<s>
Capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
"	O
are	O
non-contact	O
devices	O
capable	O
of	O
high-resolution	O
measurement	O
of	O
the	O
position	O
and/or	O
change	O
of	O
position	O
of	O
any	O
conductive	O
target	O
"	O
.	O
</s>
<s>
Capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
are	O
used	O
in	O
a	O
wide	O
variety	O
of	O
applications	O
including	O
semiconductor	O
processing	O
,	O
assembly	O
of	O
precision	O
equipment	O
such	O
as	O
disk	B-Device
drives	I-Device
,	O
precision	O
thickness	O
measurements	O
,	O
machine	O
tool	O
metrology	O
and	O
assembly	O
line	O
testing	O
.	O
</s>
<s>
A	O
capacitive	B-Device
sensing	I-Device
system	O
for	O
conductive	O
materials	O
uses	O
a	O
model	O
similar	O
to	O
the	O
one	O
described	O
above	O
,	O
but	O
in	O
place	O
of	O
one	O
of	O
the	O
conductive	O
plates	O
,	O
is	O
the	O
sensor	O
,	O
and	O
in	O
place	O
of	O
the	O
other	O
,	O
is	O
the	O
conductive	O
target	O
to	O
be	O
measured	O
.	O
</s>
<s>
Due	O
to	O
this	O
proportional	O
relationship	O
,	O
a	O
capacitive	B-Device
sensing	I-Device
system	O
is	O
able	O
to	O
measure	O
changes	O
in	O
capacitance	O
and	O
translate	O
these	O
changes	O
in	O
distance	O
measurements	O
.	O
</s>
<s>
One	O
of	O
the	O
more	O
common	O
applications	O
of	O
capacitive	B-Device
sensors	I-Device
is	O
for	O
precision	O
positioning	O
.	O
</s>
<s>
Capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
can	O
be	O
used	O
to	O
measure	O
the	O
position	O
of	O
objects	O
down	O
to	O
the	O
nanometer	O
level	O
.	O
</s>
<s>
This	O
type	O
of	O
precise	O
positioning	O
is	O
used	O
in	O
the	O
semiconductor	O
industry	O
where	O
silicon	B-Architecture
wafers	I-Architecture
need	O
to	O
be	O
positioned	O
for	O
exposure	O
.	O
</s>
<s>
Capacitive	B-Device
sensors	I-Device
are	O
also	O
used	O
to	O
pre-focus	O
the	O
electron	O
microscopes	O
used	O
in	O
testing	O
and	O
examining	O
the	O
wafers	B-Architecture
.	O
</s>
<s>
In	O
the	O
disc	B-Device
drive	I-Device
industry	O
,	O
capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
are	O
used	O
to	O
measure	O
the	O
runout	O
(	O
a	O
measure	O
of	O
how	O
much	O
the	O
axis	O
of	O
rotation	O
deviates	O
from	O
an	O
ideal	O
fixed	O
line	O
)	O
of	O
disc	B-Device
drive	I-Device
spindles	O
.	O
</s>
<s>
By	O
knowing	O
the	O
exact	O
runout	O
of	O
these	O
spindles	O
,	O
disc	B-Device
drive	I-Device
manufacturers	O
are	O
able	O
to	O
determine	O
the	O
maximum	O
amount	O
of	O
data	O
that	O
can	O
be	O
placed	O
onto	O
the	O
drives	O
.	O
</s>
<s>
Capacitive	B-Device
sensors	I-Device
are	O
also	O
used	O
to	O
ensure	O
that	O
disc	B-Device
drive	I-Device
platters	O
are	O
orthogonal	O
to	O
the	O
spindle	O
before	O
data	O
is	O
written	O
to	O
them	O
.	O
</s>
<s>
Capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
can	O
be	O
used	O
to	O
make	O
very	O
precise	O
thickness	O
measurements	O
.	O
</s>
<s>
Capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
operate	O
by	O
measuring	O
changes	O
in	O
position	O
.	O
</s>
<s>
This	O
error	O
can	O
be	O
eliminated	O
by	O
using	O
two	O
capacitive	B-Device
sensors	I-Device
to	O
measure	O
a	O
single	O
part	O
.	O
</s>
<s>
Capacitive	B-Device
sensors	I-Device
are	O
placed	O
on	O
either	O
side	O
of	O
the	O
part	O
to	O
be	O
measured	O
.	O
</s>
<s>
Capacitive	B-Device
sensors	I-Device
circuits	O
can	O
be	O
constructed	O
that	O
are	O
able	O
to	O
detect	O
changes	O
in	O
capacitance	O
on	O
the	O
order	O
of	O
a	O
10−5	O
picofarads	O
(	O
10	O
attofarads	O
)	O
.	O
</s>
<s>
While	O
capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
are	O
most	O
often	O
used	O
to	O
sense	O
changes	O
in	O
position	O
of	O
conductive	O
targets	O
,	O
they	O
can	O
also	O
be	O
used	O
to	O
sense	O
the	O
thickness	O
and/or	O
density	O
of	O
non-conductive	O
targets	O
as	O
well	O
.	O
</s>
<s>
Capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
are	O
often	O
used	O
in	O
metrology	O
applications	O
.	O
</s>
<s>
In	O
many	O
cases	O
,	O
the	O
sensors	O
are	O
used	O
to	O
analyze	O
and	O
optimize	O
the	O
rotation	O
of	O
spindles	O
in	O
various	O
machine	O
tools	O
,	O
examples	O
include	O
surface	O
grinders	O
,	O
lathes	B-Algorithm
,	O
milling	O
machines	O
,	O
and	O
air	O
bearing	O
spindles	O
.	O
</s>
<s>
Capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
are	O
often	O
used	O
in	O
assembly	O
line	O
testing	O
.	O
</s>
<s>
At	O
other	O
times	O
,	O
they	O
are	O
used	O
to	O
simply	O
look	O
for	O
the	O
presence	O
or	O
absence	O
of	O
a	O
certain	O
component	O
,	O
such	O
as	O
glue	B-Application
.	O
</s>
<s>
Using	O
capacitive	B-Device
sensors	I-Device
to	O
test	O
assembly	O
line	O
parts	O
can	O
help	O
to	O
prevent	O
quality	O
concerns	O
further	O
along	O
in	O
the	O
production	O
process	O
.	O
</s>
<s>
Capacitive	B-Algorithm
displacement	I-Algorithm
sensors	I-Algorithm
share	O
many	O
similarities	O
to	O
eddy	O
current	O
(	O
or	O
inductive	O
)	O
displacement	O
sensors	O
;	O
however	O
capacitive	B-Device
sensors	I-Device
use	O
an	O
electric	O
field	O
as	O
opposed	O
to	O
the	O
magnetic	O
field	O
used	O
by	O
eddy	O
current	O
sensors	O
This	O
leads	O
to	O
a	O
variety	O
of	O
differences	O
between	O
the	O
two	O
sensing	O
technologies	O
,	O
with	O
the	O
most	O
notable	O
differences	O
being	O
that	O
capacitive	B-Device
sensors	I-Device
are	O
generally	O
capable	O
of	O
higher	O
resolution	O
measurements	O
,	O
and	O
eddy	O
current	O
sensors	O
work	O
in	O
dirty	O
environments	O
while	O
capacitive	B-Device
sensors	I-Device
do	O
not	O
.	O
</s>
