<s>
A	O
rotary	B-Algorithm
encoder	I-Algorithm
,	O
also	O
called	O
a	O
shaft	B-Algorithm
encoder	I-Algorithm
,	O
is	O
an	O
electro-mechanical	O
device	O
that	O
converts	O
the	O
angular	O
position	O
or	O
motion	O
of	O
a	O
shaft	O
or	O
axle	O
to	O
analog	O
or	O
digital	O
output	O
signals	O
.	O
</s>
<s>
There	O
are	O
two	O
main	O
types	O
of	O
rotary	B-Algorithm
encoder	I-Algorithm
:	O
absolute	O
and	O
incremental	O
.	O
</s>
<s>
The	O
output	O
of	O
an	O
absolute	O
encoder	O
indicates	O
the	O
current	O
shaft	O
position	O
,	O
making	O
it	O
an	O
angle	B-Algorithm
transducer	I-Algorithm
.	O
</s>
<s>
The	O
output	O
of	O
an	O
incremental	B-Algorithm
encoder	I-Algorithm
provides	O
information	O
about	O
the	O
motion	O
of	O
the	O
shaft	O
,	O
which	O
typically	O
is	O
processed	O
elsewhere	O
into	O
information	O
such	O
as	O
position	O
,	O
speed	O
and	O
distance	O
.	O
</s>
<s>
Rotary	B-Algorithm
encoders	I-Algorithm
are	O
used	O
in	O
a	O
wide	O
range	O
of	O
applications	O
that	O
require	O
monitoring	O
or	O
control	O
,	O
or	O
both	O
,	O
of	O
mechanical	O
systems	O
,	O
including	O
industrial	O
controls	O
,	O
robotics	O
,	O
photographic	O
lenses	O
,	O
computer	O
input	O
devices	O
such	O
as	O
optomechanical	B-Device
mice	I-Device
and	O
trackballs	B-Device
,	O
controlled	O
stress	O
rheometers	O
,	O
and	O
rotating	O
radar	B-Application
platforms	O
.	O
</s>
<s>
Optical	B-Algorithm
encoders	I-Algorithm
are	O
very	O
sensitive	O
to	O
dust	O
.	O
</s>
<s>
Magnetic	O
encoders	O
operate	O
in	O
harsh	O
environments	O
where	O
optical	B-Algorithm
encoders	I-Algorithm
would	O
fail	O
to	O
work	O
.	O
</s>
<s>
A	O
multi-turn	O
absolute	O
rotary	B-Algorithm
encoder	I-Algorithm
includes	O
additional	O
code	O
wheels	O
and	O
toothed	O
wheels	O
.	O
</s>
<s>
An	O
incremental	B-Algorithm
encoder	I-Algorithm
will	O
immediately	O
report	O
changes	O
in	O
position	O
,	O
which	O
is	O
an	O
essential	O
capability	O
in	O
some	O
applications	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
the	O
mechanical	O
system	O
monitored	O
by	O
an	O
incremental	B-Algorithm
encoder	I-Algorithm
may	O
have	O
to	O
be	O
homed	O
(	O
moved	O
to	O
a	O
fixed	O
reference	O
point	O
)	O
to	O
initialize	O
absolute	O
position	O
measurements	O
.	O
</s>
<s>
The	O
optical	B-Algorithm
encoder	I-Algorithm
's	O
disc	O
is	O
made	O
of	O
glass	O
or	O
plastic	O
with	O
transparent	O
and	O
opaque	O
areas	O
.	O
</s>
<s>
The	O
Gray	B-Device
code	I-Device
is	O
often	O
used	O
.	O
</s>
<s>
This	O
code	O
can	O
be	O
read	O
by	O
a	O
controlling	O
device	O
,	O
such	O
as	O
a	O
microprocessor	B-Architecture
or	O
microcontroller	O
to	O
determine	O
the	O
angle	O
of	O
the	O
shaft	O
.	O
</s>
<s>
This	O
code	O
can	O
be	O
read	O
by	O
a	O
controlling	O
device	O
,	O
such	O
as	O
a	O
microprocessor	B-Architecture
or	O
microcontroller	O
to	O
determine	O
the	O
angle	O
of	O
the	O
shaft	O
,	O
similar	O
to	O
an	O
optical	B-Algorithm
encoder	I-Algorithm
.	O
</s>
<s>
Built-in	O
rotary	B-Algorithm
encoders	I-Algorithm
are	O
used	O
to	O
indicate	O
the	O
angle	O
of	O
the	O
motor	O
shaft	O
in	O
permanent	O
magnet	O
brushless	O
motors	O
,	O
which	O
are	O
commonly	O
used	O
on	O
CNC	O
machines	O
,	O
robots	B-Algorithm
,	O
and	O
other	O
industrial	O
equipment	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
the	O
encoder	O
were	O
used	O
in	O
a	O
robot	B-Algorithm
arm	O
,	O
the	O
controller	O
would	O
think	O
that	O
the	O
arm	O
was	O
in	O
the	O
wrong	O
position	O
,	O
and	O
try	O
to	O
correct	O
the	O
error	O
by	O
turning	O
it	O
through	O
180°	O
,	O
perhaps	O
causing	O
damage	O
to	O
the	O
arm	O
.	O
</s>
<s>
To	O
avoid	O
the	O
above	O
problem	O
,	O
Gray	B-Device
coding	I-Device
is	O
used	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
arrange	O
several	O
sensors	O
around	O
a	O
single	O
track	O
(	O
ring	O
)	O
so	O
that	O
consecutive	O
positions	O
differ	O
at	O
only	O
a	O
single	O
sensor	O
;	O
the	O
result	O
is	O
the	O
single-track	O
Gray	B-Device
code	I-Device
encoder	O
.	O
</s>
<s>
Depending	O
on	O
the	O
device	O
and	O
manufacturer	O
,	O
an	O
absolute	O
encoder	O
may	O
use	O
any	O
of	O
several	O
signal	O
types	O
and	O
communication	O
protocols	O
to	O
transmit	O
data	O
,	O
including	O
parallel	O
binary	O
,	O
analog	O
signals	O
(	O
current	O
or	O
voltage	O
)	O
,	O
and	O
serial	O
bus	O
systems	O
such	O
as	O
SSI	B-Protocol
,	O
BiSS	O
,	O
Heidenhain	O
EnDat	O
,	O
Sick-Stegmann	O
Hiperface	O
,	O
DeviceNet	O
,	O
Modbus	B-Protocol
,	O
Profibus	O
,	O
CANopen	O
and	O
EtherCAT	B-Protocol
,	O
which	O
typically	O
employ	O
Ethernet	O
or	O
RS-422/RS	O
-485	O
physical	O
layers	O
.	O
</s>
<s>
The	O
rotary	B-Algorithm
incremental	I-Algorithm
encoder	I-Algorithm
is	O
the	O
most	O
widely	O
used	O
of	O
all	O
rotary	B-Algorithm
encoders	I-Algorithm
due	O
to	O
its	O
ability	O
to	O
provide	O
real-time	O
position	O
information	O
.	O
</s>
<s>
The	O
measurement	O
resolution	O
of	O
an	O
incremental	B-Algorithm
encoder	I-Algorithm
is	O
not	O
limited	O
in	O
any	O
way	O
by	O
its	O
two	O
internal	O
,	O
incremental	O
movement	O
sensors	O
;	O
one	O
can	O
find	O
in	O
the	O
market	O
incremental	B-Algorithm
encoders	I-Algorithm
with	O
up	O
to	O
10,000	O
counts	O
per	O
revolution	O
,	O
or	O
more	O
.	O
</s>
<s>
Rotary	B-Algorithm
incremental	I-Algorithm
encoders	I-Algorithm
report	O
position	O
changes	O
without	O
being	O
prompted	O
to	O
do	O
so	O
,	O
and	O
they	O
convey	O
this	O
information	O
at	O
data	O
rates	O
which	O
are	O
orders	O
of	O
magnitude	O
faster	O
than	O
those	O
of	O
most	O
types	O
of	O
absolute	O
shaft	B-Algorithm
encoders	I-Algorithm
.	O
</s>
<s>
Because	O
of	O
this	O
,	O
incremental	B-Algorithm
encoders	I-Algorithm
are	O
commonly	O
used	O
in	O
applications	O
that	O
require	O
precise	O
measurement	O
of	O
position	O
and	O
velocity	O
.	O
</s>
<s>
A	O
rotary	B-Algorithm
incremental	I-Algorithm
encoder	I-Algorithm
may	O
use	O
mechanical	O
,	O
optical	O
or	O
magnetic	O
sensors	O
to	O
detect	O
rotational	O
position	O
changes	O
.	O
</s>
<s>
The	O
mechanical	O
type	O
is	O
commonly	O
employed	O
as	O
a	O
manually	O
operated	O
"	O
digital	O
potentiometer	B-Device
"	O
control	O
on	O
electronic	O
equipment	O
.	O
</s>
<s>
For	O
example	O
,	O
modern	O
home	O
and	O
car	O
stereos	O
typically	O
use	O
mechanical	O
rotary	B-Algorithm
encoders	I-Algorithm
as	O
volume	O
controls	O
.	O
</s>
<s>
A	O
rotary	B-Algorithm
incremental	I-Algorithm
encoder	I-Algorithm
has	O
two	O
output	O
signals	O
,	O
A	O
and	O
B	O
,	O
which	O
issue	O
a	O
periodic	O
digital	O
waveform	O
in	O
quadrature	O
when	O
the	O
encoder	O
shaft	O
rotates	O
.	O
</s>
<s>
This	O
is	O
similar	O
to	O
sine	O
encoders	O
,	O
which	O
output	O
sinusoidal	O
waveforms	O
in	O
quadrature	O
(	O
i.e.	O
,	O
sine	O
and	O
cosine	O
)	O
,	O
thus	O
combining	O
the	O
characteristics	O
of	O
an	O
encoder	O
and	O
a	O
resolver	B-Algorithm
.	O
</s>
<s>
Some	O
rotary	B-Algorithm
incremental	I-Algorithm
encoders	I-Algorithm
have	O
an	O
additional	O
"	O
index	O
"	O
output	O
(	O
typically	O
labeled	O
Z	O
)	O
,	O
which	O
emits	O
a	O
pulse	O
when	O
the	O
shaft	O
passes	O
through	O
a	O
particular	O
angle	O
.	O
</s>
<s>
This	O
is	O
commonly	O
used	O
in	O
radar	B-Application
systems	I-Application
and	O
other	O
applications	O
that	O
require	O
a	O
registration	O
signal	O
when	O
the	O
encoder	O
shaft	O
is	O
located	O
at	O
a	O
particular	O
reference	O
angle	O
.	O
</s>
<s>
Unlike	O
absolute	O
encoders	O
,	O
an	O
incremental	B-Algorithm
encoder	I-Algorithm
does	O
not	O
keep	O
track	O
of	O
,	O
nor	O
do	O
its	O
outputs	O
indicate	O
the	O
absolute	O
position	O
of	O
the	O
mechanical	O
system	O
to	O
which	O
it	O
is	O
attached	O
.	O
</s>
<s>
Consequently	O
,	O
to	O
determine	O
the	O
absolute	O
position	O
at	O
any	O
particular	O
moment	O
,	O
it	O
is	O
necessary	O
to	O
"	O
track	O
"	O
the	O
absolute	O
position	O
with	O
an	O
incremental	B-Algorithm
encoder	I-Algorithm
interface	O
which	O
typically	O
includes	O
a	O
bidirectional	O
electronic	O
counter	O
.	O
</s>
<s>
Inexpensive	O
incremental	B-Algorithm
encoders	I-Algorithm
are	O
used	O
in	O
mechanical	O
computer	B-Device
mice	I-Device
.	O
</s>
<s>
Rotary	B-Algorithm
encoders	I-Algorithm
with	O
a	O
single	O
output	O
(	O
i.e.	O
</s>
<s>
tachometers	B-Device
)	O
cannot	O
be	O
used	O
to	O
sense	O
direction	O
of	O
motion	O
but	O
are	O
suitable	O
for	O
measuring	O
speed	O
and	O
for	O
measuring	O
position	O
when	O
the	O
direction	O
of	O
travel	O
is	O
constant	O
.	O
</s>
