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Resistance
Temperature Detectors
(RTD's)
*
Pl
num
Selection
Guide
Resistance
Ternperature Detector
IRTDI
Selection
Guide
-
/
Step
#1
- Select The
Ohms
Of
The
Element
When choosing
an
RTD
(Resistance
Temperature
Detector
or
Platinum
Resistance
Thermometer) for your application, you
will
first
need to
first
determine
the
ohms
of
resistance
for the
platinum element.
This
is
determined
by
the capability
of
your
temperature
indicating
instruments.
The Richards
RTD sensor is
available in
100
ohm,500
ohm, and
1000 ohm
configurations. The
ohm
value
is
the
base resistance
of
the
platinum element at
a
reference point of
0'C.
ln
typical
industrial applications
the
100 ohm
type
is
the
most
commonly
used
element and
is
the standard
in
this
catalog.
/
Step #2 - Select The
Alpha
RTD's have a temperature coefficient or "curve" of
either
.003920
ohms/ohm/'C or
.003850
ohms/ohm/'C.
This
value
is
commonly
called the alpha of the
sensor. The
.003920
or "American"
alpha is
the
U.S. industrial standard and the Japanese standard
(JlS
C1604-19S9).
The.003850 or "European"
alpha
is the
German (DlN 43760-1980), British
(BS
1904-1984), and
the
lnternational
Electrotechnical Commission (lEC 751-1983)
standard.
ln
typical
industrial applications the "European"
curve
is
more commonly used
than
the
"American"
curve and
is also
the
standard
alpha
in
this
catalog.
/
Step #3 - Select The
Accuracy
The accuracy
of
RTD
elements are frequently classified
using
the
DIN
43760 classification standard. This classification is
also
used
by
the lnternational
Electrotechnical
Commission
(lEC
751).
The classes are divided into four groups (A, B,
C,
D) by
the amount
of
allowable
resistance and
temperature
deviation over a
temperature
range.
These
base
values are
usually listed at
0"C' The
small-
er the deviation
the
lower
the class
(A) and the greater the accuracy of
the
sensor.
ln order
to
give our
customers
a high
quality
prod-
uct,
all standard
Richards RTD
sensors
perform
with
a
accuracy
greater
than
a class
A.
The standard Richards
RTD has a accuracy
of
c0.04olo
resistance
or
t0.1"C,
which is more accurate that the
DIN Class
A.
We also offer a very high accuracy version,
which
can be
specified
by
the
"AA"
(American Curve) or
"EE'
(European
Curve)
in
our part number. For comparison purposes,
the
Richards
and
DIN
accuracy classes
(at
0'C)
are shown
below.
Richards
Premium
AA
or
EE
=
t0.027" resistance or t0.05"C
Richards
Standard
A
or
E
=
=0,04o/o
resistance or
t0.1'C
DIN
Class A =
+0.0670
resistance or
t0,15'C
DIN
Class
B =
r0.1
2o/o
rasistance or
=0.3"C
/
Step
#4
- Select The Figure
Which Best
Represents The
Style
RTD
You Require
Browse
through our catalog and
locate
one
of
the
RTD photographs
which would
best
suite your
application.
Due
to space
limi-
tations,
if
you do
not
find
exactly
what you are
looking
for,
phone
one of
our
sales
engineers,
and we can
help with
the
part number.
/
Step
#5
-
Fine Tune
The
Part
Number
After locating
a
figure and
part number,
you can fine
tune
the
sensor for
your
application.
lf you
require an
American curve
sen-
sor and
not
the standard
European
curve, substitute the
"E"
with an "A"
in
the part
number.
lf you
require
a
500C1
and
not
the
stan-
dard
100Q sensor, substitute
the
"11" in
the
part number with a
"51".
1000Cl
sensors can
be
ordered
by changing
the
"11"
to
a "101".
Substitute any "X" and "Y" characters with
your
length
requirements.
RTD's
are
provided
in
four wire configurations as
standard. This
is
the
most
accurate configuration. Note
if
you are
using a transmitter
you
may be only able
to
use a
three wire
sensor.
This can
be
designated
by substituting
the
"4" in
the
part number
with a
"3".
Two
wire
RTD's
can
be
specified
by substituting
the
"4"
with
a
"2"
in
the part
number.
Note the RTD
wiring configuration
diagrams shown
in
this
catalog.
The standard
metal
sheath
for
RTD ele-
ments
is
1/4"
diameter made of 316 stainless
steel.
lnconel sheaths can be specified by changing the "16"
in
the part number to
a
"09".
Example Part
Number:
4E164-11-12-24 (Four
wire,
European curve,
31
6ss, 1/4" Dia.,100Q,
12"
probe, 24" probe and leads)
Note:
Richards
standard
RTD's have
a
maximum
service temperature
rating
of 400"C
(752'F).
Our
high
temperature
RTD's have a
maximum service
temperature
rating
of
650'C (1202"F).
lf you
would
like
to
specify
this
option,
add
a "H" after
the
curve designation
letter (A or
E) in
the catalog
number.
Example Part
Number:
4EH164-11'12-24
(High Temp., Four
wire,
European curve,
316ss,
1/4"
Dia.,100dt,12" probe,24"
probe and
leads).
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