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Lead Contents

Types and Characteristics of Temperature Sensors for Controllers

FAQ No. FAQ00666

Primary Contents

Question

What are the types and characteristics of temperature sensors for Controllers?

Answer

Refer to the following table.

TypePrinciple and
characteristics
AdvantagesDisadvantagesElement
type
Class
Platinum
resis-
tance
thermom-
eter
The electrical
resistance of the
metal used by
platinum resistance
thermometers has
a fixed relationship
to the temperature.
Therefore, a
platinum wire with
extremely high purity
is used for the
resistor.
High
precision
Expensive
Easily
influenced by
lead wire
resistance
(OMRON
minimizes
influence by
using a
3-conductor
system.)
Slow thermal
response
Low resistance
to shock and
vibration
JPt100
Pt100
JIS Standard
ClassTolerance
Class A± (0.15+0.002 | t |) °C
Class B± (0.3+0.005 | t |) °C
Note:
| t | represents the absolute value
of the temperature range.
Thermo-
couple
Thermocouple
temperature sensors
are constructed
using two dissimilar
metals that are
joined together. The
junctions are called
the measuring junction
and the reference
junction (output
terminal side). A
thermoelectromotive
force is generated
between the junctions
with a fixed correlation
to the temperature
providing the difference
in temperature.
Therefore, the
temperature at the
measuring junction
can be determined
from the
thermoelectromotive
force when a fixed
temperature is
maintained at the
reference junction.
Thermocouple
temperature sensors
are capable of
measuring the
highest temperatures
among contact
temperature sensors
by using this
measurement method.
Broad
temperature
range

High-
temperature
measurement

High
resistance to
shock and
vibration

Fast thermal
response
Compensating
conductors are
required when
extending the
lead wires
K (CA)
J (IC)
R (PR)
JIS Standard for Thermocouples
Material
code
Model
name
Tempe-
rature
range
ClassTolerance
(See
note.)
RPR0°C to
1,600°C
Class
2
(0.25)
±1.5°C or
±0.25% of
measured
temperature
KCA0°C to
1,200°C
Class
2
(0.75)
±2.5°C or
±0.75% of
measured
temperature
JIC0°C to
750°C
Class
2
(0.75)
±2.5°C or
±0.75% of
measured
temperature
Note:
The tolerance is either the value
in °C or %, whichever is larger.
Ther-
mistor
Temperature
Characteristics
Fast thermal
response

Small error
due to lead
wire
resistance
Limited
temperature
range
Low resistance
to shock
ThermistorJIS Standard Class 1
Measured
temperature
Tolerance
-50 to 100°C±1°C max.
100 to 350°C±1% max. of measured
temperature