<s>
The	O
linear	B-Algorithm
variable	I-Algorithm
differential	I-Algorithm
transformer	I-Algorithm
(	O
LVDT	B-Algorithm
)	O
(	O
also	O
called	O
linear	B-Algorithm
variable	I-Algorithm
displacement	I-Algorithm
transformer	I-Algorithm
,	O
linear	B-Algorithm
variable	I-Algorithm
displacement	I-Algorithm
transducer	I-Algorithm
,	O
or	O
simply	O
differential	O
transformer	B-Algorithm
)	O
is	O
a	O
type	O
of	O
electrical	O
transformer	B-Algorithm
used	O
for	O
measuring	O
linear	O
displacement	O
(	O
position	O
)	O
.	O
</s>
<s>
A	O
counterpart	O
to	O
this	O
device	O
that	O
is	O
used	O
for	O
measuring	O
rotary	O
displacement	O
is	O
called	O
a	O
rotary	B-Algorithm
variable	I-Algorithm
differential	I-Algorithm
transformer	I-Algorithm
(	O
RVDT	B-Algorithm
)	O
.	O
</s>
<s>
LVDTs	B-Algorithm
are	O
robust	O
,	O
absolute	O
linear	O
position/displacement	O
transducers	O
;	O
inherently	O
frictionless	O
,	O
they	O
have	O
a	O
virtually	O
infinite	O
cycle	O
life	O
when	O
properly	O
used	O
.	O
</s>
<s>
As	O
AC	O
operated	O
LVDTs	B-Algorithm
do	O
not	O
contain	O
any	O
electronics	O
,	O
they	O
can	O
be	O
designed	O
to	O
operate	O
at	O
cryogenic	O
temperatures	O
or	O
up	O
to	O
1200°F	O
(	O
650°C	O
)	O
,	O
in	O
harsh	O
environments	O
,	O
and	O
under	O
high	O
vibration	O
and	O
shock	O
levels	O
.	O
</s>
<s>
LVDTs	B-Algorithm
have	O
been	O
widely	O
used	O
in	O
applications	O
such	O
as	O
power	O
turbines	O
,	O
hydraulics	O
,	O
automation	O
,	O
aircraft	O
,	O
satellites	O
,	O
nuclear	O
reactors	O
,	O
and	O
many	O
others	O
.	O
</s>
<s>
The	O
LVDT	B-Algorithm
converts	O
a	O
position	O
or	O
linear	O
displacement	O
from	O
a	O
mechanical	O
reference	O
(	O
zero	O
or	O
null	O
position	O
)	O
into	O
a	O
proportional	O
electrical	O
signal	O
containing	O
phase	O
(	O
for	O
direction	O
)	O
and	O
amplitude	O
(	O
for	O
distance	O
)	O
information	O
.	O
</s>
<s>
The	O
LVDT	B-Algorithm
operation	O
does	O
not	O
require	O
an	O
electrical	O
contact	O
between	O
the	O
moving	O
part	O
(	O
probe	O
or	O
core	O
assembly	O
)	O
and	O
the	O
coil	O
assembly	O
,	O
but	O
instead	O
relies	O
on	O
electromagnetic	O
coupling	O
.	O
</s>
<s>
The	O
linear	B-Algorithm
variable	I-Algorithm
differential	I-Algorithm
transformer	I-Algorithm
has	O
three	O
solenoidal	O
coils	O
placed	O
end-to-end	O
around	O
a	O
tube	O
.	O
</s>
<s>
Modern	O
systems	O
,	O
particularly	O
those	O
involving	O
safety	O
,	O
require	O
fault	O
detection	O
of	O
the	O
LVDT	B-Algorithm
,	O
and	O
the	O
normal	O
method	O
is	O
to	O
demodulate	O
each	O
secondary	O
separately	O
,	O
using	O
precision	O
half	O
wave	O
or	O
full	O
wave	O
rectifiers	O
,	O
based	O
on	O
op-amps	O
,	O
and	O
compute	O
the	O
difference	O
by	O
subtracting	O
the	O
DC	O
signals	O
.	O
</s>
<s>
Because	O
,	O
for	O
constant	O
excitation	O
voltage	O
,	O
the	O
sum	O
of	O
the	O
two	O
secondary	O
voltages	O
is	O
almost	O
constant	O
throughout	O
the	O
operating	O
stroke	O
of	O
the	O
LVDT	B-Algorithm
,	O
its	O
value	O
remains	O
within	O
a	O
small	O
window	O
and	O
can	O
be	O
monitored	O
such	O
that	O
any	O
internal	O
failures	O
of	O
the	O
LVDT	B-Algorithm
will	O
cause	O
the	O
sum	O
voltage	O
to	O
deviate	O
from	O
its	O
limits	O
and	O
be	O
rapidly	O
detected	O
,	O
causing	O
a	O
fault	O
to	O
be	O
indicated	O
.	O
</s>
<s>
Where	O
digital	O
processing	O
in	O
the	O
form	O
of	O
a	O
microprocessor	B-Architecture
or	O
FPGA	B-Architecture
is	O
available	O
in	O
the	O
system	O
,	O
it	O
is	O
customary	O
for	O
the	O
processing	O
device	O
to	O
carry	O
out	O
the	O
fault	O
detection	O
,	O
and	O
possibly	O
ratiometric	O
processing	O
to	O
improve	O
accuracy	O
,	O
by	O
dividing	O
the	O
difference	O
in	O
secondary	O
voltages	O
by	O
the	O
sum	O
of	O
the	O
secondary	O
voltages	O
,	O
to	O
make	O
the	O
measurement	O
independent	O
of	O
the	O
exact	O
amplitude	O
of	O
the	O
excitation	O
signal	O
.	O
</s>
<s>
The	O
LVDT	B-Algorithm
is	O
designed	O
with	O
long	O
slender	O
coils	O
to	O
make	O
the	O
output	O
voltage	O
essentially	O
linear	O
over	O
displacement	O
up	O
to	O
several	O
inches	O
(	O
several	O
hundred	O
millimetres	O
)	O
long	O
.	O
</s>
<s>
The	O
LVDT	B-Algorithm
can	O
be	O
used	O
as	O
an	O
absolute	O
position	O
sensor	O
.	O
</s>
<s>
Even	O
if	O
the	O
power	O
is	O
switched	O
off	O
,	O
on	O
restarting	O
it	O
,	O
the	O
LVDT	B-Algorithm
shows	O
the	O
same	O
measurement	O
,	O
and	O
no	O
positional	O
information	O
is	O
lost	O
.	O
</s>
<s>
Because	O
the	O
sliding	O
core	O
does	O
not	O
touch	O
the	O
inside	O
of	O
the	O
tube	O
,	O
it	O
can	O
move	O
without	O
friction	O
,	O
making	O
the	O
LVDT	B-Algorithm
a	O
highly	O
reliable	O
device	O
.	O
</s>
<s>
The	O
absence	O
of	O
any	O
sliding	O
or	O
rotating	O
contacts	O
allows	O
the	O
LVDT	B-Algorithm
to	O
be	O
completely	O
sealed	O
against	O
the	O
environment	O
.	O
</s>
<s>
LVDTs	B-Algorithm
are	O
commonly	O
used	O
for	O
position	O
feedback	O
in	O
servomechanisms	O
,	O
and	O
for	O
automated	O
measurement	O
in	O
machine	O
tools	O
and	O
many	O
other	O
industrial	O
and	O
scientific	O
applications	O
.	O
</s>
