the	O
same	O
shaft	O
,	O
for	O
example	O
,	O
in	O
stereo	O
audio	O
amplifiers	O
for	O
volume	B-Algorithm
control	O
.	O
</s>
<s>
In	O
other	O
applications	O
,	O
such	O
as	O
domestic	O
light	O
dimmers	O
,	O
the	O
normal	O
usage	O
pattern	O
is	O
best	O
satisfied	O
if	O
the	O
potentiometer	B-Device
remains	O
set	O
at	O
its	O
current	O
position	O
,	O
so	O
the	O
switch	O
is	O
operated	O
by	O
a	O
push	O
action	O
,	O
alternately	O
on	O
and	O
off	O
,	O
by	O
axial	O
presses	O
of	O
the	O
knob	O
.	O
</s>
<s>
They	O
are	O
usually	O
physically	O
much	O
smaller	O
than	O
user-accessible	O
potentiometers	B-Device
,	O
and	O
may	O
need	O
to	O
be	O
operated	O
by	O
a	O
screwdriver	O
rather	O
than	O
having	O
a	O
knob	O
.	O
</s>
<s>
They	O
are	O
usually	O
called	O
"	O
preset	O
potentiometers	B-Device
"	O
or	O
"trim[ming]	O
pots	O
"	O
.	O
</s>
<s>
Although	O
in	O
principle	O
any	O
taper	O
is	O
possible	O
,	O
two	O
types	O
are	O
widely	O
manufactured	O
:	O
linear	O
and	O
logarithmic	O
(	O
aka	O
"	O
audio	O
taper	O
"	O
)	O
potentiometers	B-Device
.	O
</s>
<s>
Potentiometers	B-Device
made	O
in	O
Asia	O
and	O
the	O
USA	O
are	O
usually	O
marked	O
with	O
an	O
"	O
A	O
"	O
for	O
logarithmic	O
taper	O
or	O
a	O
"	O
B	O
"	O
for	O
linear	O
taper	O
;	O
"	O
C	O
"	O
for	O
the	O
rarely	O
seen	O
reverse	O
logarithmic	O
taper	O
.	O
</s>
<s>
10%	O
log	O
taper	O
on	O
a	O
10kOhm	O
potentiometer	B-Device
would	O
yield	O
1kOhm	O
at	O
the	O
midpoint	O
.	O
</s>
<s>
A	O
linear	O
taper	O
potentiometer	B-Device
(	O
linear	O
describes	O
the	O
electrical	O
characteristic	O
of	O
the	O
device	O
,	O
not	O
the	O
geometry	O
of	O
the	O
resistive	O
element	O
)	O
has	O
a	O
resistive	O
element	O
of	O
constant	O
cross-section	O
,	O
resulting	O
in	O
a	O
device	O
where	O
the	O
resistance	O
between	O
the	O
contact	O
(	O
wiper	O
)	O
and	O
one	O
end	O
terminal	O
is	O
proportional	O
to	O
the	O
distance	O
between	O
them	O
.	O
</s>
<s>
Linear	O
taper	O
potentiometers	B-Device
are	O
used	O
when	O
the	O
division	O
ratio	O
of	O
the	O
potentiometer	B-Device
must	O
be	O
proportional	O
to	O
the	O
angle	O
of	O
shaft	O
rotation	O
(	O
or	O
slider	O
position	O
)	O
,	O
for	O
example	O
,	O
controls	O
used	O
for	O
adjusting	O
the	O
centering	O
of	O
the	O
display	O
on	O
an	O
analog	O
cathode-ray	O
oscilloscope	O
.	O
</s>
<s>
Precision	O
potentiometers	B-Device
have	O
an	O
accurate	O
relationship	O
between	O
resistance	O
and	O
slider	O
position	O
.	O
</s>
<s>
A	O
logarithmic	O
taper	O
potentiometer	B-Device
is	O
a	O
potentiometer	B-Device
that	O
has	O
a	O
bias	O
built	O
into	O
the	O
resistive	O
element	O
.	O
</s>
<s>
Basically	O
this	O
means	O
the	O
center	O
position	O
of	O
the	O
potentiometer	B-Device
is	O
not	O
one	O
half	O
of	O
the	O
total	O
value	O
of	O
the	O
potentiometer	B-Device
.	O
</s>
<s>
A	O
logarithmic	O
taper	O
potentiometer	B-Device
is	O
constructed	O
with	O
a	O
resistive	O
element	O
that	O
either	O
"	O
tapers	O
"	O
in	O
from	O
one	O
end	O
to	O
the	O
other	O
,	O
or	O
is	O
made	O
from	O
a	O
material	O
whose	O
resistivity	O
varies	O
from	O
one	O
end	O
to	O
the	O
other	O
.	O
</s>
<s>
Most	O
(	O
cheaper	O
)	O
"	O
log	O
"	O
potentiometers	B-Device
are	O
not	O
accurately	O
logarithmic	O
,	O
but	O
use	O
two	O
regions	O
of	O
different	O
resistance	O
(	O
but	O
constant	O
resistivity	O
)	O
to	O
approximate	O
a	O
logarithmic	O
law	O
.	O
</s>
<s>
The	O
two	O
resistive	O
tracks	O
overlap	O
at	O
approximately	O
50%	O
of	O
the	O
potentiometer	B-Device
rotation	O
;	O
this	O
gives	O
a	O
stepwise	O
logarithmic	O
taper	O
.	O
</s>
<s>
A	O
logarithmic	O
potentiometer	B-Device
can	O
also	O
be	O
simulated	O
(	O
not	O
very	O
accurately	O
)	O
with	O
a	O
linear	O
one	O
and	O
an	O
external	O
resistor	O
.	O
</s>
<s>
True	O
logarithmic	O
potentiometers	B-Device
are	O
significantly	O
more	O
expensive	O
.	O
</s>
<s>
Logarithmic	O
taper	O
potentiometers	B-Device
are	O
often	O
used	O
for	O
volume	B-Algorithm
or	O
signal	O
level	O
in	O
audio	O
systems	O
,	O
as	O
human	O
perception	O
of	O
audio	O
volume	B-Algorithm
is	O
logarithmic	O
,	O
according	O
to	O
the	O
Weber	O
–	O
Fechner	O
law	O
.	O
</s>
<s>
Unlike	O
mechanical	O
potentiometers	B-Device
,	O
non-contact	O
potentiometers	B-Device
use	O
an	O
optical	O
disk	O
to	O
trigger	O
an	O
infrared	O
sensor	O
,	O
or	O
a	O
magnet	O
to	O
trigger	O
a	O
magnetic	O
sensor	O
(	O
as	O
long	O
as	O
there	O
are	O
other	O
types	O
of	O
sensors	O
,	O
such	O
as	O
capacitive	O
,	O
other	O
types	O
of	O
non-contact	O
potentiometers	B-Device
can	O
probably	O
be	O
built	O
)	O
,	O
and	O
then	O
an	O
electronic	O
circuit	O
does	O
the	O
signal	O
processing	O
to	O
provide	O
an	O
output	O
signal	O
that	O
can	O
be	O
analogue	O
or	O
digital	O
.	O
</s>
<s>
An	O
example	O
of	O
a	O
non-contact	O
potentiometer	B-Device
can	O
be	O
found	O
with	O
the	O
integrated	O
circuit	O
.	O
</s>
<s>
The	O
word	O
rheostat	O
was	O
coined	O
about	O
1845	O
by	O
Sir	O
Charles	O
Wheatstone	O
,	O
from	O
the	O
Greek	O
rheos	O
meaning	O
"	O
stream	O
"	O
,	O
and	O
-	O
-states	O
(	O
from	O
histanai	O
,	O
"	O
to	O
set	O
,	O
to	O
cause	O
to	O
stand	O
"	O
)	O
meaning	O
"	O
setter	O
,	O
regulating	O
device	O
"	O
,	O
which	O
is	O
a	O
two-terminal	O
variable	B-Device
resistor	I-Device
.	O
</s>
<s>
For	O
low-power	O
applications	O
(	O
less	O
than	O
about	O
1	O
watt	O
)	O
a	O
three-terminal	O
potentiometer	B-Device
is	O
often	O
used	O
,	O
with	O
one	O
terminal	O
unconnected	O
or	O
connected	O
to	O
the	O
wiper	O
.	O
</s>
<s>
A	O
digital	O
potentiometer	B-Device
(	O
often	O
called	O
digipot	O
)	O
is	O
an	O
electronic	O
component	O
that	O
mimics	O
the	O
functions	O
of	O
analog	O
potentiometers	B-Device
.	O
</s>
<s>
Through	O
digital	O
input	O
signals	O
,	O
the	O
resistance	O
between	O
two	O
terminals	O
can	O
be	O
adjusted	O
,	O
just	O
as	O
in	O
an	O
analog	O
potentiometer	B-Device
.	O
</s>
<s>
There	O
are	O
two	O
main	O
functional	O
types	O
:	O
volatile	O
,	O
which	O
lose	O
their	O
set	O
position	O
if	O
power	O
is	O
removed	O
,	O
and	O
are	O
usually	O
designed	O
to	O
initialise	O
at	O
the	O
minimum	O
position	O
,	O
and	O
non-volatile	O
,	O
which	O
retain	O
their	O
set	O
position	O
using	O
a	O
storage	O
mechanism	O
similar	O
to	O
flash	B-Device
memory	I-Device
or	O
EEPROM	B-General_Concept
.	O
</s>
<s>
Usage	O
of	O
a	O
digipot	O
is	O
far	O
more	O
complex	O
than	O
that	O
of	O
a	O
simple	O
mechanical	O
potentiometer	B-Device
,	O
and	O
there	O
are	O
many	O
limitations	O
to	O
observe	O
;	O
nevertheless	O
they	O
are	O
widely	O
used	O
,	O
often	O
for	O
factory	O
adjustment	O
and	O
calibration	O
of	O
equipment	O
,	O
especially	O
where	O
the	O
limitations	O
of	O
mechanical	O
potentiometers	B-Device
are	O
problematic	O
.	O
</s>
<s>
In	O
equipment	O
which	O
has	O
a	O
microprocessor	B-Architecture
,	O
FPGA	B-Architecture
or	O
other	O
functional	O
logic	O
which	O
can	O
store	O
settings	O
and	O
reload	O
them	O
to	O
the	O
"	O
potentiometer	B-Device
"	O
every	O
time	O
the	O
equipment	O
is	O
powered	O
up	O
,	O
a	O
multiplying	O
DAC	O
can	O
be	O
used	O
in	O
place	O
of	O
a	O
digipot	O
,	O
and	O
this	O
can	O
offer	O
higher	O
setting	O
resolution	O
,	O
less	O
drift	O
with	O
temperature	O
,	O
and	O
more	O
operational	O
flexibility	O
.	O
</s>
<s>
A	O
membrane	O
potentiometer	B-Device
uses	O
a	O
conductive	O
membrane	O
that	O
is	O
deformed	O
by	O
a	O
sliding	O
element	O
to	O
contact	O
a	O
resistor	O
voltage	O
divider	O
.	O
</s>
<s>
The	O
service	O
life	O
of	O
these	O
types	O
of	O
potentiometers	B-Device
is	O
typically	O
1	O
million	O
to	O
20	O
million	O
cycles	O
depending	O
on	O
the	O
materials	O
used	O
during	O
manufacturing	O
and	O
the	O
actuation	O
method	O
;	O
contact	O
and	O
contactless	O
(	O
magnetic	O
)	O
methods	O
are	O
available	O
(	O
to	O
sense	O
position	O
)	O
.	O
</s>
<s>
Membrane	O
potentiometer	B-Device
manufacturers	O
offer	O
linear	O
,	O
rotary	O
,	O
and	O
application-specific	O
variations	O
.	O
</s>
<s>
Membrane	O
potentiometers	B-Device
can	O
be	O
used	O
for	O
position	O
sensing	O
.	O
</s>
<s>
For	O
touch-screen	O
devices	O
using	O
resistive	O
technology	O
,	O
a	O
two-dimensional	O
membrane	O
potentiometer	B-Device
provides	O
x	O
and	O
y	O
coordinates	O
.	O
</s>
<s>
Potentiometers	B-Device
are	O
rarely	O
used	O
to	O
directly	O
control	O
significant	O
amounts	O
of	O
power	O
(	O
more	O
than	O
a	O
watt	O
or	O
so	O
)	O
.	O
</s>
<s>
Instead	O
they	O
are	O
used	O
to	O
adjust	O
the	O
level	O
of	O
analog	O
signals	O
(	O
for	O
example	O
volume	B-Algorithm
controls	O
audio	O
equipment	O
)	O
,	O
and	O
as	O
control	O
inputs	O
for	O
electronic	O
circuits	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
light	O
dimmer	O
uses	O
a	O
potentiometer	B-Device
to	O
control	O
the	O
switching	O
of	O
a	O
TRIAC	O
and	O
so	O
indirectly	O
to	O
control	O
the	O
brightness	O
of	O
lamps	O
.	O
</s>
<s>
Preset	O
potentiometers	B-Device
are	O
widely	O
used	O
throughout	O
electronics	O
wherever	O
adjustments	O
must	O
be	O
made	O
during	O
manufacturing	O
or	O
servicing	O
.	O
</s>
<s>
User-actuated	O
potentiometers	B-Device
are	O
widely	O
used	O
as	O
user	O
controls	O
,	O
and	O
may	O
control	O
a	O
very	O
wide	O
variety	O
of	O
equipment	O
functions	O
.	O
</s>
<s>
The	O
widespread	O
use	O
of	O
potentiometers	B-Device
in	O
consumer	O
electronics	O
declined	O
in	O
the	O
1990s	O
,	O
with	O
rotary	B-Algorithm
incremental	I-Algorithm
encoders	I-Algorithm
,	O
up/down	O
push-buttons	O
,	O
and	O
other	O
digital	O
controls	O
now	O
more	O
common	O
.	O
</s>
<s>
However	O
they	O
remain	O
in	O
many	O
applications	O
,	O
such	O
as	O
volume	B-Algorithm
controls	O
and	O
as	O
position	O
sensors	O
.	O
</s>
<s>
Low-power	O
potentiometers	B-Device
,	O
both	O
slide	O
and	O
rotary	O
,	O
are	O
used	O
to	O
control	O
audio	O
equipment	O
,	O
changing	O
loudness	B-Algorithm
,	O
frequency	O
attenuation	O
,	O
and	O
other	O
characteristics	O
of	O
audio	O
signals	O
.	O
</s>
<s>
The	O
'	O
log	O
pot	O
 '	O
,	O
that	O
is	O
,	O
a	O
potentiometer	B-Device
has	O
a	O
resistance	O
,	O
taper	O
,	O
or	O
,	O
"	O
curve	O
"	O
(	O
or	O
law	O
)	O
of	O
a	O
logarithmic	O
(	O
log	O
)	O
form	O
,	O
is	O
used	O
as	O
the	O
volume	B-Algorithm
control	O
in	O
audio	O
power	O
amplifiers	O
,	O
where	O
it	O
is	O
also	O
called	O
an	O
"	O
audio	O
taper	O
pot	O
"	O
,	O
because	O
the	O
amplitude	B-Application
response	O
of	O
the	O
human	O
ear	O
is	O
approximately	O
logarithmic	O
.	O
</s>
<s>
It	O
ensures	O
that	O
on	O
a	O
volume	B-Algorithm
control	O
marked	O
0	O
to	O
10	O
,	O
for	O
example	O
,	O
a	O
setting	O
of	O
5	O
sounds	O
subjectively	O
half	O
as	O
loud	O
as	O
a	O
setting	O
of	O
10	O
.	O
</s>
<s>
There	O
is	O
also	O
an	O
anti-log	O
pot	O
or	O
reverse	O
audio	O
taper	O
which	O
is	O
simply	O
the	O
reverse	O
of	O
a	O
logarithmic	O
potentiometer	B-Device
.	O
</s>
<s>
It	O
is	O
almost	O
always	O
used	O
in	O
a	O
ganged	O
configuration	O
with	O
a	O
logarithmic	O
potentiometer	B-Device
,	O
for	O
instance	O
,	O
in	O
an	O
audio	O
balance	O
control	O
.	O
</s>
<s>
Potentiometers	B-Device
used	O
in	O
combination	O
with	O
filter	O
networks	O
act	O
as	O
tone	B-Algorithm
controls	I-Algorithm
or	O
equalizers	O
.	O
</s>
<s>
In	O
audio	O
systems	O
,	O
the	O
word	O
linear	O
,	O
is	O
sometimes	O
applied	O
in	O
a	O
confusing	O
way	O
to	O
describe	O
slide	O
potentiometers	B-Device
because	O
of	O
the	O
straight	O
line	O
nature	O
of	O
the	O
physical	O
sliding	O
motion	O
.	O
</s>
<s>
The	O
word	O
linear	O
when	O
applied	O
to	O
a	O
potentiometer	B-Device
regardless	O
of	O
being	O
a	O
slide	O
or	O
rotary	O
type	O
,	O
describes	O
a	O
linear	O
relationship	O
of	O
the	O
pot	O
's	O
position	O
versus	O
the	O
measured	O
value	O
of	O
the	O
pot	O
's	O
tap	O
(	O
wiper	O
or	O
electrical	O
output	O
)	O
pin	O
.	O
</s>
<s>
Potentiometers	B-Device
were	O
formerly	O
used	O
to	O
control	O
picture	O
brightness	O
,	O
contrast	O
,	O
and	O
color	O
response	O
.	O
</s>
<s>
A	O
potentiometer	B-Device
was	O
often	O
used	O
to	O
adjust	O
"	O
vertical	O
hold	O
"	O
,	O
which	O
affected	O
the	O
synchronization	O
between	O
the	O
receiver	O
's	O
internal	O
sweep	O
circuit	O
(	O
sometimes	O
a	O
multivibrator	O
)	O
and	O
the	O
received	O
picture	O
signal	O
,	O
along	O
with	O
other	O
things	O
such	O
as	O
audio-video	O
carrier	O
offset	O
,	O
tuning	O
frequency	O
(	O
for	O
push-button	O
sets	O
)	O
and	O
so	O
on	O
.	O
</s>
<s>
Potentiometers	B-Device
can	O
be	O
used	O
as	O
position	O
feedback	O
devices	O
in	O
order	O
to	O
create	O
closed-loop	O
control	O
,	O
such	O
as	O
in	O
a	O
servomechanism	O
.	O
</s>
<s>
Potentiometers	B-Device
are	O
also	O
very	O
widely	O
used	O
as	O
a	O
part	O
of	O
displacement	O
transducers	B-Algorithm
because	O
of	O
the	O
simplicity	O
of	O
construction	O
and	O
because	O
they	O
can	O
give	O
a	O
large	O
output	O
signal	O
.	O
</s>
<s>
In	O
analog	O
computers	O
,	O
high	O
precision	O
potentiometers	B-Device
are	O
used	O
to	O
scale	O
intermediate	O
results	O
by	O
desired	O
constant	O
factors	O
,	O
or	O
to	O
set	O
initial	B-Algorithm
conditions	I-Algorithm
for	O
a	O
calculation	O
.	O
</s>
<s>
A	O
motor-driven	O
potentiometer	B-Device
may	O
be	O
used	O
as	O
a	O
function	O
generator	O
,	O
using	O
a	O
non-linear	O
resistance	O
card	O
to	O
supply	O
approximations	O
to	O
trigonometric	O
functions	O
.	O
</s>
<s>
The	O
potentiometer	B-Device
can	O
be	O
used	O
as	O
a	O
voltage	O
divider	O
to	O
obtain	O
a	O
manually	O
adjustable	O
output	O
voltage	O
at	O
the	O
slider	O
(	O
wiper	O
)	O
from	O
a	O
fixed	O
input	O
voltage	O
applied	O
across	O
the	O
two	O
ends	O
of	O
the	O
potentiometer	B-Device
.	O
</s>
<s>
One	O
of	O
the	O
advantages	O
of	O
the	O
potential	O
divider	O
compared	O
to	O
a	O
variable	B-Device
resistor	I-Device
in	O
series	O
with	O
the	O
source	O
is	O
that	O
,	O
while	O
variable	B-Device
resistors	I-Device
have	O
a	O
maximum	O
resistance	O
where	O
some	O
current	O
will	O
always	O
flow	O
,	O
dividers	O
are	O
able	O
to	O
vary	O
the	O
output	O
voltage	O
from	O
maximum	O
(	O
)	O
to	O
ground	O
(	O
zero	O
volts	O
)	O
as	O
the	O
wiper	O
moves	O
from	O
one	O
end	O
of	O
the	O
potentiometer	B-Device
to	O
the	O
other	O
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
load	O
resistance	O
is	O
often	O
not	O
known	O
and	O
therefore	O
simply	O
placing	O
a	O
variable	B-Device
resistor	I-Device
in	O
series	O
with	O
the	O
load	O
could	O
have	O
a	O
negligible	O
effect	O
or	O
an	O
excessive	O
effect	O
,	O
depending	O
on	O
the	O
load	O
.	O
</s>
